PCT Test Purpose and Application (1)
PCT test is generally known as pressure cooker cooking test or saturated steam test, the most important is to test the product to be tested under harsh temperature, saturated humidity (100%R.H.)[saturated water vapor] and pressure environment, test the high humidity resistance of the test product, for printed circuit board (PCB&FPC), used to carry out material moisture absorption test, high pressure cooking test... For the purpose of the test, if the product to be tested is a semiconductor, it is used to test the moisture resistance of the semiconductor package. The product to be tested is placed in a harsh temperature, humidity and pressure environment. If the semiconductor package is not good, moisture will penetrate into the package along the colloid or the interface between the colloid and the conductor frame. Popcorn effect, open circuit caused by corrosion of dynamic metallized area, short circuit caused by contamination between package pins... And other related issues.
Pressure Digester test (PCT) Structure:
The test chamber consists of a pressure vessel, including a water heater that can produce a 100% (wetting) environment. The different failures of the product to be tested after PCT test may be caused by a large amount of water vapor condensation and penetration.
Bathtub curve:
Bathtub curve (Bathtub curve, failure period), also known as bathtub curve, smile curve, mainly shows the failure rate of the product in different periods, mainly including early death period (early failure period), normal period (random failure period), wear period (degradation failure period), according to the reliability test box of environmental test. It can be divided into screening test, accelerated life test (durability test) and failure rate test. "Test design", "test execution" and "test analysis" should be considered as a whole when conducting reliability tests.
Common failure periods:
Early failure (early death, Infant Mortality Region) : imperfect production, defective materials, unsuitable environment, imperfect design. Random failure period (normal period, Useful Life Region) : external shock, misuse, changes in environmental conditions fluctuations, poor compression performance. Degradation failure period (Wearout Region) : oxidation, fatigue aging, performance degradation, corrosion.
Environmental stress and failure diagram description:
According to the statistical report of Hughes Airlines, the proportion of environmental stress caused by electronic products failure, height accounted for 2%, salt spray accounted for 4%, dust accounted for 6%, vibration accounted for 28%, and temperature and humidity accounted for up to 60%, so the impact of electronic products on temperature and humidity is particularly significant, but due to the traditional high temperature and humidity tests (such as: 40℃/90%R.H., 85℃/85%R.H., 60℃/95%R.H.) takes a long time, in order to speed up the material's hypersonic rate and shorten the test time, accelerated test equipment (HAST[High accelerated life testing machine], PCT[pressure pot]) can be used to carry out relevant tests. It is also called (degenerate failure period, wear period) test.
Service conditions for high, low temperature, and low pressure test chambers
One of the usage conditions for high, low temperature, and low pressure test chambers: environmental conditions
a、 Temperature: 15 ℃~35 ℃;
b、 Relative humidity: not exceeding 85%;
c、 Atmospheric pressure: 80kPa~106kPa
d、 There is no strong vibration or corrosive gas in the surrounding area;
e、 No direct sunlight exposure or direct radiation from other cold or heat sources;
f、 There is no strong airflow around, and when the surrounding air needs to be forced to flow, the airflow should not be directly blown onto the box;
g、 The influence of magnetic field on the control circuit of the interference free test box in the surrounding area;
h、 There is no high concentration of dust or corrosive substances in the surrounding area.
Condition 2 for the use of high, low temperature, and low pressure test chambers: Power supply conditions
a、 AC voltage: 220V ± 22V or 380V ± 38V;
b、 Frequency: 50HZ ± 0.5HZ
Condition Three for the Use of High, Low Temperature, and Low Pressure Test Chambers: Water Supply Conditions
It is advisable to use tap water or circulating water that meets the following conditions:
a、 Water temperature: not higher than 30 ℃;
b、 Water pressure: 0.1MPa~0.3MPa;
c、 Water quality: meets industrial water standards.
Condition 4 for the use of high, low temperature, and low pressure test chambers: Test load conditions
The load of the test chamber should meet the following conditions every week:
a、 The total mass of the load shall not exceed 80KG per cubic meter within the working chamber volume
b、 The total volume of the load shall not exceed 5/1 of the working chamber volume
c、 On any cross-section perpendicular to the prevailing wind direction, the sum of the load areas should not exceed 3/1 of the cross-sectional area of the working chamber at that location, and the load should not obstruct the flow of airflow when placed.
Dear customer:
Our company has products such as rapid temperature change test chambers, UV accelerated weather resistance testing machines, and temperature and humidity control chambers. You can call our service hotline through our website to learn more about our products. Our pursuit is endless, and we welcome new and old customers to choose their favorite products with confidence. We will be dedicated to serving you!
Precision Oven Manual
Precision ovens are suitable for semiconductor devices in the electronic industry, curing and aging of electronic components, high-temperature precision testing of plastic and rubber, molding processes for telephone handle wires, as well as experimental or workshop production lines in higher education research institutions and industrial and mining enterprises that require high product temperatures.
This instrument is equipped with a two-level temperature control system, dual protection, automatic cut-off for overheating, safe and reliable. The column alarm device has a temperature rise and constant temperature light display. When using this instrument in large quantities in the production workshop, which instrument has reached the constant temperature requirement and which one is still in the heating state can be clearly seen.
The instrument liner is made of high-quality mirror stainless steel, the outer shell is sprayed with plastic, and a safety door lock is installed. The front door adopts a high-temperature resistant glass observation window, which can observe the condition of the test piece inside the box at any time.
Dear customer:
Our company has products such as rapid temperature change test chambers, UV accelerated weather resistance testing machines, and temperature and humidity control chambers. You can call our service hotline through our website to learn more about our products. Our pursuit is endless, and we welcome new and old customers to choose their favorite products with confidence. We will be dedicated to serving you!
PCT Test Purpose and Application (2)
θ 10℃ rule:
When discussing product life, the expression of [θ10℃ rule] is generally used, and a simple explanation can be expressed as [10℃ rule], when the ambient temperature rises by 10℃, the product life will be reduced by half; When the ambient temperature rises by 20 ° C, the product life will be reduced to a quarter. This rule can explain how the temperature affects the life of the product (failure), the opposite product reliability test, can also be used to increase the ambient temperature to accelerate the failure phenomenon, a variety of accelerated life aging tests.
Causes of failure caused by moisture:
Water vapor infiltration, polymer material depolymerization, reduced polymer bonding ability, corrosion, cavitation, wire solder joint detachment, leakage between leads, wafer and wafer bonding layer detachment, pad corrosion, metallization, or short circuit between leads. Effect of water vapor on the reliability of electronic packaging: corrosion failure, delamination and cracking, changing the properties of plastic sealing materials.
PCT failure mode for PCB:
Blister, Crack, SR de-lamination.
PCT testing of semiconductors:
PCT is mainly to test the moisture resistance of semiconductor packaging, the product to be tested is placed in a harsh temperature and humidity and pressure environment test, if the semiconductor packaging is not good, moisture will penetrate into the package along the colloidal or colloidal and wire frame interface into the package, common reasons for installation: Popcorn effect, open circuit caused by corrosion of dynamic metallized area, short circuit caused by contamination between package pins... And other related issues.
PCT reliability assessment for IC semiconductors:
DA Epoxy, wire frame material, sealing resin corrosion failure and IC: corrosion failure (water vapor, bias, impurity ions) will cause electrochemical corrosion of IC aluminum wire, resulting in open circuit and migration growth of aluminum wire.
Failure phenomena caused by moisture corrosion of plastic-sealed semiconductors:
Because aluminum and aluminum alloys are cheap and simple to process, they are usually used as metal wires for integrated circuits. From the beginning of the integrated circuit molding process, water and gas will penetrate through epoxy resin to cause corrosion of aluminum metal wires and thus open circuit phenomenon, which becomes the most headache for quality management. Although various efforts have been made to improve product quality through various improvements, including the use of different epoxy resin materials, improved plastic sealing technology and the improvement of inactive plastic sealing film, with the rapid development of miniaturization of semiconductor electronic devices, the corrosion problem of plastic sealed aluminum metal wire is still a very important technical topic in the electronics industry.
Corrosion process in aluminum wire:
① Water permeates into the plastic sealing shell → moisture permeates into the gap between the resin and the wire
② Water permeates the surface of the wafer to cause aluminum chemical reaction
Factors that accelerate aluminum corrosion:
① The connection between the resin material and the wafer frame interface is not good enough (due to the difference in expansion rate between various materials)
② When packaging, the packaging material is contaminated with impurities or impurity ions (due to the appearance of impurity ions)
③ The high concentration of phosphorus used in the inactive plastic encapsulation film
(4) Defects in inactive plastic encapsulation film
The Popcorn Effect:
The original refers to the IC encapsulated in the plastic outer body, because the silver paste used in the wafer installation will absorb water, once the plastic body is sealed without prevention, when the downstream assembly and welding encounter high temperature, the water will burst due to the vaporization pressure, and it will also emit a sound like popcorn, so it is named, when the absorbed water vapor content is higher than 0.17%, The [popcorn] phenomenon will occur. Recently, P-BGA packaging components are very popular, not only the silver glue will absorb water, but also the substrate of the serial board will absorb water, and the popcorn phenomenon often occurs when the management is not good.
A Brief Analysis of the Five Characteristics of Walk in Laboratories
The walk-in laboratory has been upgraded on the basis of the original walk-in laboratory, with the characteristics of large testing space and operators being able to operate the test products in the laboratory, providing conditions for temperature and humidity environment testing for industrial manufacturers' batch or large parts, semi-finished products, and finished products. Adopting advanced Chinese LCD display screen touch screen, various complex program settings can be carried out. The program settings adopt dialogue mode, and the operation is simple and fast. It can achieve automatic operation of the refrigeration machine, maximizing automation, and can be equipped with LAN communication interfaces for users to remotely process and centrally control. It can record temperature and temperature parameters for 90 days, and is equipped with a paperless recorder.
5 characteristics of walk-in laboratory
1. Having an extremely wide temperature and humidity control range, it can meet various needs of users. By adopting a unique balanced temperature and humidity control method, a safe and precise temperature and humidity environment can be achieved. Having stable and balanced heating and humidification performance, it can achieve high-precision and highly stable temperature and humidity control.
2. Equipped with high-precision intelligent temperature regulators, temperature and humidity are displayed using LED digital display. Optional temperature and humidity recorder.
3. The refrigeration circuit is automatically selected, and the automatic control device has the performance of automatically selecting and operating the refrigeration circuit according to the set value of temperature, achieving direct start of the refrigeration machine and direct cooling under high temperature conditions.
4. The inner door is equipped with a large observation window, which facilitates the observation of the experimental status of the test samples.
5. Equipped with advanced safety and protection devices - residual current circuit breaker, over temperature protector, phase loss protector, and water cut-off protector.
Dear customer:
Our company has products such as rapid temperature change test chambers, UV accelerated weather resistance testing machines, and temperature and humidity control chambers. You can call our service hotline through our website to learn more about our products. Our pursuit is endless, and we welcome new and old customers to choose their favorite products with confidence. We will be dedicated to serving you!
PCT Test Purpose and Application (3)
The way water vapor enters the IC package:
1. Water absorbed by IC chip and lead frame and silver paste used in SMT
2. Moisture absorbed in the plastic sealing material
3. The device may be affected when the humidity in the plastic sealing room is high;
4. After the encapsulation of the device, water vapor permeates through the plastic sealant and the gap between the plastic sealant and the lead frame, because there is only a mechanical combination between the plastic and the lead frame, so there is inevitably a small gap between the lead frame and the plastic.
Note: As long as the gap between the sealant is greater than 3.4*10^-10m, water molecules can pass through the sealant protection Note: The airtight package is not sensitive to water vapor, generally do not use accelerated temperature and humidity test to evaluate its reliability, but to measure its air tightness, internal water vapor content, etc.
PCT test description for JESD22-A102:
It is used to evaluate the integrity of non-airtight packaged devices against water vapor in water vapor condensation or saturated water vapor environments. The sample is placed in a condensed, high-humidity environment under high pressure to allow water vapor to enter the package, exposing weaknesses in the package such as corrosion of the delamination and metallization layers. This test is used to evaluate new package structures or updates of materials and designs in the package body. It should be noted that there will be some internal or external failure mechanisms in this test that do not match the actual application situation. Since absorbed water vapor reduces the glass transition temperature of most polymer materials, an unreal failure mode may occur when the temperature is higher than the glass transition temperature.
External pin tin short circuit: The ionization effect caused by moisture in the package external pin will cause abnormal growth of ion migration, resulting in short circuit between pins.
Moisture causes corrosion inside the package:
The cracks caused by the moisture through the packaging process bring external ion contamination to the surface of the wafer, and after passing through the surface defects such as: protective layer pinholes, cracks, poor covers... Etc., into the semiconductor original, causing corrosion and leakage current... Such problems, if there is applied bias then the fault is more likely to occur.
PCT test conditions:
(Collate PCB, PCT, IC semiconductor and related materials have relevant test conditions on PCT[steam pot test]) PCT test purpose and application
Test name
temperature
humidity
time
Check items & add notes
JEDEC-22-A102
121 ℃
100%R.H.
168h
Other test time: 24h, 48h, 96h, 168h, 240h, 336h
Tensile stripping strength test of IPC-FC-241B-PCB copper laminated laminates
121 ℃
100%R.H.
100 h
The strength of the copper layer should be 1000 N/m
IC-Auto Clave test
121 ℃
100%R.H.
288h
Low dielectric high heat resistant multilayer board
121 ℃
100%R.H.
192h
PCB plug agent
121 ℃
100%R.H.
192h
PCB-PCT test
121 ℃
100%R.H.
30min
Check: Layers, bubbles, white spots
Lead-free solder accelerated life 1
100 ℃
100%R.H.
8h
Equivalent to 6 months under high temperature and humidity, activation energy =4.44eV
Lead-free solder accelerated life 2
100 ℃
100%R.H.
16h
Equivalent to a year of high temperature and humidity, activation energy =4.44eV
IC lead-free test
121 ℃
100%R.H.
1000h
Check every 500 hours
Liquid crystal panel adhesion test
121 ℃
100%R.H.
12h
Metal gasket
121 ℃
100%R.H.
24h
Semiconductor package test
121 ℃
100%R.H.
500, 1000 hours
PCB moisture absorption test
121 ℃
100%R.H.
5, 8h
FPC moisture absorption test
121 ℃
100%R.H.
192h
PCB plug agent
121 ℃
100%R.H.
192h
Multilayer material with low dielectric power and high heat resistance
121 ℃
100%R.H.
5h
Water absorption is less than 0.4 ~ 0.6%
High TG glass epoxy multilayer printed circuit board material
121 ℃
100%R.H.
5h
Water absorption is less than 0.55 ~ 0.65%
High TG glass epoxy multilayer printed circuit board - Heat resistance test after hygroscopic reflow welding
121 ℃
100%R.H.
3h
Heat resistance test of reflow welding after PCT test is completed (260℃/30 seconds)
Micro-etching Horizontal Browning (Co-Bra Bond)
121 ℃
100%R.H.
168h
Automotive PCB
121 ℃
100%R.H.
50, 100h
PCB for the main board
121 ℃
100%R.H.
30min
GBA carrier board
121 ℃
100%R.H.
24h
Accelerated wet resistance test of semiconductor devices
121 ℃
100%R.H.
8h
User selection environment test box must read
1、 Equipment selection criteria
There is currently no exact number of natural environmental factors and induced environmental factors that exist on the surface of the Earth and in the atmosphere, among which there are no less than a dozen factors that have a significant impact on the use and lifespan of engineering products (equipment). Engineers engaged in the study of environmental conditions for engineering products have compiled and summarized the environmental conditions that exist in nature and are induced by human activities into a series of testing standards and specifications to guide the environmental and reliability testing of engineering products. For example, GJB150- the National Military Standard of the People's Republic of China for Environmental Testing of Military Equipment, and GB2423- the National Standard of the People's Republic of China for Environmental Testing of Electrical and Electronic Products, which guides environmental testing of electrical and electronic products. Therefore, the main basis for selecting environmental and reliability testing equipment is the testing specifications and standards of engineering products.
Secondly, in order to standardize the tolerance of environmental testing conditions in experimental equipment and ensure the control accuracy of environmental parameters, national technical supervision agencies and various industrial departments have also formulated a series of calibration regulations for environmental testing equipment and detection instruments. Such as the national standard GB5170 of the People's Republic of China "Basic Parameter Calibration Method for Environmental Testing Equipment of Electrical and Electronic Products", and JJG190-89 "Trial Calibration Regulations for Electric Vibration Test Stand System" issued and implemented by the State Administration of Technical Supervision. These verification regulations are also an important basis for selecting environmental and reliability testing equipment. Testing equipment that does not meet the requirements of these verification regulations is not allowed to be put into use.
2、 Basic principles for equipment selection
The selection of environmental and reliability testing equipment should follow the following five basic principles:
1. Reproducibility of environmental conditions
It is impossible to fully and accurately reproduce the environmental conditions that exist in nature in the laboratory. However, within a certain tolerance range, people can accurately and approximately simulate the external environmental conditions that engineering products undergo during use, storage, transportation, and other processes. This passage can be summarized in engineering language as follows: "The environmental conditions (including platform environment) created by the testing equipment around the tested product should meet the requirements of the environmental conditions and their tolerances specified in the product testing specifications. The temperature box used for military product testing should not only meet the requirements of the national military standards GJB150.3-86 and GJB150.4-86 for different uniformity and temperature control accuracy. Only in this way can the reproducibility of environmental conditions be ensured in environmental testing.
2. Repeatability of environmental conditions
An environmental testing equipment may be used for multiple tests of the same type of product, and a tested engineering product may also be tested in different environmental testing equipment. In order to ensure the comparability of test results obtained for the same product under the same environmental testing conditions specified in the testing specifications, it is necessary to require the environmental conditions provided by the environmental testing equipment to be reproducible. This means that the stress levels (such as thermal stress, vibration stress, electrical stress, etc.) applied by environmental testing equipment to the tested product are consistent with the requirements of the same testing specification.
The repeatability of environmental conditions provided by environmental testing equipment is guaranteed by the national metrological verification department after passing the verification according to the verification regulations formulated by the national technical supervision agency. Therefore, it is necessary to require environmental testing equipment to meet the requirements of various technical indicators and accuracy indicators in the calibration regulations, and to not exceed the time limit specified in the calibration cycle in terms of usage time. If a very common electric vibration table is used, in addition to meeting technical indicators such as excitation force, frequency range, and load capacity, it must also meet the requirements of precision indicators such as lateral vibration ratio, table acceleration uniformity, and harmonic distortion specified in the calibration regulations. Moreover, the service life after each calibration is two years, and after two years, it must be re calibrated and qualified before being put into use.
3. Measurability of environmental condition parameters
The environmental conditions provided by any environmental testing equipment must be observable and controllable. This is not only to limit the environmental parameters within a certain tolerance range and ensure the reproducibility and repeatability of the test conditions, but also necessary for the safety of product testing, in order to prevent damage to the tested product caused by uncontrolled environmental conditions and unnecessary losses. At present, various experimental standards generally require that the accuracy of parameter testing should not be less than one-third of the allowable error under experimental conditions.
4. Exclusion of environmental testing conditions
Every time an environmental or reliability test is conducted, there are strict regulations on the category, magnitude, and tolerance of environmental factors, and non test required environmental factors are excluded from penetrating into it, in order to provide a definite basis for judging and analyzing product failure and fault modes during or after the test. Therefore, it is required that environmental testing equipment not only provide the specified environmental conditions, but also not allow any other environmental stress interference to be added to the tested product. As defined in the verification regulations for electric vibration tables, the table leakage magnetic flux, acceleration signal-to-noise ratio, and total root mean square value ratio of in band and out of band acceleration. The accuracy indicators such as random signal verification and harmonic distortion are all established as verification items to ensure the uniqueness of environmental testing conditions.
5. Safety and reliability of experimental equipment
Environmental testing, especially reliability testing, has a long testing cycle and sometimes targets high-value military products. During the testing process, testing personnel often need to operate, inspect or test around the site. Therefore, it is required that environmental testing equipment must have the characteristics of safe operation, convenient operation, reliable use, and long working life to ensure the normal progress of the testing itself. The various protection, alarm measures, and safety interlock devices of the testing equipment should be complete and reliable to ensure the safety and reliability of the testing personnel, the tested products, and the testing equipment itself.
3、 Selection of Temperature and Humidity Chamber
1. Selection of Capacity
When placing the test product (components, assemblies, parts or whole machine) into a climate chamber for testing, in order to ensure that the atmosphere around the test product can meet the environmental testing conditions specified in the test specifications, the working dimensions of the climate chamber and the overall dimensions of the test product should follow the following regulations:
a) The volume of the tested product (W × D × H) shall not exceed (20-35)% of the effective working space of the test chamber (20% is recommended). For products that generate heat during testing, it is recommended to use no more than 10%.
b) The ratio of the windward cross-sectional area of the tested product to the total area of the test chamber on that section shall not exceed (35-50)% (35% is recommended).
c) The distance between the outer surface of the tested product and the wall of the test chamber should be kept at least 100-150mm (recommended 150mm).
The above three provisions are actually interdependent and unified. Taking a 1 cubic meter cube box as an example, an area ratio of 1: (0.35-0.5) is equivalent to a volume ratio of 1: (0.207-0.354). A distance of 100-150mm from the box wall is equivalent to a volume ratio of 1: (0.343-0.512).
In summary, the working chamber volume of the climate environment test chamber should be at least 3-5 times the external volume of the tested product. The reasons for making such regulations are as follows:
After the test piece is placed in the box, it occupies the smooth channel, and narrowing the channel will lead to an increase in airflow velocity. Accelerate the heat exchange between the airflow and the test piece. This is inconsistent with the reproduction of environmental conditions, as relevant standards stipulate that the air flow velocity around the test specimen in the test chamber should not exceed 1.7m/s for temperature environmental tests, in order to prevent the test specimen and the surrounding atmosphere from generating heat conduction that is not in line with reality. When unloaded, the average wind speed inside the test chamber is 0.6-0.8m/s, not exceeding 1m/s. When the space and area ratio specified in points a) and b) are met, the wind speed in the flow field may increase by (50-100)%, with an average maximum wind speed of (1-1.7) m/s. Meet the requirements specified in the standards. If the volume or windward cross-sectional area of the test piece is increased without restrictions during the experiment, the actual airflow speed during the test will exceed the maximum wind speed specified in the test standard, and the validity of the test results will be questioned.
The accuracy indicators of environmental parameters in the working chamber of the climate chamber, such as temperature, humidity, salt spray settling rate, etc., are all measured under no-load conditions. Once the test piece is placed, it will have an impact on the uniformity of the environmental parameters in the working chamber of the test chamber. The larger the space occupied by the test piece, the more severe this impact will be. Experimental data shows that the temperature difference between the windward and leeward sides in the flow field can reach 3-8 ℃, and in severe cases, it can be as high as 10 ℃ or more. Therefore, it is necessary to meet the requirements of a] and b] as much as possible to ensure the uniformity of environmental parameters around the tested product.
According to the principle of heat conduction, the temperature of the airflow near the box wall is usually 2-3 ℃ different from the temperature at the center of the flow field, and may even reach 5 ℃ at the upper and lower limits of high and low temperatures. The temperature of the box wall differs from the temperature of the flow field near the box wall by 2-3 ℃ (depending on the structure and material of the box wall). The greater the difference between the test temperature and the external atmospheric environment, the greater the temperature difference. Therefore, the space within a distance of 100-150mm from the box wall is unusable.
2. Selection of temperature range
At present, the range of temperature test chambers abroad is generally -73 to+177 ℃, or -70 to+180 ℃. Most domestic manufacturers generally operate at -80 to+130 ℃, -60 to+130 ℃, -40 to+130 ℃, and there are also high temperatures up to 150 ℃. These temperature ranges can usually meet the temperature testing needs of the vast majority of military and civilian products in China. Unless there are special requirements, such as products installed near heat sources such as engines, the upper temperature limit should not be blindly increased. Because the higher the upper limit temperature, the greater the temperature difference between the inside and outside of the box, and the poorer the uniformity of the flow field inside the box. The smaller the available studio size. On the other hand, the higher the upper limit temperature value, the higher the heat resistance requirements for insulation materials (such as glass wool) in the interlayer of the box wall. The higher the requirement for the sealing of the box, the higher the production cost of the box.
3. Selection of humidity range
The humidity indicators given by domestic and foreign environmental test chambers are mostly 20-98% RH or 30-98% RH. If the humid heat test chamber does not have a dehumidification system, the humidity range is 60-98%. This type of test chamber can only perform high humidity tests, but its price is much lower. It is worth noting that the corresponding temperature range or minimum dew point temperature should be indicated after the humidity index. Because relative humidity is directly related to temperature, for the same absolute humidity, the higher the temperature, the lower the relative humidity. For example, if the absolute humidity is 5g/Kg (referring to 5g of water vapor in 1kg of dry air), when the temperature is 29 ℃, the relative humidity is 20% RH, and when the temperature is 6 ℃, the relative humidity is 90% RH. When the temperature drops below 4 ℃ and the relative humidity exceeds 100%, condensation will occur inside the box.
To achieve high temperature and high humidity, simply spray steam or atomized water droplets into the air of the box for humidification. Low temperature and humidity are relatively difficult to control because the absolute humidity at this time is very low, sometimes much lower than the absolute humidity in the atmosphere. It is necessary to dehumidify the air flowing inside the box to make it dry. At present, the vast majority of temperature and humidity chambers both domestically and internationally adopt the principle of refrigeration and dehumidification, which involves adding a set of refrigeration light pipes to the air conditioning room of the chamber. When humid air passes through a cold pipe, its relative humidity will reach 100% RH, as the air saturates and condenses on the light pipe, making the air drier. This dehumidification method theoretically can reach dew point temperatures below zero degrees, but when the surface temperature of the cold spot reaches 0 ℃, the water droplets condensed on the surface of the light pipe will freeze, affecting the heat exchange on the surface of the light pipe and reducing the dehumidification capacity. Also, because the box cannot be completely sealed, humid air from the atmosphere will seep into the box, causing the dew point temperature to rise. On the other hand, the moist air flowing between the light tubes only reaches saturation at the moment of contact with the light tubes (cold spots) and releases water vapor, so this dehumidification method is difficult to keep the dew point temperature inside the box below 0 ℃. The actual minimum dew point temperature achieved is 5-7 ℃. A dew point temperature of 5 ℃ is equivalent to an absolute moisture content of 0.0055g/Kg, corresponding to a relative humidity of 20% RH at a temperature of 30 ℃. If a temperature of 20 ℃ and a relative humidity of 20% RH are required, with a dew point temperature of -3 ℃, it is difficult to use refrigeration for dehumidification, and an air drying system must be selected to achieve it.
4. Selection of control mode
There are two types of temperature and humidity test chambers: constant test chamber and alternating test chamber.
The ordinary high and low temperature test chamber generally refers to a constant high and low temperature test chamber, which is controlled by setting a target temperature and has the ability to automatically maintain a constant temperature to the target temperature point. The control method of the constant temperature and humidity test chamber is also similar, setting a target temperature and humidity point, and the test chamber has the ability to automatically maintain a constant temperature to the target temperature and humidity point. The high and low temperature alternating test chamber has one or more programs for setting high and low temperature changes and cycles. The test chamber has the ability to complete the test process according to the preset curve, and can accurately control the heating and cooling rates within the maximum heating and cooling rate capability range, that is, the heating and cooling rates can be controlled according to the slope of the set curve. Similarly, the high and low temperature alternating humidity test chamber also has preset temperature and humidity curves, and the ability to control them according to the preset. Of course, alternating test chambers have the function of constant test chambers, but the manufacturing cost of alternating test chambers is relatively high because they need to be equipped with curve automatic recording devices, program controllers, and solve problems such as turning on the refrigeration machine when the temperature in the working room is high. Therefore, the price of alternating test chambers is generally more than 20% higher than that of constant test chambers. Therefore, we should take the need for experimental methods as the starting point and choose a constant test chamber or an alternating test chamber.
5. Selection of variable temperature rate
Ordinary high and low temperature test chambers do not have a cooling rate indicator, and the time from the ambient temperature to the nominal lowest temperature is generally 90-120 minutes. The high and low temperature alternating test chamber, as well as the high and low temperature alternating wet heat test chamber, both have temperature change speed requirements. The temperature change speed is generally required to be 1 ℃/min, and the speed can be adjusted within this speed range. The rapid temperature change test chamber has a fast temperature change rate, with heating and cooling rates ranging from 3 ℃/min to 15 ℃/min. In certain temperature ranges, the heating and cooling rates can even reach over 30 ℃/min.
The temperature range of various specifications and speeds of rapid temperature change test chambers is generally the same, that is, -60 to+130 ℃. However, the temperature range for assessing the cooling rate is not the same. According to different test requirements, the temperature range of rapid temperature change test chambers is -55 to+80 ℃, while others are -40 to+80 ℃.
There are two methods for determining the temperature change rate of the rapid temperature change test chamber: one is the average temperature rise and fall rate throughout the entire process, and the other is the linear temperature rise and fall rate (actually the average speed every 5 minutes). The average speed throughout the entire process refers to the ratio of the difference between the highest and lowest temperatures within the temperature range of the test chamber to the time. At present, the technical parameters of temperature change rate provided by various environmental testing equipment manufacturers abroad refer to the average rate throughout the entire process. The linear temperature rise and fall rate refers to the guaranteed temperature change rate within any 5-minute time period. In fact, for the rapid temperature change test chamber, the most difficult and critical stage to ensure the linear temperature rise and fall speed is the cooling rate that the test chamber can achieve during the last 5 minutes of the cooling period. From a certain perspective, the linear heating and cooling speed (average speed every 5 minutes) is more scientific. Therefore, it is best for the experimental equipment to have two parameters: the average temperature rise and fall speed throughout the entire process and the linear temperature rise and fall speed (average speed every 5 minutes). Generally speaking, the linear heating and cooling speed (average speed every 5 minutes) is half of the average heating and cooling speed throughout the entire process.
6. Wind speed
According to relevant standards, the wind speed inside the temperature and humidity chamber during environmental testing should be less than 1.7m/s. For the test itself, the lower the wind speed, the better. If the wind speed is too high, it will accelerate the heat exchange between the surface of the test piece and the airflow inside the chamber, which is not conducive to the authenticity of the test. But in order to ensure uniformity within the testing chamber, it is necessary to have circulating air inside the testing chamber. However, for rapid temperature change test chambers and comprehensive environmental test chambers with multiple factors such as temperature, humidity, and vibration, in order to pursue the rate of temperature change, it is necessary to accelerate the flow velocity of the circulating airflow inside the chamber, usually at a speed of 2-3m/s. Therefore, the wind speed limit varies for different usage purposes.
7. Temperature fluctuation
Temperature fluctuation is a relatively easy parameter to implement, and most test chambers produced by environmental testing equipment manufacturers can actually control temperature fluctuations within a range of ± 0.3 ℃.
8. Uniformity of temperature field
In order to simulate the actual environmental conditions that products experience in nature more accurately, it is necessary to ensure that the surrounding area of the tested product is under the same temperature environment conditions during environmental testing. Therefore, it is necessary to limit the temperature gradient and temperature fluctuation inside the test chamber. In the General Principles of Environmental Test Methods for Military Equipment (GJB150.1-86) of the National Military Standard, it is clearly stipulated that "the temperature of the measurement system near the test sample should be within ± 2 ℃ of the test temperature, and its temperature should not exceed 1 ℃/m or the total maximum value should be 2.2 ℃ (when the test sample is not working).
9. Precision control of humidity
The humidity measurement in the environmental testing chamber mostly adopts the dry wet bulb method. The manufacturing standard GB10586 for environmental testing equipment requires that the relative humidity deviation should be within ± 23% RH. To meet the requirements of humidity control accuracy, the temperature control accuracy of the humidity test chamber is relatively high, and the temperature fluctuation is generally less than ± 0.2 ℃. Otherwise, it will be difficult to meet the requirements for humidity control accuracy.
10. Cooling method selection
If the test chamber is equipped with a refrigeration system, the refrigeration system needs to be cooled. There are two forms of test chambers: air-cooled and water-cooled.
Forced air cooling
Water-cooling
Working conditions
The equipment is easy to install, only need to power on.
The ambient temperature should be lower than 28℃. If the ambient temperature is higher than 28℃, it has a certain impact on the refrigeration effect (preferably with air conditioning), the circulating cooling water system should be configured.
Heat exchange effect
Poor (relative to the water-cooling mode)
Stable, good
Noise
Large (relative to the water-cooling mode)
Less
The walk-in high and low temperature (humid and hot) laboratory also needs maintenance
Reminder: Remember to maintain the walk-in high and low temperature (humid and hot) laboratory as well!
1. The temperature and humidity testing system of the walk-in high and low temperature (humid and hot) laboratory must be operated and maintained by a dedicated person. Strictly follow the operating procedures of the system and avoid others from operating the system illegally.
2. Long term shutdown of the walk-in high and low temperature (humid and hot) laboratory can affect the effective service life of the system. Therefore, the system should be turned on and operated at least once every 10 days; Do not repeatedly stop the system in a short period of time. The number of starts per hour should be less than 5 times, and the time interval between each start stop should not be less than 3 times; Do not open the door of the walk-in temperature and humidity testing system at low temperatures to prevent damage to the door sealing tape.
3. A system usage file should be established to facilitate system maintenance and repair. The use of archives should record the start and end time (date) of each system operation, the type of experiment, and the ambient temperature; When the system malfunctions, provide a detailed description of the fault phenomenon as much as possible; The maintenance and repair of the system should also be recorded in as much detail as possible.
4. Conduct a monthly main power switch (leakage circuit breaker) operation test to ensure that the switch is used as a leakage protector while meeting the load capacity. The specific steps are as follows: first, please confirm that the main power switch is turned to "ON", which means the system is powered on, and then press the test button. If the switch lever of the residual current circuit breaker falls down, this function is normal.
5. The main box of the walk-in temperature and humidity testing system should be protected during use and should not be subjected to strong impacts from sharp or blunt objects.
6. To ensure the normal and clean supply of cooling water, the cooling water filter of the refrigeration unit should be cleaned every 30 days. If the local air quality is poor and the dust content in the air is high, the cooling water tower reservoir should generally be cleaned every 7 days.
7. The leakage, overload, and short-circuit protection characteristics of the residual current switch are set by Lab Companion manufacturer and cannot be adjusted arbitrarily during use to avoid affecting performance; After the leakage switch is disconnected due to a short circuit, the contacts need to be checked. If the main contacts are severely burned or have pits, maintenance is required.
8. The test products placed in the walk-in temperature and humidity testing system should be kept at a certain distance from the suction and exhaust ports of the air conditioning channel to avoid obstructing air circulation.
9. Overtemperature protector action test. Set the temperature of the over temperature protector to be lower than the temperature of the box. If there is an E0.0 alarm and buzzing sound, it indicates that its function is normal. After completing the above experiment, the temperature protection setting should be reset appropriately, otherwise it may cause inappropriate termination.
10. Once a year, use a vacuum cleaner to clean and remove dust from the distribution room and water circuit room. Once a month, use a dry cloth to clean the accumulated water in the water tray of the refrigeration unit.
Concentrator Solar Cell
A concentrating solar cell is a combination of [Concentrator Photovoltaic]+[Fresnel Lenes]+[Sun Tracker]. Its solar energy conversion efficiency can reach 31% ~ 40.7%, although the conversion efficiency is high, but due to the long sunward time, it has been used in the space industry in the past, and now it can be used in the power generation industry with sunlight tracker, which is not suitable for general families. The main material of concentrating solar cells is gallium arsenide (GaAs), that is, the three five group (III-V) materials. General silicon crystal materials can only absorb the energy of 400 ~ 1,100nm wavelength in the solar spectrum, and the concentrator is different from silicon wafer solar technology, through the multi-junction compound semiconductor can absorb a wider range of solar spectrum energy, and the current development of three-junction InGaP/GaAs/Ge concentrator solar cells can greatly improve the conversion efficiency. The three-junction concentrating solar cell can absorb energy of 300 ~ 1900nm wavelength relative to its conversion efficiency can be greatly improved, and the heat resistance of concentrating solar cells is higher than that of general wafer-type solar cells.
Temperature and Humidity Terms
Dew Point temperature Td, in the air water vapor content unchanged, maintain a certain pressure, so that the air cooling to reach saturation temperature called dew point temperature, referred to as dew point, the unit is expressed in ° C or ℉. It's actually the temperature at which water vapor and water are in equilibrium. The difference between the actual temperature (t) and the dew point temperature (Td) indicates how far the air is saturated. When t>Td, it means that the air is not saturated, when t=Td, it is saturated, and when t<Td, it is supersaturated.
dew is the liquid water in the air that condenses on the ground. In the evening or at night, due to the radiation cooling of the ground or ground objects, the air layer close to the surface will also cool down. When the temperature drops below the dew point, that is, when the water vapor content in the air is susaturated, there will be condensation of water vapor on the surface of the ground or ground objects. If the dew point temperature is above 0 ° C at this time, tiny water droplets appear on the ground or ground objects, which are called dew.
frost refers to the white ice crystals formed on the ground or objects after the air close to the ground is cooled to the frost point (meaning the dew point is below 0) under the influence of radiation cooling on the ground.
fog refers to the condensation of water vapor suspended in the atmosphere near the Earth's surface, composed of small water droplets or ice crystals. When the temperature reaches the dew point temperature (or is close to the dew point), the water vapor in the air condenses to form fog.
snow is solid water in the form of snowflakes that falls to the ground from mixed clouds. Precipitation consisting of a large number of white opaque ice crystals (snow crystals) and their polymers (snow masses). Snow is the natural phenomenon of water condensing and falling in the air, or falling snow;
There is a limit to the amount of water vapor that can be contained in a unit volume of air under a certain pressure and a certain temperature. If the water vapor contained in the volume of air exceeds this limit, the water vapor will condense and produce precipitation, and the actual value of water vapor in the volume of air. In terms of absolute humidity. The more water vapor there is, the higher the absolute humidity of the air.
Relative Humidity refers to the percentage of water vapor pressure in the air and saturated water vapor pressure at the same temperature, or the ratio of the absolute humidity of wet air to the maximum absolute humidity that can be reached at the same temperature, and can also be expressed as the ratio of the partial pressure of water vapor in wet air to the saturation pressure of water at the same temperature.
Humidity: wet and dry bulb measurement
The dry and wet bulb thermometer is used to detect the [relative humidity] in the air, the dry bulb temperature is the temperature measured by the general temperature sensor, and the wet bulb temperature is tied on the temperature sensor with a wet cloth, and then soaked in a small cup of water, so that the water is wrapped in the whole sensor, because the relative humidity in the air must be less than or equal to 100% (the water vapor in the air is not saturated). Therefore, the moisture of the wet bulb will be evaporated, and the heat will be taken away during evaporation, resulting in a drop in the wet bulb temperature (the dry bulb temperature is the real air temperature), which means that the greater the difference in the readings of the dry and wet bulb thermometer, the more vigorous the evaporation of water, and the smaller the relative humidity in the air, as long as the temperature of the dry and wet bulb is measured, Then compare [relative humidity table] you can know the relative humidity of the environment at that time.
Maintenance of refrigeration compressor for constant temperature and humidity test chamber, cold and hot shock test chamber
Article summary: For environmental monitoring equipment, the only way to maintain long-term and stable use is to pay attention to maintenance in all aspects. Here, we will introduce the maintenance of the compressor, which is an important component of the constant temperature and humidity test chamber and the cold and hot shock test chamber
Detailed content:
Maintenance plan for refrigeration compressor:
As the core component of the refrigeration system in the constant temperature and humidity test chamber, the maintenance of the compressor is essential. Guangdong Hongzhan Technology Co., Ltd. introduces the daily maintenance steps and precautions for the compressor in the constant temperature and humidity test chamber and the cold and hot shock test chamber
1、 Carefully check the sound of the cylinders and moving parts at all levels to determine if their working condition is normal. If any abnormal sound is found, immediately stop the machine for inspection;
2、 Pay attention to whether the indicated values of pressure gauges at all levels, pressure gauges on gas storage tanks and coolers, and lubricating oil pressure gauges are within the specified range;
3、 Check if the temperature and flow rate of the cooling water are normal;
4、 Check the supply of lubricating oil and the lubrication system of the moving mechanism (some compressors are equipped with organic glass baffles on the side of the cross head guide rail of the machine body),
You can directly see the movement of the crosshead and the supply of lubricating oil; The cylinder and packing can be inspected for oil discharge using a one-way valve, which can check if the oil injector is inserted into the cylinder
Oil injection situation;
5、 Observe whether the oil level in the body oil tank and the lubricating oil in the oil injector are below the scale line. If they are low, they should be refilled in a timely manner (if using a dipstick, stop and check);
6、 Check the temperature of the intake and exhaust valve covers at the cross guide rail of the crankcase with your hand to see if it is normal;
7、 Pay attention to the temperature rise of the motor, bearing temperature, and whether the readings on the voltmeter and ammeter are normal. The current should not exceed the rated current of the motor. If it exceeds the rated current, the cause should be identified or the machine should be stopped for inspection;
8、 Regularly check whether there are any debris or conductive objects inside the motor, whether the coil is damaged, and whether there is friction between the stator and rotor, otherwise the motor will burn out after starting;
9、 If it is a water-cooled compressor and water cannot be immediately supplied after the water is cut off, it is necessary to avoid cylinder cracking due to uneven heating and cooling. After parking in winter, the cooling water should be drained to prevent freezing and cracking of the cylinder and other parts;
10、 Check whether the compressor vibrates and whether the foundation screws are loose or detached;
11、 Check whether the pressure regulator or load regulator, safety valve, etc. are sensitive;
12、 Pay attention to the hygiene of the compressor, its associated equipment, and the environment;
13、 Gas storage tanks, coolers, and oil-water separators should regularly release oil and water;
14、 The lubricating machine used should be filtered by sedimentation. Differentiate the use of compressor oil between winter and summer
EC-105HTP,MTP,MTHP, High and low temperature constant temperature bath (1000L)
Project
Type
Series
ＨＴ
ＭＴ
ＭＴＨ
function
Temperature occurs in a way
Dry wet bulb method
Temperature range
-20 ～ + 100 ℃
-40 ～ + 100 ℃
-40 ～ + 150 ℃
Range of temperature
Below the + 100℃
± 0.3 ℃
+Above the 101℃
―
± 0.5 ℃
Temperature distribution
Below the + 100℃
± 1.0 ℃
Above the + 101℃
―
± 2.0 ℃
The temperature drops the time
+20 ～ -20 ℃
Within 60 minutes
+20 ～ -40 ℃
Within 9 0 minutes
+20 ～ -40 ℃
Within 9 0 minutes
Temperature rise time
-20 ～ + 100 ℃
Within 45 minutes
-40 ～ + 100 ℃
Within 50 minutes
-40 ～ + 150 ℃
Within 75 minutes
The internal volume of the uterus was tested
1000Ｌ
Test room inch method (width, depth and height)
1000mm × 1000mm × 1000mm
Product inch method (width, depth and height)
1400mm × 1370mm × 1795mm
Make the material
External outfit
Test room control panel
machine room
Cold steel plate, cold steel plate beige
(Color table 2.5Y8 / 2)
Inside
Stainless steel plate (SUS304,2B polished)
Broken heat material
Test room
Hard synthetic resin
―
glass wool
door
Hard synthetic resin foam cotton, glass cotton
Project
Type
Series
ＨＴ
ＭＴ
ＭＴＨ
Cooling dehumidifying device
Cooling-down method
Mechanical section shrinkage mode
Cooling medium
Ｒ４０４Ａ
compressor
Output (number of units)
0.75kW （１）
1.5kW （１）
Cooling and dehumidifier
Multi-channel mixed heat sink type
The condenser
Multi-channel mixed radiator plate type (air cooling type)
Calorifier
Form
Nickel-chromium heat-resistant alloy heater
Volume
3.5kW
Blower
Form
Multi-channel mixed radiator plate type (air cooling type)
Motor capacity
40W
Controller
The temperature is set
-22.0 ～ + 102.0 ℃
-42.0 ～ + 102.0 ℃
-42.0 ～ + 152.0 ℃
Humidity is set
0 ～ 98%RH （But the temperature of the wet and dry bulb is 10-85 ℃ ）
Time setting Fanny
0 ~ 999 Time 59 minutes (formula) 0 ~ 20000 Time 59 minutes (formula formula)
Set decomposition energy
Temperature 0.1℃, humidity 1% RH for 1 min
Indicate accuracy
Temperature ± 0.8℃ (tp.), humidity ± 1% RH (tp.), time ± 100 PPM
Vacation type
Value or program
Stage number
20-stage / 1 program
The number of procedures
The maximum number of incoming force (RAM) programs is 32 programs
The maximum number of internal ROM programs is 13 programs
Round-trip number
98 times maximum or unlimited
Number of round-trip repeats
Maximum 3 times
Displace the end
Pt 100Ω（at 0 ℃）， gradeＢ（JIS C 1604-1997）
Control action
When splitting the PID action
Endovirus function
Early delivery function, standby function, setting value maintenance function, power outage protection function,
Power action selection function, maintenance function, transportation round-trip function,
Time delivery function, time signal output function, overrising and overcooling prevention function,
Abnormal representation function, external alarm output function, setting paradigm representation function,
Transport type selection function, the calculation time represents the function, the slot lamp lamp function
Project
Type
Series
ＨＴ
ＭＴ
ＭＴＨ
Control panel
Equipment machine
LCD operating panel (type contact panel),
Represents lamp (power, transport, abnormal), test power supply terminal, external alarm terminal,
Time signal output terminal, power cord connector
Protective device
Refrigerating cycle
Overload protection device, high blocking device
Calorifier
Temperature over-rise protection device, temperature fuse
Blower
Overload protection device
Control panel
Leakage breaker for power supply, fuse (for heater, humidifier),
Fuse (for operating loop), temperature rise protection device (for testing),
Temperature rise overcooling prevention device (test material, in microcomputer)
Offproducts (sets)
House receiving (4), house board (2), operation instructions (1)
Equipment products
Adventitia
hard borosilicate glass 270mm× 190mm
２
Cable hole
内径 50mm
１
The trough inside the lamp
AC100V 15W White hot ball
２
Wheel
４
Horizontal adjustment
４
Electrovirus characteristics
Source *
AC three-phase 380V 50Hz
Maximum load current
13A
15A
Capacity of the leakage breaker for the power supply
25 A
Sensory current 30mA
Power distribution thickness
8mm2
14mm2
Rubber insulation hose
Coarseness of grounding wire
3.5mm2
5.5mm2
Tubing
drain-pipe *
PT1/2
Product weight
470kg
540kg
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