Burn-in Oven
Burn-in is an electrical stress test that employs voltage and temperature to accelerate the electrical failure of a device. Burn-in essentially simulates the operating life of the device, since the electrical excitation applied during burn-in may mirror the worst-case bias that the device will be subjected to in the course of its useable life. Depending on the burn-in duration used, the reliability information obtained may pertain to the device's early life or its wear-out. Burn-in may be used as a reliability monitor or as a production screen to weed out potential infant mortalities from the lot.
Burn-in is usually done at 125 deg C, with electrical excitation applied to the samples. The burn-in process is facilitated by using burn-in boards (see Fig. 1) where the samples are loaded. These burn-in boards are then inserted into the burn-in oven (see Fig. 2), which supplies the necessary voltages to the samples while maintaining the oven temperature at 125 deg C. The electrical bias applied may either be static or dynamic, depending on the failure mechanism being accelerated.
Figure 1. Photo of Bare and Socket-populated Burn-in Boards
The operating life cycle distribution of a population of devices may be modeled as a bath tub curve, if the failures are plotted on the y-axis against the operating life in the x-axis. The bath tub curve shows that the highest failure rates experienced by a population of devices occur during the early stage of the life cycle, or early life, and during the wear-out period of the life cycle. Between the early life and wear-out stages is a long period wherein the devices fail very sparingly.
Figure 2. Burn-in ovens
Early life failure (ELF) monitor burn-in, as the name implies, is performed to screen out potential early life failures. It is conducted for a duration of 168 hours or less, and normally for only 48 hours. Electrical failures after ELF monitor burn-in are known as early life failures or infant mortality, which means that these units will fail prematurely if they were used in their normal operation.
High Temperature Operating Life (HTOL) Test is the opposite of ELF monitor burn-in, testing the reliability of the samples in their wear-out phase. HTOL is conducted for a duration of 1000 hours, with intermediate read points at 168 H and 500 H.
Although the electrical excitation applied to the samples are often defined in terms of voltages, failure mechanisms accelerated by current (such as electromigration) and electric fields (such as dielectric rupture) are understandably accelerated by burn-in as well.
Lab Ovens and Lab Furnaces
Design with sample protection as the primary goal
Lab ovens are an indispensable utility for your daily workflow, from simple glassware drying to very complex temperature-controlled heating applications. Our portfolio of heating and drying ovens provides temperature stability and reproducibility for all your application needs. LABCOMPANION heating and drying ovens are designed with sample protection as a primary goal, contributing to superior efficiency, safety and ease of use.
Understand natural and mechanical convection
Principle of natural convection:
In a natural convection oven, hot air flows from bottom to bottom, so that the temperature is evenly distributed (see figure above). No fan actively blows the air inside the box. The advantage of this technology is ultra-low air turbulence, which allows for mild drying and heating.
Principle of mechanical convection:
In a mechanical convection (forced air drive) oven, an integrated fan actively drives the air inside the oven to achieve uniform temperature distribution throughout the chamber (see figure above). A major advantage is excellent temperature uniformity, which enables reproducible results in applications such as material testing, as well as for drying solutions with very demanding temperature requirements. Another advantage is that the drying rate is much faster than natural convection. After opening the door, the temperature in the mechanical convection oven will be restored to the set temperature level more quickly.
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