Test chamber for environmental conditions with burn-in
As a test for multiple semiconductor products, burn-in chambers are ovens that evaluate the reliability of multiple devices and screen large quantities of them for premature failure (infant mortality). Environment chambers are designed to burn in integrated circuits (ICs) and other devices, such as laser diodes, over static or dynamic conditions.For a given production program, the chamber size is determined by the size of the burn-in board, the number of products to be burnt in, and the number of batches required per day.
Insufficient space between parts leads to poor performance if the interior space is too small. Burn-in Environmental Test Chamber Oversized items waste time, energy, and space. A company that is buying a new burn-in setup must ensure the heat source can handle the load of the DUT by working with the vendor. The use of forced recirculating airflow benefits parts by spacing them, but because airflow travels along the entire side of the oven, parts can be more densely packed vertically.
The temperature range for the chamber should be 15 °C above ambient to 300 °C, depending on the equipment to be tested (DUT). The chamber should be temperature stable. An unintended effect of an asymmetrical chamber is the lack of uniformity between the high and low temperatures. It is acceptable in most semiconductor burn-in applications to set the set point for uniformity to at least 1% and to control the temperature to at least 1.0 °C.
If burn-in requirements are very stringent, 0.1 °C resolution will be sufficient to meet them. Also, consider a refrigerant that has a negligible ozone depletion coefficient. When combustion chambers are operated in temperatures below 0 °C, they reach temperatures as low as –55 °Connecting DUT boards and driver boards to ATE stations can be made easier by providing card cages, card slots, and access doors.
Forced convection with recirculation of airflow is the best method of heating and transferring heat to parts; it also minimizes the time needed for parts to reach temperature and demonstrates fast heat transfer. It is important to design the fan, so the air is directed to all areas of the chamber to achieve temperature uniformity and performance. The airflow can be horizontal or vertical. Depending on the airflow in the chamber, it is critical to know the direction of insertion of the DUT.
Burn-in ovens use a temperature controller that executes an algorithm called PID (proportional, integral, derivative). Upon learning the real temperature value compared to the set point value, the controller sends a signal to the heater requesting the application of no heat to full heat as needed. Equalizing the temperature in the chamber is also achieved by using a fan.
An RTD (Resistance Temperature Detector), also known as a PT100, is the most common type of temperature sensor used in environmental ovens.Basic thermal modeling using oven thermal capacity and losses, heat sources output, and DUT mass will allow you to verify that the oven and heat source are capable of reaching the desired temperature with short enough thermal time constants for tight loop response under the controller.
