Stress Protocol
Specific test protocol for measuring the moisture resistance of non-hermetic packaged semiconductor devices defines the standard. Jesd22-a110 is often referred to as the highly accelerated temperature and humidity stress test. Procedure identifies weaknesses in the protective coatings and seals of the chip.
Electrical Bias
Electrical voltage is applied to the device while it is exposed to high temperature and high humidity. This combination accelerates the corrosion of the internal metal layers and the growth of parasitic conductive paths. Goal is to simulate the effects of long-term exposure to a harsh environment in a very short time.
Failure Acceleration
Testing at one hundred and thirty degrees Celsius and eighty-five percent relative humidity can reveal defects in just a few hundred hours. Common failure modes include wire bond degradation and the breakdown of the passivation layer. Passing this test indicates that the design is suitable for use in automotive or outdoor industrial applications.
Test Duration
Qualifying a new product requires multiple batches to be tested for a duration that correlates with the expected service life. Engineers monitor the devices for any changes in leakage current or functional performance during the exposure. A single failure in the sample set can lead to the rejection of the entire design.
Results are documented in a formal report that stays with the product throughout its life cycle. This rigorous screening ensures that the microelectronics can survive the moisture and heat encountered in the real world without a premature breakdown of the insulation. Adherence to the specified ramp-up and ramp-down rates prevents thermal shock from invalidating the results.
