Cost-Effective Testing Solutions for Sealing Material With IR Package

Abstract

Hermeticity is one of the critical issues for infrared (IR) device package since the leakage will impair the functionality of the device. In this paper, two types of tests are conducted, i.e., moisture sensitivity test and helium leakage test. Pure material moisture sensitivity test is done in the first step, for the samples are made of pure hermetic sealing material and the cost is very low. The samples are subjected to moisture sensitivity level 1 (MSL1) condition, then desorbed by isothermal thermogravimetric analysis TGA at constant temperature 85 °C, and then followed by subsequent simulations to compare void penetration time and final relative humidity for different types of materials. The results show that the simulation can extend the time of the test to the fully dry/saturated condition, so that the test time/labor cost can be greatly reduced. The test results show that epoxy-based materials are suitable for this method. The moisture diffusion data repeatability is quite good and strictly follows Fick’s law. For glass material, TGA test has limitations in sample preparation. Voids are generated in glass samples during screen printing, which will lead to inaccurate test results. Then, helium leakage test is done by using alumina substrate bottom casing hermetically sealed by a silicon filter as the testing sample. The selected sealing materials are the ones with longer penetration time in TGA test and simulation. Bonding surfaces have no surface finish considering low cost. Sample preparation is not limited to epoxy-based materials. High-temperature storage (HTS) and thermal cycling (TC) are carried out to detect the hermeticity changes. The results show that some of the glass samples have peeling issues with anti-reflective coating after reliability test, although helium leak rate is slightly better. In conclusion, the advantage of moisture sensitivity test is low cost and can identify whether the material can pass or fail MSL1 condition. However, helium leakage test has fewer limitations in sample preparation. Combined with TC and HTS, helium leakage test can detect the material degradation and bonding quality effect. TGA and helium leakage test are combined together to enhance the hermeticity of IR package in this paper.