Reliability Evaluation of Aluminum-Metallized MOS Dynamic RAM´s in Plastic Packages in High Humidity and Temperature Environments

Analysis of accelerated aging data indicates that room temperature vulcanizing (RTV) silicone rubber coated aluminum metallized N-type metal-oxide semiconductor (NMOS) devices in plastic packages will perform reliably in typical Bell System use environments. For example, a 4K bit dynamic random access memory (DRAM) operating with zero power dissipation in a worst case central office environment will reach 100 FIT¹failure rate in about 400 years. The Same device in a worst case customer premises or exposed Baton Rouge, LA environment will reach 100 FIT in 40 years at zero power dissipation or 100 FIT in 100 years with 100 mW power dissipation (~6°C temperature rise over ambient). These reliability estimates are based on Bell Telephone Laboratories (BTL) stress test results at 85°C and 85 percent relative humidity (RH) and acceleration factors obtained by an analysis of published aluminum corrosion data which was applied to an Eyring model. The details of this analysis are presented, along with curves that will permit a system user to estimate the failure rate of a typical aluminum metallized MOS device in any set of temperature and humidity conditions at several values of device temperature rise.