Solder joint reliability in AgPt-metallized LTCC modules

Purpose - To investigate the effect of the metallization and solder mask materials on the solder joint reliability of low temperature co-fired ceramic (LTCC) modules. Design/methodology/approach - The fatigue performance of six LTCC/PCB assembly versions was investigated using temperature cycling tests in the - 40-125 degrees C and 20-80 degrees C temperature ranges. In order to eliminate fatigue cracking in the LTCC module itself, large AgPt-metallized solder (1 mm) lands with organic or co-fired glaze solder masks, having 0.86-0.89 mm openings, were used. The performance of these modules was compared to that of AgPd-metallized modules with a similar solder land structure. The joint structures were analysed using resistance measurements, scanning acoustic microscopy, SEM/EDS investigation, and FEM simulations. Findings - The results showed that failure distributions with Weibull shape factor (beta) values from 8.4 to 14.2, and characteristic life time (theta) values between 860 and 1,165 cycles were achieved in AgPt assemblies in the - 40-125 degrees C temperature range. The primary failure mechanism was solder joint cracking, whereas the AgPd-metallized modules suffered from cracking in the ceramic. In the milder test conditions AgPd-metallized modules showed better fatigue endurance than AgPt-metallized modules. Originality/value - This paper proves that the cracking in ceramic in the harsh test condition can be eliminated almost completely by using AgPt metallization instead of AgPd metallization in the present test module structure.