John McMahon, Russell Brush, and Brian Standing
Toronto, ON, Canada
Accelerated thermal cycling (ATC) is the accepted test methodology for characterizing the expected service life of electronic components. When combined with vibration, shock and bend testing it can provide a reasonable confidence that the material under test will perform robustly in field service. Since the year 2005 the team has conducted ATC testing on over 500 lots of components. Looking back at some of the early work and how those assembly lots would compare to current industry expectations provides some real insight to the progress made by the industry.
Package technology has progressed significantly as have process materials and chemistry. There are specific component categories where comparisons are easier to make. Ceramic ball grid array (CBGA) components are one such case.
This paper compares assembly and test of various 1.0 mm pitch CBGAs conducted between 2005 and 2014 and ranging from 32.5 x 32.5 mm and 937 IO to 55 x 55 mm and 2892 IO. Assembly yields and processes are compared as well as ATC test results. Weibull distributions and parameters are provided along with selected destructive failure analysis and discussion of the mechanisms.
These observations lead us to the following conclusions:
- The use of SMD pads at the corners of Ceramic parts for mechanical support can affect the region of solder fatigue within the BGA solder joint but does not appear to have any significant impact on chamber life.
- The beneficial effect of LTCC substrate material is significant and has by itself extended the chamber life of ceramic components.
- The use of standoffs under the corners of large ceramic BGA packages appears to generate more consistent solder joint heights from PA and FR processes.
- The use of modern edge bond material can significantly increase chamber cycling life by a factor of 3X or more.
- The positive effect of edge bond material has been replicated in multiple ATC tests using IPC9701, Test Condition 1.
Initially Published in the SMTA Proceedings