THE GREAT SAC DEBATE: COMPARING THE RELIABILITY OF SAC305 AND SAC405 SOLDERS IN A VARIETY OF APPLICATIONS

摘要

This paper compares the results of reliability testing of SAC305 and SAC405 in three different cases on a test vehicle representative of a mid-complexity server-type product which included a range of component types from CBGAs to discrete resistors. The first case compares the reliability of pure SAC305 assemblies to pure SAC405 on a variety of surface finishes, including ENIG, ImmAg, ImmSn, Electrolytic Ni/Au and OSP. These assemblies 1-4 differ from those used in many other studies in that SAC305 balled area array components were used on assemblies screened with SAC305 paste, and SAC405 balled area array components were used on assemblies screened with SAC405 paste, resulting in pure SAC305 or pure SAC405 systems. Many previous studies have used area array components balled with SAC405, but increasing use of SAC305 by component suppliers for balling area array components means it can no longer be assumed that of these assemblies was determined in 0°C to 100°C thermal cycling. In the second case, a small sub-set of the assemblies, again, either pure SAC305 or pure SAC405 systems, were tested in harsher -55°C to 125°C thermal cycling more representative of a military or aerospace end- use environment. In the third case, the reliability of mixed assemblies created with either SAC305 or SAC405 balled components and tin/lead paste was studied using the 0°C to 100°C thermal cycle to determine if the difference in composition of the component ball affects the reliability of the resulting assembly.