The high cycle fatigue (HCF) durability of SAC solders has not been investigated to the same extent as SnPb solder [1] [2] [3], especially as a function of temperature. This is a first essential step towards understanding the interaction between thermal cycling damage and vibration damage [4] [5]. In this study, vibration durability is investigated under step-stress broad-band random vibration excitation at different temperatures. The test vehicle consists of various common surface mount components soldered onto a test PWB. The solder system, plating system and thermal pre-conditioning are systematically varied. Twenty printed wiring assemblies are tested at a time in a specially designed fixture on an electrodynamic shaker. The test setup is first characterized before conducting the durability experiment, by collecting strain histories at different sites on the PWB, mounted at different locations on the fixture, under different loading conditions. These strain results are useful to be able to compare the performance of the assemblies at different strain conditions and as inputs for subsequent finite element analysis (FEA) to estimate acceleration factors for various field environments [6]. In order to check the temperature dependence of the vibration durability, the broad-band vibration durability tests have been repeated at room temperature, high temperature and low temperature. Test results are reported in this paper, and important trends are identified for SAC and SnPb solder systems. Destructive failure analysis (cross-sectioning, polishing and microscopy) is used to confirm that the failure is by solder fatigue.

This content is only available via PDF.
You do not currently have access to this content.