FILL THE VOID III

摘要

This study is part three in a series of papers on voiding in solder joints and methods for mitigation of voids. In this study several new variables were tested and compared to previous data on voiding. A new circuit board design was used which is different than the circuit board used in previous studies. The new circuit board design includes two sizes of QFNs (Quad Flat No Lead), BGA's (Ball Grid Array), and LGA (Land Grid Array) components which are susceptible to voiding. The following variables were evaluated with respect to voiding: 1. Solder powder size was varied using a no-clean lead-free solder paste and IPC Type 3, Type 4 and Type 5 SAC305 solder powders. 2. Solder alloy was studied using SAC305 alloy, SN100C alloy, SN100CV alloy and a mixture of SAC305/SN100C alloys. 3. Surface finish on the circuit board is thought to have an impact on voiding. OSP surface finish is more difficult to wet with solder than other surface finishes and in theory should produce higher voiding levels, and this was evaluated with multiple solder pastes. 4. The performance of a new "low voiding" no clean solder paste was compared to other industry standard no clean solder pastes. 5. Several new stencil designs on QFN thermal pads were tested. These voiding results were summarized along with previous data on voiding and recommendations given to help the reader "Fill the Void."