A CASE STUDY ON Pb-FREE PROCESS AND MATERIAL CHALLENGES IN THE ASSEMBLY OF LARGE FINE-PITCH BGA COMPONENTSAuthors: King Gonzalez, Ramgopal Uppalapati, Vasu Vasudevan
Company: Intel Corporation
Date Published: 9/24/2006 Conference: SMTA International
Material analysis was performed across a multitude of package types with varying ball pitch and body size. In addition, reliability performance was assessed by controlling material variations such as PCB surface finish, solder paste, and solder ball composition across multiple DOE legs using a reference assembly process window.
The results from the case study revealed failure modes related to assembly process and material issues suggesting strong sensitivity to material and process interactions and narrower process window using SnAgCu (SAC) alloy. The failure modes observed on ImAg boards include nonwetting and open joints under potential un-optimized reflow-profile conditions, and BGA solder joint (SJ) cracks related to planar microvoids. The paper lists recommendations to reduce or eliminate the observed issues to produce robust Pb-free PCBA process.
Key words: PCB, surface finish, Pb-free, BGA, OSP, and ImAg
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