SMTA International Conference Proceedings


Author: Fay Hua et al.
Company: Intel Corporation
Date Published: 9/21/2003   Conference: SMTA International

Abstract: This is the second report in a series of studies conducted at Intel addressing the solder joint reliability of Sn-Ag-Cu BGA-type components attached with eutectic Pb-Sn solder (Pb-free backward compatibility). The packages used in these studies were: a) 0.5 mm pitch vfBGA (very fine ball grid array), b) 0.8mm pitch SCSP (stack chip scale package), c) 1.0mm pitch and 1.27mm pitch wbPBGA (wire bond plastic ball grid array) packages. This paper focuses in the wbPBGA components and in comparison with the other two packages addresses the BGA Scaling effects on backward compatibility.

The packages were assembled under various board reflow profiles using standard Pb-Sn assembly conditions. Peak reflow temperatures varied from 208°C to 222°C with a soak profile or a direct ramp up profile. These reflow profiles result in either a homogenous microstructure of the solder joint because of the melting and collapse of the Sn-Ag-Cu BGA balls or a non-homogenous microstructure due to partial melting and collapse of the BGA balls. The solder joint reliability (SJR) was evaluated in terms of resistance to failure by subjecting assemblies to temperature cycles (-40 °C to 125°C, 30 minutes per cycle) and mechanical shock testing. Results from this SJR testing and detailed failure analysis are reported.

Key words: solder joints, reliability, BGAs, Pb-free, Pb-Sn and Sn-Ag-Cu solder compatibility.

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