Authors: Steve Vandervoort, Dudi Amir, Raiyo Aspandiara, Fay Hua, Bin Li, Gregorio Murtagian, and Rajen S. Sidhu Company: Intel Corporation Date Published: 10/4/2009
Abstract: Reported incidences of head-and-pillow (HnP) solder joint defects for ball grid array (BGA) components have increased significantly with the conversion to lead-free solder ball alloys. Though the literature on this solder joint defect has focused mainly on fine-pitch BGA packages, BGA sockets are not immune to the HnP defect, even with relatively larger ball pitches. In this paper, we will report on HnP defects observed after surface mount assembly with specific focus on BGA sockets on motherboards. The mechanism for the formation of this defect in the sockets will be described. Various aspects of the design and materials of these BGA sockets differ in some respects from those of BGA packages. How these relevant design and materials characteristics affect the generation of this HnP defect within the socket solder joints will be elaborated on. Finally, potential solutions which have been evaluated and characterized to eliminate the defect in these sockets will be discussed.