Soldering Reliability Study And Solder Material Selection Analysis In BGA Package

With the implementation of WEEE and ROHS by the EU, more and more Pb-freematerials and technologies come into the market. SnAg and SnAgCu alloys become verypopular, and will completely replace the PbSn solder alloys. In the meantime, the strengthof the solderabilty plays a more and more important role in the BGA package.Research to find the key factors which have big influence on the quality and reliabilityof the solder joints. And also try to study the advantages and disadvantages of various ofPb-free solder alloy recipes in terms of solderability.By using the reliability and failure analysis methods: shear test, pull test andmetallographic analysis, etc., which have been always implemented in BGA packages tocollect the experiment data, study the key factors and inter-relationships which haveinfluences on the solderability.The collapse of IMC is a major reason that causes the connection failure. In the solderalloy, with the reduction of Ag, the ductibility of materials is enhanced, which helpsabsorbing and distributing the stress between solder alloys and IMC. In the SnAgCu solderalloy, when the percentage of Cu<0.5%, the IMC layer is composed of both (CuNi)6Sn5and (NiCu)3Sn4, which can easily cause the collapse of the connection.Conclusions: In Pb-free solder balls，eg. SAC(Sn，Ag，Cu)，the proportion of Ag andCu are very critical and so have big influence on the quality and reliability of the solderjoints.