Suppressing Ni-Sn-P growth in SnAgCu/Ni-P solder joints

The interfacial morphologies for SnAgCu/Ni-P with various phosphorous contents were investigated by electron microscopy. The initial formation of the phosphorous-rich phase in Ni-P under-bump metallizations (UBMs) was dependent on phosphorous content, i.e., Ni3P for Ni-7 wt.%P UBM and Ni12P5 for Ni-13 wt.%P UBM. Different Ni xP y phases significantly affected the subsequent Ni-Sn-P formation. The growth of Ni-Sn-P could be thus controlled by altering the phosphorous content of the Ni-P UBMs. Therefore, an approach to suppress Ni-Sn-P formation is proposed