Ball impact responses of Sn-1Ag-0.5Cu solder joints at different temperatures and surface finishes

The purpose of this paper is to measure and analyze the Sn-1Ag-0.5Cu solder joints under high speed ball impact test (BIT) conditions. In this study, the ball impact test was conducted at impact velocity of 300 mm/s on package-level solder joints with 0.3 mm ball diameter, bonded individually on substrate pads of Ni/Au, OSP and Ni/Pd/Au surface finishes at elevated temperature of 25, 50, 75, 100 and 125 °C, respectively. The experimental results show that Ni/Pd/Au surface finish at room temperature has higher intermetallic compound (IMC) strength performance than Ni/Au and OSP. These three different substrate surface finishes, however, tend to have quite similar IMC strength performance at elevated operation temperature. The board-level drop test reliability of TFBGA 14 mm × 14 mm 409 L for these surface finishes were also performed at room temperature. The trends of BIT results are in good agreement to board-level drop test reliability. A three-dimensional finite element analysis (FEA) model was established to analyze the transient structural responses in the solder joint for determining the maximum impact toughness capacity. The effects of temperature on solder joint material yield stress and IMC strength on the impact characteristics were investigated.