The Role of Pd in Sn-Ag-Cu Solder Interconnect Mechanical Shock Performance

The impact of microstructure evolution, localized recrystallization and board thickness on Sn-Ag-Cu interconnect board level shock performance

“…As already explained in an earlier publication, the bulk solder can transform into a multi grained structure from a single/dual grain structure during shock test. [9,10] With this transformation, the shock induced strain can be absorbed and result in an improved shock performance. A similar single to multi grain transformation is also observed in the isothermally aged samples after shock.…”

“…Mitigation of crack initiation or crack propagation can be achieved if the shock energy is consumed or absorbed in the interconnection system, in other words by the solder joint bulk solder material. [9,10] Figure 1 shows cross section polarized light microstructures of the outermost 5 joints on each side of the outside edge of the shock-tested samples. Since the pad design of these samples were NSMD (nonsolder mask defined), the crack locations were typically at the upper interface or in the laminate below the board side copper pad, as indicated by an outlined box in the figure.…”

“…The test vehicle was designed to provide three different shock and strain conditions and the shock and strain response was explained in detail in earlier publications. [9,10] A fixed input shock of 1500G with 0.5 millisecond half-sine pulse duration at the table was imposed, which is based on the JEDEC22-B111 standard. [11] The connections between the component daisy chains were continuously monitored and a 20% increase in resistance during the shock test, compared to the initial resistivity value, was considered to be a failure.…”