THB reliability research for fine pitch substrate

With plating bar pitch becoming finer, the risk of ion migration on package surface under temperature humidity bias (THB) tests will be raised. In our research on fine pitch products with operating voltages of 1.5 V, 1.8 V and 3.3 V, the effects of plating bar spacing and layout that may affect ion migration on the package surface in THB tests have been studied. The critical substrate plating bar spacing and bias values that cause ion migration have been determined. The effects of different PSR (green PSR and non-green PSR) on the ion migration phenomenon have also been evaluated. Static electric field simulations have been done to help analyze the effects of different plating bar layouts. A substrate design rule for fine pitch products has been established for improving THB reliability.