Lead-Free BiSnAg Soldering Process for Voidless Semiconductor Packaging

The rapid growth in the global market for semiconductor power electronics has intensified the requirement for better reliability quality at the solder interconnect that demands small or zero solder void size, as well as the search for lead-free solders due to environmental and health concerns. BiSn-based solder has been one popular choice among lead-free solders to provide low-cost solutions for more compact electronic packages. In this work, BiSnAg solder alloy was subjected to the standard reflow, the vacuum reflow, and the pressure cure to evaluate the effectiveness on the solder void size reduction or elimination toward achieving voidless packaging. Pressure cure is shown to be an effective technique to minimize the solder void size below 1% consistently and considerably improve the removal rate of solder void in BiSnAg solder during semiconductor die packaging. More importantly, pressure cure can effectively remove all the hollow solder voids except for the solder voids containing solid deposits originating from the trapped solder flux residues, paving a critical way forward to achieve zero solder void in the electronics packaging.