A study of lead-free BGA backward compatibility through solderability testing at component level

A study was conducted to assess the backward compatibility of two different lead-free BGA components using Jedec Solderability testing method (JESD22-B102D). The test was conducted at component level. The two components tested were 29×29mm Thermally Enhanced PBGA (TePBGA-II) and 35×35mm Tape BGA (TBGA) with SAC387 and Sn3.5Ag solder balls. Four units from each of the two component types were used to prepare the profiling pallet. These pallets were used to obtain a Low Solderability Profile and a High Solderability Profile to encompass the low and high end of the reflow profile according to Jedec SnPb Solderability Test Conditions. The sample size used in the final solderability testing study was 15 units for each component and solder ball alloy type. Prior to solderability reflow, all the 15 units per cell were subjected to 8 hrs of steamaging and followed by 1hr baking at 100 degree C. This is followed by solderability testing which includes SnPb paste printing onto ceramic plates using stencil with the component´s arrays. Next, components were place on the solder paste array using Fine Placer machine. And the components were reflowed in the Low and High SnPb Solderability Profile which were obtained earlier for each of the two component types. Finally, components will be detached from ceramic plate by force. Inspection will be done on the solder balls on the component as well as on the ceramic plate. The passing criteria are based on Jedec Solderability standard which includes no satellite balls or paste remaining on the ceramic plate after reflow. The solderability testing result showed that all the two BGA component types passed without any solderability failure with both the Low and High SnPb Solderability Profiles. This result showed that backward compatibility is NOT an issue for lead-free BGA components with SAC387 and Sn3.5Ag solder balls from solderability point of view.