Authored By:
Jim Hisert, Brandon Judd
Indium Corporation
Summary
Package-on-package (PoP) technology allows two or more electronic components to be stacked vertically, which saves space and allows our portable gadgets to continue getting smaller year after year. A relatively new form of solder paste called "PoP Paste" has been developed specifically for this application.
There are fundamental differences between PoP pastes and the traditional solder pastes, which are designed for printing applications. This paper will highlight the differences between these solder pastes and talk about the characteristics needed by PoP pastes to increase transfer efficiency, eliminate head-in-pillow defects, and provide excellent solder wetting. If these three criteria are met, solder joint reliability will follow
Conclusions
With the miniaturization of today's electronic devices and the increasing complexity of their features, the need for PoP components is increasing significantly. Although it may seem like a simple solution to just use the standard SMT solder paste that you have in-house for your upcoming PoP applications, these products are not optimal for this type of process. As our testing has shown, modern PoP solder paste materials are much better suited for the dipping process used for PoP components. Formulation, particle size, and metal loading are all key factors in the design of a PoP-specific solder paste.
The time spent evaluating these new products is well spent. Electrical opens on your boards when using standard SMT materials or outdated dipping pastes can result in costly and time-consuming rework down the road. With the proper material and process, insufficient solder transfer and head-in-pillow defects can be a thing of the past.
Initially Published in the SMTA Proceedings
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