Two big names in electronics assembly (Vern Solberg and Phil Damberg) recently wrote an article for Circuits Assembly Magazine regarding "PoP Assembly Process Fundamentals". The article goes through the background of package-on-package, the components, the PoP solder paste dipping process, reflow, and post-assembly solder evaluation. Most authors would stop there, but as a bonus, Vern and Phil discuss reinforcement, warpage, future trends, and future package technologies.
Now, I like to think I generally have my finger on the pulse of who is using our PoP solder pastes, but this one completely slipped past me. I was happily surprised to read that they referenced Indium Corporation PoP solder paste - cool! When I was learning about semiconductor packaging years ago, I learned a lot from Vern's tech papers. This was personally rewarding to be mentioned by an industry leader like him. If you're reading this - thanks Vern and Phil!