Increased use of PoP technology is driven by continued product miniaturization. Smaller products require increased printed circuit board assembly (PCBA) density. Stacking memory is one way to achieve both goals for enhanced functionality and greater packaging density. While PoP was originally adopted by consumer electronics and telecommunications designers, even the medical industry is now designing it into new applications. 
 

That said, PoP technology is not without manufacturing challenges. While the ball grid array (BGA) packages used are well understood, a poor quality process carries a far higher cost in terms of rework or scrap, since two or more BGAs are affected.

Placement requirements and process technology are not significantly different from individual BGAs. Following screen printing, the first component is placed. Then, the second component is flux dipped and placed. In some cases, up to two or more BGAs may be stacked. In many EMS facilities, the only significant line modification is purchasing a flux dip module for placement machines. Thermal profiling during reflow is the same as boards of similar thermal mass.

However, quality needs to be carefully monitored. Any distortion in the bottom component will be reflected in the components above it. Another concern can be excessive heat in convection reflow processes when lead-free components are used. Because the top component is flux dipped, there is no additional solder volume.