SMT Prototype PCB Assembly Techniques of PoP

When it comes to surface mount technology (SMT) modes of PoP, two types of technologies are available: pre-stacked PoP and on-board stacking PoP.

In pre-stacked PoP technique, manufacturers will stack top package and bottom package, carry out soldering to make the combination be a component that is called pre-stacked device, then attach the combined component to printed circuit board (PCB) surface and implement reflow soldering.

In on-board stacking PoP technique, manufacturers will sequently stack bottom package and top package on circuit board. First, they will mount bottom package on circuit board prototype, then mount top package on bottom package after dipping into flux or solder paste. Next, conduct a reflow soldering on the stacking package.

Take a double-side SMT assembly as an example, steps of on-board stacking PoP assembly include:

• Non-PoP side component assembly (printing, mounting, reflow soldering and inspection);
• Solder paste printing on PoP side;
• Bottom package and other devices mounting;
• Top package devices dipping flux or solder paste;
• Top package mounting;
• Reflow soldering;
• Inspection (X-ray or AOI).

Compared with pre-stacked PoP SMT prototype PCB assembly technique, on-board stacking PoP contains two more steps: top package's flux or solder paste dipping and top component mounting.

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