We have developed, tested and used advanced surface mounting technologies
POP assembly consists of two or more fine-pitch ball grid arrays (BGAs) stacked one atop another. In a two-piece assembly, the bottom package is usually a high-density logic device, while the top package is a high-capacity memory device. Both devices can contain more than one die. To accommodate the upper package, a thin layer of mold compound is applied to the center of the lower package, just to cover the die and wire bonds. Solder balls on the bottom of the upper package connect with I/O pads on the top of the lower package.
POP assemblies are produced using the standard surface-mount process-with an extra hitch. The BGAs are fed from tape or trays. First, solder paste for the lower BGA is deposited on the board with a stencil printer, and the BGA is placed onto the board. Next, the second BGA is picked up and-here’s the hitch-dipped into a film of specially formulated “tacky” flux or solder paste just far enough to wet the balls. The second BGA is then placed atop the first one, and the entire board is reflowed as normal, preferably in a convection oven with a nitrogen atmosphere.
Microwave boards with metal base
Metal core PCB (MCPCB) is designed to allot the heat from some extremely heating elements of electronic devices, where typical thick copper foil and cooler solutions won’t give the desired effect.