PC card packaging technology with BGA and build up PWB

摘要

The PC architecture is increasingly used for both industry and consumer products. And also the PC architecture may become the pervasive device because of standard architecture, high performance, low cost, and more integrated.A credit card size, the smallest PC mother board supporting EASI(embedded all-in one system interface) have been developed as the solutions providing the PC architecture.Key technologies to develop OKI Micro Card PC were resin coated Ball Grid Array(BGA) packaging with single ppm soldering technology and build-up multilayered PWB(Printed wiring board).New packages were required to be developed because common LSI packages could not meet a card size PC. Then two BGA packages having full matrix solder bumps of 361 and 238 wifflin 29×29mm{sup}2 and 21×25mm{sup}2 substrates of BT resin were developed. One BGA package is CPU single chip module, and another BGA is PC/AT chip set composed of three bare chips, multichip module. Minimum line width and space of BGA substrate were 60μm. Build-up multilayered PWB was adopted as a means to submit the high density packaging with modest packaging cost Using via posts having 125 microns, this PWB can accommodate all of the wiring function of card PC in 8 layers and 0.7 mm thickness. Surface finish of solder pads are copper plated with pre flux coating. Establishingan optimum soldering conditions including pad/mask size and reflow profile, single ppm soldering quality were assured in mass production line.