Importance

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Abstract

A multi-layer flexible circuit board has thicker regions to which surface-mount-technology (SMT) components (such as flip chips and QFPs) and pin-in-hole (PIH) components are mounted on both sides and which contains conductive through vias between wiring layers. After the SMT components have been mounted to the first side, a screening fixture with a support surface that has cavities conforming the components on the first side, is used to screen solder paste to the other side of the board. The thicker regions are surrounded by thinner regions of the board with fewer wiring layers and preferably fewer or thinner dielectric layers, and which can be bent along a line without bending the thicker regions. A common heat spreader plate with cavities or holes for multiple components is laminated to the thicker regions on one side of the board. The thicker regions have windows in which wire-bond chips are mounted to the heat spreader and the chips are wirebonded to the other side of the board. A thermally conductive adhesive or grease connects between the components and the bottoms of the cavities. Two heat sink plates are bolted together and along with other such heat sink plates are bolted to an enclosure frame to improve thermal performance.

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First Claim