Heat-dissipating chip carrier substrates

摘要

A substrate for a leadless chip carrier (50) is formed on a rigid multi-layer circuit board (1). Metallic layers (4 and 5) are secured to opposite sides (2 and 3) of the board, and on top of these are mounted respective layers (10 and 11) of elastomeric material. An electrically-conductive layer (20) is laid on top of the upper elastomeric layer (10) and this is formed in a pattern of contact elements (70) and tracks which are interconnected to other layers of the substrate by plated-through holes. The chip carrier (50) is supported on a heat transfer pad (40) of copper which rests on the upper metallic layer (4) and is secured thereto by a layer of solder (46). The pad (40) may have an integral pillar (42) that extends through a copper-plated aperture (43) in the substrate to a heat-dissipating pad on the surface of the lower elastomeric layer. Contact pads (51) on the chip carrier (50) are soldered to the contact elements (70), the height of the heat-transfer pad (40) being such as to separate them and ensure a thick solder joint (53).