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Thermally Enhanced Module With Thermal C4S To Handle Non-Uniform Chip Heat Flux

IP.com Disclosure Number: IPCOM000223138D
Publication Date: 2012-Nov-05
Document File: 2 page(s) / 82K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method is disclosed to utilize thermal C-4 (Controlled Collapse Chip Connection) pads to create customized heat flow paths from the chip to the module cover (cap) while avoiding thermal stresses due to thermal coefficient of expansion mismatch.

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Thermally Enhanced Module With Thermal C 4S To Handle Non-Uniform Chip Heat Flux

In order to accommodate increased power dissipation in integrated circuit chips it is desirable to provide a thermal conduction heat flow path directly from the back of the chip to the underside of the module cap. Although thermal paste has been used to do this, the heat transfer effectiveness of the path is limited by the relatively low thermal conductivity of the paste. From a thermal conductivity viewpoint it would be desirable to provide a metallurgical joint between the chip and cap by using a low melting point solder. However, the introduction of a continuous solder joint between chip and cap results in excessive stress due to the different temperature coefficients of expansion of the chip, solder, and cap materials.

Disclosed is a connection means for avoiding thermal stress at a metallurgical

joint between a chip and its cap. In this embodiment, the backside of the chip and the underside of the cap are interconnected utilizing a pattern of thermal C-4 pads as shown in the Figure. Arrays of C-4 pads are screened onto the backside of the chip or onto the module cap using standard techniques. Ideally, the thermal C-4s would be similar to solder columns typically used to connect modules to cards. Individual solder columns with a relatively large aspect ratio (length to width of column) will act as small beams, exhibiting good compression, tension, and moment properties. A reduct...