US 5,926,371 A · Heat transfer apparatus which accommodates elevational disparity across an upper surface of a surface-mounted semiconductor device

Abstract

A heat transfer apparatus is presented accommodating elevational disparity of an upper surface of a semiconductor device with respect to the component side of a PCB without adversely affecting system reliability. The heat transfer apparatus includes a thermally conductive cap structure positioned between the semiconductor device and an ambient and thermally coupled to the semiconductor device. One embodiment includes one or more spacers which maintain a space between the cap structure and the semiconductor device. A chip mounted to the substrate of a ceramic BGA package is mechanically isolated from the cap structure by the spacers, preventing chip damage due to shock and vibration. A backing plate on a side of the PCB opposite the semiconductor device provides PCB structural support and additional heat transfer. Several fasteners attach the backing plate to the cap structure. A portion of the fasteners exert a force which urges the cap structure toward the semiconductor device, while the remainder of the fasteners fix the relative positions of the backing plate and the cap structure. Fixing the relative positions of the backing plate and the cap structure reduces creep problems and promotes stress relief in viscoplastic elements. A first thermal interface layer between the cap structure and the semiconductor device achieves an acceptably low thermal resistance value under a relatively small amount of pressure. The spacers are omitted in an alternate embodiment wherein the first thermal interface layer has a uniform thickness and a consistency which permits the thickness to be maintained during installation.

Claims34

Dependent claims

A heat transfer apparatus transferring heat energy from a chip mounted to a substrate, the heat transfer apparatus comprising:

a thermally conductive cap structure;
at least one spacer engaged between respective surfaces of the cap structure and a region of the substrate laterally outside a perimeter of the chip such that a space is formed between the cap structure and the chip;
wherein a force is used to bias the cap structure toward the chip;
and
wherein the position of the cap structure relative to the chip is fixed such that the space formed between the cap structure and the chip is maintained.

2 more elements

A heat transfer apparatus transferring heat energy from a semiconductor device to an ambient, wherein the semiconductor device comprises an upper surface having a chip attached thereto, and wherein the semiconductor device is mounted upon a component side of a printed circuit board (PCB), the heat transfer apparatus comprising:

a thermally conductive cap structure, wherein the cap structure is interposed between the semiconductor device and the ambient, and wherein the cap structure is in thermal communication with the semiconductor device;
at least one spacer, wherein the at least one spacer is interposed between and in contact with a portion of the upper surface of the semiconductor device surrounding the chip and the cap structure such that a space is formed between the upper surface of the chip and the cap structure;
a backing plate positioned on a side of the PCB opposite the component side and at a location opposite that of the semiconductor device;
a plurality of fasteners for attaching the backing plate to the cap structure;
and
wherein the at least one spacer is spherical in shape and comprises a thermally conductive material.

3 more elements

A heat transfer apparatus transferring heat energy from a semiconductor device to an ambient, wherein the semiconductor device comprises an upper surface, and wherein the semiconductor device is mounted upon a component side of a printed circuit board (PCB), the heat transfer apparatus comprising:

a thermally conductive cap structure comprising a bottom surface having a cavity and a circumferential lip surrounding the cavity, and wherein the cavity comprises an upper wall, and wherein the semiconductor device resides within the cavity and the cap structure is interposed between the semiconductor device and the ambient;
at least one spacer interposed between and in contact with the upper surface of the semiconductor device and the upper wall of the cavity such that a space is formed between the upper surface of the semiconductor device and the upper wall of the cavity;
a backing plate positioned on a side of the PCB opposite the component side and at a location opposite that of the semiconductor device;
a plurality of fasteners for attaching the backing plate to the cap structure;
a first thermal interface layer interposed between the semiconductor device and the cap structure and thermally couples the cap structure to the semiconductor device;
a second thermal interface layer interposed between the backing plate and the PCB and thermally couples the backing plate to the PCB;
and
a seal interposed between the lip of the cap structure and the PCB.

5 more elements

Dependencies are inferred from the claim text.

Heat transfer apparatus which accommodates elevational disparity across an upper surface of a surface-mounted semiconductor device

Life of this patent

Heat transfer apparatus which accommodates elevational disparity across an upper surface of a surface-mounted semiconductor device

Life of this patent

Abstract

Claims34