Browse Prior Art Database

Thermally-Activated IHS Attachment

IP.com Disclosure Number: IPCOM000008966D
Publication Date: 2002-Jul-26
Document File: 3 page(s) / 47K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses heat to attach an integrated heat spreader (IHS) to a package while maintaining sufficient pressure between the IHS and the die. Benefits include lower cost and the ability to attach the IHS without clips or special trays.

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Thermally-Activated IHS Attachment

Disclosed is a method that uses heat to attach an integrated heat spreader (IHS) to a package  while maintaining sufficient pressure between the IHS and the die. Benefits include lower cost and the ability to attach the IHS without clips or special trays. 

Background

Currently, clips are used to press down on the IHS during the attach process (see Figure 3). Installing and removing these clips adds cost and throughput time to the process.

General Description

In the disclosed method, the spring member (see Figure 2a) shrinks 0.078mm during heating (i.e. thermal activation step) to provide 6 lbf. on the die. This amount of shrinkage is only ~10% given that the distance from the top of the substrate to the top of the die is 0.8mm (33 mils). Either the shape memory alloy spring member (see Figure 2b) or the volatile component spring member (see Figure 2c) shrinks at least 10% during thermal activation. These enhanced contraction features are needed in the spring member, because normal contraction of a pure polymer structure (CTE=60 ppm/oC) can only provide about 1% contraction during a temperature reduction of 200oC.

Figure 2a shows the spring member pre-attached to an integrated heat spreader (IHS). The thermal interface material (TIM) is also pre-attached to the IHS. After placement onto the package, the whole assembly is heated. During this thermal activation step, the spring member first bonds to the substrate—due to an epoxy coating—then the...