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Integrated Heat Spreader with Features to Limit Solder Thermal Interface Material Spread

IP.com Disclosure Number: IPCOM000074589D
Publication Date: 2005-Feb-23
Document File: 5 page(s) / 140K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an integrated heat spreader (IHS) with features that limit the flow of solder thermal interface material (TIM).

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Integrated Heat Spreader with Features to Limit Solder Thermal Interface Material Spread

Disclosed is a method for an integrated heat spreader (IHS) with features that limit the flow of solder thermal interface material (TIM).

Background

Excessive or uncontrolled compression of the package during package reflow, along with lid tilting and variations in pre-form placement and size, can lead to liquid solder being pushed beyond the die area (where it could short the surrounding capacitors). This is can be problematic for packages that have very large dies and many capacitors under the lid.  These factors can lead to molten solder being squeezed to one side of the die, where it beads up and breaks off.

Figure 1 shows a current IHS used in solder TIM applications has a flat cavity with a gold spot in the center. The size of the gold spot is larger than the silicon die. The gold spot serves as a wetting layer for the molten solder. The solder wets and sticks to the gold during reflow, however it does not wet the nickel plating on the IHS.

General Description

The disclosed method relies on surface tension forces to control solder TIM spread. Solder TIM in the molten form wets to the gold plating on the IHS, but not the nickel. This helps restrain the molten solder to the areas where there is gold plating. In addition, gold-plated troughs are added to catch the excess solder.  The ribs on the new IHS can soak up and hold excess solder similar to the ribs on a bubble wand (see Fig...