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Depopulated Ball/Land Grid Array Patterns on Components with Integrated Heat Spreaders

IP.com Disclosure Number: IPCOM000010332D
Publication Date: 2002-Nov-20
Document File: 3 page(s) / 66K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses “columns or rows” of solder spheres on area arrays to connect a component’s substrate to the distributing board. Benefits include eliminating solder joint cracks from high-risk locations.

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Depopulated Ball/Land Grid Array Patterns on Components with Integrated Heat Spreaders

Disclosed is a method that uses “columns or rows” of solder spheres on area arrays to connect a component’s substrate to the distributing board. Benefits include eliminating solder joint cracks from high-risk locations.

Background

Although thicker integrated heat spreaders provide better overall (system) thermal resistance, they are susceptible to joint fatigue failures due to high stress concentrations on the joints directly under the heat spreader lip shadow (see Figure 1). The increased stiffness of the spreader generates more movement/deformation (i.e. less relaxation from the IHS) of the organic substrate, and as a consequence the solder joints are highly deformed. This problem is more evident on heat spreaders with thickness greater than 1.5mm.

General Description

Currently, there are several types of ball grid array patterns on microelectronic packages (e.g. full grid arrays, fully populated arrays, peripheral or window arrays, etc.). Newly developed packages for high power devices use an integrated heat spreader to aid in thermal management. This heat spreader is normally made out of nickel-plated copper, with a thickness of 1 to 3 mm.

The disclosed method prevents solder joint failures by depopulating those high risk locations. If the solder spheres directly below the heat spreader shadow are not placed, no open failures are expected and the use of a thicker integrated heat...