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Thermal Loading Land Grid Array with Heat Sink Posts to Stiffen the PCB

IP.com Disclosure Number: IPCOM000023836D
Publication Date: 2004-Mar-31
Document File: 5 page(s) / 489K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a heat sink with attached posts to stiffen a PCB under the CPU and socket. Benefits include eliminating the need for a backing plate under the PCB.

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Thermal Loading Land Grid Array with Heat Sink Posts to Stiffen the PCB

Disclosed is a method that uses a heat sink with attached posts to stiffen a PCB under the CPU and socket. Benefits include eliminating the need for a backing plate under the PCB.

Background

Land grid array (LGA) sockets require an activation force on the contacts to create electrical contact and minimize electrical resistance. It is important to reduce the flex in the PCB under the socket. Currently, direct socket loading (DSL) requires a load plate, stiffener plate, and a lever to generate the required load (see Figures 1 and 2); these components are made from stainless steel, impacting the overall cost of the process.

General Description

In the disclosed method, load is generated directly through a thermal device (i.e. heat sink) on the processor package in order to activate the contacts. The required activation force for the LGA contacts can range from 60 to 125 pounds of force, and the load must be maintained for a 7 year design life of the processor. The disclosed method is shown in Figures 3, 4, and 5.

The socket is made of LCP material and copper alloy-based contacts, which are stitched in the housing. Solder balls are attached to the contact paddle to allow surface mounting of the socket to the PCB. The heat sink is designed with specially shaped posts; these posts, in conjunction with an attachment device, are secured through the PCB to prevent flex, twist, and rotation.

The following is the manufacturing sequence for the...