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Stepped Nonlinear Clips and Retention Mechanisms

IP.com Disclosure Number: IPCOM000004811D
Publication Date: 2001-Jun-11
Document File: 5 page(s) / 79K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a design for stepped nonlinear clips and retention mechanisms (RMs). Benefits include a high capacity to withstand board-level shock and a wide range of tolerance stack-ups yet able to be hand assembled.

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Stepped Nonlinear Clips and Retention Mechanisms

Disclosed is a design for stepped nonlinear clips and retention mechanisms (RMs). Benefits include a high capacity to withstand board-level shock and a wide range of tolerance stack-ups yet able to be hand assembled.

The disclosed design includes two metal clips and two plastic RMs that constrain the heavy heatsinks required for high thermal output integrated circuits (ICs). The ICs are assembled onto electronic packages that are connected to an electronic board though a socket connector. The heatsink is placed on top of the electronic package with thermal interface material (TIM) between the electronic package and the heatsink. The heatsinks required to cool the IC have a high mass (~1 lb) and must be retained on the electronic package and board. The full assembly is required to pass 50Gs of shock to satisfy environmental conditions that simulate shipping and handling. The clips and retention mechanisms are devices that retain the heatsink, making the connection between the heat sink and board. Figure 1 shows the full assembly. Figure 2 shows the exploded view of the full assembly.

A typical failure mode that occurs during 50-G shock when a heavy heat sink is required is that the electronic package pulls out of the socket connector causing electrical opens and total failure. Damage is results from the TIM acting as glue between the heatsink and electrical package. Any heatsink movement is reflected in the package. Under 50Gs of shock, the heatsink receives approximately 100 lbf of shock load. The retention ability of the socket is at its maximum 20 lbf. Therefore, a simple preload solution must apply 80 lbf to ensure that failure does not occur. However, 80 lbf cannot conventionally be achieved with hand-assembled clips. Prevention of the failure mode eliminates the movement of the heatsink. The disclosed design solves the pullout problem while utilizing a hand-assembled clip.

The assembly process for the disclosed design is as follows. First, the two RMs are mounted to the electronic board or to the chassis. The heatsink is then placed between the two RMs. The clips are assembled in a series of steps (see Figure 3). The lower portion of the clip's center window is placed over the center RM tab. The clip is slid into place so the higher portion of the clip's center window is centered over the RM's center tab. The two clip arms are placed in order over the RM's end tabs.

The clips are manufactured by stamping a thin sheet of stainless steel to the flat outline. Then the outlines are bent to the required shape through a progressive die. The RMs are injection-molded plastic parts.

The only conventional solution to the pullout problem utilizes screw fasteners on the heat sink, which must be assembled with a tool that leads to a higher assembly time and cost. The disclosed design provides the following benefits:

The design includes the only hand-assembled clip and RM solution for socketed packages that solves...