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Method for a retention mechanism and clip for applying a high-force preload to a heatsink and electronic package on a PCB

IP.com Disclosure Number: IPCOM000074634D
Publication Date: 2005-Feb-23

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a retention mechanism and clip for applying a high-force preload to a heatsink and electronic package on a printed circuit board (PCB). Benefits include improved functionality, improved performance, improved thermal performance, and improved reliability.

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Method for a retention mechanism and clip for applying a high-force preload to a heatsink and electronic package on a PCB

Disclosed is a method for a retention mechanism and clip for applying a high-force preload to a heatsink and electronic package on a printed circuit board (PCB). Benefits include improved functionality, improved performance, improved thermal performance, and improved reliability.

Background

              Conventionally, a heatsink may be wave-soldered onto a PCB. A very low compressive preload is applied at the thermal bond-line. Thermal performance for small-die packages is generally limited due to the use of thermal interface materials (TIMs). They are prone to large variations in thermal performance due to variations in the balancing of the heatsink on small-die packages during the wave-soldering process (final assembly). The assembly is prone to severe thermal degradation as a result of temperature cycling conditions in the end-user environment.

              Typically, the heatsink component must be larger (thicker base and more extended surface area) to compensate for low thermal bond-line performance. The assembly is

prone to preload degradation over time via stress relaxation in solder joints. The conventional technology is not capable of successfully cooling electronics that must dissipate >20 watts.

              The heatsink may also conventionally be held onto the PCB via some type of flexural or torsional spring clip and solder-joint anchors. This arrangement provides low shock resistance due to the low static tensile force limit of the anchors, which tend to pull out of solder over time. Low shock resistance may also result from the low stiffness of the flexural or torsional spring clip. As a result, the heatsink tends to come off of bare-die packages during shock, which potentially leads to die cracking-related electrical failures. To counter this problem, the PCB manufacturer must integrate the anchor component at their factory, limiting the options available to the system integrator down-stream.

General description

              The disclosed method is a retention mechanism and clip for applying a high-force preload to a heatsink and electronic package on a PCB. The key elements of the disclosed method include:

•             Stirrup with a large open loop at its top to engage with the clip component or, alternatively, that directly interfaces with retention features incorporated into the heatsink design

•             Clip (optional) with a right-hand notch and a left-hand notch for accepting the open loop in the stirrup

•             Heatsink with an optional central channel and optional features to interface with the clip

•             PCB with holes that interface with the hook structure of the stirrups

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to ergonomically applying a high static compressive bond-line pressure to promote better thermal conducti...