Design for a force-balanced thermal plate for cooling semiconductor devices
Disclosed is a design for a force-balanced thermal plate for cooling semiconductor devices. Benefits include improved thermal performance and improved flexibility through looser tolerances on the mechanical components while maintaining mechanical integrity.
Description
The disclosed design includes a thermal plate contacts the device using spring features that adjust for device height variances. As the springs are deflected during attachment, a compression force is induced on the thermal interface material (TIM), improving its thermal performance. The compression force results from the following:
• Magnitude of deflection
• Material properties of the spring features
• Number of spring features
• Mechanical design of the spring features
Figure 1 is an exploded drawing of the full assembly. The thermal plate is item 5. The four spring features are depicted on the top of the plate.
Conventional designs include the attachment of a thermal cooling solution to the PCB near the device to be cooled. The thermal solution standoffs in this case are sized so that the solution is positioned above the device to be cooled. A small thermal bond line (BLT) gap is filled with thermal grease, elastomer, or other thermal-conductive material. However, the standoffs and the device have height variances (tolerances) that result in a variance in the BLT. If the variances are extensive enough, the BLT is too great or too thin to yield adequate thermal performance or mechanical fit with TIMs. Figure 2 illustrates a conventional assembly with a BLT variance of 0.22 mm that requires an elastomer 3-mm thick for mechanical fit, which is 6 times thicker than conventional thermal requirements allow.
Benefits
The disclosed design eliminates the attempt to maintain a BLT with fixed-height components such as standoffs. Instead, the thermal solution moves to absorb the component height variance. Mechanical integrity and adequate pressure on the thermal interface material are maintained to yield good thermal performance. The spring features in the thermal solution permit looser tolerances on the mechanical components. Figure 3 illustrates the new assembly with the plate resting on the compressed elastomer and spring features to absorb height variances. The schematic is included in Figure 4.
Fig. 1
Fig. 2
Fig. 3
Fig. 4
Disclosed anonymously
