As power levels for board components have risen, thermal engineers have been forced to design larger and more innovative heat sinks than ever before. Along with the thermal challenge has come the mechanical challenge of attaching these heat sinks to the components in a reliable fashion.
One of the most popular methods uses some form of clip. These are low in price and easily applied. Smart engineering has led to clip systems that provide strong, even pressure well beyond the working life of the component. They hold their heat sinks tight even when dropped or shocked, but they can be unclipped manually whenever it’s necessary.
Clips that attach directly to the component provide an advantage over other clip types, (e.g. z-clips) in that no holes are required in the PWB. The ATS maxiGRIP is an example of such an attachment. maxiGRIP uses a plastic frame clip that attaches directly to the component and provides a mounting platform for a custom spring clip (Figure 5).
The frame clip is installed, using a special tool which expands all four sides of the clip simultaneously, allowing the clip to be placed directly over the component package (A keep out area is usually required). Once released, tabs on each side engage and secure the clip to the component, creating a secure mounting platform for the spring clip. The spring clip, which is designed to provide a very precise load, is then installed to hold the heat sink in place, maintaining continuous pressure at the heat sink component interface. The maxiGRIP assembly has a big advantage over other heat sink attachment methods in that it allows for the use of high performance phase change interface materials.
Extensive FEA and shock and vibration testing of the maxiGRIP assembly have been done to provide a carefully engineered heat sink attachment solution with a high-level of reliability.