Heat Spreader - Emerson COM Express Carrier Design Manual

20.2 Heat Spreader

An important factor for each system integration is the thermal design. The heat spreader acts as a
thermal coupling device to the module. Usually It is a 3 mm-thick aluminum plate. Figure 35 shows the
heat spreader used on the Emerson COMX-ATOM-420.
The heat spreader is thermally coupled to the CPU via a thermal gap filler. On some modules, it may
also be thermally coupled to other heat generating components with the use of additional thermal gap
fillers.
Although the heat spreader is the thermal interface where most of the heat generated by the module is
dissipated, it is not to be considered as a heat sink. It has been designed to be used as a thermal
interface between the module and the application-specific thermal solution. The application-specific
thermal solution may use heat sinks with fans and/or heat pipes, which can be attached to the heat
spreader. Some thermal solutions may also require that the heat spreader is attached directly to the
systems chassis therefore using the whole chassis as a heat dissipater.
The main mechanical mounting solutions for systems based on COM Express modules have proven to
be the top-mounting and bottom-mounting solutions. The decision as to which solution will be used is
determined by the mechanical construction and the cooling solution of the customer's system. There
are two variants of the heat spreader, one for each mounting possibility. One version has threaded
standoffs and the other has non-threaded standoffs (bore hole). The following sections describe these
two common mounting possibilities and the additional components (standoffs, screws, etc.) that are
necessary to implement the respective solution.
Figure 35 Heat Spreader Used on COMX-ATOM-420 COM Express Module
Page 90 of 103 COM Express Carrier Type 2
Design Guide