Apalis Carrier Board Design Guide - Toradex

Apalis Carrier Board Design GuideFigure 69: Mounted Heat SinkIn order to guarantee good thermal conductivity between SoC and the heat sink required foreffective heat dissipation, pressure needs to be applied to the thermal interface material betweenSoC and spreader. As the Apalis module PCB is only 1.2mm thick, adding pressure in the middle ofthe board would cause undesired bending and flex, which could damage the module. To preventsuch bending, every Apalis module features a pad on the bottom side of the module. This padallows the addition of a support standoff between module and carrier board.If a cooling system is used that applies force to the center area of the module PCB, it is stronglyrecommended that the additional spacer be added under the module.Spacer addedunder SoCFigure 70: PCB bending problemThe figure below shows a cross-section trough of a heat sink, mounted on an Apalis module. Theoverall height from carrier board surface to the top of the heat sink is 14mm without a fan. Theadditional spacer under the center of the module needs to have a height of 3mm.SoCHeats SinkSpacer 3mm14mmSpacer 8mmSpacer 3mmFigure 71: Stacking height of heat sinkCarrier BoardToradex AG l Altsagenstrasse 5 l 6048 Horw l Switzerland l +41 41 500 48 00 l www.toradex.com l info@toradex.com Page | 71