Design007 Magazine


Issue link:

Contents of this Issue


Page 51 of 75

52 The PCB Design Magazine • September 2017 Last month I expressed what I hoped would prove a good starting point for my series of articles on the all-important subject of ther- mal management. This was a five-point guide, which I compiled based on the many questions that our customer support teams field every day on the telephone, at exhibitions and when vis- iting customers' premises. This month, I'd like to progress matters further and concentrate on some of the problems you are likely to encoun- ter when applying a thermal interface material, and how to select materials that are appropri- ate for your electronic assembly and its operat- ing conditions. I'll also be looking a little more closely at bond line thickness and its effects on performance, as well as the alternatives to non- curing thermal pastes. But let's start with a prob- lem that, I'm afraid, most of you will encoun- ter at some stage in your product development work: pump-out. Pump-out can occur when a device—an in- sulated-gate bipolar transistor (IGBT), for exam- ple—is subject to temperature changes resulting in relative motion between the conductor and its heatsink between which a non-curing ther- mal paste has been applied. This motion can cause such pastes to be squeezed or pumped out from the interface gap, reducing the thermal transfer performance. To tackle issues with pump-out, it is first im- portant to understand the conditions and ma- terials involved. Temperature extremes and rate of change of temperature are important factors that will determine the choice of thermal in- terface material; for example, if operating tem- peratures are likely to range between -50°C and 200°C, a silicone-based thermal paste would be the preferred option. In addition to these temperature consid- erations, the materials being used may affect the interface material, particularly with re- gards to the spacing between the device and its heatsink—otherwise known as the bond line thickness. by Jade Bridges ELECTROLUBE Thermal Management: Problems and Solutions SENSIBLE DESIGN

Articles in this issue

Archives of this issue

view archives of Design007 Magazine - PCBD-Sept2017