Three questions an engineer should ask prior to using thermal epoxy for their heat sinks

We’ve seen a big uptick in use of epoxy by our customers here at ATS. To our engineers that is alarming. While thermal epoxy initially appears to be a good solution for attaching a heat sink to a chip, accomplishing both the attachment and the thermal interface material in one “quick” glue application design engineers and manufacturing engineers should stop and ask themselves the following three questions before deciding to move ahead.

(1) Does it have to be glued?
Many times glue looks like the easy answer since its generally cost-effective and can be easily applied. But the question “does it have to be clued” really stops you short to make you examine potential alternatives. Don’t forget, thermal epoxy can expire and lose it’s properties.

(2) Is the perceived cost/time savings in assembly worth the actual cost of rework?
Many times thermal epoxy is a quick default choice, “just glue it on” has the sound of a quick solution that should work in average applications.  But that’s not the case.While it looks easy, thermal epoxy requires consistent application to the semiconductor the heat sink is being glues onto. To get that consistent application can require some training (a “soft” cost). But the real caution is the rework. No one “expects” reworks but reworking a company’s computer boards is reality. And with thermal epoxy being used for your heat sinks the rework requires either hot air guns (an additional expense) or destruction of the components under the heat sink. The cost of the rework may exceed the cost savings of using epoxy. Don’t forget the cost of  using thermal epoxy for your heat sinks includes training on how to use epoxy, special equipment to remove epoxied heat sinks and the cost of the material (which has a shelf life and many times must be refrigerated).

(3) Is epoxy being chosen to secure your heatsink?
While the epoxy bond is secure, it’s not foolproof. In fact ATS has seen many epoxied heat sinks that fell off during shock and vibe testing. What generally happens is that heat will weaken the epoxy mechanical bond then, when a strong shock or other mechanical stress is applied, the weakened bond with break, leaving your heat sink in free fall and your semiconductors overheating.

Want some alternatives? Check out our blog post series,

How to choose a heat sink attachment method to secure your heat sink and for optimal heat transfer Part 1

How to choose a heat sink attachment method to secure your heat sink and for optimal heat transfer Part 2

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