Thermal Gels or Gap Filler Pads? Top 6 Things You Should Know

Thermal interface materials are used to eliminate air gaps or voids from adjoining rough or un-even mating surfaces. Because the thermal interface material has a greater thermal conductivity than the air it replaces, the resistance across the joint decreases and the component junction temperature will be reduced.

Two principal “gap filler” thermal interface materials prevalent on the market today are thermal gels – also known as dispensable gap fillers – and gap filler pads.

So, which one should you select for your application? Here are the top 6 things you need to know.

1. Conformability

Both thermal gels and thermal gap filler pads are highly conformable, but the maximum configurability of a gap pad is less than that of a gel due to its solid structure. Dispensable gels provide maximum conformability because they can be dispensed in near-infinite shapes and patterns.

2. Automation 

Both thermal gels and gap filler pads offer application via automation, but thermal gels get a significant advantage here because dispensing systems are quite versatile. While pad placement can be automated to an extent, the equipment and fixturing required to do so is typically quite specialized and may not be readily adapted from one job to the next.

3. Cost

When it comes to cost, thermal gap filler pads require less up-front capital because there is no dispensing equipment to invest in. However, our experience with multiple applications suggests that about 5,000 parts per year is the threshold where it becomes more economical to use thermal gels and an automated dispensing system versus pads that are manually applied for the same application.

4. Precision

Precision and accuracy are important, and the edge might go towards gap filler pads in this instance. Pads can be cut to the exact shape of your part, whereas the thermal gel takes the shape of how it spreads out once it is compressed. But as usual, the specific application will drive the degree of precision required, as well as determine the acceptability of whether the gel material extends beyond the surface of what it is being applied to.

5. Throughout

Speed in production is application-dependent, but recently, one of our customers was considering a switch from pads to gels and ran a test of both materials to gauge the difference in throughput. Their study revealed that it required an operator 18 seconds to apply one pad, including handling the pad, placing it properly, and then moving on to the next component. Using a dispensable gel and an automated process, those same steps required only four seconds.

6. Technology advances

Gap filler pads have long been the go-to choice for many design engineers, but recent advances in thermal gels, which are highly conformable, pre-cured single-component compounds, can provide superior performance, greater ease of manufacturing and assembly, and a lower cost in certain high-volume applications; particularly as electronic design applications get smaller, more fragile and more complex.

The use of the two materials must of course be decided individually. We will be happy to help you with the selection or advise you on which interface material makes the most sense in your case. Please feel free to contact our team directly here!