How to choose a heat sink attachment method to secure your heat sink and for optimal heat transfer (part 2 of 2)

In part 1 of our 2 part series, we laid the ground work for our two part series by noting that there are six main methods you can use to secure a heat sink to a semiconductor

  1. Thermal Tape
  2. Epoxy
  3. Wire Form Z-Clips
  4. Clips
  5. Threaded Stand-offs (PEMS) and Compression Springs
  6. Push-Pins and Compression Springs

In part one we covered thermal tape, epoxy and wire form z-clips. In part two we’ll cover clips, push pins and stand offs and have a special offer for our readers to get all this information in a handy download.

Commercial heat sink clip and ATS maxiGRIP heat sink clip Heat Sink Clips: Heat sink clips are Plastic or plastic/wire clips that grip the components. They are a step above z-clips in ease of use and application. Where a Z-Clip requires a PCB anchor, standard heat sink clips do not. In fact, as long as you have keep out area available around a chip and height available, a clip is a great option. There are many options in using a clip. There are very basic clips, such as those from Malico, which quickly and easily hold a heat sink onto a semiconductor and more advanced clips such as what we at ATS offer in our maxiGRIP and superGRIP clips. The main benefits of a clip are, first, they apply a pre-load to the TIM (thermal interface material) improving thermal performance. Second, they require no holes or anchors in the PCB. This is a very big benefit since clips do not reduce the trace space available for board layout. Third, clips make rework easy by allowing heat sinks to be easily removed and reapplied without damaging the PCB board. Finally, some clips, like maxiGRIP and superGRIP provide a strong enough mechanical attach to pass NEBS, ETSI and MIL shock and vibration. There are some downsides that need to be noted though. First, designers need to insure they design in some keep out area around the semiconductors so that a clip can be used. That also assumes that the design team has considered a thermal management strategy during the architect phase of the product too. Secondly, clips do add extra assembly time since they have to be manually applied.

heat sink being attached to a board using a PEMThreaded Standoffs (PEMS): These are threaded mechanical assemblies that offer the highest level of retention and stability. This approaches benefits include, first, that they are a strong mechanically. They will pass shock and vibe for NEBS, ETSI and MIL.  Second, they provide the highest TIM preload, insuring excellent performance from whatever thermal interface material you choose. Third, they are ideal for heavy copper heat sinks. Finally, they make installation and rework easy since a simple unscrewing of the attach allows the non-destructive removal of the heat sink.  But, as with all heat sink attach methods, there are a few drawbacks to consider. First, they require holes in the PCB removing valuable space for trace. Second they tend to be expensive, especially given that holes need to be drilled into a PCB board to use them.

push pin attach for heat sinks Push-Pins: These are generally plastic or brass push-pin that offer quick and easy mechanical attachment. They are generally equally strong to a threaded standoff (PEMs) approach to heat sink attach. Push pins offer a very strong TIM preload as well as being ideal for large, heavy copper heat sinks. Some of the drawbacks include requiring holes in the PCB board which reduces the trace length space available, a generally complicated assembly process, and finally a fairly high price relative to other solutions.

That wraps up our two part series on heat sink attachment options.

Special offer for our readers to get all this information in a handy download
There’s a lot of material in our two part series on heat sink attachment. To make referencing our series quicker, we’ve assembled this material into a two page “Resource Guide” completed with images as a handy reminder during your next thermal management project.To get a copy, simply drop some email to us at joday@qats.com with the words, “HEAT SINK ATTACH OFFER” in the subject line and we’ll send a copy to you.

If you’re looking for a solution on heat sink attachment and need to bounce this off us, feel free to! ATS sells various heat sinks attachment options, of course, and we’ll talk about that next time, but we’re happy just to discuss your options in your application, so call us at 781-769-2800, email us at sales.hq@qats.com or visit our website at http://qats.com

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