Category Archives: Thermal Interface Material

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

Posted on January 5, 2011 by | Leave a comment

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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Posted in Heat Sink Attach, heat sink clip, Thermal Interface Material

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Can a thermal interface material, by itself, be effective in thermal management without a heat sink?

Posted on November 15, 2010 by | Leave a comment

Our first reaction when we saw the press release from Fujipoly was one of skepticism. Here’s the full release:

Carteret, NJ Monday, November 15, 2010 A new thermal material breakthrough from Fujipoly allows engineers to reduce chip and circuit temperature by as much as 11% without the need for a heatsink.

The advanced 4-ply, peel-n-stick FPDSEM 90 Cooling Patch offers the fastest and easiest way to radiate heat from an electronic component to the surrounding environment. All you need to do is apply the patch like a sticker to the surface of any hot spot. The material can also be custom cut or trimmed to fit virtually any shape.

The low resistance Cooling Patch provides a thermal conductivity of 1.5 W/m°K and a thermal emissivity of 0.97. Fujipolys FPDSEM 90 is 25mm thick and can be ordered in sheets, rolls or kiss-cut rolls depending on your application.

The phrase our team focused on was, “reduce chip and circuit temperature by as much as 11% without the need for a heatsink.

Here’s a .jpg of their new thermal material. The green marker points to the Fujipoly TIM while the blue marker points to the semiconductor (or click on the photo to zoom in on it)

Fujipoly thermal interface material

While the claims are impressive, unless the paste has significant emissivity (highly metalized) our team did not see how it would work. We speculate that Fujipoly may have developed a special material; however, the 10-11% thermal reduction will not work at higher velocity flow , anything more than 1-1.25 m/s  the impact is in 1-2%.

If anyone of our readers gives this material a try before us, drop us a line and let us know what you learned; joday-at-qats.com

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Posted in Thermal Analysis, Thermal Interface Material

ATS’s Webinar on Thermal Interface Material, still spots open to register, 10/28 2PM – we’ll be live Tweeting it!

Posted on October 26, 2010 by | Leave a comment

We’ll be hosting another of our thermal management webinars on Thursday, October 28, 2PM EST. Dr. Kaveh Azar will be teaching and the subject is about thermal interface material.

Here’s where to go register and join us:  Using Thermal Interface Material to Improve Heat Sink Performance.

We’ll be live Tweeting our event, using the hashtag, #ATS_TIM

Why should you listen in? Because we’ll be covering what the latest is in Thermal Interface Material (TIM, why to use it and what to use. The right TIM can improve your heat sink performance 20% or more!

We’ve blogged about this in the past including topics such as:

  • Does thermal grease have a long term reliablity risk?
  • An article from EP&T on how to choose the right TIM
  • TIM manufacturer roundup so you can find all the TIM suppliers in one convenient place with links

You can see all our posts on Thermal Interface Material here at this link: Thermal Interface Material Posts at ATS’s Blog.

AND least we forget, this webinar is sponsored by our good friends at Ellsworth Adhesives. They have an entire line of TIM for thermal engineering.

Ellsworth Adhesive Logo

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Posted in Thermal Interface Material, Webinar

Fujipoly releases new, high performance additions to its Sarcon line of Thermal Interface Material

Posted on June 30, 2010 by | Leave a comment

Fujipoly, a firm we featured in the ATS Thermal Interface Material Resource Roundup, have released a duo of additions to their fine line of Sarcon specially formulated thermal interface materials. Applicable to an aluminum heat sink, copper heatsink or other applications requiring low thermal resistance gap filler pad compounds, Sarcon 100GR-HL and SARCON XR-Um-Al are both available now from Fujipoly.

SARCON XR-Um-Al is a uniquely formulated gap filler compound that has a putty-like consistency. This physical property contributes to the material’s extremely low contact and thermal resistance while maintaining a thermal conductivity of 17 watt/m-k. The gap filler pad is manufactured with a thin aluminum carrier film for customer-friendly application. The low adhesion aluminum barrier enables users to remove the carrier film after installation with no pull-out effect. This thermal interface material is available in sheets up to 50mm x 50mm with thicknesses ranging from 0.2mm to 0.5mm.

SARCON 100GR-HL is a thermal gap filler pad manufactured with a hardened top surface. The unique, one-sided treatment is less tacky than the opposing surface allowing the thermal pad to consistently adhere to either the target electrical component or opposing heat sink. The hard surface allows for effortless removal without tearing or damaging the material during assembly and rework operations. Sarcon® 100GR-HL transfers heat with a thermal conductivity of 2.8 W/m°K and a thermal resistance of .44°Cin2/W at 72.5 PSI. This 1.0mm thick, flame retardant TIM is available in sheets up to 300mm x 200mm.

Thermal interface material is an important part of a thermal management system. So important in fact we’d like to point our readers to a couple of resources we’ve put together here at ATS. The first is our white paper, “When to use thermal interface material with your heatsink and why?” The second is an on-demand webinar we have made available to the thermal engineering community entitled, “Heat Sink Selection Made Easy“, in which we cover a bit about thermal interface material relative to heatsink selection. These materials are free of charge of course. If you’ve got questions or need a bit of help with your thermal engineering, give us a try, companies like Lucent, and Motorola already have. Call us at 781-949-2521 or email us at sales.hq@qats.com

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Posted in Thermal Interface Material

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Is CPU Cooling best done with a Copper Heatsink or Aluminum Heatsink?

Posted on June 16, 2010 by | 1 comment

The topic of whether a CPU heat sink should be a copper heat sink or aluminum heat sink comes up in every thermal management design. And the short answer as to which material to use is:

“It depends.”

There are many variables in designing the right heat sink, some of which include:

  • Thermal management cost budget relative to BOM cost
  • Orientation of boards (vertical or horizontal)
  • How much weight or stress can be applied to the target chip
  • How much keep out around a chip exists
  • Air flow to the chip
  • Air flow in and through the system (maybe you don’t need a heat sink at all as noted in an earlier ATS White Paper)
  • Component dimensions
  • Component height
  • Target junction temperature
  • Target case temperature

Let’s just focus on the material question though, copper heatsink vs. aluminum heatsink. Chris Soule, Engineering Director at Thermshield, has done a nice one page write up on the topic. Some of his key points include:

  • Pure copper has about two times the conductivity of aluminum but that inherent advantage is only helpful when
  1. Air Flow speeds are 800 LFM
  2. The hot spot on the CPU or other semiconductor is small in comparison to the size of the chip itself.
  • When air flow is 400 LFM or lower or the hot spot on the CPU or semiconductor is spread throughout the chip, then Aluminum is a better choice.
  • The cost of a copper heat sink is often up to three times the equivalent sized aluminum heat sink

In our labs here at ATS, we’ve found that if an aluminum heatsink by itself does not have the necessary thermal condutivity, then using phase change thermal interface material (such as those listed in our Thermal Interface Roundup Post) with the proper pressure applied can make the difference in cooling.

So which do you use? Copper or Aluminum? It depends on the variables noted including your budget. One thing is for sure, there is no clear, one sized fits all answer and the thermal engineer should carefully decide. Hopefully before the electrical design is complete!

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Posted in heat sink, Thermal Interface Material

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