Tag Archives: thermal interface materials

Engineering How-To: Removing Thermal Interface Materials

By Norman Quesnel
Senior Member of Marketing Staff
Advanced Thermal Solutions, Inc. (ATS)

As you may already know, TIMs – thermal interface materials – are not especially easy to remove from heat sinks. But the needs to do so are common: repositioning the sink, switching to a better performing TIM, replacing components, etc.

Most of today’s TIMs are bonded to heat sink surfaces with a pressure-sensitive adhesive layer. The rest of the TIM may be an elastomer filled with thermally conductive particles. Bonding pressure, such as from clips and screws increase the thermal performance, but the result can be a TIM that’s hard to remove from the heat sink surface.

Another kind of TIM is thermal grease, which is an excellent heat conductor but is inherently messy. This must be accounted for when removing thermal grease from a heat sink surface.

With the right tools and some patience, a heat sink can have its TIM removed completely. The approaches are similar for removing different kinds of TIMs.

Removing Thermal Tapes

Removing Thermal Interface Materials

Double-sided thermal interface tapes provide exceptional bonding properties between components and heat sinks. For many applications they remove the need for mechanical fasteners to secure the sink to the component.

Here we are showing the removal of Parker Chomerics Thermattach T412 tape from a heat sink. The T412 tape has aluminum mesh carrier which helps improve heat transfer. The aluminum also helps keep the TIM together when it’s removed.

Use a razor blade, but don’t gouge the aluminum because if it makes the surface uneven that will negatively impact heat transfer. Start at one corner, try to lift the TIM slightly the razor blade, be careful not to cut yourself.

Next, put the heat sink (upside down) on a paper towel. This is mainly to protect the fins of the heat sink from getting scraped. Then, use a putty knife with a flexible blade, or a plastic scraper or something similar with a non-gouging edge to help remove the rest of the TIM.

Push the scraping edge carefully forward under the TIM corner, while pulling the TIM slightly up. While you are starting to lift the original TIM corner from the surface, you can start doing the same on another corner. And if continue to work at it from different angles eventually you can get the TIM off.

If there is TIM residue left over on the heat sink surface, you can use a lint-free cloth and a solvent to wipe it clean. The solvent should be something that won’t damage the finish on the heat sink. Here we used isopropyl alcohol. You may have to repeat this several times to get everything off and you have a clean surface.

Removing Phase-Change Materials

Phase-change materials (PCM) can be removed with similar steps as with thermal tapes. These images show the removal process using a maxiFLOW™ push pin heat sink from Advanced Thermal Solutions, Inc. (ATS).

Start with sharp, clean razor blade because a plastic scraper’s edge isn’t fine enough to penetrate cleanly under the TIM. Be sure the razor blade is straight to minimize the risks of nicks to the heat sink surface. The TIM manufacturer’s data sheet recommends using a razor blade to remove the phase change TIM. In this demo, the TIM is Chomerics T766 PCM. Slowly work the razor blade edge under the TIM, be careful of your fingers.

After a lot of use phase change materials can be hard to remove compared to new pieces. Use the razor under different corners. Go slowly until you get all the material off. You will be left with some PCM residue on the heat sink surface.

You can put a small amount of isopropyl alcohol on the surface and use this as a lubricant and go back with the razor blade to get a close shave on that surface to remove much of the remaining TIM residue.

When your sink’s surface is nearly clean, get a lint free cloth or a wipe. With some alcohol and with a bit of rubbing you should be able to remove the rest of the phase change material.

Removing Thermal Grease

Here we start with a heat sink with thermal grease on its mounting surface.

Start by removing as much grease as possible using a dry cloth or paper towel. You should be able to get most of the grease off this way.

Then, for the leftover grease residue, use a lint-free cloth or rag with some alcohol or another type of solvent that won’t eat away at the heat sink’s anodized surface. With a little elbow grease, you should be able to get the surface clean.

Note that If you’re going to be doing a lot of handling of thermal greases and solvents, it’s advisable to wear protective gloves.

For more information about Advanced Thermal Solutions, Inc. (ATS) thermal management consulting and design services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com. To register for Qpedia and to get access to its archives, visit 

What is the Thermal Impact of Imperfections in Phase-Change Material

Advanced Thermal Solutions, Inc. (ATS) engineers have received several questions from customers about the phase-change material that comes standard on the base of all ATS heat sinks. Engineers have asked whether imperfections on the surface of the grey foil that protects the phase-change material, such as dents or wrinkles, have a significant impact on the thermal interface material’s thermal performance. Do these imperfections have any impact at all? Should the liner be removed?

ATS uses Parker Chomerics Thermflow™ T766 thermal interface material (TIM), which comes with a thin, protective layer of metal foil that should not be removed when placing the heat sink on the device it is intended to cool.

Phase-Change Materials

ATS heat sinks come with Chomerics T766 phase-change material standard. (Advanced Thermal Solutions, Inc.)

When pressure is applied, the phase-change material (and the metal foil) conform to both surfaces, completely removing air gaps or voids to maximize heat sink performance. The phase-change material will “attain minimum bond-line thickness” and “maximum surface wetting,” according to information from Chomerics, to limit the thermal resistance path and ensure almost no thermal contact resistance between the device being cooled and the heat sink. For the T766, the phase-change temperature is listed as 55°C. The liner should remain in place when placing heat sink on the device it is intended to cool (see the video below).[1]

Should engineers be concerned about the appearance of the metal foil lining? Do the dents or wrinkles in the lining impact the performance of the phase-change material and potentially impact the efficiency of the heat sink?

To reassure engineers that the appearance of the metal foil would have a negligible impact on the thermal performance of the TIM, the Chomerics Research and Development Department released the results of tests that the company performed on the T766 conformable metal foil. [2] Chomerics studied the impact on thermal impedance when the foil was wrinkled, dented, and even folded.

Researchers tested materials that were not wrinkled, lightly wrinkled, moderately wrinkled, and severely wrinkled under different pressures (20 psi, 50 psi, and 100 psi). The results (shown below) demonstrated that even when wrinkled “to a far greater extent than would be expected in actual handling” thermal impedance never increased more than 0.02°C-in22/W. The report explained, “For 50 W of power, through one square inch of material, that’s only 1.0°C change!”

The dent test was created using a wooden tongue depressor and included a sample with five dents per square inch and a second with 15 per square inch. As was demonstrated in the wrinkle study, the dents smoothed out during the testing process and showed a minimal impact on thermal impedance. “Once again, the thermal impedance did not increase by more than 0.01°C-in2/W. For 50 W of power, through one square inch of material, that’s only 0.5°C change! The metal foil carrier is so conformable that the dents were almost unidentifiable after testing with 100 psi of pressure.”

The final test was performed on T766 that was folded. One sample was folded under on one edge and the second was folded to overlap down the center. The results indicated that small folds of up to 5% of the pad’s area does not significantly impact thermal impedance. A large fold, which tripled the thickness of the foil in the center of the sample, had a significant impact on the thermal impedance of the material.

The report concluded, “T766 will perform extremely well even when the pad is wrinkled or folded, or the foil is scratched or dented. The high conformability of the metal foil carrier will allow it to smooth out and erase almost any imperfection.”

1. https://www.parker.com/literature/Chomerics/Parker%20Chomerics%20

2. http://www.parker.com/parkerimages/Parker.com/Divisions-2011/Chomerics%20Division/SupportAssets/Parker%20Chomerics%20THERMFLOW

For more information about Advanced Thermal Solutions, Inc. (ATS) thermal management consulting and design services, visit https://www.qats.com/consulting or contact ATS at 781.769.2800 or ats-hq@qats.com.

Announcing our ATS Electronics Cooling Webinars for Third Quarter of 2012

ATS, Advanced Thermal Solutions, Inc. will present technical webinars on electronic cooling topics in July, August and September 2012. Each of these free events will provide engineering-level training in a key area of modern thermal management.

Here are the different webinar topics and presentation times:

Using Thermal Interface Materials to Improve Heat Sink Thermal Performance

July 26, 2012 at 2:00 p.m. ET

To cool hotter components, engineers are using larger fans and heat sinks, and increasing surface areas. These hardware enhancements can add significantly to design costs. In many cases, cooling performance can be improved by using a higher performance interface material between the case and the heat sink. Participants will learn the importance of lowering thermal resistance using thermal interface materials, or TIMs, and the different kinds of TIMs available from the market.

Air Jet Impingement Cooling

August 23, 2012 at 2:00 p.m. ET

Ongoing increases in power in devices such as processors and IGBTs mean that higher capacity cooling methods are needed to remove excess heat. One such method is the jet impingement of a liquid or gas onto a surface on a continuous basis. Lab experiments at ATS have shown up to a 40% improvement in cooling achieved using this method. This webinar will explore jet impingement cooling theory, implementation and best practices.

LED Thermal Management in Commercial and Consumer Lighting Applications

September 27, 2012 at 2:00 p.m. ET

Excess heat directly affects both short-term and long-term LED performance. The short-term effects are color shift and reduced light output, while the long-term effect is accelerated lumen depreciation and thus shortened useful life. Participants will learn how to diagnose and solve thermal issues in consumer and commercial LED applications.

Each of these one-hour online tutorials will include detailed visuals, real world examples, instructions, definitions and references. Audience questions will be answered by the presenters during and after the presentation. One or more ATS PhD-level thermal engineers will be presenting live.

There is no cost to attend these ATS webinars, but virtual seating is limited. Registration is available online at http://www.qats.com, or by calling 1-781-949-2522.