Thermal interface materials for Power Electronics

Thermal Interface Materials for Power Electronics: Insights from NREL Study


Dur­ing the 2009 U.S. Depart­ment of Ener­gy, Annu­al Mer­it Review & Peer Eval­u­a­tion Meet­ing, the Nation­al Renew­able Ener­gy Lab­o­ra­to­ry (NREL) pre­sent­ed under the U.S. DOE Hydro­gen Pro­gram and Vehi­cle Tech­nolo­gies Pro­gram high­light­ed the con­tin­u­ous devel­op­ment of Ther­mal Inter­face Mate­ri­als (TIMs) in Pow­er Elec­tron­ics application. 

The paper by Naru­manchi et al., which was pre­sent­ed, address­es the need for cut­ting-edge ther­mal con­trol tech­nolo­gies to enable high-pow­er den­si­ty appli­ca­tions and reduce the sys­tem cost where­in TIMs still rep­re­sent­ed a sig­nif­i­cant heat removal bot­tle­neck. One of the objec­tives of the study is to iden­ti­fy TIM which meets the tar­get ther­mal per­for­mance of 5 mm2K/W for 100 microns bond­line thick­ness (BLT) , as well as meets the reli­a­bil­i­ty and cost con­straints for pow­er elec­tron­ics application.

In this arti­cle, they dis­cussed the ther­mal resis­tance data of the var­i­ous com­mer­cial TIMs eval­u­at­ed through ther­mal per­for­mance by the NREL study. Among the 40 mate­ri­als test­ed, the NREL study has iden­ti­fied the mate­ri­als which have the poten­tial of meet­ing the tar­get per­for­mance includ­ing Hon­ey­well PCM 45G, an iden­ti­cal mate­r­i­al to Hon­ey­well PCM 45F.


The main appli­ca­tion focus of the ther­mal inter­face mate­ri­als (TIMs) is on auto­mo­tive pow­er elec­tron­ics cool­ing, specif­i­cal­ly for IGBT Pack­age used in an invert­er. All the state of the art ther­mal inter­face mate­ri­als have been evaluated. 

The devel­op­ment of ther­mal greas­es/gels, phase-change mate­ri­als (PCMs), sol­ders, and car­bon nan­otubes (CNTs) as inter­face mate­ri­als have all made sig­nif­i­cant strides. As of today, greas­es, gels, and PCMs are the most wide­ly used with ther­mal per­for­mance reach­ing up to 10 mm2K/W. It can also be not­ed the ongo­ing research on CNT mate­ri­als as TIMs in which Dou­ble-sided CNT has sig­nif­i­cant poten­tial due to its ther­mal resis­tance per­for­mance, which is as low as 4 mm2K/W.

State-of-the-Art Thermal Interface Materials(CNT: carbon nanotubes, PCMs: Phase Change Materials, Greases, and Gels.
Fig­ure 1. State-of-the-Art Ther­mal Inter­face Materials(CNT: car­bon nan­otubes, PCMs: Phase Change Mate­ri­als, Greas­es, and Gels.

Results and Discussion

Since grease is the pri­ma­ry inter­face mate­r­i­al in the auto­mo­tive pow­er elec­tron­ics indus­try, NREL con­duct­ed tests on dif­fer­ent com­mer­cial­ly avail­able ther­mal greas­es. Fig­ure 2b shows the ther­mal resis­tance as a func­tion of grease thick­ness at 75°C, in which the resis­tance is direct­ly pro­por­tion­al to the grease thick­ness as expect­ed. Based on the find­ings pre­sent­ed, it is evi­dent that the com­mer­cial­ly avail­able greas­es exam­ined in this study can yield sat­is­fac­to­ry per­for­mance; how­ev­er, none of them achieve a val­ue as low as 3 mm2K/W.

In cor­re­la­tion to the resis­tance-thick­ness rela­tion­ship, Fig­ure 2a shows the dom­i­nance of bulk resis­tance over con­tact resis­tance. It can be shown here that the five com­mer­cial mate­ri­als hav­ing low resis­tances both on bulk & con­tact resis­tance are: Chome­r­ics XT8030, Hon­ey­well PCM45G/PCM45F, Dow Corn­ing TC 5022, Shinet­su X23-7783D‑S, and 3M AHS1055M.

Fig­ure 3, indi­cates the rela­tion­ship between tem­per­a­ture, pres­sure, and resis­tance. Fig­ure 3a shows that as the tem­per­a­ture increas­es, ther­mal resis­tance increas­es as well. The tem­per­a­ture range dur­ing tests is sub­ject­ed up to more than 120°C which is the oper­at­ing tem­per­a­ture for IGBT pack­ages show­ing poten­tial in the appli­ca­tion. This exhibits the rel­a­tive­ly low­er per­for­mance of Shinet­su X23-7783D‑S on the tem­per­a­ture test which had the high­est resis­tance of 30–50 mm2K/W while the rest only had 5–20 mm2K/W.

Fig­ure 3b shows that as the pres­sure increas­es the resis­tance low­ers. This indi­cates that the com­press­ibil­i­ty of the mate­r­i­al up to a cer­tain BLT is also reduc­ing the resis­tance. This high­lights the superb per­for­mance of Hon­ey­well PCM45G/PCM45F hav­ing the low­est resis­tance of <10 mm2K/W among all the oth­er com­mer­cial TIMs.

Among the TIMs con­sid­ered in this study, Chome­r­ics XT8030, Dow Corn­ing TC 5022, Shinet­su X23-7783D‑S, and 3M AHS1055M had promis­ing per­for­mance in terms of thick­ness. Hon­ey­well PCM45G/PCM45F stood out and showed a huge dif­fer­ence in per­for­mance dur­ing pres­sure tests. Indus­try trends also showed future work that needs to be done with bond­ed, sin­tered, and pos­si­bly semi sin­tered interfaces.

Choos­ing the right Ther­mal inter­face mate­r­i­al for Pow­er elec­tron­ics and IGBT appli­ca­tions can be very com­plex and chal­leng­ing. Luck­i­ly, CAPLINQ has the prod­uct and appli­ca­tion knowl­edge to con­sult you and help you out with a prod­uct rec­om­men­da­tion. Con­tact us for more info


  1. Naru­manchi, Sreekant. Advanced Ther­mal Inter­face Mate­ri­als (TIMs) for Pow­er Elec­tron­ics. U.S. DOE Hydro­gen Pro­gram and Vehi­cle Tech­nolo­gies Pro­gram Annu­al Mer­it Review. 2009

About Darlene Pudolin

Darlene Pudolin is one of CAPLINQ's Application Engineers specializes in Thermal Interface Materials, Fine & Specialty Chemicals, and Soldering Materials within the company's Technical Marketing unit. Darlene recently joined CAPLINQ in early 2023 but has been an experienced materials quality engineer for 5+ years. She has a broad range of experience in materials solution from Thermal Interface Materials, Cement Chemistry, and Hydrogen Renewable Technology. With a long history of serving customers in Industrial and Research academe, Darlene is passionate on driving solutions about troubleshooting points that best fit the market requirements. Based in the Philippines, Darlene holds a Bachelor's degree in Chemical Engineering from Mapua University and currently doing her Master's degree in Energy Engineering at University of the Philippines Diliman.

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