Thermal interface materials development of thermal conductivity

Increasing the Thermal Conductivity (TC) of Thermal Interface Materials

Why is Thermal Conductivity important?

As elec­tron­ic equip­ment advances and tech­nolo­gies progress, mod­ern com­po­nents like light-emit­ting diodes (LEDs), EV Bat­ter­ies, and Semi­con­duc­tor Advanced Pack­ag­ing appli­ca­tions are under­go­ing inte­gra­tion, minia­tur­iza­tion, and increased intel­li­gence. This evo­lu­tion results in con­cen­trat­ed heat gen­er­a­tion, sig­nif­i­cant­ly impact­ing the ser­vice life and per­for­mance of elec­tron­ic devices. Thus improv­ing the heat con­duc­tion of Ther­mal Inter­face Mate­ri­als (TIMs) has emerged as a crit­i­cal chal­lenge, urgent­ly requir­ing solu­tions to ensure the opti­mal func­tion­al­i­ty, longevi­ty, and reli­a­bil­i­ty of elec­tron­ic equipment. 

TIMS in light-emitting diodes (LEDs), EV Batteries, and Semiconductor Advanced Packaging applications

The Evolution from Traditional to Polymer-Based TIMs:

Elec­tron­ic devices dis­si­pate heat using heat sinks, and TIMs play a cru­cial role in facil­i­tat­ing this process. Tra­di­tion­al ther­mal con­duc­tive mate­ri­als, such as sil­ver and cop­per, have lim­i­ta­tions in terms of weight and flex­i­bil­i­ty. In response to these chal­lenges, poly­mer-based TIMs have gained wide­spread use, lever­ag­ing advan­tages such as excel­lent pro­cess­ing per­for­mance, cost-effec­tive­ness, and low density. 

Despite the inher­ent­ly low ther­mal con­duc­tiv­i­ty of poly­mers (< 0.4 W/m‑K), numer­ous strate­gies have emerged in recent years to enhance the TC of poly­mer-based TIMs (Fig­ure 1). Their TC is com­mon­ly improved by incor­po­rat­ing ther­mal­ly con­duc­tive fillers such as graphene or car­bon nan­otubes. The chal­lenge, how­ev­er, lies in bal­anc­ing the filler con­tent to enhance heat dis­si­pa­tion with­out com­pro­mis­ing pro­cess­ing abil­i­ty and mechan­i­cal prop­er­ties. Con­se­quent­ly, the pur­suit of high-per­form­ing TIMs with min­i­mal filler con­tent becomes cru­cial, par­tic­u­lar­ly in the realm of microelectronics.

To achieve opti­mal filler con­tent bal­ance, one strat­e­gy is to mod­i­fy the filler sur­face using reac­tive chains to achieve smooth flow of the fillers. CAPLINQ pro­vides a wide range of Reac­tive sil­i­cones that enable high­er filler con­tent while main­tain­ing prop­er flowa­bil­i­ty with­in the poly­mer matrix, there­by max­i­miz­ing ther­mal per­for­mance. This reac­tive sil­i­cones has the abil­i­ty to make the inor­gan­ic filler eas­i­er to blend into the sil­i­cone binder resin which facil­i­tates filler dis­per­sion.

Among the reac­tive sil­i­cones prod­ucts, FM0815J is a recent­ly devel­oped reac­tive sil­i­cone trimethoxy silyl designed to increase filler load­ings improv­ing per­for­mance prop­er­ties in sil­i­cone sys­tems which has the abil­i­ty to chem­i­cal­ly bond to the sur­face of the inor­gan­ic filler thus a more sta­bi­liz­ing the filler dispersion.

Factors affecting the Thermal Conductivity

Factors/Modifications affecting Thermal Conductivity of Polymer-based Thermal Interface Materials
Fig­ure 1. Factors/Modifications affect­ing Ther­mal Con­duc­tiv­i­ty of Poly­mer-based Ther­mal Inter­face Materials

More­over, TC also depends on oth­er mul­ti­ple fac­tors includ­ing the ther­mal­ly con­duc­tive filler char­ac­ter­is­tics, poly­mer matrix char­ac­ter­is­tics, microstruc­ture con­trol of fillers, and ther­mal inter­fa­cial resis­tance, as shown in Fig­ure 1. 

Gen­er­al­ly, the ran­dom dis­tri­b­u­tion of fillers in com­mon TIMs usu­al­ly leads to a low through-plane TC: 1–5 W/m‑K (PTM5000PTM6000). Although many tech­niques have been devel­oped to fab­ri­cate paper-like films which show sat­is­fac­to­ry in-plane TC: 5–8 W/m‑K (PTM7000, PTM7900, & PTM7950), a high through-plane TC >8 W/m‑K (HT9000, HT10000, & HT11000) is more desired for some cas­es in high end appli­ca­tions. Unlike strate­gies that have been devel­oped to induce filler align­ment in the in-plane direc­tion, the meth­ods to ver­ti­cal­ly align fillers in the through-plane direc­tion are still limited.

Some pri­or efforts to improve the through-plane TC of poly­mer com­pos­ites are on adjust­ing the ori­en­ta­tion of fillers in the through-plane direc­tion and con­struct­ing a 3D net­work struc­ture. These tech­niques main­ly involve the con­struc­tion of a seg­re­gat­ed struc­ture, mag­net­ic fields, elec­tric fields, chem­i­cal vapor depo­si­tion (CVD),3D print­ing, ice-tem­plat­ing and infil­trat­ing, exten­sive shear force-direct­ed meth­ods, tem­plate-direct­ed meth­ods and hydrother­mal reduction.

Exam­ple of recent poly­mer-based with advanced filler sys­tem TIMs are phase change mate­ri­als (PCMs) designed by Hon­ey­well, which are dri­ven by an inno­v­a­tive poly­mer tech­nol­o­gy, and can be cus­tomized to fit diverse prod­uct appli­ca­tions and end uses. In addi­tion to phase change mate­ri­als, we offer a vari­ety of prod­ucts with high ther­mal con­duc­tiv­i­ty and high com­press­ibil­i­ty, includ­ing Ther­mal Gap Pads, Ther­mal Hybrid, Ther­mal Grease, Ther­mal Insu­la­tors, and more.

The research and devel­op­ment of TIMs is a con­tin­u­ous process and choos­ing the right ther­mal inter­face mate­r­i­al is crit­i­cal for improv­ing heat dis­si­pa­tion in mul­ti­ple devices. An appli­ca­tion-spe­cif­ic assess­ment can be con­duct­ed to rec­om­mend a suit­able TIM appli­ca­tion. Con­tact us and our appli­ca­tion engi­neers and in-house ther­mal experts will help you out with prod­uct selec­tion for your appli­ca­tion requirements.

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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