Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Fabrication of insulated metal substrates with organic ceramic composite films for high thermal conductivity Seonghyeop Kim a,c,1, ⁎ , Jooyoung Kim b,1, ⁎ , Jin Hyeok Kim c,⁎⁎ a R & D Division, Feelstone Inc., 37 Eco-gil, Damyang-eup, Damyang-gun, Jeollanam-do 517-700, Republic of Korea b 3D Conversion Business Center, Gwanju Technopark, 333 Cheomdan-gwagiro, Buk-gu, Gwangju 500-706, Republic of Korea c Optoelectronic Convergence Research Center, Department of Material Science and Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 500-757, Republic of Korea ARTICLE INFO Keywords: Insulated metal substrate Organic ceramic composite Coating mixture Sol-gel Thermal conductivity Breakdown voltage ABSTRACT Insulated metal substrates (IMSs) were fabricated and characterized using an organic ceramic composite as a coating mixture. Organic‐inorganic sol solutions were prepared by a sol‐gel process using TEOS (tetraethy- lorthosilicate), MTMS (methyltrimethoxysilane) and PhTMS (phenyltrimethoxysilane). Ceramic fillers were composed of aluminum oxide (1 and 4 μm) and silicon nitride. The optimal ratio of ceramic filler in the coating mixture was found to be 70 wt%. A thermal conductivity of 3.16 W/mK and a breakdown voltage of 4 kV with a leakage current of 0.17 mA/cm 2 were obtained for the 122 μm-thick film. A well-networked microstructure between the sol resin and filler in the organic ceramic composite films enhanced the properties of the IMS, such as thermal conductivity and electric insulation. 1. Introduction Insulated metal substrates (IMSs) have attracted attention as a promising substrate for high-density packaging because they have good thermal dissipation and high thermal conductivity and can act as a heat sink or heat substrate [1,2]. Especially in the field of power modules, IMSs have many applications, such as metal‐oxide semiconductor field- effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), intelligent power modules (IPMs) and backlight units in the automotive and semiconductor industries [3]. In ultra‐large‐scale integration (ULSI) circuits, such as systems on a chip (SOC) and wafer‐scale integrations (WSIs), the rapid radiation of generated heat is important because of the numerous integrated chips, resulting in a decrease in device lifetime of the power module. For this reason, the plastic circuit board for power modules has been changed to an IMS for its high thermal conductivity, radiant heat and withstanding voltage. However, most IMSs are made of epoxy resin with some ceramic fillers, such as alumina (Al 2 O 3 ) and aluminum nitride (AlN), which are known to have a thermal endurance below 200 °C due to the limited tolerance of the epoxy [4], which results in weight loss of the epoxy resin beginning at 150 °C and reaching a loss of 5% at 346 °C [5]. Therefore, hybrid coatings, so‐called organic‐inorganic mixtures, have been considered as good candidates for the fabrication of IMSs, and many studies have reported the successful avoidance of cracks on the metal substrates from different thermal expansions and thermal shock [3,6,7], as well as improved thermal properties by adding filler [8– 12]. In this paper, we fabricated a mixture of organic-inorganic sol and ceramic filler as a coating material for IMS application. Via a sol-gel process, the organic-inorganic sol solution is synthesized from tetra- ethylorthosilicate (TEOS) as an inorganic network former, methyltri- methoxysilane (MTMS) and phenyltrimethoxysilane (PhTMS). The fillers Al 2 O 3 and silicon nitride (Si 3 N 4 ) were added into the organic- inorganic sol solutions for the coating mixture. The sol‐gel based coating mixture was deposited on an aluminum alloy substrate. To obtain improved thermal conductivities and withstanding voltages, various ratios of ceramic filler were investigated. 2. Experimental details Fig. 1 shows a flow chart of the synthesis of the organic‐inorganic sol solution. As a starting solution, silica sol and organosilanol sol were prepared with a mole ratio of 0.6 ~ 0.9:1. The silica sol was prepared in ambient atmosphere for 12 h by stirring tetraethylorthosilicate (TEOS, Dow Corning) with ethanol, HCl, and distilled water in a molar ratio of TEOS:ethanol:HCl:H 2 O =1:4:0.0001:4. The organosilanol sol was obtained from MTMS (methyltrimethoxysilane, Dow Corning), which http://dx.doi.org/10.1016/j.ceramint.2017.03.163 Received 20 January 2017; Received in revised form 17 March 2017; Accepted 26 March 2017 ⁎ Corresponding author at: R & D Division, Feelstone Inc., 37 Eco-gil, Damyang-eup, Damyang-gun, Jeollanam-do 517-700, Republic of Korea. ⁎⁎ Corresponding authors. 1 gwangelove@naver.com E-mail address: jinhyeok@chonnam.ac.kr, gwangelove@naver.com (J. Hyeok Kim). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2017 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Kim, S., Ceramics International (2017), http://dx.doi.org/10.1016/j.ceramint.2017.03.163