Thermal Performance Comparison of Thick-Film Insulated Aluminum Substrates With Metal Core PCBs for High-Power LED Modules

Abstract

Evolution of lumens per watt efficacy has enabled exponential growth in light-emitting diode (LED) lighting applications. However, heat management is a major challenge for an LED module design due to the necessity to conduct heat away from the LED chip. Elevated chip temperatures cause adverse effects on LED performance, lifetime, and color. This paper compares the thermal performance of high-power LED modules made with two types of circuit boards: novel substrates based on insulated aluminum material systems (IAMSs) technology that inherently allows using thermal vias under the LEDs and traditional metal core printed circuit boards (MCPCBs) commonly used with high-power LED applications. IAMS is a thick-film insulation system developed for aluminum that cannot handle temperature higher than 660°C. The coefficient of thermal expansion of IAMS pastes is designed to match with aluminum, which minimizes any bowing. The thermal via underneath the LED enables excellent thermal performance. More than 7°C reduction in LED junction temperature at 700-mA drive current and 27% reduction in the total thermal resistance from the LED junction to the bottom of the substrate were demonstrated for the IAMS technology when compared with MCPCB. When considering only the thermal resistance of the substrate, reductions of around 70% and 50% were obtained. This versatile and low-cost material system has the potential to make LEDs even more attractive in lighting applications.

Copper-Core MCPCB With Thermal Vias for High-Power COB LED Modules

“…The result could be explained by variation in LED performance and the substrate color because the alumina module with white substrate reflects more light than Cu MCPCB module with darker substrate due to absorption losses. The similar results have been reported also in our previous studies [21]. This is a drawback of the Cu MCPCB technology proposed in this paper and needs to be tackled by white masking or by changing the color of the insulator material to make this technology commercially successful.…”

“…Thermal vias under the heat source could be an effective heat management solution as reported for ceramic substrates in [19] and [20] and IMS in [21]. Also, for PCBs, a significant thermal performance enhancement with thermal vias is reported [22].…”

“…1), the heating current through each red LED chip was 255 mA and through each blue LED chip was 113.3 mA. The measurement procedure followed JESD51-51 [25] standard and is described more in detail in [21].…”

Thermal impedance measurements of layered Metal Core PCB used in LED lighting

“…The Laplace transformed temperature change at the second layer is (8) The areal heat diffusion time is A t =A tm + A ti (9) where (10) (11) as shown in Fig2. A tm is the area heat diffusion time of MCPCB without boundary thermal resistance, and A ti is attributed to the influence of the boundary thermal resistance.…”

“…Layered Metal Core PCB (MCPCB), for its low thermal impedance, was widely used in LED lighting applications. Recent years, various MCPCB technologies were developed to achieve lower thermal impedance [4][5][6][7][8][9]. However, due to their different techniques, it is hard to use one appropriate method to evaluate the thermal impedance of all.…”