Design Of Radiator For High-power LED Multi-chip Module And Analysis Of Packaging Thermal Resistance

Regarding high efficiency, low energy consumption, long life and friendliness to environment and so many advantages, LED lighting is considered as the forth-generation illuminating light source. For different use environment, heat dissipating of LED chips meets different restrictions, so different thermal designs are required to meet the demand in different places. With the single LED chip power rising, better packaging structure is needed to meet the increasing heat dissipating requirement.For high-power LED street lamps of complex shape, as air flow is obstructed by light shell,it is difficult to dissipate heat through nature convection. Fin heat pipe is select to solve the problem, heat is conducted through heat pipe to unobstructed space for air flow, and then dissipated through nature convection on fins. Fin size and fin spacing have been mathematical optimized to enhance nature convection heat transfer.Water cooling is selected for automobile high-power LED. The relationship between inlet flow rate, temperature of PN junction and pump power has been investigated by numerical simulation analysis. Serial channel, pseudo-serial channel, parallel channel and pseudo-parallel channel are totally compared. The influence of factors of the heat dissipating structure, including fin thickness, inlet flow rate and so on, has been investigated. The relationship between PN junction and the relative standard deviation (RSD) of speed in each sub-channel has been investigated. Method of reducing RSD has been studied and distribution factor K is most significant factor.Thermal resistance of each part between PN junction and heat sink has been studied. Based on the measurement of thermal diffusion coefficient of DCB base plate and Cu-TIM-Cu structure, interface contact thermal resistance in DCB base plate and TIM has been calculated. Thermal diffusion coefficient of Cu-TIM-Cu structure has been measured after aging to study the thermal resistance changing in long-term heat load.The concept of actual-heat-flow thermal resistance is proposed. Due to restriction of heat flow, actual heat flow thermal resistance is one order of magnitude larger than the theoretical thermal resistance.Etching-type reflector on base plate has been designed to reduce actual-heat-flow thermal resistance.In water cooling mode, the heat conduction parts constitute the main part of thermal resistance. Chip and chip TIM layer are 2 most significant parts in thermal resistance. Based on indirect calculation, the equivalent conductivity of 5μm multilayer structure is 0.9155W/(m·K)。Larger substrate vertical structure LED has been designed to spread heat flow horizontally in substrate, as lead to reducing actual-heat-flow thermal resistance of chip substrate, chip TIM and DCB base plate.