Preparation of copper thermal interface materials by laser method

Abstract

In recent years, driven by the continuous miniaturization of high-performance electronics, the heat fluxes generated by semiconductor components increases dramatically, urges the development of more effective cooling methods, to ensure the reliability, stability and performance of these components, Therefore, it is crucial to solve the heat dissipation problem of electronic products. thermal interface material (TIM) is typically to fill the gaps between the two imperfect surfaces, to increase the contact area and reduce the contact thermal resistance. Developing new TIMs is crucial for the future development of the electronics industry, In the flip chip package, TIM has three key roles, which are to dissipate the heat of the chip, to allow higher processing speeds. during temperature cycling, to absorb strain caused by coefficients of thermal expansion (CTE) mismatch between the die, substrate, and the integrated heat spreader (IHS). all these activities have to be performed at room temperature in order to ensure the processor stability.At present, Polymer-based materials are commonly used as TIM. Polymer TIM consists of conductive filler particles and polymer substrate. Due to most polymer substrate has very poor thermal conductivity, generally about 1- 6W/(m.K), the heat conduction is based on the collisions between the filler particles, Therefore, it is easy to understand that the inherent thermal conductivity of 100% metal far exceeds that of polymer-based TIMs. This paper using the laser method to directly deposit a layer of 100% metal copper layer on the chip, Our results show that the Si and Cu were well bonded. No reaction layer and porosity at the interface between the metal copper layer and the silicon substrate(Fig. 4). Copper has a high thermal conductivity, thus this TIM can result in orders-of-magnitude improvements in cooling performance, moreover, the porous layer may absorb thermal strain resulting from the mismatch of CTE between the die, substrate and the IHS, during temperature cycling. A simple central processing unit (CPU) was employed to be direct deposited a layer of copper as TIM at low temperature successfully.