Thermal Efficiency Evaluation after Thermocompression of Copper Layer Obtained By Dynamic Hydrogen Bubble

Abstract

With the increase in engines electrification, especially in aircraft future developments, there is a need of extremely high-power converters in the power electric chain, interfacing the electrical network and the electric motors. The COPPERPACK project (COPPER based PACKaging for direct cooled power module ANR-19-CE05-0011) aims to module assembling by thermocompression, which requests the elaboration of thin nanoporous copper films to be placed between chips and metallized ceramic substrates. Different possibilities exist and have been tested all along the project, such as copper-zinc or copper-manganese electrodeposition followed by an anodic dissolution, but the faster and simpler way resides in electroforming deposition made by Dynamic Hydrogen Bubble Template (DHBT) [1]. This process works in unusual potentials and current densities where the competition between hydrogen discharge (commonly avoided) and copper reduction is very high. In this case, this method achieves thick deposits in very short time (few seconds) with high currents allowing a very fast growth of copper around hydrogen bubbles. Pores and ligaments sizes can be controlled by several operating parameters i.e. current densities, temperature, deposit time, chemical additives [2] as well by pulsed currents. Films were tested for chips assembling by thermocompression, and present excellent behavior’s. Several conditions have been tested, in different configurations, varying the size and the height of the chips.Eventually, this system has been extended to cooling systems, favoring the assembling of copper foams and complex copper shapes, designed for cooling fluid circulation. Once again, the copper layers obtained by DHBT allow to build compact and efficient systems.[1] Abdel-Karim, R.; El-Raghy, S. Chap 4 in Advanced materials and their applications - micro to nano scale. One Central Press, United Kingdom, pp 69–91, 2017[2] Shin, H.-C.; Liu, M. Chem. Mater. 2004, 16, 25, 5460–5464 doi.org/10.1021/cm048887b