Porous Copper Layer Development by Dynamic Hydrogen Bubble Template for Power Modules Assembling by Thermocompression

Abstract

Copper is the most widely used materials for microelectronics applications due to their electrical and thermal conduction properties, and in several applications, thick and porous layers are requested. With increased aircraft electrification, there is a need of extremely high-power converters in the power electric chain, interfacing the bus and the electric motor. The COPERPACK project (COPPER based PACKaging for direct cooled power module ANR-19-CE05-0011) aims to module assembling by thermocompression, which requested the elaboration of thin nanoporous copper film to be placed between chips and metallized ceramic substrates.Different possibilities still exists 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.[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 Figure 1