Bonded Ceramic-Metal Layers for Fabrication of Thermal Conduction Plates

Abstract

The work described in this article is part of an effort to build reliable and efficient liquid cooling modules for high-power laser diodes. The cooling system is designed to mount at least 12 laser diodes to a common microheat exchanger, thus requiring a large-size thermal conduction plate. Fabrication of the thermal conduction plate involved void-free bonding of copper layers on both sides of an aluminum nitride (AlN) plate. In the current study, ceramic-metal bonding methods using moly-manganese metallization and active metal brazing were investigated. Bonded AlN/copper plates were characterized and evaluated by optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. For detecting voids, cracks, and delamination, some of the plates were analyzed by scanning acoustic microscopy (C-SAM). Results indicated that >99% void-free bonded AlN/Cu plates can be fabricated by using properly selected metallization conditions and brazing temperature profiles. The active metal brazing approach was found to be a cost-effective method of fabricating reliable, void-free thermal conduction plates.