Laser machining of ceramics and silicon for MCM-D applications

The ceramics were machined with a computer controlled Nd:YAG slab-laser. The laser parameters as well as the process parameters were optimized to obtain kerfs with good quality and cuts without cracks. Two applications were investigated: ceramics and silicon as substrates for embedded MCM-Ds (Multi Chip Modules, Deposited) and water-cooled heat sinks for single chips, multichip modules or laser diodes. For the embedded MCMs, windows were machined into the substrate. Bare dice and standard passive components (like capacitors or resistors) were inserted into these windows and fixed in their position with an epoxy. AlN, Al ₂O₃ and Si were tested as substrate materials. The critical parameter was the mechanical stability of the substrate because of the thermal stress introduced by the following thin film process. For the second application, several heat sinks were produced in AlN. Different methods to clean the cooling channels were investigated. Maximum heat dissipation of water-cooled test-devices was determined for various channel geometries