New materials improve properties of ceramic PCBs
The new curamik Advantage features from Rogers Inc. enable circuit experts to optimize the performance of ceramic circuit boards. This is done by selecting additional options, e.g. various coating options for improved copper surface quality, treatments for minimizing surface roughness, step etching, precise laser drilling of small through holes, solder resist to avoid solder bridges and an optimization for silver sintering processes.

The curamik substrates on ceramic basis include curamik Power, curamik Power plus, curamik Performance and curamik Thermal, and offer a wide range of thermal conductivities from 24 to 170 W / m-K. The materials have been developed especially for efficient thermal distribution in heat generating power electronics circuits in active high performance devices such as IGBT or MOSFET modules. The curamik Advantage feature series improves the usability as well as the performance of the curamik materials and increases the reliability in the process.

 

The features provide coatings for all four known curamik printed circuit boards made of nickel (Ni), nickel gold (NiAu) and silver (Ag). Silver coatings may also be applied to individual PCB regions to allow a portion of the copper surface to be exposed. The wet chemical coating process takes place internally and helps to improve the reliability and effectiveness of the wire bonding and soldering processes.

 

Further processes with curamik Advantage are, for example, chemical or mechanical treatments for improving the surface roughness Rz to below 7 μm, use of a solder resist to prevent inadvertent flow of solder as well as the formation of undesired solder bridges, treatment to provide partial discharge-free substrates, and laser drilling of small through holes With diameters of more than 1 mm.

 

Perhaps the most important process of the curamik-Advantage feature family is the optimization for modern silver sintering processes as an alternative to the conventional process for chip bonding and system soldering. By means of silver sintering, very reliable compounds can be produced by heating a paste with minute silver particles. Silver has excellent thermal conductivity (240 W / m-K), and by changing the size of the silver particles contained, compounds having different thermal performance levels can be produced for improved reliability. In the silver sintering process, compounds with standard thicknesses of 50 to 100 μm are formed. Even smaller strengths are already possible today.