Engineering performance in applied EPD: problems and solutions

Providing the particle size, shape and size distribution are suitable, appropriate dispersion media and surface-active additives can usually be found for the electrophoretic deposition (EPD) of powder with any chemical composition. The design of the EPD cell is largely dictated by the geometry of the final product and the required dimensional tolerances. The integrity of the microstructure and freedom of the product from process defects commonly depend on the deposition parameters and the dispersion chemistry. Demonstrations of laboratory feasibility for EPD products may prove straightforward, but developing an EPD process technology that is suitable for mass production can be far more challenging. This contribution reports four examples: 1. The deposition of silver thermal sinks in low-temperature, co-fired ceramic (LTCC) tape vias. 2. The formation and printing of silver-base alloy lines for conducting interconnects. 3. The embedding of passive ceramic components in punched ceramic tape. 4. The production of porous conducting anodes for solid electrolyte capacitors. In each case, the process parameters have been selected to satisfy the engineering requirements while minimizing the formation of process defects. Observed defects include variations in the particle packing density; loss of adhesion to the substrate, cracking of the deposit and surface roughness or thickness variations.