A patterned substrate, the finished part which goes into a TE Cooler. This material conducts heat and insulates electric current. Typically comprised of ALO, BeO or ALN. At least one side of the ceramic has a metal pattern required for the operation of the TE Cooler. ALO ALN BeO Thermal Conductivity (W/in C) .051 4.0 6.5 CTE (10-6/C) 7.0 4.0 9.0