The table shows the dielectric constant of some common ceramics that can be used as fillers to enhance the thermal conductivity.

Other than the high thermal conductivity, the dielectric layer of PCB also requires high insulation resistance, high glass transition temperature (Tg) and decomposition temperature, high adhesion strength with copper and base metal plate, proper dielectric constant, and manufacturability. The first three characteristics are inter-correlated; a high Tg and decomposition temperature of the dielectric layer enables the board to continuously serve in a high temperature condition without causing any harm to its other properties such as insulation resistance or resulting in any defects such as delamination.

Same as the thermal conductivity, the characteristic of dielectric constant also depends on the type and the percentage of fillers added in the resin matrix.  Table shows the dielectric constant of some common ceramics that can be used as fillers to enhance the thermal conductivity. The use of a higher dielectric constant of ceramics will result in higher dielectric constant of the insulation dielectric of the PCB, and the amount it added will further intensify this effect. Selection of the types of fillers depend on the applications of the PCB, alumina may be more appropriate if low cost products with less thermal conductivity are required, while boron nitride is more suitable for high speed applications due to its lower dielectric constant.

Manufacturability, affects the production yield of metal core laminates and the PCB in laminate manufacturers and PCB fabricators respectively. The effect of the percentage of f iller contents on the performance of PCB is twofold. Firstly, it has direct influence on the rheology of the resin matrix that may affect resin flow during lamination of the metal core laminate or PCB. Insufficient resin flow may result in resin void or poor adhesion strength between dielectric and the metal base plate or copper foil. Secondly, in combination with the effect of the hardness of the filler, it affects the machinability of the PCB, too hard a filler leads to worn out of drill bits and may result in poor hole quality.