Under the intervention of external electric field, the outermost valence band electrons gain a little extra energy without violating the exclusion principle to reach many empty places within the band near. Compared with thermal excitation out-of-order, Excited electrons by the electric field and the field in the direction opposite to the momentum, it will produce a collective motion in the crystal, thereby forming current. For tungsten copper heat sink, due to different equivalent orbital and atom distance of W and Cu atoms, the band (or empty) overlap, constitutes a full conduction band, and has excellent electrical conductivity. For copper with divalent, its valence band is full band, which the valence band and a higher band overlaps, filled with electrons can occupy the vacated belt so that it has good conductivity; while tungsten with hexa-valence, its valence band is not full and the electrical conductivity is lower than copper phase. So this is a good proof of the conductivity of tungsten copper heat sink materials or conductivity depends on copper content.

The other influencing factor is porosity, which will hinder the movements of electrons. In other words, the higher porosity, the lower tungsten copper heat sink electrical conductivity. Due to tungsten copper is a kind of pseudo alloy, which composed of two kinds of metals with a big difference, there are a lot of interface and porosity between W and Cu grains. The experiment shows that tungsten copper composite material and its electrical conductivity were positively correlated with the density, the lower the density, the lower the conductivity. In addition, sintering temperature controlling is also important, electrical conductivity of tungsten copper has a sharp decline when it over-burnt. The main reasons comprise two, one is inside W phase has severe segregation and porosity, and as the main medium and Cu conductive phase may also undergone some degree of segregation, such that its penetration to the surface, the conductivity decreases with the decreasing content of Cu inside.