In general, the relationship between the traverse speed V of the laser and the absorption ?? (in units of inverse distance, e.g. 1/??m) of the frit can be derived from the diffusion relationship: V=4BD/r 2???(1) where V is the traverse speed of the laser light over frit 14, D is the thermal conductivity coefficient of the frit, r is the diffusion length in the frit and B is a scaling factor.