A study of the heat-affected zone in the UV YAG laser drilling of GFRP materials

This paper describes the characteristics of the heat-affected zone (HAZ) of a UV YAG laser-drilled hole in glass fiber reinforced plastic (GFRP) printed circuit boards. The structures of the HAZ produced by different laser parameters were analyzed. When drilled with lower power and repetition rate, a clear hole wall with very little black charred material was obtained. On the other hand, when drilled with high power and repetition rate, matrix recession and fiber protrusion were observed, also a loose coating was found covering the protruded glass fibers. The results also show that for a given repetition rate, the size of the HAZ increases with increase in average laser power. As for the effect of the pulse repetition rate, a peak value of HAZ width is reached at about 7kHz for each given laser power, and beyond which the HAZ width decreases. A novel evaluation parameter, defined as the quotient of total area of the HAZ and the profile length, is suggested to quantify the size of the laser-induced HAZ in fiber reinforced composites.