On the quality and the accuracy of the laser direct structuring, experimental investigation and optimization

Abstract

The enormous applications of the molded interconnect devices (MID) make these face many difficult challenges, some of which are the quality and the reliability, as well as concerns on how to produce the micro-MID products. This drives to a hard competition between the different methods used in the MID technology. The laser direct structuring (LDS) has clearly been distinguished as the best method in comparison with the other MID processes. However, it also needs more development, especially in terms of the quality, accuracy, and their impact on the final MID quality of the two- (2D) and three-dimensional (3D) micro and normal products, especially with the decline or the limited availability of information in both of the industry and scientific research. In this work, the MID-LDS has been experimentally investigated by considering the effect of the important process parameters on the process responses and then to explore the relationship between these responses and the final MID quality and reliability. These experimental works were based on the design of the experimental tool, which employed a full factorial design for the LDS process parameters. They include the laser power, structuring speed, laser frequency, hatching percentage, the incident angle, and the focal length. The experiments have been performed on the polymer plates of Poly Ether Ether Ketone (PEEK) materials. During the experiments, different measurements have been implemented to find out the correlation between the adopted parameters and the 3D surface roughness, structuring percentage, structuring type, and ablation type, which are regarded as the most important features of LDS quality. Further measurements focus on the LDS accuracy and the final quality and reliability of the metallization structure, which includes the metallization thickness, the surface roughness, and the adhesion strength. The analysis of these experimental results showed that the quality and reliability, especially the adhesion strength and the surface roughness, of the final MID products are deeply related to the structuring percentage, structuring type, ablation type, and finally, the surface roughness.