Hole Cleaning
Chemical or thermal removal of resin debris from the walls of drilled microvias ensures reliable electrical contact for subsequent plating. The process of laser desmear utilizes concentrated light energy to vaporize the resin smear left behind after blind microvia creation. This technique is especially applied in high-density interconnect designs where mechanical brushing is ineffective.
Physical Mechanism
Controlled pulse parameters allow the laser to target the epoxy resin without damaging the inner copper catch pads. During blind microvia formation, the laser drill often leaves a thin residue of melted dielectric material on the surface of the underlying copper layer. Implementing laser desmear removes this thin organic layer through photo-ablation or thermal decomposition, creating a clean metal surface for copper deposition.
This selective removal prevents the creation of high-resistance junctions in the microvia connection.
Reliability Outcome
Plating adhesion and joint reliability are the direct benefits of this advanced cleaning process. If resin residue remains on the copper pad, the plated copper will not bond properly, leading to microvia separation under thermal stress or during solder reflow. The laser desmear method improves the interface between the sputtering or chemical copper and the target pad, reducing the occurrence of latent open circuits during product operation.
Standard reliability evaluations, such as highly accelerated thermal shock testing, confirm the long-term integrity of joints treated with this approach. Electronics manufacturers use it to secure interconnect longevity.
