Laser processing techniques developed for structuring glass in PCBs
A joint project comprised of three scientific institutes and four industrial companies is underway to develop laser processing techniques for multilayer circuit boards based on thin glass. The boards should give improved functionality for aerospace technologies.
As part of the Glass PCB project, scientists in the Glass Group of the Production and Systems Department at Laser Zentrum Hannover (LZH) are working on developing two different laser processes for processing these special materials.
The first is a laser used to structure the metal layers. According to the PCB layout, a laser is used to make conducting tracks by removing excess metal from a thin glass base. The advantages of laser ablation are especially apparent in the extremely fine structural resolution of the metal, without causing damage to the sensitive material.
Secondly, a laser is used to form holes or vias to connect the different circuit board layers, or the conventional components. The LZH is currently working on finding suitable laser parameters to drill through the materials without causing thermal damage. Also, the vias should be of high quality, and be reproducible at high speeds. Optimal results aim at generating parallel vias through the glass layers.
The process time, which is dependent on the material thickness and the circuit board layout, is presently two seconds for drilling a microvia with a 0.2mm diameter through a 170µm thick material.
Also, comparative investigations carried out by project partner TU Berlin show that its highly beneficial to use a laser for drilling vias, since conventional, mechanical drilling causes unwanted microcracks, and the service life of the drills is 40 times shorter.
In the joint project, the LZH develops the laser processes for structuring the circuit board layouts and for drilling the vias, and the industrial partners such as Schott AG provide thin glass materials. The circuit board manufacturer Hotoprint offers both production processes for the thin glass circuit boards and electroplating. KCS Europe is in charge of coating technologies (sputtering) of the conducting metal layers on the thin glass. Furthermore, CCI Eurolam is involved as a specialist for materials for circuit board manufacturing. Process handling of the thin glass sheets for multilayer boards is being researched by the Institute of Transport and Automation Technology (ITA) of the University of Hannover.
The project will be funded by the Central Innovation Program SME (ZIM) of the Federal Ministry of Economics and Technology (BMWi) until the middle of 2014.