Glass-reinforced epoxy circuit boards (FR4) typically char when cut with a CO₂ laser. This charring may be greatly reduced by using a laser with high peak power, such as the Coherent CO₂ K2K, in conjunction with an acousto-optic modulator. G- and K-Series 9-Micron The output beam from a Coherent K2K laser was passed through an optical system consisting of an aperture, an acousto-optic modulator, an optical isolator (to eliminate back reflections from reaching the laser), and a circular polarizer. The modulator was synchronized with the laser to reduce pulse rise-and-fall times to less than 1 µsecond. The resulting output was focused by a 63-mm focal length lens. FR4 boards of 1 mm thickness were cut using multiple passes. Breakdown of the epoxy matrix was greatly reduced in comparison with standard laser cutting technology. Some darkening of the matrix occurred but charring was eliminated.

Fig. 1 - Edge of 1-mm-Thick FR4.

There is considerable variance in the exact composition of FR4 materials. Certain formulations exhibit more degradation than others when laser processing is used. The optimum process settings use very wide pulse spacing, creating an edge that is slightly serrated under magnification.

Material	Composite
Process	Cutting and Scribing Ablation-Material Removal

RSS Feeds     Legal     Terms of Sales     Purchase Order Terms and Conditions
My Coherent     Privacy     Site Map     Coherent@Home     Help

© Copyright Coherent, Inc. 2010 All Rights Reserved

WARNING: Be aware of job search related scams. Cyber scammers have been posting fraudulent job openings for Coherent on several internet job sites. These positions include acting as "Regional Representatives." These scammers ask job applicants to wire money to individuals in foreign countries. DO NOT DO SO. Coherent does not ask job applicants to wire money to anyone. If you are either the victim of this scammer or if you have received a request to send money to anyone in connection with a Coherent job, please file a formal complaint at www.IC3.gov, which is the website maintained by the Internet Crime Complaint Center, a partnership of the FBI, the National White Collar Crime Center, and Bureau of Justice Assistance.