With the purchase of our new Universal Laser PLS6 laser marking and etching system, I was hopeful that using the new higher power lens option we would be able to produce circuit boards directly from the laser. Using the HDPFO lens on the PLS6 we were able to mark metals directly for the first time. Unfortunately, initial investigations into cutting copper on copper-clad circuitry boards failed.
Laser marking of metals relies on an immense buildup of energy in a very fine spot on the material turning the region into a plasma that will either mark the surface or vaporize and cut through the material. Because of copper's high conductivity, as compared with other metals such as stainless steel, the energy generated by the laser is dissipated too quickly and cannot form a plasma, and thus the lasers affects are blocked by the thin film of copper on a copper-clad circuitry board.
The traditional process for making circuits on copper-clad boards involves transferring or developing a resist onto the boards surface from a printed pattern. The board is then submerged in an acid solution that dissolves the copper film except in places where the resist pattern has been deposited. The resist is then removed and the copper pattern is left. An example of this process.
Although my attempts to etch copper directly with the laser failed I thought we could improve the traditional acid etching process by using the laser to subtractively produce the etch resist patterns directly on the board. This would involve covering the entire surface of the board with a resist and then using the laser to remove the negative of the printed circuit pattern. Where the laser removed the resist the acid would also remove the copper. To test this process I coated a copper clad board with six different resist materials and tested the ability of the laser to remove each.
The materials, in the order shown: Polyurethane, Spray Acrylic, Latex Paint, Two-Part Epoxy, Cyanoacrylate, and Black Sharpie Pen.
On each 2" x 3" area of resist I then printed the following pattern of As and Bs using the settings shown in the table below. Rows A and B are identical except that I would later remove excess material from the B row by rubbing the area with alcohol to remove the fume that is left on the surface of the copper after the resist had been vaporized. Settings are in (Power, Speed, Points Per Inch).
I then chose a setting of (20, 50, 1000) from the table of As and Bs to use as a test setting for etching a sample circuit pattern on each resist area.
I then used alcohol on a half of each material to remove the fume from the printed circuit pattern.
The following two images show the most impressive results which were for alcohol washed spray acrylic and the alcohol washed polyurethane. I'll be following this post with the results of the etching process.
Continued in Part II