How short of a pulse can we get?

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#1

I’m interested in high density circuit boards and in order to cut and not damage the laser you need very short pulses http://www.industrial-lasers.com/articles/print/volume-27/issue-05/features/laser-drilling-high-density-printed-circuit-boards.html

any word ?


#2

If you are planning to drill through the copper layer then you should definitely research the minimum wattage that will work. Remember that the pro unit is rated at 45W.


#3

@sirus20x6, I’m assuming you want this for laser drilling of via. I think you will run into a couple of problems with the GF in this application.
First, @jkopel is correct, you will most likely have issues going through the copper layer with a 45W laser.
Secondly, you will also probably have an issue with accuracy. While the optics on the GF are great, they do not seem to be designed for micron scale alignment. For high density circuits, you need to be able to align to very small targets (usually <100um) to insure you are drilling in the correct locations.


#4

I would recommend an Othermill for quick PCB prototyping. Copper is a great mirror at 10600nm. For cutting it, you want a YAG, fiber, diode, or other laser.

That said, you can (I’m told) get some fantastic, super detailed etching by putting a resist on the material, engraving it off with the laser, then chemical engraving. That doesn’t get you holes though.


Question about metals and powder coating
#5

Does this mean you could create pcb traces on a copper clad board by putting down a resist then engraving away the negative space with the laser to expose the copper then etching the away the copper with ferric chloride? Could you do a different (but aligned) pattern for the bottom side for double sided boards? What material would you use for the resist? Would the etched away portions with exposed copper act as a mirror? Could the “mirror” damage the laser by reflecting the beam back into the emitter? Any thoughts on using the laser for solder stencils (material, accuracy, etc)?


#6

That’s exactly what some people are doing.


#7

You could probably use Kapton Tape as a resist. I’ve put that through some pretty nasty chemicals as part of an electroless nickle platting line and it didn’t deteriorate at all. I’ve never used it with ferric chloride though, so you might want to do a test piece. As for double sided, I would imagine it should work.


#8

When doing very short pulses the normal wattage rating doesnt mean much. if the laser is on for a millionth of a second it can far exceed that constant rating of 45watts but will then need some time to cool down before the next pulse.


#9

I’ve thought of that. I wonder if that will get me the detail I’m looking for. possibly


#10

Normally double sided boards would be impossible on a standard laser but the glow forge has a camera for alignment so hopefully if you print the right fiducial (alignment) marks on both sides of the material this will be possible.

The laser should be fine for making solder stencils, loads of people have done it before even on cheap Chinese lasers there is no reason to believe the glowforge won’t have the same levels of accuracy


#11

I would be interested in learning about how that works with a CO2 laser, a 1us pulse is really short! A really good xenon flash tube for instance is usually around 9us.


#12

If your material has square corners, we’ll use those as the fiducials.