Laser drilling with a "mask"?

[antknee]

I'm trying to understand laser drilling with a mask. I have had some drilling done with the lasers direct focal point changing rapidly to make holes. I send a 2D CAD with 100 holes each at 20um diameter and the part returns. It appears fairly standard stuff.

Now I'm at the point that I need smaller holes <18um and lots of them >1000. They also need to be more smooth and regular because my part is intended for use in a printer. So I think I need a higher power laser and some kind of mask or focusing lens. At this point the concepts and procedure become a bit hazy. Can someone explain? And how does the cost compare?

Thanks,

Ant.

 

[LASERNINJA]

Mr. Ant

Neat application but unfortunately, out of my scope of expertise. I've contributed to this form for a little while now. Most of the topics are about heavy sheet metal stuff.

Your not being ignored just the right person hasn't read you post yet.

 

[antknee]

Thanks for the info. I've done some more reading, it appears usually laser drilling at these diameters is done with a YAG laser that fires then moves, fires then moves. The mask technique appears to use a CO2 laser that has had a lens put between it and the material. The lens works like those in a pair of glasses and alters the focal point. I could only guess that the reaso for this is that a CO2 laser has bigger beam that needs to be shrunk down to YAG sizes, but i'm not sure...

 

[MacGyverS2000]

Theoretical feature size for a CO2 laser will be the wavelength, 10.6um, though in practice it's often up to an order of magnitude larger. YAG wavelengths are an order of magnitude smaller, with the same typical caveats. The masking process is used because you can cut a large number of holes at one time.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[antknee]

I think I'm getting a better idea of the process now. I'm imagining:

1) A CO2 laser has its beam widened by a lens
2) This beam then goes selectively through a disposable mask
3) The mask consists of 10um holes drilled in it by a YAG laser.

Does that sound sensible?

And what would be mask be made of? I can think the CO2 laser would vaporise more or less anything it came across.

Regards,

Ant.

 

[IRstuff]

There's a bunch of issues with the basic concept. Your laser has a finite amount of energy, so spreading the beam over the boundary of all these holes decreases the effective power drastically, by an order of magnitude or more. what material is this? Is it really suitable for laser drilling? How thick is it? Do you care about the variance of the hole diameters from top to bottom? One picks laser processing generally because it can't be done any other way. Can you etch the holes?

Note the copper mask material here:

http://www.lightmachinery.com/masks.html

is itself chemically etched.

TTFN
faq731-376

 

[MacGyverS2000]

ant, did you read my reply?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[antknee]

MacGyver I was replying to your post and updating what I think happens. It is possible, even probable, I haven't fully understood!

It is for an atomiser/printer, so the holes need to be 10 microns diameter or thereabouts. The material is stainless that is 0.2mm thick, material and thickness can't change. A wet etch couldn't produce holes small enough, they typically have a diameter the same as the thickness, perhaps there is a more accurate way of etching, I'm not sure? I don't mind the diameter changing top to bottom face. I'm looking at the link, thanks, it is interesting to see what can be done.

Regards,

Ant.

 

[MacGyverS2000]

CO2 wavelengths are in the 10um+ range... creating features on the same order as the wavelength present serious difficulties. It's possible, but when you have access to shorter wavelengths (e.g., YAG), the benefits of using the longer wavelengths are far outweighed by the risks.

Dan - Owner

http://www.Hi-TecDesigns.com