Anyone cut Kapton before?

[Sotos Patistas]

Hello to all near and far.

I was recently contacted by a local company about cutting some stencils out of Kapton. I've never run across it before and the potential client was kind enough to send a small piece for testing. It's pretty tough stuff. I managed to cut through it, but it was pretty messy. Cleaned up OK, but not great. I'm going to give it another try, this time with a mask over it, and cutting face down to see if that helps.

In the meantime, I thought I'd ask the folks here if anyone has any tips they might offer. Here's a link to some info about the stuff: http://www2.dupont.com/Kapton/en_US/tech_info/index.html

I appreciate whatever suggestions you might offer.

Sotos

[Dan Hintz]

You can cut it with a CO2, but professionally it's typically done with a fiber laser. How thick of a piece are you working with?

[Sotos Patistas]

I haven't mic'd it, but I'd guess it's only a few thousandths thick. First pass acted like it was quite reflective, I slowed it down some and the second pass cut through, but with a fair amount of charring. Cleaned OK, but like I mentioned, not great.

This is with a 35W CO2.

[John Glowaski]

I was asked by a client to cut some Kapton that was .005" thick with my laser. I was not happy with the results. I subbed the job to a friend who did it on his vinyl plotter/cutter.
Every now an then they ask me to cut some rectangular pieces...since they are such a good customer I do it with my paper cutter.

[Scott Shepherd]

Hello to all near and far.

I was recently contacted by a local company about cutting some stencils out of Kapton. I've never run across it before and the potential client was kind enough to send a small piece for testing. It's pretty tough stuff. I managed to cut through it, but it was pretty messy. Cleaned up OK, but not great. I'm going to give it another try, this time with a mask over it, and cutting face down to see if that helps.

If the stencil is a solder mask, just use mylar. I've done a fair amount of solder masks made from .004" thick mylar. You can raster it or vector it. Cuts well, you can go REALLY small, and it's very tough material. I know they make some of those from Kapton, but my customer changed over to mylar and have been quite happy. That might not be the type of stencil you are doing, but it sounds like it, since that's a common use for that material.

[Bruce Boone]

I had some pretty thick Kapton tape when I was first proving out my fiber laser. I was seeing if it would prevent the slag that I got when lasering titanium. It was so tough that it would prevent the cut unless the wattage was way up in the thousands of watts! I stopped experimenting with it when I didn't have good results with it.

[Dan Hintz]

I had some pretty thick Kapton tape when I was first proving out my fiber laser. It was so tough that it would prevent the cut unless the wattage was way up in the thousands of watts!

1um, right? Kapton really slices & dices at UV wavelengths. Also a good wavelength for working with silver and gold.

[Bruce Boone]

Yup. 1068 or whatever the Ytterbium fiber is. I couldn't believe how tough it was to get through.

[Sotos Patistas]

Thanks for all the info and advice.

Scott, it is a stencil of sorts, not for solder but some sort of conductive paint. That's as much as I know. The client sent me several materials that they use, mylar being one, as well as Kapton.

I'll try lasering with a mask, as well as from the backside and see if that cleans up the cut any. I'll report back so that my results make it into the SMC archives in case anyone has a similar inquiry down the timeline.

[Ernie Balch]

In the flex circuit industry Kapton is usually cut with pulsed lasers like a Tripled YAG (355 nm wavelength). Pulsed CO2 lasers are also commonly used but these usually have a slightly shorter wavelength than the normal 10.6 um. This matches the absorption bands of kapton and allows cleaner cutting.

[Dan Hintz]

In the flex circuit industry Kapton is usually cut with pulsed lasers like a Tripled YAG (355 nm wavelength). Pulsed CO2 lasers are also commonly used but these usually have a slightly shorter wavelength than the normal 10.6 um. This matches the absorption bands of kapton and allows cleaner cutting.

The 355nm wavelength is the UV laser I mentioned. I believe ULS (and Epilog? Trotec?) sell 9um CO2, which should work well for Kapton.

[Ernie Balch]

Clean cutting of kapton takes a high peak power. With a 355 nm YAG and a 40 nanosecond pulse duration you get a peak power measured in kilowatts with an average power of about 1 Watt. So in this case cutting kapton is easy with a low average power.

CW lasers like my RECI glass tube are a different story, the average power might be 80 watts much higher but the peak power achieved is much lower, so cutting is not very good.

[Dan Hintz]

Here's an IR transmission spectra for Kapton... note the peaks/troughs.
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[Sotos Patistas]

Well, FWIW, I got around to running a second test on the piece of Kapton I was sent and although I may or not get the work, I must say I was pleasantly surprised. On the first test, I hit it with about as much power as I'd use to cut mylar and it took two passes to cut through, two sooty, sloppy passes, with a bit ugly kerf. For the second test, I cut from the backside (don't know if that really made a difference or not) and put some painters tape over the front side, and hit it with the amount of power I'd use to cut 1/8" birch ply. Cut through in one pass, relatively clean cut, and after removing the mask (carefully) the cut looked much better than I expected. I see a small charred band on one side of the cut if I use a magnifying glass. That may turn out to be a deal breaker, can't say. It's on its way back to the client for inspection.

Thanks again to all who offered info and insight.

[Isaac Clarke]

Mylar is fantastic stuff, this was my first ever try with the stuff. It was very forgiving :)
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[Richard Rumancik]

Isaac, didn't you get a lot of raised edges on the perimeter of each cut? I assume you were vector cutting not rastering. Way back I tried vector cutting Mylar as a test to make a stencil and I got very pronounced raised edges. With rastering I think it was better but if I recall correctly the job time was a problem.

To make a good solder paste stencil you need to generate a very smooth flat surface, with no warpage due to heat and no edge distortion. Kapton is pretty much impossible in my opinion with a normal CO2 10.6 um laser. It will char and ripple due to the heat.

[Isaac Clarke]

I think I rastered that one at full speed and it only took a few mins. Vectoring I find low power and high speed work well.

[Sotos Patistas]

Speaking of alternatives to Kapton, my client deemed my sample cut acceptable, but stated he is open to alternatives. He needs something PSA backed, somewhat rigid, somewhat flexible. The cutouts in the stencils I'm cutting can at times be on the small side, 1 to 2 inches overall length. Also, the solution they are spraying is applied at room temperature, and he stated that they may force dry with low heat, perhaps 100 degrees F.

This is an area in which I haven't done any work previously, so I appreciate those of you who have lent their expertise to the thread.

Sotos