Anyone here have experience with laser engravers? (5/21/09: Success with Kapton
Phil Pilgrim (PhiPi)
Posts: 23,514
I'm considering the acquisition of a laser engraver. One requisite application will be cutting out polyester solder paste masks; but it's one of those items whose applications will multiply, once in possession, I'm sure.
So, for those of you who have actual hands-on experience with these machines (hyposthesizers, pontificators, and conjecturers need not reply), any recommendations? Any ones to stay away from?
My budget is in the $5K ballpark.
Thanks,
-Phil
Post Edited (Phil Pilgrim (PhiPi)) : 5/21/2009 10:59:26 PM GMT
So, for those of you who have actual hands-on experience with these machines (hyposthesizers, pontificators, and conjecturers need not reply), any recommendations? Any ones to stay away from?
My budget is in the $5K ballpark.
Thanks,
-Phil
Post Edited (Phil Pilgrim (PhiPi)) : 5/21/2009 10:59:26 PM GMT
Comments
Although I don't have first hand experience, I do know of someone who supplies us with kapton stencils from a laser (the engraver type).
check out www.ohararp.com
He is a good friend, and can help you out. He knows a lot about the engravers.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Through all of my research, testing, communication, etc, I was very happy with the results with the 3 different Epilog lasers I used. Some of the sample products at the reps shop were amazing. Unfortunately, I could never justify the cost for the need at hand, so I am still without one. (which is why the radios are done by the trophy engraver...)
Epilog sells demo units 2 times a year, so you can get them at a very good price if you time it right. The Mini 24 was actually available for purchase while I was using it at ~85% of new cost. Here's what used machines he has now for example: www.aceslasers.com/usedsystems.htm
Check on Epilog's website to see if they have a local rep or anyone local that owns a machine and is willing to do a personal demo. They were pretty honest with how accurate the machine specs were in practical usage. Plus, getting an "owner" give you a demo is very helpful. Also, request their info kit.
Another thing I liked is that it worked like a printer. I already used CorelDraw, so for all of my research, it was very easy to create multiple test images to challenge the laser. I never was able to find a clean solution for converting the gerber data into a format that could be transferred straight to the Epilog. I just ended up created the patterns in Corel from scratch since I could navigate in Corel so quickly.
I'll post a second response with more details on my stencil making research..... good luck!
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Andrew Williams
WBA Consulting
IT / Web / PCB / Audio
Post Edited (WBA Consulting) : 3/28/2009 8:22:39 AM GMT
Through several tests and various materials, I determined that it was very possible, but very cumbersome in determining the right settings. Once you get the settings dialed in, it should be reasonably smooth sailing.
Materials I tried were (all films were purchased from McMaster):
5 mil Kapton (Polyimide)
2mil Black Cirlex Polyimide
5 mil Static dissipative PET (polyester "mylar")
5 mil Fluoropolymer PFA Film
5 mil Ultra-High Molecular Weight Polyethylene (UHMW) Film
A piece of clear Avery sheet protector material (don't remember the thickness, but about 4 mil)
A sheet of plain cardstock
The 5 mil Kapton proved to be the best material to produce a stencil that could be used several times. Pretty good paste release as well. The 2mil Black Cirlex Polyimide had good results, but I think the fact I used 2 mil in my testing brought it lower than the Kapton. (that was the thickest that McMaster carries)All other materials would work, but with several pitfalls. If you are only using SOIC and 0805 parts, cardstock would actually be fine for a single print.
Through my research I had Pololu (www.pololu.com/catalog/product/446 cut me a stencil from mylar. Unfortunately, I was not impressed. For a quick turn 1 shot proto, it would be justifiable, but the edges of the apertures are not square or clean so fine pitch prints horribly. Mylar does not work well with a CO2 laser for very small cuts. The amount of heat generated by the laser even at low power or fast speed rates is still too much for a clean cut on mylar.
I also requested a sample from BEST of their stencilquik stencils.
www.solder.net/stencilquik/default.asp The stencil has a patent number lasered into it and the patent document has some good details.
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Andrew Williams
WBA Consulting
IT / Web / PCB / Audio
He uses Mylar, I used them for producing my PropGFX boards and I can recommend them (as long as you look after them that is)
Mylar is ok for what I am doing, it had no problem coping with the LQFP packaging of the Prop
Coley
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PropGFX - The home of the Hybrid Development System and PropGFX Lite
Post Edited (Coley) : 3/28/2009 11:33:33 AM GMT
-Phil
If you are not trying to cut dense material, for 5k you may consider geting a new CNC machine, then add a laser diode component for burning thin film like you are discussing. This way you have a multi-use system.
75 watts sounds like a pretty high-end system. Any idea what that unit will do that, say, a 40- or 25-watter can't?
-Phil
It's (the predecessor to) this one:
http://www.synrad.com/fenix/index.htm
If you want me to do a test burn on something, let me know. If it's something I've not got to hand, post me a sample...
Steve
No I was suggesting a laser diode which would be easy to attahed and remove. I see guys cutting lots of thin stuff with standard DVD-RW diodes. You could easily find a speed that would work on thin polyester/mylar. But like you said if your machine xy is too small then you need a bigger machine. But, you could get a CNC for much less than 5k and the diode is dirt cheap.
The 75watter will cut .5" plexy slowly, not too clean though, .25" plexy cuts great. It will cut .25" wood nicely too. More wattage = more depth, faster cutting, cutting harder materials.
www.youtube.com/watch?v=B2mEpnogUMI
www.youtube.com/watch?v=ndWSe8uk_vc
Post Edited (TChapman) : 3/28/2009 9:07:41 PM GMT
One consideration that is not mentioned here is beam width. If you plan to cut any stencil with fine small apertures you will need lens that will give you a finer point (drawback, the beam widens faster, not good for thick material).
The Epilog has lenses for such purpose, but I'm not sure about the knock offs from China.
Also, unless staying with pretty large footprints, plan on investing in some Kapton. It is humidity sensitive, but doesn't give the "flash" left over from the cutting process.
We use a lot of kapton stencils, and have found them good after 200 boards or so. We do have to watch how we store them, and the humidity they are exposed to when using them.
For fine pitch (LQFP) we use stainless only. It is the best way to go. Rework really sucks.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
My main interest in the solder stencils is for short-term prototyping rather than production runs. Frankly, I've just about had it with clogged fine-tipped syringes! I've looked at some of the Chinese knockoffs on eBay. One site comes with several detailed videos regarding mirror alignment, grounding, and watercooling (using a five-gallon bucket!). This all seems a bit half-a**ed and prone to maladjustment, but the price is down around $1600. On the flipside econonomically, middle-of-the-line Epilogs go for about $15K. That buys a LOT of solder stencils from service bureaus and is WAY above my budget. So this is one purchase I may end up putting off for awhile. :-(
-Phil
Within the past month or so I began looking for a laser cutter/engraver for the exact same reason! While dealing with prototypes, it seemed like my syringes would constantly clog... maybe the paste is just getting old. On the other hand, for production pieces, I can apply the same paste very easily using a squeegee and stencil. So, I began looking for a way to make my own stencils in-house.
I, like you, don't really want to invest money in a foreign knockoff laser cutter. Consequently, I can't independently afford $15K either.
As I was browsing Instructables one day, I came across an interesting article:
www.instructables.com/id/Create_Solder_Paste_Stencils_with_Cricut/
The author found a way to use a small, hobbyist "vinyl/craft" CNC cutter and some proprietary software to make stencils quickly. The only consumables are the machine's blades and the cutting mats; both of which aren't too expensive. It looks rather intriguing, especially since the author claims the stencils are precise enough to use with 0805 and TQFP components.
I recently purchased a Cricut machine on eBay for about $75 shipped. This particular machine can't cut an area greater than 5.5" x 11", but that's okay: my boards are usually 4" x 6" anyway. I'll let you know how it goes once it arrives and I make a few stencils.
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-Paul
'Funny you should mention this. I've got a vinyl cutter, but I'm afraid mine, at least, would be a pain for this app. Many of my boards use fine-pitch (0.5mm) components. While the machine is theroetically capable of this resolution and has enough knife pressure to cut polyester, in practice holes this small tend not to be very cleanly cut, and the requisite "weeding" and "hanging chads" are a constant headache.
I'm nonetheless very interested in your experience with the Cricut machine! Thanks for the feedback!
-Phil
-Phil
All in all I am very happy with my purchase. I do my stuff in a part time role and like many of you got fed up with expensive stencils. I sell the stencils as a courtesy to developers and hobbiests who want a high quality and inexpensive alternative to others out there. I offer a $25 flat rate pricing (competitiors offer ~$25 as a starting price) and allow you to "panelize" the 8.5x11" area if you have multiple designs at no cost (I only require the multi designs to be in one file). I usually ship in 1 business day and on Saturdays as well (at no extra cost). Basically, if you send me the stencil before I get home from work, you'll have it in the mail the next day. James Long of www.lil-brother.com uses our stencils on his automatic pick and place machine all the time. He has made runs of over 100 panels using our 3 mil kapton stencils!
If you all ever have any questions about lasers, stencils, or smd reflowing (on the cheap) feel free to drop me a line.
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Regards, Ryan O'Hara
Check out our $20 SMT Stencils!!!
www.ohararp.com/Stencils.html
Your pricing is excellent; much cheaper than all of the alternatives. I know I, for one, will be in touch once I require more production quality stencils.
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-Paul
Got to love Ryan, he just express mailed me two stencils for a dual sided job I need to assemble before the weekend.
We really do use his stencils a lot, so he has some experience. We only have 4 metal stencils, and have assembled many boards since our opening last year.
If you have used Mylar, you will definitely like Kapton. No flash, and the apertures can get pretty small, just watch the moisture.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
I don’t know if you’re still interested (given ohararp above provides reasonably priced Kapton stencils already)….
Anyways – I recently purchase one of those $1000 from china laser engravers for cutting my own Kapton stencils. I managed to have it generate a decent stencil for a 1mm pad on 1.2mm centers.
This first thing to check is if the software and engraver you choose is capable of executing a ‘cut’. That is you can turn on (and keep on) the laser while moving the focusing head.
The trouble I had was the MoshiDraw software that came with the engraver, converted the vector lines I specified into a raster image. That is, instead of cutting a clean line the engraver tried to build up a line by burning a series of dots in a raster image. It’s very similar to printing out line graphics with a low resolution dot matrix printer. Good for engraving ‘happy birthday’ but not so great for <1mm feature stencils.
It turns out in my case, that the MoshiDraw software had a feature to ‘cut’ the outline of the area to be engraved. I managed to sniff the data protocol on the parallel port and reverse engineered the “cut a square” command. So for my masks I cut a series of really small squares in two layers of 5 mil kapton.
I was going to try sniffing more of the protocol to see if the controller board inside my engraver can do circle cuts but I’m not hopeful…. So for now squares/rectangles will have to do.
Jeff
That's good info. A raster-only engraver woudln't be of much use, unless you can hack it somehow to do vector work. What has been your experience with:
1. Spot size and spot size uniformity.
2. Mirror alignment/misalignment.
3. Cooling.
4. Ventilation.
I agree: it would be hard to beat Ryan's $25 Kapton stencil deal. $15K buys a lot of stencils at that price! I sent him a Gerber for a fine-pitch design that's a real pain to paste with a syringe, and I look forward to reporting back here about my experiences with it.
-Phil
I have yet to try creating smaller aperatures. I'd like to do stencils for 0.4mm pitch FPBGA's and 0.5mm pitch TQFP's.
So far I've used it to make an 15 by 13 array of 1mm aperatures at 1.2mm pitch. So the remaining bit of Kapton is
only 0.2mm wide. It actually generates little 1mm squares. The engraver uses stepper motors so it's not fast but it seems very controllable. The engraver will accept positioning commands to roughly 1/16th of a mm. The program I wrote keeps track of the
cumulative positioning offsets to 1/256th of a mm and will tweak the positioning commands to keep the positioning error to a minimum. ie For my 15 by 13 array the 15th hole over still lines up.
The Canadian reseller may have aligned the mirrors before I got it but when it arrived the unit just worked. The MoshiDraw
software that came with the engraver was royal pain in the rear.
For cooling I use a 5 liter (pint) container of distilled water and a aquarium pump that I bought. Most of the time the laser head
is positioning on the work piece so the actual time the laser is firing is perhaps %20.
Ventilation. I run my laser out in my garage so I switched out the bathroom vent fan (yes I'm serious) that came with the engraver
and patched together a hook up to my shop vac vacuum. I then put a HEPA filter in the shop vac. No smell as far as I can tell.
I added a aquarium air pump to the setup and used the 1/4" aquarium air hose to mount an gentle air jet on the focusing head.
It helps to bump any soot away from the optics and towards the exhaust intake inside the engraver.
Jeff
@Phil, your stencil should be arriving in the mail if it hasn't already. I believe I sent it out last Thursday. Please let the group know how things come along with this sample.
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Regards, Ryan O'Hara
Check out our $25 SMT Stencils!!!
www.ohararp.com/Stencils.html
-Phil
We use plastic putty knives for small stencils (like you patch dry wall with), and a metal stencil squeegee for large ones. You could also use metal putty knives, it's all about the same. Just make sure the corners are not sharp. they will tend to "cut" the stencil if they are.
Both work well, just make sure to clean them well after. Denatured alcohol works well.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
-Phil
In order to use the mask, I constructed an alignment frame from some scrap 1/16" FR4. That way, each board I pasted would align properly with the mask. I then put a small piece of double-stick tape on the frame's platform to keep the board from shifting during pasting. Next, I trimmed and positioned the mask over the board, so it lined up, and taped the mask to the frame, forming a hinge:
Just to see how well I could do pasting (not having my ducks quite in a row component-wise), I spluged a bead of paste onto the frame end of the mask and, with a credit card, drew it across the mask. Here are the results I got:
····1. The smaller pads pasted quite well on the first pass.
····2. The larger pads pasted incompletely, even after a second and third pass. The squeegee seemed to lay down the paste, then pull it back up again, leaving paste only in the down-pass side of the aperture where it could pile up against the edge.
····3. After doing this, the pads seemed rather heavily pasted with bridges between some of the closer ones.
····4. So I wiped the board clean and decided to try a single pass and to paste the larger pads by hand with the syringe. I still got too much paste on the board, though.
I'm sure these difficulties have nothing to do with the mask itself and more to do with my inexperience. Some possible gremlins:
····1. The squeegee. Maybe something made from Teflon or another non-stick substance would help with the "pulling-up" problem.
····2. The solder paste. Too thick, maybe? Can it be thinned? Wrong kind for squeegeeing (it came from the syringe that I've been using)?
····3. The mask for the large pads. Perhaps I should've designed these as a grid of smaller apertures.
····4. Technique.
-Phil
Post Edited (Phil Pilgrim (PhiPi)) : 4/7/2009 1:32:16 AM GMT
Since we deal with paste a lot, I'll try to possibly answer some of the possibilities.
Your apertures look fine. No problems there.
The sharp edge of the card may cause the paste to pull back up, but doubtful.
Try rounding the edge, and pull again. If it stay's put, the answer is evident.
I vote for the paste being too thick. The correct viscosity paste will "roll" in front of the squeegee. If it doesn't roll at about 30 degree angle (from flat surface to squeegee), it is too thick. The only material you can thin with is flux. Not any flux, but the flux in the solder paste. I know where you can buy no-clean solder flux if you need some. It comes in a syringe. (Solder and More).......they are on the net. It may not be the exact flux, but I know it works, we thin ours when needed.
There is some technique involved. The first thing I suggest is put about 10X more solder than you'll ever need (when you think it is enough, then double it). If you put a little dot, it makes it much harder. More is better, in this case. When your done, just put back the excess. (I didn't really say that.......but you can).
Also, you will find, that perfection is not needed for most items. There are going to be times bridging of the solder paste will happen, but after reflow the pins will "wick up" the solder and you will not have bridges.
I personally would have slapped that board together and have it baked already (just like you pasted it).
Just for reference, when cleaning the stencil, try to pick a material that doesn't leave fuzz. If you clean with a material that does, you will hate yourself the next time you use that stencil. All those little apertures will be "webbed" with fuzz, and cause improper flow through.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
-Phil
Hey, now that is a tip I can use. !!
Thanks,
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Laser engraver would be cool for other things though. So would a 3d printer but I am broke at the moment.
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