anyone tried using a cheap chinese laser to make stencils - Page 1
Forum section: electronics / projects

author: daedalus
author_rank: Regular Contributor
timestamp: August 15, 2012, 03:59:35 pm
content: Hi,I have recently changed pcb vendor, and now need to source stencils for my designs separately. One thought I had was to pick up a cheap laser engraver, such ashttp://www.ebay.co.uk/itm/USB-NEW-CO2-LASER-ENGRAVING-CUTTING-MACHINE-ENGRAVER-IN-GOOD-CONDITION-o3-/130618418064Has anyone tried doing this before? Most of my boards are 0603+ sized parts, with the odd 0.5mm pitch qfn here and there, is this likely to be doable?Alternatively does anyone know a cheap UK supplier for laser cut mylar stencils? The last one set me back $70 with shipping, and Im looking for ways to reduce the leadtime / hassle involved.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: August 15, 2012, 10:00:36 pm
content: http://www.smtstencil.co.uk/

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 15, 2012, 10:22:06 pm
content: I use smtstencil.co.uk for the occasional plastic stencil, but 0.5mm is a bit marginal, especially for QFN where print quality is more critical than QFP as rework is harder.Cheapest UK source I know for stainless stencils ishttp://www.pcbtrain.co.uk/- their express service is very cheap but only offers 150 micron, which is a bit thick for 0.5mm pitch, but probably just about useable. BTW if you select their cheapest post service they still usually send by next-day courier.They do thinner stencils on their normal stencil service, at higher cost.

author: Jimmy
author_rank: Regular Contributor
timestamp: August 15, 2012, 11:16:00 pm
content: One of the guys in our group (hsbne.org) bought ahttp://www.ebay.com.au/itm/PRECISE-CO2-LASER-ENGRAVING-CUTTING-MACHINE-ENGRAVER-NEW-USB-PORT-r5-/251004109043?pt=AU_Business_Industrial_Printing_Equipment&hash=item3a7102c0f3To get it working he ripped out all the crap controler that would only run with the suppied software.Built new Front control pannel for it.He added a z axis table so you can adjust height of job to the best focal point of the lazer.Put all new optics in it.Built a cooling system for it with radiator.Duckted the smoke outside.Put air assist on it to blow debree away.I think if you want to buy a laser you will be buying yourself a project to sink money into to get it working. ALL to save a little money on postage and waiting time. How many stencils can you buy for the price of the lazer and how many are you going to make a week. If you want to make custom front pannels go for it and buy one.The Cheap laser cutter would be like usind a dot matrix printer when the fab shop uses a laser printer.

author: daedalus
author_rank: Regular Contributor
timestamp: August 16, 2012, 04:00:04 pm
content: thanks guys, I had looked at smtstencil recently, but it seems they have a broken machine at the moment, so aren't taking orders. I didn't know about pcbtrain, and with shipping taken into account its a better deal then pololu.as for the costs savings of a laser, at £52 and 6 days a stencil from pololu, it would pay for itself over 10 orders, and I design 5 boards a month that need stencils. So it does have a relatively short payback window, assuming that the output is any good. That said I have enough half-finished hobby projects right now, so as it sounds like you have to gut and rebuild the thing to get a decent output, I guess I will give up on this for now.

author: arclight
author_rank: Contributor
timestamp: August 16, 2012, 04:43:57 pm
content: I've done it successfully, using plain-old transparency sheets from the office supply store. The Mylar sheets are a bit thick for the finest pitch components (i.e. you'll end up with more solder paste on the board than you probably wanted) and they also will get hard crusty bits from the flux reacting with them if solder paste is left on for an extended period of time. But they do the job and are almost free.The main thing you need to know when cutting these out is that most laser cutters will require the highest feed rate/lowest laser setting for best results. Also, you need to reduce the size of your stencil openings to account for the "burn back" that the laser causes. I believe Kapton sheets don't have this problem. But they are also like 20X the cost.Here are two tutorials on this. Both are Eagle CAD centric, but you get the idea. I wrote the first one:http://wiki.032.la/nsl/Laser_Stencilshttp://wiki.032.la/nsl/StencilI've done down to SSOP-28 with this method (which is like 0.65mm), and the results were fine. Like any dodgy home soldering process, you should always check your components for bridges and clean if needed before testing.Cheers,Arclight

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 16, 2012, 10:17:41 pm
content: Quote from: daedalus on August 16, 2012, 04:00:04 pmThe cheap Chinese lasers need a lot of TLC and fiddling, and ideally the crap controller and software replacing. Although cheaper on the surface, how much is your time worth?Another aspect is that stencil print quality is the biggest factor in good final board quality - fine-pitch with plastic stencils will cost you some time in reworking shorted and dry pins.A tensioned stainless stencil will produce perfect QFPs all day long (placement accuracy permitting!)

author: poorchava
author_rank: Super Contributor
timestamp: August 16, 2012, 11:53:08 pm
content: i know that iTead studios offer relatively cheap smt stencils. Chemically etched ones are from $45 upwards, laser cut from $90 upwards.I've also seen some guy cutting stencils on a homemade cnc mill. Stock material was brass sheet and the tool was an ordinary engraving bit (single staight flute v-cutter).I guess as long as you don fine pitch components like 0.5mm QFP that should do. With fine pitch I think stencil thickness begins to play huge role and you won't necessarily get it right the first time.

author: Jimmy
author_rank: Regular Contributor
timestamp: August 17, 2012, 03:29:33 am
content: post a stencil file and I will see if I can have a go on the laser cutter and send it to you before you decide to invest time into it I think I got some oht sheets

author: metalphreak
author_rank: Frequent Contributor
timestamp: August 17, 2012, 08:58:57 am
content: For basic SMD stuff, you can whip up a usable stencil using some laminating sheets and a V-cutter bit on a CNC. Pictures attached are of my first attempt which was a fairly rubbish 5min job, but is still perfectly usable. OHP transparency sheets would be better as I just ran these through a laminator to get the thickness. I would love to try making some with brass or stainless steel, but I have no idea where I can get the sheet material at the right thickness?

author: GeoffS
author_rank: Unknown
timestamp: August 17, 2012, 10:58:55 am
content: Not sure what thickness stainless steel shim you need but trythese people. they have stainless down to 0.001"I have some of their brass shim material and it's very good. Not sure if they sell retail or only wholesale.

author: powermosfet
author_rank: Newbie
timestamp: August 18, 2012, 02:17:36 pm
content: Please keep in mind, documentation may be very hard to follow

author: metalphreak
author_rank: Frequent Contributor
timestamp: August 18, 2012, 06:16:11 pm
content: Mike has a good write up on his site about the cheap laser cutters. He probably didn't mention it because they aren't that great out of the boxhttp://www.electricstuff.co.uk/lasercutter.html

author: arclight
author_rank: Contributor
timestamp: August 20, 2012, 06:12:41 pm
content: Another option is the "Cricut" and similar paper stencil cutters that are sold for hobby purposes. Here is one tutorial on using these to make PCB solder paste stencils:http://code.google.com/p/opendous/wiki/SolderPasteStencilsArclightQuote from: metalphreak on August 18, 2012, 06:16:11 pm

author: mamalala
author_rank: Unknown
timestamp: August 20, 2012, 09:24:08 pm
content: You can make a stencil rather easily using the photo method.Get some Tenting-Resist. This is photosensitive laminate that you apply to PCB's usually. (Tenting is the name i know, i guess it comes under different names as well). Apply that to some thin steel or brass sheet, using one of the laminating machines that you use to laminate paper, cards, etc. Must be a "hot laminate" type, not the cold one.Get a "real" film of your stencil layout from a DTP shop or similar. Expose the laminated steel/brass sheet, develop, and then etch. You have to laminate the sheet on both sides, but only expose & develop one side. After etching, strip off the laminate. There's your stencil now.You need to work under yellow light, since the laminate is highly sensitive. You can also get pre-sensitized steel & brass sheets here:http://www.renaelectronics.com/product_stencil.htmGreetings,Chris

author: CLC
author_rank: Newbie
timestamp: January 16, 2013, 03:38:49 pm
content: Hi there not sure if you are still looking but I have a CO2 laser that I use to cut mylar stencils. Predominantly cut 125 and 190 micron but can get other thicknesses as well. If you are still looking pls let me know and we can discuss further. I am UK based for ease of postage!Kind RegardsJulie