DIY Solder Stencil on a DIY Laser

We use a lot of solder stencils where I work (during the day).  We usually buy stainless steel framed stencils for about $300 each.  For prototyping we usually hand paste each pad.  We have an semi-automated dispenser, but it is still tedious work.  I see several places like Pololu selling low cost mylar solder stencils.  I wondered if my Buildlog.net 2.x home made laser cutter could do it.

I researched a few blogs and pulled some information from Pololu.  Pololu sells 3mil and 4mil mylar stencils and recommended 3mil for fine pitch work.  I decided to buy the 3 mil mylar.  I picked it up on my way home from McMaster Carr.  It was a life time supply for about $15.

I found a bunch of old small SMT PCBs that I could play with.  I got the top side paste mask  gerber file for it.  I imported the file into a Gerber tool called ViewMate from Pentalogix.  This is a great program that I have be using for years.  A partially disabled version is free.  I have found that it has plenty of useful features.

 

Most PCB layout software has layers for the solder stencil.  There are industry standards (IPC) for the size of these pads, but they are generally a little smaller than the pad.  Often large pads, like thermal pads under big power ICs are divided into smaller windows or dots.  This prevents excess solder from causing problems.   With this in mind you probably need to shrink the pads even further to deal with the kerf of the laser.

ViewMate has a nice feature that allows you to shrink the apertures.   Apertures are a somewhat archaic term from when artworks were done optically on film.  They basically mean the shapes.  To use this feature select the Setup…D Codes menus.

 

Select all the shapes in the list and select the Operations…Swell menus.

Enter a negative value to shrink the shapes.

I then printed 1:1 to a PDF.

ViewMate has a lot of export options, but most of them are not available in the free version.  PDF is fine for what I needed to do.  I then imported the PDF into Corel.  I cleaned up a few extra lines and text in Corel and moved it over near the origin.

If you were always going to make your own stencils,  you could probably skip a few of these steps by defining your stencils layers with the right values.  Pololu actually shrinks it differently in X than Y for even better performance.  Many CAD programs could print straight to PDF or other formats then.

Corel is a front end for my DSP laser software, so I was ready to try making the stencil.  The PDF has vector information so you could cut it or engrave it.  Everyone seems to recommend engraving, so I gave that a try.

I was not sure what to put the mylar on.   I decided to hang it in the air.  I taped inside a wooden frame.  I tried different power levels and speeds and looked for my best result.  I onlt tried about 3 settings combinations before I ran out room.  I looked closely and they all looked pretty good.  I think I got the best at 200mm/s and about 60% power.  The power was not too much of an issue.  It seemed better to cut it with more power than it need.  It tended not to heat the surrounding area.  The step over was 0.15mm.  That probably could have been smaller for more accuracy.   There was a slight smoky haze after cutting that I rinsed off with water.

It matched up perfectly with the PCB.

 

 

 

 

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5 Responses to “DIY Solder Stencil on a DIY Laser”


  1. Matthew

    This is exciting! I was asking about this in the forums not too long ago. Have you had the opportunity to try it out?

    This application alone may convince me I need to buy/build my own laser cutter!

  2. matthew bennett

    I wonder if a vinyl cutter could also do this? Like a cheap CraftRobo or Cricut?

  3. bdring

    There is some info on Cricuts doing it. They tend to over cut the ends and have trouble with small details. There is an Instructable on doing it.

    I did this over the weekend and showed it to my production manager. I am going to make a few tweaks and try to apply some paste with it. While Ponoko recommended 0.003/0.004 thick, he likes them a little thicker.

  4. CNC Router

    CNC Router…

    [...]DIY Solder Stencil on a DIY Laser at Buildlog.Net Blog[...]…

  5. Mark

    I had good luck with this method. I did a direct PDF print/save (PDFCreator) from my soldermask gerber file and used illustrator to save to DXF… then imported it into lazycam/mach3. At 3mA at 200mm/sec I was able to achieve great detail even on high density parts. Thanks for the article Bart!

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