You can always start out your SMT designs with DIY laser-cut stencils
but eventually you'll want to upgrade to a stenciling machine. Stencil machines hold the metal-cut stencil flat and taut so that you dont have any shifting or curling while you try to lay paste down. The good ones have a fixture so you can always get the same alignement every time - speeding up your stenciling time down to under a minute per PCB. They're a little expensive, but if you ever plan to do over 100 of a PCB they are essential!
Get the Right Stencil
First thing to note is that most machines are to be used with a certain type of stencil. Some require framed stencils. Others use foil (unframed) type. Framed stencils are bulky, and more expensive, but they are fast because you dont have to spend time stretching or loading them. If you have a lot of stencils already, of course look for a machine that matches what you've got. At ~$200 each its a shame to reorder them!
The stencil machine we opted for is called an STP-350 , we picked it up from Madell (most everything else there is not suggested but this machine is fairly well made and we think worth the price) For about $1350 US.
The nice thing about this machine is that it takes framed stencils, is about $1500 after shipping and has a good fixturing area. We liked that it uses 3mm holes for alignment. Many low cost stencilers require the PCB to be flat against the bed which means you can't (easily) do double-sided boards.
We get our PCB house to place 4 x 3mm holes in each corner of our PCB panel. The first time you set it up for a PCB run, you'll need to align it by loosening the 3mm studs and placing the PCB on the fixture bed. Then you can use the knobs on the side to help align it.
It takes 5-10 minutes to set up per board but once it is set up and aligned, you can just lift the stencil, place a new one so that the corner holes snap into the fixture studs and print! We've found that the corner holes almost always line up perfectly.
Last updated on 2012-07-01 at 01.00.23 AM