Making solder paste stencil -- Print actual size - Page 1
Forum section: electronics / general

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: March 15, 2015, 10:14:32 pm
content: Hi all,Just finished my first major board design in Altium and have had the boards made by the board house. Now I am planning to make my own solder stencil using a Kapton sheet. I am wondering if there is a standard method to print the GTS Camtastic file (Top Solder layer) in its actual-size so that I can then transfer it to the Kapton. My design is done on a standard letter-size sheet (8.5" x 11") which I'm sure it recognizes, so I imagine the capability must be there. I'm just not sure how to do it.Thanks very much!Matt

author: Araho
author_rank: Regular Contributor
timestamp: March 15, 2015, 11:49:16 pm
content: I assume that depends a lot on how you're planning on making the holes in the Kapton, to be honest.I know a guy who uses standard Gerber or GCode-converted Gerbers into a cnc-based kapton knife-cutter. If you're using a lasercutter, there's probably some other standard. If you're planning on cutting it by hand (no idea if this is possible or a good idea for more fine-pitch stuff, which is where you really want the stencil), printing to actual size on a paper shouldn't be too hard. Try printing as PDF, that's usually my go-to-way if the software doesn't support it directly...

author: ajb
author_rank: Super Contributor
timestamp: March 16, 2015, 01:00:29 am
content: I export the paste layer as a PDF, including the PCB outline as a reference, pull that into Corel, and then print directly to the laser cutter. No muss, no fuss, and while I can't say I've measured the accuracy, there's no discernible error with 0603s and TSSOPs across a ~100x150mm board, which is generally the approximate envelope I'll prototype with a kapton stencil. I've done down to 0.4mm QFPs, but those are pretty much guaranteed to require some manual cleanup after reflow.

author: zapta
author_rank: Super Contributor
timestamp: March 16, 2015, 01:17:17 am
content: Quote from: The_PCB_Guy on March 15, 2015, 10:14:32 pmGTS? Don't you need the top paste layer?How do you plan to cut it after you export?

author: free_electron
author_rank: Super Contributor
timestamp: March 16, 2015, 04:43:27 am
content: You need the GTP file.Simply create a pdf file from the board (no need to go to gerber) and in the outjob select paste files.Open the pdf in ilustrator or coreldraw and off you go

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: March 16, 2015, 09:44:03 pm
content: Thanks very much everyone.First of all, yep--I meant the GTP layer, not GTS. That was my mistakeSecond, I was considering cutting it by hand with an X-ACTO knife, though I was a bit concerned about the pads on the QFN package. They are extremely fine, as you can see in the attached image.Unfortunately I do not currently have access to a laser cutter, so I am working at very low volume for now. In the past I have always hand-soldered my SMD boards, but that's not really an option now that I am using a QFN. The idea was to print out an actual-size image of the paste layer, tape it to the Kapton, then cut through the paper and the Kapton together. Again, that will still be difficult to do for the micro pins.Your suggestions are appreciated!Matt

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: March 16, 2015, 10:36:10 pm
content: Hi all, sorry for the double-post. I exported the top paste and the board outline layers to a PDF but now I am running into the same issue I ran into earlier--it's not actual size, as shown in the print preview of the print dialog (see attached image).This is what I am trying to overcome.Thanks!Matt

author: DerekG
author_rank: Frequent Contributor
timestamp: March 16, 2015, 11:58:53 pm
content: You need to choose "custom scale" on your print driver page.You need to carefully measure now much bigger (or smaller) your print out it over what it actually needs to be.You can now work out the percentage change in size as follows:needed size/actual size = "custom %" you need to apply.You may find that your print out is different in the x dimension than the y dimension. If so, you need an artwork program that can scale each printout dimension separately. If the difference in each dimension is very small, you "may" be able to average a scaling somewhere in-between.

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: March 17, 2015, 12:30:00 am
content: Quote from: DerekG on March 16, 2015, 11:58:53 pmUnfortunately I don't have a printer at my new apartment yet so I was trying to figure this out in order to print it right off as soon as I get one. Otherwise I would have worked out the percentage a long time ago

author: tautech
author_rank: Super Contributor
timestamp: March 17, 2015, 12:37:10 am
content: Ok just fired up my summer 09 version:File> Fabrication Outputs> Mask SetPrintSet printer scaling in printer properties.Each printer will have different properties, scaling, actual size etc.Experiment and measure result with calipers. Note settings for use later.Just saw your post so I'm of little help either.

author: zapta
author_rank: Super Contributor
timestamp: March 17, 2015, 02:16:30 am
content: It will be though to cut the stencil by hand. Have you considered applying the solder paste by hand or even soldering the QFN by hand (doable).Another option is to use oshstencil.com or etch your own stencil from a thin metal sheet (some use soda cans metal for this)

author: The_PCB_Guy
author_rank: Regular Contributor
timestamp: March 17, 2015, 11:19:14 pm
content: Quote from: zapta on March 17, 2015, 02:16:30 amI considered it, yes. I wasn't sure if it was the way to go though, I was afraid I might add too much solder.QuoteIn order to do that I would still need a printout of the paste layerI've also already spent a fair amount of money on t his project, so I'd rather not buy stencils, if at all possible. This is definitely more of a DIY project at the moment.