Hi Bob-
I guess you're imagining that because you can tolerate a bit more production time and setup time, you might be able to get a "high quality" stencil printer. Unfortunately, the "high quality" feature you're looking for is where most of the cost is!
It isn't terribly difficult to put a pcb on a static mat, carefully align a stencil in a frame on it, and while "clamping" the stencil with one hand, use a sharp putty knife to mash the paste through with the other hand. I've seen high skill level techs turn out pretty high resolution work that way.
Since you mention that you will be doing several of the same pcb, it would be nice to have a repeatable way of maintaining alignment. That isn't real hard either--just use a couple of hinges to hold the stencil (if the hinges are loose, mis-align them a bit so they work against each other). Tape some thin alignment strips to the static mat so you can repeatably place the board under it. Getting initial alignment correct will be very annoying, but if you've got the time it can certainly be done.
If you want easier alignment, that requires a stage with x, y, and theta adjustments. That costs more. Find the backlash in the cheap adjusters annoying? If so, you'll need to design some anti-backlash into it. Manual squeegee operation unpleasant? Add a squeegee holder on rails. Did you want a power drive on the stencil? Vacuum hold down of the pcb?
Will there be parts on both sizes of these boards? That means you'll have to design a "nest". You'll also probably want a reasonable way to adjust stencil height.
Get my drift? The problems outlined above can all be "solved" cheaply, but the result will probably not meet your "high quality" requirement.
OR, you can let someone else add solidified solder deposits to your bare boards, and pre-apply flux:
http://www.stentech.com/092~SIPAD_Products/
I ran an R&D lab a few years ago, and this worked very well for us. At that time, the company offering it was SIPAD, but I guess they've sold to other organizations. Anyway, the concept is that they put the solder deposits down for you, and flatten them and add flux so that all you have to do is peel off some wax paper and place parts. Solder paste is a miserable material to work with, especially toxic if it contains Pb, so I was very happy with someone else handling that mess.
I found that since the paste was already reflowed on these boards, the solder joint quality was much higher when reflowed with my parts on top. I could reliably drop the reflow temperature nearly 10C and still get gorgeous joints.
Dual sided boards are a bit of a problem with this technique because the second side deposits "dome" when the first side components are soldered. We deliberately put our highest resolution parts on the first side.
Wayne Thayer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Cochran
Sent: Thursday, June 08, 2017 3:42 PM
To: [log in to unmask]
Subject: [TN] seeking recommendations for a manual stencil printer...
Hi,
We want to bring in house a high quality, low cost manual stencil printer for prototyping / reflowing several of the same PCB in a batch run.
There are many, many models out there to choose from, but the specifications seem to be limited.
If you can recommend one, please do so. And if there are ones to stay away from, then please share this, too.
Thank you,
Bob Cochran
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Robert E. Cochran
Mind Chasers Inc.
https://mindchasers.com
297 Route 72 W, Suite 35-315
Manahawkin, NJ 08050
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