I do SMT boards all the time. I order PCBs with stainless stencils from
JLCPCB, www.jlcpcb.com. I normally order 4-6 layer double sided boards. 10
boards with two stencils are around $50. Then shipping to US is $50. I
normally get boards in about 7-10 days
I use a stencil printer from NeoDen, then use Manncorp pick and place
machine to place the 'jelly bean' parts. Then hand place other parts.
After which I use a custom made reflow oven.
I have tried countless stencil printers and reflow methods and ovens, and
soldering irons,etc. As such if anyone has questions I can help answer them.
Trampas
On Sun, Jun 4, 2023, 4:43 PM Pete soper via TriEmbed <triembed@triembed.org>
wrote:
> Wow, John. It never occurred to me to turn solder paste into "solder
> paint"! Does that really work for you for .5mm centered QFNs?
>
> Pete
>
> On 6/4/23 14:01, John Wettroth wrote:
> > I think everyone experiments with SMT assembly to get to something that
> works. I used a little Chinese clone pneumatic dispenser that pushed out
> paste through a blunt needle- its fine for small board if you can pull an
> airline into your lab. The only designator is 983A, it must be a copy of
> something made by Hakko or Plato, etc.- I still use it but its only suited
> for really simple boards. Hitting pads on a 300 pin BGA or a few hundred
> R's and C's is no fun. Metal stencils are the way to go, they work so
> well- plastic does work but past can go under them pretty easily. The only
> problem I have now is keeping solder paste from going bad and turning to
> concrete. I have a little beer fridge in my lab and keep it in there which
> help. I bring it up to room temp and if its too stiff, add a little
> Isopropyl- I don't go strictly by the expire dates- I can use it for 2
> years or so though it might expire at 6 mos. You can also put a little bit
> of liquid flux in it to liven it up. It fails somewhat gracefully, you can
> do a test run and see if it will reflow without committing a bunch of
> boards.
> >
> > I guess the original point of that post is the guy built a Linux box on
> a biz car- that's pretty cool. I jumped to your stencil comment.
> >
> > Regards,
> > John M. Wettroth
> > E: j...@mindspring.com
> > M: (919) 349-9875
> > H: (984) 329-5420
> >
> > -----Original Message-----
> > From: TriEmbed <triembed-boun...@triembed.org> On Behalf Of Pete soper
> via TriEmbed
> > Sent: Sunday, June 4, 2023 12:40 PM
> > To: triembed@triembed.org
> > Subject: Re: [TriEmbed] a full custom biz card that runs Linux
> >
> > About 10 years ago OSH Stencils started out selling stencils made of
> > kapton. The kapton came on rolls and there was curvature in the stencils
> > such that 80% of the hassle of applying paste was holding the stencil
> > down as flat as possible. For fine pitch parts it was a serious PITA. I
> > was told kapton was used because it would cut cleanly. After Matt
> > (owner) had shipped a zillion kapton stencils he could afford a serious
> > laser cutter to offer stainless steel. For me this was a cause for major
> > celebration. The time with the kapton was when stainless steel stencils
> > from other sources were expensive. Now they are cheap, as you noted
> > John. A lot of the stencils I get from Matt are $10. A hobbyist might
> > flinch at this cost, but IMO it's a small price to pay for the ability
> > to actually assemble a board vs imagining that one can do it by manually
> > putting paste to board. One can't actually manually put paste to board
> > reliably for small parts. :-) Again, my focus is on small pitch parts as
> > these have become a fact of life and avoiding them imposes a very heavy
> > constraint on design. I'm preparing to make a flexible board for a
> > sensor that has 10 pads around it's sides underneath and is 1.8x2.0mm
> > overall. That takes a good stencil. :-)
> >
> > A plastic that is dead flat to begin with and that doesn't go bonkers
> > with a laser (i.e. that can be cut cleanly without the edges swelling)
> > would IMO make for a cottage industry for somebody because they could
> > beat the stainless steel prices and perhaps offer comparable quality
> > results. But I'd have to see such a plastic stencil under my microscope
> > to be convinced that it can actually compete with stainless steel. My
> > 'scope has a very good camera and I'd be happy to take pictures to share
> > with the group so we could see what the apertures look like close up.
> > ("Aperture" is the 50 cent term for the mostly square corner holes in a
> > stencil.)
> >
> > Pete
> >
> > On 6/4/23 08:09, John Wettroth via TriEmbed wrote:
> >> I've played with this with standard transparency film and a little 40w
> Chinese
> >> laser- takes a bit of tuning to get it all correct but works. Stencils
> are
> >> really cheap when you order a board if you remember.
> >>
> >> Regards,
> >> John M. Wettroth
> >> E: j...@mindspring.com
> >> M: (919) 349-9875
> >> H: (984) 329-5420
> >>
> >> -----Original Message-----
> >> From: TriEmbed <triembed-boun...@triembed.org> On Behalf Of Pete soper
> via
> >> TriEmbed
> >> Sent: Saturday, June 3, 2023 1:51 PM
> >> To: Triangle Embedded Interest Group <triembed@triembed.org>
> >> Subject: [TriEmbed] a full custom biz card that runs Linux
> >>
> >> He made his solder stencil with a laser cutter and the BOM runs around
> $3.
> >>
> >>
> https://www.thirtythreeforty.net/posts/2019/12/my-business-card-runs-linux/
> >>
> >>
> >> _______________________________________________
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