Thanks Trampas- I experimented a lot over the years too but have slowed down somewhat in my dotage. I worked for Maxim from NC and went out west monthly- they had the real stuff ++ but monthly was too long. I was hacking around mostly with RF stuff done on an LPKF CNC board grinder which I still use- bought new in the mid 90’s and upgraded a few times. RF requires so much iteration that even a Chinese vendor doesn’t give the kind of turnaround require for a good workflow. A few boards a day is common. The boards tend to be simple, playing with some sub-circuit, etc. Sometimes on exotic substrates like Rogers- hard to get quick turn. I paid $10k for this LPKF and probably never gotten my money out of it even boards were a few hundred bucks. Its still fun- instant gratification. Regards, John M. Wettroth E: j...@mindspring.com M: (919) 349-9875 H: (984) 329-5420 From: TriEmbed <triembed-boun...@triembed.org> On Behalf Of Trampas Stern via TriEmbed Sent: Sunday, June 4, 2023 7:14 PM To: Pete soper <p...@soper.us> Cc: TriEmbed <triembed@triembed.org> Subject: Re: [TriEmbed] a full custom biz card that runs Linux I do SMT boards all the time. I order PCBs with stainless stencils from JLCPCB, www.jlcpcb.com <http://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 <mailto: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 <mailto:j...@mindspring.com> > M: (919) 349-9875 > H: (984) 329-5420 > > -----Original Message----- > From: TriEmbed <triembed-boun...@triembed.org > <mailto:triembed-boun...@triembed.org> > On Behalf Of Pete soper via TriEmbed > Sent: Sunday, June 4, 2023 12:40 PM > To: triembed@triembed.org <mailto: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 <mailto:j...@mindspring.com> >> M: (919) 349-9875 >> H: (984) 329-5420 >> >> -----Original Message----- >> From: TriEmbed <triembed-boun...@triembed.org >> <mailto: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 >> <mailto: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/ >> >> >> _______________________________________________ >> Triangle, NC Embedded Interest Group mailing list >> >> To post message: TriEmbed@triembed.org <mailto:TriEmbed@triembed.org> >> List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org >> TriEmbed web site: https://TriEmbed.org >> To unsubscribe, click link and send a blank message: >> mailto:unsubscribe-triem...@bitser.net >> <mailto:unsubscribe-triem...@bitser.net> ?subject=unsubscribe >> Searchable email archive available at >> https://www.mail-archive.com/triembed@triembed.org/ >> >> >> _______________________________________________ >> Triangle, NC Embedded Interest Group mailing list >> >> To post message: TriEmbed@triembed.org <mailto:TriEmbed@triembed.org> >> List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org >> TriEmbed web site: https://TriEmbed.org >> To unsubscribe, click link and send a blank message: >> mailto:unsubscribe-triem...@bitser.net >> <mailto:unsubscribe-triem...@bitser.net> ?subject=unsubscribe >> Searchable email archive available at >> https://www.mail-archive.com/triembed@triembed.org/ >> > _______________________________________________ > Triangle, NC Embedded Interest Group mailing list > > To post message: TriEmbed@triembed.org <mailto:TriEmbed@triembed.org> > List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org > TriEmbed web site: https://TriEmbed.org > To unsubscribe, click link and send a blank message: > mailto:unsubscribe-triem...@bitser.net > <mailto:unsubscribe-triem...@bitser.net> ?subject=unsubscribe > Searchable email archive available at > https://www.mail-archive.com/triembed@triembed.org/ > > _______________________________________________ Triangle, NC Embedded Interest Group mailing list To post message: TriEmbed@triembed.org <mailto:TriEmbed@triembed.org> List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org TriEmbed web site: https://TriEmbed.org To unsubscribe, click link and send a blank message: mailto:unsubscribe-triem...@bitser.net <mailto:unsubscribe-triem...@bitser.net> ?subject=unsubscribe Searchable email archive available at https://www.mail-archive.com/triembed@triembed.org/
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