Post by thread:[EE] PCB traces for conductive rubber switches

Gold or conductive carbon is best. HASL will die over time. For a hobby project, maybe hack up a donor keyboard, superglue the pads in the right position on a piece of blank PCB? On Sun, Feb 5, 2012 at 8:21 AM, PICdude <spam_OUTpicdude3TakeThisOuTnarwani.org> wrote: {Quote hidden}> Anyone here knows much about these? I want to make a PCB to fit in an > existing enclosure with existing buttons, and wondering what I need to > do for the PCB side. The always seems to be black, and IIRC this is a > carbon coating...? Can I use regular HASL for this? Or will it > tarnish over time? Is there anything DIY I can do to make it > tarnish-proof? I only want to make a handful of these, so I expect > getting PCB's with non-standard coatings will be cost-prohibitive I > suspect. > > Cheers, > -Neil. > > >

Gold is a standard coating. I've never added it to a simple PCB but on more complex ones (6-layer, heavy copper, etc.) it wasn't a significant cost adder in a prototype run. I would guess that you could get 2-layer 6 inch by 6 inch gold-coated PCBs for something like $400 total for qty 2, and maybe $100 each for qty 5, $70 each for qty 10, etc. Sean On Sun, Feb 5, 2012 at 10:21 AM, PICdude <.....picdude3KILLspam@spam@narwani.org> wrote: {Quote hidden}> Anyone here knows much about these? I want to make a PCB to fit in an > existing enclosure with existing buttons, and wondering what I need to > do for the PCB side. The always seems to be black, and IIRC this is a > carbon coating...? Can I use regular HASL for this? Or will it > tarnish over time? Is there anything DIY I can do to make it > tarnish-proof? I only want to make a handful of these, so I expect > getting PCB's with non-standard coatings will be cost-prohibitive I > suspect. > > Cheers, > -Neil. > > >

> I want to make a PCB to fit in an existing enclosure with existing > buttons, and wondering what I need to do for the PCB side One project I had was to retro-fit a new PCB to existing buttons so I used low-profile tact switches. They were mounted on the back of the PCB with the legs bent upwards for soldering, so that only the very tip (about 1mm) of the actuator poked through the board. A bit labour- intensive and fiddly though > They always seems to be black, and IIRC this is a carbon coating...? http://www.coates.de/ccp/connections/carbon-inks-pcb.pdf You mind find a source for a small quantity of this ink to DIY. I'd wonder if you could try your own formulation - it's only a binder and graphite (pencil lead scrapings ?). or eg the meerest smear of silicone or contact adhesive on the PCB, dusted with graphite > Can I use regular HASL for this? Or will it tarnish over time? I'd not use bare solder as a contact surface, it soon oxidises > I expect getting PCB's with non-standard coatings will be cost- > prohibitive I suspect A jeweller (friend of a friend of a friend) gold-plated some small ball bearings for me, to be used in a novel tilt-switch. It cost only a couple of dollars when thrown in the basket with all the other jobs Jo

On 2/5/2012 10:21 AM, PICdude wrote: > Anyone here knows much about these? I want to make a PCB to fit in an > existing enclosure with existing buttons, and wondering what I need to > do for the PCB side. The always seems to be black, and IIRC this is a > carbon coating...? Can I use regular HASL for this? Or will it > tarnish over time? Is there anything DIY I can do to make it > tarnish-proof? I only want to make a handful of these, so I expect > getting PCB's with non-standard coatings will be cost-prohibitive I > suspect. > > Cheers, > -Neil. > > Something I used before is conductive paint that comes in a kit for repairing the window defogger in cars. It is a brown paint that is very conductive but doesn't tarnish . Mark

Actually, I was checking out the SeeedStudios Fusion PCB Service yesterday, basically they fit your designs on spare parts of their production boards, seems ENIG coating is only $15 more on ANY of their sizings So 10x 5x5cm boards are $10, plus $15 for ENIG - that's $2.50 each for a dual-layer gold board! (I haven't looked into the shipping yet) Didn't see a size mentioned in the original post, but Seeed could be worth a look. For Sean's 6inch x 6 inch (15cm x 15cm) it would work out as $130 - FOR 10 BOARDS! Lee Gold is a standard coating. I've never added it to a simple PCB but on more complex ones (6-layer, heavy copper, etc.) it wasn't a significant cost adder in a prototype run. I would guess that you could get 2-layer 6 inch by 6 inch gold-coated PCBs for something like $400 total for qty 2, and maybe $100 each for qty 5, $70 each for qty 10, etc. Sean ------------------------- Msg sent via Webmail - http://hosting.myob.com

Thanks for all the info on this. To answer a couple questions first, I'll be making only about 20 or so of these boards, each with one switch. The boards are ~2.5" x 1.25". I will not have donor boards to cut off the carbon switch-pad areas, but it seems I have several other ways to go about this... (1) DIM (Do-It-Myself) conductive ink/paint, either carbon, conductive window-defogger paint, or possibly silver. I'll need to investigate some of these, but so far I am able to quickly find these... http://www.2spi.com/catalog/spec_prep/Circuitworks-MicroTip-Conductive-Silver-Pen.php http://www.tedpella.com/SEMmisc_html/SEMpaint.htm#anchor1328915 (2) Have the boards gold-plated. I was expecting this to be a much more costly process, but apparently not so. I can find sources for this that would cost me ~$5 per board, which is not bad. (3) Mount a mechanical switch in there. This was my first thought, but I could not find anything that would fit easily/elegantly. But I like Joe's idea of recessing the switches. I will experiment with that. I have in the past recessed 8-pin SOIC's (DS18B20) similarly so they're thinner and both sides exposed. (4) There is one other option, which is that the rubber pads are connected to rectangular pushbuttons and apparently those pads should be removeable. Perhaps I can fit small tact switches in that space that the rubber pads occupied. Cheers, -Neil.

That does seem like a very good deal! What is their turn-time? Are they one of the panelizers/aggregators for hobbyists? I was basing my numbers from past experience with quick-turn proto shops. Just to go from their standard process to a more flexible one which allows ENIG is a significant cost. I just ran some numbers through Sunstone Circuits online quote generator. Sunstone is a proto place I've used a few times recently. They are definitely not the least expensive for simple boards but I recently have needed special specs (4 layer in one case, 2oz copper in another), and they seem to be the least costly quick turn (1 week or less) option for those cases that I could find. Specs: Soldermask both sides, silkscreen one side, 100 holes, 6 inches by 6 inches. All prices US dollars. Qty. 2 boards TinLead 1 week custom service("Full Feature") $585 3 weeks leadtime goes down to $433 5 boards, 1 week leadtime $616 10 boards 1 week leadtime $668 Qty. 2 boards ENIG (Gold) 1 week custom service("Full Feature") $738 3 weeks $550 5 boards 1 week $787 10 boards $868 Qty. 2 boards TinLead 2 day standard service("PCBexpress") $444 5 boards $534 10 boards $600 Qty. 1 board TinLead 2 weeks economy service("ValueProto")(still has soldermask and silkscreen) $133 2 boards $241 5 boards $565 On Mon, Feb 6, 2012 at 6:59 PM, Lee Mulvogue <leeKILLspambaudalign.com> wrote: {Quote hidden}> > Actually, I was checking out the SeeedStudios Fusion PCB Service > yesterday, basically they fit your designs on spare parts of their > production boards, seems ENIG coating is only $15 more on ANY of their > sizings > > So 10x 5x5cm boards are $10, plus $15 for ENIG - that's $2..50 each > for a dual-layer gold board! (I haven't looked into the shipping yet) > > Didn't see a size mentioned in the original post, but Seeed could be > worth a look. For Sean's 6inch x 6 inch (15cm x 15cm) it would work > out as $130 - FOR 10 BOARDS! > > Lee > Gold is a standard coating. I've never added it to a simple PCB but > on > more complex ones (6-layer, heavy copper, etc.) it wasn't a > significant cost adder in a prototype run. I would guess that you > could get 2-layer 6 inch by 6 inch gold-coated PCBs for something > like > $400 total for qty 2, and maybe $100 each for qty 5, $70 each for qty > 10, etc. > Sean > > ------------------------- > Msg sent via Webmail - http://hosting.myob.com/ >

One amendment to what I just said - I said Sunstone was the least costly quickturn custom-spec place that I found. I had one more requirement: domestic production. There are less expensive Chinese options which I have used in the past but for various reasons I did not want to go that route this time. On Tue, Feb 7, 2012 at 8:04 AM, Sean Breheny <.....shb7KILLspam.....cornell.edu> wrote: {Quote hidden}> That does seem like a very good deal! What is their turn-time? Are > they one of the panelizers/aggregators for hobbyists? > > I was basing my numbers from past experience with quick-turn proto > shops. Just to go from their standard process to a more flexible one > which allows ENIG is a significant cost. > > I just ran some numbers through Sunstone Circuits online quote > generator. Sunstone is a proto place I've used a few times recently. > They are definitely not the least expensive for simple boards but I > recently have needed special specs (4 layer in one case, 2oz copper in > another), and they seem to be the least costly quick turn (1 week or > less) option for those cases that I could find. > > Specs: Soldermask both sides, silkscreen one side, 100 holes, 6 inches > by 6 inches. All prices US dollars. > > Qty. 2 boards TinLead 1 week custom service("Full Feature") $585 > 3 weeks leadtime goes down to $433 > 5 boards, 1 week leadtime $616 > 10 boards 1 week leadtime $668 > > Qty. 2 boards ENIG (Gold) 1 week custom service("Full Feature") $738 > 3 weeks $550 > 5 boards 1 week $787 > 10 boards $868 > > Qty. 2 boards TinLead 2 day standard service("PCBexpress") $444 > 5 boards $534 > 10 boards $600 > > Qty. 1 board TinLead 2 weeks economy service("ValueProto")(still has > soldermask and silkscreen) $133 > 2 boards $241 > 5 boards $565 > > > > On Mon, Feb 6, 2012 at 6:59 PM, Lee Mulvogue <EraseMEleespam_OUTTakeThisOuTbaudalign.com> wrote: >> >> Actually, I was checking out the SeeedStudios Fusion PCB Service >> yesterday, basically they fit your designs on spare parts of their >> production boards, seems ENIG coating is only $15 more on ANY of their >> sizings >> >> So 10x 5x5cm boards are $10, plus $15 for ENIG - that's $2.50 each >> for a dual-layer gold board! (I haven't looked into the shipping yet) >> >> Didn't see a size mentioned in the original post, but Seeed could be >> worth a look. For Sean's 6inch x 6 inch (15cm x 15cm) it would work >> out as $130 - FOR 10 BOARDS! >> >> Lee >> Gold is a standard coating. I've never added it to a simple PCB but >> on >> more complex ones (6-layer, heavy copper, etc.) it wasn't a >> significant cost adder in a prototype run. I would guess that you >> could get 2-layer 6 inch by 6 inch gold-coated PCBs for something >> like >> $400 total for qty 2, and maybe $100 each for qty 5, $70 each for qty >> 10, etc. >> Sean >> >> ------------------------- >> Msg sent via Webmail - http://hosting.myob.com/ >> -

Saw that. Wasn't thinking free sample immediately, but where can I quickly buy a small quantity. Will check out the free sample route, but often I find it less of a hassle to pay the small price and not have to deal with their sales reps coming over and taking an hour of my time to sell me a million gallons of the stuff. Cheers, -Neil. Quoting IVP <joecolquittspam_OUTclear.net.nz>: >> conductive ink > > The pdf I linked to was for Coates. Coates are/were a big company > and had a branch in Auckland (Nielsen St IIRC). Pretty sure I > applied for a lab job there when I left school. Anyhoo, Coates/DIC > are still a big international and I'd expect you'd be able to 'sample' > enough to do this small job >

I was basing that off of Gold Phoenix proto pricing. I do don't individual protos nowadays, but rather get a large panel with a number of different protos and low-run projects. 20-ish of these would fit half the panel and they charge $100 for gold plating, so that's how I got the $5. I always veered towards domestic, until I found out that more and more domestic board houses are outsourcing to China anyway. So why let the domestic middle-man claim the savings? Cheers, -Neil. Quoting Sean Breheny <@spam@shb7KILLspamcornell.edu>: {Quote hidden}> That does seem like a very good deal! What is their turn-time? Are > they one of the panelizers/aggregators for hobbyists? > > I was basing my numbers from past experience with quick-turn proto > shops. Just to go from their standard process to a more flexible one > which allows ENIG is a significant cost. > > I just ran some numbers through Sunstone Circuits online quote > generator. Sunstone is a proto place I've used a few times recently. > They are definitely not the least expensive for simple boards but I > recently have needed special specs (4 layer in one case, 2oz copper in > another), and they seem to be the least costly quick turn (1 week or > less) option for those cases that I could find. > > Specs: Soldermask both sides, silkscreen one side, 100 holes, 6 inches > by 6 inches. All prices US dollars. > > Qty. 2 boards TinLead 1 week custom service("Full Feature") $585 > 3 weeks leadtime goes down to $433 > 5 boards, 1 week leadtime $616 > 10 boards 1 week leadtime $668 > > Qty. 2 boards ENIG (Gold) 1 week custom service("Full Feature") $738 > 3 weeks $550 > 5 boards 1 week $787 > 10 boards $868 > > Qty. 2 boards TinLead 2 day standard service("PCBexpress") $444 > 5 boards $534 > 10 boards $600 > > Qty. 1 board TinLead 2 weeks economy service("ValueProto")(still has > soldermask and silkscreen) $133 > 2 boards $241 > 5 boards $565 > > > > On Mon, Feb 6, 2012 at 6:59 PM, Lee Mulvogue <KILLspamleeKILLspambaudalign.com> wrote: >> >> Actually, I was checking out the SeeedStudios Fusion PCB Service >> yesterday, basically they fit your designs on spare parts of their >> production boards, seems ENIG coating is only $15 more on ANY of their >> sizings >> >> So 10x 5x5cm boards are $10, plus $15 for ENIG - that's $2.50 each >> for a dual-layer gold board! (I haven't looked into the shipping yet) >> >> Didn't see a size mentioned in the original post, but Seeed could be >> worth a look. For Sean's 6inch x 6 inch (15cm x 15cm) it would work >> out as $130 - FOR 10 BOARDS! >> >> Lee >> Gold is a standard coating. I've never added it to a simple PCB but >> on >> more complex ones (6-layer, heavy copper, etc.) it wasn't a >> significant cost adder in a prototype run. I would guess that you >> could get 2-layer 6 inch by 6 inch gold-coated PCBs for something >> like >> $400 total for qty 2, and maybe $100 each for qty 5, $70 each for qty >> 10, etc. >> Sean >> >> ------------------------- >> Msg sent via Webmail - http://hosting.myob.com/ >> -