[shadow]

Hello all, long time lurker, first time poster.

I am just getting into the CNC world and have spent a few months just reading here, to get up to speed before asking any real questions. My previous experience in the electronics hobby makes the open source driver boards or particular interest to me, so hence this post to brush up on some home hobbyist PCB techniques.

In the past I have etched boards for projects, but they have been very crude. I only have an ink-jet printer without a really convenient method to get toner copies or printouts of my work. I used to make fairly simple single sided boards, using those rub-ons and a sharpie, and needless to say the quality was 'in the basement' to put it mildly. It works, but icky. I used to use the PCB express free CAD to lay out the work and then print it on some paper and use it as a reference to measure and make my traces from.

Now I'm into making some much higher quality boards that can be made in a home lab type setup. I am thinking of picking up a eBay special laser printer (any suggestions?) for toner transfer and using some fish tank parts I have around to make a vertical, heated bubbler tank for my etchant for the quickest etch times and best quality. Armed with a copy of Eagle CAD and soon a laser printer I should be well on my way, I hope.

My main questions are concerning the 'fit and finish' of homemade boards as the title suggests. What I mean by this is making the boards more commercial in appearance for aesthetics, as well as the added convenience and safety of a insulating solder mask and thru hole via inserts.

A long time ago I saw a webpage, or perhaps in one of my books even, a strip of via-like devices you could use at home. you insert them into oversize holes, and break them off the strip, then solder on both sides before component insertion, if the via is also used for a component lead. This makes 2 layer boards much more practical, especially if IC lead holes are also used as via's for side to side traces. The problem is, I haven't seen or heard of these things in awhile, not found a online retailer that seems to have them. Any leads on these little gems?

The second question is how to obtain some sort of semi translucent material (preferably green, but other colors are exciting too!) to use as the solder mask. Perhaps a lacquer of some sort can be sprayed on with one of those small airbrush guns. Something that looks as close as possible to the commercial stuff, but has some sort of easy application method at home. I had thought that perhaps for a spray on material, a 2nd toner transfer with just the pads could be placed on to mask those areas accurately. Seems the little 'toner dots' would then be fairly easily removed.

I haven't devised a theory for the silk screen, that is the white component outlines, not the silk screen method for copper etching. Of course, one might be able to use the real silk screen method, but I have no idea how that works or what equipment and supplies might be needed, nor if it will produce a good result, compatibility with the solder mask layer, etc. You don't want something that will just flake off when you touch it. Perhaps those familiar with the process of silk screen could enlighten me to the possibility, or not.

Sorry for the long ramble folks, but I'm hoping there is someone like-minded in the electronics hobby community here that can shed some light, pointers, experience, etc. I know many hobbyist types may not even think all these extra steps would be worth the trouble, but what can I say, sometimes I get carried away and can be a pain in the butt! Thanks guys.

[abasir]

1. I am thinking of picking up a eBay special laser printer (any suggestions?) for toner transfer...

2. A long time ago I saw a webpage, or perhaps in one of my books even, a strip of via-like devices you could use at home. you insert them into oversize holes, and break them off the strip, then solder on both sides before component insertion, if the via is also used for a component lead.

3. The second question is how to obtain some sort of semi translucent material (preferably green, but other colors are exciting too!) to use as the solder mask. Perhaps a lacquer of some sort can be sprayed on with one of those small airbrush guns. Something that looks as close as possible to the commercial stuff, but has some sort of easy application method at home. I had thought that perhaps for a spray on material, a 2nd toner transfer with just the pads could be placed on to mask those areas accurately. Seems the little 'toner dots' would then be fairly easily removed.

1. I'm not sure if there's a printer 'specially' made for toner transfer. Any laser printer will do, just need some trial & error to get the whole process trouble free.

2. I believe the product is Copperset. This site have it http://www.t-tech.com/materials/throughhole/ Also available at farnell.com (under the PCB section)

3. If you ever figure it out, share the method with us. I'm interested too but so far have not found a practical method

[Swede]

My own experience with toner transfer jumped to higher levels when I learned that certain brands of photo paper simply work better than others. I tried the "official" toner-transfer product, which worked OK, then learned of Jet Print.

Here's the story... http://www.5bears.com/pcb.htm

Look at the last picture, traces are 20 mil, and the octagon pads remained octagon! I think this paper is a good way to start.

Now as to masks and vias, I wish I could offer tips. There must be varnishes which would work. Perhaps an art store? How about thin, vinyl self-adhesive paper? You could work it over with a razor knife. Solder masks are definitely cool, but my main goal has always been good, solid, accurate traces and pads with no bleed-thru and no errant etching, and I think the Jet paper goes a long way.

Let us know what you find. It'd be cool if someone offered a true "home PCB" kit that didn't cost an arm and a leg, yet produced visually attractive boards.

[pminmo]

There is a pretty active Yahoo group on homebrew PCB's :

http://groups.yahoo.com/group/Homebrew_PCBs/

Some of those folks are even doing 3 and 4 layer homebrew pcb's, might be a good place to ask. If you learn anything please tell us...

Phil

[shadow]

1. I'm not sure if there's a printer 'specially' made for toner transfer. Any laser printer will do, just need some trial & error to get the whole process trouble free.

Sorry for the confusion, by "eBay special" I meant "red tag special" or "blue light special", along those lines, a bargain in other words. There are some really tiny HP's that are available at a good price, but I'm not sure if a larger machine may produce better results, and I have no idea what the memory in a LaserJet needs to be to meet the requirements of 600dpi images, or if it even matters - its not a concern with my inkjet.

2. I believe the product is Copperset. This site have it http://www.t-tech.com/materials/throughhole/ Also available at farnell.com (under the PCB section)

These are very similar although I'm not sure since they have no pictures or datasheet or anything describing the product in detail on their site. Farnell does not seem to have a decent USA based distributorship, and looking at t-tech's direct sales prices it left something to be desired. 38$ for a strip of 50 "vias" is a bit excessive I think. They also want 200 dollars for the insertion tool, yikes.

I searched some more last night and found another manufacturer of "eyelets" that have a very large USA distributor base. Keystone part #22 is a great part, sold individually, at $0.04-0.06 a piece, seems very reasonable and gets better in bulk. Mouser is where I pulled the prices, DigiKey lists them as non-stock items. Newark is the only place that carried the insertion toolset for the Keystone parts, at $400 and change, i don't think so. It is a two part die set that looks like you could make a working replica die set in 15 minutes at the lathe. Probably use a small arbor press or similar to provide the clamping pressure. Here is the catalog page from Keystone describing the eyelets and tool, the concept looks promising with a homemade tool:
http://www.keyelco.com/kec/pdfs/p88.pdf

Swede, thanks for your link, I had reviewed your CNC project before in great detail, first I have seen of the PCB page. Your site is a true asset with its wealth of information, I learned a lot there!

I have found several leads on Solder Mask. One is designed as a repair pen, manufactured by Chemtronics. It's basically like those paint pens you can buy at the art store, but apparently with a solder mask type substance in it. I plan to pick one up and test it out, if nothing else one could simply paint only the traces by such a method.

Another great resource that I had browsed before, but just rediscovered, is http://www.thinktink.com/ . They cover all aspects of board manufacture, generally they cover how some professional board houses do it, and they outline procedures on how you can duplicate these procedures in a home based shop. Apparently, solder mask is applied as a dry film and heat laminated to the boards. In my reading I did not discover how they re-exposed the underlying component pads for soldering. You can use a home version roller laminator or a pouch type laminator to apply this dry film. They also cover the 'real' way to do through hole electroplating. They sell some of the supplies for these procedures as well.

pminmo, thanks for the link to the yahoo group, I'm reading it right now. It's likely some of your boards will be my first projects using my new PCB goodies, so I'll have to pick your brain later on too. I have thought about multilayer homemade boards before, and theorized how one could stack the 'thin' PCB boards to achieve it. It would be excellent to be able to make PCBs with proper power and ground planes at home! I will need bipolar chopper drives, 2.8A/phase at hopefully >48V, 8 or 10 microsteps preferred. I've been boning up on my digital electronics and PIC reading and hope to bring -something- to the table. You guys are doing an excellent job. First time dealing with motor control, so I've also been browsing everything I can find on H bridges, steppers, current sensing, etc. I had 5 semesters on a EE degree before I was deployed and shot that all to hell.

[shadow]

http://www.t-tech.com/materials/throughhole/ <-- found more info on these!

The price of $38 seems that it must be for a box of 500, not 50. I found a website detailing these Copperset via's as well as some snap off pins made by Harwin. The site also details howto use the copperset system without a 200 dollar tool, using a Berol 0.9mm mechanical pencil and an automatic center punch. The method detailed looks more convenient and better looking than the eyelet system from Keystone. This is the original website I had seen the pictures of these devices on a few years back.
http://www.electricstuff.co.uk/pcbs.html

Found the link at the Yahoo group mentioned above.

[abasir]

For 600dpi memory requirement (full page letter size);
600x8.5" x 600x11.0" = 33660000 bits = 4Mbytes

As for soldermask, IIRC, they are silk screened with no mask on the pads; thus the pads never need to be 're-exposed'.

[fyffe555]

A few ideas to add;

To do toner transfer double sided boards it's a whole lot easier to drill *before* you do the toner transfer. Then you can iron each side seperately, holding up to the light to get the alignment. The toner will cover the edges of the holes and so the etch will affect them. Obviously you need the cnc running to do this! There's an Eagle ULP to make life easy, placing the holes, mounting points and even cut the outline.

If you have a colour laser printer then you can do the black toner transfer then toner transfer the 'silk screen' for labeling in another colour - yellow works.

To Tin the traces try Tinnit. Its a cold tinning solution, its about $6 a bag at alltronics.com and the powder makes up enough to 600sq inches of copper.

For pad masking I've tried tonertransfer of the pads again, and not removing the original toner from the pads before coating with greencoat, lacquer and a poly varnish.

Apart from being very tedious, the solvent for the pads also removed the coating. Coating safe solvents wouldn't remove the toner very well - and you had to remove the coating to get at it. All up, not a very sucessful experiment and it din't look good afterwards.

I haven't tried it but Alltronics has a peelable solder mask. http://www.allelectronics.com/cgi-bi...M-1&type=store. Looks as though you could apply it by hand to pads and then coat and then remove the mask simply by peeling it off?

As an alternative to the entire masking pads thing I've used something called Flux SK 10, it's a green board coating but also a flux that allows you to solder directly to the coated pads. No masking pads necessary. Got it ages ago from RS components, UK. haven't been able to find it here.

I've tried some of the via/through pin solutions with mixed results. Basically its expensive and a lot of effort. It's a whole lot easier and cheaper to plan for vias and through wire them.

I came to the conclusion that the time and cost for getting professional looking boards a home cost more than sending out the design to a board house.

[Al_The_Man]

A couple of sites for products I have used in the way of PCCT pins http://www.elpakco.com/catalog.html and pressed in threaded fitting www.pennfast.com
These companies supply the sockets/hardware for Opto22 board modules.
Al

[shadow]

I took a closer look at the Dry Film type of solder mask after being unable to find any consumer-level suppliers of liquid application solder mask available in the US. The film I am referring to is available at the thinktink.com website referenced above. As I mentioned before, the film is applied to the board using a heat lamination process, for small boards you can use those small pouch type laminators that people use to laminate photographs, etc.

In order to remove the dry film from pads and areas that should be exposed copper, after lamination the board is exposed to UV light with negative artwork. It is then developed in the same manner as photo resist boards, the process is identical. The process has a fairly high cost to get setup, but once you do, or if you are already set up for photo etch, the jump is a small one. I don't think there is any better way to achieve this level of result at home, unless you can find a supplier of the liquid solder mask and set up a silk screening station.

Through hole connection it looks like the Copperset devices are the cleanest and simplest method for home use, best appearance and easy application. For true through hole plating, thinktink.com also carries supplies for that process. I found out how this is done too. You have to use fiberglass laminate board for this process.

Conductive ink is spread over the board after etching and drilling. A squeegee is used to drag the ink across the board and fills in all the holes. Air is used to blow the excess ink from the holes, leaving a thin uniform coating of the ink on the hole wall. Then the PCB is placed into a copper electroplating process. This coats the hole walls with solid copper and also thickens the traces by the specified mils of copper, depending on plating time. The board most often after this process is then tinned using a chemical tinning process, but I imagine the cheaper/easier Tinnit cold tinning solution could be used as well with good results.

For silk screening the component layer, a toner transfer of a colored ink would look good I think. I have seen one site where when no solder mask is used,the black toner stands out sufficiently to use for 'silk screen' component outlines. Probably the best to get the highest quality would be to set up a silk screen and use that for your component outlines. High quality silk screen artwork I have found is done in a similar fashion to the dry film exposure method of photo PCB etching and the dry film solder mask.

All that being said, the expense of the shop setup to do the specialized tasks in this manner is moderate to high - I can probably set up the shop cheaper than I can set up the CNC thou! For small runs or where you would need same day turnaround on a board with this level of craftsmanship, it is considerably cheaper than a board house. Per board even a moderately complex process like this is still cheaper than small quantity from a manufacturer it seems. To spend this kind of money on these kinds of results you'd have to be almost as serious about your pcb's as you are about your CNC machining!

For my own boards, I think I will go to the extent of setting up a laminating and exposure system for the solder mask (can be used for photo resist too), and use the coppersets for through hole when necessary. Tinnit for trace tinning seems like the most sane option for now, I have 2 or 3 packages of it here that I have never tried before. If you design for keep all through holes off obstructed component leads, the snap-of Harwin pins are much faster than using wire to make the connection, and at a good price.

I am satisfied with the results I should be able to get with all the resources in this thread, hopefully it can help out anyone else at cnczone who would like to increase their home made boards quality and appearance. Thanks for all the input guys!

P.S. I could not find: "Greencoat", also Al_the_Man, I looked at those websites you linked but basically they, and your entire post, just confused me more than anything. I don't know what a PCCT is, or what an Opto22 is, or what to do with a pressed in threaded fitting. If you care to explain any of this, feel free, as I am at a complete loss on those topics.