Homemade PCB: Via advice

That'll work just fine... but why are you doing it? The places I've gone to for PC fabrication always plate-through the holes, so I get vias whether I want them or not.

It should work fine. Lot's of kits have boards you have to do this with. It is cheaper to make them this way so it keeps the kit prices down.

tim

It works, although few people bother with do it yourself board making today. The gear you need to make good boards at today's pin densities costs more than you'll save.

There are services that make boards for about $50, so home-making PCB boards just isn't worth it any more. Double-sided plated through is now the low end of PC boards.

There used to be special through-hole rivets for making vias, but that, too, is a dead technology.

John Nagle

Well, you're in for a rough go, when you put IC's into those holes. You'll have to solder both the top and the bottom. It's very hard to solder the top pins of an IC with it cover over half the holes. You have to heat both the pad and the pin at the same time, or you'll have weak, cold, or no solder connection.

Essentially you'll have two, one-sided PCB's. The pads lift easily from either side without the metal plated through the hole. Reliability isn't good, as mechanical forces will tend to break the connection from one of the sides, by working against the other.

It can be done. It really isn't worth doing, other than for the experience. Remember, experience is what you get, when you don't get what you want.

everything to make your own pcbs at home:

eyelets to make double side pcb vias

bruno

Only if each pin has to be soldered at both top and bottom, which is kind of an unusual requirement.

The only problem is that you cannot place such vias under components, since solder joint will be in the way.

When making a double side board without through plating, you must also remember that some components cannot be soldered on the top side. If you forget, you may, for example, when selecting IC sockets, have to get the more expensive ones with turned pins.

I used to make my own PCBs and did this - it works fine. Here's a tip: take a length of wire, around 12 or 18 inches or so, strip off all the insulation, then weave it through all your "vias" without cutting. Then solder top and bottom. THEN clip the wire next to all the vias to finish up. Soldering the one long segment in several places is much easier than soldering many very short segments.

But ... I must say that I don't make PCBs myself any more when I can get them made professionally for so cheaply at much higher quality than I could ever hope to make myself.

-Brian

[snip]

Brian,

Don't leave us in suspense. Tell us which service you use for prototype boards.

Thanks,

Jeff.

I'm not Brian, but I've used expresspcb.com for a couple of projects. They have downloadable no-cost design software, and for $51 plus shipping (I think it comes to a total of about $70) you get three

3.8x2.5 inch (exactly -- not larger, not smaller) double-sided boards with through-plated vias. No solder mask.

They also have a variety of other services, like 4-layer boards, silkscreen and solder mask layers, for more money.

The only thing I don't like about them is they're one of the two reasons I have to keep Windows around.

Yes, rolling your own is cheaper.

The turnaround time for the company I mentioned earlier (let me mention I'm not affliliated with the company in any way; I've just bought some boards from them) is two days (the only way the ship is FedEx); this is nothing compared to the design time.

And my home-made PCBs, decades ago, were complete and utter crap. I was never able to get the etchant to take all the copper off before it started eating through the resist.

I've seen people make good ones, and my hat is off to you if you can get it right!

I'll agree with everything you say here.

Compared to a commercial service, making it yourself still makes sense for a hobbyist in terms of both time and dollars. Turn-around is about an hour, compared to easily a full week or more. Materials and consumables for that size board cost about $2 each. Plated holes are possible, but startup cost is likely prohibitive: roughly $150 in equipment, ink, and electrolyte. Solder and paste masks are also possible, but startup cost is even more prohibitive, unless you already happen to have a laser cutter.

Compared to breadboarding, custom PCBs, especially homemade ones, can still make sense. The time and effort to run error-prone and noisy jumpers is roughly the same as preparing and etching the board. The PCB loses out if you want to make a quick change after the fact. OTOH, breadboarding isn't possible if you want to use even one surface mount part.

I've used both Advanced Circuits

and Imagineering for prototypes. Both are execellent and the costs are very reasonable. What I really like about these services is that they offer a "prototype" service where if your board conforms to a reasonable set of common specs, you can get them done for a very economical price. This typically applies to

2-layer, silkscreen, plated through holes, reasonable board size, and up to 2 oz copper. I've made a few boards that I couldn't use that service on, but the bulk of the boards I've done match the specs of their prototype special service.

Also, another great feature is that they both have an on-line quoting service - enter the specs, and then get pricing on various quantities

- so you know right away what you are getting into with regard to price. No submitting engineering files and waiting around for someone to get back to you. Other services do this also, but the above two are the ones that I have direct experience with. Turn-around is about a week in each case for protos. You can get them faster, of course, but the price generally goes up exponentially all the way to same day turn around.

Regarding DIY PCBs, I've done the toner transfer method with mixed artwork results as well as using photo sensitive boards and exposing with light, fixing chemicals, etc, with execellent artwork results. I've done both single-sided and double-sided. I found the photographic method to be far superior than the laser printer toner transfer, though a bit messier. In both cases, once you prepare the materials, apply the artwork circuit to the copper clad board, expose/heat, etc, then etch, and cleanup. Note that doing a double sided board is doubly hard because you need to ensure good alignment and you also have the through-hole problem. Don't forget you now need to drill all those holes (not so easy) and then somehow deal with through-holes (eyelets are extremely tedious and only work so-so). After all that, you can use up the better part of a perfectly good day. And even after all that, the results (at best) were marginal - nothing to write home about, and in some cases, the board has to be scrapped due to process problems.

For these reasons, I'm willing to wait a few extra days and get a supremely professional job done with an industry quality soldermask and silkscreen, even when I only need a handful of protos. I'm certainly willing to pay their asking price for the 10 excellent "proto special" boards I am guaranteed to receive from Imagineering in a few days, as opposed to spend all day of my time and produce a marginal one or if I'm having an off-day, maybe one for the scrap pile and I get to do it all again the following weekend. Woops, there goes a Saturday :-(

-Brian

I offer the following to balance the viewpoints. Certainly there are skills to be learned and a critical mass of required equipment and supplies is required. They are rather small, however, and readily attainable to almost everyone.

Carbide drill bits are specialty items. One inexpensive source is

Resharpened bits cost less than $1 each. OTOH, you need to buy a few at a time. Expect to spend $20 or so on drill bits. 24, 32, 40, 62, 125 mils are the sizes to get.

Dremels and Rotozips have 1/8" collets that take these drill bits. Some folks mount them on drawer slides to guide them. I mounted a rotozip on a small linear guide I snagged for cheap on eBay. CNC is better, of course. A small drillpress can also work reasonably well. Drilling freehand with carbide will only frustrate you and break the bits.

Toner transfer can be made to work. I get good results using Pulsar products:

I hear of good results from glossy paper, and inkjet paper. I haven't tried those. Toner transfer can make sense if you have ready access to a laserjet.

Photo-resist can deliver superior results. Pre-sensitized boards cost about twice that of plain pre-clad. Laminant is not particularly expensive square foot-wise, but it's difficult to find in small quantities. Exposure boxes can be made from plain flourescent tubes and 1x lumber. You can also strip the guts out of an old scanner and put in real UV tubes. Or just go the old-fashioned way and mount a tube on a 2x4 frame. Developer and stripper are common, cheap, and readily available as swimming pool chemicals.

I prefer toner transfer for my one-off work.

Start to finish for me is about an hour, from printing the artwork and drilling the holes, to cleaning the sink and turning on the soldering iron. There is value beyond simply dollars in the fast turnaround and the continuity of thought preserved.

I'll leave it with one final thought. Holes are expensive, and unavoidable. The rotary tool and its bondage, plus the bits, are the major capital investments. Unplated holes and vias are without doubt a major PITA. A clever person can build a small plating tank and power supply (5A DC into 20 milliohm) for not much more than $20. Anode bars and electrolyte adds another $80. Conductive ink, if you can find it in very small quantities, will cost another $50+.

Making your own is not for everyone. The obstacles are many, but small and easily surmountable. They can be taken in baby steps, or all at once. I doubt anyone really enjoys the mild tedium of making a PCB, but oftentimes it makes sense compared to the alternatives, especially for comp.robotics.misc.

[For the OP, the quickest way to "stuff" vias is to run a single unbroken length of tinned 30 AWG buss wire through all the holes, and then solder both sides. Clip off the stuff between the holes. You might get away with these plugs under SO packages if you're good and careful, but SS and smaller won't tolerate even the slightest bump underneath. You also have to keep in mind soldering access when laying out your boards. The inside row on RJ45 jacks, for example, is accessible only from the bottom. All pads that connect to signal traces need to be soldered. I take the time to solder all pads on both sides for mechanical strength. For my needs, plating the holes is the solution, not farming out the boards.]

"Mike Young"

Someone else had suggested zipping one single wire through all holes, simple and clever idea. I managed to do my first board, had a couple of problems with distance from traces and surrounding ground plane... I'm having no problems drilling holes 0.038" with a bench drill, but you're right, drilling one or two is different from drilling 40. Patience is a virtue. I'm doing double side, the alignment came out perfect. The technique I'm employing is to draw crosses inside big holes on the extremities of the board, then drill it before exposing and then sticking the two transparancies aligning the crosses through the holes.

I'll post more of my results later.

Cheers

Padu

Thats how I do them.

I think you can get little rivet type things for a "professional" job but if nobody else is gonna see it, why go to the expense. A small hole from pad to pad and a piece of component lead soldered in should be fine. The tricky bit is lining the pads up when making the board.

Good luck ;)

Rob

People did that back in the 1980s, but now that you can get boards made cheaply with plated through holes, nobody bothers.

John Nagle

Well I would suggest to make a PCB of your own in a better way, just like the professional ones. Get a copper cladded board(available easily), copy your circuit design in a transparency sheet(used for O.H.Ps), and transfer your design to the board. Etch the board using copper sulphate.

Good Luck

Regards, Abhinav

From what I remember of chemistry, ferric chloride works better.