using pin holes as vias

After etching my first double sided PCB and soldering all the vias I figure that this is quite a lot of work. So I will probably give the next to some PCB house. However I wonder if I can use pin holes as vias. The point is: if the pin is covered by the rest of the device in such a way that I can not solder from the top, will I still get a reliable connecting between bottom and top layer? Or do I need to draw an additional via to connect bottom and top layers? Or is there any specific trick to get pin holes plated like vias?

Any hints would be highly appreciated.

Udo

What kind of devices? If the device is socketed you could get a long pin socket
like a wirewrap socket. This would give you some space on the top to solder.
Not pretty but should work fine for prototypes.

(* jcl *)

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Especially the LCD display. Of course I can put it into a socket like you propose. But then then the LCD will be much higher then the rest. Looks ugly. I have enough space left so vias are not a space issue. The question is if I should put them in or if this is a waste of time. If the pin holes would be treated like vias there would be no point in introducing vias redundantly.

And for possible future projects where space might be an issue I also wonder if pin holes will be plated.

Udo

Depending on the size of the hole and use of solder paste the solder can wick through the hole plating the other side. As far as reliability goes… you would just have to do some trial and error. Maybe try plating the pins and holes with solder on the “unsolderable” side first… then some solder paste on the holes, then insert the component and heat up the lead from the other side adding very thin solder and it might pull it through the hole reliably.

I don’t think you can reliably expect solder to wick through an un-plated hole, and certainly not stick to an un-heated pad on the opposite side.

If the connection in question is a header (e.g. LCD connection), I have played games like solder the header upside down, such that the plastic spacer is well above the PCB and I can solder on both sides of the board. After all pins are soldered on both sides, slide the plastic spacer down to the board (if there’s room) or remove it entirely (but this can leave it a bit flimsy).

-j

This is absolutely understood. This is why I am asking. Will pin holes be plated? Or is there a means to indicate that they shall be plated?

Udo

If you’re talking about sending out to a board house, my understanding is that holes for through-hole components are plated. Your software (e.g. library components) probably specifies this for you.

-j

Usually all holes are plated if not noted otherwise.

I don’t think you can reliably expect solder to wick through an un-plated hole

I think you can reliable expect it not to.

I have used socket strips for ICs that allow you to solder both sides of the board. They come as a strip you solder them down and then bend over and snap the metal strip holding them together.

If you have your board professionally manufactured, then it is usually harder to get (any) holes NOT plated through. Component pin holes will always be plated through on a (professional) double-sided board, and all the normal CAD packages assume this.

If you made the board yourself, it’s really hard to solter on the top layer if you don’t have access (for example to solder a USB connector to the top layer, almost impossible to get it right the first time). The best way is to simply solder the top and bottom layer to the element. And use only bottom for connectors like USB.
Btw, how did you manufacture the double sided PCB?

  1. I asked for boards from the board house. So thanks to westf for answering my original question.

  2. @Odisej: I laser printed it onto some magazine paper and ironed it to the PCB. One side. Then I drilled two holes for pins as close as possible to opposite corners. Then I put some needles through the printout for the other side and used this to align the printout. Then I ironed the other side.

I did 2 PCBs that way. Then I etched both. The first got much better than the second. Anyway I managed to get everything in place.

Unfortunately it seems that I somehow managed to break one output pin (not mechanically, electrically). So I will still require some rework. It was quite a lot of work, especially the vias. But it was easier then expected.

Udo

You can use these rivets to place in a hole and in effect make it a plated through hole when you are doing your own double sided PCBs.

You can get them here:-
http://uk.farnell.com/cif/bg9-s/rivets-ø-0-8mm-qty-100/dp/1783593

Yeah, but the overall process is to cumbersome for me. Etching a board, putting in vias and populating it consumes several hours. Time I could use for programming. I think I will order to PCBs.

Udo

@Grumpy_Mike:

No he can’t. Assuming he’s a hobbyist.

Farnell doesn’t sell to non-business people in the beloved country of Germany. Seems like they make enough money elsewhere. They kindly refer you to an off-site web-shop for the unworthy. If you compare the prices, you pay 30% or more there - prices corrected for VAT.

I’m glad that mouser and digikey aren’t that stuck-up.

Farnell in the UK is a little more forgiving, although I did have to provide extra details when setting up an account with RS (who are often cheaper than Farnell).

One of the benefits of having owned a company to contract through :slight_smile:

Well, I don’t mind being referred to a different web shop. But it’s the ‘adjusted’ prices I dislike, and not just for single quantity but also for several 100s of chips. Why should I have to feed another dog just to get the very same parts. A bunch of jackasses. Now if I should ever have to deal with them on a business level, they’ll be at the top of my blacklist - which is growing steadily.

Well, I could buy them from other suppliers and I know some guys running their own business. This would not be the issue. Time is the issue.

I found this today: http://www.haka-lp.de/html/zwillingsangebot.html

That is for 2 boards of 80x100mm I will pay EUR 39.88 . For this price I will not etch anymore. Doing this once was enough. If I find a cheap source for getting them populated I will not solder anymore as well.

Any hints for cheap services for doing so in Europe?

Udo

No he can’t. Assuming he’s a hobbyist.

Well that is a very different experience to what I have had. Back in 1975 RS would not even entertain me and returned a cheque even though I was trying to set up a business. They said I did not have adequately staffed full time permanent premisses. They were very nasty about it. On the other hand Farnell gave me a business account and a credit facility with just a bank reference.

Now that I don’t do that any longer I deal with Farnell as a hobbyist on a cash (well card) with order basis. There is a minimum order of about £24.00 or so but I still get the same great service from them. They aren’t the cheapest but they are very quick and reliable.

Of course they’re quick and reliable. Otherwise they’d be out of business pretty quickly. For them it just shouldn’t matter if Mr. Private orders parts for a 100 bucks or Mr. Small Business. But maybe keeping hobbyists out of their database is a German thing. Some businesses in this country wouldn’t sell to me as a hobbyists even if I were waving enough money under their noses to acquire the whole thing. If I had that kind of money I’d fire the whole ‘upper management’ and have a little chat about customer satisfaction with the remaining staffers.

Now back to the original topic :wink: