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Topic: using pin holes as vias (Read 2327 times) previous topic - next topic

Udo Klein

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

Check out my experiments http://blog.blinkenlight.net

jluciani

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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Udo Klein

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
Check out my experiments http://blog.blinkenlight.net

Jeff K

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.
Jeff K - JKDevices.com - home of the MegaMini

kg4wsv

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

Udo Klein

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
Check out my experiments http://blog.blinkenlight.net

kg4wsv

#6
Jun 13, 2010, 07:55 pm Last Edit: Jun 13, 2010, 07:55 pm by kg4wsv Reason: 1
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

madworm

#7
Jun 13, 2010, 09:20 pm Last Edit: Jun 13, 2010, 09:21 pm by madworm Reason: 1
Usually all holes are plated if not noted otherwise.
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Grumpy_Mike

Quote
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.

westfw

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.

Odisej

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?


Udo Klein

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
Check out my experiments http://blog.blinkenlight.net

Grumpy_Mike

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-%C3%B8-0-8mm-qty-100/dp/1783593

Udo Klein

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
Check out my experiments http://blog.blinkenlight.net

madworm

#14
Jun 15, 2010, 09:50 pm Last Edit: Jun 15, 2010, 09:51 pm by madworm Reason: 1
@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.
• Upload doesn't work? Do a loop-back test.
• There's absolutely NO excuse for not having an ISP!
• Your AVR needs a brain surgery? Use the online FUSE calculator.
My projects: RGB LED matrix, RGB LED ring, various ATtiny gadgets...
• Microsoft is not the answer. It is the question, and the answer is NO!

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