View Full Version : double site pcb question

02-12-2010, 05:26 PM

I have a question :D

If you have a double layer pcb and the top of the layer need to be connected to the bottom of the board, and it is on a eg leg of a chip, How do you do that ??

Note, this on a home made pcb ;-)

C - L

02-12-2010, 06:24 PM
Don't know about others, but my answer is... you don't.

As in.. don't design the board so that the top and bottom legs of an IC have traces going to them.

Instead design the board so that the "via's" (joins between layers) are in an accessible location, and then use a small wire (old leg cut off from other parts) to join the top to the bottom.

Hope that made sense.

(Full disclosure - I've only ever done single sided boards, with jumpers on the top side for those limited connections that were required)

02-12-2010, 07:45 PM
You can also use component pads as vias; you just need to solder both sides of the board to the lead.

Wayne J
02-12-2010, 08:11 PM
I use both methods mentioned above.....

02-13-2010, 12:32 AM
Using your component legs is quite normal. ICs can be a problem. Use machined sockets and a very fine point soldering iron and you should be OK. Don't over drill the holes. All my leaded IC foot prints are elongated so this makes it easier.

In the past I have also used a couple of small wires (from stranded Cat5) and soldered them on the top layer before fitting the IC sockets.

Many many many moons ago we used to use little brass eyelets. Hated using them.

02-13-2010, 05:38 PM

Thanks for you responsing, I have designet a 16 DC CH Renard controller, and now I want to test it, but if I get a company to make it, then is cost much $$ :rolleyes:

Therefore I wnat to make is self :D

I think I need this machine :p


Wayne Do you have a pic of the board ??

Wayne J
02-13-2010, 06:51 PM

Wayne Do you have a pic of the board ??

This is it assembled.

02-13-2010, 09:20 PM
This is it assembled.

the funky blue fibreglass is nice.

Wayne J
02-13-2010, 11:33 PM
the funky blue fibreglass is nice.

Yep, pretty, but does not like heat very much, makes for some very careful soldering.

02-14-2010, 12:19 AM
Unsocketed DIPs are usually pretty easy. Sockets are much more difficult.

If you are designing in Eagle, there are two layers, (tKeepout and bKeepout I think? or was it t/bRestrict?) that allow you to set regions on each side of the board where the autorouter won't route. Put tKeepout in any area where you can't solder to the top of the board in addition to the bottom, and bKeepout over any pads where you can't solder to the bottom but can solder the top.

02-14-2010, 01:28 AM
Like another poster said, machined pin IC sockets are your friend when it comes to DIY double sided boards. Now, things like relays and RJ connectors are a different matter!