Homebrew PCBs

Hi all,

I'm having a little trouble and I'm hoping someone here might be able to
help.

Several of my pcb's are double sided - it's taken some practice aligning
both sides for proper etching, but I'm getting the hang of it, but I've run
into another problem....

Let's say you have a part - an IC socket, some traces run from the top pads,
and some traces run from the bottom pads and some run from both.

Normally, the hole would be thruplated creating a connection between both
sides of the pad, but I don't have any kind of thruplating equipment.  So,
How do you all compensate for this?  Solder doesn't seem to want to flow
thru the hole and I've found myself removing sockets trying to figure out
how to make connections on the top pads to the bottom where one solders.

Now on places where the chip is installed permanently, I'm just soldering
both top and bottom pads, so no direct connection between top and bottom is
required.

Any ideas on how to solve this, without purchasing more chemicals or
equipment, would be most appreciated.

-Tony

>Let's say you have a part - an IC socket, some traces run from the top pads,
>and some traces run from the bottom pads and some run from both.
>
>Normally, the hole would be thruplated creating a connection between both
>sides of the pad, but I don't have any kind of thruplating equipment.  So,
>How do you all compensate for this?

Back when I did not had my own through plating station I simply placed
an aditional Via apart from the IC socket and solderd some small wire
into it.

HTH

Markus

----- Original Message ----- 

From: "Tony Harris" <tony@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, January 22, 2004 5:01 AM
Subject: [Homebrew_PCBs] double sided pcb's - thruhole question.


> Hi all,
>
> I'm having a little trouble and I'm hoping someone here might be able to
> help.
>
> Several of my pcb's are double sided - it's taken some practice aligning
> both sides for proper etching, but I'm getting the hang of it, but I've
run
> into another problem....
>
> Let's say you have a part - an IC socket, some traces run from the top
pads,
> and some traces run from the bottom pads and some run from both.
>
> Normally, the hole would be thruplated creating a connection between both
> sides of the pad, but I don't have any kind of thruplating equipment.  So,
> How do you all compensate for this?  Solder doesn't seem to want to flow
> thru the hole and I've found myself removing sockets trying to figure out
> how to make connections on the top pads to the bottom where one solders.
>
> Now on places where the chip is installed permanently, I'm just soldering
> both top and bottom pads, so no direct connection between top and bottom
is
> required.
>
> Any ideas on how to solve this, without purchasing more chemicals or
> equipment, would be most appreciated.

If you use turned-pin sockets, you can just about solder the pins on the top
and bottom if you raise them slightly.

You might be able to put thin wire down the holes next to the pins, and use
that for the through-board connection. Tricky, but I've heard of people
doing it.

Or, you could design your boards so that a via is used for the through-board
connection (the ICs should just have pads on the bottom layer) instead of
the pins, then connect the top and bottom pads of the vias with wire. I can
do this quite easily with the PCB software I use (Pulsonix).

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

Hi Leon,

>
> > Any ideas on how to solve this, without purchasing more chemicals or
> > equipment, would be most appreciated.
>
> If you use turned-pin sockets, you can just about solder the pins on the
top
> and bottom if you raise them slightly.

This I wish I could do, unfortunately the sockets I have a gazillion of
isn't turned-pin.  Next time I go buy sockets, I will have to keep this in
mind, its a good point.

>
> You might be able to put thin wire down the holes next to the pins, and
use
> that for the through-board connection. Tricky, but I've heard of people
> doing it.

Lol, this was one of the last things I tried last night before I had hosed
the board - I didn't have enough thin wire to do what I needed =(.  I was
using some spare wire-wrap wire I had laying around.

>
> Or, you could design your boards so that a via is used for the
through-board
> connection (the ICs should just have pads on the bottom layer) instead of
> the pins, then connect the top and bottom pads of the vias with wire. I
can
> do this quite easily with the PCB software I use (Pulsonix).

I think I may have to do this and just re-design the board to accomodate
this. At least while I'm at it, I can fix other issues in the board as well
that would cause me a problem should I ever want to send it to a production
house.

I did have one last idea that actually worked fairly well - my only problem
was I put too much on - was using my SMT re-work hot air iron with some
solder paste.  I was obviously too tired last night when I got the idea and
I ended up putting too much solder paste on shorting some of the pins in the
process of removing I destroyed the board (too much re-work on the pads
figuring out solutions caused the pads to lift).  But I do think that the
solder paste would have worked.  it did definitly connect the top pads to
the pins of the socket.  But just the same, I think I'm going to go and
re-work the board.

-Tony