repairing broken traces on a PCB

[samIam]

I have broken traces on a PCB I recently etched. Just a handful ...

I am wondering how some of you repair them. Trying to tap into your body
of experience with this.

I tried soldering wirewrap from one trace to another ... but thats not
very effective ... I might try pin to pin this weekend.

ALso I have seen (on some pcbs from commercial equiptment) special
round shaped adhesive tape that placed on the strip repair wire to hold
it to the board.

Anyone know what these are called and where I can get some?

 

[Spehro Pefhany]

I tried soldering wirewrap from one trace to another ... but thats not
very effective ... I might try pin to pin this weekend.

You bare tinned wire. 1N4148 diode leads are about 0.5mm diameter and
work well down to fairly fine pitch. Lay across the break, solder on
both sides.


Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

You bare tinned wire. 1N4148 diode leads are about 0.5mm diameter and

^^^
can use

work well down to fairly fine pitch. Lay across the break, solder on
both sides.

Best regards,
Spehro Pefhany

 

[samIam]

Thats the problem ... its shifting around (the wire). I can get it fixed
but the time its soldered its sloppy and the sligthly nudge breaks it
off.

 

[Jim Thompson]

You bare tinned wire. 1N4148 diode leads are about 0.5mm diameter and
work well down to fairly fine pitch. Lay across the break, solder on
both sides.


Best regards,
Spehro Pefhany

I use "solder-sucker" braid to bridge breaks like that.

...Jim Thompson

 

[Noway2]

There are also kits available for PCB repair that contain adhesive
backed materials that get applied to the board with a special tip in a
soldering iron. I have one by Pace and they call it a thermobond kit.

 

[Tim Wescott]

Thats the problem ... its shifting around (the wire). I can get it fixed
but the time its soldered its sloppy and the sligthly nudge breaks it
off.

Make sure the traces are tinned so you don't waste time and motion on
that when your wire is down. Hold the wire down on one end and solder
the other end. Now solder the unsoldered end. If you're just spanning
a crack then heating one end of the wire will melt the other end's
solder -- if that happens then hold the wire down with something small
(I use an X-Acto knife) through the whole process.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

 

[Spehro Pefhany]

I use "solder-sucker" braid to bridge breaks like that.

...Jim Thompson

That's particularly good if the PCB itself is phenolic & cracked.



Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

Thats the problem ... its shifting around (the wire). I can get it fixed
but the time its soldered its sloppy and the sligthly nudge breaks it
off.

How wide are your traces? The solder surface tension should pull the
wire towards the center of the trace.

Bend the wire into an "L first (to give you a handle to position the
wire with fingers or needle-nosed pliers), solder one side down
securely, trim the other side so it's flat with the board, and solder
the other side down. You should end up with a smooth solder and secure
joint on either side. If you have solder resist, make sure to remove
it *thoroughly* from enough area to get a secure joint.



Best regards,
Spehro Pefhany

 

[Ken Taylor]

I have broken traces on a PCB I recently etched. Just a handful ...

I am wondering how some of you repair them. Trying to tap into your body
of experience with this.

I tried soldering wirewrap from one trace to another ... but thats not
very effective ... I might try pin to pin this weekend.

ALso I have seen (on some pcbs from commercial equiptment) special
round shaped adhesive tape that placed on the strip repair wire to hold
it to the board.

Anyone know what these are called and where I can get some?

Rather than scratching about traces trying to make them solder-able, we
always go from pad to pad with wirewrap wire, complete with insulation. Good
quality cutters, fine iron tip, steady hand, followed up by some adhesive to
keep the wire in place (following over the trace that was damaged) and then
covered with a spray-on conformal coating.

Cheers.

Ken

 

[colin]

I have broken traces on a PCB I recently etched. Just a handful ...

I am wondering how some of you repair them. Trying to tap into your body
of experience with this.

I tried soldering wirewrap from one trace to another ... but thats not
very effective ... I might try pin to pin this weekend.

ALso I have seen (on some pcbs from commercial equiptment) special
round shaped adhesive tape that placed on the strip repair wire to hold
it to the board.

Anyone know what these are called and where I can get some?

I use the finest self fluxing enameled coper wire I can find wich is 0.2mm,
if its a small gap then tin enough of the end of the wire to brifge the gap,
clean of the solder resist of the track, flux and tin, then solder the wire
acros the gap, then gently press a sharp scalpal on the bit to cut off end
tear the wire against the scalpal, DONT press down with the scalpal or your
cut even more tracks. if the tracks are too fine to handle, trace back to
the nearest via or pad, glue down with super glue if needed. as the wire is
quite fine it shldnt be a problem one end coming unsoldered while soldering
the other end.

I use this for prototyping to modify track paths etc and connecting new
tracks guaged out from the copper. you can get quite a good density and the
insulation doesnt melt if you touch it with a soldering iron unless u hold
it there for a while.

Colin =^.^=

 

[Frank Bemelman]

I have broken traces on a PCB I recently etched. Just a handful ...

I am wondering how some of you repair them. Trying to tap into your body
of experience with this.

More interesting is to hear about experiences in finding hairline
cracks in tracks.

 

[Spehro Pefhany]

More interesting is to hear about experiences in finding hairline
cracks in tracks.

I rather enjoy paying for 100% electrical inspection. Let the machines
find the problems.


Best regards,
Spehro Pefhany

 

[Frank Bemelman]

I rather enjoy paying for 100% electrical inspection. Let the machines
find the problems.

Well, I have a board here worth $100 perhaps, that certainly passed
all tests, but fails now. When I bend it, it works. I should add, that
after bending it ~15 times it stayed in failure mode. I found one
decoupling cap standing in the air, some flux rubbish (?) between a few
legs of a TQFP, but nothing that causes the failure. Ditched it
already.

I wonder what the dropout percentage is for tested boards, and if
it is worth paying for. Difficult to anwer of course, I simply have
excellent experience with untested boards, even with 7mil tracks/distance.
Seems that more goes wrong with the assembly of parts, imo
..

 

[Spehro Pefhany]

Well, I have a board here worth $100 perhaps, that certainly passed
all tests, but fails now. When I bend it, it works. I should add, that
after bending it ~15 times it stayed in failure mode. I found one
decoupling cap standing in the air, some flux rubbish (?) between a few
legs of a TQFP, but nothing that causes the failure. Ditched it
already.

Probably wise. I've found such problems, out of sheer stubborness, but
it's hardly cost-effective in itself, but necessary sometimes if you
want to make sure it isn't something more ominous than a single
failure.

I wonder what the dropout percentage is for tested boards, and if
it is worth paying for.

Around 1% for moderate quantity 2-sided boards, IME, but hair shorts
are more likely, and it's not that sensitive to design rules (10 mils
and 8 mils are about the same).

Difficult to anwer of course, I simply have
excellent experience with untested boards, even with 7mil tracks/distance.
Seems that more goes wrong with the assembly of parts, imo

We got a batch from a Taiwan manufacturer one time that was more than
20% bad. That was a long time ago.


Best regards,
Spehro Pefhany

 

[samIam]

THANKS

This is the most informative post here thus far. Thank you again.
I need to change my methods ... its the reason behind my failure
repairing this board so I can complete my testing

thanks again

 

[John Fields]

Well, I have a board here worth $100 perhaps, that certainly passed
all tests, but fails now. When I bend it, it works. I should add, that
after bending it ~15 times it stayed in failure mode. I found one
decoupling cap standing in the air, some flux rubbish (?) between a few
legs of a TQFP, but nothing that causes the failure. Ditched it
already.

I wonder what the dropout percentage is for tested boards, and if
it is worth paying for. Difficult to anwer of course, I simply have
excellent experience with untested boards, even with 7mil tracks/distance.
Seems that more goes wrong with the assembly of parts, imo

---
Yes, and I think a lot of it can be attributed to the "need" for
lead free solder that the european community has, so far,
successfully foisted on the rest of the world.

IMO, you can thank higher solder melt temperatures, brittle solder
joints, and poorly understood metallurgy for the reason you had to
throw away $100.

 

[Frank Bemelman]

---
Yes, and I think a lot of it can be attributed to the "need" for
lead free solder that the european community has, so far,
successfully foisted on the rest of the world.

IMO, you can thank higher solder melt temperatures, brittle solder
joints, and poorly understood metallurgy for the reason you had to
throw away $100.

I don't like it a bit, all that Rohs stuff. Pressing down the TQFP's
didn't bring any luck here, neither did pressing down other discrete
parts, so I figured this board suffered from a hairline crack in one
of the tracks.

Thanks, Frank.
(remove 'q' and '.invalid' when replying by email)

 

[Jim Yanik]

That's particularly good if the PCB itself is phenolic & cracked.



Best regards,
Spehro Pefhany

Wick thin superglue in the PCB crack.

 

[Spehro Pefhany]

Wick thin superglue in the PCB crack.

I was always a bit more "belt and braces" as Tony W. would say. Splint
the board on both sides with sheared-to-size strips of epoxy-glass
laminate and smother with good epoxy (not the 5-minute junk).


Best regards,
Spehro Pefhany