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Forum: PCB Design & Technology miniscule Soldering contact pad has dissolved from the PCB. How do I solder now?


Author: viskjall (Guest)
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Hello,

first of all, thank you all very much for the great work you're doing 
here. I have a question, hope you can help me out:

Ipod touch 4, Power ON/OFF, Volume Flex cable soldering onto logic 
board.

Problem: 1 of the 4 contact pads have dissolved while soldering, can not 
turn the volume UP

please refer to the picture

Question: how to fix this? There is a hair-thin line on the connector, 
should I scratch off the PCB coating and try to establish a connection? 
how do I fix solder on it?? Maybe sticking a piece of copper or other 
metal on it (if so, what kind of glue can I use, the section is SO 
small, im thinking about the sticky two sided 3M adhesive I have from 
various iPhone repairs). Will I be able to solder onto the connection (I 
guess it's about 0.1mm thick lol)?

thanks a lot, i'm in deep **** here, owner wants it back, friend of a 
friend :((

: Moved by Admin
Author: Matthias S. (Company: matzetronics) (mschoeldgen)
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You could try to remove the coating by using a glass-brush with a small 
tip, or try one of those blade-knives as a desperate measure, where the 
glass-brush is the preferred method. After having removed the coating, 
prepare a copper wire, preferably enamel-insulated ( used in e.g. RF 
coils). Apply solder to the board's trace and carefully solder the wire 
to it.

Author: viskjall (Guest)
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Unfortunately, my efforts so far have been in vain:

My problem: Trace is so thin I have trouble soldering anything onto it.

What I tried instead: Soldering a wire from the nearest test point that 
tested positive for Pin 2 (the missing contact pad).

did not work. :P Maybe I didnt solder it right or my flex is damaged or 
the wire is too thick (copper wire pulled from in-ear headphones, there 
was a good connection from the two soldering points)? . Dont know if 
this has anything to do with it but that testpoint also tested for pin 3 
(presumably ground, pin 3 covers the whole flex and on the PCB it has no 
visible trace)

Solution needed:

1. Will try to solder a wire directly to the hair thin trace again. any 
pointers are much appreciated. I have 1mm solder wire (vs 0.1 mm trace, 
unscratched only a small area, the location is difficult) and I'm using 
a flux liquid called "Flussmittel GSP-2533RX". Do I need to buy a 
smaller solderwire?

1a) will try the old fashioned way. Problem heating up the trace and 
apply solder on it. The solder just sticks to my soldering tip.

1b) could try using a small thin copper tape, solder some solder on it 
and try to "stick" it on hoping that the trace will connect. what do you 
think?

2. How about conductive varnish? 
http://www.conrad.de/ce/de/product/241319/SILBERLE...

Will this work? I could stick a copper sheet on there OR just try to 
solder onto the varnish?  but will the varnish stick on the PCB? And can 
I use a toothpick or sth similar PRECISE to apply it?

3. any other suggestions?

thanks a lot for your help, I'm really desperate I DO NEED THIS TO WORK 
:((((((((


see pictures

Author: Matthias S. (Company: matzetronics) (mschoeldgen)
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if you follow the trace on the 3rd picture, it leads to a small circular 
pad, where you could try to brush the green coating away (i hope you 
have that glass brush handy). Remove the coating until you see the 
copper nice and clear and put a tiny drop of your 'Flussmittel' to it. 
Now use a small wire of the 0.15mm type (enamel insulated) from e.g. a 
transformer or a coil. Apply heat first to the wire, removing the enamel 
and apply solder to it, basically as if you would use it in wire-wrap 
techniques.
Apply a little solder to the pad on the board and solder the wire to it 
using tweezers to precisely position it. Use adhesive tape to fix the 
wire there while making the connection on the other side of the wire.
Conductive silver is nice but won't help here, as it will not stand in 
place.
Its very useful to repair rubber-type push buttons and similar, though.

Good luck!

Author: viskjall (Guest)
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ok, apparently the new flex was faulty!! Thanks for your help Matthias!!

i got a new flex and jumped it to the small circular pad and IT'S 
WORKING. BUT due to the small space i fear it wont survive a few drops 
to the ground.

ive been thinking to apply a little hot glue, only on the soldered patch 
around the circle to avoid adding too much weight, what do you think?

ideally i can press the emi shield onto it before it gets cold..  but 
still it's not a very good solution...

Author: Matthias S. (Company: matzetronics) (mschoeldgen)
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viskjall wrote:

> ive been thinking to apply a little hot glue, only on the soldered patch
> around the circle to avoid adding too much weight, what do you think?
Yeah, sure anything which reduces load on the wire is well worth it. I 
suggested adhesive tape, but hot glue probably is even better.

Author: shaun (Guest)
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what a glass-brush

Author: Thomas Peccia (tomp67)
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Hey guys new to the forum  I have a similar problem to visktall's but 
instead of the volume up tab my power tab broke off. I would try the 
wire jump trick but not sure where the circuit pad for the power is. Can 
anyone help and point it out? It would be greatly appreciated  I could 
try to solder to the trace but if someone knows where the circuit pad is 
located that might be eaiser.  Thanks very much

Author: Muratus (Guest)
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Thomas did you ever figure out where to connect to for the missing power 
contact point? I was just replacing my power/volume wire and my power 
contact came right off when desoldering the wire.

Author: Joe (Guest)
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No idea if you guys would even get a notification of this.

Normally, I would not feel inclined to reply, I would simply take the 
info and go about my merry way.

However, this thread saved my day.

Today I was attempting to swap out an xbox 360 optical drive for a 
client. Relatively simply procedure. In the process, you must swap out 
controller boards. There are four control wires soldered on this board. 
Super simple to remove, basic soldering. I assume my soldering iron was 
too hot, because in the process one of the contact pads broke off. 
F***!!!!!! In desperate frantic I've been googling how to fix this. Not 
entirely sure that it was actually even called a contact pad. Without 
this specific wire, the optical tray would simply open and close in an 
endless loop... lol.

I found this thread. Figuring, if it doesn't work for me, I couldn't 
stand to lose anymore than I have already, I tried. Somewhat 
differently... I took a micro flat head screw driver, I followed the 
trace and scrapped away the PCB until the copper contact was complete 
exposed. Applied an EXTREMELY light layer of solder to the exposed 
trace, soldered wire flush with the trace.

BAM!!! IT WORKS!!!!

Not exactly what you guys were discussing, but enough to get me 
thinking.

As relatively unrelated my issue was... thanks for having this thread?

:D

Author: eWeeb (Guest)
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Hi

Well, soldering can be easy if you know the basics before soldering.Here 
is a guide for component placement: 
http://aa-pcbassembly.com/design-insights/guidelin...

Cheers!

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