"Arfa Daily" wrote in message
news:bHh4o.61130$0e3.22364@hurricane...


"Ian P" wrote in message
...
In the course of doing some modifications to a very expensive Sony 3 chip
HD camcorder I have accidentally cut through 3 tracks on the edge of a
mylar? flexible cable. On the good side the damage is very accessible but
the bad bit is the tracks are only 0.1mm wide on a 0.2mm pitch! Ideally
one would just replace the flex pcb but in practice that would involve
dismantling the camera and lens to get to all the places the pcb branches
out to, and in some places it actually goes into the lens mechanism
itself.

I am considering abrading off the top mylar coating to expose the copper
then bridging the breaks with some very narrow pitch zebra strip. My
other idea is to make my own miniature insulation displacement/piercing
connector using a stack of razor blade bits sandwiched with insulation
layers.

The last option would be to use wire links and solder but I think this
could only be done with some sort of mechanical micropositioning rig in
view of the small sizes involved.

I would be interested to hear any thoughts or experiences if anyone has
any.

Cheers



Ian



Based on my experience of trying to repair accidental damage to
flexiprints (yes, it happens to us all no matter how long we've been in
the game and how experienced we are !) I think that you are going to
struggle to get a fix on one of that tiny pitch. I have had plenty of
success with abrading and soldering ones of a slightly greater pitch,
doing it with a tiny needle-point soldering tip and under a microscope,
and using a single strand from superflex instrument cable, such as is used
for better quality meter leads, for instance.

I don't know whether this is a commercial job, or one for a friend, or
maybe even for yourself, but before you commit to any strategy that's
going to waste a lot of time, and end up with no fix at the end of it
anyway, the job would probably stand being left for a day or two, before
revisiting it with a clear head, to look at how hard replacing the
flexiprint would *really* be. I've often found that things that look as
though they are going to be a copper-bottomed-gold-plated bitch to do, are
actually not so bad, when looked at again after you've calmed down, and
forced a degree of 'san fairy ann' into your head over it. If you have a
copy of the service manual or can obtain one, a look at the parts list
will tell you if replacement is even an option (if you're really unlucky
it might be an integral part of the lens assembly) and if it is available,
a look at the exploded view diagram, would be helpful to determine how
many 'hidden' branches the flexiprint has, and where they go.

I really feel for you on this one. I've been there many times over the
years ...

Good luck with it, and please post back, and let us know how you get on
with it :-\

Arfa

Arfa

Thanks for your advice. As you postulated this pcb is integral with the lens
and although I have the full service manual for the camera it give no
information at all on the lens which is a bought in item (not removable
though). The job is not really commercial, for a friend or myself but it a
sort of combination of all three. I caused the damage though and I need to
repair it because there is not really any alternative.

I have in the past repaired and modified boards and components and used thin
wire just as you described, this cable though has track and spacing widths
that are really challenging, and I don't have any microscope.

I have lots of old bits of similar flexible boards and cables so I am going
to experiment with them.

Ian