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From: Ian P on 29 Jul 2010 13:19

"Meat Plow" <mhywatt(a)yahoo.com> wrote in message
news:pan.2010.07.29.14.56.20(a)hahahahahahahah.nutz...
> On Thu, 29 Jul 2010 07:47:37 -0700, William Sommerwerck wrote:
>
>> This is "not unlike" fixing a PCB trace. How would you do that?
>>
>> What about globbing some eutectic solder over the traces (even though it
>> shorts them), then using "something" to break the solder into individual
>> "strands" while it's still liquid?
>>
>> I'm wondering whether zebra strip would be conductive enough? It might
>> not matter over such a short (ar, ar) distance.
>>
>> I wish you success. And if this happened this morning, please put it
>> aside and relax. Work on something else, something easy, and try to
>> forget about this problem for the time being.
>
> Flexible pcb connector as in a ribbon connector? I've had some limited
> success repairing these with conductive paint designed to repair
> automotive window heaters.

Its a paper thin flexible pcb, golden brown in colour which I think is made
from Mylar. Because of the narrowness of the tracks and their spacing I
doubt it could be done with paint.

Ian


From: Ian P on 29 Jul 2010 13:24

"N_Cook" <diverse(a)tcp.co.uk> wrote in message
news:i2s5e6$b1d$1(a)news.eternal-september.org...
> Ian P <elanman99(a)yahoo.com> wrote in message
> news:8bdgspFuetU1(a)mid.individual.net...
>> 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
>>
>>
>
>
> Assuming you're not in a stripline-type situation with ground plane/rf
> considerations, try plaiting some magnet wire and soldering to the 3 pcb
> solder points at either end of the plaited section of "ribbon", you may
> have to make a hole through the pcb though.
>

Its just low level analogue signals but the break is close to the end of the
ribbon where the tracks are gold plated to fit in the board connector. The
copper conductors are encapsulated in the Mylar and drilling through the
track which is only 0.004" wide would not be easy!

Ian


From: William Sommerwerck on 29 Jul 2010 13:33
> It happened several days ago so have got over the initial shock
> and annoyance with myself. I am not rushing in until feel right.

Good. That means you'll probably come up with the "least bad" solution.


From: William Sommerwerck on 29 Jul 2010 13:42
> 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.

I'm starting to get the feeling that maybe you should "bite the bullet" and
have Sony do the repair. It's going to cost a lot of money, but it might be
worth it, simply in the grief saved.


From: Paul Hovnanian P.E. on 29 Jul 2010 14:00
Ian P wrote:

> 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.

I've had some luck repairing individual breaks with a conductive repair pen.

Given the pitch you are working with, you might have to expose spots on each
trace that are separated by a few millimeters along the length of the
traces to prevent bridging them with the ink.

I'm not certain how well the conductive ink stands up to continued flexing.
Gluing some stiff backing behind the area of the repair might be a good
idea.

--
Paul Hovnanian paul(a)hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.
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