Surface mount chip problem

I should add that I've got the right equipment for SMT reworking and have successfully removed and replaced quite a number of SMT chips, but this is a rather new problem.

Tiniest of blobs of conductive epoxy on the cut end of some 40 gauge or less copper wire , then other end soldered to the trace, while heatsinking the middle? How to get a tiny blob ? warm up the epoxy slightly and heat up the wire prior to epoxying ? don't know have not tried it at any time

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Thanks, I really like that idea. Only problem is that conductive epoxy is very expensive (due to the silver content) so is there a cheaper and equally effective alternative?

Think I would try to blob a small amount of solder onto the tiny lead remains, and then solder a piece of #32 wire (pretinned on both ends) to the blob and the trace, with a heat-sink of course. Would try to use a light-duty soldering iron with just enough heat to melt the solder. The Weller Cold-Heat Pro cordless soldering iron would come in handy here... (my experience. YMMV)

Good luck.

Dave

Have any friends who are *good* dentists? If so see if one of them can use their fine tools to eat away a bit fo the plastic. They will need to understand what they are doing, and how much you want to remove but I'm sure it can be done.

Are you able to check what the damaged pin does ? If you are incredibly lucky, it might just be common with another pin or just have an internal resistor or diode to another pin. Sod's Law says that you won't be that lucky, but you never know - the gods of electronic accidents might just be smiling in your direction today. They certainly weren't looking my way when I had a flash-bang encounter with a Pioneer amp that I had just finished working on ... :-(

Arfa

I would suspect that most folks working with SMT have experienced this problem. My solution was to use a tiny sewing needle pressed against the remaining pin metal on the device and secured (under pressure) with non-conductive epoxy. You can even see a magnified example of this approach in photos of my mods to the Zipit Wireless Messenger (takes a little site drilling to get to the appropriate photo, but it is there) at:

Michael

snipped-for-privacy@hotmail.com (jamma-plusser) wrote in news: snipped-for-privacy@news.zen.co.uk:

You could spot weld a small wire to the end. IC makers spot weld gold wires to the IC's all the time.

Of course the equipment to do that might be a bit more expensive than conductive epoxy :)

You could try some silver bearing conductive ink from radioshack.

less

Has anyone ever tried grinding gold of 70s TTL board edge connectors and mixing the sieved dust with standard epoxy? I know graphite does not work. Mercury and epoxy? would mercury amalgam stick to things ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Thanks all. I'm afraid that the leg in question carries a needed signal so no chance of doing anything but repairing it.

I'm going to attack the chip with a dremel tomorrow and see if I can very carefully expose enough of the leg stub to solder to. If I fail then nothing lost as the chip is no good as it is anyhow.

"N_Cook" wrote in news:gg22od$2f3$ snipped-for-privacy@news.motzarella.org:

You do NOT want mercury anywhere near electronic equipment.

Back in the late 70's I saw a mini-computer that had mercury (a manometer was laid down on top of it) all over the circuit boards.

We had to scrap it.

Attempting to replace a part would have been fatal. Mercury vapor is highly toxic and would have been released in large quantities by any heating such as soldering.

Mercury is bad enough at room temperature! If you work in a room where mercury has been spilled and not properly cleaned up, you can accumulate enought mercury in your body from breathing the mercury vapor to make you very sick or dead.

Not to mention the fact that many parts get rather warm during normal operation.

Attempting to use that computer would have been deadly.

snipped-for-privacy@hotmail.com (jamma-plusser) wrote in news:49248d7c.559184421 @news.zen.co.uk:

I DID fix a surface mount chip that I broke a leg off of by using the conductive paint I mentioned earlier. After it cures it can be soldered to.

I replaced the chip later even though it was still working, not trusting it to be reliable.

Good luck to you.

jaycar has some silver conductive paint in very small bottle

jaycar has some silver conductive paint in very small bottle oops jaycar is australian maybee radio shack might have same thing

See new thread title TIP: Poor man's conductive epoxy

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

General Cement makes both 'Copper Print" & 'Silver Print' for the US market.