Oxidised components

[David]

I've been having problems with an SMD board that I've been making some
modifications to. I suspect that I've damaged the component (I'm no expert
on SMD and can only say that the part is either a resistor or capacitor) in
that I can't see any metal on one end and it's extremely difficult to get
any solder to stick to it. Would excessive heat and/or flux oxidise the
metal in such a short space of time? If so, how can I fix it?

 

[Chris]

I've been having problems with an SMD board that I've been making some
modifications to. I suspect that I've damaged the component (I'm no expert
on SMD and can only say that the part is either a resistor or capacitor) in
that I can't see any metal on one end and it's extremely difficult to get
any solder to stick to it. Would excessive heat and/or flux oxidise the
metal in such a short space of time? If so, how can I fix it?

Hi, David. Sorry to be the bearer of bad news, but the solder has
actually leached away the termination on the one side where you can't
see any metal. There's no way to make a connection, even if you
haven't killed the part with the iron by overheating. It will never
make contact.

You'll have to buy a new part, I'm afraid.

While you're at the store, try to pick up some eutectic silver-bearing
solder (Sn/Pb/Ag 62/36/2%, .020" dia.) with a good flux. This mixture
assures minimum melting temperature, and the silver will help to reduce
the leaching effect. The self-cleaning fluxes are too mild, and don't
do a good job of wetting.

Also, get a temperature-controlled soldering iron, with a suitable tip.
Keep the tip at 750 or so, to avoid overheating of the part.

Solder-Wick or other copper despldering braid is also a good thing to
have while reworking. Try to get the narrowest possible braid (.062"
is good).

Do these things, and with good soldering technique, you won't have to
worry about this again.

Good luck
Chris

 

[David]

Hi, David. Sorry to be the bearer of bad news, but the solder has
actually leached away the termination on the one side where you can't
see any metal. There's no way to make a connection, even if you
haven't killed the part with the iron by overheating. It will never
make contact.

You'll have to buy a new part, I'm afraid.

Dammit dammit dammit. That's my PS2 up in smoke

Actually the mod is working to some extent. When it decides to boot it works
for up to 30 seconds before freezing. It works sometimes when I disconnect
the power and then reconnect. It also works sometimes if I tap the unit.
This suggests that all the connections work, but that one or more are a bit
flaky. I suspect this part I've been having problems with.

Also, get a temperature-controlled soldering iron, with a suitable tip.
Keep the tip at 750 or so, to avoid overheating of the part.

I've been using a temperature controlled iron. Always a bit wary of
overheating components so kept it at no more than 300 C (572 F). The solder
I have melts immediately at this temp but I have had it as low as 280, which
means the solder doesn't melt properly unless the iron's been touching it
for a couple of seconds.

Solder-Wick or other copper despldering braid is also a good thing to
have while reworking. Try to get the narrowest possible braid (.062"
is good).

Do these things, and with good soldering technique, you won't have to
worry about this again.

Thanks for the tips.