On 11/5/16 12:12 PM, Tom Van Baak wrote:

Suitable hot tweezers would do this just fine, for both the removal and
the replacement.

this kind of thing
http://www.weller-toolsus.com/weller-t0051317199-wta-50-tweezers-smd-desoldering.html
https://www.amazon.com/WMRT-Desoldering-Tweezers-Soldering-Stations/dp/B000UMMUII

It's what I've used at work, with a wx2021
Here's the complete set:
http://www.weller-toolsus.com/soldering/systems/weller-wx2021-solder-stat-wxmpms-wxmtms-wdh51-wdh60-120v.html

The tips heat basically instantly. It makes it easy to remove/replace
even tiny stuff, although 0402 is just too small for me.

You need a good magnifier or stereo microscope, and some orange sticks
to hold things in place while you solder, etc.

However, I've been given to understand that there is another superior
brand (on this list.. )

Metcal /OKI might be that other brand. I'd certainly recommend them, but
the tweezers are not as fast to heat as the single tip devices.

I've had little success personally with the hot air devices. I seem to
toast the board before I melt the solder, and when it does melt it's not
limited to one component. Doubtless it's my technique at fault, but I
prefer the tweezers.

On Sat, Nov 5, 2016 at 7:20 PM, jimlux jimlux@earthlink.net wrote:

On Saturday, November 05, 2016 12:12:18 PM Tom Van Baak wrote:

few

very

buy?

Tom

Either a hot air jet as used for smt desoldering will work.
A variety of nozzle shapes and sizes are available.

or

One can use a fine tip iron to alloy the solder with a low melting point
solder alloy making it very easy to remove the component and then
cleanup the pads using fluxed copper braid or even a cotton bud. Its
essential to remove the low melting point alloy before resoldering.

CHIPQUIK SMD N1 works well with both leaded and unleaded soldered SMT
parts
Bob Pease touted RF induction heated irons. Hakko makes a nice one
(FX100) now the patent has expired.

Bruce

Either hot tweezers or a hot air rework station are the best/easiest
ways to remove dead parts.  But two fine-tip soldering irons will also
work and are a lot cheaper.  The idea is to heat both ends of the part
at once, and when the solder flows, lift or flip the part off.  Then,
use some liquid flux and narrow solder wick to suck off the excess
solder, and you should end up with nice smooth pads ready for the
replacement part.

The key thing to avoid damage is to make sure the solder is really
flowing on both pads before you try to lift the part.  Sometimes ground
pads have enough thermal mass that it takes a while to get them hot
enough.  Be patient.

Good luck!
John

On 11/05/2016 03:12 PM, Tom Van Baak wrote:

Hi John,

I've never used the hot tweezers.  I'm going to have to look into them.  Normally, for desoldering, I use a narrower nozzle with an elevated temperature - usually between 280C and 350C.  That blows the part completely off the pads just as soon as the solder flows, with little impact on adjacent components.  For soldering, since I use a 240C leaded solder paste, i use a larger nozzle with slower air flow at about 245C-260C depending on what I'm soldering.  Desoldering against a copper plane is always a problem regardless of the thermal pad's shape.  I'd think you'd need a pretty hot set of tweezers to get a big 1210 sized tantalum off the board if there's a ground plane.

Bob
 -----------------------------------------------------------------
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: John Ackermann N8UR <jra@febo.com>

To: time-nuts@febo.com
Sent: Saturday, November 5, 2016 2:35 PM
Subject: Re: [time-nuts] I love the smell of tantalum in the morning

Either hot tweezers or a hot air rework station are the best/easiest
ways to remove dead parts.  But two fine-tip soldering irons will also
work and are a lot cheaper.  The idea is to heat both ends of the part
at once, and when the solder flows, lift or flip the part off.  Then,
use some liquid flux and narrow solder wick to suck off the excess
solder, and you should end up with nice smooth pads ready for the
replacement part.

The key thing to avoid damage is to make sure the solder is really
flowing on both pads before you try to lift the part.  Sometimes ground
pads have enough thermal mass that it takes a while to get them hot
enough.  Be patient.

Good luck!
John

On 11/05/2016 03:12 PM, Tom Van Baak wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Dear Tom,

On 11/05/2016 08:12 PM, Tom Van Baak wrote:

You're clearly lucky, one failure mode is short-circuit, and they can
bring other stuff with them as they fail, and hence hated by some.

Now, for these caps, you can use a normal soldering-iron without too
much trouble, but I strongly recommend pre-heating the board with a
hot-air gun.

The trick is to pre-heat the board widely so it becomes hot, but not
enough to melt any solder. As you now apply your soldering iron, the
heat-transfer won't be as large as if you had a room-temperature board,
simply because the lower temperature gradient.
The effect is that your heating up goes quicker and that part of the
board won't experience excess heat for too long.

Another trick I use is to solder new solder onto the joints. This breaks
through the oxide layer, which is a poor heat conductor. I solder onto
the joints and let them cool. Then I come back again and now the
soldering iron melts it all up nicely.

I still do SMD with my Weller WECP-20, but it's not optimal.
At work we moved the otherwise so high valued (over-valued) Metcal to
the side as the new JBC stations is much better. Metcal's doesn't keep
the temperature good enough and the new JBCs is beeter. Metcal's also
have a failure-mode in their tips which makes them break way to early.
There exist replacement tips which is in fact better than the original.

So, if you need an excuse to buy a new toy, look at the JBC-stuff:
http://www.jbctools.com/

However, I would probably be able to replace that cap before your get
your new and shiny toy on the table.

Cheers,
Magnus

Hi Tom,

I'm a SMT rework technician for a large satcom and defense company.
I have a shop at home too and all the equipment to repair this if I can be provided with the replacement cap.
Please let me know if I can be of help.

Chris
KD4PBJ