Hi

A lot depends on how many planes there are in that board. The weight of he copper
also maters a bit. If there is enough thermal mass, you will need a pre-heat process.
There are lots of ways to do it ranging from the kitchen oven to various “frame and
lightbulb” setups and on into ever more complex heating approaches.

If the hot tweezers / soldering iron / hot air tool does not reflow the solder quickly (10 seconds
or less) stop. Get a pre-heat setup and try again. With proper heat you should have the part
off in under 4 seconds. People don’t tend to use stopwatches when soldering. 4 seconds is quite
a while on a joint. Ten seconds is pretty much forever ….

Bob

I usually nibble away at the center of the part until it is two separate
pieces. Then unsolder each piece. Clean the pads off with wick then install
the new part.

Use a good sharp pair of flush cut side cutters.

Tom

----- Original Message -----
From: "Bob Camp" kb8tq@n1k.org
To: "Tom Van Baak" tvb@leapsecond.com; "Discussion of precise time and
frequency measurement" time-nuts@febo.com
Sent: Saturday, November 05, 2016 4:24 PM
Subject: Re: [time-nuts] I love the smell of tantalum in the morning

On Sat, Nov 05, 2016 at 12:12:18PM -0700, Tom Van Baak wrote:

Hello Tom.
I do this kind of repairs quite often and as you have already read from others,
almost every method like hot air, hot tweezers and two irons is suitable.

However, if you have not previous experience of smd reworking and, being
lucky that the component has only two leads, if you can have someone who
will help you and there is enough clearance around the components, I suggest
you use two irons of normal power (> 50W) with flat tip.

Hot air is a much better way to do this work, but it's also more risky:
the temperature and air flux should be right (too low and you will heat too
much everything before desoldering the component, too high and you do the same).
You can end up with melted plastic parts in other components around the area.
In some cases when sensitive components are very near, I build little fences
out of sheet metal to lay on board around the component, letting just the space
to pull up it with tweezers.

To solder back, clean the pads with solder wick, then with some form of
liquid cleaner to remove traces of rosin (I use alcohol, or thinner in some
stubborn cases). Hold the component in position pushing down to the board and
solder it manually at the sides. Forget to use SMD paste and hot air for
soldering. This has not any sense with parts so big and with only two pins
and it's trickier than desoldering about temperature and airflow...

There is another thing to look at. In some process, mainly time ago, the SMD
components were glued before soldering, so the component, even if solder is
already melt, need some force to be pulled up.

Best regards,
Andrea Baldoni

So much information from so many that have obviously run into the smell of
a burnt part.
I do the cut the part to pieces and unsolder each leg. Also the 2 iron
approach.
The absolute goal, do not damage the board.
I have a hot air station also and much like the comments made not impressed.
I did grab a scrap board to play with as I was learning.
Since your cap looks like it already split in half 50% of the jobs done.
As everyone focuses on the soldering part. The damaged board is equally
critical.
The stuff in tantalums is nasty. I clean the whole area with alcohol. And
at times actually carve out some of the carbon if I can measure some level
of resistance from each trace to the center point.
Your problem looks simple enough Tom.
Just remember this. I hate caps. But have received some of my best
equipment because they fail for $/pound. Kind of a love hate thing.
Regards
Paul
WB8TSL

On Sat, Nov 5, 2016 at 4:37 PM, Tom Miller tmiller11147@verizon.net wrote:

On Sat, 5 Nov 2016 20:57:11 +0100, you wrote:

I have never had a problem removing surface mount parts like that with
just a single soldering iron.  If access is good so that a large heat
capacity tip can be applied, then each solder joint can be heated up
very quickly preventing damage to the board.

Through hole parts on multilayer boards which have a high heat
capacity are a different manner.

On newer boards this is also a great way to dilute the lead free
solder lowering the melting point making removal easier without
damaging the board.

Add some leaded solder and flux to each joint, then remove most of the
solder from each joint with braid, and then a little heat will allow
each side of the part to pop off.

I still use my ancient Weller Magnestat irons but have quite a
collection of tips including my overpowered vacuum desoldering head.

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

Tom, I used the obvious but never read about using two soldering irons,

invented it myself, or co-discovered.

Also, a recent addition that makes SMT so easy, the title of the manual is,
"Instruction Manual for SE400, SE400-LED,  Long Working Distance Stereo Microscope",
about $200.

With a working distance of nine inches or so, it beats the pants off my
previous magnifier, Optivisor 10x where I have to have my face less than two
inches from the soldering area.

.. got the microscope from description from W7ZOI web site.
http://w7zoi.net/micscope.html

Ian, G4ICV, AB2GR

For through hole parts sure, but I would not recommend that on SMD parts,
the copper foil of a little pad is pretty easy to tear off and it's a royal
pain if you have to mount a device missing some of its landing pads.

On Sat, Nov 5, 2016 at 4:37 PM, Tom Miller tmiller11147@verizon.net wrote:

Yes. Unless you're grinding it away with a dremel (which I wouldn't recommend as far as chemical dust is concerned), nibbling away with sidecutters would be trying to force the 2 ends of the component apart. That may be stressing the pads they're soldered to, leading to a possible pad lifting at some stage.

Any of the methods mentioned that heat both ends at the same time - allowing the component to be wiped off the board - would have to be the best, stress-wise.

On 6/11/2016, at 3:00 PM, Scott Stobbe wrote:

Ditto.  I use hot tweezers -- metcal talon handpiece, in my case.  There
are other ways to do it if you don't have them.

On Nov 6, 2016 3:21 AM, "jimlux" jimlux@earthlink.net wrote: