10 Sep
2011
10 Sep
'11
6:47 a.m.
Hi
Fisrt thing is to get the pin relaxed in the hold.
Most ICs were install with an automatic machine.
This leaves them such that they are pushed against
the sides.
With solder still in the hole, and melted, push
the pin with the iron towards the IC. The idea
is to bend it just enough that it floats in the hole
without touching the sides.
It is hard to tell one what this feels like, but
one can tell when the bend is right that the
pin will move either way when given a gentle
push( not enough to bend it ).
Once this is done, with renewed flux, suck
the solder out.
When done there may be the tiniest amount
of solder at the base of the lead, on the IC
side, contacting the top of the hole and
the lead.
If this is tiny, take a short nosed, needle nose
pliers and push the lead near the hole inwards
toward the IC.
Check each lead to ensure that it is loose. With
a small screw driver, flip each end of the lead.
It should feel loose in the hole.
Once done to all the leads, the IC should come
out.
Dwight
Subject: RE: Desoldering (Again)
Date: Sat, 10 Sep 2011 13:08:06 +0100
From: mjd.bishop at emeritus-solutions.com
To: cctalk at classiccmp.org
Rob
I'm not surprised you are struggling : a non trivial evolution
I'll presume that we are talking DIP, and that you can't cut the legs
off - as removal without damage to either PEC or device is required. If
the chip is "toast" then cut the legs close to the package (e.g.
Lindstrom 7191) and remove each leg / clean up each via individually
using the same methods but with better access and 14 easy rather than 1
difficult problem.
Things which may work include:
- solder (sucker) pump
- resoldering almost dry joints, to get them dry on the next attempt
- lots of flux : flux pen, liquid, gel, jelly (highly recommended)
- solderwick rather than a solder pump
Things which will work:
- Pace SX-90 Sodr-X-tractor or similar hi-end tooling
(my experience is that inexpensive and poorly maintained extractors are
useless) The technique is to oversolder the joint, suck it dry while
wiggling the pin with the tool to preclude adhesion to the via's barrel
- a visit to your local wireman (who has the tooling)
I'm in Dorset UK; contact me off list if my SX-90 can help
Regards
Martin
-----Original Message-----
From: cctalk-bounces at classiccmp.org
[mailto:cctalk-bounces at classiccmp.org] On Behalf Of Rob Jarratt
Sent: 10 September 2011 10:07
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Desoldering (Again)
(resending from a different account, apologies if this is a duplicate)
I have a 16-pin IC to desolder and I am struggling.
Since I last asked about desoldering I have got a lot better with a
de-soldering pump and can now clear the hole in the sense that I see a
black
hole rather than solder, and I can see daylight through all the holes
(but
for most of the holes this is only if I angle the board the right way).
However, in this case the solder seems to be going all the way through
and
slightly onto the component side surface where I can't get at it with
the
pump. I have jiggled the pins to try to break any last bits of solder,
but
the chip is still very solidly attached.
Any advice?
Thanks
Rob