[sdiy] SMT?

[Rob]

Problem with this is, sometimes the still attached leads, as they are being
cut, act as little levers and tear away the pads.

Here is how I have been able to get 10x+ reworks on the same pads with smt.

Mind you, I have also been able to do this with the lead cutting method..
Only thing with myself, is that the lead cutting seems a bit destructive and
its easy to slip with the knife and lay waste to the board.. If you have a
dremel tool with the ceramic cutting wheel, the lead cutting method seems to
work a bit better by using very easy pressure, but it throws metal bits
everywhere.. They have very very fine snippers that can actually cut the 1mm
and below leads one by one.. Those work best imo.

Heres another method, less violent, and when you don't have the
microsnippers.

1) flux the leads liberally
2) put a dab of solder on the iron
3) heat the pins and melt the solder (dont worry about the solder getting
all around on the leads, youll clean it with braid later)
4) the pins that are heated, quickly use a needle or dental pick to gently
pull them up one at a time, away from the pads. Lever them up high enough so
there are no chances of them resoldering to toe board. MAKE SURE THE SOLDER
IS WETTED WELL>
5) continue all around the chip
6) once the chip is off, use solder braid to clean the pads.. Keep the
solder braid wetted well with solder, do not pull the solder braid across
the pads because it will snag and rip up the pads, and work quickly once the
solder braid is heated.


CyborgZero Technologies
www.angelfire.com/il/cyborgzerotech
AIM:cyborgzr0 <--- that last thing is a number
repairs/mods/retrofits

----- Original Message -----
From: "Terry Michaels" <104065.2340 at compuserve.com>
To: <CHoaglin at aol.com>; "synth" <synth-diy at node12b53.a2000.nl>
Sent: Sunday, April 08, 2001 9:19 AM
Subject: Re: [sdiy] SMT?


> Message text written by INTERNET:CHoaglin at aol.com
> >coincidentally, that's exactly what I'd like to figure out how to
> rework..I've got an industrial PC with an IDE controller chip that's 100
> pin
> SQFP, and I'd love to know how to get it off the board and put another one
> on
> (without a SMT rework station...) The idea of a heat gun crossed my mind,
> but
> I'm not sure it's hot enough.
>
> Anybody got ideas?
>
> Chris
> <
>
> Hi Chris:
>
> If you don't need to re-use the chip you are removing, the quickest way to
> remove it is as follows.  Take a razor blade or exacto knife and cut all
of
> the pins off the chip, right at the body.  Next, pluck the chip out,
> leaving the pins behind.  Now it is a simple matter to put a blob of
solder
> down with your iron on the first few pins, and loosen and remove them.
You
> can then go all the way around mopping up a few pins at a time, solder
wick
> is helpful.
>
> Terry Michaels