DIL package disappearing? (was: CA3046 replacement)

[Rob]

-----Original Message-----
From: Roman Sowa <Roman.Sowa at WizjaTV.pl>
To: synth-diy at mailhost.bpa.nl <synth-diy at mailhost.bpa.nl>
Date: Wednesday, July 07, 1999 9:12 AM
Subject: ODP: DIL package disappearing? (was: CA3046 replacement)


>Desoldering caps or resistors:
>with two soldering irons when precision needed, or heat one side of
>component and quickly jump to its other side. If required jump few
>times more. Works for me.

I usually use solder wick first.. That way then, there is less solder to
heat on each side, but it depends on the size of the unit.. 1206 and smaller
(about 2mm x 6mm in size) I just take a big blob of solder and wipe it off
the board! ;)

>
>Desoldering ICs (up to 20-pin SOICs):
>it takes about 4 seconds per side using 80 Watt transformer soldering gun.
>No special tip needed. Start from one adge, give it a nice heat and slowly
>move through all pins. May need to do it few times. All the time pull the
>IC.
>Then go to the second side of IC. Little messy technique, but works for me.

Here again, I use solder wick to get rid of some of the solder on the legs,
then I use an exacto blade to slide under the pins and lift them gently one
by one, being careful not to lift the pads.. you lift the pad, and you are
in a world of trouble..

>
>More elegant IC desoldering:
>Get 0.3mm transformer wire, and put it under IC pins at one side. Secure
>one end of the wire (solder somewhere). Heat first IC pin and pull the
wire,
>so it will go between pcb pad and the pin. Pin is then rised a little, and
>solder wiped out. Repeat that with every pin, and then do it for the other
>side.
>This technique is also usefull for PQFP packages.

These are all good, I think the only other thing I might add is to make sure
that the solder is completely liquid before you try to lift, pull, push,
etc..
Once again, it is paramount that one does not lift the pads...

If it is really bad you could always cut the legs of the IC and remove them
one by one..
I do this if I dont really need to evaluate or reuse the part Im removing..

Oh, another thing: flux the solderwick before using it anywhere.. This will
help flow the solder off the pads..
The pads must be cleaned thoroughly of solder before another part is placed
there..
Otherwise the part will not sit level, and it will be exceptionally hard to
keep in place while soldering..

Another tip is if the part is too difficult to place, but a bit of flux on
the end of a dental pick, needle or piece of wire, and stick the part to the
end of it and hold it in place while you solder.. I find this easier than
using tweezers..

Sometimes its easier to use a bit of glue to glue the parts in place first
before soldering.. But it needs to be some type of glue that breaks down
during the heating process, otherwise youll never get the part off.. They
have syringes of this type of glue in digikey and farnell.. I never use it,
but some ppl swear by it..

Then, there is even some sort of syringe full of solder paste, and you glue
the parts in place with it at the pads, let it dry, then heat the joints
with a solder iron or heat gun and the paste burns away leaving only the
solder on the joints.. This too sounds really good and less frustrating than
having parts sticking to your solder iron...

I think both the paste methods are fairly expensive, but clean, easy and
they usually look nice..

Rob