On Mon, Sep 04, 2006 at 07:15:42PM +0100, Peter TB Brett wrote:
> On Friday 01 September 2006 17:55, Dieter wrote:
>
> > For the most part I agree. De-soldering a DIP from a board without
> > destroying it is the exception. The legs love to stick to the walls of the
> > hole, even with the use of solder-suckers and solder-wick.
I've replaced quite a few in my time. The way I usually do it is to
heat the pin from the top side with a fairly massive temperature-controlled
tip set to 600 degrees F (fairly cool), and suck from the bottom. If the
pin is stuck to the side of the hole, I heat the pin again and free it with
tweezers.
The best method is a hot-bar desoldering tool, which heats all the
pins at the same time. I've never had one, though.
However, if I expect to replace it (exposed to ESD or overcurrent),
I mount it in a DIP socket.
> > And even
> > high-quality boards with experienced rework people are only good for about
> > 5 replacements. With a low quality board you're lucky to replace a chip
> > once without destroying the lands. So I never solder DIPs to a board, I
> > always use sockets.
>
> True: trying to replace a DIP by the 'traditional' technique (desoldering
> each
> pin with a sucker and then pulling the chip off) almost always destroys the
> PCB.
>
> However, replacing a DIP is actually quite easy, if you don't want to reuse
> the original DIP.
>
> 1) Clamp the board (in a vice, usually) so the package body is downwards and
> the pins upwards
>
> 2) Get a *high power* soldering iron and flood all the pins of the package
> with a giant blob of solder. Stroke the iron backwards and forwards, keeping
> all the pins nice and hot.
>
> 3) The DIP will fall out under its own weight, lubricated by the molten
> solder. Throw it out, it'll almost certainly be wrecked.
Depends on the iron temperature. 700 or more is likely to ruin the
part. However, if you don't mind destroying the part, production solderers
I've met prefer to clip the pins off the IC, then de-solder them one at a
time, heating from the bottom side and pulling the lead from the top with
tweezers.
> 4) Get some braid and a flux pen and carefully clean the footprint.
>
> However, this is impossible (or at least very tricky) to do for packages with
> more than 16 pins, unless you're quite experienced at this technique.
>
> If someone who *doesn't* have a lot of rework experience is going to be
> expected to need to replace the chip, fit a DIP socket. ;)
>
> Peter
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