> I've used a variety of vacuum desoldering stations in the
> past and have 2
> favorites: Weller DS-100 series and Metcal.  I have used the
> Pace, Hakko
> and early OK Industries units but don't like them anywhere
> near as much as
> I like the Weller.  The little hand-held Denon all-in-one
> units work great
> for resistors or capacitors but are a little bulky, and
> therefore hard to
> control when trying to ensure that every lead of a large DIP is free.
>

I did one swap successfully today by putting a phase-angle controller on my
bulb-suction desoldering tool and finding the just-right heat setting. I
also turned a new tip shape in a l lathe, which also seemed to make a
difference. I got pretty good results by taking my time on each pin. It's
just not an ergonomically designed tool, and after an hour of multiple tries
on 40 pins, my hand had done enough for one afternoon.

> Are you close to anyone who has a decent desoldering station - and is
> experienced in its use?  The tools are one thing - knowing
> just how the
> lead feels when the solder is melted clean to the top of the board is
> something else entirely.

I never thought I would be doing much of this again, so I'll have to invest
in some new tools. The only thing close to a soldering station around my
town are probably branding irons for livestock.

>
> If you want to purchase a tool - take a close look at the
> shop-air powered
> Weller DS-100.  It is relatively inexpensive and the vacuum has a
> respectable rise time.  The shop-air powered Metcal has a
> similar vacuum
> rise time and is much better than the Weller when desoldering
> multi-layer
> boards but costs at least triple the Weller unit.  Watch out
> for units that
> have built-in electric vacuum pumps - the vacuum rise time is
> often too
> slow and you do not get a nice clean hole.

Exactly the kind of advice I can use. The last time I purchased a tool for
desoldering DIPS, I got what was then a new concept tool - a table-top
reflow station. That was in '77. Looking around, the whole idea seems to
have become obsolete.

> If a
> pin is not free, re-solder the lead, then desolder it again.
> You need to
> have enough solder in the hole so that the desoldering tip
> has good thermal
> contact with and makes a good seal against the pad.

I made a small radiused shape on the tip, and I think it sealed better that
way - makes sense. If the suction actually gets to pull through the hole,
less solder should remain.
Is that what you mean?


> partially desoldered
> lead is a real bear to free so don't try.  Fill the hole with
> fresh solder
> and try again.

This works with solder wick too, but how nice it is to get it on the first
try
those "try again's" are killer on pad adhesion!

I'm embarrassed to say that back in the 70's I ran a repair dep't for a
major commercial electronics house. - I had ten or fifteen people on any
given day troubleshooting boards and desoldering parts by the hundreds. Only
now am I learning how difficult their jobs were.

This, I fear is only a symptom of my real problem:
I need a better revision control system - and one that will fit all kinds of
micros with all done with all different compilers and languages. The
standard method of organizing MPASM files seems to leave a bit to be
desired.
This sounds like a new topic though.   Maybe tomorrow.....


Thanks for the advice Dwayne. I start tool shopping tomorrow.
Do you have any thoughts on desoldering tools that also can function as a
hot-air reflow pen?
Sounds like it would be a useful feature for the SMT's?

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu