Pad-lifting

[John Robertson]

On 02/09/2016 2:29 PM, Jon Elson wrote:

John Robertson wrote:


I HAVE a Pace Desoldering station (actually two of them) - however I am
usually just removing one or two ICs and I can remove them with my
Weller (#7!) and Soldapullt faster than the Pace will heat up!

Yes, this is absolutely true! But, for something really expensive, or where
I have a lot of pins to desolder, I take the time to warm up the Pace, and
always get GREAT results. Usually the part just falls off the board when
the last pin is desoldered.
You can get a nice rhythm going where you heat two leads at the same
time (medium tip) and suck both together, then while the next pair are
warming up you are reloadng the sucker with your other hand. I can pull
a 40 pin chip in a minute or less typically (not that I ever time
myself, it just seems to go pretty fast.).

Once the legs are unsoldered I then use a tiny screwdriver to push the
bottom leads back and forth across the feed through hole. If it appears
to be stuck I put a dab of solder and resuck.
With the Pace, and the technique of orbiting the tip while applying suction,
I RARELY have this happen. Usually, I desolder the whole chip and it just
falls off the board. That wigglign back and forth can damage the plated
barrel of the hole.

Jon

When you are 'orbiting' I take that to mean that you are applying side
pressure to the leg of the device to move it far enough away from the
walls of the tube that the solder is removed completely and the leg has
no sticking point to the tube. That is the same process I use.

I just like using the Soldapullt, it is faster and when done with a bit
of experience (35 years in my case) gives very good consistent results
when extracting one or two ICs at a time. I train students to use the
Soldapullt in under a week - give them some bunged up boards to learn
how to remove parts without damaging the parts or the PCB. They learn
quickly and most can do a good job with only a day or so of practice.

When they get good with the Soldapullt I then train them on the Pace!

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Sjouke Burry]

On 10.02.16 2:07, Bob Engelhardt wrote:

Has anyone ever used pressure to blow away solder? I'm thinking that
125 psi through a tiny nozzle would clean out the solder better than a
spring loaded solder sucker.

Though I guess that it might send molten solder where you don't want it!

Bob

It WILL send it all over the place.
Nice way though to destroy a board.......

 

[frank]

Bob Engelhardt <BobEngelhardt@comcast.net> wrote:

Has anyone ever used pressure to blow away solder? I'm thinking that
125 psi through a tiny nozzle would clean out the solder better than a
spring loaded solder sucker.

Though I guess that it might send molten solder where you don't want it!

I tried that once on a board that was hopeless and marked for "spare parts"
only.
When blowing from the bottom side, the ICs would come out full of solder
residuals on the bottom side (cleaning required a longer time than using a
proper desolder method).
When blowing from the upper side (IC side), the action was not so effective in
removing all the solder from the hole and anyway the solder residues were
blown everywhere in the bench.
In short, I've never tried that again.

Frank IZ8DWF

 

[John-Del]

On Tuesday, February 9, 2016 at 1:29:13 PM UTC-5, Jeff Liebermann wrote:

6. Hit the connection with some solder before unsoldering to make the
old solder flow. Slopping flux on the pad doesn't help because the
flux will vaporize before the solder melts.

Adding fresh solder adds flux assuming you are using a flux core solder. While the carrier will vaporize, the flux solids remain. I always deflux when the repair is completed.

I'm undecided if hot air desoldering is any better than a soldering
sucker for through hole parts.

Not sure either, but I often use hot air to preheat the area before using the iron. Nothing ruins desoldering faster than heat sinking.

 

[Julian Barnes]

On Wed, 10 Feb 2016 04:41:37 -0800, John-Del wrote:

Not sure either, but I often use hot air to preheat the area before
using the iron. Nothing ruins desoldering faster than heat sinking.

And nothing ruins germanium semis faster than NOT heat sinking.

 

[John-Del]

On Wednesday, February 10, 2016 at 8:38:54 AM UTC-5, Julian Barnes wrote:

On Wed, 10 Feb 2016 04:41:37 -0800, John-Del wrote:

Not sure either, but I often use hot air to preheat the area before
using the iron. Nothing ruins desoldering faster than heat sinking.

And nothing ruins germanium semis faster than NOT heat sinking.

Not sure of your point, but what I'm referring to is the heat sink action of a multi layer PC with a huge ground plane running on or in it. Placing a soldering tip on some points can actually freeze the tip to the joint in worse cases, or prevent complete solder melting inside a plated through hole.. Anybody who has replaced an IPM on an LG sustain board can attest to this. Preheating the board minimizes excessive loss of desoldering tip heat to surrounding areas.

 

[Chuck]

On Tue, 9 Feb 2016 21:10:14 -0000, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:Xjsuy.834766$QP2.201595@fx42.am4...


"Jon Elson" wrote in message
news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.
OY! It depends a lot on the quality of the board, and then how much heat
it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the body.
You only have to do this on one side of a SOIC. Then scribe the other
side
and bend the IC up and down a few times, until it breaks off completely.
Then, the individual leads can be removed in a much more gentle fashion.
Avoid pressing down on the pads, they will tend to "crumple" and the edges
pull up from the board.








I still use a similar method when it suits.
Get a new blade in your knife, and you can quite easily cut vertically
through all the pins on any sized DIL (or SMD) device with no damage to
the PCB, with a bit of practice of course.

There's a bit of a knack to it, you carve through the pins at a slight angle
and make sure the blade edge lands squarely on the PCB underneath without
any sliding/slicing motion.

If you avoided using too much force, any tracks underneath usually survive
unscathed.

One trick I've heard about, is to feed some thin wire under an SMD chip and
ease it out sideways while applying heat, lifting the pins as it goes - but
this doesn't exactly fit in with the advice to minimise the duration of
applied heat. It probably wouldn't help at all if the pads are fragile to
start with.

I used to use this technique. Usually on 64 pin or more chips at
least one trace would lift.

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Jon Elson]

John Robertson wrote:

When you are 'orbiting' I take that to mean that you are applying side
pressure to the leg of the device to move it far enough away from the
walls of the tube that the solder is removed completely and the leg has
no sticking point to the tube. That is the same process I use.

Right, you make the desoldering iron tip push the pin in a circular movement
while the suction is operating. This is the technique described in the Pace
manual, and it REALLY works!

I just like using the Soldapullt, it is faster and when done with a bit
of experience (35 years in my case) gives very good consistent results
when extracting one or two ICs at a time.

Well, I rework some prety expensive boards for physics research gear. One
thing I've done a lot of is recovering $10 connectors with 68 pins. The
problem is not the cost of ONE connector, but the distributors make you buy
160 pieces minimum order! That does get expensive. We have piles of old
boards that have been superseded with newer designs. I can desolder the
connectors in about 10 minutes with the Pace. The boards would be usable if
we wanted to do that, but the evidence of the desoldering would be visible.
I'd hate to try doing a 68-pin connector with a spring-piston solder puller.

Jon

 

[Ian Field]

"Julian Barnes" <jb9889@notformail.com> wrote in message
news:n9febt$jch$3@dont-email.me...

On Wed, 10 Feb 2016 04:41:37 -0800, John-Del wrote:

Not sure either, but I often use hot air to preheat the area before
using the iron. Nothing ruins desoldering faster than heat sinking.

And nothing ruins germanium semis faster than NOT heat sinking.

The early Japanese radios had the transistors mounted almost flush - I
wonder how they got shunts onto those tiny short leads?

 

[Ian Field]

"Chuck" <chuck@mydeja.net> wrote in message
news:e2lmbbta8apbo3pu1qb16rq86e66sakka1@4ax.com...

On Tue, 9 Feb 2016 21:10:14 -0000, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:Xjsuy.834766$QP2.201595@fx42.am4...


"Jon Elson" wrote in message
news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more
than
just component leads? Most of the stuff I work on is at *least* 25
years
old and things start to get fragile.
OY! It depends a lot on the quality of the board, and then how much
heat
it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the
body.
You only have to do this on one side of a SOIC. Then scribe the other
side
and bend the IC up and down a few times, until it breaks off completely.
Then, the individual leads can be removed in a much more gentle fashion.
Avoid pressing down on the pads, they will tend to "crumple" and the
edges
pull up from the board.








I still use a similar method when it suits.
Get a new blade in your knife, and you can quite easily cut vertically
through all the pins on any sized DIL (or SMD) device with no damage to
the PCB, with a bit of practice of course.

There's a bit of a knack to it, you carve through the pins at a slight
angle
and make sure the blade edge lands squarely on the PCB underneath without
any sliding/slicing motion.

If you avoided using too much force, any tracks underneath usually survive
unscathed.

One trick I've heard about, is to feed some thin wire under an SMD chip
and
ease it out sideways while applying heat, lifting the pins as it goes -
but
this doesn't exactly fit in with the advice to minimise the duration of
applied heat. It probably wouldn't help at all if the pads are fragile to
start with.

I used to use this technique. Usually on 64 pin or more chips at
least one trace would lift.

If the chip is scrap; shear the pins off at the header, You can flow fresh
solder over the pin debris and surface tension them up on the tip of the
iron.

If the board is scrap, I usually use a modelers pencil blowtorch on the
other side - a regular blowtorch or hot air gun are other options.

 

[Ian Field]

"Bob Engelhardt" <BobEngelhardt@comcast.net> wrote in message
news:n9e2g702at0@news4.newsguy.com...

Has anyone ever used pressure to blow away solder? I'm thinking that 125
psi through a tiny nozzle would clean out the solder better than a spring
loaded solder sucker.

Though I guess that it might send molten solder where you don't want it!

Years ago I got the compressor from a scrap fridge, coiled up the pipe and
wedged it in the grille of a portable LPG heater with a carburettor jet
peened into the end.

It worked well harvesting from all SMD boards, but I was getting toasted
using it.

 

[John Robertson]

On 02/10/2016 10:21 AM, Jon Elson wrote:

John Robertson wrote:

....
Well, I rework some prety expensive boards for physics research gear. One
thing I've done a lot of is recovering $10 connectors with 68 pins. The
problem is not the cost of ONE connector, but the distributors make you buy
160 pieces minimum order! That does get expensive. We have piles of old
boards that have been superseded with newer designs. I can desolder the
connectors in about 10 minutes with the Pace. The boards would be usable if
we wanted to do that, but the evidence of the desoldering would be visible.
I'd hate to try doing a 68-pin connector with a spring-piston solder puller.

Jon

Yeah, I would not attempt something like those 68-pin or ICs with the
tiny pins, etc. with the Soldapullt.

When it gets down to it we use five basic methods of desoldering devices
in the order of use on my bench:

1) Weller and Soldapullt

2) Pace desoldering station

3) Weller and solder wick

4) Weller and Chip-Quik surface mount desolder kit. This has an alloy
rod that greatly reduces the melting point of the solder and is used on
very fragile items and small surface mount repairs.

5) Hot Lamp surface mount station (we really get very little surface
mount work).

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[John Robertson]

On 02/10/2016 3:29 AM, frank wrote:

Bob Engelhardt <BobEngelhardt@comcast.net> wrote:
Has anyone ever used pressure to blow away solder? I'm thinking that
125 psi through a tiny nozzle would clean out the solder better than a
spring loaded solder sucker.

Though I guess that it might send molten solder where you don't want it!

I tried that once on a board that was hopeless and marked for "spare parts"
only.
When blowing from the bottom side, the ICs would come out full of solder
residuals on the bottom side (cleaning required a longer time than using a
proper desolder method).
When blowing from the upper side (IC side), the action was not so effective in
removing all the solder from the hole and anyway the solder residues were
blown everywhere in the bench.
In short, I've never tried that again.

Frank IZ8DWF

I've used the propane (using MAPP gas tank) torch method on boards that
are to be scrapped - heat the bottom side of the board fast and very
hot, bang the board (IC legs down) onto a piece of wood to drive the
molten solder off the bottom, then retrieve the released parts.

Makes a mess of the PCB, but the ICs are usually fine. At least it is quick!

John ;-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[MJC]

In article <TpudnRkpEIE74ibLnZ2dnUU7-S2dnZ2d@giganews.com>, elson@pico-
systems.com says...

The problem is not the cost of ONE connector, but the distributors
make you buy 160 pieces minimum order! That does get expensive.

As a private individual repairing my own kit I have met that problem
too. If you can find a sympathetic salesperson you could try asking for
a "sample"...

Mike.

 

[Ralph Mowery]

"MJC" <gravity@mjcoon.plus.com> wrote in message
news:MPG.3125c86b6df9a24f3@news.plus.net...

In article <TpudnRkpEIE74ibLnZ2dnUU7-S2dnZ2d@giganews.com>, elson@pico-
systems.com says...
The problem is not the cost of ONE connector, but the distributors
make you buy 160 pieces minimum order! That does get expensive.


As a private individual repairing my own kit I have met that problem
too. If you can find a sympathetic salesperson you could try asking for
a "sample"...

Some of that has aslways been a sore spot with me. The companies should be
required to sell any parts to an individual to do their own repair.
I went with a man to help him pick up some boat motor parts. A man off the
street wanted to buy some small part of about $ 20. They would not sell it
to him. So we bought the part and then sold it to him. If not for us, he
would have had a hard time getting that part.

I have called some companies and received small parts with no problem.
Needed a special transistor for a $ 1500 radio. Called Icom and ordered two
of them and the postage and parts was about $ 5. No rip off at all from
them.

 

[Michael A. Terrell]

Ralph Mowery wrote:

"MJC" <gravity@mjcoon.plus.com> wrote in message
news:MPG.3125c86b6df9a24f3@news.plus.net...
In article <TpudnRkpEIE74ibLnZ2dnUU7-S2dnZ2d@giganews.com>, elson@pico-
systems.com says...
The problem is not the cost of ONE connector, but the distributors
make you buy 160 pieces minimum order! That does get expensive.


As a private individual repairing my own kit I have met that problem
too. If you can find a sympathetic salesperson you could try asking for
a "sample"...

Some of that has aslways been a sore spot with me. The companies should be
required to sell any parts to an individual to do their own repair.
I went with a man to help him pick up some boat motor parts. A man off the
street wanted to buy some small part of about $ 20. They would not sell it
to him. So we bought the part and then sold it to him. If not for us, he
would have had a hard time getting that part.

I have called some companies and received small parts with no problem.
Needed a special transistor for a $ 1500 radio. Called Icom and ordered two
of them and the postage and parts was about $ 5. No rip off at all from
them.

I once needed some microwave transistors from Rockwell-Collins. They
wanted $1500 each, and I had to buy 15 of them. The deliver date was
almost a year away. Needless to say, I scrapped a lot of their $4,000
radios. I replaced them with new Microdyne 1100LPR receivers for under
$1200 each. The new units were agile, with a digital tuner. The older
$4,000 units were tunable, but they needed an input filter for whatever
frequency you needed. We had a lot higher quality signal from the new
equipment, and it ran a lot cooler.

 

[Mike Tomlinson]

En el artículo <OfednbmKe8k3yyfLnZ2dnUU7-WudnZ2d@giganews.com>, John
Robertson <spam@flippers.com> escribió:

Once the legs are unsoldered I then use a tiny screwdriver to push the
bottom leads back and forth across the feed through hole. If it appears
to be stuck I put a dab of solder and resuck. Then I press the bottom of
each leg on the top side where they meet the PCB to again loosen them
up. At this point the IC usually pulls out with my finger tips.

I can confirm this method works beautifully. It feels like a waste of
time 'testing' each pin, but being able to lift the IC out undamaged and
the pins straight with fingertips makes it worth it, especially if
you're trying to save the IC. It also prevents pulling out the plating
'tube' with plated-through holes. My heart always sank when that
happened.

--
(\_/)
(='.'=) Bunny says: Windows 10? Nein danke!
(")_(")

 

[Ian Field]

"Mike Tomlinson" <mike@jasper.org.uk> wrote in message
newsP0AXGYEFPvWFwKR@jasper.org.uk...

En el artículo <OfednbmKe8k3yyfLnZ2dnUU7-WudnZ2d@giganews.com>, John
Robertson <spam@flippers.com> escribió:

Once the legs are unsoldered I then use a tiny screwdriver to push the
bottom leads back and forth across the feed through hole. If it appears
to be stuck I put a dab of solder and resuck. Then I press the bottom of
each leg on the top side where they meet the PCB to again loosen them
up. At this point the IC usually pulls out with my finger tips.

I can confirm this method works beautifully. It feels like a waste of
time 'testing' each pin, but being able to lift the IC out undamaged and
the pins straight with fingertips makes it worth it, especially if
you're trying to save the IC. It also prevents pulling out the plating
'tube' with plated-through holes. My heart always sank when that
happened.

As long as the pads on both sides have tracks, its fairly easy to repair
with a strand of wire - unless its a multilayer board with internal
connections to that via!

 

[John-Del]

On Saturday, February 13, 2016 at 4:47:29 AM UTC-5, Mike Tomlinson wrote:

En el artículo <Z67vy.866518$QP2.290161@fx42.am4>, Ian Field <gangprobi
ng.alien@ntlworld.com> escribió:

As long as the pads on both sides have tracks, its fairly easy to repair
with a strand of wire

Yes, or make sure the pin is soldered both top and bottom.

- unless its a multilayer board with internal
connections to that via!

If that happens, it's sayonara, I think.

I had a Samsung multi layer board that was working but quit after I replaced a typical leaded electrolytic that was vented a bit. Top and bottom connections fine but the middle layer was not. Several reheats did not fix it.

Fortunately I had a working board and I used a DMM on the diode scale (for the audible) and attached one lead to the cap in question and I waltzed the other lead around the board on every point until I found a zero ohm connection that did not exist on the damaged board. Running an external jumper fixed it.

 

[Mike Tomlinson]

En el artículo <Z67vy.866518$QP2.290161@fx42.am4>, Ian Field <gangprobi
ng.alien@ntlworld.com> escribió:

As long as the pads on both sides have tracks, its fairly easy to repair
with a strand of wire

Yes, or make sure the pin is soldered both top and bottom.

- unless its a multilayer board with internal
connections to that via!

If that happens, it's sayonara, I think.

--
(\_/)
(='.'=) Bunny says: Windows 10? Nein danke!
(")_(")