SMT de-soldering

[Michael A. Terrell]

Rich Webb wrote:

On Sun, 28 Jun 2009 13:50:33 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Baron wrote:

Bob Engelhardt wrote:

I have an SMT board with a jumper in the form of a 0 ohm resistor. I
need to remove it, but I've never done anything with SMT. Is there
anything special that I need to know? I'm planning on de-soldering
it.

Thanks,
Bob

I have a worn out soldering iron bit with the end cut back and a slot
filed across it, just a fraction bigger than an 0805 component that I
use to remove that size parts. The main issue is with parts that are
glued down. It takes a lot of heat to break that bond.

Usually the part being removed remains in the solder on the end of the
tip but brushes out on the wet sponge.


That's why I use a pair of irons. Its easy to drop the removed part
on the corner of the PC board, or bench so it doesn't get too hot.

Or use one of these gizmos. Several vendors carry them and their
relatives, styles from open-loop AC to temperature controlled DC models
for various solder stations.

I suck using chopsticks. Can't imagine I'd have better luck coordinating
a pair of soldering irons but the tweezer style is easy.

You use the pair of chopsticks in one hand, and the solder irons in
two. I did my work under a stereo microscope. A also had three to five
soldering irons on my bench at a time. Unless you have extremely poor
motor control, it only takes a few minutes to learn the technique.

http://www.web-tronics.com/sostwsmdhott.html (Other vendors, just an
example)

I've never used one, but I'm familiar with them. I could move the tip
less than a thousandth of an inch by watching it through the microscope.
I had some .015" Multicore rework solder, and a lot of the ICs I worked
with had their pins on .015" center to center.

I did like the Pomona tweezer probes for checking resistors &
capacitors. One of the early digital capacitance meters had a zero
adjust that let you null out the cable.


--
You can't have a sense of humor, if you have no sense!

 

[Baron]

Rich Webb wrote:

On Sun, 28 Jun 2009 13:50:33 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Baron wrote:

Bob Engelhardt wrote:

I have an SMT board with a jumper in the form of a 0 ohm resistor.
I
need to remove it, but I've never done anything with SMT. Is
there
anything special that I need to know? I'm planning on
de-soldering it.

Thanks,
Bob

I have a worn out soldering iron bit with the end cut back and a
slot filed across it, just a fraction bigger than an 0805 component
that I
use to remove that size parts. The main issue is with parts that
are
glued down. It takes a lot of heat to break that bond.

Usually the part being removed remains in the solder on the end of
the tip but brushes out on the wet sponge.


That's why I use a pair of irons. Its easy to drop the removed
part
on the corner of the PC board, or bench so it doesn't get too hot.

Or use one of these gizmos. Several vendors carry them and their
relatives, styles from open-loop AC to temperature controlled DC
models for various solder stations.

I suck using chopsticks. Can't imagine I'd have better luck
coordinating a pair of soldering irons but the tweezer style is easy.

http://www.web-tronics.com/sostwsmdhott.html (Other vendors, just an
example)

Hey thats neat ! I wonder, how does it cope with glue bonded
components ?
I find that I have to give a slight twist to detach them once the solder
has melted.

--
Best Regards:
Baron.

 

[Baron]

Michael A. Terrell wrote:

Rich Webb wrote:

On Sun, 28 Jun 2009 13:50:33 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Baron wrote:

Bob Engelhardt wrote:

I have an SMT board with a jumper in the form of a 0 ohm
resistor. I
need to remove it, but I've never done anything with SMT. Is
there
anything special that I need to know? I'm planning on
de-soldering it.

Thanks,
Bob

I have a worn out soldering iron bit with the end cut back and a
slot filed across it, just a fraction bigger than an 0805
component that I
use to remove that size parts. The main issue is with parts that
are
glued down. It takes a lot of heat to break that bond.

Usually the part being removed remains in the solder on the end of
the tip but brushes out on the wet sponge.


That's why I use a pair of irons. Its easy to drop the removed
part
on the corner of the PC board, or bench so it doesn't get too hot.

Or use one of these gizmos. Several vendors carry them and their
relatives, styles from open-loop AC to temperature controlled DC
models for various solder stations.

I suck using chopsticks. Can't imagine I'd have better luck
coordinating a pair of soldering irons but the tweezer style is easy.


You use the pair of chopsticks in one hand, and the solder irons in
two. I did my work under a stereo microscope. A also had three to
five
soldering irons on my bench at a time. Unless you have extremely poor
motor control, it only takes a few minutes to learn the technique.

http://www.web-tronics.com/sostwsmdhott.html (Other vendors, just an
example)


I've never used one, but I'm familiar with them. I could move the
tip
less than a thousandth of an inch by watching it through the
microscope. I had some .015" Multicore rework solder, and a lot of the
ICs I worked with had their pins on .015" center to center.

I did like the Pomona tweezer probes for checking resistors &
capacitors. One of the early digital capacitance meters had a zero
adjust that let you null out the cable.

How did you handle glued down component removal, particularly when there
is a track running under the part ? In the early days of learning how
to repair this stuff the section of track under the part often came
away when the part was lifted.

--
Best Regards:
Baron.

 

[Rich Webb]

On Sun, 28 Jun 2009 22:11:52 +0100, Baron
<baron.nospam@linuxmaniac.nospam.net> wrote:

Rich Webb wrote:

Or use one of these gizmos. Several vendors carry them and their
relatives, styles from open-loop AC to temperature controlled DC
models for various solder stations.

I suck using chopsticks. Can't imagine I'd have better luck
coordinating a pair of soldering irons but the tweezer style is easy.

http://www.web-tronics.com/sostwsmdhott.html (Other vendors, just an
example)


Hey thats neat ! I wonder, how does it cope with glue bonded
components ?
I find that I have to give a slight twist to detach them once the solder
has melted.

You would have about as much grip as with a pair of not terribly well
aligned, smooth jawed, needle nose pliers. Enough for a twisting moment
that could loosen the glue but don't expect to pick the board off the
deck if the part was really secure in place.

If you know ahead of time that there is glue under the parts, preheating
the board might help to soften the adhesion.

--
Rich Webb Norfolk, VA

 

[David L. Jones]

Bob Engelhardt wrote:

I have an SMT board with a jumper in the form of a 0 ohm resistor. I
need to remove it, but I've never done anything with SMT. Is there
anything special that I need to know? I'm planning on de-soldering
it.

Best solution, two soldering irons - essential for SMD work really.
Alternatively you can put a big blob of solder over the part and heat it all
up at once. Or heat one end and and then the other end alternatively until
it eventually falls off. This can be a problem on bad quality FR4 boards as
it might lift the pads.

Dave..

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/

 

[Michael A. Terrell]

Baron wrote:

How did you handle glued down component removal, particularly when there
is a track running under the part ? In the early days of learning how
to repair this stuff the section of track under the part often came
away when the part was lifted.

We never used that method in our products. Any glue was a drop on
one side of a component, or in the case of a large chip like a 144 pin
MPU, a drop on opposite corners. All our boards were built, in house
and met NASA standards. Glue under components is supposed to be used on
throwaway boards, only. The glue is also supposed to soften with heat,
but some assembly houses used cheaper adhesives that weren't thermal
release. Even with glue under consumer electronics I've repaired, a
slight twisting of the hot ceramic body would generally break the bond.


--
You can't have a sense of humor, if you have no sense!

 

[Electronworks.co.uk]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:4A469BDB.BFC895D@earthlink.net...

"Electronworks.co.uk" wrote:

"Bob Engelhardt" <bobengelhardt@comcast.net> wrote in message
news:h25pp702rpc@news3.newsguy.com...
I have an SMT board with a jumper in the form of a 0 ohm resistor. I
need
to remove it, but I've never done anything with SMT. Is there anything
special that I need to know? I'm planning on de-soldering it.

Thanks,
Bob

Get a fine tipped soldering iron, heat up one side until it melts, then
quickly heat up the other side. Swap your soldering iron between one side
and the other and eventually the part will come off


That is a great way to lift pads & traces off a PC board. Use a pair
of irons, and lift the resistor as soon as the solder liquefies on both
sides. If you have to put it back, a small drop of liquid RMA (Rosin,
Mildly Activated) liquid flux, and the pair of irons will reflow the
solder. Surface tension will center the ends, so there is no need to
worry about trying to position it exactly. Remove one iron. As soon as
that end solidifies, remove the other. The rosin will remove any oxides
from the existing solder. it takes longer to write about it, than to do
it.

I did a lot of this for four years at Microdyne (Now part of L3
Communications) as a production test tech, and engineering tech.


--
You can't have a sense of humor, if you have no sense!

Pah! Nonsense!

I've done it loads of times and never had a problem.

The best way is of course to use 2 irons, but many people do not have access
to 2 soldering irons

--
Bill Naylor
www.electronworks.co.uk
Electronic Kits for Education and Fun

 

[Michael A. Terrell]

"Electronworks.co.uk" wrote:

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:4A469BDB.BFC895D@earthlink.net...

"Electronworks.co.uk" wrote:

"Bob Engelhardt" <bobengelhardt@comcast.net> wrote in message
news:h25pp702rpc@news3.newsguy.com...
I have an SMT board with a jumper in the form of a 0 ohm resistor. I
need
to remove it, but I've never done anything with SMT. Is there anything
special that I need to know? I'm planning on de-soldering it.

Thanks,
Bob

Get a fine tipped soldering iron, heat up one side until it melts, then
quickly heat up the other side. Swap your soldering iron between one side
and the other and eventually the part will come off


That is a great way to lift pads & traces off a PC board. Use a pair
of irons, and lift the resistor as soon as the solder liquefies on both
sides. If you have to put it back, a small drop of liquid RMA (Rosin,
Mildly Activated) liquid flux, and the pair of irons will reflow the
solder. Surface tension will center the ends, so there is no need to
worry about trying to position it exactly. Remove one iron. As soon as
that end solidifies, remove the other. The rosin will remove any oxides
from the existing solder. it takes longer to write about it, than to do
it.

I did a lot of this for four years at Microdyne (Now part of L3
Communications) as a production test tech, and engineering tech.

Pah! Nonsense!

I don't remember you working the test production line. How many
circuit boards that cost over $8,000 (EIGHT THOUSAND US DOLLARS) to
build have you worked on? How much work have you done for NASA or the
ESA? I've done both, at Microdyne.

I've done it loads of times and never had a problem.

Of course you haven't. You're special. Now its time for your nap,
recess is over.

The best way is of course to use 2 irons, but many people do not have access
to 2 soldering irons.

Anyone that can't afford two ESD rated soldering irons shouldn't be
messing with SMD components.

--
Bill Naylor
www.electronworks.co.uk
Electronic Kits for Education and Fun

--
You can't have a sense of humor, if you have no sense!

 

[Baron]

Michael A. Terrell wrote:

Baron wrote:

How did you handle glued down component removal, particularly when
there
is a track running under the part ? In the early days of learning
how to repair this stuff the section of track under the part often
came away when the part was lifted.


We never used that method in our products. Any glue was a drop on
one side of a component, or in the case of a large chip like a 144 pin
MPU, a drop on opposite corners. All our boards were built, in house
and met NASA standards. Glue under components is supposed to be used
on throwaway boards, only. The glue is also supposed to soften with
heat, but some assembly houses used cheaper adhesives that weren't
thermal release. Even with glue under consumer electronics I've
repaired, a slight twisting of the hot ceramic body would generally
break the bond.

I suspected as much ! That slight twist seems to be needed most times.
Its just a nuisance when the track underneath gets twisted off because
the glue hasn't let go.

--
Best Regards:
Baron.

 

[Baron]

Rich Webb wrote:

On Sun, 28 Jun 2009 22:11:52 +0100, Baron
baron.nospam@linuxmaniac.nospam.net> wrote:

Rich Webb wrote:

Or use one of these gizmos. Several vendors carry them and their
relatives, styles from open-loop AC to temperature controlled DC
models for various solder stations.

I suck using chopsticks. Can't imagine I'd have better luck
coordinating a pair of soldering irons but the tweezer style is
easy.

http://www.web-tronics.com/sostwsmdhott.html (Other vendors, just an
example)


Hey thats neat ! I wonder, how does it cope with glue bonded
components ?
I find that I have to give a slight twist to detach them once the
solder has melted.

You would have about as much grip as with a pair of not terribly well
aligned, smooth jawed, needle nose pliers. Enough for a twisting
moment that could loosen the glue but don't expect to pick the board
off the deck if the part was really secure in place.

If you know ahead of time that there is glue under the parts,
preheating the board might help to soften the adhesion.

I have tried various techniques which is how I ended up with a notched
soldering iron tip. Most of the time it doesn't matter if the
component gets damaged or destroyed, its going to be replaced anyway.
I hoped that someone had a tip to reduce or prevent damage to the tracks
under a glued down part.

I agree with Michael most consumer electronics is not intended to be
repaired and the glue used isn't intended to soften under heating.


--
Best Regards:
Baron.

 

[Baron]

David L. Jones wrote:

Bob Engelhardt wrote:
I have an SMT board with a jumper in the form of a 0 ohm resistor. I
need to remove it, but I've never done anything with SMT. Is there
anything special that I need to know? I'm planning on de-soldering
it.

Best solution, two soldering irons - essential for SMD work really.
Alternatively you can put a big blob of solder over the part and heat
it all up at once. Or heat one end and and then the other end
alternatively until it eventually falls off. This can be a problem on
bad quality FR4 boards as it might lift the pads.

Dave..

I have found that some of the larger 1206 & 0805 parts, if they are not
glued will conduct enough heat to melt the solder on both ends allowing
them to be brushed off the pcb lands.

Nice blogs by the way.

--
Best Regards:
Baron.

 

[Michael A. Terrell]

Baron wrote:

Michael A. Terrell wrote:


Baron wrote:

How did you handle glued down component removal, particularly when
there
is a track running under the part ? In the early days of learning
how to repair this stuff the section of track under the part often
came away when the part was lifted.


We never used that method in our products. Any glue was a drop on
one side of a component, or in the case of a large chip like a 144 pin
MPU, a drop on opposite corners. All our boards were built, in house
and met NASA standards. Glue under components is supposed to be used
on throwaway boards, only. The glue is also supposed to soften with
heat, but some assembly houses used cheaper adhesives that weren't
thermal release. Even with glue under consumer electronics I've
repaired, a slight twisting of the hot ceramic body would generally
break the bond.


I suspected as much ! That slight twist seems to be needed most times.
Its just a nuisance when the track underneath gets twisted off because
the glue hasn't let go.

The only thing I ever saw with enough glue to do that was a cheap car
radio. It was so poorly built that the fillets, and some components
cracked from vibration but the broken crap was still glued to the
board. It was first generation SMD, and reflowed with very low grade
solder. In this case it looked like the glue helped cause the failures.


--
You can't have a sense of humor, if you have no sense!

 

[David L. Jones]

Baron wrote:

David L. Jones wrote:

Bob Engelhardt wrote:
I have an SMT board with a jumper in the form of a 0 ohm resistor.
I need to remove it, but I've never done anything with SMT. Is
there anything special that I need to know? I'm planning on
de-soldering it.

Best solution, two soldering irons - essential for SMD work really.
Alternatively you can put a big blob of solder over the part and heat
it all up at once. Or heat one end and and then the other end
alternatively until it eventually falls off. This can be a problem on
bad quality FR4 boards as it might lift the pads.

Dave..


I have found that some of the larger 1206 & 0805 parts, if they are
not glued will conduct enough heat to melt the solder on both ends
allowing them to be brushed off the pcb lands.

Yes, I've found that too, although the trick is not lifting the pad with too
much heat.
A second soldering iron is an investment you'll never regret!

Nice blogs by the way.

Thanks!
They are crude but hopefully effective.
Getting a bit of a following now which is nice (and surprising).
Still trying to convince the wife I need a better camera and mic for my
"stupid blog thingy I'll loose interest in next week"!

Dave.
--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/

 

[baron]

David L. Jones Inscribed thus:

Baron wrote:
David L. Jones wrote:

Bob Engelhardt wrote:
I have an SMT board with a jumper in the form of a 0 ohm resistor.
I need to remove it, but I've never done anything with SMT. Is
there anything special that I need to know? I'm planning on
de-soldering it.

Best solution, two soldering irons - essential for SMD work really.
Alternatively you can put a big blob of solder over the part and
heat it all up at once. Or heat one end and and then the other end
alternatively until it eventually falls off. This can be a problem
on bad quality FR4 boards as it might lift the pads.

Dave..


I have found that some of the larger 1206 & 0805 parts, if they are
not glued will conduct enough heat to melt the solder on both ends
allowing them to be brushed off the pcb lands.

Yes, I've found that too, although the trick is not lifting the pad
with too much heat.
A second soldering iron is an investment you'll never regret!

I've half a dozen including a hot air one.
Trouble is every job seems to need the one you don't have !

Nice blogs by the way.

Thanks!
They are crude but hopefully effective.
Getting a bit of a following now which is nice (and surprising).
Still trying to convince the wife I need a better camera and mic for
my "stupid blog thingy I'll loose interest in next week"!

Dave.

Funny ! My missus says that to me when I want to spend money.

--
Best Regards:
Baron.

 

[Bob Engelhardt]

OK, it's done. No problems. I used 2 irons as suggested. Thanks for
the help. Bob

 

[Michael A. Terrell]

Bob Engelhardt wrote:

OK, it's done. No problems. I used 2 irons as suggested. Thanks for
the help. Bob

You're welcome, and you now have another new skill under your belt.



--
You can't have a sense of humor, if you have no sense!

 

[Daniel Mandic]

Jamie wrote:

and what the hell do you think they use 0 ohm R's for you moron.

Hmmm, they would need a temperature about 4-5 degrees....

~ S? How can that be?



Best regards,

Daniel Mandic