Maker Pro
Maker Pro

De-soldering ICs with a hot air gun.

N

N Cook

Jan 1, 1970
0
In response to someone who emailed me a couple of
months back saying he did not believe it
was possible to desolder , with a hot-air gun,
ICs soldered in plated through hole pcb boards,
without causing mayhem.
And anyone else who could use the technique.
The following is some before and after pics
of such a board this week, with thin tracks, through pin tracks and
a nearby via for good measure.
http://home.graffiti.net/diverse:graffiti.net/de_sol1.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol2.jpg
Masked off with the thick form of plummer's PTFE
tape to protect adjascent components from desoldering/
flicking off.
http://home.graffiti.net/diverse:graffiti.net/de_sol3.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol4.jpg
After blasting with hot-air and before cleaning
up the holes with a needle-point probe and soldering iron.
Usually the polyester of the pcb does not discolour, for
normal cheap IC soldering, but the plated-through
fixings mean more heat required than usual.
http://home.graffiti.net/diverse:graffiti.net/de_sol5.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol6.jpg
The converted circlip pliers extractor tool , with a close up
of the double joggled tips.
Lines of bending are at B-B and the red lines.
Graph paper is mm squares.

The full text for the tip
De-soldering ICs
Use a hot-air paint-stripper,1400W,500 degree centigrade,with 2 level heat
control to prolong element life. Activity may appear fearsome but it is no
worse than a flow-solder bath.Pre-heat for one minute then apply to
pcb,make extractor tool to pull ic from component side. Make an IC extractor
from an
old large pair,10 inch, of circlip pliers,the jaws need to open out enough
to clip around the ends of up to 64 pin ICs with enough force to overcome
the mechanical force of the situation where all the pins are angled relative
to the PCB holes.Forge around both of the
original circlip pins,one joggle at right angle to clear the heigth of the
ICs and a slight
inwards joggle to make purchase on the underside of the IC,grinding a wedge
angle to the
points helps particularly where there is no clearance between IC and pcb.
[ Because of these joggles this tool is also useful for depressing the rear
grippers and releasing of that type chassis mount fuseholders and switches
when internally surrounded by other
components ] . For awkward positions lock the pliers to the IC by wrapping
a cable tie around the handles, tighten, slide down and
add a couple of notches to the tie and force back along the handles.
Use this technique for salvaging (working order) up to 64 pin ics ( when
practised ),other
components, sm and even repair (tracks are not dislodged).For repair work
beware of spatter of molten solder causing solder bridges on adjascent
compoents because if you are doing the job properly,ie not dislodging pcb
tracks the IC must be pulled out with
some force and the board tends to flex so possibility of flicking solder.
Mask off surrounding areas with wide aluminium tape or thick plummer's PTFE
tape around both sides of board to avoid unsoldering
and flicking off nearby minor components and trap any that do.
The secret is to be as quick as possible,idealy the body of the extracted ic
will be just about handleable rather than too hot to touch.Try practising on
a board with close packed TTL chips or similar and aim for an extraction
rate of something like one every 2 seconds.Between boards keep the hot air
gun running on low power setting (not switching off).Don't rest the gun
against the board
when heating as vibration seems to affect the element life also don't allow
the board to
flex back onto the gun for the same reason.Hold the gun so airflow is angled
to the board as solder spat directly into the nozzle can kill the element.
About the only components that cannot be removed with this technique are
parts moulded in soft plastic,e.g. crystal sockets,rf coils with plastic
former
(IF coils usually OK) some DIP switches. Even these are desolderable intact
if the body of the component is previously cooled with a blast of aerosol
freezer spray.
You definitely need a tool to pull the IC off the board as soon as the
solder is non-solid/breaking up ie before even fully melted quite possibly.
An old pair of long nose pliers with the ends ground down so the remnant
tips can be bent inwards to grab the ends of the IC would probably be
sufficient to show the method works.
Also definitely practise on an old/scrap board first as it needs that
confidence because otherwise pointing a glowing hot element and 300 degree C
or more blast of hot air at a pcb is not a natural thing to do.
SAFETY NOTE:- ensure good ventilation, use safety goggles because trapped
water etc in the capaillary structure of glass fibre reinforced PCB can
super-heat to steam and jet out molten solder,also it is possible to
overlook
small electrolytic capacitors on the solder side of the board which of
coarse
explode with the direct heat of the hot air gun and beware of very
slight risk of combustion of adjascent flammable parts especially where
components have extra (un-noticed) mechanical bonding leading to extended
duration of heating activity.
 
B

Baron

Jan 1, 1970
0
N said:
In response to someone who emailed me a couple of
months back saying he did not believe it
was possible to desolder , with a hot-air gun,
ICs soldered in plated through hole pcb boards,
without causing mayhem.
And anyone else who could use the technique.
The following is some before and after pics
of such a board this week, with thin tracks, through pin tracks and
a nearby via for good measure.
http://home.graffiti.net/diverse:graffiti.net/de_sol1.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol2.jpg
Masked off with the thick form of plummer's PTFE
tape to protect adjascent components from desoldering/
flicking off.
http://home.graffiti.net/diverse:graffiti.net/de_sol3.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol4.jpg
After blasting with hot-air and before cleaning
up the holes with a needle-point probe and soldering iron.
Usually the polyester of the pcb does not discolour, for
normal cheap IC soldering, but the plated-through
fixings mean more heat required than usual.
http://home.graffiti.net/diverse:graffiti.net/de_sol5.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol6.jpg
The converted circlip pliers extractor tool , with a close up
of the double joggled tips.
Lines of bending are at B-B and the red lines.
Graph paper is mm squares.

The full text for the tip
De-soldering ICs
Use a hot-air paint-stripper,1400W,500 degree centigrade,with 2 level
heat
control to prolong element life. Activity may appear fearsome but it
is no
worse than a flow-solder bath.Pre-heat for one minute then apply to
pcb,make extractor tool to pull ic from component side. Make an IC
extractor from an
old large pair,10 inch, of circlip pliers,the jaws need to open out
enough to clip around the ends of up to 64 pin ICs with enough force
to overcome the mechanical force of the situation where all the pins
are angled relative to the PCB holes.Forge around both of the
original circlip pins,one joggle at right angle to clear the heigth of
the ICs and a slight
inwards joggle to make purchase on the underside of the IC,grinding a
wedge angle to the
points helps particularly where there is no clearance between IC and
pcb.
[ Because of these joggles this tool is also useful for depressing
[ the rear
grippers and releasing of that type chassis mount fuseholders and
switches when internally surrounded by other
components ] . For awkward positions lock the pliers to the IC by
wrapping a cable tie around the handles, tighten, slide down and
add a couple of notches to the tie and force back along the handles.
Use this technique for salvaging (working order) up to 64 pin ics (
when practised ),other
components, sm and even repair (tracks are not dislodged).For repair
work beware of spatter of molten solder causing solder bridges on
adjascent compoents because if you are doing the job properly,ie not
dislodging pcb tracks the IC must be pulled out with
some force and the board tends to flex so possibility of flicking
solder. Mask off surrounding areas with wide aluminium tape or thick
plummer's PTFE tape around both sides of board to avoid unsoldering
and flicking off nearby minor components and trap any that do.
The secret is to be as quick as possible,idealy the body of the
extracted ic will be just about handleable rather than too hot to
touch.Try practising on a board with close packed TTL chips or similar
and aim for an extraction rate of something like one every 2
seconds.Between boards keep the hot air gun running on low power
setting (not switching off).Don't rest the gun against the board
when heating as vibration seems to affect the element life also don't
allow the board to
flex back onto the gun for the same reason.Hold the gun so airflow is
angled to the board as solder spat directly into the nozzle can kill
the element. About the only components that cannot be removed with
this technique are parts moulded in soft plastic,e.g. crystal
sockets,rf coils with plastic former
(IF coils usually OK) some DIP switches. Even these are desolderable
intact if the body of the component is previously cooled with a blast
of aerosol freezer spray.
You definitely need a tool to pull the IC off the board as soon as the
solder is non-solid/breaking up ie before even fully melted quite
possibly. An old pair of long nose pliers with the ends ground down so
the remnant tips can be bent inwards to grab the ends of the IC would
probably be sufficient to show the method works.
Also definitely practise on an old/scrap board first as it needs that
confidence because otherwise pointing a glowing hot element and 300
degree C or more blast of hot air at a pcb is not a natural thing to
do. SAFETY NOTE:- ensure good ventilation, use safety goggles because
trapped water etc in the capaillary structure of glass fibre
reinforced PCB can super-heat to steam and jet out molten solder,also
it is possible to overlook
small electrolytic capacitors on the solder side of the board which of
coarse
explode with the direct heat of the hot air gun and beware of very
slight risk of combustion of adjascent flammable parts especially
where components have extra (un-noticed) mechanical bonding leading to
extended duration of heating activity.

FWIW A simple removal tool for use with this technique is a strip
of .75mm thick aluminium bent in a U shape with the ends of the U
folded under. Similar in fashion to the old keycap puller.
 
H

hr(bob) [email protected]

Jan 1, 1970
0
In response to someone who emailed me a couple of
months back saying he did not believe it
was possible to desolder , with a hot-air gun,
ICs soldered in plated through hole pcb boards,
without causing mayhem.
And anyone else who could use the technique.
The following is some before and after pics
of such a board this week, with thin tracks, through pin tracks and
a nearby via for good measure.http://home.graffiti.net/diverse:gr...graffiti.net/diverse:graffiti.net/de_sol2.jpg
Masked off with the thick form of plummer's PTFE
tape to protect adjascent components from desoldering/
flicking off.http://home.graffiti.net/diverse:gr...graffiti.net/diverse:graffiti.net/de_sol4.jpg
After blasting with hot-air and before cleaning
up the holes with a needle-point probe and soldering iron.
Usually the polyester of the pcb does not discolour, for
normal cheap IC soldering, but the plated-through
fixings mean more heat required than usual.http://home.graffiti.net/diverse:gr...graffiti.net/diverse:graffiti.net/de_sol6.jpg
The converted circlip pliers extractor tool , with a close up
of the double joggled tips.
Lines of bending are at B-B and the red lines.
Graph paper is mm squares.

The full text for the tip
De-soldering ICs
Use a hot-air paint-stripper,1400W,500 degree centigrade,with 2 level heat
control to prolong element life. Activity may appear fearsome but it is no
worse than a flow-solder bath.Pre-heat for one minute then apply to
pcb,make extractor tool to pull ic from component side. Make an IC extractor
from an
old large pair,10 inch, of circlip pliers,the jaws need to open out enough
to clip around the ends of up to 64 pin ICs with enough force to overcome
the mechanical force of the situation where all the pins are angled relative
to the PCB holes.Forge around both of the
original circlip pins,one joggle at right angle to clear the heigth of the
ICs and a slight
inwards joggle to make purchase on the underside of the IC,grinding a wedge
angle to the
points helps particularly where there is no clearance between IC and pcb.
[ Because of these joggles this tool is also useful for depressing the rear
grippers and releasing of that type chassis mount fuseholders and switches
when internally surrounded by other
components ] . For awkward positions lock the pliers to the IC by wrapping
a cable tie around the handles, tighten, slide down and
add a couple of notches to the tie and force back along the handles.
Use this technique for salvaging (working order) up to 64 pin ics ( when
practised ),other
components, sm and even repair (tracks are not dislodged).For repair work
beware of spatter of molten solder causing solder bridges on adjascent
compoents because if you are doing the job properly,ie not dislodging pcb
tracks the IC must be pulled out with
some force and the board tends to flex so possibility of flicking solder.
Mask off surrounding areas with wide aluminium tape or thick plummer's PTFE
tape around both sides of board to avoid unsoldering
and flicking off nearby minor components and trap any that do.
The secret is to be as quick as possible,idealy the body of the extracted ic
will be just about handleable rather than too hot to touch.Try practising on
a board with close packed TTL chips or similar and aim for an extraction
rate of something like one every 2 seconds.Between boards keep the hot air
gun running on low power setting (not switching off).Don't rest the gun
against the board
when heating as vibration seems to affect the element life also don't allow
the board to
flex back onto the gun for the same reason.Hold the gun so airflow is angled
to the board as solder spat directly into the nozzle can kill the element.
About the only components that cannot be removed with this technique are
parts moulded in soft plastic,e.g. crystal sockets,rf coils with plastic
former
(IF coils usually OK) some DIP switches. Even these are desolderable intact
if the body of the component is previously cooled with a blast of aerosol
freezer spray.
You definitely need a tool to pull the IC off the board as soon as the
solder is non-solid/breaking up ie before even fully melted quite possibly.
An old pair of long nose pliers with the ends ground down so the remnant
tips can be bent inwards to grab the ends of the IC would probably be
sufficient to show the method works.
Also definitely practise on an old/scrap board first as it needs that
confidence because otherwise pointing a glowing hot element and 300 degree C
or more blast of hot air at a pcb is not a natural thing to do.
SAFETY NOTE:- ensure good ventilation, use safety goggles because trapped
water etc in the capaillary structure of glass fibre reinforced PCB can
super-heat to steam and jet out molten solder,also it is possible to
overlook
small electrolytic capacitors on the solder side of the board which of
coarse
explode with the direct heat of the hot air gun and beware of very
slight risk of combustion of adjascent flammable parts especially where
components have extra (un-noticed) mechanical bonding leading to extended
duration of heating activity.

Norm:

Thanx for the step by step information. Your posts are always worth-
while. Is adjascent the UK spelling of adjacent?? <G>

H. R. (Bob) Hofmann
 
S

Smitty Two

Jan 1, 1970
0
Baron said:
N said:
In response to someone who emailed me a couple of
months back saying he did not believe it
was possible to desolder , with a hot-air gun,
ICs soldered in plated through hole pcb boards,
without causing mayhem.
And anyone else who could use the technique.
The following is some before and after pics
of such a board this week, with thin tracks, through pin tracks and
a nearby via for good measure.
http://home.graffiti.net/diverse:graffiti.net/de_sol1.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol2.jpg
Masked off with the thick form of plummer's PTFE
tape to protect adjascent components from desoldering/
flicking off.
http://home.graffiti.net/diverse:graffiti.net/de_sol3.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol4.jpg
After blasting with hot-air and before cleaning
up the holes with a needle-point probe and soldering iron.
Usually the polyester of the pcb does not discolour, for
normal cheap IC soldering, but the plated-through
fixings mean more heat required than usual.
http://home.graffiti.net/diverse:graffiti.net/de_sol5.jpg
http://home.graffiti.net/diverse:graffiti.net/de_sol6.jpg
The converted circlip pliers extractor tool , with a close up
of the double joggled tips.
Lines of bending are at B-B and the red lines.
Graph paper is mm squares.

The full text for the tip
De-soldering ICs
Use a hot-air paint-stripper,1400W,500 degree centigrade,with 2 level
heat
control to prolong element life. Activity may appear fearsome but it
is no
worse than a flow-solder bath.Pre-heat for one minute then apply to
pcb,make extractor tool to pull ic from component side. Make an IC
extractor from an
old large pair,10 inch, of circlip pliers,the jaws need to open out
enough to clip around the ends of up to 64 pin ICs with enough force
to overcome the mechanical force of the situation where all the pins
are angled relative to the PCB holes.Forge around both of the
original circlip pins,one joggle at right angle to clear the heigth of
the ICs and a slight
inwards joggle to make purchase on the underside of the IC,grinding a
wedge angle to the
points helps particularly where there is no clearance between IC and
pcb.
[ Because of these joggles this tool is also useful for depressing
[ the rear
grippers and releasing of that type chassis mount fuseholders and
switches when internally surrounded by other
components ] . For awkward positions lock the pliers to the IC by
wrapping a cable tie around the handles, tighten, slide down and
add a couple of notches to the tie and force back along the handles.
Use this technique for salvaging (working order) up to 64 pin ics (
when practised ),other
components, sm and even repair (tracks are not dislodged).For repair
work beware of spatter of molten solder causing solder bridges on
adjascent compoents because if you are doing the job properly,ie not
dislodging pcb tracks the IC must be pulled out with
some force and the board tends to flex so possibility of flicking
solder. Mask off surrounding areas with wide aluminium tape or thick
plummer's PTFE tape around both sides of board to avoid unsoldering
and flicking off nearby minor components and trap any that do.
The secret is to be as quick as possible,idealy the body of the
extracted ic will be just about handleable rather than too hot to
touch.Try practising on a board with close packed TTL chips or similar
and aim for an extraction rate of something like one every 2
seconds.Between boards keep the hot air gun running on low power
setting (not switching off).Don't rest the gun against the board
when heating as vibration seems to affect the element life also don't
allow the board to
flex back onto the gun for the same reason.Hold the gun so airflow is
angled to the board as solder spat directly into the nozzle can kill
the element. About the only components that cannot be removed with
this technique are parts moulded in soft plastic,e.g. crystal
sockets,rf coils with plastic former
(IF coils usually OK) some DIP switches. Even these are desolderable
intact if the body of the component is previously cooled with a blast
of aerosol freezer spray.
You definitely need a tool to pull the IC off the board as soon as the
solder is non-solid/breaking up ie before even fully melted quite
possibly. An old pair of long nose pliers with the ends ground down so
the remnant tips can be bent inwards to grab the ends of the IC would
probably be sufficient to show the method works.
Also definitely practise on an old/scrap board first as it needs that
confidence because otherwise pointing a glowing hot element and 300
degree C or more blast of hot air at a pcb is not a natural thing to
do. SAFETY NOTE:- ensure good ventilation, use safety goggles because
trapped water etc in the capaillary structure of glass fibre
reinforced PCB can super-heat to steam and jet out molten solder,also
it is possible to overlook
small electrolytic capacitors on the solder side of the board which of
coarse
explode with the direct heat of the hot air gun and beware of very
slight risk of combustion of adjascent flammable parts especially
where components have extra (un-noticed) mechanical bonding leading to
extended duration of heating activity.

FWIW A simple removal tool for use with this technique is a strip
of .75mm thick aluminium bent in a U shape with the ends of the U
folded under. Similar in fashion to the old keycap puller.

Um, IC pullers are $3.50. You have to be pretty dedicated to the DIY
approach to make your own.
 
N

N Cook

Jan 1, 1970
0
Smitty Two said:
Um, IC pullers are $3.50. You have to be pretty dedicated to the DIY
approach to make your own.

If you mean the likes of
http://www.maplin.co.uk/images/300/fd54j.jpg
then no - not man enough even for cheapo boards, certainly not for
plated-through extraction.
B&D first sold a hot air gun in the UK about 1982.
I bought one in something like 1985/6 and soon realised how useful it would
be for IC extraction. The one I made up, in the mid 1980s, has survived
perhaps 50,000 IC extractions. The handles were originally all black
enamelled, now bare metal.
Same can't be said for using the same gun - I would recomment Bosch or any
make that uses a ceramic matrix for the element, B & D still uses mica as
far as i know.
I'm only guessing on 50,000 but does include about 1500 , inch diameter , 6
inch long celluloid pill pots , on average 3/4 full of extracted, salvaged
and sorted ICs
 
M

Mark D. Zacharias

Jan 1, 1970
0
Just had to tell someone - I got a bright idea to remove a flyback
transformer using a paint stripper gun.

AMAZING. Had that FBT out of there in about 40 seconds - no need to fight
the thing clearing eyelets, etc.

Done it twice now. Works great. Surely someone here has done this, But I
work with a couple really experienced TV techs and they hadn't thought of it
before...

I would recommend watching out for any nearby SMD's, though...


Mark Z.
 
N

N Cook

Jan 1, 1970
0
Mark D. Zacharias said:
Just had to tell someone - I got a bright idea to remove a flyback
transformer using a paint stripper gun.

AMAZING. Had that FBT out of there in about 40 seconds - no need to fight
the thing clearing eyelets, etc.

Done it twice now. Works great. Surely someone here has done this, But I
work with a couple really experienced TV techs and they hadn't thought of it
before...

I would recommend watching out for any nearby SMD's, though...


Mark Z.

I've always used it for LOPT and pcb mounted mains ones and near enough
removing everything else except soft plastic enclosed components.

I very rarely use this SMD technique for more than 16 pin DIL format but it
does work for karger formats but I would not like to rely on any salvaged in
such manner.
Note the residual patterning in the solder, on the board, makes it a doddle
for replacing with a new one. Again you have to exert quite a pull on the IC
to keep IC heating time to a minimum. Another reason for making a strong IC
extractor tool for the basic DIL IC format removal.

Hint for de-soldering surface mount ICs.
Use a hot-air paint-stripper,1400W,500 degree centigrade,with 2 level heat
control to prolong element life.
Form a ring of silicone covered wire around the IC{to isolate the remaing
components on the pcb.Push a thin piece of wire
under one side of the IC and form a loop around the IC,repeat on the other
side;this is to remove the IC when the solder melts, tug on these wires
while
heating up to ensure minimum heating contact time.
Place a slab of PTFE with right size hole cut into and
clip pcb and slab together with clothes pegs/Bulldog clips etc.
If the IC is for re-use then cover body of IC with heat insulating material
or blast IC with freezer spray.Allow the hot-air gun to get up to heat{say 1
minute}
before applying to IC.
For more crowded boards make "conical" shrouds to surround the IC. I used
some PTFE strip that i had but thin paxolin or similar but drilled and wired
together would probably do. Cut 4 small trapezoids from the PTFE
or tin-plate and wire at the corners to form a
truncated pyramidal frustrum.
Fixed PTFE together with paper staples but for the smallest shroud
for 8 pin SM had to wire together the final join.
Tie to the PTFE/ tin-plate cone (to stop the blower blowing it off) with
copper wire or temporarily solder to distant points.
When practised the heated contact time should be less than
2 seconds - no board distortion or collateral damage surprisingly.
If you can't get the tugging wires under the IC then pass
under a few pins at each corner.
Because this tugging frees the IC at the earliest moment, the solder
on the board is not fully melted and leaves a profile for localising
the new IC in place and then solder pin by pin.
Even for thick board and plated-through holes
so only tips of IC leads protrude,
very thin signal traces, traces to tiny pads on both sides of boards of same
pin in some cases and plated vias under ICs as well. I know if i used
"proper " vacuum assist desolder or butcher-and-remove-single-pins , many of
those traces/pads would have dislodged.
I had to sharpen the points of my large adapted circlip pliers to get the
extra purchase on the ends of 14,16, and 28 pin ICs. Not one dislodged
track using a paint-strip hot-air gun. Next time i'll have to take some
before and after pics for the doubting thomases.
SAFETY NOTE:- ensure good ventilation, use safety goggles,and beware of very
slight risk of combustion.
 
B

Baron

Jan 1, 1970
0
hr(bob) [email protected] said:
In response to someone who emailed me a couple of
months back saying he did not believe it
was possible to desolder , with a hot-air gun,
ICs soldered in plated through hole pcb boards,
without causing mayhem.
And anyone else who could use the technique.
The following is some before and after pics
of such a board this week, with thin tracks, through pin tracks and
a nearby via for good
measure.http://home.graffiti.net/diverse:gr...graffiti.net/diverse:graffiti.net/de_sol2.jpg
Masked off with the thick form of plummer's PTFE tape to protect
adjascent components from desoldering/ flicking
off.http://home.graffiti.net/diverse:gr...graffiti.net/diverse:graffiti.net/de_sol4.jpg
After blasting with hot-air and before cleaning up the holes with a
needle-point probe and soldering iron. Usually the polyester of the
pcb does not discolour, for normal cheap IC soldering, but the
plated-through fixings mean more heat required than
usual.http://home.graffiti.net/diverse:gr...graffiti.net/diverse:graffiti.net/de_sol6.jpg
The converted circlip pliers extractor tool , with a close up of the
double joggled tips. Lines of bending are at B-B and the red lines.
Graph paper is mm squares.

The full text for the tip
De-soldering ICs
Use a hot-air paint-stripper,1400W,500 degree centigrade,with 2
level heat
control to prolong element life. Activity may appear fearsome but it
is no
worse than a flow-solder bath.Pre-heat for one minute then apply to
pcb,make extractor tool to pull ic from component side. Make an IC
extractor from an
old large pair,10 inch, of circlip pliers,the jaws need to open out
enough to clip around the ends of up to 64 pin ICs with enough force
to overcome the mechanical force of the situation where all the pins
are angled relative to the PCB holes.Forge around both of the
original circlip pins,one joggle at right angle to clear the heigth
of the ICs and a slight
inwards joggle to make purchase on the underside of the IC,grinding a
wedge angle to the
points helps particularly where there is no clearance between IC and
pcb.
[ Because of these joggles this tool is also useful for depressing
[ the rear
grippers and releasing of that type chassis mount fuseholders and
switches when internally surrounded by other
components ] . For awkward positions lock the pliers to the IC by
wrapping a cable tie around the handles, tighten, slide down and
add a couple of notches to the tie and force back along the handles.
Use this technique for salvaging (working order) up to 64 pin ics (
when practised ),other
components, sm and even repair (tracks are not dislodged).For repair
work beware of spatter of molten solder causing solder bridges on
adjascent compoents because if you are doing the job properly,ie not
dislodging pcb tracks the IC must be pulled out with
some force and the board tends to flex so possibility of flicking
solder. Mask off surrounding areas with wide aluminium tape or thick
plummer's PTFE tape around both sides of board to avoid unsoldering
and flicking off nearby minor components and trap any that do.
The secret is to be as quick as possible,idealy the body of the
extracted ic will be just about handleable rather than too hot to
touch.Try practising on a board with close packed TTL chips or
similar and aim for an extraction rate of something like one every 2
seconds.Between boards keep the hot air gun running on low power
setting (not switching off).Don't rest the gun against the board
when heating as vibration seems to affect the element life also don't
allow the board to
flex back onto the gun for the same reason.Hold the gun so airflow is
angled to the board as solder spat directly into the nozzle can kill
the element. About the only components that cannot be removed with
this technique are parts moulded in soft plastic,e.g. crystal
sockets,rf coils with plastic former
(IF coils usually OK) some DIP switches. Even these are desolderable
intact if the body of the component is previously cooled with a blast
of aerosol freezer spray.
You definitely need a tool to pull the IC off the board as soon as
the solder is non-solid/breaking up ie before even fully melted quite
possibly. An old pair of long nose pliers with the ends ground down
so the remnant tips can be bent inwards to grab the ends of the IC
would probably be sufficient to show the method works.
Also definitely practise on an old/scrap board first as it needs that
confidence because otherwise pointing a glowing hot element and 300
degree C or more blast of hot air at a pcb is not a natural thing to
do. SAFETY NOTE:- ensure good ventilation, use safety goggles because
trapped water etc in the capaillary structure of glass fibre
reinforced PCB can super-heat to steam and jet out molten solder,also
it is possible to overlook
small electrolytic capacitors on the solder side of the board which
of coarse
explode with the direct heat of the hot air gun and beware of very
slight risk of combustion of adjascent flammable parts especially
where components have extra (un-noticed) mechanical bonding leading
to extended duration of heating activity.

Norm:

Thanx for the step by step information. Your posts are always worth-
while. Is adjascent the UK spelling of adjacent?? <G> ---------- this is correct.
H. R. (Bob) Hofmann
 
C

Clint Sharp

Jan 1, 1970
0
Mark D. said:
Just had to tell someone - I got a bright idea to remove a flyback
transformer using a paint stripper gun.

AMAZING. Had that FBT out of there in about 40 seconds - no need to fight
the thing clearing eyelets, etc.
Weller instant heat soldering gun, length of heavy gauge copper wire in
place of the normal tip bent into the outline of the pins, works
wonderfully. As for the heat gun desoldering ICs, I recommend a Steinel
variable heat gun, used to work on lots of expensive IBM motherboards
using one of these to pre-heat or desolder chips.
 
B

Baron

Jan 1, 1970
0
N said:
If you mean the likes of
http://www.maplin.co.uk/images/300/fd54j.jpg
then no - not man enough even for cheapo boards, certainly not for
plated-through extraction.

I agree. That is why I made mine using 10mm wide x .75mm alloy strip.
The other advantage is that as you squeeze the angle on the bent ends
lifts the ic off the board. Just like the modified circlip pliers. It
can get a little difficult if the dil's are a bit close together
though.
 
L

Leonard Caillouet

Jan 1, 1970
0
Mark D. Zacharias said:
Just had to tell someone - I got a bright idea to remove a flyback
transformer using a paint stripper gun.

AMAZING. Had that FBT out of there in about 40 seconds - no need to fight
the thing clearing eyelets, etc.

Done it twice now. Works great. Surely someone here has done this, But I
work with a couple really experienced TV techs and they hadn't thought of
it before...

I would recommend watching out for any nearby SMD's, though...


Mark Z.

Duh! Boy do I feel stupid. We use hot air for ICs, why not a flyback.
Thinking about all that cleaning of desoldering tools and wick over the
years while that heat gun was sitting idle makes me sick for the time and
money wasted. Big heavy traces and lots of solder to catch the heat. I
read your post and had to go try it and it works great.

Thanks Mark.

Leonard
 
A

Andy Cuffe

Jan 1, 1970
0
explode with the direct heat of the hot air gun and beware of very
slight risk of combustion of adjascent flammable parts especially where
components have extra (un-noticed) mechanical bonding leading to extended
duration of heating activity.

I bought a temperature regulated hot air gun. It cost about 3 times
what a regular hot air gun cost, but it was worth the extra. It's
continuously adjustable from 120-800 degrees F. While it's not as
good as a professional hot air soldering station, it works well for
removing components without burning, or damaging the board. It easily
removes regular SMD ICs without damaging them, or bending the pins.
I've even managed to remove and re-use a few small BGA chips.
Andy Cuffe

[email protected]
 
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