Salvage Components from PCBs

[Brad]

Hi,

I have a bunch of circuit boards (no SMDs) that I would love
to find an easy way to remove the parts without unsoldering each
one at a time. I know there is a chemical (not cheap), when
applied, lowers the melting point of solder. Maybe I could use
a hot air gun? Do you know a good method?

Thanks in advance, Brad

Before you type your password, credit card number, etc.,
be sure there is no active key logger (spyware) in your PC.

 

[Matt J. McCullar]

One method I've heard of -- but not tried myself -- involves using a
blowtorch. You heat up the solder side of the board, liquifying all of the
solder joints at once, and then knocking the board over an empty metal
garbage can to catch everything as it falls off.

This may or may not work well. It depends on the manufacturer of the
circuit board. Sometimes the parts legs are bent over or crimped after
they've been inserted into the board, so they won't pop loose this way.

 

[Don Young]

If you have one, a heat gun works great. Otherwise a torch or even a
hotplate can do it. It just takes a little practice to get the heat right
and you may ruin some parts. If the leads are crimped you can melt the
solder and remove it by brushing, banging the board against something, or
even an air blast (which can be pretty dangerous). A forked tool is best for
uncrimping the leads.
Don Young

 

[Soren Kuula]

Hi,

I have a bunch of circuit boards (no SMDs) that I would love
to find an easy way to remove the parts without unsoldering each
one at a time. I know there is a chemical (not cheap), when
applied, lowers the melting point of solder. Maybe I could use
a hot air gun? Do you know a good method?

Hot air gun works great, but the fumes are not healthy --> go outdoors.

I used to do that, only to realize that the component you are looking
for is much easier to find while still on the board, also because it is
quite easy to guess what kind of device the old boards used to sit in,
and thus on which boards you should look for a certain kind of IC,
transistor, or whatever....

Soren

 

[N Cook]

Hi,

I have a bunch of circuit boards (no SMDs) that I would love
to find an easy way to remove the parts without unsoldering each
one at a time. I know there is a chemical (not cheap), when
applied, lowers the melting point of solder. Maybe I could use
a hot air gun? Do you know a good method?

Thanks in advance, Brad

Before you type your password, credit card number, etc.,
be sure there is no active key logger (spyware) in your PC.

I've used this technique for salvaging and repair for 10 years.
Although I do own a proper vacuum assist desolder station I
prefer to use a hot-air gun - it causes less damage to tracks etc

De-soldering ICs etc
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.
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.
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.

SAFETY NOTE:- ensure good ventilation, use safety goggles because trapped
water etc in the capaillary structure of glass fibre reinfiorced 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.

other tips on
http://homepages.tcp.co.uk/~diverse

 

[Art]

Kind'a wonder what antistatic procedures are being implemented to actually
produce opera devices once these procedures are completed?? IMHO I agree
with leaving the components physically on the pcb until required for use,
then use appropriate antistatic removal techniques to assure a component
that may actually function in it's new enverironment. Otherwise you may have
a few resistors and caps that end up in a pile to be sorted later, static
sensitive devices would best be left on the boards until required for use.