Semi OT: Removal of QFP ICs

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Does anyone here have suggestions for good ways to remove flat pack ICs
on prototype boards such as a 64 pin TQFP or larger?

The tools I have available, have a (smaller) hot air tool that is fine
for chip package compoents but can't output enough to do a larger
device like an IC larger than an SOIC-16.  I have used the Dremel with
diamond wheel cutter method sucessfully but it does carry a real risk
of ripping pads off the board no matter how carefull you are.  These
are prototype boards in a development project so their "value" is high
in that they would be expensive and time consuming to replace.

I know that there are tools available that will apply the hot air and
then apply vacuum pressure to remove the device reliably but I don't
have access to that level of equipment.


Re: Semi OT: Removal of QFP ICs
http://www.avrfreaks.net/index.php?module=dpDocs&func=index&cid=4
Read the de - soldering section



Re: Semi OT: Removal of QFP ICs

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If you don't care about keeping the part nice:

Take a very thin wire, and feed it between the package and a row of
pins. Tie one end of the wire to a hole in the board, or a sturdy
component. Hold the other end of the wire with one hand, and a
soldering iron with the other. Heat the pins one by one (or a small
group at the same time, if the pins are close together), while trying
to raise the pins with the wire. If you keep the wire at a 45-90 degree
angle, and carefully pull on it, it will bend the pins up one by one.

For the last row of pins, you can pull up the package, and bend it back
and forth a few times to break the pins.


Re: Semi OT: Removal of QFP ICs
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If the TQFP may be destroyed, use a small cutting plier where you have the
tips filed down at the outside in order to make the cutter narrow enough to
fit between the IC pins. Cut the pins and remove the remaining pieces with
solder wick.

Another method that saves the chip (apart from bent legs) is to shove a thin
copper wire underneath one side of pins, start heating the pins at the end
where you pull on the wire (fix the other side somehow). The pins will bend
up, the wire will slide between the pin and pad, clearing the solder.

Meindert



Re: Semi OT: Removal of QFP ICs
On 23 Feb, in article

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For small quantities of rework I would look at

        http://www.chipquik.com /

Very useful and very clean way of removing  devices even QFP 144
as I have found. Available from various catalogues or direct.

Good flux pens I find help as well for liberal coatings of flux in removal
and replacement device.

For larger volumes more than one a week I would seriously consider
the expense of JBC hot air system for QFP, trouble is quite a bit more
pricey.

        http://www.jbctools.com /

That is a few top get you started.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Semi OT: Removal of QFP ICs


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I've been using the ChipQuik stuff for a while now, and it works great.

-Hershel

Re: Semi OT: Removal of QFP ICs

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If you want to keep both the parts and pcb, you need to reverse reflow
it.  First of all, dry out the board completely (40C for 192 hours or
120C for 24 hours or something in between) if you have any plastic
parts.  Bake upside down at around 250C for a few seconds and tap on it
while it's hot.  We had to redo some boards with BGA and TQFP that way.


Re: Semi OT: Removal of QFP ICs

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The most important thing is patience.

Turn the hot air heat and flow all the way up.
Give the tool a couple of minutes to come up
to temp then work it around 2 perpendicular
sides of the chip while *gently* teasing and
lifting the corner of the chip with a dental
tool.

Do not apply enough pressure to delaminate a
pad.  When it lifts up a little, move over
to another corner. Work your way around until
the chip lifts free.

I've done about 100 chips this way without
damaging the boards.  I generally throw the
chip away after removing it, but in a couple
cases where I've had to reuse it, it worked
fine.

Again, patience.  The process usually takes
at least 5 minutes on a 100 pin TQFT.


Re: Semi OT: Removal of QFP ICs

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This might not work in all cases, and be careful about solder splatters.
Wear eye protection and so on (stuff could go flying): We used a thin
stainless steel blade and gradually shoved it under the pins that were
in one row as the heat softened up the solder, until the blade was under
all of them. Solder didn't stick to this blade as long as you kept
gently moving it. Then pulled it back out and repeated that for all
sides until the chip came off. Be careful when it does. If the thin
blade had to bend across a nearby decoupling cap it might go "kaploink"
and send the chip flying.

In my case it was one of those little gauge things from the days when
cars needed their valves adjusted regularly. These gauges have something
like 20 metal tongues you can slide out, some are really thin. But it
has to be the 'upscale' version with stainless blades.

Regards, Joerg

http://www.analogconsultants.com

Re: Semi OT: Removal of QFP ICs


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the gauge thingy is called a "feeler gauge". I used to tune my Dad's '65 VW
bug with one.

Bob



Re: Semi OT: Removal of QFP ICs
Hello Bob,

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Thanks. I used it on my Citroen 2CV. In contrast to the VW Beetle this
was much more comfy:

Only two cylinders. Take off both front fenders, takes 2 minutes tops.
Then let some air out of the front tires, pfffsssst, makes for a nice
cushy seat. Take cap off and adjust. Meantime you could park a nice
bottle of booze on the air filter cap, reachable from both "seats". It
had a circular indentation that, for some reason, was a snug fit for the
bottom of a whine bottle. I bet that was another one of Andre Citroen's
famous functional requirement specs :-)

Regards, Joerg

http://www.analogconsultants.com

Re: Semi OT: Removal of QFP ICs
ChipQuik works very well:

http://www.chipquik.com /

Leon


Re: Semi OT: Removal of QFP ICs
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That it does. They'll even send a free sample.

(a satisfied user)



Re: Semi OT: Removal of QFP ICs

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I can recommend a dentists toolset. Don't ask me for a
name, it is just one of these bent thin wires from some
incredibly strong material. Some sort of stainless steel.
I start in a corner and heat the pin while trying to push
the tool underneath. When the tin becomes soft it slips
to the next.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Re: Semi OT: Removal of QFP ICs
I want to thank everybody for their responses.

 It looks like ChipQuik is very popular.  I sent them an email asking
for a free sample.  I look forward to trying it out, the next time I
need to remove an IC.

The dental tool method would probably work well too as long as I work
carefully fstarting in one corner.  Now, if I can only remember where I
left the pick that the dentist gave me that one time I got my teeth
cleaned....


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