Semi OT: Removal of QFP ICs

Read the de - soldering section

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.

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

For small quantities of rework I would look at

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.

That is a few top get you started.

--
Paul Carpenter          | paul@pcserviceselectronics.co.uk
    PC Services
              GNU H8 & mailing list info
             For those web sites you hate

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.

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.

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

ChipQuik works very well:

Leon

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

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

-Hershel

That it does. They'll even send a free sample.

(a satisfied user)

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

Bob

Hello Bob,

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

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....