how to remove lqfp package

That's pretty wild. How does it 'dissolve' solder? Got a link?

I use a Dremel tool with a cutting wheel to remove flat-pack ICs, then follow up with solder-wick to remove the severed pins from the pads without stressing the board too much. Seems to work pretty well. (Also very effective for removing old-fashioned DIPs.)

-- jm

------------------------------------------------------

Note: My E-mail address has been altered to avoid spam

------------------------------------------------------

We use this system, which is basically the same as ChipQuik:

At $75 it's pricy, but 16 feet is enough to desolder ~75 QFP-128 chips, salvaging just one board makes it payoff.

Using just a pre-heater at 150 C, this stuff mixes with the solder and lowers its melting point so it's liquid. The chip lifts off without even needing an iron.

This keeps the board and other components below recommended temps, and nearby components stay firmly soldered. It's actually gentle enough that the chips could be re-used, if only there was a way to clean off their leads.

Cheers, Richard

First apply a lot of flux to the pads and wick up as much solder as possible using a solder wick. Thread a length of fine steel or similar wire under the chip and behind the row pads. Tie one end of the wire to the board. Pull the other end tight at 45° angel to the pads. Apply soldering iron to the first pad where the wire is pressing behind the pad. The little remaining solder will melt and the wire will slip behind the next pad in line. With little practice you can unzip a chip and preserve both the chip and pads.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

I am having an argument (a friendly one) with co-workers about removing small 32, 48, and 100 lead LQFP packages from production circuit boards. I think they should use the hot air rework equipment we own, but they like to clip them off with cutters and then clean up the pads with a soldering iron. I think that method stresses the pads on the board when they cut. I believe they cut many leads at once. Any comments?

Thanks,

Jeff

Cutting the leads with very sharp cutters may work ok but the clean up with a soldering iron may be slightly toasting the PCB.

There is a material sold for removing such things with no damage at all. It looks like solder but has a vert low melting point. You just use your normal preheater and put this stuff on the joints. It melts and disolves the solder freeing the IC without even the slightest damage to the PCB.

--
--
kensmith@rahul.net   forging knowledge

This is one of those areas where everyone has their own favourite technique. ChipQuik is another technique that I often use:

Leon

I have a tool from a dentist with a fine tip that lets me lift a single pin of a 0.8mm to 0.5mm pin distance case. I wouldn't heat the whole board with hot air as some other components may overheat or be blown away. Clipping might lift the pads and damage the copper.

Rene

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

[...]

You can wipe the leads of a PLCC with paper to clean them. On a TQFP, it would be very tricky to do without bending them.

--
--
kensmith@rahul.net   forging knowledge

Time them. Clipping, then unsoldering pins, sounds very time-consuming, not to mention messy.

So I vote hot-air.

I've done DIPs with a solder sucker and wick, but it's also time-consuming, and I wouldn't want to try it on a package with leads on all 4 sides. Although, you could use some pointy thing - stick it between the package and the jog in the lead, and shove it in as you unsolder one lead at a time and lift them.

In any case, the old solder will have to be removed somehow.

HTH! Rich

I guess this must be bismuth. There's a eutectic alloy of tin, lead and bismuth in which the tin/lead ratio is nearly 60/40, which melts at around 94C - below the BP of water. Sounds like this solder is s.t like this, perhaps with more bismuth. Time for some US EE who's a shooter to try it with some bismuth shot, now sold as a replacement for lead shot?

removing

boards. I

like to

soldering iron.

believe

Hot-air wins. It's faster, and there's virtually no damage to the PCB or to the component being removed.

-a