SMT de-soldering

How did you handle glued down component removal, particularly when there is a track running under the part ? In the early days of learning how to repair this stuff the section of track under the part often came away when the part was lifted.

You would have about as much grip as with a pair of not terribly well aligned, smooth jawed, needle nose pliers. Enough for a twisting moment that could loosen the glue but don't expect to pick the board off the deck if the part was really secure in place.

If you know ahead of time that there is glue under the parts, preheating the board might help to soften the adhesion.

Best solution, two soldering irons - essential for SMD work really. Alternatively you can put a big blob of solder over the part and heat it all up at once. Or heat one end and and then the other end alternatively until it eventually falls off. This can be a problem on bad quality FR4 boards as it might lift the pads.

Dave..

We never used that method in our products. Any glue was a drop on one side of a component, or in the case of a large chip like a 144 pin MPU, a drop on opposite corners. All our boards were built, in house and met NASA standards. Glue under components is supposed to be used on throwaway boards, only. The glue is also supposed to soften with heat, but some assembly houses used cheaper adhesives that weren't thermal release. Even with glue under consumer electronics I've repaired, a slight twisting of the hot ceramic body would generally break the bond.

Pah! Nonsense!

I've done it loads of times and never had a problem.

The best way is of course to use 2 irons, but many people do not have access to 2 soldering irons

I don't remember you working the test production line. How many circuit boards that cost over $8,000 (EIGHT THOUSAND US DOLLARS) to build have you worked on? How much work have you done for NASA or the ESA? I've done both, at Microdyne.

Of course you haven't. You're special. Now its time for your nap, recess is over.

Anyone that can't afford two ESD rated soldering irons shouldn't be messing with SMD components.

I suspected as much ! That slight twist seems to be needed most times. Its just a nuisance when the track underneath gets twisted off because the glue hasn't let go.

I have tried various techniques which is how I ended up with a notched soldering iron tip. Most of the time it doesn't matter if the component gets damaged or destroyed, its going to be replaced anyway. I hoped that someone had a tip to reduce or prevent damage to the tracks under a glued down part.

I agree with Michael most consumer electronics is not intended to be repaired and the glue used isn't intended to soften under heating.

I have found that some of the larger 1206 & 0805 parts, if they are not glued will conduct enough heat to melt the solder on both ends allowing them to be brushed off the pcb lands.

Nice blogs by the way. :-)

The only thing I ever saw with enough glue to do that was a cheap car radio. It was so poorly built that the fillets, and some components cracked from vibration but the broken crap was still glued to the board. It was first generation SMD, and reflowed with very low grade solder. In this case it looked like the glue helped cause the failures.

Yes, I've found that too, although the trick is not lifting the pad with too much heat. A second soldering iron is an investment you'll never regret!

Thanks! They are crude but hopefully effective. Getting a bit of a following now which is nice (and surprising). Still trying to convince the wife I need a better camera and mic for my "stupid blog thingy I'll loose interest in next week"!

Dave.

David L. Jones Inscribed thus:

I've half a dozen including a hot air one. :-) Trouble is every job seems to need the one you don't have !

Funny ! My missus says that to me when I want to spend money. :-)

OK, it's done. No problems. I used 2 irons as suggested. Thanks for the help. Bob

You're welcome, and you now have another new skill under your belt. :)

Hmmm, they would need a temperature about 4-5 degrees....

~ S? How can that be?

Best regards,

Daniel Mandic