Removing a TSSOP chip

I have to remove a TSSOP chip in an Apogee DAC (see the black market for details...).

But how do I do that without damaging the fragile 3- or 4-layer board in the process?

And advice on how to solder wires to the pads afterwards are also accepted :green:

Best regards,

Mikkel C. Simonsen

There are some specialized desoldering stations for that sort of thing but they run into a lot of money.

But short of that, there are some specialized iron tips that fit over the package(s) on both sides so you can lift the whole thing off, unless it is glued down as well.

If glued, then a lead-by-lead heating and gentle pry upwards with a really fine needle-pointed awl can do it. Very tedious, and impatience results in prying the pads up.

If there is excess solder to begin with, some fine solderwick applied to remove the initial excess may make the second operation easier.

Hakko and Weller make hot air units for SMD/SMT rework. We use them all the time at my work. The technique we use is to apply plenty of flux (low residue or water soluble, depending on the PCB assembly) and then gently heat up the area from about 6 inches away at 800 deg. F. Then slowly working closer until you are about 5 mm away. Once the solder is in a liquid state we pull it off the board using tweezers. Sometimes a very slight nudge is used to make sure the IC is free, and not to pull any pads. We replace pulled pads all the time but it can take 20 min. for each pad using a microscope.

Solder wick can be used but I don't trust it.

Vetsen

P.S. Hey MCS, I thought you were the king of SMT. :green:

I just fill the space between the leads with solder until they are all bridged. You have to work fast so the added solder keeps things cool. Trade off heating both sides until you get them molten at the same time, then slide the whole mess off onto the table and clean up the mess.

Exciting, isn't it!



Well, no.

Something like this?

http://www.dansworkshop.com/SMT%20Hot%20Air%20Pencil.shtml

Some time ago I found another description of how to diy a hot-air soldering thingy out of available parts - using an aquarium pump, a desoldering head and some steel-wool for heating the air. I can't find it right now, though..

Jakob E.

what CJ said...

or, feeding thru a thin wire under the pins/IC then heat the pin with the solder iron and pull the wire to raise it of the pad...a pin at a time...

[quote author="Vetsen"]P.S. Hey MCS, I thought you were the king of SMT. :green:[/quote]
Yes, adding the parts is no problem - but removing them is :grin:

Best regards,

Mikkel C. Simonsen

http://www.usbmicro.com/odn/documents/46.html

Just a thought


Wouldnt it be easier to just cut off all the legs as near as possible at the chip and let them soldered where thay are. It might be also easyer to solder the new wires to the legs too then to the tiny traces on the board. Of course only if we dont need that Chip for anything else.

btw. nice work Mikkel :guinness: :guinness: :guinness:
I cant wait to hear my appogees in action.

Best Regards: Jasmin

[quote author="Housemeister"]Wouldnt it be easier to just cut off all the legs as near as possible at the chip[/quote]
Have you seen how close together those pins are? Even getting a tool between the pins for cutting would be difficult...

Of course only if we dont need that Chip for anything else.

Click to expand...

The chip is useful, but I think saving the board is a bit more important :grin:

Best regards,

Mikkel C. Simonsen

I pretty much always cut the chip off of the board - I don't have the nice tool. But be careful so you don't lift the pads. Sometimes if you're rough with the cutting, you can lift pads and that's not fun.

I've done it a few times, my boost gauge boards use three TSSOP chips apiece, and I've had to swap them out more than I'd like.

You can do it by removing all solder with wick, then laying your iron across all the pins on one side, and gently lifting with tweezers, then do the other side. It's possible to lift pads this way, you're much better off with hot air.

In the past I've generally tried the cutting technique but get frustrated when my cutters won't fit between the legs. I mean really frustrated. So I usually end up taking the clippers to all 4 pins at once. Sometimes this works OK, sometimes it ends up ruining half the pads.
It's easy once you have one side up though because you can just rock the whole chip back and forth until the other pins snap off clean.

The lifting one pin at a time thing never worked for me either. Couldn't find anything small enough to get under the darn things. And as soon as I stick a soldering iron on there to get things heated up, it usually ends up bridging all the pads into an unrepairable mess. Seriously.

So, take my advice so you don't have to be the newbie ruining all your fancy equipment, like I do.... get someone who knows what they're doing. Either that or figure out a way that actually works.

A small update.

I have just found out I don't have to remove the chip. Disconnecting one pin should be enough. That pin is of course not at one of the corners... I also can't just cut it off - it has to be grounded afterwards.

So I have to lift this pin without breaking it off. Any ideas? I guess daArry's method may work, if I can get anything under the pin.

Another option would be to "disconnect" the pad. The pin is connected to the outside world through a via, so perhaps drilling through that via with a slightly larger bit would work? Or cutting the less than 0.5mm long track connecting the pad and the via - I will need a scalpel and a magnifier for that option at least...

Best regards,

Mikkel C. Simonsen

A scalpel blade under the pin, and solder iron on it?

We have an 8 pin surface mount that needs pin 3 lifted and shorted to pin 2. (Thank you engineers for letting me cover yo ass while you drive your Mustang convertible home :twisted: )

Solder wick it a bunch of times then pop it loose with an exacto.

The operation went well, but the patient died...

I managed to get the pin pushed away from the solder pad with a knife blade. But when I tried to bend the pin upwards, it just cracked off...

So I had to change strategy, and remove the chip completely. Using the soldering iron and the knife, I got all the pins on the same side of the chip snapped off. After that, it was easy to remove the chip.

This left a terrible mess on the board of course, but after cleaning it with some solder wick, it looked OK (no shorts). The only pads that had fallen off, were the NC ones. One aditional pad did come off though when I cleaned the board with alcohol and a cotton swab (the pad of the pin that should have been bent).

I need to perform the operation on one more chip, so perhaps the pin-bend procedure will work better then...

Best regards,

Mikkel C. Simonsen

ok it took me a while to find this thread but I am here to save the day.

EDIT: nevermind i did read the last post!! The rest is still informative though...

I solder these crazy chips and many other crazy ICs daily and know some hair raising but useful ways of getting them off. Trust me, it's not that hard really it just looks hard. I find it harder to unsolder through hole stuff than SMD.

First, do you know if the IC was glued to the PCB before soldering? If it is, you will likely kill this PCB trying to get it off and you should not try it.

second, If it's not glued to the pcb, then the next step depends on what you would like to do. I bought the most useful tool i have ever bought for getting these things off. Yep, that's a regular METCAL soldering iron and various IC tips. EBAY. Used. 50$usd. I have about 50 tips that i've bought over the years and can take just about anything off of a board with them. It's a good investment if you plan on doing more of these. apply solder to the proper tip, place tip on IC, wait a few seconds until you see the solder on the pins melt and then lift the IC right off the board. OR you can do it the less easy way. solder. lots of it. Get a razor blade too.

1. apply huge amounts of solder to all rows of pins making sure all the pins are connected by the solder bridges.

2. now gently wipe the tip of the iron back and forth along two perpendicular rows of pins until the solder is liquid and will stay so for a few seconds.

3. while you are wiping and the solder is hot, take the razor blade and place the tip under the corner of the IC and gently start to lever it up. don't try to hard or you'll pull pads up. do it just enough to move it.

4. allow the solder to cool while holding the IC up.

5. move to another corner and do steps 1 to 4 again.

6. once you've moved all the way around the IC and the pins are now sitting neatly on top of a mound of solder there are two things you can do. either get some solder wick and suck all the solder under the pins and the IC will come off, or move quickly around the IC with the solder iron and flip the IC off the board with your razor as the solder is liquid.

Yes it sounds terrible but once you've tried it(on a test board of course..) it's actually only about a 30 second job and as long as all the solder is molten, you won't pull the pads up which is by far the most likely thing you'll do.

[quote author="Svart"]First, do you know if the IC was glued to the PCB before soldering? If it is, you will likely kill this PCB trying to get it off and you should not try it.[/quote]
It isn't (I know now).

3. while you are wiping and the solder is hot, take the razor blade and place the tip under the corner of the IC and gently start to lever it up. don't try to hard or you'll pull pads up. do it just enough to move it.

Click to expand...

I don't know if there's space for the blade - the chip is surrounded by other parts on all sides...

Best regards,

Mikkel C. Simonsen

you might try gluing something to the top of the IC with heat resistant glue so that you can pull up on it as you run solder on all the legs.. but really the best way is to use a tool designed for it. :wink:

good luck!