Favorite SMD chip removal method

I walk over to the kitchen, give my wife a kiss, steal some chocolate out of the fridge when she isn't looking, then take a piece of thick aluminum foil. This gets draped around the board and then I cut the chip free, using an Exacto knife. Now I heat things with a Cooper heat gun. I let a Rouladen-hook (like a kabob spike but 3x smaller) stick underneath, at a very flat angle. This avoids me having to tug and risk ripping pads off. When the hook starts to sag I know it's 2-3 more seconds and I'll be able to just scoot the chip off onto the aluminum.

If in a rush I sometimes use a big old 150W iron. Melt some solder onto the pins and slide that along. Then I take my thinnest valve adjuster blade (don't need those anymore with modern cars) and slide it along with it, goes between pins and pads (careful, never force it or a pad will rip off).

I never use any large BGAs. Too many reliability issues. A non-flexing BGA on a flexing PCB is a bump failure waiting to happen.

--
Regards, Joerg

http://www.analogconsultants.com/

OK, I'm slow -- by "cut the chip free" you mean you're cutting a hole in the aluminum foil, so you're only heating up the chip? When I first read that I thought you meant you were cutting off the chip at the legs, then cleaning up the legs later -- but that doesn't make sense with the rest of what you said.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Yes, just the foil, so that you get enough clearance around the pins yet neighboring chips and SMT parts remain covered. Use thick foil, the good stuff, not the thin stuff from the Dollar store :-)

--
Regards, Joerg

http://www.analogconsultants.com/

If the chip is scrap, cutting it loose and removing the pins later is probably easiest. Paying some attention to how much time you are spending and whether it pays to invest $150 in a chinese Haako knockoff or $900? in an actual Haako rework is also worth asking yourself. I used the proceeds of SMD work with my WTCPN to invest in a knock-off - if work ever develops to that point, I'll use the proceeds from using the WTCPN and the knock off to buy a real Haako. Fortunately most of the work was not rework.

For smallish chips using a long cone point on the WTCPN and loading up on regular solder so you can get a whole side melted can work, at least for two-sided chips where getting a whole side free means you can pull that side up. If you have a larger wide iron/tip you might be able to pull that off with bigger chips - adding solder is an important part of the process, but quad-packs will be a pain since you'd really have to get 3 sides free to make progress.

If you need to save the chip and can spare the time, adding a bit of solder to one pad, heating, pulling the leg up with a tweezer or probe, repeat works on gull-wings. More commonly of use in the "E.C.O. - wire around the mistakes before you get the next board revision" phase just to get a few legs up to connect wires to.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

If not saving the chip, cut all leads at the chip body and desolder each lead individually at the PCB pad. THAT is the least invasive to the PCB assy.

If you require keeping the chip and it is fine pitch, then a full reflow is required (with real solder). The second requirement being that you know what you are doing, because attempting to pull a chip that is not fully reflowed can cause a pad to be lifted.

You can pre-wick much of the solder, and then there would be less clean up after the removal.

The key is not to introduce a lot of heat into the individual pads on the PCB. That heat is what causes them to de-laminate either the pad or even layers of the PCB glass itself.

Full reflow is the best, and a good, proper pre-heat ramp up of the entire board before the chip area gets heated, will keep the assembly stable. No pre-heat and you cause temp extremes in the PCB as well as components themselves. Using a pre-heat is not going to harm the rest of the components. To the contrary.

For big SO packages, usually a fairly fat conical tip and a piece of tungsten wire--you loop it between the pins and the package, and apply tension while you touch each pin with the iron. Comes off just like a zipper.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics Electro-optics Photonics Analog Electronics

55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

For BGAs: Suspend the board over the bench with the chip in question on top. Strip some 30 GA WW wire and push the end under the middle of the chip. Tie off the end to form a loop around the chip.

Place one heat gun under the chip running on low and another down from the top running on high. Dab some thin gauge solder on to pads at intervals to judge temperature. When the solder flows on to a pad, gently lift your wire loop. If you feel resistance, continue heating the chip. Within seconds, you will be able to lift BGA off the board, with minimum cleanup necessary. Be careful! Many components will just be hanging by virtue of solder surface tension. This is not the time to jar the board.

--Winston

A 2-speed heat gun aka paint stripper. I pre-heat the board gently at the low setting and then use the high setting for a few seconds to get the solder to melt and remove the chip. It works like a charm and both the board and the chip survive!

For small SOIC and TSSOP packages I usually don't bother with the heat gun. I apply much solder on one side and lift the chip. Then use solder wick to get rid of the solder which leaves me with one side of the chip clear from the board. Then I apply much solder on the other side.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

(...)

Yes.

Preheating is necessary for BGAs on multilayer boards. Get those inner plane layers hot and you can lift anything off the top of the board.

--Winston

For one-off repairs on leaded chips, I have a couple ways. If the chip is definitely bad, and no need for post-mortem analysis, one trick is to use a modified X-acto knife to scribe the leads on each row several times. One way is to use the knive backwards, it scrapes a little lead off each time you scrape down the row, and soon the leads are separated from the body. Use the knife to complete the separation, and then use a soldering iron to "sweep" away the leads.

Another method, slower, is to use an X-acto knife to bend up each lead as you heat it until the solder pulls away completely. I usually use standard solder wick first to remove as much solder as possible. I usually dip the solder wick in GC liquid flux first, as the stock solder-wick doesn't have enough flux to work properly.

If I have to pull a bunch of chips, I make a desoldering tool from a block of copper bar. You can buy tools like this for most common chip outlines from Pace and similar solder tool suppliers. I often add some solder to the chip first, either bridging all the leads together with standard iron or applying a bunch of solder to the desoldering tool before use. If you don't have enough solder to completely wet all the leads, you can rip pads off the board. When I have this setup working optimally, I can usually desolder a 100 - 128 pin quad flat pack in under 10 seconds.

Jon

Hi,

Sometimes I short out all the leads with solder, say for a 44-QFP package, so there are 4 big blobs of solder one on each side of the chip with a much larger heat capacity, so that gives enough time to heat up all 4 sides them lift the chip off before the solder solidifies.

cheers, Jamie

I think that by far the best way to get these ICs off the board is by hot air. Especially if you have a tip that is in shape of the IC you are trying to remove. If not, even the small tips on these units work fine.... ya just gotta move it around the chip edge.

Chinese hot air units can be had for real cheap, some of which even have a soldering iron on them.

To put the new chip back on, I juse use roll solder (with GROUNDED iron), and then LARGE solder wick to help remove my shorts.

boB

snipped utter stupidity.

What happened is that you became even more immature, and more retarded than John is. You pathetic, cringing little milksop.

You need a butane gas torch to get those off

--
Dirk

http://www.neopax.com/technomage/ - My new book - Magick and Technology

I've got one of these on my bench. Very happy with it.

The main question is: do you shove enough electrons in to cause damage? Chips are designed to withstand a certain amount of ESD without degrading performance.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

If you put a line of flux from a needle bottle over the row of pads, you can just tin the iron and run it down the line in a few seconds per side--no bridges, no worries. Slick as can be.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics Electro-optics Photonics Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

I use ChipQuik:

Leon

For under $400, you can get cheap Chinese hot air rework equipment from

. QK853 hot air plate (need to replace the platform with a larger area plate and raise it little bit) for $145. QK857D hot air rework station for $185. It's cheaply made, but does work for small amounts of work. We use both units which have been used almost daily for the past 2 years.

With this combo, a little bit of flux, and some unorthodox techniques; you can remove/attach most SMT parts.