EEVblog #437 - Removing SMD Parts with ChipQuik

How to remove surface mount SMD QFP packages from a PCB using ChipQuik low melting point alloy solder.

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[Kriakoziabr]

Greetings from Russia. We have a popular method: Take Wood's metal (~ 42 % lead, ~ 40 % bismuth, ~ 9 % tin, ~ 9 % cadmium. Melting point is 68°C) or Rose's metal (~32 % lead, ~ 50 % bismuth, ~ 18 % tin by weight. Melting point is 95°C) Rose is more popular, since it does not contain cadmium and is less toxic. Apply at 400-450 degrees on lead-free alloy So you get an alloy with a melting point of about 110 degrees. Sometimes it is even inappropriate to heat the part in addition, it falls out by itself. After, MANDATORY remove the resulting alloy from the place of soldering, it is brittle and fusible. Thus it is possible e.g. SO8 desoldering chip without hot air. Chip Quik SMD Removal Kit for poor :-)

[hellterminator]

18:34 “Be careful if you've got nearby passives of course.”
18:40 Desolders C8.
:D

[jackmclane]

The composition: 49% Bismuth, 18% Lead, 12% Tin, 21% Indium.
This makes a eutectic alloy that melts at 58°C.

[DarthMaul]

C8 is the most famous component on board

[nhojyelbom]

btw, you can re use the chipquik balls! just use a brush dipped in flux, move into 1 big ball to re-use (with flux of course)

[rubber]

Not bad at all, but the cost is astronomical!

[marcusdudley]

How can you patent an alloy? At what point does another alloy violate the patent? If it has like 5% iron, 6% antimony and 89% other stuff for example and you manufacture an alloy with 5.2% iron, 5.8% antimony and 89% other stuff, would that be considered a violation? At what point does the proportion of constituent metals get diverse enough to render it "different" from a patented alloy, and who defines this limit?

[cashman]

Its the leftover stuff from the T-1000. So it must be expensive.

[frankt.]

12:46 Made in Mexico flips the chip => TAIWAN

[chickenby]

the trick is to melt the original solder so the two metals mix, and then after you can heat it up much quicker, and this combined with a hot air gun is amazing. there are tons of other "low melt" solder options, all at much lower price points

[SaderStel]

This is heaven for use with a hot air iron, just lower the temp, no stress for the chip and little components around will not get unsolder. Since it's such a low temp, maybe you can even use a fiber brush to brush away the solder that is left on tracks.

[NunYa]

This stuff is amazing! I use it mainly to remove ribbon cables that are hot bar soldered directly to the board. Have not lifted a pad since!

[chaddkersey]

There seems to be some confusion among the commenters here about what a patent is. There is no secret. The whole point of patents is to be able to disclose information that you would otherwise keep as a trade secret. US patent number 5326016 A. "18% tin, 28% lead, 11% cadmium and 43% bismuth"

[mariusmul]

Its excellent in any workshop scenario, it removes not only chips but those nasty TO3's, transformers, coils or whatever do not desolder easily from thick pcb's.Very handy.You can use much less after some practice, retrievable bits can be used again and its all at low temperatures.GREAT.

[SomeMoreVideos]

It says tin, lead, bismuth, *indium* on the datasheet I found on Farnell. I don't imagine cadmium would be legal for sale in many parts of the world. Presumably it's the newer version of it if the old one did contain cadmium. Percentages are: Sn12, Pb18, Bi49, In21.

[mike]

I can vouch that this stuff works great. I had to desolder a 128 pin ultra fine pitch QFP from a donor board, clean it up, and reuse the thing on another board. I did it all without any damage to the pads or chip itself. And it was my first time using the stuff. So in the right hands, this stuff is worth every penny.

[greatstonedragon]

ChipQuik can also be useful for thru-hole repairs on multi-layer boards. With internal power and ground planes (and moron cad jockeys who neglect thermal reliefs), it can be next to impossible to remove snap-in caps and jack connectors without pulling the thru hole out with the component, further damaging an otherwise repairable board. Sometimes you just can't get heat into the solder joint faster than the power plane takes it away without burning the PCB, preheating or no. After removing excess solder with solder wick, a bit of ChipQuik and gentle wiggling makes it possible to pull the component out.

Another use is getting all the lead-free solder out of smaller multilayer thru-holes. Occasionally you run into a thru-hole where the solder next to the power layer just refuses to melt. Apply a bit of ChipQuik to the pad, heat up a resistor lead with your iron, and insert it into the blob of solder. The lead pushes through the hole, and mixes the higer temp lead free solder with the alloy. It's then easy to melt all the way through the hole, and remove all the solder.

ChipQuik is a great thing to have in an Altoids tin in your toolbox. After a bit of practice, you'd be surprised how long it lasts. And if you clean it off well with solder wick, any remaining residue tinned on the pads won't significantly change the composition of the new solder joint enough to cause a problem.

[sciencetestsubject]

according to the MSDS on digikey the proportions are slightly different, and the Cadmium is replaced by Indium.

[CodydeGraaf]

from an Amazon page (B+D enterprises): The composition is (Tin 12%, Lead 18%, Bismuth 49%, Indium 21%). The lead free ChipQuik version is the SMD1NL.

[tubastuff]

I've done the same by purchasing a small ingot of CerroBend 158 (used as a filler when bending thinwall tubing), filing off some to get it to powder form. I then take the powder and pack it around the pins of the QFP and then, from the underside of the board, use a 150W PAR-38 incandescent spotlamp to heat the area. The board heats evenly, the alloy liquifies and the QFP slides right off. No iron involved. Using the PAR38 as a heat source and a toothbrush, the board and chip clean up nicely. CB (now CS) 158 costs about $25 for a one-pound ingot. If you have a friend who works in radiology, you can sometimes get the stuff from them as it's also used as Xray shielding for selective radiotherapy.