23 replies to this topic

[Richard H.]

Bought a load of chips on EBay, the legs have a sort of oxide on them that won't let solder through. I've tried flux and tinning with the iron turned fully up, but it still won't stick. Scraping sort of works, but it bends the legs (surface mount)

Is there some easily available chemical (acid ?) I can use to get it off ?



Thanks

Edited by Richard H., Tue Dec 28, 2010 12:35 PM.

[save2600]

Maybe some CLR and a toothbrush? Doubt it though. Extremely fine sandpaper or a fiberglass brush works best. Lightly sand both sides of the legs until shiny again and yes, this can be done without bending or breaking the legs if you're careful.

Edited by save2600, Tue Dec 28, 2010 12:51 PM.

[Richard H.]

I was really hoping for a chemical method as I have about 400 of them to de-oxide

[batari]

Richard H., on Thu Dec 30, 2010 10:10 AM, said:

I was really hoping for a chemical method as I have about 400 of them to de-oxide

Have you tried acids of varying strength, as well as bases? I'd think one or the other would work.

[Video]

Chips are sealed in epoxy (or plastic? What is that black shit anyways/) Maybe you could drop them in a jewelry cleaner machine? They use chemicals and vibration to take corrosion off of jewelry, maybe it could take oxide off chips. If you don't mind ruining (or risking ruining) you could try this. If it works, or the caused failure rate is acceptable, I think this would be a good solution.

[batari]

Other suggestions are to use a reducing agent. I am not a chemist, but I think reducing agents remove oxidation. I looked some up and see that hydrogen peroxide can act as a reducing agent. I also see ascorbic acid on the list (which I believe is in vitamin C pills.)

I have had the same problem with oxidation but on some through hole pads on PCBs. Fortunately the oxide is just on one side so I can solder the chips to the top, but it would be nice to be able to clean them, so I may try a few things later.

[Rybags]

Maybe just try a white vinegar soak... I used to do it on coins.

About 8 hours would do the trick. Try one or two testbeds first.

[Richard H.]

Quote

Have you tried acids of varying strength, as well as bases?

The only thing I tried was jewellery cleaning fluid. The dip and strip stuff. It had no effect.

[5-11under]

I'm in the same boat, with a bunch of EPROMs. If anyone has any solutions, please reply.

I'm trying the hydrogen peroxide right now. It's only 6% solution, and the chips are pretty "dirty", so I've got my doubts.
If I had some CLR, I'd try that. I have no idea if it will work, but it'd be a simple solution if it works as well as the commercials.
Another thing I've thought of is to put the chips in a container partially filled with dry sand, and shake it up until the pins look clean. Of course the labeling and package and EPROM window, in my case, will also be sanded to some degree.

[Video]

A sand box could work, just tape over the windows/labels and you should be OK

[nathanallan]

Video, on Fri Dec 31, 2010 3:55 PM, said:

A sand box could work, just tape over the windows/labels and you should be OK

Right, sounds like how to get rust out of a gas tank, and seems like it would work here and you'd need very fine grit sand. LOL sand from Nazca should do it.

/edit To clarify, the white sand found at Nazca is finely ground glass. No idea how it got there, but you can definitely make your own for a project like this. Tools: piece of glass to be ground up, one heavy stone with a flat surface and one flat surface, best if it is stone, too. Stone Age electronics

Edited by nathanallan, Fri Dec 31, 2010 4:04 PM.

[Dave Neuman]

This might work

[A.J. Franzman]

batari, on Thu Dec 30, 2010 6:35 PM, said:

I looked some up and see that hydrogen peroxide can act as a reducing agent.

5-11under, on Fri Dec 31, 2010 2:48 PM, said:

I'm trying the hydrogen peroxide right now. It's only 6% solution, and the chips are pretty "dirty", so I've got my doubts.
If I had some CLR, I'd try that. I have no idea if it will work, but it'd be a simple solution if it works as well as the commercials.

You Fail Chemistry Forever. Hydrogen peroxide is an oxidizer, which is the opposite of a reducing agent. If you want to clean an oxide off a metal, you don't use an oxidizer to do it! Hydrogen peroxide, bleach, and a large number of other chemicals will rapidly create oxides and their chemical relatives on metal surfaces. I have personally used bleach to almost instantly "rust" a length of brand-new shiny metal chain for use as a halloween prop. It was much easier, more authentic looking, and more durable than painting it...

CLR, Tarn-X, vinegar, or another acid would be much better alternatives.

Edited by A.J. Franzman, Sat Jan 1, 2011 1:12 AM.

[batari]

A.J. Franzman, on Sat Jan 1, 2011 1:06 AM, said:

batari, on Thu Dec 30, 2010 6:35 PM, said:

I looked some up and see that hydrogen peroxide can act as a reducing agent.

5-11under, on Fri Dec 31, 2010 2:48 PM, said:

I'm trying the hydrogen peroxide right now. It's only 6% solution, and the chips are pretty "dirty", so I've got my doubts.
If I had some CLR, I'd try that. I have no idea if it will work, but it'd be a simple solution if it works as well as the commercials.

You Fail Chemistry Forever. Hydrogen peroxide is an oxidizer, which is the opposite of a reducing agent.

Nope. Hydrogen peroxide can act as either an oxidizing or reducing agent.

Funny link though.

[Richard H.]

I have one chip soaking in vinegar. Will let you know if it works by tomorrow (it will have had 48 hours by then).

[5-11under]

If the vinegar works, it's an easy solution. I might try it myself starting tonight. Coca Cola might work the same, but is messier. The weak hydrogen peroxide did not work.

[A.J. Franzman]

When MythBusters did Coca-Cola myths, they found that it didn't work as an engine degreaser, but it worked at least as well as a leading commercial product (!) for cleaning rust off of chrome bumpers. So it may actually work better than vinegar for de-oxidizing those IC pins.

[batari]

When I used to collect coins, I found that adding a little salt to the vinegar rapidly increased the reaction time. That is, it would clean them in seconds instead of hours.

I was also thinking an electrolysis method may also work. Try a weak salt solution with a small current and two metal plates, and rest the chip on one of the plates (or perhaps hold it down) on the plate to make better contact. Alternatively you could try a non electric method like holding it against a plate of galvanized steel in solution.

Does anyone know what metal chip pins are made of? Tin maybe?

[Richard H.]

The vinegar soaking did not work at all

[Video]

Richard H., on Wed Jan 5, 2011 12:32 PM, said:

The vinegar soaking did not work at all

How long did it soak? I know, oddly, that if you soak metal in vinegar for a frew hours, it can take rust off...but if it stays in to long, it will actually reverse the effect and cause the metal to rust.

Heh, plaiting, that might be cool, if you don't fry the chip.

Try jewelry polish, or maybe you can use toothpaste, it takes some scratches off CD's, maybe it can help on metal too?

[Dave Neuman]

Richard H., on Wed Jan 5, 2011 12:32 PM, said:

The vinegar soaking did not work at all

Maybe Naval Jelly

http://www.ehow.com/...aval-jelly.html

[A.J. Franzman]

batari, on Tue Jan 4, 2011 7:01 PM, said:

When I used to collect coins, I found that adding a little salt to the vinegar rapidly increased the reaction time. That is, it would clean them in seconds instead of hours.

[snip]

Does anyone know what metal chip pins are made of? Tin maybe?

Vinegar (acetic acid) is a weak acid. Acetic acid + NaCl (salt) produces hydrochloric acid, a strong acid. But everything I've ever read on coin collecting says don't clean them, if they have any value, because you'll only reduce it.

I'm not sure about surface-mount IC leads, but I know older through-hole component leads were typically either copper or mild steel, tinned with either pure tin or the usual 63/37 lead/tin solder. You could tell the steel from the copper because the steel ones are attracted to magnets. Today they're probably all tinned with either pure tin or one of today's 2/98 silver/tin solders or some similar low toxicity stuff, but I don't know if IC pins now are copper (doubtful -- too soft), plain mild steel, or some specific alloy.

Edited by A.J. Franzman, Thu Jan 6, 2011 12:06 AM.

[Richard H.]

Quote

How long did it soak?

About 50 hours. I took a look at 24 and there was no change.

Some of the legs appear to have even more oxide on now

I'm just wondering if it's worth buying one of those ultrasonic water bath cleaners.

[A.J. Franzman]

An ultrasonic cleaner by itself will not remove any oxidation except that which you could just as easily scrub off with a stiff brush, but it will usually speed up most cleaning/chemical baths significantly. First you need to find something that works.