turnished solder

What is this turnish of which you speak? Why would it matter if there was an encoder on the board?

Are you posting from a phone using autocomplete? TURN IT OFF.

You could try a soldering iron.

You won't like the taste.

Mark L. Fergerson

Can you post a photo? How old- tin gets really hard to solder. HASL is less of an issue. Cardboard has sulphur that tarnishes PCBs.

A Scotch and water would do something for me.

X-posted to a more appropriate forum.

Jamie - try the silver tarnish remover on a scrap board to see if all works well. I've used tin/silver solders enough to consider the two close neighbors but lead may not fit. Vinegar or maybe a stronger acetic acid might be worth a test run too.

Hul

M Philbrook wrote:

I do not understand your description of turnish but I interpret it as tarnish. Are the connections completely corroded? Can you describe their condition in more detail or provide a photo?

I will try to help based on my experience but I need to ask a few questions:

• Do you want to just clean the connections or de-solder and then re-solder?

• Have you tried re-soldering the joints at all? If so, what were your results?

• Have you tried using RA (Rosin, Activated) flux and re-soldering? You can use lacquer thinner to clean the board after soldering/re-soldering. Keep the lacquer thinner away from things that it will dissolve.

Older boards as in tin-lead solder? Or perhaps RoHS solder containing silver, which will tarnish if exposed to H2S or other sulfides?

If you're not sure if it's leaded solder, you can test for lead with a hardware store lead test kit: If that's too expensive, just ADD some tin-lead solder to and existing connection. If the resulting solder joint is shiny, the base solder is tin-lead. If it's a dull color, that kinda looks like a cold solder joint, the base solder is some flavor of RoHS solder.

Hard to tell without identifying the type of solder and the chemical that's attacking it. If it's silver bearing solder, try one of these: I'm curious if ketchup works.

Drinking either would not be beneficial.

After you clean of the solder, you might consider protecting the PCB with an acrylic or wax spray.

Perhaps the OP is Canadian.

No, he lives in Connecticut.

From Urban Dictionary: "1. A boy, often named Paul, who has poor writing. Usually, a "turnish" will write in all caps making it difficult to decipher maps they have constructed."

I asked for a suggestion to an issue as poasted! I didn't ask for a spelling or grammer check. I don't always proof read when I am in a rush.

If you don't have anything to offer in reguads of a honest question? Please don't waste my time or others.

My current practice of board rework works fine with kapton tape, liquid flux, alcohole and the occasionalal replacement of solder pads, hot air, current heating etc.

I was simply looking for a more modern way of removing corroded solder from the parts/pads with less work/damage.

Thank you for your useless contribution.

I could post if I had one of the boards here, its at my work bench at work and I am home atm.. Making new boards with a modern design hasn't attracted the massa's at the moment. So we do some rework (repairs) sent to us from other divisions. I was looking to see if there was any specific checmical being made to help remove the surface of corroded solder without digging up the exising surface and damaging pads / vias.

Currently I use kapton tape to cordon off surrounding areas, alcohol, liquid flux, paste at times, Hor air, current heating, and the occassional replacement of pads/traces.

I did try silver tarnish remover, it only works on small levels of corrosion. I guess I was looking for a more agressive chemical ready made for the job. I've seen plumbers use an acid but I don't think that would go over well.

Thanks

Liquid RA flux. You can get it from MG Chemicals or Kester, among others.

Cheers

Phil Hobbs

Wax spray? that's interesting. I've used electrical varnish but I find it does not work well in areas where thise is fast pulses/RF in volved ;) These are leaded solder boards if that makes any difference.

I'll look into wax spray for electrical use.

Thanks.

You can dip the board in liquid flux and let it dry and it will be pretty well protected. You can get flux by the gallon (or maybe 4 liters) and it's not too expensive, but shipping tends to be pricey (hazmat charges).

--sp

Best approach I know is glass-bead blasting. It takes a glove box, a compressor, and some patience.

Second-best is wire brush (but beware deposition of soft metal on places that oughtn't conduct).

Metal polish (mild abrasive suspended in goop) will remove the soft oxides, but leaves a residue. That's sometimes a very bad thing.

Chemical treatments (vinegar was mentioned) will dissolve some of the lead, but that's not useful; it'll also attack copper, and create new corrosion where any dissimilar metals are encountered.

Best approach I know is glass-bead blasting. It takes a glove box, a compressor, and some patience.

Second-best is wire brush (but beware deposition of soft metal on places that oughtn't conduct).

Metal polish (mild abrasive suspended in goop) will remove the soft oxides, but leaves a residue. That's sometimes a very bad thing.

Chemical treatments (vinegar was mentioned) will dissolve some of the lead, but that's not useful; it'll also attack copper, and create new corrosion where any dissimilar metals are encountered. =============================================================

If you are going to bead blast, I think soda would be a much better choice than glass beads. First, I think even very fine glass beads will be too aggressive, even roughing up the board itself if you aren't very careful. Second, cleanup is going to be a pain. Fine bits of the beads will be embedded in every surface you actually blast, and will find every nook and cranny even on the other side of the board. Soda won't clean as fast but it will be much gentler on the board and components, and cleanup is just a water rinse.

----- Regards, Carl Ijames

Don't assume that by wax, I mean something that's as soft as candle wax or paraffin. It comes in many flavors and compositions. The main advantages of wax conformal coatings are:

1. Easy reword. You can solder through it.
2. It's waterproof
3. It's cheap
4. You can scrape it off connectors, pots, trimmers, grounding pads, and other places that should have been protected before spraying.
5. You can inspect it with a UV light.

The bad news is that it attracts dust and dirt but can be dissolved or melted off and replaced. It's also not very durable and can be scraped off by as little as vibrating loose wires. I've used it in the distant past on marine radios, but now I seem to be having a problem finding a vendor. There may have been a problem with wax. I'll do some googling later.

Other conformal coatings:

Yes, it makes a big difference in identifying the tarnish. See my previous reply to this question.

thanks Phil, and everyone else that dropped. I will get some of that flux tomorrow, get it ordered ;)

Jamie

just looking online here, Kester 1544, Activated Rosin liquid flux. We have some stuff now that I put in a hypo needle. Wonder if that is basically the same stuff?

Jamie

There are two common kinds of acid-treated tree-sap flux: Rosin Mildly Activated (RMA) and the more aggressive Rosin Activated (RA).

The stuff I usually use is MG Chemicals 835, but I also have a jug of Kester 1544.

Cheers

Phil Hobbs