Free oxygen? All the oxygen you can breathe for free?

Sorry Blocco, just had to pierce in and be silly.

Oxidation is the worst during soldering IF no flux is used. Nearly all solders have a flux core of some sort. Some are "No Clean", others are "Water Soluble" to name a few. "Rosin Core" is another, but this one you want to clean with some sort of flux cleaner. Depending on the exact chemistry of the flux it can be anywhere from very mildly corrosive to rather aggressive. And if you fail to clean it off it can deteriorate your work.

When you heat and reheat solder it dries out (so to say) and can appear as if it were a cold solder joint. That's because without flux oxygen begins to oxidize the surface (where oxygen contacts the molten solder) forming solder dross. Dross is the unwanted byproduct of hot solder. The purpose of flux is to replace the oxygen in the immediate location where the solder is being applied so it doesn't oxidize. It has other purposes as well, such as cleaning the surface of the copper pad to aid in solder wetting (adhesion of the solder to the copper).

As for storage of electronics - which the computer you're working from right now - has solder joints that were made some time ago. So no real application is necessary to prevent oxidation. However, an unprotected copper trace can become oxidized rather quickly if it comes in contact with something like the oils found on the human hand. It can tarnish - or if worse, it can corrode its way through the traces. For many years electronics were built without the aid of solder mask and conformal coating.

Solder mask is a protective coating on the board meant to protect all the areas of the copper traces that solder is not intended to be applied to. Conformal Coating is a clear coating (spray type is most common and is applied after the board is complete) is meant to protect the board from moisture. Some conformal coatings are very good at sealing a board and in such cases the board can be submerged in water and not suffer any ill effects from contact with moisture.

As for concerns over oxidation during storage - I wouldn't worry about it.

Hi Tony, does a coating of solder result in a good contact for a switch? I have switches that are operated with a shorting bar of copper or phosphor bronze - not sure how to tell - and they oxidize so that when the bar is pushed across two wires the contact isn't reliable. I wonder if coating the bar with a thin layer of solder will avoid this or will the solder oxidize too? Thanks in advance for your advice! Jim

Mod: link to old thread. @Tonyr1084
https://forum.allaboutcircuits.com/threads/oxidation-when-soldering.125832/post-1195177

 

Some kind of grease might be better. It should protect from oxidation and lubricate the sliding contact.

 

Hi Tony, does a coating of solder result in a good contact for a switch?

No. Absolutely not! Solder is an alloy of some two metals. For years the most common was Tin/Lead, usually 60/40 or 65/35, with Lead being the most prevalent metal. Silver solder is also an alloy of two metals. Off hand I don't know the mix. A google of silver solder should yield enough information about the alloy. While both are good electrical conductors they don't do well with potential arcing.

On the subject of arcing, switches rated for AC are not good for DC, not unless you stick to the amperage ratings on the switch. DC is harder on a switch because when breaking contact there's an arc. If the amperage is high enough that arcing can continue even though you've shut the switch off. With AC you have current that crosses zero 120 times (60Hz US, 50Hz non-US). When switches become oxidized it's typically best practice to replace them. Contact grease is a fairly good suggestion, but again, you have to be cognizant of the amperage and type of current (AC or DC). Arcing can still occur with grease, only the grease can become heated to its flash point and can become problematic or even dangerous. That's why there are UL listings that rate a switch type for a specific purpose. Don't violate those regulations because there's sound reason behind them.

Would you care to be more specific about how you are using your switch? It's rating, the type of current you're running (AC or DC)? How much current? The voltage? Armed with this information we can likely direct you to the best solution for your situation.

 

Here's a link to silver solder alloys:
https://en.wikipedia.org/wiki/Solder_alloys

 

Are you switching AC or DC? What is the voltage and current?
There are other preventative methods for arc suppression.

 

A good coating of solder will indeed avoid the problem of COPPER oxide, BUT it will not improve the durability of the switch. So the very important question is how much current is the switch carrying and how much current is the switch breaking?
SOME switches making and breaking higher power are submerged in insulating oil.
And most well designed switches have enough contact mass to avoid an excessive temperature rise. And often the contacts are an alloy created for switch contacts.

 

Years ago my go to was Cramolin for a cleaner and oxidation preventative. We used it on precision decade resistance box contacts. While I no longer see the stuff I am seeing where DeoxIT® (D100L replaced Cramolin (R100L) is a replacement. The stuff isn't cheap. CRC also has a line of good cleaners and preservatives for removing and preventing oxidation. So it's a matter of what you are switching and how deep your pockets are.

Ron

 

It keeps coming back to that one question: What are you switching? Of course we need to know the voltage, the type of current (AC or DC) and how much current. So far all we have is a question (post #1). Haven't heard back for a few days. Wondering how long it's going to take to get an answer.

 

Years ago my go to was Cramolin for a cleaner and oxidation preventative. We used it on precision decade resistance box contacts. While I no longer see the stuff I am seeing where DeoxIT® (D100L replaced Cramolin (R100L) is a replacement. The stuff isn't cheap. CRC also has a line of good cleaners and preservatives for removing and preventing oxidation. So it's a matter of what you are switching and how deep your pockets are.

Ron

DeoxIT is good stuff, similar to the much more expensive Stabilant 22A which is really amazimgly effective,