I"ve just tried Tining a board with Silver solder paste and it worked really well and a very small amount goes a long way as the silver seems to go on much thinner than the Solder does....
The problem with the Silver paste is that it is a Bit pricey at about $5 for 1/4 ounce but I tinned a 6in x 6in board with a drop the size of a pea.....
The problem with the Silver paste is that it is a Bit pricey at about $5 for 1/4 ounce but I tinned a 6in x 6in board with a drop the size of a pea.....
there's that confusion between tin plated (Sn) and tinned (Pb/Sn).EdT said:
Both solder easily.
Does an electroplated version of tin plated as against hot dip tin plated produce a clean electrically bonded surface that solders well?
Similarly does a chemical deposition layer solder well or is it full of pock marks?
Like I said, tin alone affects the copper in a bad way, as well as having a tendency to grow whiskers over time, eventually leading to shorts.
It is possible to electroplate with solder (tin/lead). That's what my initial question was about.
As for using wicking braids -- with the current prices of copper, not to mention the projections...
It is possible to electroplate with solder (tin/lead). That's what my initial question was about.
As for using wicking braids -- with the current prices of copper, not to mention the projections...
No one in the PCB manufacutring industry plates tin, they just wet tin on and blow off, they do gold plate traces and pads though. By tin I mean 63/37 Sn/Pb eutectic solder. Tin or lead by itself has a higher melting temperature than a of mix 63/37 Sn/Pb, at this precise ratio it becomes an eutectic alloy meaning it turns from solid to liquid without a slush stage unlike older 60/40 solder.
Nixie said:
I have purchased parts which have been plated with lead and tin. It is done at the same time, in one bath.
The primary issue was one of deposition rate. One metal plates differently from the other. There is a correct current density which gives the proper deposition ratio, go over it and one metal plates more, lower, and the other metal.. From what I can remember, the deposit goes lead heavy where the current is lower, but that was long ago.
All the plating vendors I dealt with did not electroplate solder, just seperate lead and tin. The plated surface may have the correct alloy ratio, but it is not yet solder, it needs to be reflowed. Plated only is porous, the base metal will oxidize until the plating is reflowed.
The only problem with removing molten solder is the possibility of removing too much, leaving a copper/tin alloy. This alloy can be difficult to solder to as the flux is not normally good enough to cut this.
Cheers, John
Gold, yes. Tin forms an oxide, but that oxide is easily stripped by low activity fluxes.AndrewT said:
Gold unfortunately embrittles a solder. The best gold thickness for solderability is about 50 microinches, and not a bright finish, but a matte.
Soldering to copper is two stage...first, a copper tin alloy forms at the copper surface, it is yellowish in appearance...then a second copper/tin alloy, this a more whitish look..then, over that is the solder alloy itself.
If you wipe the solder alloy off with a cloth, you can expose the second copper/tin alloy...this is the hard to solder part I speak of. It requires an activated flux to form a metallic bond during subsequent soldering.
Cheers, John
Hi John,
these two copper/tin alloys;
are they different chemical compounds or different proportions of alloy mixture.
I note that lead didn't get a mention in either layer.
Does the lead only appear in the solder layer? Is this layer richer in lead compared to the parent solder ?
Presumably, if the underlayers of copper/tin are not exposed then soldering to the covered layers is always easy with conventional fluxes?
When you talk of activated flux, what exactly needs to be specified?
these two copper/tin alloys;
are they different chemical compounds or different proportions of alloy mixture.
I note that lead didn't get a mention in either layer.
Does the lead only appear in the solder layer? Is this layer richer in lead compared to the parent solder ?
Presumably, if the underlayers of copper/tin are not exposed then soldering to the covered layers is always easy with conventional fluxes?
When you talk of activated flux, what exactly needs to be specified?
AndrewT said:
Different alloys. The one closest to the copper is Cu3Sn, the next is Cu6Sn5.
I googled to find this, I could not find the article I was thinking of, it's somewhere in this darn office.. man, google has been very good to me lately..
http://www.ami.ac.uk/courses/topics/0156_intm/index.html
AndrewT said:
I would assume so, but the two intermetallic layers are not that thick.
Yes..that has been my experience.AndrewT said:
AndrewT said:
I can use R for all my work. When the molten solder has been wiped, R will not work at all, forcing RMA or heaven forbid, RA. Or, removing the mess and starting at bare copper again.
Cheers, John
AndrewT said:
Give or take.(I'm hedging my bets...
)Copper is soluble in solder.. If the wires are small enough guage, they quickly dissapear in a solder pot.
The cu/sn intermetallic formed freezes two degreees C above pure solder, this gives a sandy/grainy surface finish if the pot is too contaminated with copper.
That little tidbit came from a different paper and also duplicates my experience.. that paper did not elaborate on which alloy it was, I never bothered checking on which either.
Cheers, John
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