Type of Solder? High Tin% or Silver

[BilljustBill]

Overview: At some point, I'm going to start a long solar panel containing up to three individual strings of 36 cells. Over the past five years, I have gathered both 4x4" and 5x5" poly cells at some rather good prices. I'll be using a shower door that has a wide aluminum frame for easy mounting of the tempered glass face, metal wall stud material for framing, and cement board (Hardy Board) sheeting sealed with epoxy paint and PV sealants for the sides and back panel. It might be a bit bulky and on the heavy side, but on a ground based mount, two people can easily attach it.

I found a new and factory sealed tube of silver solder rods at the local monthly flea market for $15. The same type of solder a local successful HVAC company uses when installing their Trane brand products. Does silver solder require too hot a temp to be used when tabbing together rows of 18 solar cells? Is 60/40 solder good enough?

I have a good soldering iron that has a stable temp design, I use for making copper foil stain glass windows. Will it be good enough?

What type of flux works best on solar cells? Do you rinse them with a neturalizer and let them thoughly air dry before you enclose them?

Thanks, Bill

[Mike90250]

Silver solder would be my 2nd choice. 63/37 Sn/Pb electronic solder, with a rosin flux, is the ideal. If you are not allowed the best tool (tin/lead), then the silver solder is the next best thing. http://en.wikipedia.org/wiki/Solder
Silver solder requires more heat.

Rosin flux can be removed with a cotton swab dipped in alcohol, even drug store 70% rubbing alcohol is fine.

/begin rant/ As to lead free solders, while tin works, it has an annoying habit of spontaneously growing "whiskers". In a few years, as "lead free" electronics fail, and have to be scrapped (finding the fine whiskers that cause the fatal short is near impossible) the waste caused by the failures, will exceed the waste if a proper 10% lead content was retained.

http://en.wikipedia.org/wiki/Tin_whisker

[Guest]

Hey Mike. So whats your first Choice?
I need to know...
Thanks!

[foo1bar]

Hey Mike. So whats your first Choice?
I need to know...
Thanks!

He already said - 63/37 - ex:
http://www.amazon.com/Kester-Rosin-C.../dp/B0149K4JTY or

http://www.amazon.com/Kester-Rosin-Core-Solder-Spool/dp/B00068IJWC

(I'm sure there's cheaper sources. Especially if you don't need a lot. But lead based solder is still readily available)

[Guest]

Ah okay I misunderstood.
Ya Im browsing around looked at the wiki he posted.
Im just wondering about some things myself.
I think the only way to go about this finding the right supplier with the right solder that works best.
Obviously Tin-Silver is best.

But what about Tin-Silver-Copper?
Or perhaps a Tin free Alloy solder

Right now im using Lead free Tin Silver BernzOmatic 0.62/1.6mm

http://www.ebay.com/itm/BernzOmatic-SRC300-3-oz-Lead-Free-Rosin-Core-Solder-New-/351571858354?hash=item51db50d3b2:g:JZoAAOSwKIpWEyYS

[solarix]

The electronic has been forced to develop lead-free solders over the last decade or two. In Europe, to be certified for sale with the CE mark, a product has to be lead-free and this has caused companies world wide to abandon good old tin/lead solder. While I agree with the dangers of lead, the new solders just are not nearly as reliable. Lead gives solder some flexibility and the new lead free circuitry just doesn't handle hot-cold cycling long term. This might not be as big of a problem on something like solar cells which have large surface areas, but on miniaturized circuitry it is. Notice how cellphones barely last a couple years? Guess what kind of solder is used in microinverters? Adding silver to solder is a big improvement (also a big cost hike) but doesn't make up for removing the lead. This is just my two cents of course as my circuit board magazines swear up and down how the new solders are just as good. Just get some of each and try soldering with them. You'll see what I mean. Just try taking any modern circuit board and try unsoldering some components and you'll see how hard lead-free is to work with...

[Guest]

Some good points there. I will defiantly get Lead solder and try it out. If its better for hot cold conditions you kinda want that for solar cells. But not sure if its a better conductor than tin-silver
Im sure after a couple of years with your solar cells being in sunlight and exposed to cold elements your tabbing will somewhat come loose from your solar cell...

[foo1bar]

But not sure if its a better conductor than tin-silver

So if you use a lead based solder it'll be 14.5 ohm-cm instead of 12.3 ohm-cm? (that's what I could find for resistance values)

I'm guessing that the wires will account for at least 90% of the resistance in the circuit. Which means using tin-silver instead of a lead solder would be a 1.5% better.
If the wires (and other stuff) are 95% of the resistance, then you're at ~0.75%; if it's 99% then it's ~0.15%

So I'd use what works best for the manufacturing - it'll save time which is probably worth more than the extra losses from the small increased resistance.

Im sure after a couple of years with your solar cells being in sunlight and exposed to cold elements your tabbing will somewhat come loose from your solar cell...

I wouldn't expect that. If that happens, IMO it wasn't manufactured correctly. A good solder joint should last for decades - even with thermal cycling and UV exposure.

[Guest]

I will run a bunch of tests on different soldering products. So I want to know exactly which would outperform the other in terms of resistance. They could state that this product does so and so, But in reality it could do much poorer that products labeled the same as the next.

[Mike90250]

silver solder is likely way too hot for PV cell tabbing, and is likely to remove (dissolve) the metal film traces on the cells you are trying to solder too.

[Sunking]

Don't use silver, it requires too much heat. You have been warned.

[Guest]

So Lead free Tin Silver BernzOmatic 0.62/1.6mm not good then?
What do you really advise?

Ive been using this and with very high heat... And the cells turn out okay, It welds itself pretty good. And the volt output dosnt seem to be damaged efficiency.

I will purchase the Kester Solder you recommend.. What temp do you guys use with this solder.

Everytime I solder its not very perfect... I know its the type of solder and perhaps it is the silver and the high temps not giving me clean uniform soldering..
Even though the cell still produces .60volt for a 6x6 poly cell

[Guest]

Okay heres the thing. My solar cells are made of 3 busbar Silver.
Do you think Silver on Silver+Tin solder is safe for it you think?
I know you recommend Lead-Tin-silver

Just curious what your thoughts are.

And the tabbing Wire itself is Tin-Copper.

[Mike90250]

Silver solder would be my 2nd choice.

63/37 Sn/Pb electronic solder, with a rosin flux, is the ideal.

> So Lead free Tin Silver BernzOmatic 0.62/1.6mm not good then? NO

[Guest]

Intresting. I will put it to the test when I get the some
As it stands I dont feel like its a good conductor Tin and Lead alloy in my solder...

Be nice to have straight Silver and maybe conductive glue?
I noticed this conductive glue floating around on ebay.. when i search for tabbing wire