Cell soldering technique.

[snowcrow]

  After a good many broken and warped solar cells, I noticed the board I was using to solder on was getting scorch marks from the heat transfer through the cell. Well.. if there was that much heat being transfered through a cell its time for me to take a new approach to the problem!

  I decided it was time to try soldering both sides at once to just see what would happen?  Well.. it turns out that it work really well, as long as tabs are lined up with in reason both top and bottom!!  I just waited for solder on the tab beneath to melt before I started moving the iron. I did turn up the heat to the full 40 watts for this operation!!

 As the tabs cooled the cell stayed perfectly flat, to my amazement!!  This is a wonderful thing, both sides cool at a close enough rate so that the stress on the cell are kept to a minimum!!

  The only two main issues in can see with using this method are, cleaning the strings of cells and making sure that your iron is hot enough to do the job in one pass.  I've try to do touch-up and found that its best done right the first time around!!

Blessings, Snow Crow

[snowcrow]

Here are some scanned photos of a test cell using this method of soldering.

Try it on a few scrap cells, I think you'll like it!!

Blessings, Snow Crow

[tecker]

Liquid solder flux . the tabing is tinned and the cell is usually tinned the liquid flux readys the solder in front of the tip to pool .

[RCpilot]

Sounds like a plan, as soon as I am able to use my hand again I plan to try this as well. What was the cell laying on while doing this?

Kelly

[snowcrow]

  The test cell was on .25" plywood when the soldering was done, but I plan to do a few more test with aluminum and steel as a solder table to see what works best.  I may also attach a couple of power resistors to the solder table for preheating and make it a soldering jig.

  If you look close enough at the cell's bottom view, you can see the wood grain transfered to the tabs.  A smooth preheated steel surface for a the table would most likely do the trick!!

Blessings, Snow Crow

[snowcrow]

I did use Liquid solder flux, but I choose to use the "Felt Pen" applicator in stead of the bottled type because it applies just enough to do the job and requires the "NO" clean-up, if you do it right.

  As far as the cells being tinned, I don't think I've seen any of the newer one to be tinned at all.  They all come "bare Bones" as you see above.  I guess it makes for easier shipping, and with chance of damage during shipping.  I guess if the whole cell was tinned it would give you a little more current, but is it really worth the bother? How many cells will get broken trying to do so?

Here is a photo of the Flux Pen.

Blessings, Snow Crow

[howlet]

Too much heat from the soldering iron can damage the cell. Check a cells output both before and after you solder to make sure that you are not losing power. Have fun!  JB

[howlet]

     Ive been doing my tabbing and interconnecting of cells on a sheet of tempered glass that is laid on my workbench.

 The glass absorbs the heat so when you move on to the next cell, it is being sort of preheated and takes less time.

 Other advantages Ive found from this is excess flux from the opposite side soldered joint is deposited on the glass and can be scrapped away with a razor blade.

  Just seems to work better for me.                 Jeff

[howlet]

 There appears to be some discoloration at the solder joint, thats why I mentioned checking the output of the cell. JB

[snowcrow]

  Thanks howlet, the tempered glass sounds like a good choose for a heat sink.  The cell output has not been that impressive in the before short circuit testing.  I didn't find any that put out the 6 amps claimed!?  After soldering the tabs on three cracked cells and soldering them together, I did see and 2.5 amps.

  I did take a quick look at the panel you made and noticed you used smaller cells.  I think I just made the wrong choose in buying the biggest cells I could buy!!  The 6" round cells are just too hard to work with partly because of the shape itself.  I did notice while soldering partial cells, that the expansion and contraction difference between cell and tab, was no where near as great, as doing a full cell. This may be the reason I don't see that many panels with 6" round cells!!  A smaller two tab cell would have been a better choose for my first panel.

  As for the discoloration on the cell, the dark area next to the tab is flux.  The cells were not even in color from the start, something to do with the anti-reflective surface coating.  Part of the discoloration you see is due to my scanner.

  Well... I guess I'll just have to make the best out of a bad situation and just press on to get this one panel done!!!!!  I'll buy smaller cells next time for sure!!

Blessings, Snow Crow

[snowcrow]

  Thanks howlet, the tempered glass sounds like a good choose for a heat sink.  The cell output has not been that impressive in the before short circuit testing.  I didn't find any that put out the 6 amps claimed!?  After soldering the tabs on three cracked cells and soldering them together, I did see and 2.5 amps.

  I did take a quick look at the panel you made and noticed you used smaller cells.  I think I just made the wrong choose in buying the biggest cells I could buy!!  The 6" round cells are just too hard to work with partly because of the shape itself.  I did notice while soldering partial cells, that the expansion and contraction difference between cell and tab, was no where near as great, as doing a full cell. This may be the reason I don't see that many panels with 6" round cells!!  A smaller two tab cell would have been a better choose for my first panel.

  As for the discoloration on the cell, the dark area next to the tab is flux.  The cells were not even in color from the start, something to do with the anti-reflective surface coating.  Part of the discoloration you see is due to my scanner.

  Well... I guess I'll just have to make the best out of a bad situation and just press on to get this one panel done!!!!!  I'll buy smaller cells next time for sure!!

Blessings, Snow Crow

[howlet]

 Hi Snowcrow, Finding a soldering technique that works is tricky. The technique that works great for the front of the cell almost never works for the back side. Thats because the bus fingers on the front and back of the cells are composed of different materials.

  Having a soldering station with an adjustable temperature control is a life saver. When tabbing or stringing you must find the right temperature,flux, and tinning combination that will give you a small, smooth, steady puddle of solder that can be pushed or pulled down the length of the solder joint. It is alot like Tig welding. In an ideal situation, your Iron will barely be touching the puddle of solder.

 A proper string wont have any excess solder buildup on the top of the ribbon. Hard to do sometimes.

 Glad to see others making their own panels! I'm about to finish one this evening. Getting ready to laminate. I'll post some results. JB