Issues when soldering back of solar cells

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  • thunderbird
    Junior Member
    • Sep 2014
    • 4
    #1

    Issues when soldering back of solar cells

    Hello everyone,

    I am building my first DIY panel with solar cells from eBay (deleted by Moderator) shop.

    When tabbing the back of the cells, the (I"ll call it "solder pad") sometimes kind of "evaporates".solar_cell_back - Copy.JPG

    I've read and watched countless instructional videos which gave two options for soldering the back tabs:

    1) Add flux, solder the tab wire (by heating it up slowly by slowly moving the iron tip and pressing lightly to the cell while sliding over it)
    2) Add flux, pre-solder, then put the tab wire on top and heat it up by slowly moving the iron tip and pressing lightly to the cell while sliding over it

    I've tried both and both do result in the issue as shown in the attached photo. In case of (1) the tab wire doesn't always stick firmly enough and tend to come of when moving the cells (I do add a sufficient amount of flux). In case of (2) sometimes parts or even more than shown on this photograph are not soldered by sliding over the iron tip but it does look likes the "adhevise pad" (don't know how to call it properly but I mean like it comes from the shop as shown in the right part of the photo - the silver-ish pad- evaporates instantly when sliding over the iron and adding some solder. Note that I don't keep my iron for a long time on the pad, I just slide over.

    Anyone had this issue too? Any ideas what could be the origin of this issue? I've tried a colder iron tip as well as a hotter tip, both still result in the same issue.

    Do you know if these kind of issues will influence the performance (in a bad way) of my solar panel?

    Thank you very much for any help!
    Last edited by Mike90250; 09-06-2014, 06:22 PM.
    Tags: back, cell, tab wire, tabbing
    • Mike90250
      Moderator
      • May 2009
      • 16020
      #2
      The metal layer on cells, is only a few atoms thick, and it dissolves in solder.

      My suggestion, add a little (just a little) more solder to the tab wire. Then flux the cell backside. Lay the flat tab wire on the backside, and gently drag your hot iron down the tab wire, allowing the heat to flow thru the tab wire, and reflow onto the cell.

      i don't advise tinning the cell, then adding the tab wire, that's 2 heat cycles, and you loose more metalization than just one pass would.

      Lead free solders generally need higher temps than real tin/lead electronic solder. Lead free "solder" is something else, like crappy hot melt glue. Solder contains lead. I've used plenty of both.
      Last edited by Mike90250; 09-06-2014, 06:28 PM.
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        Comment

        • thunderbird
          Junior Member
          • Sep 2014
          • 4
          #3
          Thank you very much Mike! I will try that tomorrow.

          Any idea what's best: lead free "solder" or the "lead containing" solder?

          I've used the last one (because of the lower temperature needed but also the better "strength".

            Comment

            • inetdog
              Super Moderator
              • May 2012
              • 9909
              #4
              Originally posted by thunderbird
              Thank you very much Mike! I will try that tomorrow.

              Any idea what's best: lead free "solder" or the "lead containing" solder?

              I've used the last one (because of the lower temperature needed but also the better "strength".
              The only reason for using lead-free solder is concern about toxicity. And some of that is more regulatory (zero tolerance) than practical for uses on the scale you are looking at.
              There are, AFAIK, no thermal or mechanical advantages to any commercially available lead free mixes when you are looking at low temperature work.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

                Comment

                • thunderbird
                  Junior Member
                  • Sep 2014
                  • 4
                  #5
                  Thank you very much inetdog!

                  I am looking forward to the new suggested soldering technique (add just a little extra solder to the tab wire and reflow it)

                  Enjoy the weekend!

                    Comment

                    • ZoNiE
                      Solar Fanatic
                      • Jul 2014
                      • 129
                      #6
                      Solder with Lead is usually easier to use and melts faster. 2X on the advice given here, tin the wire, lay it down, then apply heat. You may try a lower temp on your iron, and forget the flux, the rosen core solder already has enough.
                      Last edited by ZoNiE; 09-10-2014, 02:19 AM. Reason: transposition
                      House-Sun Earth Hot Water.
                      RV-390W Kyocera, Kid.

                        Comment

                        • thunderbird
                          Junior Member
                          • Sep 2014
                          • 4
                          #7
                          Thank you very much ZoNiE! I'll try that. It is good to know that I can forget about the flux!

                            Comment

                            • Loki000
                              Junior Member
                              • Dec 2014
                              • 1
                              #8
                              I've tried both and both do result in the issue as shown in the attached photo. In case of (1) the tab wire doesn't always stick firmly enough and tend to come of when moving the cells (I do add a sufficient amount of flux). In case of (2) sometimes parts or even more than shown on this photograph are not soldered by sliding over the iron tip but it does look likes the "adhevise pad" (don't know how to call it properly but I mean like it comes from the shop as shown in the right part of the photo - the silver-ish pad- evaporates instantly when sliding over the iron and adding some solder. Note that I don't keep my iron for a long time on the pad, I just slide over.
                              NAT

                                Comment

                                • ZoNiE
                                  Solar Fanatic
                                  • Jul 2014
                                  • 129
                                  #9
                                  Originally posted by Loki000
                                  I've tried both and both do result in the issue as shown in the attached photo. In case of (1) the tab wire doesn't always stick firmly enough and tend to come of when moving the cells (I do add a sufficient amount of flux). In case of (2) sometimes parts or even more than shown on this photograph are not soldered by sliding over the iron tip but it does look likes the "adhevise pad" (don't know how to call it properly but I mean like it comes from the shop as shown in the right part of the photo - the silver-ish pad- evaporates instantly when sliding over the iron and adding some solder. Note that I don't keep my iron for a long time on the pad, I just slide over.
                                  You may have adhesion issues from surface oxidation/corrosion. A gentle rubbing with alcohol, or a horse hair brush with short bristles will clean off any crud and allow better flow of the solder. I do NOT know how Alcohol will affect the rest of the device, but probably would be OK.
                                  House-Sun Earth Hot Water.
                                  RV-390W Kyocera, Kid.

                                    Comment

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