Soldering of Bus Bars

System

Hi Everyone,

I am trying to fix one problem in manufacturing of solar modules. Problem is bubbles in the laminate after lamination on bus bar solder joints. As you may know the complete circuit is on the EVA and then the whole cell assembly is joined through bus bar through soldering. I have observed that during soldering heat is tranferred to the EVA and it starts to react which eventually create voids/bubbles.
Does anyone has any idea how can we minimize bubbles/voids across solder joints.

Thanks.

mike95490

Re: Soldering of Bus Bars

The solder melt temp is above the EVA rated temp. So either solder first, and then EVA, or you must look for a low temp solder. most of the 95% tin solders melt hotter then the 300 year old standard lead/tin solder. That leaves the very expensive indium and bismith solders, which lack the corrosion resistance, and could reflow on the roof in use. You will have to research this a lot, to find the right product. Here's a start http://www.indium.com/bismuth/

System2

Re: Soldering of Bus Bars

Thanks for your response.
The major difficulty I am having is we do laser soldering on interconnect joints which are already placed on the EVA. As soon as soldering happens, EVA gets heated due to transfer of heat during laser soldering. Therefore before we could laminate, reaction has already occurred in the EVA. This reaction I believe leaves behind bubbles/voids in the EVA.
Does anyone know a good insulator which we can put beneath bus bars while doing hand soldering.

Thanks.

mike95490

Re: Soldering of Bus Bars

Proper laser soldering should NOT melt any other materials. they should barely get warm. Material is too thick/heavy or you have settings configured wrong, too much laser.