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Comment by photochemsyn | Hacker News Reader

There's a huge differential when it comes to processing different panel types, such as First Solar's CdTe panels (cadmium is a toxic heavy metal) versus the monocrystalline silicon panels that China is making (apparently only China has managed to scale up monocrystalline silicon, with the machines as tightly held secrets as ASML's EUV systems).

You'd think that would be a primary point of discussion in any article on solar panel waste, but no.

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That is because CdTe is actually a stable molecule that isn’t water soluble, turns out the problem of panels from a toxic leeching perspective is largely from the small amounts of lead used at soldering points which is a common point with most silicon PV panels.

No reason tin can’t be used instead/lead free panels can’t be made except for the saving of a few pennies by skimping on the solder - no regulations to ensure they should be lead free. Unfortunately waste processing decades into the future isn’t often accounted for and those few pennies at design time add up across hundreds of thousands of panels on a single site…

Nowadays everything is "ROHS", even in the US, so not even lead.

Have they actually made a decent lead-free solder yet?

Nope.

Yes. You just need to set your iron a fair bit hotter and learn to live with matte solder joints.

Also, typical lead-free solders oxidize in air at their soldering temperature much more readily than near-eutectic Pb-Sn at its respective soldering temp.

That oxide film tends to interfere pretty badly with wetting of surfaces being soldered. In other words - it's much easier to end up with a "dry" joint - even with adequately increased temperature - unless better and/or more flux is used.

Not doubting the facts you've mentioned, but in my experience I've had no problems getting the surfaces to wet, though that may just be due to using rosin core solder that happens to have a good flux in it.

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