Lol, that amount of solder accounts for maybe... 0.0001% of the solder used in the product. Usually its like a cap repair or something
Think about this:
1) risk throwing away entire device because of some trace de lamination that occurs on a 12 layer PCB because of excessive heat (those boards are practically one time use). Factor in all the other costs associated with telling the customer that you broke their stuff. Thats about a pound of e-waste generated.
2) tolerate a few milligrams of lead.
Its not plutonium.
The amount of energy saved by reducing the demand for manufacturing demand for even more phones to end up being burned in Africa totally covers all the downsides of using lead.
How about you go after lead on historical building roofs? It's actually alot compared to the amount of lead used in many years of equipment repair, and its still considered basically nothing.
I am telling you that there is so much more hidden lead being used in all sorts of industries that ends up polluting stuff that this is a absolute waste of time to consider.
here is one, how about you go after lead acid batteries instead. Thats like going after a match stick burning when there is a whole city that is in conflagration. One incorrectly disposed LA battery (not counting stuff like lead contaminated acid leaks that get on the road) probobly equivalent to many years of SMD caps being replaced in every repair shop in the world. A boat that sinks? A car crash that ruptures the battery and scatters it ? You are talking pounds every time, tons of crumbling lead oxide dust, etc. And lead acid battery is just one of them.
Hell, tons of old cars are soldered together with lead thats slowly disintegrating along the roads as well (used to be a way to attach the roof of a car).
And then you also create a industry of high precision soldering tools that is bound to be extremely wasteful when people try to figure out a way to get lead free to work right for shitty consumer item repairs. Why build tools that you don't have to? I can imagine all sorts of efforts going to making all sorts of crazy shit to replace 10 miligrams of lead on a SMD capacitor reliably. Easier repair = less waste. The amount of general industrial waste that won't be produced if you reduce yearly electronics demand by 10% (facilitated by easy repairs) is extremely large. If people start getting the idea that your average repair shop is gonna fuck up the repair (they already have a bad reputation!), you will just have more people saying fuck it and buying a new phone, laptop or videocard. It's setting up the repair industry to fail.
Look at the pakistani car battery repair industry (and their practices) and you will see that going after a phone repair shop is just
preposterous. (tldr, they do open air casting of lead plates in the desert with high wind and dry conditions, it must spread lead dross everywhere within 1000 miles lol, ). And don't fail to consider coal and stuff, which ends up making lead vapors from operations. by tightening down emissions regulations for mineral based industries you already have a sea compared to the drop. For instance dust control on open air mines (they leave heavy metal laiden dirt on top of the ground), coal processing, minerals processing water (you get lead compounds in the wash water), land reshaping projects, etc. Probably tons of lead contaminated industrial water are mixed with normal water every day also post discharge (try to ensure that all water extracted from the earth is drinkable, and do not allow for 'industrial grade' water to be used.. good luck doing this in some places, you have special water sources that everyone knows you cannot drink).