There's silver epoxy but that's outrageously expensive. Googling shows that you can add fine graphite powder to some kind of epoxy, to get something like that

There's silver epoxy but that's outrageously expensive. Googling shows that you can add fine graphite powder to some kind of epoxy, to get something like that maybe. Still glue is not super easy to control, and can't be used for fine traces. If the glue leaks across two pins, you can't just remelt it with a soldering iron.