Type H or M fluxes should not be used for what purpose?

Type H or M fluxes are specifically formulated for use in processes that require a more robust cleaning capacity and are designed to function in harsher conditions typically associated with specific types of electronic assembly. They can be more aggressive in terms of their chemical action, which is ideal for applications where stronger cleaning capabilities are needed prior to soldering. However, using Type H or M fluxes for tinning stranded wires is not advisable due to the potential adverse effects that such potent fluxes can have on the wire and its insulation.

Tinning stranded wires involves a careful process to ensure that the strands are adequately coated with solder without causing damage to the wires or compromising their electrical insulation. The aggressive nature of Type H or M fluxes can not only lead to excessive corrosion but might also leave residues that would require extensive cleaning afterwards, defeating the purpose of the tinning process. Therefore, while these fluxes serve important roles in certain soldering applications, their use for tinning stranded wires is not appropriate.