Question: Once a wire is pre-tinned with lead free – no clean solder, can it then be considered solid wire and then be soldered to a PCBA using water soluble flux?
Answer: There are no restrictions as to the flux to be used to solder wires to PCBA. The restriction comes from the specification IPC/J-STD-001 – Paragraph 3.3 Flux, stating within the paragraph that “… Type H or M fluxes shall not [D1, D2, D3] be used for tinning of stranded wires.”
Once the wires are tinned and assembled to their respective terminations, be it either a terminal, or a printed circuit board, other approved fluxes can be used to make those connections. The option to clean will be based upon the flux type used and should be specified on the assembly documentation.