Question:
We need to remove RMA solder flux on indium/lead soldered subassemblies. Most aqueous cleaners attack this solder.
Answer:
According to the Materials Handbook by GS Brady et al, indium lead solders are alkali resistant solders. Rosin based RMA fluxes are best cleaned by alkaline/saponifying cleaners with no conductive cations such as Detergent 8.
The organic amine in Detergent 8 forms a water soluble soap with the rosin. Because Detergent 8 is cation free, it cannot leave conductive residues. We recommend using a 3% Detergent 8 solution for ultrasonic immersion cleaning or a 5% Detergent 8 solution for manual cleaning of indium/lead soldered subassemblies.
Detergent 8 is a hazmat that most package sizes must ship by ground. You can ship a 5 gallon jerrycan of Detergent 8 by air.