Chapter 3.2.2 on Solder Purity Maintenance states:
|Solder used for preconditioning, gold removal, tinning of parts, and machine soldering shall be analyzed, replaced or replenished at a frequency to ensure compliance with the limits specified by IPC. If contamination exceeds the limits, intervals between the analyses, replacement or replenishment shall be shortened. The frequency of analysis should be determined on the basis of historical data, or monthly analyses.
Records containing the results of all analyses and solder bath usage (e.g., total time in use, amount of replacement solder, or area throughput) shall be maintained for a minimum of one year for each process/ system.