Case Study Series

Cleaning PCBs for Remanufacturing
–Stephen Griffith

Q: How long will the bath last? How do I determine bath life?

A: It is hard to determine due to your throughput -Bath Analysis NVR (non-volatile residue) Testing would be useful to determine soil load- with an analyzer such as a Mettler Toledo HE53.

Q: How do I measure concentration in an ultrasonic tank? (Can I use my refractometer?)

A: In the metal finishing world, oils mess with a refractometer, so we use conductivity and a conductivity meter to measure concentration. If we were cleaning just flux and solder paste, we would be utilizing a refractometer, and referring to the Refractive Index Chart from KYZEN will determine your Concentration.

Q: How do I know my boards are clean?

A: Depends on your spec- in this case, it was visibly clean. Since we are looking at oil, Dynes tests or contact angle tests would be the most useful. If we were cleaning PCBs during initial manufacturing, we would be looking at testing using Ion Chromatography.

Q: What do I do with my used wash solution?

A: This will be up to your state and local regulations. Typically, we find that the contaminants and soils are the problem with going straight to the drain, not the chemicals.

Q: Is it common to clean oils off the boards?

A: Not typically. Usually, when we are trying to clean PCBs, we are going after raw solder pastes and fluxes. But when remanufacturing is needed, multiple soils are often not on the boards during the initial manufacturing processes. You need a broad-spectrum chemistry that can handle a wide variety of soils, including solder pastes, fluxes, and oils.