Staining is often caused by reaction products, metal oxidation, or insoluble residues. Prevention requires control of chemistry, rinse quality, and drying.

Causes of staining and solutions

Causes include residual flux activators reacting with metals, iron contamination in water, and insufficient drying. Solutions include improved rinse water quality, passivation steps, and pH control.

Prevention points

• use DI water for final rinses and monitor metal ions

• neutralize aggressive chemistries before final rinse

• implement corrosion inhibitors or passivation where needed

• verify staining absence on worst-case test boards

ZESTRON’s analytical lab identifies staining chemistries and prescribes corrective actions.