Acceptable ROSE levels explained
ROSE stands for resistivity of solvent extract and measures extractable ionic contamination, often expressed as micrograms of sodium chloride equivalent per square centimeter. It provides a rapid index for cleanliness and process control. ROSE is useful for trend monitoring and identifying when cleaning processes need adjustment.
ROSE alone does not identify specific ions or predict all failure modes, but it is a practical production metric. Many high-reliability manufacturers use ROSE thresholds to gate PCBs before final assembly or conformal coating. ZESTRON recommends combining ROSE with ion chromatography for root cause analysis and SIR testing for electrical risk assessment.
ROSE testing methodology
ROSE testing steps:
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Select representative locations on the PCB for sampling.
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Extract residues with a defined solvent and agitation method.
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Measure the change in solvent resistivity or conductivity.
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Convert conductivity change to micrograms NaCl equivalent per square centimeter.
Consistency in sample area, solvent, and extraction time is critical. ZESTRON offers standardized ROSE protocols and training to ensure reproducible results.
Threshold levels for PCBs
Common threshold guidance:
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general commercial electronics: <1.5 micrograms NaCl eq/cm2
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high-reliability electronics: <0.5 to 1.0 micrograms NaCl eq/cm2
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high-voltage or critical safety systems: lower thresholds and additional testing
These are starting points; acceptable levels depend on application, operating environment, applied bias, and coating strategy. ZESTRON helps customers define product-specific thresholds and implements process control measures.