Surface insulation resistance measurements

Measuring the reliability of the circuit

When electronics operate in humid environments, contamination can occur on the surface of the assembly and conductive electrochemical corrosion products (dendrites) can form between adjacent conductors.  During surface insulation resistance (SIR) measurement, the electrical resistance between metallic conductors on the substrate surface is monitored when a voltage is applied. This indicates the propensity of the system to form these corrosion products and gives a measure of the reliability of the circuit assembly in the field.

Our equipment can detect leakage currents approaching pA, and can log resistance values every 10-20 minutes over test periods ranging from a few hours to several months. In practice, we create test coupons that are representative of geometries found in production printed circuit assemblies. They are manufactured using supplier-specific process chemistries, such as flux, paste, cleaners and resists. NPL has SIR measurement facilities for up to 512 channels per run with bias and measurement voltages from 5 to 1000V.

Our services and capabilities include:

• Solder paste assessments
• Conformal coating compatibility with no-clean solder pastes
• Solder mask evaluations
• PCB surface finish and solder paste compatibility
• Conformal coating protection efficiency
• Assembly process evaluations
• Nano-coating assessment
• Dew testing
• Cleaning process reviews
• High voltage solder mask performance

Learn more about our capabilities

SIR, CAF and condensation testing for electronic assemblies
The advantages of using SIR (and CAF) testing to evaluate assembly processes and materials. Test vehicle design, how to conduct testing and analyse the results. Watch webinar  View slides

Development of SIR measurements for electronic assemblies
Starting with the historic international standard for SIR testing (ISO 9455) and evolving this to reflect modern soldering processes and instrumentation capability. Download the report

Test method for conformal coating protection performance of electronic assemblies in harsh environments
A test method for assessing conformal coating protection performance using the SIR technique. Download the report

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