Overview
ISO 16525-2:2014 specifies standardized test methods for isotropic electrically conductive adhesives (ICA) used in wiring, die attach and surface assembly of printed circuit boards in electronic devices. Part 2 focuses on the determination of electrical characteristics relevant to electronic assemblies - primarily volume resistivity and interfacial contact resistivity - using defined test circuit boards and measurement procedures.
Key topics and requirements
- Scope and purpose: Evaluates electrical behavior of paste-type ICAs (heat-curing resin with dispersed metal particles) when used to interconnect electronic circuits.
- Measured quantities:
- Volume resistivity (ρ) - electrical resistance of the adhesive as a function of cross-sectional area/length; reported in Ω·m (or Ω·mm in test formula).
- Interfacial contact resistivity (ρi) - resistance generated at the interface between the adhesive and the adherend (electrode), expressed per unit area.
- Measurement principles:
- Use of a four-probe method (two current terminals, two voltage terminals) and specially patterned test circuit boards to separate bulk resistivity from interfacial effects.
- Volume resistivity calculated from applied current, measured voltage drop and adhesive geometry.
- Interfacial resistivity determined by measuring resistances at multiple voltage taps along adhesive patterns and extrapolating the intercept via least-squares regression.
- Test specimen preparation:
- Screen-printing or masked application of ICA onto circuit substrates; recommended adhesive thickness ~0.10–0.15 mm.
- Requirements for electrode plating/anti-oxidants and soldered wiring to ensure low lead resistance (≤ 0.01 Ω).
- Test conditions:
- Standard atmosphere: (25 ± 5) °C and (50 ± 10) % RH (ISO 554).
- “Dry circuit” measurement constraints to avoid microstructure breakdown (limits noted for current/voltage).
- Reporting: Detailed test report content is specified - adhesive identification, substrate/circuit dimensions, curing conditions, measurement conditions, and calculation parameters.
Applications and who uses it
- Adhesive manufacturers - to characterize and certify electrical performance of ICAs.
- Electronics OEMs and PCB assemblers - to select adhesives for wiring, die-attach and surface mount interconnects.
- Test laboratories and quality engineers - for acceptance testing, comparison of formulations and failure analysis.
- Materials and reliability engineers - to assess interface resistance contributions and to optimize assembly processes.
Related standards
- ISO 16525 series (Parts 1–9) - general methods, heat-transfer, shear tests, environmental tests, signal transmission, etc.
- Normative references cited: ISO 472, ISO 554, ISO 80000-1, IEC 60468, IEC 61249-2-7, EN 923, ASTM B539-02.
Keywords: ISO 16525-2, isotropic electrically conductive adhesives, volume resistivity, interfacial contact resistivity, test methods, electronic assemblies, PCB, four-probe method.
Open preview (PDF)Adhesives — Test methods for isotropic electrically conductive adhesives — Part 2: Determination of electrical characteristics for use in electronic assemblies
