IEC 62047-31:2019

Overview

IEC 62047-31:2019 specifies a standardized four-point bending test method to measure the interfacial adhesion energy (critical energy release rate) of the weakest interface in layered MEMS materials. Based on fracture mechanics, the method applies to thin-film stacks deposited on semiconductor substrates (typically silicon) where the total thin-film thickness is much smaller than the supporting substrate. The test uses a pure bending moment applied to a machined test piece to initiate and propagate steady-state interfacial cracking; the interfacial adhesion energy is derived from the critical bending load.

Key topics and requirements

• Test principle: Introduce a pre-crack/notch, initiate a crack that reaches the weakest interface, then reload to measure the critical load for steady-state interfacial crack growth. Under pure bending the energy release rate is independent of crack length.
• Test piece geometry and fabrication:
  • Test pieces must be produced using the same fabrication process as the actual MEMS devices.
  • Geometry constraints: thickness of the test piece should be ~50× less than its length and width; length should be ~10× larger than width. Total thin-film thickness should be ~100× less than the supporting substrate thickness.
  • Pre-crack/notch may be made by diamond saw, laser ablation or chemical etching.
• Measurements and tolerances:
  • Dimensional measurements for span (L), width (b) and substrate thickness (h) must be accurate (error < ±5%).
  • The standard provides the fracture‑mechanics equation to compute energy release rate from the applied load (P), span (L), Young’s modulus (E), Poisson’s ratio (ν), width (b) and substrate thickness (h).
• Test apparatus and control:
  • Four-point bending fixture on a universal testing machine with load cell, actuator, linear guide and displacement sensor.
  • Loading pin diameter requirements (as specified in the standard), and instrumentation resolution requirements (load cell and displacement sensor resolutions < 1/100 of relevant values).
  • Loading speed range recommended for steady-state cracking and camera imaging at >10 Hz with ≥20× magnification for crack behavior recording.

Applications

• Thin-film adhesion characterization for MEMS components (sensors, actuators, RF-MEMS, micro-optics).
• Process qualification and materials selection during MEMS fabrication development.
• Failure analysis and reliability assessment where interfacial delamination is a root cause.
• Comparative testing of surface treatments, adhesion layers and deposition processes.

Who should use this standard

• MEMS designers and process engineers
• Reliability and failure‑analysis laboratories
• Materials scientists working on thin-film adhesion
• Semiconductor test labs and QA teams validating MEMS fabrication

Related standards

• Other parts of the IEC 62047 series (Semiconductor devices – Micro‑electromechanical devices)
• IEC 62047-2 and IEC 62047-3 are referenced for thickness measurement methods used in preparing and analyzing test pieces.

Keywords: IEC 62047-31, four-point bending, interfacial adhesion energy, layered MEMS materials, thin film adhesion, fracture mechanics test, MEMS reliability.