Overview
ISO 21164:2018 - Metallic and other inorganic coatings - specifies standardized test methods for measuring adhesion of DC magnetron sputtered silver coatings used for electrical, electronic, optical and other engineering applications. It covers adhesion assessment on sheets and flat objects (not screw threads, strip or wire in non‑fabricated form) and defines procedural requirements for several mechanical and thermal tests as well as nano‑scale scratch testing.
Key topics and technical requirements
- Scope and purchaser responsibilities
- Applies to sputtered silver coatings serving non‑decorative (engineering) functions.
- The purchaser must specify basis‑metal condition, finish, surface roughness, thickness and adhesion test requirements.
- Mechanical adhesion tests
- Burnishing: rapid, firm rubbing (e.g., agate spatula) for up to 15 s; not applicable for coatings >10 µm.
- Barrel burnishing: wet burnish (about 40 min) in a rubber‑lined barrel (≈250 mm, 25 r/min); inspect for blistering/peeling.
- Peel test: use the method referenced in ISO 4521.
- Bending test: bend specimen to a 4 mm radius through 90° and back three times; coating must not detach.
- Thermal shock: heat at 200–300 °C for ~30 min then quench in ambient water; inspect for blistering/detachment.
- Nano scratch test
- Intended for sputtered silver thickness ≈0.5–1.5 µm on steel or copper substrates (qualitative results).
- Uses a nano scratch tester with a sphero‑conical diamond indenter (≈2 µm radius).
- Progressive linear loading example: start 1 mN → final 100 mN, loading rate ≤100 mN/min.
- Record acoustic emission, coefficient of friction, frictional force and penetration depth; report environmental conditions, coating/substrate details, indenter radius, speeds and loads.
- Inspection and evaluation
- Low‑magnification microscopy is used to detect blistering, peeling, micro‑cracks or exfoliation following tests.
Practical applications
- Ensures reliable electrical/optical performance where sputtered silver coatings provide conductivity, reflectivity or contact surfaces.
- Commonly applied in component qualification, incoming inspection, production quality control and failure analysis for connectors, contacts, optical mirrors and electronic assemblies.
Who should use this standard
- Coating manufacturers, contract sputtering shops and plating houses
- Materials and surface‑engineering engineers
- Quality assurance, test laboratories and purchasers specifying coated components
Related standards
- ISO 4521 - Electrodeposited silver coatings: specification and test methods (referenced for burnishing/peel)
- ISO 2064 - Coating thickness measurement conventions
- ISO 2080 - Surface treatment vocabulary
Keywords: ISO 21164:2018, DC magnetron sputtered silver coatings, coating adhesion test, nano scratch test, burnishing, bending test, thermal shock, barrel burnishing.