Overview
IEC 61747-40-2:2015 specifies a mechanical testing procedure for display cover glass used in mobile electronic devices, focusing on the measurement of as‑received edge strength using a uni‑axial four‑point bend (4‑point) test. The standard defines test setup, apparatus functions, specimen handling and reporting so manufacturers, test labs and designers can generate comparable strength and statistical data for cover glass used in flat‑panel displays.
Key topics and technical requirements
- Test principle: Uni‑axial flexure produced by forcing two parallel load bars through a specimen supported on two parallel support bars (four‑point bend). Load at fracture is measured and converted to strength (Clause 4, Clause 7).
- Specimen & sample definitions: Distinguishes individual specimen and sample for statistical treatment; typical specimen dimensions described (width 44–60 mm, length 60–110 mm, thickness 0.55–2.0 mm).
- Apparatus: Requirements for a controlled testing frame with load cell, displacement detection and controller (Clause 5). Controller functions include preset traverse rates, stop-on-fracture and emergency stop.
- Fixture details & protection: Surfaces contacting load bars are covered with polymeric adhesive tape to preserve fracture surfaces and reduce fragmentation; support rods covered with PTFE tape or rollers to minimize contact damage and friction.
- Environment & pre‑conditioning: Tests performed per the environment in IEC 61747-40-1 with specimens stored in that environment for at least four hours prior to testing (Clause 5.1).
- Safety: Identifies hazards - broken glass, flying debris, crush hazards - and procedural safeguards (Clause 6.1).
- Calculations & statistics: Strength calculations and statistical treatment are defined (Clause 7). Weibull analysis (IEC 61649) is cited for statistical characterization and plotting (example Weibull plot provided).
- Reporting: Required test data, specimen details and statistical outputs to be reported (Clauses 8 and 9).
Practical applications
- Validation of cover glass mechanical performance for smartphone, tablet and other mobile device displays.
- Incoming quality control and production testing of tempered or ion‑exchanged cover glass.
- Comparative material evaluation and R&D (e.g., assessing ion‑exchange strengthening effects).
- Failure analysis and contractual specifications where edge strength and fracture statistics are required.
- Certification and supplier qualification by test laboratories and QA teams.
Who uses this standard
- Display module manufacturers and OEMs
- Cover glass and substrate suppliers
- Materials and mechanical test laboratories
- Quality assurance, reliability and product safety engineers
- R&D teams developing strengthened glass processes
Related standards
- IEC 61747-40-1 - Guidelines and environmental pre‑conditioning for cover glass mechanical testing.
- IEC 61649:2008 - Weibull analysis for statistical treatment of brittle fracture data.
Keywords: IEC 61747-40-2, four-point bend, uni-axial flexural strength, cover glass testing, mobile device displays, edge strength, Weibull analysis, testing frame, PTFE, specimen dimensions.
Open preview (PDF)Liquid crystal display devices - Part 40-2: Mechanical testing of display cover glass for mobile devices - Uni-axial flexural strength (4-point bend)
