I. Why Is Professional Testing of Fiberglass Boards Necessary?
1.1 Applications and Quality Risks of Fiberglass Boards
Fiberglass boards (also known as FR-4 epoxy fiberglass boards, G10, G11, etc.) are laminated panels manufactured by bonding glass fiber cloth as the reinforcing material with an epoxy or phenolic resin matrix under high temperature and pressure. They possess excellent mechanical strength, electrical insulation, heat resistance, chemical corrosion resistance, and dimensional stability, and are widely used in: electronics and electrical engineering (PCB drilling spacers, insulating partitions, switchgear components), construction (fire-resistant partitions, wall insulation backing panels, ceiling panels), rail transit (interior fittings, seat back panels), wind turbine blades (webs, beam caps), chemical corrosion protection (storage tank linings, grating panels), and advertising and display (screen printing substrates, digital printing panels).
During production and use, key performance indicators of fiberglass boards—including flexural strength, impact strength, heat deflection temperature, flame retardancy rating (UL94 V0/V1 or GB 8624 B1/B2), water absorption, insulation resistance, and environmental performance (formaldehyde emission, heavy metal content)—directly determine their safety and service life. If quality control is not strictly enforced, this may lead to issues such as panel fracture under stress, the release of toxic fumes during combustion, deformation and insulation failure in humid environments, and indoor formaldehyde levels exceeding safety standards, posing health risks. Commissioning a third-party testing agency with CMA/CNAS accreditation to issue a report is a necessary step for factory acceptance, project acceptance, and export clearance.
1.2 Consequences of Failing to Meet Key Performance Criteria
- Insufficient bending strength/impact strength: Fracture under load, posing safety hazards when used in wind turbine blades or rail transit applications
- Failure to meet flame retardancy standards: Rapid combustion upon exposure to fire, failing to comply with building fire safety codes (GB 8624 Class B1 requirements)
- Low heat deflection temperature: Softens and deforms in high-temperature environments, leading to failure of electronic insulation components
- Excessively high water absorption: Dimensional changes in humid environments, resulting in reduced insulation performance
- Excessive formaldehyde emissions: Fiberglass boards used indoors pollute the air and pose health risks
- Insulation resistance too low: Risk of electrical leakage when used in electrical equipment
II. Scope of Glass Fiber Board Testing
Epoxy glass fiber boards (FR-4), phenolic fiberglass boards, G10 fiberglass boards, G11 fiberglass boards, flame-retardant fiberglass boards, halogen-free fiberglass boards, high-CTI fiberglass boards, high-TG fiberglass boards, high-thermal-conductivity fiberglass boards, insulating fiberglass boards, fiberglass-reinforced composite panels for construction, fiberglass boards for wind turbine blades, fiberglass boards for rail transit, chemical-resistant fiberglass grids, PCB drilling spacers, screen printing substrates, high-temperature-resistant fiberglass boards (above 250°C), anti-static fiberglass boards, and colored fiberglass boards.
III. Key Test Items and Standard References
3.1 Mechanical Properties
- Bending Strength: Determined using the three-point bending method in accordance with GB/T 9341 or ISO 178, expressed in MPa. The longitudinal bending strength of FR-4 fiberglass boards shall be ≥350 MPa, and the transverse bending strength shall be ≥300 MPa
- Impact Strength (Unnotched/Notched): Determined in accordance with GB/T 1043.1 or ISO 179 using the simply supported beam or cantilever beam method, expressed in kJ/m².
- Tensile Strength: Determined in accordance with GB/T 1040.2, applicable for stress analysis of fiberglass panels
- Compressive Strength: Determined in accordance with GB/T 1041, measuring compressive capacity in the thickness direction
- Interlaminar Shear Strength: Determined in accordance with JC/T 773 or ISO 14130, evaluating interlaminar bonding strength
3.2 Thermal Properties
- Heat Deflection Temperature (HDT): Determined in accordance with GB/T 1634 or ISO 75 under a load of 1.8 MPa or 0.45 MPa. FR-4 glass-fiber-reinforced board: HDT ≥ 130°C (1.8 MPa); high TG grade: ≥ 170°C
- Glass Transition Temperature (Tg): Determined by the DSC method in accordance with IPC-TM-650 2.4.25 or ISO 11357; reflects the resin’s heat resistance grade.
- Flame Retardancy Rating: Determined in accordance with UL 94 (vertical burning) or GB/T 2408. Common ratings: V-0 (self-extinguishing within 10 seconds), V-1, V-2; For building applications, in accordance with GB 8624-2012, Class B1 (flame-retardant) requires a flame spread index ≤ 120 W/s
- Oxygen Index: Determined in accordance with GB/T 2406 to measure the minimum oxygen concentration required to sustain combustion; flame-retardant grade ≥ 28%
- Thermal Decomposition Temperature: TGA method, used to evaluate long-term heat resistance
3.3 Electrical Properties
- Insulation Resistance: Determined in accordance with GB/T 1410 or IPC-TM-650 2.5.7, both at room temperature and after immersion; must be ≥10⁶ MΩ
- Dielectric Strength (Breakdown Voltage): Determined in accordance with GB/T 1408.1, in kV/mm; typical value for FR-4 is ≥20 kV/mm
- Dielectric Constant and Dielectric Loss Factor: Determined at 1 MHz in accordance with IPC-TM-650 2.5.5.9
- Arc Resistance: Evaluated in accordance with GB/T 1411
- Comparative Tracking Index (CTI): Evaluated in accordance with GB/T 4207 to assess surface resistance to tracking
3.4 Physical and Durability Properties
- Water Absorption: In accordance with GB/T 1034 or ISO 62, weigh after soaking in water at 23°C for 24 hours; required to be ≤0.1%–0.5% (depending on grade)
- Density: Determined in accordance with GB/T 1033 using the immersion method or geometric method
- Dimensional Stability: Determined in accordance with IPC-TM-650 2.2.4 as the percentage change in dimensions after heat treatment
- Chemical Resistance: Determined in accordance with ASTM D543 as the retention rate of properties after immersion in acids, alkalis, and solvents
- Damp Heat Aging: Insulation resistance and flexural strength are tested after treatment at 85°C/85% RH
3.5 Environmental Protection and Safety Performance
- Formaldehyde Emission: In accordance with GB 18580-2017, using the 1 m³ climate chamber method, the requirement for fiberglass boards for indoor use is ≤0.124 mg/m³ (Class E1)
- Heavy Metal Content: In accordance with GB/T 26125 or IEC 62321, testing for Pb, Hg, Cd, and Cr(VI)
- RoHS Compliance: Testing for six restricted substances
- REACH SVHC: Testing for Substances of Very High Concern
- Total Volatile Organic Compounds (TVOC): In accordance with GB/T 18883, for interior-use panels
IV. What Qualifications Must Testing Laboratories Possess?
The Significance of CMA/CNAS
CMA (Accreditation of Inspection and Testing Laboratories): A statutory qualification in China; test reports can be used for forensic evaluation, engineering acceptance, and product quality disputes.
CNAS (China National Accreditation Service for Conformity Assessment): International mutual recognition; reports are accepted in ILAC member countries (including the EU, the U.S., Japan, and Southeast Asia).
V. How Do Common Testing Instruments Ensure Data Accuracy?
Universal Testing Machine: Flexural strength, tensile strength, interlaminar shear strength; accuracy class 0.5
Simply Supported Beam/Cantilever Beam Impact Tester: Impact strength
Thermal Deformation and Vicat Softening Point Tester: GB/T 1634, oil bath heating; accuracy ±0.1°C
Differential Scanning Calorimeter (DSC): Glass Transition Temperature (Tg)
Thermogravimetric Analyzer (TGA): Thermal decomposition temperature, filler content
Vertical Burning Tester: UL 94, timing accuracy 0.1 s
Oxygen Index Tester: GB/T 2406
High-Resistance Meter/Insulation Resistance Tester: Surface resistance, volume resistance
Dielectric Strength Tester: Up to 100 kV
LCR Bridge: Dielectric constant, Dielectric loss
Constant Temperature and Humidity Chamber: Humidity and heat aging
1 m³ Climate Chamber: Formaldehyde emission
Gas Chromatography-Mass Spectrometry (GC-MS): VOCs, RoHS
Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES): Heavy metals
All equipment is calibrated regularly and operates under an internal quality control system.
VI. Frequently Asked Questions (FAQ)
Q1: How many samples are required for glass fiber board testing?
A: Generally, 2–3 complete boards measuring no less than 200 mm × 200 mm are required. Destructive tests (bending, impact, flame retardancy) will consume the samples, so please keep backups. Please specify the thickness, grade (e.g., FR-4, G10), and required flame retardancy rating.
Q2: How is the flame retardancy rating of fiberglass boards tested? What is the difference between Class B1 and UL 94 V-0?
A: UL 94 V-0 is a vertical burning test requiring self-extinguishment within 10 seconds and no dripping that ignites cotton; GB 8624 Class B1 is a flame-retardant rating for building materials, which, in addition to combustion testing, also requires testing for smoke toxicity and heat release. The two standards apply to different scenarios: UL 94 is used for electronic insulation, while GB 8624 is used for construction.
Q3: What are the possible reasons for a glass fiber board failing the bending strength test?
A: ① Insufficient number of glass fiber cloth layers or uneven layering; ② Incomplete resin curing; ③ Improper pressing pressure or temperature; ④ Incorrect test direction (longitudinal and transverse directions must be distinguished). When testing according to GB/T 9341, the direction must be specified.
Q4: What tests are required for exporting fiberglass boards to the EU?
A: RoHS 2.0 (six restricted substances) and REACH SVHC. Electronics-grade products also require UL 94 flame retardancy certification; construction-grade products must comply with the EN 13501-1 fire resistance class. CNAS-accredited institutions can issue reports in both Chinese and English.
Q5: How to choose a reliable glass fiber board testing laboratory?
A: ① CMA + CNAS accreditation; ② Equipped with universal testing machines, heat deflection testers, and flame retardancy testers; ③ Familiarity with GB, UL, ISO, and ASTM standards; ④ Capability to perform failure analysis (delamination, blistering, etc.); ⑤ Reports in both Chinese and English. Beijing Qingxi Technology Research Institute possesses these advantages.
VII. Summary
The quality of fiberglass boards directly impacts electrical and electronic safety, building fire resistance, and indoor air quality. Every parameter—from flexural strength and heat deflection temperature to flame retardancy ratings and formaldehyde emission levels—must be strictly controlled. It is recommended to select an institution that holds both CMA and CNAS accreditation, operates a judicial appraisal institute, and maintains a high integrity rating (such as Beijing Qingxi Technology Research Institute). Prior to testing, the type of fiberglass board (FR-4/G10/construction grade), applicable standards (GB, UL, ISO), and the intended use of the report (factory acceptance, export clearance, or project acceptance) should be clearly defined.
The summary of the above testing items and standards is provided as a reference for entities involved in the production, processing, procurement, and use of fiberglass boards when commissioning testing.