印制板安全标准 / Standard for Safety of Printed Wiring Boards

This standard covers requirements for printed wiring boards used as components in electrical equipment. It addresses flammability, electrical insulation, mechanical strength, and thermal performance of rigid and flexible printed wiring boards.

Materials used shall comply with applicable UL recognized material specifications. All test specimens shall be representative of production. Marking shall include manufacturer identification, type designation, and UL recognition mark. Construction review per applicable end-product standards.

Specimens shall meet V-0, V-1, or V-2 rating per UL 94 Vertical Burning Test. Minimum acceptable rating is V-1 for most applications. Test five specimens at specified thickness. Afterflame time t1 and t2, afterglow time t3 recorded. No flaming drips allowed for V-0 and V-1 ratings.

Apply test voltage between conductive layers and surface conductors. Test voltage depends on spacing and application class. For working voltage up to 250V, test at 1000V AC for 60 seconds. No breakdown or flashover permitted. Humidity preconditioning at 48 hours in 93% RH may be required.

Measure insulation resistance between adjacent conductors after humidity conditioning. Minimum 100 MΩ at 500V DC after 96 hours at 40°C/93% RH. Measurement taken within 5 minutes of removal from chamber. Surface and volume insulation resistance both evaluated.

Float test at 288°C ± 5°C for 10 seconds. No delamination, blistering, or conductor lifting. Solder mask shall not peel or discolor beyond acceptable limits. Plated through-hole integrity maintained. Tested both as-received and after moisture conditioning.

Measure dimensional change after processing cycles including etching, soldering simulation, and thermal cycling. Maximum dimensional change 0.025 mm/mm for rigid boards. Flexible circuits maximum 0.05 mm/mm. Measurements at minimum four reference points.

Minimum peel strength 0.7 N/mm for copper foil ≥ 35 µm. Tested at 90° peel angle, 50 mm/min crosshead speed. After thermal stress conditioning, minimum 0.5 N/mm. Both lengthwise and crosswise grain directions tested. Report average of three specimens.

Subject specimens to temperature cycling between -55°C and +125°C. Dwell time 15 minutes at each extreme. Ramp rate 10°C/min minimum. Complete 100 cycles minimum. Inspect for cracking, delamination, and PTH barrel cracks after cycling. Electrical continuity verified throughout.

Each board shall be permanently marked with manufacturer name or trademark, type designation, date code, and UL recognition symbol. Marking shall survive normal cleaning and soldering processes. Label adhesion tested per UL 969. Traceability to production lot required.