Closed Plain-Weave Glass Yarn Fabrics, Uncoated

Standard E-glass PCB fabrics (typically 9–11 micron filament diameter, uncolored, width over 30 cm) generally fall under the mechanically bonded, uncolored, wide-format lines within 701963. However, the specific 10-digit line depends on filament diameter and whether the fabric is silica-based. Importers should obtain mill certifications confirming filament diameter and silica content, and consider a binding ruling for high-volume PCB substrate imports given the multiple available lines.

Fabrics woven from silica filaments with silica content exceeding 93% (line 7019634030) are high-purity quartz or fused-silica fabrics used in aerospace radomes and high-temperature electrical insulation — distinct from standard E-glass or S-glass fabrics. The ≤93% silica line (7019634060) captures lower-purity specialty glasses. Chemical analysis documentation from the manufacturer is the standard method for supporting the correct classification.