Material Specification
Industry requirements for the woven glass fabric used in the construction of base materials are established by this consensus document. Compliance with ipc-4412 ensures that the reinforcement used in a laminate meets specific standards for weight, thickness and weave consistency. These properties are fundamental to the mechanical strength and electrical stability of the finished printed board.
The standard classifies fabrics by style numbers that correspond to specific yarn counts and filament diameters.
Fabric Classification
Selection of a glass style influences the resin content and the overall thickness of a single ply of prepreg. Thinner fabrics allow for the creation of thin multilayer boards but may be more susceptible to warping during the lamination process. Heavier weaves provide better dimensional stability but can introduce glass-weave skew in high-speed signals.
Fabricators must select the appropriate style to balance the electrical needs of the circuit with the mechanical requirements of the assembly. The document provides the tolerances for defects like knots or broken filaments that could compromise the dielectric barrier.
Acceptance Quality
Physical testing includes the measurement of the breaking strength of the fabric in both the warp and fill directions. These values confirm that the laminate will survive the pressures of the hydraulic press.
