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Glass fibres are nothing new; the ancient Egyptians reportedly drew coarse fibres from heat softened glass. Modern usage, however, began in the 1930s with the founding of the Owens-Corning Fiberglas Corporation and the granting in 1938 of a patent covering their commercial manufacturing process.
Fibres exhibit markedly different properties to those of their bulk parent materials. Glass fibres can exhibit tensile strengths up to 5 GPa, which is around 100x higher than that of bulk glass, the difference being attributable to the reduction of the effect of surface defects, the control of which remains an important performance parameter.
The use of woven glass fibres in PCB substrates dates back to the 1960s where they were used as a high performance replacement for paper reinforcements. Woven glass fibre provided an ideal reinforcement to complement the properties of epoxy resin systems which were being rapidly deployed in electronics by adding high tensile strength and dimensional stability to the composite material forming the substrate.
Glass fibres brought not only the properties of high tensile strength and dimensional stability but also high thermal resistance, good chemical resistance, insensitivity to moisture and of course that of being a good electrical insulator.
The process of glass fibre production remained largely unchanged over 50 years, however there have been a number of recent important developments that have enabled substrates made with woven glass fabrics to adapt to the changing requirements of circuit design. In particular changes have been necessary to accommodate microvia technology requirements, improving CAF (conductive anodic filamentation) requirements and very importantly to extending the usable frequency range of glass reinforced substrates. Read the full article here.Editor's Note: This article originally appeared in the March 2014 issue of The PCB Magazine.
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