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MAY 2022 I DESIGN007 MAGAZINE 79 UVCLX coating with 75% bio-organic content from renewable sources, which might solve your requirements more sufficiently. I hope my column has been useful and of course, we are always happy to help and advise. ESIGN007 Phil Kinner is the global busi- ness and technical director of conformal coatings at Electro- lube. To read past columns or contact Kinner, click here. Download your copy of Electro- lube's book, The Printed Circuit Assembler's Guide to… Conformal Coatings for Harsh Environments, and watch the micro webinar series "Coatings Uncoated!" Evolution of Glass Fabric Materials such as cotton, paper and glass mat were used before woven glass fiber started mass production and became the dominant fabric used for PCB composites. Early PCBs were low layer count and used a heavy glass weave, such as 7628 or 7629, as the primary component. Since the mid '70s, glass manufacturers have introduced new and thinner glass weaves to enable ultra-thin laminate and substrate materials. Woven glass fabric is impregnated with resin and when fully cured or dried, pro- vides the mechanical, chemical, and electri- cal properties for rigid printed circuit appli- cations. The characteristics and properties of glass fiber and fabrics are defined by IPC-4412 "Specification for Finished Fabric Woven from E-Glass for Printed Boards." There are compositions of glass fibers that will also be discussed including the next generation of lower-Dk glass fabrics now in development. Glass is a mix of several inorganic minerals which are melted in a furnace. Temperatures are maintained above 1000°C so the com- ponents can be melted and homogenized. The molten glass is then drawn from plati- num bushings to form fibers which are collected to make a yarn which is collected onto a bobbin. These bobbins are then processed into an elec- tronics fabric designed to be used in production of laminate and prepreg. Figure 2.1 is a review of the whole process from raw material to the fiber and process to be woven as glass cloth. Download this book to continue reading. BOOK EXCERPT The Printed Circuit Designer's Guide to... High Performance Materials Chapter 2: Glass Fabric arise as it may prove difficult to dissipate heat away from thickly coated components. It is good to remember that above a certain thickness, which does vary according to the material being applied, any increase is likely to deliver diminishing returns. Get the advice of a reputable supplier; they have laboured hard to establish optimum coating thicknesses for their products in all kinds of operating envi- ronments. ere's a lot to consider for a suc- cessful conformal coating process. Getting it wrong could compromise the reliability of an electronic assembly, shorten its life expec- tancy, or even prove critical. First and fore- most, seek some expert advice as there are new coating materials, such as our new bio-based Figure 2.1: Glass fiber/glass cloth manufacturing process. (Source: Taiwan Glass)

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