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96 The PCB Magazine • March 2014 USING FLEX IN HIGH-SPEED APPLICATIONS continues ing the differences between the materials can help both fabricators and designers better uti- lize flex circuits to meet their goals. • To utilize flex in high-speed and high fre- quency applications, the effect of the Kapton, adhesive must be understood in the same way that the effects of the glass and resin must be known for rigid designs. • Not all Kapton are created equal. Ad- vanced, high modulus Kapton has low loss and low dispersion compared to Kapton used for coverlay. • As high-speed circuits get thinner, the more it makes sense to utilize flexible circuits in these designs because of the inherent properties of flex materials. PCB References 1. Specification Tree of Standards organized by IPC. 2. Oliver, G and Coonrod, J. Practical Mea- surements of Dielectric and Loss of PCB Materi- als at High Frequencies, DesignCon 2014. 3. More information on the composite ma- terials can be found at www.pyralux.com/tk. Figure 7: comparison of high-speed flex to high-speed rigid microstrip lines. glenn oliver is a senior engineer at dupont electronics and communications.