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48 DESIGN007 MAGAZINE I AUGUST 2022 A hybrid multilayer PCB is a circuit consists of several layers of different circuit materials. is is typically done for cost reasons, but there are other reasons as well. Sometimes using a combi- nation of different materials in a circuit stackup can assist with adjusting the overall coefficient of thermal expansion (CTE) of the circuit and that can be advantageous for circuit assembly and reliability. Additionally, there have been different materials combined for hybrid circuits with the intent of impacting thermal manage- ment, adjusting coupling, and customizing elec- trical properties for different layers within the circuit. Another good reason for combining dis- similar materials for a hybrid multilayer circuit is to improve circuit fabrication. Probably the most common reason for using hybrid multilayer PCBs is cost. Over the past many years, PCBs have been getting more com- plex. Today's circuits can be used to process many different types of electrical signals. e circuit may have high speed digital signals, RF signals, control signals, power planes, ground planes, etc. e high-speed digital and RF sig- nals will typically require a higher quality cir- cuit material that is formulated for very good and consistent electrical performance. e high frequency circuit materials, which are com- monly used for high-speed digital and RF applications, are generally higher in cost as compared to more standard FR-4 circuit materials. e control signals, power planes, and ground planes do not need the higher quality cir- cuit material and for the cir- cuit layers with those signals, they can use the cheaper FR-4 materials. Combining low-cost FR-4 materials with higher qual- ity high-frequency circuit materials is oen done with today's hybrid PCBs. ere are circuit fabrica- tion concerns which need to be addressed when combining dissimilar materials and most Benefits of High-Performance Hybrid Multilayer PCBs Lightning Speed Laminates Feature Column by John Coonrod, ROGERS CORPORATION 48 DESIGN007 MAGAZINE I AUGUST 2022