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June 2017 • The PCB Magazine 19 • DuPont Interra: HK04J (dielectric core composed exclusively of polyimide) • Oak-Mitsui: FaradFlex (epoxy or other type of resin bonded to a high-performance polymer film) Advantages of Using Embedded Materials There are many benefits to incorporating embedded capacitors (as well as other embed- ded components) into a design. Besides me- chanical or design benefits there are also electri- cal advantages. Mechanical/Design Benefits One of the major reasons to embed is to save space on outer layers; there will be fewer com- ponents to go on the surface of the multilay- er. All decoupling capacitors can be eliminat- ed (from the surface) as well as perhaps greater than 40% of bypass capacitors. Saving real estate can result in a smaller size PCB which decreases weight and (possibly) thickness. This savings in board real estate could be utilized in other ways also; perhaps more ca- pability can be designed in and extra layers be added without increasing overall thickness. But with possible layer count reduction (and hence a thinner overall panel), the PTH aspect ra- tio will be reduced and the fewer surface compo- nents mean fewer PTH connections overall. Cir- cuit routing capability will be improved. By solv- ing noise issues early in the design cycle, not only is the cycle most likely shortened but specs can be simpler. All these benefits point to lower cost. Electrical Benefits Regardless of savings in materials, real es- tate, design turnaround time and the other benefits mentioned above, there are often oth- er factors that make embedded capacitance a good approach. Chief among these is improved reliability with fewer connections overall. But there are numerous electrical design advantages that should also be recognized. These include: • Significantly reduced power buss noise • Decreased inductance • Lower power-to-ground noise • Reduced simultaneous switching noise • Reduced interference from digital circuits to analog/RF circuits in mixed signal applications • Reduced impedance and modal resonance • Shorter routing path deliveries instantaneous charge when needed • Decreased need for EMC measures such as metal shells, tapes, etc. • No glass bundles, therefore no conductive anodic filament (CAF) concerns • Improved trace routing capability Applications The improved tolerance, temperature volt- age and frequency characteristics realized with embedded capacitors make these PCBs suitable for a wide range of applications, including: • Routers • Servers • Telecom • SSD storage • MEMS microphones • Commercial • Wearable electronics • Consumer electronics • Organic capacitor chip diplexers • RF filters • Super computers • Test and measurement equipment • Medical applications • Military/aerospace Two applications are shown in Figures 5 and 6. A BRIEF TUTORIAL ON EMBEDDED CAPACITORS Figure 5: MEMS microphone. Source: 3M.