Embedded Capacitors in PCBs for low impedance

Embedded Capacitor – Power Planes PCB with-built in capacitance

A reliable capacitor can be formed in a PCB multi-layer board using a composition of dielectric materials. The interconnections of the dielectric material withing the multi-layer PCB package forms embedded capacitance. As a result, this method accommodates frequencies above 1 Ghz. Frequencies that discrete surface mounted capacitors are ineffective at. Furthermore, this method reduces surface mounted components. Therefore offering a smaller final package size.

A capacitance PCB can be built with a thickness below 0.35mm . Using three 50um prepreg layers, two 12 um capacitance dielectrics and 18 um copper foil.

Advantages of Embedded PCB Capacitors

Surface mounted discrete capacitors are ineffective above 1 GHz
Built in decoupling
Minimal ESR
Improved EMI
PCB embedded capacitors have Low impedance and high capacitance at high frequencies
Impedance is more critical than capacitance at high frequencies
Low power bus noise can result in reduced radiated emission

Dielectric material choices

Dupont and 3M offer dielectric laminate. See the below links for datasheets from their respective websites. Contact us to explore how you can effectively incorporate this method into your project.

Embedded capacitance layer in a multi-layer build using blind via’s

Capacitance layer in a multi-layer PCB using a blind via

Layer composition for capacitance layer using blind via’s

The list details the layers that appear in the above illustration.

Final plating 18um
Second plating 18um
Base copper 18um
Core 100um
Base copper 18um
Capacitance layer 12um
Base copper 18um
Second plating 18um
Prepreg 100um
Second plating 18um
Base copper 18um
Capacitance layer 12um
Base copper 18um
Core 100um
Base copper 18um
Second plating 18um
Final plating 18um

Final PCB thickness: 0.44 mm

Embedded capacitance layer in a multi-layer build without via’s

Embedded Capacitance layer in a multi-layer PCB with no blind via

Simple power plane example:

A to -12V
C to +5 V
B not to any power plane

Layer composition for capacitance layer without via’s