Issue link: https://iconnect007.uberflip.com/i/834021
18 The PCB Magazine • June 2017 plates: two blind vias (or through-holes) con- nect to either copper plane layer creating a ca- pacitor. Some suppliers, such as 3M and Oak- Mitsui, offer epoxy-resin cores which provide high dielectric constants for applications such as MEMS microphones. Figure 3 illustrates the difference between a traditional capacitor and an embedded one. Note the smaller footprint when the capacitor is embedded under the IC. Drop-in Replacement In general, place the capacitive layer on 2/3 and on (n-2)/(n-1) as shown in Figure 4. For high layer counts, there may be more capaci- tive layers. There are three major brands of embedded capacitance material: • 3M: ECM (very thin layer of ceramic-filled epoxy) A BRIEF TUTORIAL ON EMBEDDED CAPACITORS Figure 3: Traditional capacitor (left) vs. embedded capacitor (right). Source: Oak-Mitsui Figure 4: Capacitance copper clad cores directly substitute the outer cores (green). Source: Oak-Mitsui