High Voltage Characteristics of Embedded Decoupling Capacitors

摘要

Printed wiring board layers with dielectric constants much greater than typical FR-4 (K~~4.5) can be made by creating, polymer-ceramic composites or dielectric films that can be laminated between or deposited on a copper core. This core can then be integrated as part of a multilayer printed wiring board. Three commercial core materials for Embedded Decoupling Capacitors (EDC) are now available and can provide up to 40x the capacitance per unit area of FR-4. These layers can be used to replace or supplement discrete MLCs used for decoupling. Although the EDC capacitors will almost always be used at low voltages of 1.3 to 15 volts, the boards are often tested at higher voltages. Breakdown tests at 500 volts are commonly used in the electronics industry. For this reason we have characterized some high voltage parameters of the EDC capacitors. A high voltage, low frequency signal is applied to the samples and the charge versus voltage characteristics are measured and stored digitally. The applied voltage was a triangle wave; the peak amplitude for our tests was 100volts, 500volts or 1000 volts. The period of the test signal was either 0.1, 1 or 10 seconds. We will also report on measurements of leakage currents and breakdown strength for the various types of EDC materials. All of the EDC higher dielectric constant materials showed nonlinear high field behavior. This response is characteristic of polymer/ceramic composites and is due to trapped charge electret effects at the particle/polymer interfaces.