Low Dielectric Constant—The Substrate of the Future

Low dielectric constant printed circuit board materials are becoming available. There are four or more materials that can produce boards with a dielectric constant of 28. This paper will discuss the electrical and system advantages of having a lower dielectric constant, and the advantages and disadvantages of each of the principal new materials. In particular, the use of lower dielectric to increase circuit density will be stressed, rather than the more usual expectation that the lower dielectric constant will be used to increase propagation velocity or reduce capacitance. The increase in circuit density will reduce the size of boards, and achieve the reduction in propagation delay even though the capacitance and characteristic impedance are unchanged.