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Method for low-k dielectric materials for printed circuit board manufacturing

IP.com Disclosure Number: IPCOM000007146D
Publication Date: 2002-Feb-27
Document File: 3 page(s) / 44K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for low-k dielectric materials for printed circuit board (PCB) manufacturing. Benefits include improved performance.

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Method for low-k dielectric materials for printed circuit board manufacturing

Disclosed is amethod for low-k dielectric materials for printed circuit board (PCB) manufacturing. Benefits include improved performance.

Background

              As PCB signal frequencies increase, the capability to switch signals from digital high (1) to low (0) becomes limited by resistance-capacitance (RC) delays. They are caused by the capacitance between the switching trace and adjacent reference traces and/or planes. This capacitance is governed in part by the dielectric material used to electrically isolate the traces and planes.

              Capacitance is directly proportional to the dielectric constant, k, of the material. If k is great, then so is the capacitance therefore producing larger RC delays that limit the maximum signal frequency on the PCB. This problem becomes more pronounced for longer traces (larger surface area, A) and thinner PCB/dielectric layers, d, as the capacitance, C, is described by the equation, . The surface area, A, is given as the minimum overlapping areas between two metallic planes/traces (the product of the trace width, w, and trace length, L). The dielectric thickness is given by dimension, d (see Figure 1).

      Conventional PCB materials consist almost solely of FR-4 (epoxy-resin/woven glass cloth) dielectric layers and copper (Cu) conductors. At conventional and projected operating frequencies, the FR-4 dielectric constant is approximately 4.4-5.2. If the industry continues to use FR-4 in PCBs, then designers must resort to shorter signal traces and/or thicker dielectrics to reduce PCB capacitance and keep RC delays within reasonable performance limits.

General description

              The disclosed method is for the incorporation of low-k dielectric silica aerogels in PCB fabrication to enable high-speed signaling.

              Silica aerogels are commercially available materials. They have been used successfully as a low-k dielectric in silicon integrated circuit fabrication using copper metalization. This usage suggests that silica aerogels may be used in PCB fabrication as a low-k dielectric in place of...