| 摘要 |
A thin film circuit board has an insulator layer and a conductor layer embedded in the insulator layer and supported in an undercut state by an insulator. The entire conductor layer, excluding the portion supported by the insulator, is surrounded by an insulator having a relatively low dielectric constant which in turn is surrounded by an insulator having a relatively high dielectric constant. The insulator portion that supports the conductor layer in the undercut state has a relatively high etching rate and is formed in a desired thickness on an insulator layer having a relatively low etching rate.
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