| 摘要 |
PROBLEM TO BE SOLVED: To provide an electric circuit board which contains a plurality of ultra-fine bubbles in the electric circuit board, is low in a dielectric constant, and in particular is useful in a high frequency region. SOLUTION: An electric circuit board has a plurality of ultra-fine bubbles which are formed by a supercritical fluid inside the electric circuit board and are each independent. Preferably, the total volume rate of the ultra-fine bubbles is 20 to 69% based on all volume of the electric circuit board, and a maximum bubble diameter of the ultra-fine bubbles in 20μm or less. Further, the supercritical fluid is a supercritical carbon dioxide. Further, the electric circuit substrate is obtained by impregnating a thermosetting resin into a sheet made of at least one kind selected from a pulp fiber, a glass fiber, a liquid crystal high polymer fiber and a heat-resistant organic fiber to create a prepreg, and by press-forming the prepreg. COPYRIGHT: (C)2003,JPO
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