| 摘要 |
PROBLEM TO BE SOLVED: To provide a porous resin layer, which has a high heat resistance, a high dimensional stability and high insulation characteristics and moreover, has uniform and microscopic bubbles, a photosensitive resin composition layer for obtaining the porous resin layer, a circuit board having such a porous resin layer as an insulating layer and a suspension substrate with a circuit. SOLUTION: A polyamic acid resin 4, a photosensitizer, a dispersive compound 3 capable of being dispersed in the resin 4, and a solvent are made to be contained as a photosensitive resin composition on a circuit board 1. By removing the solvent from this composition layer 2, a state that the compound 3 is dispersed in the resin 4 is formed, then the compound 3 is removed from the composition layer 2 to bring the composition layer 2 into a porous state and after that, the composition layer 2 is cured to obtain a porous resin layer. The obtained porous resin layer is low in a dielectric constant. Therefore, if the porous resin layer is used as an insulating layer 6 on the circuit board 1, the high-frequency characteristics of the circuit board 1 can be raised. |
