Patent ID: 7611747

Claim:
A method of producing a multi-layer circuit board having a conductor circuit and an insulating material in which said insulating material is formed in a process comprising curing a curable composition layer, wherein said curable composition layer has a content of foreign matter, having particle sizes within the range of 30 to 50 μm, of 0 to 50 pieces per square centimeter; wherein the multi-layer circuit board has an electric resistance value of 10 8 Ω or more when the multi-layer circuit board is left standing at a DC voltage of 50V under a 120° C. saturated water vapor condition for 300 hours; wherein the insulating material includes a support and the curable composition layer is laminated on said support, and the insulating material has a charging voltage (absolute value) of not higher than 500 V; wherein said process of forming said insulating material comprises steps of forming a coating layer from a solution of a curable composition on said support, drying said coating layer and removing said support, and said step of drying said coating layer includes at least two zones comprising a first drying zone for conducting drying at 20 to 90° C. and a second drying zone for conducting drying at 70 to 150° C., a drying time of each of said drying zones is 40 to 150 seconds, and a temperature of said second drying zone is higher than that of said first drying zone; and wherein the method of producing the multi-layer circuit board comprising the steps of: laminating said insulating material on an internal layer board having a first electrically insulating layer and an electrically conducting circuit formed on a surface of said first electrically insulating layer in such a fashion that said curable composition layer comes into contact with said internal layer board; removing of said support from said curable resin composition layer is by peeling; curing said curable composition and forming a second electrically insulating layer; and laminating a conductor capable of forming an electrically conducting circuit on said second electrically insulating layer.