Flexible laminate board, process for manufacture of the board, and flexible print wiring board

Abstract

A process for production of a flexible laminated sheet having one or more laminated bodies each provided with a metal foil formed on one side of a resin film. The process includes coating a varnish containing a polyamic acid and a solvent onto the metal foil, holding the coated film, drying in which at least a portion of the solvent in the varnish is removed to form a layer composed of a resin composition, and forming the resin in which the layer composed of the resin composition is heated to form a resin film containing a polyimide resin. The conditions for each step from the coating up to the resin film-forming are adjusted based on a target for the content of metal elements in the resin film.

1 . A process for production of a flexible laminated sheet having at least one laminated body, each laminated body being provided with a metal foil formed on one side of a resin film, the process comprising:
 a coating step in which a varnish containing a polyamic acid and a solvent, for forming said resin film of each laminated body, is coated onto the metal foil to form a coated film;   a drying step in which the solvent in the varnish is removed to a proportion of 1-60 wt % of the total, to form a resin composition layer from the varnish; and   a resin film-forming step in which the resin composition layer is heated to 250-550° C. under a reducing atmosphere to form said resin film, said resin film containing a polyimide resin.   
     
     
         2 . A production process according to  claim 1 , wherein the reducing atmosphere is formed by a mixed gas composed of nitrogen gas and hydrogen gas at between 0.1 vol % and 4 vol % of the total. 
     
     
         3 . A production process according to  claim 1 , wherein the solvent is removed by heating the varnish to 100-170° C. in the drying step. 
     
     
         4 . A production process according to  claim 1 , wherein the metal foil is a copper foil. 
     
     
         5 . A production process according to  claim 1 , wherein a concentration of the polyamide acid in the varnish is 8-40%, and the viscosity of the varnish is 1-40 Pa·s. 
     
     
         6 . A production process according to  claim 1 , wherein in said drying step, the solvent in the varnish is removed to a proportion of 25-45 wt %. 
     
     
         7 . A production process according to  claim 1 , wherein in the coating step, the varnish is coated in contact with the metal foil. 
     
     
         8 . A production process according to  claim 1 , wherein in the flexible laminated sheet produced, a content of metal elements in the resin film is no greater than 5 wt %. 
     
     
         9 . A production process according to  claim 1 , wherein the resin film-forming step is performed after the drying step. 
     
     
         10 . A production process according to  claim 1 , wherein the drying step is performed under a reduced pressure atmosphere or a reducing atmosphere.