Transfer sheet and wiring board using the same, and method of manufacturing the same

Abstract

A transfer sheet of the present invention includes a resin film having a glass transition temperature of not lower than 60° C., a silicone resin layer formed on the resin film, and a metal wiring pattern formed on the silicone resin layer. The metal wiring pattern has an exposed face that forms a roughened face, and the roughened face has a ten-point average surface roughness (Rz) of 2 μm or more, while a face of the wiring pattern, which is in contact with the silicone resin layer, has a surface roughness (Rz) lower than that of the exposed face. Thereby, the present invention provides a transfer sheet that has improved transfer performance for enabling transferring at low temperature, and improved dimensional stability and also a via-connection reliability. The present invention provides also a wiring board using the transfer sheet and a method of manufacturing the same.

1 - 16 . (canceled)  
   
   
       17 . A method of manufacturing a wiring board, comprising: 
 superposing, on an electrical insulating substrate sheet, a transfer sheet comprising a resin film having a glass transition temperature of not lower than 60° C., a silicone resin layer formed on the resin film, and a metal wiring pattern formed on the silicone resin layer, an exposed face of the metal wiring pattern forms a roughened face, and the roughened face has a ten-point average surface roughness (Rz) of at least 2 μm, while a face of the metal wiring pattern in contact with the silicone resin layer has a surface roughness (Rz) lower than the surface roughness of the exposed face;    applying pressure while heating to a temperature to allow the wiring pattern to be embedded in the insulating substrate sheet so as to embed at least one part of the wiring pattern in the insulating substrate sheet; and    peeling the resin film so as to obtain a wiring board with the embedded wiring pattern.    
   
   
       18 . The method according to  claim 17 , wherein the insulating substrate sheet has a viahole filled with a conductive paste, and the insulating substrate sheet is superposed so that the wiring pattern of the transfer sheet is connected to the conductive paste of the insulating substrate sheet.  
   
   
       19 . The method according to  claim 17 , wherein the insulating substrate sheet is prepared by filling the viaholes with the conductive paste, 
 the transfer sheet is superposed onto the insulating substrate sheet so that the wiring pattern is connected to the conductive paste, and the sheets are laminated by applying heat at temperature lower than a cure reaction peak temperature of the conductive paste, thereby embedding the wiring pattern in the insulating substrate sheet, and    the resin film is peeled to obtain an insulating substrate sheet with the embedded wiring pattern.    
   
   
       20 . The method according to  claim 17 , further comprising laminating a plurality of insulating substrate sheets obtained by the method according to  claim 17  in a batch, and curing the sheets.  
   
   
       21 . The method according to  claim 17 , wherein the transfer sheet is prepared by forming a primer layer on a resin film as a supporter, and subsequently forming the silicone resin layer on the primer layer.  
   
   
       22 . The method according to  claim 17 , wherein the wiring pattern is formed by etching a copper foil.