Process for manufacture of printed circuit boards with thick copper power circuitry and thin copper signal circuitry on the same layer

Abstract

A process of manufacturing printed circuit boards which is useful in the formation of printed circuit boards containing both areas of thick conductive traces and areas of fine resolution conductors in a single conductive layer, and printed circuit boards formed from such a process. A conductive core is first fabricated containing areas of thick conductors on a relatively thin conductive base. The conductive core is then bonded to a sublayer such as “prepreg” with the thick conductive areas adjacent to the sublayer in order to form a relatively flat laminate. Proper bonding typically requires the use of high resin “prepreg” sublayer. In the alternative, an additional inner layer of pure resin can be inserted between the conductive core and the insulating sublayer prior to bonding. After bonding, the conductive surface of the laminate is formed into printed conductor traces by methods known in the art. For example, chemical etching may be used to remove conductive material not comprising the printed circuits. In various embodiments of the invention a solder mask coating is applied to the completed printed circuit board. By use of this process, a single layer printed circuit comprising both thick conductor traces and fine resolution traces is possible. This invention is also useful in manufacturing a printed circuit core or layer suitable for use as a component in a multilayer printed circuit board where it is desirable that a relative flat layer containing thick conductor traces be provided.

We claim:  
     
         1 . A printed circuit board formed by the process comprising: 
 forming a conductor core containing a thin base of electrically conductive material and areas of thick conductive material in a predetermined pattern;    bonding the conductor core to a sublayer of electrically insulating material to create a flat laminate, wherein the areas of thick conductive material are positioned adjacent to the sublayer; and,    forming predetermined printed circuits by removing conductive material from the flat laminate that does not comprise said predetermined printed circuits to form the predetermined printed circuits.    
     
     
         2 . The printed circuit board of  claim 1  wherein the conductor core and predetermined printed circuits comprise copper.  
     
     
         3 . The printed circuit board of  claim 1  wherein forming of the conductive core further comprises electrolytically depositing the areas of thick electrically conductive upon the thin electrically conductive base.  
     
     
         4 . The printed circuit board of  claim 1  wherein the sublayer of electrically insulating material comprises sheets of glass fiber reinforced with resin that is dried but not cured.  
     
     
         5 . The printed circuit board of  claim 4  wherein the bonding of the conductor core to conductor core to the sublayer.  
     
     
         6 . The printed circuit board of  claim 5  wherein the hot pressing is performed at sufficient temperature and for a sufficient period of time to enable full and complete curing of the resins in the insulating sublayer.  
     
     
         7 . The printed circuit board of  claim 1  wherein removing of conductive material is accomplished through chemical etching.  
     
     
         8 . The printed circuit board of  claim 1  further comprising applying a solder mask coating over predetermined areas of the printed circuit board.  
     
     
         9 . The printed circuit board of  claim 1  wherein said thin base is of a thickness in the range of 0.0003 inches to 0.0020 inches.  
     
     
         10 . The printed circuit board of  claim 1  wherein said thin base is of a thickness in the range of 0.0003 inches to 0.0007 inches.  
     
     
         11 . The printed circuit board of  claim 1  wherein said areas of thick conductive material are of a thickness in the range of 0.004 inches to 0.020 inches in predetermined pattern of conductor traces.  
     
     
         12 . The printed circuit board of  claim 1  wherein said areas of thick conductive material are of a thickness in the range of 0.004 inches to 0.010 inches in a predetermined pattern of conductor traces.  
     
     
         13 . A printed circuit board formed by the process comprising: 
 forming a conductor core containing a thin base of electrically conductive material and areas of thick conductive material in a predetermined pattern;    bonding the conductor core to an inner layer of resinous material and a sublayer of electrically insulating material to create a flat laminate, wherein the areas of thick conductive material are positioned adjacent to the inner resinous material layer that is in turn positioned adjacent to the sublayer of insulating;    said layer of resinous material selected from a group of resinous materials that is compatible with the sublayer of electrically insulating material and;    removing conductive material from the flat laminate that does not comprise said predetermined printed circuits to form a predetermined printed circuit.    
     
     
         14 . The printed circuit board of  claim 13  wherein the conductor core and predetermined printed circuits comprise copper.  
     
     
         15 . The printed circuit board of  claim 13  wherein forming of the conductive core further comprises electrolytically depositing the areas of thick electrically conductive upon the thin electrically conductive base.  
     
     
         16 . The printed circuit board of  claim 13  wherein the sublayer of electrically insulating material comprises sheets of glass fiber reinforced with resin that is dried but not cured.  
     
     
         17 . The printed circuit board of  claim 16  wherein the bonding of the conductor core to the sublayer of electrically insulating material comprises hot pressing the conductor core to the sublayer.  
     
     
         18 . The printed circuit board of  claim 17  wherein the hot pressing is performed at complete curing of the resins in the insulating sublayer.  
     
     
         19 . The printed circuit board of  claim 13  wherein removing of conductive material. is accomplished through chemical etching.  
     
     
         20 . The printed circuit board of  claim 13  further comprises applying a solder mask coating over predetermined areas of the printed circuit board.  
     
     
         21 . The printed circuit board of  claim 13  wherein said thin base is of a thickness in the range of 0.0003 inches to 0.0020 inches.  
     
     
         22 . The printed circuit board of  claim 13  wherein said thin base is of a thickness in the range of 0,0003 inches to 0.000'7 inches.  
     
     
         23 . The printed circuit board of  claim 13  wherein said areas of thick conductive material are in the range of 0.004 inches to 0.020 inches in a predetermined pattern of conductor traces.  
     
     
         24 . The printed circuit board of  claim 13  wherein said areas of thick conductive material are in the range of 0.004 inches to 0.010 inches in a predetermined pattern of conductor traces.  
     
     
         25 . A printed circuit core suitable for use as a component of a multilayer printed circuit formed by the process comprising: 
 forming a conductor core comprising a thin base of electrically conductive material and areas of thick conductive material in a predetermined pattern;    bonding the conductor core to a sublayer of electrically insulating material creating a flat laminate, wherein the areas of thick conductive material are positioned adjacent to the sublayer; and;    removing conductive material from the flat laminate that does not comprise said predetermined printed circuits thereby forming predetermined printed circuits.    
     
     
         26 . The printed circuit core of  claim 25  wherein the conductor core and predetermined printed circuits comprise copper.  
     
     
         27 . The printed circuit core of  claim 25  wherein forming of the conductive core further comprises electrolytically depositing the areas of thick electrically conductive upon the thin electrically conductive base.  
     
     
         28 . The printed circuit core of  claim 25  wherein the sublayer of electrically insulating material comprises sheets of glass fiber reinforced with resin that is dried but not cured.  
     
     
         29 . The printed circuit core of  claim 28  wherein the bonding of the conductor core to the sublayer of electrically insulating material is performed by hot pressing the conductor core to the sublayer.  
     
     
         30 . The printed circuit core of  claim 29  wherein the hot pressing is performed at sufficient temperature and for a sufficient period of time to enable full and complete curing of the resins in the insulating sublayer.  
     
     
         31 . The printed circuit core of  claim 25  wherein removing of conductive material is accomplished through chemical etching.  
     
     
         32 . The printed circuit core of  claim 25  wherein said thin base is of a thickness in the range of 0.0003 inches to 0.0020 inches.  
     
     
         33 . The printed circuit core of  claim 25  wherein said thin base is of a thickness in the range of 0.0003 inches to 0.0007 inches.  
     
     
         34 . The printed circuit core of  claim 25  wherein said areas of thick conductive material are in the range of 0.004 inches to 0.020 inches in a predetermined pattern of conductor traces.  
     
     
         35 . The printed circuit core of  claim 25  wherein said areas of thick conductive material are in the range of 0.004 inches to 0.01 0 inches in a predetermined pattern of conductor traces.