Multilayered printed circuit board and manufacturing method thereof

Abstract

An opening is formed in resin 20 by a laser beam so that a via hole is formed. At this time, copper foil 22 , the thickness of which is reduced (to 3 μm) by performing etching to lower the thermal conductivity is used as a conformal mask. Therefore, an opening 20 a can be formed in the resin 20 if the number of irradiation of pulse-shape laser beam is reduced. Therefore, occurrence of undercut of the resin 20 which forms an interlayer insulating resin layer can be prevented. Thus, the reliability of the connection of the via holes can be prevented. Thus, the reliability of the connection of the via holes can be improved.

1 . A multilayered printed circuit board comprising: a substrate on which a conductive circuit is formed; an interlayer insulating resin layer formed on the conductive circuit; an opening for forming a via hole formed in the interlayer insulating resin layer; and another conductive circuit including a via hole and formed on the interlayer insulating resin layer, wherein the surface of the conductive circuit is subjected to a coarsening process using etching solution containing cupric complex and organic acid, and stripe pits and projections are formed on the inner wall of the opening for forming the via hole. 
     
     
         2 . A method of manufacturing a multilayered printed circuit board including (1) a step of forming a conductive circuit; (2) a step of forming an interlayer insulating resin layer on the conductive circuit; (3) a step of applying a laser beam to form an opening for forming a via hole in the interlayer insulating resin layer; and (4) a step of forming another conductive circuit including a via hole on the interlayer insulating resin layer, wherein the surface of the conductive circuit is subjected to a coarsening process by using etching solution containing cupric complex and organic acid. 
     
     
         3 . A method of manufacturing a multilayered printed circuit board according to  claim 1 , wherein the etching solution containing the cupric complex and the organic acid is sprayed to the surface of the conductive circuit or the conductive circuit is immersed in the etching solution under a bubbling condition so that the surface of the conductive circuit is subjected to the coarsening process. 
     
     
         4 . A method of manufacturing a multilayered printed circuit board comprising at least the steps (a) to (d): (a) forming a conductive circuit; (b) coating the conductive circuit with resin; (c) irradiating the resin with a carbon-dioxide gas laser beam to form a through hole which reaches the conductive circuit such that the carbon-dioxide gas laser beam is vertically applied to the conductive circuit below the resin to cause interference of reflected wave from the conductive circuit and incident wave to occur so that stripe pits and projections are formed on the side wall of the through hole; and (d) coating the through hole with metal to form a via hole. 
     
     
         5 . A method of manufacturing a multilayered printed circuit board according to  claim 4 , wherein the resin is thermosetting resin or a composite material of the thermosetting resin and thermoplastic resin. 
     
     
         6 . A method of manufacturing a multilayered printed circuit board according to  claim 4  or  5 , wherein the step of forming the via hole includes a step of forming a resist after an electroless copper plated film has been formed in the through hole and supplying electric power through the electroless plated film to form an electrolytic plated film in a portion in which the resist is not formed. 
     
     
         7 . A multilayered printed circuit board according to any one of  claims 4  to  6 , wherein the interlayer insulating resin layer contains acrylic monomer. 
     
     
         8 . A method of manufacturing a printed circuit board comprising at least the steps (a) and (b): (a) forming a solder-resist layer on the surface of a substrate on which a conductive circuit has been formed; and (b) irradiating the solder-resist layer with a laser beam to form a through hole which reaches the conductive circuit. 
     
     
         9 . A method of manufacturing a printed circuit board according to  claim 8 , wherein the surface of the conductive circuit has a metal coarsened layer. 
     
     
         10 . A method of manufacturing printed circuit board according to  claim 8 , wherein (c) a step of forming a bump made metal having a low melting point in the through hole is performed after the step (b). 
     
     
         11 . A method of manufacturing printed circuit board according to  claim 8 , wherein a laser beam in a single mode is applied in the step of forming the through hole so that a through hole having a diameter of 300 μm to 650 μm is formed. 
     
     
         12 . A method of manufacturing printed circuit board according to  claim 8  wherein a laser beam in a multi mode is applied in the step of forming the through hole so that a through hole having a diameter of 50 μm to 300 μm is formed. 
     
     
         13 . A method of manufacturing a printed circuit board according to any one of  claims 8  to  12 , wherein the step of forming the through hole is performed such that the carbon-dioxide gas laser beam is vertically applied to the conductive circuit below the resin to cause interference of reflected wave from the conductive circuit and incident wave to occur so that stripe pits and projections are formed on the side wall of the through hole. 
     
     
         14 . A method of manufacturing a printed circuit board according to  claim 13 , wherein the step of forming the bump is performed such that a metal film is provided for the through hole having the side wall provided with the stripe pits and projections, and then metal having a low melting point is enclosed. 
     
     
         15 . A method of manufacturing a multilayered printed circuit board such that a through hole is formed in a double-side copper-plated laminated board by performing a laser machining and the through hole is made to be conductive to form a through hole so that a core substrate is manufactured, and an interlayer insulating resin layer and a conductive circuit are formed on the core substrate, said method of manufacturing a multilayered printed circuit board comprising the step of: making the thickness of copper foil of the double-side copper-plated laminated board to be smaller than 12 μm. 
     
     
         16 . A method of manufacturing a multilayered printed circuit board according to  claim 15 , wherein the laser machining uses a carbon-dioxide gas laser beam. 
     
     
         17 . A method of manufacturing a multilayered printed circuit board according to  claim 15  or  16 , wherein the laser machining uses short-pulse carbon-dioxide gas laser beam of 20 mJ to 40 mJ and 10 −4  second to 10 −8  second. 
     
     
         18 . A method of manufacturing a printed circuit board incorporating through holes and conductor patterns formed by a subtractive method, said method of manufacturing a printed circuit board comprising: an opening forming step for forming an opening for forming a through hole at a predetermined position of a metal-applied board formed by applying-conductive metal foil having a thickness of 0.5 μm to 7.0 μm to each of two sides of an insulating substrate; a desmear step for dissolving and removing smear existing in the opening for forming the through hole; a first plating step for forming a thin plated layer on a ground layer caused from the conductive metal foil and the surface of the inner wall of the opening for forming the through hole; a second plating step for forming a mask on the thin plated layer and forming a thick plated layer on a portion exposed through an opening of the mask; and performing etching after the mask has been separated so that the thin plated layer and the ground layer below the mask are removed so as to divide the conductor patter. 
     
     
         19 . A method of manufacturing a printed circuit board according to  claim 18 , wherein the conductive metal foil including at least one of Cu, Ni, Sn, Au, Ag, Pt or Al. 
     
     
         20 . A method of manufacturing a printed circuit board according to  claim 18 , wherein the first plating step uses an electroless plating bath, and the second plating step uses an electrolytic plating bath. 
     
     
         21 . A method of manufacturing a printed circuit board according to  claim 18 , wherein the first plating step uses an electroless copper plating bath to form a copper plated layer having a thickness of 0.2 μm to 2.5 μm, and the second plating step uses an electrolytic copper plating bath to form a copper plated layer having a thickness of 8.0 μm or greater. 
     
     
         22 . A method of manufacturing a printed circuit board according to any one of  claims 18  to  21 , wherein the step for dividing the conductor pattern by performing etching is performed in a state in which no etching resist is provided for the thick plated layer formed in the second plating step.