Metal covered polyimide composite, process for producing the composite, and process for producing electronic circuit board

A metal covered polyimide composite, comprising:

• a polyimide film;
• a tie-coat layer formed on a surface of said polyimide film;
• a metal seed layer formed on said tie-coat layer;
• and
• a copper or copper alloy layer directly formed on said metal seed layer by electroplating, said copper or copper alloy layer consisting of two or three separately-applied plating layers with a boundary only being formed and located between each adjacent pair of plating layers and a concentrated portion of impurities being present only within the boundary between each adjacent pair of plating layers and not within the two or three separately-applied plating layers;
• each of said two or three separately-applied plating layers having a thickness within a range of 2.07 μm to 8.50 μm;
• and
• no further layers of copper or copper alloy are plated on said two or three separately-applied plating layers of copper or copper alloy of the metal covered polyimide composite.

A method of producing a metal-covered polyimide composite, comprising the steps of:

• forming a tie-coat layer on a surface of a polyimide film and a metal seed layer on the tie-coat layer;
• and
• feeding the polyimide film with the tie-coat layer and the metal seed layer around a plating drum within an electroplating bath to electroplate two or three plating layers of copper or copper alloy on the metal seed layer such that a boundary containing concentrated impurities is formed between each adjacent pair of the two or three plating layers of copper or copper alloy;
• wherein the electroplating bath has an electroplating area divided into a plurality of electroplating zones, a pre-determined one of the plurality of electroplating zones consisting of two adjacent anode plates which are electrically connected and which have a gap formed therebetween equal to or less than half a distance between surfaces of the two adjacent anode plates facing the plating drum and the polyimide film traveling on the plating drum;
• and
• wherein one of the two or three plating layers of copper or copper alloy being formed in the pre-determined one of the plurality of electroplating zones.

A method of producing a metal-covered polyimide composite, comprising the steps of:

• forming a tie-coat layer on a surface of a polyimide film and a metal seed layer on the tie-coat layer;
• and
• feeding the polyimide film with the tie-coat layer and the metal seed layer around a first plating drum within a first electroplating bath and a second plating drum within a second electroplating bath to electroplate two or three plating layers of copper or copper alloy on the metal seed layer such that a boundary containing concentrated impurities is formed between each adjacent pair of the two or three plating layers of copper or copper alloy;
• wherein the first electroplating bath includes an electroplating zone consisting of two adjacent anode plates which are electrically connected and which have a gap formed therebetween equal to or less than half a distance between surfaces of the two adjacent anode plates facing the first plating drum and the polyimide film traveling on the first plating drum;
• wherein the second electroplating bath includes an electroplating zone consisting of two adjacent anode plates which are electrically connected and which have a gap formed therebetween equal to or less than half a distance between surfaces of the two adjacent anode plates facing the second plating drum and the polyimide film traveling on the second plating drum;
• and
• wherein one of the two or three plating layers of copper or copper alloy is formed in the electroplating zone of the first electroplating bath and another one of the two or three plating layers of copper or copper alloy is formed in the electroplating zone of the second electroplating bath.