Formation of Fine Pitch Traces Using Ultra-Thin PAA Modified Fully Additive Process

A method of manufacturing a flexible substrate comprising:

• providing a flexible dielectric substrate;
• laser drilling at least one first via opening all the way through said dielectric substrate;
• applying an alkaline modification to said dielectric substrate to form a first polyamic acid (PAA) anchoring layer on top and bottom surfaces of said dielectric substrate;
• electrolessly plating a first Ni—P seed layer on top and bottom of said first PAA layers;
• forming a first photoresist pattern on top and bottom of said first Ni—P seed layers;
• plating first copper traces within said first photoresist patterns and through said at least one first via opening;
• plating a surface finishing layer on said first copper traces;
• and
• removing said first photoresist patterns and etching away said first Ni—P seed layers not covered by said first copper traces to complete said flexible substrate.

A method of manufacturing a flexible substrate comprising:

• providing a flexible dielectric substrate;
• laser drilling at least one first via opening all the way through said dielectric substrate;
• applying an alkaline modification to said dielectric substrate to form a first polyamic acid (PAA) anchoring layer on top and bottom surfaces of said dielectric substrate;
• electrolessly plating a first Ni—P seed layer on top and bottom of said first PAA layers;
• forming a first photoresist pattern on top and bottom of said first Ni—P seed layers;
• plating first copper traces within said first photoresist patterns and through said at least one first via opening;
• removing said first photoresist patterns and etching away said first Ni—P seed layers not covered by said first copper traces;
• thereafter laminating a bonding film on top and bottom surfaces of said first copper traces;
• laminating a dielectric layer on top and bottom of said bonding films;
• laser drilling at least one second via opening all the way through said dielectric layer and said bonding film to contact said first copper traces on top and bottom of said substrate;
• thereafter applying an alkaline modification to said dielectric layers to form a second polyamic acid (PAA) anchoring layer on top and bottom surfaces of said dielectric layers and within said at least one second via openings;
• electrolessly plating a second Ni—P seed layer on top and bottom of said second PAA layers;
• forming a second photoresist pattern on top and bottom of said second Ni—P seed layers;
• plating second copper traces within said second photoresist patterns and through said at least one second via opening;
• plating a surface finishing layer on said second copper traces;
• and
• removing said second photoresist patterns and etching away said second Ni—P seed layers not covered by said second copper traces to complete said flexible substrate.

A chip on film comprising:

• a flexible dielectric substrate having a first polyamic acid (PAA) anchoring layer on its top surface;
• at least one first copper trace on a first Ni—P seed layer on said first PAA layer and having a surface finishing layer on a top surface of said at least one first copper trace;
• and
• at least one die mounted on said dielectric substrate to said at least one first copper trace.