Centrifugal method for filing high aspect ratio blind micro vias with powdered materials for circuit formation

A process for filling via openings on a substrate comprising:

• providing a substrate having via openings defined on a via-surface;
• providing at least a layer of a fluid particulate suspension on said via-surface;
• centrifuging said substrate:
• wherein said centrifugation is performed with a swinging-bucket rotor;
• wherein said fluid particulate suspension comprises:
• a suspension fluid;
• and
• a plurality of particles;
• wherein said suspension fluid is a reactive fluid comprising a curable liquid resin and a dispersing agent;
• wherein said curable liquid resin comprises polynorbornenes;
• wherein said dispersing agent comprises naphthalene sulfonic acid condensates;
• wherein said plurality of particles is selected from cores coated with metals;
• wherein a first portion of said cores is coated with a first solder-forming metal;
• a second portion of said cores is coated with a solder-forming metal complementary to said first metal;
• and
• wherein said cores comprise a ceramic having a negative volumetric coefficient of thermal expansion;
• wherein said ceramic is beta-eucryptite;
• and
• wherein said substrate is electrically biased relative to said fluid particulate suspension;
• brushing said via-surface during centrifugation;
• vibrating said substrate during centrifugation;
• creating a vacuum in a centrifuge chamber;
• spraying a fluid particulate suspension against said via-surface;
• curing said reactive fluid thereby forming a substantially solid mass in said via;
• providing a brush means;
• wiping excess particles from said via-surface using said brush means;
• wherein said brush means comprises doctor blades;
• providing a filler-mask having through-via defined herein,
• said filler-mask having a via-surface disposed to contact said fluid suspension and
• a substrate-contact surface disposed to contact said substrate via-surface;
• and
• aligning said mask on said substrate via-surface;
• wherein the openings of said through-via are wider at said mask via-surface than at said substrate-contact surface and said through-via has multiple substrate-contact surface openings.