E.i. Dupont De Nemours and Company

University of California

Allan Cairncross

John Edwin Gantzhorn, Jr

Chester A Thayer, Ii

George Yeaman Thomson, Jr

Thomas Kenneth Bednarz

Ulrich Klabunde

Catherine T Chang

Michael Arnett Smith

Donald R Baer

Methods and associated apparatus are disclosed for use in mounting particles on and de-mounting particles from a substrate having an array of tacky and non-tacky areas. The particles can be either electrically conducting or electrically non-conducting. Selection of electrically conducting particles is preferred. The substrate having an array of tacky and non-tacky areas can either be electrically non-conducting (e.g., a dielectric substrate) or electrically-conducting. The methods involve use of first and second electrode plates with the substrate therebetween, the plates having applied thereto a direct current potential, which potential in preferred embodiments is reversed in polarity for a number N of cycles. Methods and articles are disclosed using an electrically conductive surface adjacent the tacky and non-tacky areas to minimize static buildup on the particles and tacky and non-tacky areas.

Electrostatic methods and apparatus for mounting and demounting particles from a surface having an array of tacky and non-tacky areas

Improved methods and apparatus are disclosed for efficiently and precisely adhering and centering particles on tacky areas on a surface containing an array of tacky and non-tacky areas. These improved methods and apparatus for particle attachment and centering involve holding and heating of the surface containing an array of tacky and non-tacky areas with particles adhered thereon for a period of time and at a temperature to allow the particles to adhere and center to the tacky areas. The surface containing the array of tacky and non-tacky areas can be heated either prior to, during or after a step of contacting the array with particles. Either discrete sheets or a continuous moving web of material having a surface containing an array of tacky and non-tacky areas can be employed. Each tacky area of an array of tacky and non-tacky areas has a size and bonding strength suitable for adhesion of one particle thereto in formation of an array. The array is populated with conductive-particles, is useful in the precise placement of particles on contact pads of electronic devices, such as circuit boards in semiconductor applications.

Method and apparatus for adhering and centering particles to the tacky areas on a surface containing an array of tacky and non-tacky areas

Methods and apparatus are disclosed for efficiently and precisely adhering and centering particles on tacky areas on a surface containing an array of tacky and non-tacky areas. These methods and apparatus for particle attachment and centering involve holding and heating of the surface containing an array of tacky and non-tacky areas with particles adhered thereon for a period of time and at a temperature to allow the particles to adhere and center to the tacky areas. The surface containing the array of tacky and non-tacky areas can be heated either prior to, during or after a step of contacting the array with particles. Either discrete sheets or a continuous moving web of material having a surface containing an array of tacky and non-tacky areas can be employed. Each tacky area of an array of tacky and non-tacky areas has a size and bonding strength suitable for adhesion of one particle thereto in formation of an array. The array is populated with conductive-particles, is useful in the precise placement of particles on contact pads of electronic devices, such as circuit boards in semiconductor applications.

Method for precise placement of an array of single particles on a surface

Polymeric ledges on a metal stencil screen are made using a polymeric layer which is partially removed by a developer solution.

Process for making improved metal stencil screens for screen printing

The process and product are disclosed for mounting free-flowing particles, which employ a support having a support surface with an array of tacky areas which have a size and bonding strength suitable for adhesion of either one or two of said particles. In the process the particles flow across the support surface to allow particles to contact the tacky areas and adhere thereto. An array of mounted particles may thus be provided which has at least 50% singly or doubly mounted particles.

Method and product for particle mounting

A process for making a metal ledge on one side of a metal screen involves exposing through the stencil screen a photoresist layer, removing unexposed photoresist areas, plating the metal stencil screen where the unexposed photoresist has been removed and removing the exposed photoresist.

Process for making metal ledge on stencil screen

A process is described for defined etching of holes using a sliver mask formed by silver diffusion transfer imaging.

Process for defined etching of substrates

Compositions and films are provided for the preparation of electrostatic printing masters. The composition binder permits use of aqueous silver halide photographic techniques to image the master for printing, and exhibits insulation properties needed for electrostatic printing under typical conditions of relative humidity.

Silver-based electrostatic printing master

Tetracyanopyrazine reacts with aromatic amines to give products of the formula ##SPC1## Wherein

Growing community of inventors

Hockessin, DE, United States of America

Allan Cairncross