University of California

Melissa Orme-Marmerelis

Robert F Smith, Jr

In a high-speed fabrication process for producing highly uniform metallic microspheres, a molten metal is passed through a small orifice, producing a stream of molten metal therefrom. A series of molten metal droplets forms from the break up of the capillary stream. To achieve high uniformity of the spheres and avoid defects, the droplets are cooled before being captured. Separating the droplets, by causing them to travel in different paths than their adjacent droplets, helps to facilitate the cooling of the droplets. The droplets can be separated by electrostatically charging them as they break off from the capillary stream. The droplets are then passed through an electric field, which can be produced by a pair of deflection plates. The droplets are dispersed by varying the electric field&#x2014;e.g., by rotating the plates or by varying the voltage applied thereto&#x2014;or by varying the electrostatic charge of the droplets. Advantageously, the droplets can be actively cooled in flight by passing them through a cryogenic gas chamber.

High-speed fabrication of highly uniform metallic microspheres

In a high-speed fabrication process for producing highly uniform metallic microspheres, a molten metal is passed through a small orifice, producing a stream of molten metal therefrom. A series of molten metal droplets forms from the break up of the capillary stream. To achieve high uniformity of the spheres and avoid defects, the droplets are cooled before being captured. Separating the droplets, by causing them to travel in different paths than their adjacent droplets, helps to facilitate the cooling of the droplets. The droplets can be separated by electrostatically charging them as they break off from the capillary stream. The droplets are then passed through an electric field, which can be produced by a pair of deflection plates. The droplets are dispersed by varying the electric field&mdash;e.g., by rotating the plates or by varying the voltage applied thereto&mdash;or by varying the electrostatic charge of the droplets. Advantageously, the droplets can be actively cooled in flight by passing them through a cryogenic gas chamber.

Ultra-small satellite droplets of molten metal, generated from capillary stream break-up, are selectively directed to predetermined locations on a substrate. The satellite droplets are produced at a high rate and are highly uniform because of the nature of capillary stream break-up. Applied harmonic disturbances are used to control and generate the satellite and parent droplets. The satellite droplets are electrostatically charged on a droplet-by-droplet basis and are then deflected by, e.g., an electric field to predetermined locations on a substrate. The substrate is moveable, attached to an x-y table, for facilitating the placement of satellite droplets on the substrate. The satellite droplets can be placed in individual locations on the substrate (e.g., for forming a ball grid array) or can be overlapped to form conductive traces. Because the satellite droplets have small diameters, these traces may have correspondingly small widths or pitches.

High-speed direct writing with metallic microspheres

In a high-speed fabrication process for producing highly uniform ultra-small metallic micro-spheres, a molten metal is passed through a small orifice, producing a stream of molten metal therefrom. A series of molten metal droplets forms from the break up of the capillary stream. Applied harmonic disturbances are used to control and generate satellite and parent droplets. Significantly, the satellite droplets formed are smaller than the orifice, allowing for the production of smaller metal balls with larger orifices. The satellite droplets are separated from the parent droplets by electrostatic charging and deflection or by aerodynamic or acoustic sorting. Preferably, the satellite droplets are cooled before being collected to avoid defects and achieve high uniformity of the resulting metal balls.

Growing community of inventors

Irvine, CA, United States of America

Melissa Orme-Marmerelis