International Business Machines Corporation

John D Larnerd

Russell E Darrow

Ronald J Moore

Alan J Emerick

Robert W Nesky

John M Atkinson

Glenn J Ingraham

Disclosed is a method of fabricating a microelectronic package, especially a microelectronic package having copper circuitization on a dielectric substrate. The method includes the steps of depositing, imaging, developing the photoresist for additive circuitization, and forming a pattern of copper circuitization on the so exposed portions of the package. In order to avoid the formation of deleterious air bubbles on the exposed walls of the imaged and developed resist, the panel is exposed to and wetted by a liquid mist.

Method of additive circuitization of circuit boards with high adhesion,

A method of solder leveling in printed circuit boards or other circuitized substrates. Flux is first applied to the surface of the substrate to be soldered. Molten solder is then applied to the fluxed surface after which the soldered substrate is cooled to a temperature below 300.degree. F. Molten solder is then again applied to the previously soldered surface of the substrate. This last step results in leveling the solder first applied to the substrate, including removal of any solder balls which had been formed over recessed pins and flush filling of passage holes formed in the substrate. The method can be performed without regard to the surface condition of the substrate, the composition of flux and solder, whether the substrate is of the thin film type or of the thick film type, nor whether dip soldering or wave soldering techniques are used. The invention also incompasses the end product resulting from use of the method.

Solder leveling technique

A machine for forming a head and a bulge on a copper pin and to connect the pin to a ceramic substrate by a single application of impact force at high velocity and controlled energy conditions includes an air cylinder within which a piston of controlled mass moves due to the effect of compressed air stored in an accumulator. A die block includes a two dimensional array of holes into which are fitted pin blanks that extend above the surface of the die block and on which is fitted a substrate having an identical array of pin holes formed therein. The pins are fitted within the die block and on the substrate such that a predetermined length of the pin blank extends above the surface of the substrate and a controlled length of the pin blanks extends between the substrate and the die block. The pins are retained within the die against axial movement and the holes in the substrate and die block provide radial restraint to the pins following the application of the impact force. The substrate is elastically supported to deflect after impact while the pin head and bulge are forming.

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Owego, NY, United States of America

John D Larnerd