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Alternative method to form C4 bumps with solder paste

IP.com Disclosure Number: IPCOM000009592D
Publication Date: 2002-Sep-04
Document File: 3 page(s) / 51K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for controlled collapse chip connect (C4) bumps formed with solder paste. Benefits include improved design and manufacturing flexibility.

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Alternative method to form C4 bumps with solder paste

Disclosed is a method for controlled collapse chip connect (C4) bumps formed with solder paste. Benefits include improved design and manufacturing flexibility.

Background

        � � � � � Conventional technology forms C4 bumps by either electroplating or screen printing solder onto a substrate near the end of the manufacturing process.� When electroplating, it is often difficult to control the volume of solder and to control the stoichiometry of the plated alloys. Ternary alloys are very difficult, if not impossible to plate. Binary alloys may be difficult to plate, but the process is possible. Conventional screen printing of solder bumps is also limited to approximately 150um pitch. This method allows a wide range of solders to be used, can extend pitch capability beyond 150um, and allows the solder bumps to be formed at the beginning (rather than at the end) of the manufacturing process.

General description

� � � � � The disclosed method is to squeegee solder paste into photo-defined, etch-formed cavities in a dielectric coated copper plate, with reflow prior to electrolytic copper plating. Semi-additive or subtractive buildup processes are applied to form a multilayer substrate. Near the end of the manufacturing process, the copper base plate is etched away, exposing the bumps that were formed within the base plate at the beginning of the process.

� � � � � The key elements of the method include:

•        � � � � Photo-definined, etch-formed cavities in an organic-coated copper base plate.

•        � � � � Squeegeeing solder paste of any alloy into the cavities

•        � � � � Reflowing the solder paste within the cavities to form the solder alloy and solidify the bump

•        �...