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Method for a mold pattern to enable solder printing onto 300-mm wafers down to 100-micron pitch

IP.com Disclosure Number: IPCOM000010019D
Publication Date: 2002-Oct-09
Document File: 3 page(s) / 36K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a mold pattern to enable solder printing onto 300-mm wafers down to 100-micron pitch. Benefits include improved functionality and improved reliability.

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Method for a mold pattern to enable solder printing onto 300-mm wafers down to 100-micron pitch

Disclosed is a method for a mold pattern to enable solder printing onto 300-mm wafers down to 100-micron pitch. Benefits include improved functionality and improved reliability.

Background

� � � � � Screen printing stencils are limited by the web spacing between the apertures. The web spacing cannot be decreased below 45 microns as the stencil begins to deform under the tension and printing forces. As the pitch of the flip-chip interconnect shrinks, the apertures must also shrink to maintain the minimum web spacing. This approach results in less solder volume deposited on the wafer, which limits the die-to-package joint capability.

        � � � � � Conventionally, nickel stencils are electroformed with a minimum web spacing of 45 microns (see Figure 1). No conventional solution exists that meets production requirements.

Description

� � � � � The disclosed method is a 300-mm silicon wafer drilled to aperture shapes, pitch, and size for a product similar to nickel stencils. A silicon wafer with laser-drilled holes in a bump design is attached to a metal support frame and used as a model to print solder in screen-print style.

� � � � � Silicon wafers can be laser drilled or deep reactive ion etched (DRIE) to the tighter tolerances in the required pitches and aperture sizes (see Figure 2). They can be used in place of the nickel web to force the solder to the wafer for printing. Reliability requiremen...