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Method for fine-pitch substrate pre-soldering using an in-place photo-definable resist material

IP.com Disclosure Number: IPCOM000008059D
Publication Date: 2002-May-15
Document File: 3 page(s) / 60K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for fine-pitch substrate pre-soldering using an in-place photo-definable resist material. Benefits include process simplification and improved functionality.

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Method for fine-pitch substrate pre-soldering using an in-place photo-definable resist material

Disclosed is a method for fine-pitch substrate pre-soldering using an in-place photo-definable resist material. Benefits include process simplification and improved functionality.

Background

              The conventional process for substrate pre-soldering is stencil printing. In this process, a stencil is fabricated in the pattern of the chip-attach pads on the substrate. The stencil is aligned on top of the substrate, and solder is transferred to the substrate via a squeegee-based printing process. 

              As the pitch of the integrated circuit (IC) interconnects become smaller, more demands are placed on the stencil fabrication accuracy and stencil-to-substrate alignment. Although conventional pitches support high-yielding printing processes, the interconnect pitches of the future may pose significant challenges for this process.

Description

              The disclosed method deposits solder onto the chip-attach pads of a high-density, integrated circuit substrate. The substrate pre-solder forms interconnections to the IC chip.

              The key elements of the method include (see Figures 1 and 2):

§         Use of a photo-definable resist material as an in-place solder printing mask

§         A process for pre-soldering substrate pads with a photo-definable resist material:
              1.           Resist application
              2.           Exposure and development
              3.           Solder printing
              4.           Reflow
              5.           Resist removal

§         A photo-definable resist material that meets the following require...