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Method for a three-dimensional solder pad

IP.com Disclosure Number: IPCOM000013536D
Publication Date: 2003-Jun-18
Document File: 4 page(s) / 144K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a three-dimensional solder pad. Benefits include improved performance, improved reliability, and improved ease of implementation.

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Method for a three-dimensional solder pad

Disclosed is a method for a three-dimensional solder pad. Benefits include improved performance, improved reliability, and improved ease of implementation.

Background

      Conventional pad geometries are limited to the plane or below the plane of the printed circuit board (PCB) surface. When a second-level interconnection is constructed, it is subjected to loading through the initial stress of manufacturing, shipping/handling, and power/thermal cycling. Each of these loads creates localized damage of the second level interconnect if the elastic limit of the interconnect material is surpassed. When enough damage occurs from inelastic strain, the material develops microcracks near grain boundaries. These small cracks coalesce and form larger cracks in the PCB near the edges of the pad or component. Because most of the PCB interfaces are planar, no direct method exists to limit the propagation of the crack.

              Conventional solutions are to change the surface finish of the PCB, increase the pad size (which limits the routable escapes of the I/O of the package), and add preloading (which causes other stress related issues around the board).

General description

      The disclosed method is a three-dimensional solder pad. Its geometry acts as a crack arrest and provides a greater surface area for wetting solder.

              The key elements of the method include:

•             Three-dimensional pad with solder wetted to it

•             Copper deposition process to construct the three-dimensional pad

Advantages

              The disclosed method provides advantages, including:

•             Improved performance due to creating a greater wetted surface area than that of a planar pad

•             Improved performance due to the pad developing a greater controlled standoff height, making a joint more compliant

•             Improved reliability due to the three-dimensional pad consumes energy when it forces the fatigue crack front to change direction, adding time to the joint’s functional life

•        ®..