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Method for an Ni-Pd-Al-Au surface finish

IP.com Disclosure Number: IPCOM000146418D
Publication Date: 2007-Feb-13
Document File: 2 page(s) / 107K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a nickel-palladium-aluminum-gold (Ni-Pd-Al-Au) surface finish. Benefits include improved functionality and improved performance.

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Method for an Ni-Pd-Al-Au surface finish

Disclosed is a method for a nickel-palladium-aluminum-gold (Ni-Pd-Al-Au) surface finish. Benefits include improved functionality and improved performance.

Background

      Ni-Pd-Au is a conventional surface finish for ball-grid array (BGA) packages for higher solder joint reliability. Additionally, Ni-Pd-Au provides improved maximum current draw (Imax) performance over electroless nickel immersion gold plus electrolytic gold (ENIG+EG) and ENIG (see Figure 1).

      However, Ni-Pd-Au can result in poor electrical performance in land-grid array (LGA) packages. The interdiffusion of Au and Pd results in an increase in contact resistance due to the nonconformance of the surface because of its hardness (see Figure 2).

Description

      The disclosed method is a Ni-Pd-Al-Au surface finish. The method applies to copper substrates with LGA or BGA interconnections.

      The method uses Al as a barrier layer to prevent solid solution formation between Au and Pd. The Al provides lower hardness and excellent electrical conductivity (see Figure 3).

      The Ni-Pd-Al-Au surface finish decreases the low-level contact resistance by preventing or minimizing the formation of a Au-Pd solid solution. Additionally, the Al does not form a solid solution. As a result, the package functions similar...