Browse Prior Art Database

Sacrificial Anode Ring on the Package and Board Pad for Solder Joint Reliability

IP.com Disclosure Number: IPCOM000074588D
Publication Date: 2005-Feb-23
Document File: 3 page(s) / 57K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a sacrificial anode (e.g. zinc, magnesium, etc.) on the package and board that is more reactive than the copper pad. Benefits include eliminating the oxidation that can lead to solderability and testing issues.

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Sacrificial Anode Ring on the Package and Board Pad for Solder Joint Reliability

Disclosed is a method that uses a sacrificial anode (e.g. zinc, magnesium, etc.) on the package and board that is more reactive than the copper pad. Benefits include eliminating the oxidation that can lead to solderability and testing issues.

Background

Currently, there is a need to address package ENIG brittle fracture issues. Switching to a new surface finish can address the issues, but can lead to major non-wetting problems. A change to other surface finishes, like Direct Immersion Gold (DIG), Immersion Silver (ImAg), and Organic Surfactant Protection (OSP) can improve solder joint reliability (SJR); however, they have limitations because the pads will corrode during processing before the solder ball attach
(see Figure 1).

General Description

The disclosed method uses a sacrificial anode to protect the test pad from being oxidized. The material of the sacrificial anode is more reactive compared with the material of the test pad.  Thus, this sacrificial anode prevents oxidation on the copper pad with DIG, ImAg, and OSP. 

Oxidation or corrosion of a test pad occurs by the generalized reaction M à Mn+ + ne-

Cat

hodic protection involves supplying, from an external source, electrons to the metal to be protected, making it a cathode; the reaction above is forced in the reverse (or reduction) direction.

One cathodic protection technique employs a galvanic couple; the metal to be protected is elec...