Browse Prior Art Database

Process for Preventing Chip Pad Corrosion

IP.com Disclosure Number: IPCOM000088230D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Haddad, MM: AUTHOR [+3]

Abstract

In semiconductor package substrates nickel pads are conventionally provided for solder bonding of the device to the substrate. On complex substrates utilizing multilayer ceramic (MLC) technology and a large number of devices, additional pads are provided for the connection of wires for correcting defects, making engineering changes, and the like. These pads which utilize thermo-compression bonding are preferably coated with a layer of heavy gold which is preferably deposited by electroplating. Prior to electroplating these pads with a layer of gold, the nickel pads are covered with a layer of resist in order to prevent them, also, from being electroplated.

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Process for Preventing Chip Pad Corrosion

In semiconductor package substrates nickel pads are conventionally provided for solder bonding of the device to the substrate. On complex substrates utilizing multilayer ceramic (MLC) technology and a large number of devices, additional pads are provided for the connection of wires for correcting defects, making engineering changes, and the like. These pads which utilize thermo-compression bonding are preferably coated with a layer of heavy gold which is preferably deposited by electroplating. Prior to electroplating these pads with a layer of gold, the nickel pads are covered with a layer of resist in order to prevent them, also, from being electroplated.

In complex structures a layer of conductive material is provided underneath the resist to make certain that the exposed pads to be electroplated are provided with a connection to the cathode. If the stop-off resist layer is not sufficiently tight over the device pads or has pin holes, etc., particularly at the interface with the rough ceramic surface, the electroplating solution may penetrate and come into contact with the conductive-paint layer on the nickel pads, causing corrosion of the nickel layer.

In this process, corrosion of the nickel pads covered by the resist can be prevented by utilizing a conductive paint that at least includes particles of a metal less noble than nickel, such as aluminum, magnesium and zinc.

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