Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-10-08
2001-11-20
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S825000, C029S842000
Reexamination Certificate
active
06317974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to contacts for microelectronic components such as semiconductor chips and associated circuit panels, connectors, sockets and related devices. Specifically, the present invention is directed to the forming of a wear resistant edge on the contacts on microelectronic components.
2. Description of the Related Art
Contacts for microelectronic components are typically formed from copper or other relatively soft or easily deflectable materials. The contacts engage terminals (such as pins or solder balls) on adjacent microelectronic components forming electrical connections. To improve the electrical connection, the contacts may wipe or otherwise abrade the pads or solder bumps as those elements are engaged, breaking through any oxide layer in order to electrically connect with the clean, un-oxidized material below.
Commonly assigned U.S. Pat. No. 5,802,699, the disclosure of which is hereby incorporated by reference herein, discloses a connector for mounting a microelectronic element to a substrate. In one embodiment, the connector has a body having a plurality of holes disposed in an array corresponding to an array of bump leads on the microelectronic device to be mounted. The connector also has an array of resilient contacts secured to the body in registration with the holes. Each contact is adapted to resiliently engage a bump lead inserted into the associated hole. An array of terminals are electrically connected to the contacts such that a microelectronic component can be connected to a substrate by bonding the terminals to the substrate and superposing the microelectronic element on the body. The bump leads on the component protrude into the holes and are engaged by the resilient contacts.
Certain embodiments disclosed in commonly assigned U.S. Pat. No. 5,632,631, the disclosure of which is hereby incorporated by reference herein, disclose microelectronic contacts having asperities to scrape a contacting solder ball or pad in order to break through the oxide layer. Preferably, the asperities are formed from beryllium copper or another conducting substance.
In many applications, microelectronic contacts and sockets are reused by removing one microelectronic element and replacing it with a second microelectronic element. For example, an assembly may be tested before bonding the contacts on the substrate to terminals on the microelectronic element. If the microelectronic element fails, it may be replaced by another microelectronic element, which is bonded to the substrate after passing the test. In another example, a substrate having sockets may be used as a test fixture for testing numerous successive microelectronic elements. In both cases, the sockets or contacts must withstand multiple wiping contacts with solder balls or pads on the microelectronic element.
Although the foregoing commonly assigned patents offer significant advantages, still further improvements in contacts are desirable.
SUMMARY OF THE INVENTION
The present application discloses a process for creating wear resistant edges for contacts. The wear resistant edge permits the reuse of the contact as described above without rapid degradation of the contact due to wear. Furthermore, the hard contact edge of the present invention enhances the wiping and scraping action that uncovers the underlying un-oxidized metal of the solder ball or pad.
The present invention relates to a method of making a contact having a wear resistant edge. The method of this aspect of the invention includes the step of providing a composite or laminate structure which includes a substrate and a conductive layer. A photoresist layer is then formed on the conductive layer. The photoresist layer is patterned to expose portions of the conductive layer. The exposed portions are etched to form contacts having etched edges. A wear resistant material is then plated onto the etched edges to form wear resistant edges. The patterned photoresist layer is then stripped. The top portion of each contact is then etched to a predetermined height which is below the height of the associated wear resistant edge so that the wear resistant etch protrudes above the surface of the contact.
The present invention also relates to a method making a contact having an aperture opening which is defined by a plurality of electrically conductive contact tabs. Each of the contact tabs has a wear resistant edge. The method of this aspect of the invention comprises the step of patterning a first photoresist layer which is disposed on the conductive layer of the composite structure. The conductive layer is etched to form a plurality of tabs. The edges of the tabs are then plated with a wear resistant material. The first photoresist layer is stripped and a second photoresist layer is formed on the conductive layer. The second photoresist layer is patterned to define the outline of the contact. The conductive layer is exposed to a second etching step to form the outline of the contact. The contact tabs are disposed within the outline of the contact. In preferred embodiments, the contact tabs are extend radially inward and form an aperture in the conductive layer. The top portion of each contact is also etched to a predetermined height which is less than the height of the associated wear resistant edge.
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Arbes Carl J.
Lerner, David, Littenberg, Krumhholz & Mentlik, LLP
Tessera Inc.
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