Browse Prior Art Database

Pin Attachment Technique and Structure

IP.com Disclosure Number: IPCOM000052865D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Phelps, DW: AUTHOR [+3]

Abstract

In the attachment of pins to ceramic or plastic substrates on which silicon chips are mounted, it is necessary to obtain a good, reliable, strong bond of the pins to the top surface metallization or to metal-filled vias. This article describes an improved technique and resulting structure which minimizes failures of pin attachment due to substrate cracking and maximizes the strength and reliability of pin attachments to a substrate.

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Pin Attachment Technique and Structure

In the attachment of pins to ceramic or plastic substrates on which silicon chips are mounted, it is necessary to obtain a good, reliable, strong bond of the pins to the top surface metallization or to metal-filled vias. This article describes an improved technique and resulting structure which minimizes failures of pin attachment due to substrate cracking and maximizes the strength and reliability of pin attachments to a substrate.

Fig. 1 is an exploded view of a substrate having a cap positioned to be attached to provide an improved structure for having a pin welded thereto. The substrate has a tungsten- or molybdenum-filled via overlaid with a surface pad of the same material. Plated onto the top of the surface pad is a thin layer of nickel and a very thin layer of gold.

The metal cap is comprised of a thick layer of copper and a thinner layer of a good brazing material, such as LITHOBRAZE* (a eutectic alloy of copper and silver with a trace of lithium).

The cap is placed in contact with the surface pad of the substrate, and the assembly placed in a furnace at brazing temperature (about 900 Degrees C A brazed interconnection is formed, as shown in Fig. 2. The resulting structure is a relatively thick layer of copper, a layer of braze material formed from the lithobraze, the gold, and the nickel, and a layer of molybdenum or tungsten. A pin can be welded to thinas structure by percussive or other welding techniques and wit...