Browse Prior Art Database

Tinning Metal Pads on a Nonwettable Substrate

IP.com Disclosure Number: IPCOM000085840D
Original Publication Date: 1976-Jun-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Hafner, B: AUTHOR [+2]

Abstract

In modern circuit technology metal pads to be solder-coated are arranged on nonwettable substrates. During the tinning of the pads, for example, in a soldering bath, a spherical protrusion of solder limited to the area of the pads and defined with regard to its outer shape and quantity of solder it contains, is formed as a result of the surface tension and the areal extension of the pads.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 99% of the total text.

Page 1 of 2

Tinning Metal Pads on a Nonwettable Substrate

In modern circuit technology metal pads to be solder-coated are arranged on nonwettable substrates. During the tinning of the pads, for example, in a soldering bath, a spherical protrusion of solder limited to the area of the pads and defined with regard to its outer shape and quantity of solder it contains, is formed as a result of the surface tension and the areal extension of the pads.

A method of increasing the quantity of solder collected by a pad, without increasing the area required, is used to tin the surface pads of a processed Si wafer. The quantity of solder required per wafer is greater than that obtainable by mere tinning.

Film 3 of a suitable metal is vapor deposited on pad 1, predetermined with regard to its areal extension and arranged on nonwettable substrate 2. Film 3 overlaps pad 1, and the areal extension of the film determines the future volume of solder on pad 1. Film 3 is tinned in an orthodox manner, whereby a spherical solder protrusion 4 limited by film 3 is formed (Fig. 2).

In a subsequent heating step (reflow), film 3 dissolves in the liquefied solder of spherical protrusion 4. The total quantity of solder formed recedes to the original nonsoluble pad 1, forming spherical solder protrusion 5 of the volume required (Fig. 3).

Pad 1 can be produced, for example, by chromium-copper-gold vapor deposition. Layer 3 can be made of copper.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-...