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Black Chromium as a Solder Dam

IP.com Disclosure Number: IPCOM000051058D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Block, ML: AUTHOR [+4]

Abstract

In the manufacturing of substrates for the mounting of integrated circuit chips, top surface metallization is applied to the substrate. Conventionally this metallization includes successively depositing a bottom layer of Cr, an intermediate layer of Cu, and a top layer of Cr. When the chip or chips are to be soldered by flip-chip bonding techniques, the top layer of Cr is removed by etching where the solder connections are to take place and is left in the remaining areas to act as a solder dam. Certain problems such as etch undercutting and striping have been encountered in removing the top layer of Cr in the desired areas.

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Black Chromium as a Solder Dam

In the manufacturing of substrates for the mounting of integrated circuit chips, top surface metallization is applied to the substrate. Conventionally this metallization includes successively depositing a bottom layer of Cr, an intermediate layer of Cu, and a top layer of Cr. When the chip or chips are to be soldered by flip-chip bonding techniques, the top layer of Cr is removed by etching where the solder connections are to take place and is left in the remaining areas to act as a solder dam. Certain problems such as etch undercutting and striping have been encountered in removing the top layer of Cr in the desired areas.

It has been found that if the process is modified and so-called "black chromium" is used as the top layer, these problems can be overcome and etch undercutting and striping can be eliminated. In this process, the bottom layer of Cr is deposited followed by the deposition of a Cu layer. At this point the desired circuit pattern is etched.

After the etching of the pattern, photoresist is applied to the sites on the pattern where soldering is to take place. Following this, black chromium is sputter deposited over the entire substrate. Black chromium is the product of a process wherein Cr is sputtered with 0(2) being bled into the system. It is actually a form of chromium oxide.

After the black chromium is applied, the photoresist is developed and this will remove the black chromium from Chose sites where soldering i...