Wire Bump Material

Abstract

The present invention was held in order to resolve problems on above-mentioned conventional wire bumping material. This invention has the following purposes; (1) approximating Au—Ag alloy bumping balls to bond Al pads to ideal sphere shape (2) increasing assurance of Au—Ag alloy bump bonding to Al pads (3) shortening tail length of Au—Ag alloy bump (4) improving anti-Au consumption into solder (5) decreasing contamination of capillary tip by bump wire and hole around tip Means for resolution Au—Ag alloy for wire bumping comprising wherein Au, which purity is more than 99.99 mass %, comprising Au matrix and a particle of additive elements, consisting of 1 to 40 mass % Ag, which purity is more than 99.99 mass %.

Description

[0001] This application is based on Japanese Patent Application No. 2004-287599, filed on Nov. 30, 2004, the entire contents of which are incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to metal alloy or material for wire bumping to form bump, using wire bonding technique. STATE OF THE ART [0003] Conventionally, it is known that method of forming metallic bump, using wire bonding method, bonding with electrodes on the IC chips or transistors and leads of TAB (Tape Automated Bonding), lead frames and / or outer terminals on ceramic substrates. This wire bumping method has an advantage to manufacture high density packages and thin type packages, because of direct bonding to electrode pads on IC chips and outer terminals through bump and lower height of bonded part comparing with a case of using wire-bonding. For example, there are flip chip method, forming bumps on electrodes of IC chip in advance, bonding with these bumps against molten sol...

AI Technical Summary

Benefits of technology

The present invention provides a solution for improving the performance of conventional Au alloy for wire bumping. The invention focuses on approximating the shape of bumping balls to bond Al pads, increasing the assurance of bump bonding, shortening the tail length of bumps, improving anti-Au consumption into solder, and decreasing contamination of the capillary tip. The invention provides various wire bumping materials, including an Au—Ag alloy with specific additives such as Ca, Be, rare-earth elements, and other elements. The invention also provides specific alloys for bonding to Pb matrix solder or Sn matrix solder, as well as for flip chip bonding to Pb-free Sn matrix solder with a melting point of 170°C to 260°C. Overall, the invention enhances the performance and reliability of wire bumping processes.

Problems solved by technology

Whereas in the case of using high purity Au, after ultrasonic bonding to IC chip forming balls on ultra fine wire in advance, tearing off a part of the wire held with a clamp, problem occur that tails, which is principal cause of incorrect contact, remained on the side of bumps, namely on remained balls of IC chips.

However, genus of platinum, like Pd, etc. is very expensive, moreover it is necessary specific facilities and more expensive comparing with Au, conventionally had been used as purity of 99.9% Au, which contained much impurities.

Moreover, increasing additives of genus of platinum, inside of capillary is contaminated, and this contamination make non-spherical ball attached to wire, and balls become harder and Si chip is broken under Al pad, for such problems, practically, it had been used Au-1% Pd alloy.

When operating temperature become higher temperature, phenomena of solder consumption occur, namely Au rapidly melt into solder, it is forced to operate soldering under strict temperature control.

Though Au-5% Pd alloy has been studied, ball bonding in the air, because of forming hard balls, problem of grater chip damage against Al pad, and problem of big fluctuation of Pd market price, said capillary contamination and length of tails, it had not been in practical use.