WireBondingSummary

The Nordic Electronics Packaging Guideline Chapter A: Wire Bonding 1 LIST OF CONTENTS 1. LEVEL 1. INTRODUCTION OF WIREBONDING TECHNOLOGY.2 1.1 WHAT IS WIREBONDING.2 1.1.1 Wirebonding processes2 1.1.2 Wirebond s.2 1.3 HISTORY AND APPLICATIONS3 1.4 COST3 1.5 LIMITATION OF WIREBONDING.4 2 LEVEL 2. CONCLUSIONS AND GUIDELINE.4 2.1 WIREBONDING TECHNIQUES.4 2.1.1 Ball bonding4 2.1.2 Wedge bonding5 2.2 WIRES AND TYPICAL METALLURGICAL SYSTEMS5 2.2.1 Wires usually used in wirebonding.5 2.2.2 Metallurgical systems6 2.3 BODING EQUIPMENT8 2.3.1 Wirebonder.8 2.3.2 Bonding tools8 2.4 WIREBONDING GUIDELINE9 2.4.1 Process optimization.9 2.4.2 Wirebonding design.10 2.4.3 Bond uation12 2.5 FAILURE MECHANISMS OF WIREBONDS.16 2.5.1 Failure shooting16 2.5.2 Pad cleanliness.16 2.5.3 Bonding failures17 2.5.4 Reliability failures.18 3 LEVEL 3. BACKGROUND INATION (LINKS).20 3.1 REPORT20 3.2 PUBLICATION.FEL! BOKMÄRKET ÄR INTE DEFINIERAT. 4 REFERENCES.20 2 Wirebonding 1.Level 1. Introduction of wirebonding technology This guideline is concerned with wirebonding technology, which affords the fundamental knowledge and the practical applications to those who are using this technique as well as those who are interested in this technique. This guideline is divided into different levels according to reader’s requirements. 1.1What is wirebonding Wirebonding is an electrical interconnection technique using thin wire and a combination of heat, pressure and/or ultrasonic energy. Wirebonding is a solid phase welding process, where the two metallic materials (wire and pad surface) are brought into intimate contact. Once the surfaces are in intimate contact, electron sharing or interdiffusion of atoms takes place, resulting in the ation of wirebond. In wirebonding process, bonding force can lead to material deation, breaking up contamination layer and smoothing out surface asperity, which can be enhanced by the application of ultrasonic energy. Heat can accelerate Interatomic diffusion, thus the bond ation. 1.1.1Wirebonding processes Wirebonding process begins by firmly attaching the backside of a chip to a chip carrier using either an organic conductive adhesive or a solder (Die Attach). The wires then are welded using a special bonding tool (capillary or wedge). Depending on bonding agent (heat and ultrasonic energy), the bonding process can be defined to three major processes: thermocompression bonding (T/C), ultrasonic bonding (U/S), and thermosonic bonding (T/S), as shown in Table 1-1. Table 1-1. Three wirebonding processes. WirebondingPressureTemperatureUltrasonic energyWirePad ThermocompressionHigh300-500 oCNoAu,Al, Au UltrasonicLow25 oCYesAu, AlAl, Au ThermosonicLow100-150 oCYesAuAl, Au 1.1.2Wirebond s There are two basic s of wirebond: ball bond and wedge bond, the corresponding bonding technique, bonding tool and materials are listed in Table 1-2. Currently, thermosonic gold ball bonding is the most widely used bonding technique, primarily becau