Thermosonic Bonding Gold Bumped Die

The substrate is placed on a stage heated to approximately 150°C and mechanically clamped.  The die is picked from a waffle pack or gel pack and the bumps are aligned with the bond pads on the substrate.  The die is brought in contact with the substrate and a bond load in the range of 20-80 grams per bump is applied.  Ultrasonic energy is applied and the gold bumps are fused to the bonding pads.  Underfills are not normally applied in this process.

A heated stage with mechanical clamps to firmly hold the substrate in place is required.  The stage must be capable of heating to 150°C.  Additional spot heating may be required when using substrates that cannot transfer heat well to the bonding area.  In this instance, a spot heating system is needed to deliver topside heating and raise the bonding surface to the desired temperature.  A heater attached to the bonding tool may also be used, but these tend to interfere with the ultrasonic action.

A holder that can present waffle or gel packs is needed for die pick-up.

A die bonding collet with vacuum is required to pick die and securely hold it during the bonding process.  Because of the ultrasonic motion, a four-sided collet with an inverted pyramid shaped opening is best suited to accurately capture the die.  The pick and place mechanism must be capable of picking the die with the collet and placing it accurately while applying a bond load of up to 3Kg and perhaps more depending on bump count.

An ultrasonic generator and transducer capable of 60Khz and up to 40W of power is needed to apply ultrasonic motion.

A vision system that shows the substrate pad and die bump alignment is required along with a means to make fine adjustments to achieve correct alignment.  Use of a microscope with an appropriate lighting system is helpful in process observation and optimization.

Several types and sizes of workstages are available. The selection is based on various substrate characteristics. All stages have mechanical clamps available to hold substrates securely in position (custom machining may be required). The stages can maintain temperatures up to 350°C and are closed loop controlled by the system computer.

An optional hot gas spot heating system for topside heating of the substrate is available with one or two retractable nozzles.

All three models come equipped with a die tray pedestal capable of holding a mirror, waffle pack or gel pack for die pick-up.

A cube beam splitter, color camera, zoom lens, and monitor are provided for alignment of bumps to pads. An optional direct view microscope is available on all models for a direct view of the bonding process as it happens.

Ultrasonic energy comes from the Uthe transducer and 40 watt power supply. Z motion is closed loop servo controlled with a strain gauge for bond load control. A computer controls most system functions.

• Model 410XP Precision Bonder or Model 410 Flip Chip Aligner/Bonder or Model 860 Omni Bonder.
• Ultrasonic Bond Head and vacuum pick-up tool.
• Heated Workstage with mechanical clamp.

• Leica Stereo Zoom Scope and ring light illuminator.
• Single or Dual Hot Gas System.
• Table for Model 860.