Ultrasonic Wire Bonding & Wedge Bonding Prepress CAM Vector Guide

Master acoustic energy density, loop kink coordinates, and micro-pad vector design for high-yield semiconductor assembly.

1. Semiconductor Microelectronic Wire Bonding Fundamentals

Ultrasonic wedge bonding and thermosonic ball bonding are the dominant microelectronic interconnection techniques for hybrid microcircuits, multi-chip modules (MCM), RF power transistors, and power electronics IGBT/SiC modules. Gold (∅ 18–33 µm), Aluminum-Silicon (1% Si, ∅ 25–50 µm), and Copper wires are joined to metallized pads via solid-state acoustic scrubbing without melting.

2. Mathematical Mechanics of Ultrasonic Scrubbing

The ultrasonic transducer vibrates at 60 kHz to 140 kHz, transmitting tangential shear displacement ($A_{scrub} = 1.0 - 4.5\text{ µm}$) to break native aluminum oxides ($Al_2O_3$) and expose pristine metallic lattices:

Excessive scrub power causes heel cracking and silicon cratering beneath the bond pad, while insufficient scrub leads to non-sticking and high interfacial contact resistance.

3. Wire Loop Profiling & CAM Vector Toolpaths

4. Prepress CAD/CAM Rules for Wire Bonding Pad Geometries

• Bond Pad Pitch: Maintain minimum $W_{pad} \ge 1.75 \times d_{wire} + 15\text{ µm}$ to ensure the capillary or wedge tool does not encroach on passivation edges.
• Loop Apex Clearance: Maintain $> 125\text{ µm}$ clearance above silicon die edge chamfers to prevent dielectric breakdown during mold encapsulation.
• DXF Bond Vector Normalization: SpotItLive Vector Studio automatically extracts centerline bond trajectories, calculates kink coordinates, and creates verified keep-out zones for automated bonders (Kulicke & Soffa, Hesse, ASM).