wire

**Wire Bond Packaging** is **connecting die pads to package leads via thin wires enabling electrical contact at lowest cost** — most mature, highest-volume technology. **Wire Materials** gold (standard; no oxidation); copper (cost-advantaged; oxidizes). **Wire Diameter** 12.5-25 μm (fine-pitch), 50-75 μm (high-current). **Loop Height** sag under gravity; 100-500 μm typical. **First Bond** die pad (Al) ultrasonic or thermocompression bonded. **Second Bond** package lead bonded similarly. **Ultrasonic** mechanical vibration (~60-120 kHz) + pressure. Breaks oxides. **Thermocompression** heat (100-250°C) + pressure. Temperature aids flow. **Thermosonic** temperature + ultrasonic (modern standard). **Bond Force** 50-200 grams-force typical. Sufficient bond, don't damage die. **Dwell Time** 1-10 ms at bond site. Longer: stronger bond; reduced throughput. **Tail Trimming** excess wire cut mechanically. **Pull Strength** post-bond test: pull wire; measure force. Typical 10-30 grams-force. **Tensile Strength** wire itself ~100-300 MPa. Over-pulling breaks wire. **Wedge** wedge-shaped tool; used for fine-pitch Al. **Ball** ball-shaped; stitch bonds (multiple). **Quality** defects: cold weld, lifted wire, contamination. **Thermal Cycle** −40 to +125°C stresses wire at interface. **Electromigration** high current in thin wire causes atomic diffusion. Void formation. **Moisture** entrapped moisture → popcorn effect (explosive expansion on reflow). Pre-bake critical. **Corrosion** copper bondwires corrode (halides). Gold immune. **Intermetallics** Cu-Al forms brittle IMC if excessive. **Wire bonding remains highest-volume** due to cost and proven reliability.