Copper (Cu) wire has long been used as a method of connecting a silicon die to the package terminals. With the recent increase in Gold (Au) wire cost, Copper (Cu) wire is an attractive way to manage overall package cost.
Copper (Cu) Wire Benefits
Copper (Cu) wire offers significant cost advantage over Gold (Au) wire. It is also an excellent replacement for Gold (Au) wire due to its similar electrical properties. Self inductance and self capacitance are nearly the same for Gold (Au) and Copper (Cu) wire and Copper (Cu) wire has lower resistivity. In applications where resistance due to bond wire can negatively impact circuit performance, using Copper (Cu) wire can offer improvement.
Wire Material Cost Savings Copper (Cu) versus Gold (Au)
Production Status
Amkor is currently running Copper (Cu) wire production on multiple package platforms and in multiple factories.
Assembly Yield with Copper (Cu) Wire Approaches Yield with Gold (Au) Wire
Amkor has over 4,000 newer model bonders which may be converted for Copper (Cu) wire bond. Potential capacity equates to 120 million CSPs / week based on 100 wires per package. Current 2010 plans are to upgrade over 700 bonders for Copper (Cu) wire bond with additional conversions based on customer demand.
Wafer Technology Node and Copper (Cu) Wire Readiness
| >90nm | 90nm | 60nm / 65nm | 45nm / 40nm | |
|---|---|---|---|---|
| non-Low-K or Low-K | Both | Low-K | Low-K | Low-K |
| Rel Status | SQC / SQB & Eng Evals | Passed | Passed | Eng Eval |
| HVM | non-Low K | Yes | Yes | Development |
Considerations for Copper (Cu) Wire Bond
- Larger bond pad opening (BPO) is recommended
- Minimum 4um larger than for same diameter Au wire
- Copper (Cu) wire has greater tendency to “splash” out due to higher bond force
- Copper (Cu) wire bond success is highly dependent on silicon structure
- Amkor has compiled engineering data on many bond pad structures – Not easy to generalize
