Room-Temperature Bonding with Pd Coated Cu Wire on Al Pads: Ball Bond Optimization with 2-Stage Methodology
Bibliographic record
Abstract
Wirebonding performed at elevated temperatures is the standard interconnect process for integrated circuits, typically with the use of low-cost copper bonding wire. However, for specific applications it is necessary for wire bonds to be reliably joined at room-temperature. This paper details the development of a room-temperature ball bonding process using a 2-stage optimization method. The first stage optimizes ball geometry by applying a 32 design of experiment to bonding parameters impact force (IF) and electric flame-off (EFO) current. In the second stage bond shear strength is optimized by stepwise increase in ultrasonic amplitude. Target ball bond values were attained at optimized parameters: IF of 1331 mN, EFO current of 59.9 mA, and an ultrasonic amplitude of 26.46 US%. Pad lift during bonding was observed at excessive ultrasonic amplitudes above 40 US%, as determined by optical images at the bond interface. Bonding parameters at room-temperature (23°C) were increased when compared to a high temperature process (175°C) to account for reduced thermal energy. For the same geometry at room-temperature a 7 % increase to impact force was required. EFO current levels remained relatively constant between the two bonding temperatures. For the same shear strength at room-temperature a 18 % increase in ultrasound amplitude was required. The confirmed average shear strength achieved via the room-temperature process was 116 MPa. Higher values are possible.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".