Improving solder wettability atop screen-printed copper for flexible hybrid electronic circuit assembly
Bibliographic record
Abstract
Abstract Poor wettability of solder paste on printed copper (Cu) surfaces presents a significant limitation towards the reliable assembly of flexible hybrid electronic (FHE) circuits. This work addresses this challenge using a low-melting-point, bismuth-based solder on nanoparticle-based copper ink pads serigraphically printed on flexible polyimide. To improve solderability, we introduce a surface treatment involving mechanical polishing of the printed copper with sodium bicarbonate (NaHCO [t]3 ) to reduce surface porosity and remove organic residues. This treatment enhanced solder wettability by 66%, leading to superior component alignment and assembly quality. The fabricated circuits prove highly robust and withstand a 1000 h accelerated aging test at 85 ∘ C and 85% relative humidity. Cross-sectional analysis confirms formation of a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>1.5</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mo>±</mml:mo> <mml:mstyle scriptlevel="0"/> <mml:mn>0.5</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> m thick intermetallic layer, indicative of an industrial-quality FHE circuit.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 0.000 |
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 teacher head, 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".