Microstructures Resulting from the Use of Solder Balls of One Composition with Paste of a Different Composition on a Copper Substrate
Bibliographic record
Abstract
ABSTRACT With the development and use of a variety of Pb-free solders, it is probable that some solder joints in electronic assemblies may be made with solders of two different compositions, one of which may be eutectic Pb-Sn. To investigate some possible resulting microstructures, small balls of four different SAC Pb-free solders were each melted with eutectic Pb-Sn solder paste, as well as with various SAC pastes, on a copper substrate. Two paste levels were used, 20 and 29 weight percent of the total sample weight. In all cases, the sample was held for 90 seconds at a temperature above the melting point of the solder paste. For samples made with PbSn paste, two different values of maximum temperature were used, 210°C and 220°C, while for samples made with SAC paste, the maximum temperatures used were 235°C and 245°C. The resulting microstructures were evaluated metallographically using both optical and scanning electron microscopes. It was observed that the use of Pb-Sn solder paste introduced some Pb-Sn eutectic microstructure and changed the ternary eutectic present from Ag 3 Sn-Cu 6 Sn 5 -Sn, normally observed in SAC alloys, to Ag 3 Sn-Pb-Sn. The high Sn content of the SAC alloys used led to rapid dissolution of the copper substrate, often resulting, on cooling, in formation of primary Cu 6 Sn 5 crystals and Cu 6 Sn 5 -Sn binary eutectic regions. Similar experiments were also carried out using balls of the Sn-Zn-Al solder alloy.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".