Control of “Spalling” in SAC Pb-Free Solder Alloys when used with a Ni Substrate
Bibliographic record
Abstract
ABSTRACT A basic feature of the formation of a solder joint is the occurrence of a single layer of intermetallic compound between the solder and the substrate on which the joint is made. However, under some conditions, such as repeated reflows, when a solder of the Pb-free SAC type is used with a nickel (or Ni(P)) substrate, a second layer of intermetallic compound is formed in the solder, near to but separated from the layer that is adjacent to the substrate. The appearance of this second layer of intermetallic compound is called “spalling” because it gives the impression that it was initially formed on the substrate and later displaced from that location by the introduction of a second intermetallic layer on the substrate. By consideration of the possible reactions that can occur during cooling of an SAC solder to which is added a small amount of Ni it is shown in this paper that spalling is accounted for as a nonequilibrium effect associated with a quasiperitectic reaction of the Cu-Ni-Sn alloy system. It is shown that the occurrence of spalling can be delayed to longer liquid holding times by an increase in the Cu content of the solder to a value greater than 0.6wt%. Attempts to control spalling by increasing the cooling rate of the solder to values as high as 4.7°C per second were not successful.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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".