Effect of Solder Alloy, Aging and Tal on High Strain-Rate Fracture of Lead-Free Solder Joints
Bibliographic record
Abstract
ABSTRACT Fracture experiments at a strain rate of 30 s -1 and a loading phase angle of 38˚ were performed using Cu-solder-Cu double cantilever beam (DCB) specimens of 2 mm long discrete solder joints with a thickness of 150 μm. Three different lead-free solder compositions, SAC305, SAC0807 and SAC0307, were examined using a drop tester. Some specimens were aged at 100˚C for 300 h to assess the effect of aging, while the effect of the time above liquidus (TAL) was investigated using values of 120 s and 240 s. These parameters were of interest since they can change the microstructure and fracture behavior of solder joints. The failure of the solder joints in the DCB specimen was apparent as a distinct peak in the output of a strain gage that was bonded to the lower arm of the specimen at the location of the solder joint. This maximum strain at break was used to find the corresponding failure load using a finite element model (FEM) of the DCB. The critical strain energy release rate for crack initiation, J ci , of the solder joint was then calculated using the FEM. The standard deviation of J ci obtained from different test batches was between 11% and 18% of the mean value. Although other studies showed that these parameters significantly affected on fatigue life and reliability of solder joints, a statistical analysis on multiple repeat tests showed that the mean values of J ci were essentially the same for the three solder alloys, and were unaffected by either the aging or the change in TAL.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| 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 | 0.000 | 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".