The Remarkable Return of Post-Reflow Cleaning as a Mainstream Process to Improve Reliability
Bibliographic record
Abstract
ABSTRACT Today, in modern times, society values cleanliness. The pandemic exaggerated the degree to which we desire, expect, and even demand cleanliness. Even in “normal times”, cleanliness is revered. We wash our bodies, dishes, cars, and pets. We expect cleanliness in our hotels and restaurants. We require cleanliness, to the point of sterility, in our operating rooms. In many public restrooms, we even hire people to inspect for cleanliness and publish inspection reports. Cleanliness has become a normal part of life, except in one aspect of our life. Part of our life that ensures our safety, prepares our food, transports us to work and play, monitors our health, and so much more. I'm referring to electronics. Once regarded as vital, the level of importance of a clean circuit assembly has been demoted. How did the cleanliness of circuit assemblies, once required, get shoved aside? There's one simple answer; the environment. During the 1980's, scientists discovered a “hole” in the Earth's ozone layer and attributed it to, among other things, chlorofluorocarbons (CFC's). In order to protect the ozone layer, or at least slow down the shrink-rate, a treaty was signed, referred to as the Montreal Protocol [figure 1], originally by eleven countries, that would phase out production, and consequently availability, of most CFC-based solvents within a ten-year time frame. That was 1989. By law, these CFC-based solvents would be no longer produced by 1999. The wildly popular cleaning/defluxing chemicals of the day were largely CFC-based and therefore subject to the ban. Necessity being the mother of invention, a new flux was introduced promising to leave behind an invisible and benign residue, not harmful to circuit assemblies. This new “noclean” flux would eliminate the cleaning requirement. Almost instantly, the electronic assembly industry switched to no-clean fluxes and abandoned their cleaning processes. While some high-reliability manufacturers such as military and medical maintained their cleaning processes, the majority of the industry exchanged their cleaning systems and processes for the promise of a “clean without cleaning” circuit assembly.
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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 | 0.013 | 0.016 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.005 |
| Scholarly communication | 0.005 | 0.007 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.005 | 0.007 |
| Insufficient payload (model declined to judge) | 0.016 | 0.007 |
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".