Addressing the Problems with Ionic Cleanliness Testing on Modern Circuits
Bibliographic record
Abstract
ABSTRACT ROSE Testing – A Historical Perspective Shortly after the electronic circuit card replaced point to point wiring in the 1950's, the reliability of manufactured circuit assemblies was directly linked to the amount of “freely” ionizable material remaining on the board following assembly. These residues in the presence of moisture and a voltage differential will undergo both chemical and dendritic electrochemical reactions resulting in rapid and catastrophic circuit failure. In response to several high profile space and military systems failures in the 1960's, the US Military developed and incorporated the “Resistance of Solvent Extract” test or as it became commonly known as the ROSE test. The ROSE test initially was performed manually using a procedure in which a known volume of clean solution of 75% IPA and 25% purified water was sprayed onto the assembly being tested and collected in a clean beaker. The resistance of the soiled solution was measured and compared to standard NaCl solutions. Based upon final resistance, the amount of NaCl equivalent on the test assembly could be determined with some accuracy. The amount determined to be present was divided by the area of the circuit being tested and an average ionic contamination was determined. A limit of no more than 10 micrograms per square inch, or 1.56 micrograms per square centimeter, was set based upon test data and reliability data from failed units. This remains the default standard today. Automated testing machines became available and replaced the manual method. The ROSE method quickly gained acceptance and was incorporated in the US military specification, Mil-P-28809 in 1971 1 . From that point forward, virtually all US contracts to build electronic hardware required that a sample board be pulled from normal production and a daily ROSE test performed. Everything got more complicated in the 1980's with the introduction of SMT assembly design because the flux in solder paste got a lot more complicated. Viscosity modifiers and thixotropic agents were added to improve printability. Tack extending agents and anti-slump compounds are present to keep things in place until the reflow soldering process heats and melts the solder. All these additions make cleaning and cleanliness testing more difficult. In 1990 the Montréal protocol was enacted and stopped the production and use of the primary class of cleaning agents being used. In response the Industry developed a new class of fluxes referred to as “No-clean fluxes”. This gave license to the flux and solder paste formulators to put things in that cannot be cleaned or at the very least were difficult to clean. Cleaning and testing got even more difficult with the introduction of higher temperature “lead free” solders which expose flux residue to a longer and hotter assembly profile. Through all of this, the ROSE test protocol remained virtually unchanged for 50 years. Confidence in the cleanliness test has eroded significantly because of concerns about dissolving and measuring the “right stuff”. ROSE testing is still required on most high reliability electronic build contracts because there is no better method which is practical in production. Figure 1 shows the evolution of cleaning and testing.
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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 | 0.009 | 0.013 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.006 |
| Scholarly communication | 0.003 | 0.006 |
| Open science | 0.004 | 0.003 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".