Addressing the Problems with Ionic Cleanliness Testing on Modern Circuits
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,009 | 0,013 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,001 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,003 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,006 |
| Communication savante | 0,003 | 0,006 |
| Science ouverte | 0,004 | 0,003 |
| Intégrité de la recherche | 0,002 | 0,003 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,004 | 0,002 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».