The Remarkable Return of Post-Reflow Cleaning as a Mainstream Process to Improve Reliability

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.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.