The Return of Cleaning: Why Post-Reflow Cleaning is Becoming Mainstream Again

This is the first of a two part series.

For decades, cleaning circuit assemblies after soldering was not optional. It was standard practice across the electronics manufacturing industry. Then, almost overnight, that changed.

In this episode of Reliability Matters, Mike Konrad takes you back to the origins of that shift. From the widespread use of CFC-based cleaning solvents to the global impact of the Montreal Protocol, this episode explains how environmental regulation led to the rapid adoption of no-clean flux and the removal of cleaning as a standard process step. But that decision came with assumptions.
Assumptions based on larger components, wider spacing, and assemblies that were far more tolerant of residues than what we see today.

As electronics evolved, so did the risk.

Miniaturization, increased component density, and the expansion of electronics into harsh environments have dramatically reduced the tolerance for contamination. And when cleaning was removed, it wasn’t just flux that remained. It was the totality of residues introduced throughout the manufacturing process.

This episode walks through how those residues, combined with moisture and electrical bias, can lead to electrochemical migration, including parasitic leakage and dendritic growth, often resulting in delayed or intermittent failures.

This is the story of how we got here.

In Part 2, we bring this discussion into the present.

What does “clean” actually mean today? Why did the industry move away from fixed cleanliness limits? And why is cleaning once again becoming a critical part of modern electronics manufacturing?
If you’ve ever asked the question, “Do I really need to clean?” Part 2 will challenge how you think about the answer.