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36 SMT007 MAGAZINE I NOVEMBER 2026 ROSE also does not reveal where residues are located. A small amount of contamination trapped beneath a bottom-terminated component may pose a significant reliability risk, while a much larger amount distributed elsewhere on the board may be relatively harmless. ROSE averages everything together into a single bulk result. Perhaps most importantly, ROSE does not directly measure electrical reliability. A board can produce a low ROSE number and still experience electrochemical migration, corro- sion, insulation resistance degradation, or dendritic growth under service conditions. Conversely, a board may produce a relatively high ROSE result and still perform acceptably in its intended environment. The relationship is not always straightforward because reliability depends on many factors, including residue chemistry, location, moisture exposure, electrical bias, assembly design, and operating conditions. This reality is one reason IPC cleanliness require- ments evolved away from universal ROSE limits and toward objective evidence approaches centered on actual reliability testing. Why the Industry Changed Its Thinking Historically, the famous 1.56 µg/cm² sodium chloride equivalent limit became widely accepted as a clean- liness benchmark. For many years, passing this limit was often viewed as evidence that a product was clean enough for service. Modern electronics changed the equation. Assemblies today contain smaller geometries, lower standoff components, denser packaging, and more complex chemistries than the assemblies for which many of the original cleanliness assumptions were developed. Modern flux residues may be only partially extractable, highly localized, or chemically different from the contaminants that dominated reli- ability concerns decades ago. As a result, IPC-J-STD-001 evolved toward an objective-evidence model. Surface insulation resis- tance (SIR) testing became the preferred method for demonstrating that residues do not adversely affect reliability under temperature, humidity, and electrical bias conditions. ROSE remains valuable, but primarily as a process-monitoring tool rather than a qualification tool. The Appropriate Use Case for ROSE The best way to think about ROSE is as a process control instrument, not a reliability predictor. An ideal approach looks something like this: First, qualify the manufacturing process using objective evidence such as SIR testing, environmental testing, historical reliability data, or other appropriate methods. Establish that the process consistently produces assem- blies suitable for the intended service environment. Next, measure the corresponding ROSE values produced by that validated process. These values become your baseline. Once those process-control limits are estab- lished, ROSE becomes extremely useful. If future production runs begin generating ROSE values that fall outside the validated range, the manufacturing team knows something has changed and can inves- tigate before larger problems develop. In this model, SIR tells us whether the process is acceptable. ROSE helps us determine whether the process remains consistent. The Clean Truth ROSE testing has survived for decades because it provides something manufacturing engineers desperately need: fast feedback. It is inexpensive, practical, and sensitive enough to detect mean- ingful process changes. The mistake is expecting it to do more than it was designed to do. ROSE measures extractable ionic contamination. It does not identify contaminants, locate contami- nants, or directly predict reliability. It should not be used as standalone evidence that a manufacturing process is qualified for high-reliability electronics. When used as a process-control tool anchored in a validated cleanliness program, ROSE remains one of the most useful measurements available to elec- tronics manufacturers. When used as a universal pass/fail indicator of reliability, it can be misleading. That's the clean truth. SMT007 Dr. Adam Klett is director of science at KYZEN. To read past columns, click here. T H E C L E A N T R U T H