Ionic Contamination Debate Highlights Growing Divide in Automotive Electronics

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A recent Global Electronics Association panel discussion revealed both broad agreement and sharp differences regarding one of electronics manufacturing’s most persistent reliability questions: How clean is clean enough?

The discussion, focused on ionic contamination assessment in electronic control unit (ECU) manufacturing, brought together the following experts:  Tim Dietz from Ford Motor Company, Dr. Lothar Henneken from Robert Bosch, Eric Camden from Foresight, Hubertus Mertens from MKS’ Atotech, Doug Pauls from It Depends Electronics, and Stan Rak from SF Rak Company, as moderator. While everyone agreed that contamination control is essential for long-term reliability, panelists differed significantly on whether ion chromatography (IC) should play a larger role in production acceptance and process control.

At the center of the discussion was the industry’s shift away from universal cleanliness limits. For decades, electronics manufacturers relied on the well-known ROSE (Resistivity of Solvent Extract) limit of 1.56 micrograms sodium chloride equivalent per square inch. That limit was ultimately removed from IPC J-STD-001 because experts concluded that a single cleanliness threshold could not adequately address the wide range of electronic products, operating environments, and reliability requirements found across the industry.

That change continues to influence how manufacturers approach contamination today. Pauls shared his belief that “ROSE testing is still acceptable as a process control tool, but you have to understand what the number means and what it’s telling you.”

Camden emphasized that cleanliness limits should be based on objective evidence generated through reliability testing. Rather than adopting universal thresholds, manufacturers should establish their own acceptance criteria through methods such as surface insulation resistance (SIR) testing, temperature-humidity-bias testing, and product-level environmental validation.

The debate becomes more complicated when ion chromatography (IC) enters the picture.

Unlike ROSE testing, which provides a general measure of contamination, IC identifies individual ionic species and can pinpoint specific contamination sources. That capability makes IC a powerful tool for root-cause analysis and troubleshooting. Several panelists acknowledged its value when investigating failures, qualifying suppliers, or assessing process changes.

Dietz offered a practical example. He described three significant quality issues that were ultimately traced to contamination-related causes. By conducting contamination analysis and implementing process improvements, Ford and its suppliers eliminated the problems and dramatically reduced customer returns. For Dietz, the data support the value of contamination monitoring as part of a broader quality strategy.

Yet Henneken pushed back strongly against the growing trend of applying fixed IC limits to automotive manufacturing. He argued that extraction-based measurement techniques do not directly predict reliability and may produce misleading results when applied to modern no-clean assembly processes. Dietz then commented, “Localized extraction tells you right where to go. What process built that part of the board? What components are there? And start troubleshooting away.”

Henneken cited examples in which IC detected contamination levels exceeding published limits, yet similar products have accumulated 1.5 billion field operating hours without widespread reliability problems. He warned that overly restrictive limits could unintentionally disqualify proven technologies, materials, and manufacturing processes.

Another concern raised during the discussion involves measurement variability. Panelists noted that contamination results can change significantly depending on extraction solvents, analytical methods, sample preparation techniques, and even the laboratory performing the analysis. That variability creates challenges for anyone attempting to establish universal acceptance criteria.

Henneken said, “This is one example from boards that I have sent to three different laboratories, and I have got three different results.” Mertens picked up on that point a bit later when he shared, “You need to be very careful in what you do, and you need to evaluate your own measurement tool.”

For the PCB manufacturing and assembly community, the implications are significant.

As automotive electronics expand into safety-critical applications, OEMs are demanding greater confidence in long-term reliability. At the same time, suppliers are seeking practical, repeatable, and cost-effective methods for monitoring manufacturing processes. The challenge is finding the balance between analytical rigor and production reality.

Perhaps the most important takeaway for is that the industry is moving toward evidence-based qualification rather than reliance on simple pass-fail cleanliness numbers. Whether manufacturers use ROSE, localized contamination testing, ion chromatography, or a combination of methods, panelists repeatedly emphasized that contamination data must be correlated with demonstrated reliability performance.

The consensus was that there is no universal cleanliness number that guarantees reliability. Camden summed it up, “There are no one-size-fits-all limits for cleanliness, and nor should there be.” Pauls said, “You would not have the same cleanliness metric for a garage door opener as you would for a heart pacemaker.”

Understanding the product, the process, and the operating environment remains the foundation of contamination control, and likely will for years to come.