Two Terrifying Cleaning Questions

We were helping a client set up cleaning evaluations at a provider of cleaning equipment; and the client received a questionnaire asking for details. The first question: what manufacturing steps occur before the cleaning process to be evaluated? The second question: what’s the next step in manufacturing after the cleaning process to be evaluated? These are two reasonable, logical questions – we ask similar questions of our clients. Unfortunately, attempting to answer these questions often strikes terror into the hearts of components manufacturers.

Take a deep breath – don’t be terrified! Tackle the questions and you will decrease product failure and build customer satisfaction. Answering these questions is important for manufacturers involved in metal finishing, for those involved in optics fabrication, and for electronics assemblers.

Suppliers
The client we mentioned is developing a new cleaning process for a critical product containing metals and polymers. Very high levels of cleanliness (very low levels of soil) are a customer requirement. There’s a supply chain. Supply chains are often complex; processes (not just cleaning processes) are often not defined.

Manufacturers who choose suppliers based on price alone often get just what they pay for – aggravation! The cleaner the parts and the more consistent the soil or soil residue, the easier it is to obtain a reliable cleaning process. Part of this effort involves understanding, communicating with, auditing, defining, and collaborating with (or, less desirable, controlling) suppliers of parts and components. This exercise includes uncovering potential problem soils and problem processes.

Become a Curator
Curate your suppliers. It’s sort of like some “foodie” restaurants or farmers markets where you are informed about the soil properties and watering practices of the tomato being offered. How do you curate suppliers? Ask questions and look at the genealogy of the parts and components. Specifying that components be produced by Company “N” may not tell the whole story in terms of contamination. Company “N” may outsource half a dozen processes; and if there is inadequate control in the outsource processes, chaos can ensue. At BFK Solutions, we are always happy to help clients eliminate chaos and improve yield; we’re even happier when we can help you avoid the chaos in the first place.

Knowing the “as received” cleanliness of parts can be valuable in simplifying the cleaning process and in achieving a consistent cleaning process. “As received” cleanliness is not considered as often as it might be. Some companies assume the worst and as a matter of course practice 100% cleaning of incoming parts, perhaps using a mild alkaline cleaner with several rinses; we see this practice in some medical device and aerospace applications. This can lead to a false sense of security. Are they doing enough cleaning? Are they verifying cleanliness? Is the verification process effective? It is often not apparent. Performing well-defined testing, like particulate level and non-volatile residue, can help in selecting optimal suppliers.

What if you have zero control over the supply chain?
In some cases – for example, if you are a contract manufacturer – you have no control over the parts as received, because the customer supplies the parts. You have to cope with soil levels that are variable and beyond your control, you may see heated or cured residue. You can’t tell the customer how to process the parts; but you are in charge of successfully coating or deposition or plating or painting. There are several strategies to achieve optimal cleaning. Some contract manufacturers run cleaning evaluations with “worst case” examples of incoming product. A few contract manufacturers charge more to process parts that are heavily-soiled. Some contract manufacturers elect to use very aggressive cleaning with solvents. Based on decades of experience, it seems inevitable that the more effective the cleaning solvent, the more likely there are to be worker safety and environmental issues. Clients that successfully manage aggressive solvents do so by controlling the process to achieve superb solvent containment.

Fixing Problems
Suppose there is a problem. We can and must look at the cleaning process. It is also important to determine what happened before cleaning and what happens after cleaning. Answering these questions is essential in root cause analysis; and, even more important than pointing fingers, in fixing the problem and preventing the problem from happening again in the future. For example, if there is coating failure on a metal part, the cleaning process may have been modified or “improved” to something that no longer works. The coating fabricator may have changed metalworking fluids and/or the fabrication process. The problem may be the fault of the coater – perhaps the coating process was changed or the parts became contaminated.

What the customer wants
In some fields, there are standard tests for cleanliness. That’s helpful, but it may not be what the customer wants. For example, in electronics assembly, there are well-established, valuable industry tests to show that conductive residue has been minimized. This means testing for resistivity. What level of resistivity has to be achieved? It’s a moving target that depends on the application. When we explain this to electronics assemblers, one response is to discuss Ion Chromatography. The technique allows you to see which ionic species are present. Is it what the customer wants? An electronics assembly may “pass” all of the tests, but what if they are not the correct tests? Ionics are not the only soil of concern. Non-ionic residue can contribute to product failure, particularly where high reliability over a long time is required. One client was concerned more about particulates than about ionics because the electronics assembly was part of an instrument used during semi-conductor processing.

As in many fields, cleaning electronics assemblies is not an end in itself. It’s not a matter of passing the tests, but about testing for what the customer is worried about.

Are you in charge of cleaning?
Be brave and consider the two questions. The first question: what manufacturing steps occur before the cleaning process to be evaluated? The second question: what’s the next step in manufacturing after the cleaning process to be evaluated?

In fact, it’s more than considering one step back and one step beyond – it’s looking at the end-use of the product. To achieve an effective, economical cleaning process, to produce a product that better satisfies customers, you have to look back and also look forward. It is unlikely that you will understand everything; but knowledge does indeed translate into effective cleaning; and effective critical cleaning translates into productivity.

Reference
B. Kanegsberg and E. Kanegsberg, “Intended Consequences,” 2012
https://www.materialstoday.com/metal-finishing/features/on-the-surface-intended-consequences/

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