There may be fear of regulatory agencies or of customers. Cleaning most often relates to particles; increasingly, it is also concerned with Airborne Molecular Contamination (AMC) or with minimizing biofilms.
Effective cleaning begins with thoughtful design. For the product, this means avoiding or at least being aware of areas where contamination is likely to occur. For the cleanroom, it means consideration of materials and configuration that minimize contamination. As part of the design, we also include determining what processes will be conducted within the cleanroom and how process flow will occur. Cleanroom real estate is valuable; conducting as much cleaning as possible outside of the cleanroom is not only economical, but can also minimize cleanroom contamination.
Extrapolation is necessary, but it may not be sufficient. We may say that a new product is substantially like an existing one and use cleanliness standards and cleaning practices for the existing product as benchmarks for the new one. However, after a few generations of extrapolation, modified cleaning processes and other, more pertinent, tests for cleanliness may be required.
In cleanrooms, a design to be used for one application may not be readily adaptable to another. Cleanrooms are often reutilized for applications other than those for which they were originally designed. In such instances, it is important to take a dispassionate look at the previous use or perhaps misuse of the cleanroom and to take corrective action. It is also important to assess how the cleanroom is to be used and to make needed changes.
This means not just specifications and standards, but also actual performance requirements. Meeting a specification is not a substitute for logical analysis. Such analysis must involve the expected end-use of the product as well as an assessment of likely contaminants and of the consequences of contamination.
Teaching employees to adhere to rules of behavior or to a specific cleaning protocol is necessary. However, for both product and cleanrooms, there is no substitute for understanding the “why” of the cleaning process. Education is important whether your product and cleanrooms are cleaned inhouse or are outsourced. In fact, when you outsource, educating the employees of the contractor may be even more important.
Monitoring and auditing are part of vigilance. However, monitoring and auditing are not sufficient, particularly with complex products. One reason for the importance of an educated workforce is that you have to expect the unexpected; and this is true for both the cleanroom and the product itself.
CLEAN CRITICALLY—IN AND OUT OF THE CLEANROOM
Too often, cleaning the cleanroom to a particular standard becomes an end in itself; reaching the goal or staying within limits of contamination may not be adequate. The ultimate goals—assuring cleanliness and quality performance of the product—are lost. We have to meet or exceed the requirements. In cleaning the cleanroom and the product, our goal should be to clean critically, to adopt valueadded cleaning. By the way, our view of critical cleaning is that it is a lynch-pin process, one that is essential to product quality. Therefore, critical cleaning may occur not only in the cleanroom but also very early in the fabrication and assembly process. But, more about critical cleaning next year.