In recent blogs we have been talking, for the most part, about particles that are relatively large – ones you can see, touch and feel. There is a world out there, however, that worries about particles that are very tiny. I’m talking about particles that are smaller than tens of microns in dimension. An earlier …
Now it’s time to see the results! Particles have been harvested, collected and are ready to either be weighed or counted. The first step in evaluating cleanliness using either method is to examine the specification. There are two basic types, part-specific and generic. Part-Specific Specifications – Part-specific specifications will state the sample size in number …
In preceding blogs we have talked about harvesting particles for evaluation and talked about specifications. Specifications may or may not dictate the harvesting process but almost always provide detail on how to evaluate the particles harvested in a process involving re-washing. The first step is to concentrate the harvested particles for evaluation. This usually involves a filtration and evaporation process. …
Before we get into quantifying the particles we have harvested in the last few blogs, I would like to take a minute or two to talk about the specifications that define and govern the evaluation process. In upcoming blogs we will talk about the quantification of particles in general terms. In real life, there is …
Those of us who have played the particle counting game know that there are some tough calls when it comes to harvesting particles as part of the cleanliness testing procedure. In some cases, adhering strictly to the specification would result in the rejection of every part tested. Although I do not believe that rules are …
Although manual re-washing techniques for harvesting particles are effective for a wide range of particle types and sizes, they may fall short in collecting particles that are very small (less than 10 or 20 microns) or difficult to remove from the surface of the substrate for one reason or another. Ultrasonics, which has long been the “gold standard” of cleaning, …
The evaluation of cleanliness is often based on a quantification of the particles left on a surface following the conventional or production cleaning process. The first step in evaluating a part for cleanliness with regard to particles is to harvest those particles that remain after cleaning. Once harvested, the particles can be counted, weighed, microscopically …
Removing foreign particles from surfaces is the target of many cleaning operations. The spectrum of the definition of particles as contaminants is very broad and encompasses size, number, shape and composition. Because of the diversity of the nature of particles, the methods to detect and quantify them are diverse as well. Some particles are easily seen with …
So far in this series we have concentrated primarily on the detection of oil and other hydrophobic films on surfaces. However, not all contaminating films are oil and all are not hydrophobic. What about contaminants that are not hydrophobic and may even by hydrophilic (residual soaps and surfactants, for example) as well as things like oxides? These are just …
The tests described in the last couple of blogs are rudimentary ways to assess the surface activity of the surface being tested. In fact, they are all based on the concept of contact angle. A drop of water resting at equilibrium on a surface will intersect that surface at a measurable angle called the contact angle. The …
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