The Cause and Effect Relationship Between Cleanliness and Field Life
We deal with a lot of cleanliness issues, which result in early field failures and poor hardware reliability. During cleanliness assessments, we have found that there is a direct correlation between a clean operation and highly reliable hardware. We developed the Critical Cleanliness Control testing unit (also referred to as C3) that is used to evaluate residues on manufacturing operations.
Don’t Blame the Entire Assembly
You may get a green light from your overall cleanliness testing but still experience failures of your assembly. This will drive an operator crazy, especially when they’ve already been given the general seal of approval. While this is frustrating, it’s not an uncommon experience.
The reason you’re having failures despite having passed cleanliness testing is that bulk resistivity testing – ROSE testing – measures everything as a whole product. This is why we’ve developed the C3, a steam extraction instrument that allows for localized residue analysis.
The C3 Extraction Process
This test instrument applies an electrical bias across electrodes with a controlled spacing between them that is submerged into the extracted solution. The ionic contamination level may be effectively related to the measured leakage current across the electrode gap and the amount of time it takes for the leakage current to exceed a threshold level.
Our residue extraction process is designed to effectively remove ionic residues using the following sequence:
Solution is heated and delivered to the extraction site (micro-bursts of steam).
Soak time allows the heated solution to solubilize and extract residues present at the extraction site.
The solution is aspirated into the test cell.
This process is repeated nine times in order to effectively remove the surface residues from a 0.1 in 2 area, gathering approximately 2.5 mL of extraction solution to be used during testing.
Maintaining Cleanliness Testing For Improved Reliability
Our extraction method is proven effective and ion chromatography testing indicates, time and again, that properly cleaned assemblies will commonly have a longer field life and more reliable components.
Often it’s not the cleanliness of the entire assembly that’s the problem, but rather small pockets of contamination between two critical features (e.g. pads, leads, vias) that cause failures. This is why localized cleanliness assessments are important in determining where failures may originate and how to best clean those areas. C3 testing should be done if you experience failures even though you’ve already passed your cleanliness testing.