Your Challenge: Defining the Right Pollution Degree
Pollution Degree: Influencing Factors and Implementation in the Supply Chain and Manufacturing
defining pollution degreeMitigating Risks, Ensuring Quality
The development of a new assembly or power module always begins with defining the requirements, such as performance specifications and the mission profile set by management. A fundamental aspect of this process is considering insulation coordination on the circuit carrier, including the design of clearance and creepage distances. This is based on the pollution degree classification, determined by the designer according to IEC 60664-1 or IPC 2221.
When examining pollution degrees more closely, the classification is often only abstractly described as:
Pollution Degree 1
... "No pollution or only dry, non-conductive pollution occurs. The contamination has no influence."
Pollution Degree 2
... "Only non-conductive pollution occurs, except that occasional temporary conductivity due to condensation is expected. This condensation may occur during the power-on and power-off cycles of the device."
Pollution Degree 3
... "Conductive pollution occurs, or dry, non-conductive pollution that becomes conductive due to expected condensation."
Pollution Degree 4
... "Continuous conductivity occurs due to conductive dust, rain, or other wet conditions."
... without providing detailed guidance on their implementation.
methodologyFrom Pollution Degree to Key Figures: Implementation in Drawings and Specifications
To achieve a design that is optimized for both space constraints (geometry, power density) and cost efficiency, assemblies are typically designed for Pollution Degree 1 or 2. However, production and process technology must translate this classification into material and component selection, manufacturing processes, and overall supply chain management.
To ensure that the final product complies with the initial management requirements and the corresponding design, abstract terms such as "occasional temporary conductivity due to condensation is expected" must be converted into measurable key figures for drawings, bills of materials (BOM), and supplier specifications.
Whether conductivity between potentials on assembly or module surfaces is expected depends primarily on the following influencing factors:
01 | Particle Contamination
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This topic falls under the category of "Technical Cleanliness."
Based on particle risk assessments, a Component Cleanliness Code (CCC) is created. This allows the particle contamination aspect of the pollution degree to be precisely specified and seamlessly integrated into the supply chain and manufacturing processes.
In addition to particle contamination, it must also be clarified whether…
02 | Ionic Contamination
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This aspect can be addressed by specifying the deliquescence humidity in the drawing.
03 | Ventilation Conditions
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In this case, influencing factors must be discussed and defined, such as:
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Enclosure geometries
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Flow conditions
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Self-heating
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