Iso Die Package Selection for Compact Surface Mount Assembly
Matching package creepage distance to board pollution degree prevents arc flash failure while maintaining high density surface mount assembly yields.
Comparative Tracking Index
Breakdown Resistance
Electrical insulation measurement determines the susceptibility of a plastic material to surface tracking under wet conditions. The comparative tracking index defines the voltage at which fifty drops of a standard ammonium chloride solution cause electrical breakdown on the surface. This value helps designers select appropriate creepage distances for high-voltage printed circuit boards.
It measures risk assessment in harsh environments.
Voltage Threshold
Electrochemical degradation of the surface occurs when voltage exceeds the critical limit during contamination. High comparative tracking index ratings mean the material resists carbon pathway formation under moisture. Most standards specify a voltage range between one hundred and six hundred volts for testing.
The result is verified on five separate test specimens to ensure accuracy.
Material Classification
Insulation groupings dictate the minimum creepage distances in equipment design rules. The comparative tracking index categorizes materials into four classes from Material Group I down to Material Group IIIb. Group I represents the most tracking-resistant polymers.
Equipment manufacturers require higher groups for environments with high pollution degrees.
Testing Environment
Standardized aqueous solution is dropped from a fixed height of thirty to forty millimeters onto the specimen between two platinum electrodes. The droplet interval remains set at thirty seconds. If the current exceeds point five amperes for two seconds, the specimen fails the test.
This procedure must occur under controlled temperature to maintain consistency. Environmental drift or mineral buildup on the electrodes will skew the results and require re-calibration of the apparatus before further runs.