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by jdietrich
3720 days ago
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SMD passives are listed in both metric and imperial units. Most sizes are unambiguous, but 0402 and 0603 resistors exist in both series. There's also possibility for confusion between the imperial 01005 and the metric 1005. These parts are specified in metric, making the imperial sizes purely nominal. http://www.newark.com/chip-smd-resistors/resistor-case-style... The metric/imperial split is a constant nuisance. Most board houses and PTH packages use mils, but the vast majority of SMT IC packages are specified in millimetres. Board layouts almost always necessitate switching between imperial and metric units; Layout software includes features to manage this. Wire gauges are a total mess - AWG, SWG and mm are all in common use. Standard pin headers and derivative connectors are 0.1" pitch (2.54mm), but JST connectors are 2.5mm pitch. Conversion errors have caused countless production problems. |
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