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移除书签3.2.4. Footprint Variants
Within a Package there can be multiple footprint variants. They are intended to support the following use-cases:
Mounting variants: For example, a THT resistor can be mounted either vertically or horizontally with various pad distances. Every common mounting variant should be available as footprint variants.
Soldering techniques: Many packages can be soldered either by reflow-, wave- or hand-soldering, which usually require different land patterns. For every suitable soldering technique there could be a corresponding footprint variant.
Density levels: IPC-7351 specifies three different density levels for footprints:
Density Level A: Maximum (Most) Land Protrusion
Density Level B: Median (Nominal) Land Protrusion
Density Level C: Minimum (Least) Land Protrusion
If applicable, these three density levels should also be added as footprint variants.
Combinations As a given Package might support multiple of the use-cases above, all suitable combinations of them should be added. For example a Package which should have all three density levels as defined in IPC-7351 and can be mounted either vertically or horizontally would need six footprint variants to support all possible use-cases. |
Set default footprint The first footprint is always the default footprint, so you should move the most reasonable footprint to the top of the footprint list! The default footprint should fulfill these rules:
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Example 4. THT resistor 0207 footprint variants
