Are the discrete SMD component patterns sized as EIA or Metric?

Most SMD components have been created based on IPC-7351 standard.

I do not see where all parts are based on IPC-7351, for example the CAP SMD pattern library has EIA pattern names, 0402, 0805

I believe those are EIA naming not IPC-7351, wouldn't the CAP_0402 be a CAP_1005 if it were following IPC 7351.


Thanks
Tim

O, you mean pattern names. It's true SMD chips have EIA names because they are more natural than IPC names.

Hello Alex!
I thought about this just like you, until read the IPC-7351B, and found some annoying consequences of this approach.
Consider for example "CAPC1005X55N" land pattern name.
1. Maximal component's height has an impact on pads size and clearances, and this is coded in the name as "55" (it means 0.55mm). So, to choose the correct land pattern for new component, you should check it's height. "CAP_0402" form contains no this information.
2. Pads size and clearances also depends on board producibility level (there are 3 of them), and this level is encoded in the last letter, "N" in this example means "Normal". "CAP_0402" form contains no this information.
3. IPC standards (IPC-CM-770E for example) recommends transition to metric units, so it looks strange, when all sizes are metric except land pattern names. Also data sheets for new components usually contains sizes in metric units.
4. When i see CAP_0402 in the library, i don't know, has it been made according to IPC-SM-782A, IPC-7351 or something else, and for what height and producibility level (and for what thermal pad size, for QFN), so i need to check this pattern in all details. It makes such land patterns almost useless for new users. IPC-7351B component's naming makes one-for-one relationships between land patterns and their names, so if you know required land pattern name (it can be constructed reading data sheet), you can not confuse it with something else. It is also helpful for automatic 3D models attachment.
5. IPC-7351B naming style is uniform for all component types. Every simplified "ad-hoc" naming will miss something.

I think IPC-7351B pattern names are too complex. Unexperienced customer will have troubles with that names.
Component height usually doesn't affect pattern itself. We thought it was unreasonable to duplicate identical patterns with long names and invent our name convention.
IPC-7351 standard offers 3 levels of density. Our libraries include patterns for normal density only.
There are simiral patterns for the same components in IPC-7351 land pattern calculator. For example, there are few patterns for each chip resistor and capacitor. Most users don't need these variants.