Design Guidelines

General

Descriptions are standardized for simple searching. See DESCR.md. If you want to add a new class of part that doesn't have an entry in DESCR.md, please contribute to that file as well.
Separate power units: orient vertically, pins at +/- 0.4in with 0.15in length
Text should be 50 mil in general
Pin length, numbering, general naming:
- ICs: pins at least 0.15in long, pin numbers 50 mil text
- Discrete semis: pin numbers 40 mil text.
- Passives: omit pin numbers for two-pin parts. Three-pin parts can omit numbers when the third pin is structural (e.g. grounded crystal). When using numbers, use 40 mil text.
- Name all pins. Hide names when the symbol graphic identifies the pin instead (transistor BCE, etc)
- Prefer overbar for inverted pins with names, inversion circle for inverted pins without names. Don't combine the two!
In manufacturer libraries, name parts according to manufacturer naming scheme.
One footprint per part; specify footprint in Footprint field
For parts with a large number of variants (e.g. fixed-voltage regulators), a placeholder in the name is acceptable: LM1117DT-v.v
Prefer logical schematic to blank parts with names - e.g., use buffer symbol in buffers, not just pins named IN and OUT.
Include bomtool BOM lines whenever possible.
Do not duplicate data! Don't fill in footprint filters, we use the footprint field. Don't use the keywords field, the new component chooser filters on description.

Do not follow manufacturer naming. Be consistent, Microchip's "VSS" is no different from Atmel's "GND".
For single rail parts, name main supply V+ (not VCC, VDD)
For multi-rail parts, name main supply according to use when possible (VCORE, not V1.2)
Ground is GND, not VSS