# PCBA Project Versioning

## Background

A PCBA has four design ouputs that completely define the board. These outputs are
- Schematic
    - The *schematic* defines all of the components on the bord and how the components are interconnected. This is done in an abstrac way with notional symbols representing components and component connections. The Bill of Material (BoM) is directly tied to the schematic.
- PCB layout artwork
    - The *layout* defines the physical implementation of the electronic components and their interconnections on a specific board geometry.
- PCB fabrication diagram
    - The *fabrication diagram* defines the manufacturing board. These parameters can include but are not limited to -
        - Layer stackup (including thickness)
        - Copper weight
        - Materials
        - Solder mask color
        - Testing requirements
        - Controlled impedance requirements
- PCBA assembly diagram
    - The *assembly diagram* defines specific assembly steps and proceedures. These steps and proceedures can include but are not limited to - 
        - Mechanical Parts that need to be installed on the board
        - Coatings
        - Packaging
        - Cuts and jumps
        - ESD handling requirements

Each of these design outputs should be versioned independently.

## Rationale
- Schematic
    - Component values can be changed and pin compatible direct replacement parts can be substituted without affecting the artwork, fabrication, or assembly requirements.
- PCB Layout artwork
    - Components can be re-arranged on the board and still adhere to the same schematic, fabrication and assembly parameters.
    - If changes in schematic, fabrication, or assembly require a layout change then the layout artwork revision should be incrimented.
- PCB Fabrication Diagram
    - Fabrication requirements can change without a change in schematic, artwork, or assembly. For instance core materials and thickness can be changed.
    - If changes in schematic, layout artwork, or assembly diagram require changes in the fabrication diagram then the fabrication diagram revision should be incrimented.
- PCBA Assembly Diagram
    - Assembly requirements can change without a change in schematic, layout artwork, or fabrication diagram. For instance a conformal coating could be added or removed or a wave solder process could be changed to a hand solder process.

*A change log should be kept for the various design outputs*
 https://keepachangelog.com/en/1.1.0/

## Part Number Nomenclature

| Output                | Part No | PCB Layer   | Revision | Comment                               |
| --------------------- | ------- | ----------- | -------- | ------------------------------------- |
| Schematic             | EnnnnS  | Silk        | Variable | Schematic can be changed without spin |
| Artwork               | EnnnnG  | Etch        | Fixed    | Artwork change requires spin          |
| PCB Fab Diagram       | EnnnnF  | Solder Mask | Fixed    | PCB fab requires spin                 |
| PCBA Assembly Diagram | EnnnnA  | Silk        | Variable | PCBA can be reworked without spin     |




