PCB notes are essential instructions and specifications provided by the board designer to the fabrication house. PCB fabrication notes serve as the primary communication channel between the designers and fab houses.
These notes detail crucial requirements for manufacturing the printed circuit board (PCB), ensuring the final product meets the designer's intent and performance specifications.
Purpose of PCB Notes
The main purpose of PCB notes is to convey precise manufacturing requirements that cannot be easily captured solely within the graphical layout data. They clarify specific tolerances, materials, processes, and finishing details necessary for the fabricator to build the board correctly.
Think of them as the rulebook or special instructions that accompany the blueprint for building the PCB. Without these notes, the fab house might make assumptions that lead to errors, delays, or non-functional boards.
Where are PCB Notes Found?
PCB notes are typically included in the fabrication drawings. These drawings are a comprehensive set of documents that accompany the design files sent to the manufacturer. According to the reference, fabrication drawings comprise:
- Board shape with dimensions
- Location of drilled holes (drill chart)
- Details of cut-outs
- Layer stack-up
- Title block
- And importantly, the fabrication notes themselves.
What Information Do PCB Notes Contain?
PCB notes cover a wide range of fabrication requirements. Based on typical industry practices and the context provided by the reference (detailing communication and specific aspects like materials and finishes), common information includes:
- General Specifications: Overall fabrication standards to be followed (e.g., IPC standards like IPC-A-600).
- Material Requirements: Specific PCB laminate type, thickness, and copper weight.
- Layer Stack-up Details: Confirmation of the arrangement and thickness of dielectric and copper layers (often visually represented but detailed in notes).
- Drilling Information: Tolerances for hole sizes, plating requirements (plated or non-plated), and specific drill processes.
- Soldermask and Silkscreen: Color, thickness, and any specific registration tolerances.
- Surface Finish: Type of surface finish required (e.g., ENIG, HASL, OSP) and its specifications.
- Dimensional Tolerances: Overall board dimensions, feature locations, and board edge requirements.
- Testing Requirements: Mandated electrical testing procedures (e.g., flying probe, bed of nails).
- Quality Assurance: Specific inspection criteria or quality standards.
Example of Information in Notes
Here’s a simplified look at the types of details often communicated:
| Aspect | Example Note Text |
|---|---|
| Standard | FABRICATE PER IPC-6012 CLASS 2. |
| Material | BASE MATERIAL: FR4, TG 150 MINIMUM. |
| Copper Weight | ALL COPPER LAYERS: 1 OZ MINIMUM FINISHED. |
| Surface Finish | SURFACE FINISH: ENIG (ELECTROLESS NICKEL IMMERSION GOLD). |
| Testing | 100% ELECTRICAL TEST REQUIRED (FLYING PROBE). |
| Dimensional Tol. | ROUTE OUTLINE TOLERANCE: +/- 0.1mm. |
These notes are critical for preventing misunderstandings and ensuring the manufacturing process results in a board that precisely matches the designer's intentions for the electronic product.
