Part 2: PCB Specification Documentation for Your Master Drawing

| Created: February 16, 2022 | Updated: March 29, 2024

The master drawing is the most critical part of your design documentation and will convey all of the fine details needed to manufacture your board. While these documentation requirements will change based on the design specifications of your PCB, the overall goal is still to clarify your design intent and avoid any manufacturing delays.

If you would like to skip to different chapters in this series, use the Table of Contents links below:

The master drawing is like the cookbook for your PCB, it includes all the details and instructions on how to manufacture your board. There are specific requirements that you should include in every master drawing.

Master Drawing Class Requirements

Communicating basic information about your design to both your manufacturer and stakeholders mitigates risks of design intent miscommunication. It is highly recommended to utilize the optional blocks that will best fit your particular project’s requirements to facilitate organization of your design documentation. Organized documentation will make it easier for your design intent to connect across your documentation. Now that we have tackled the naming and organization of our documents, let’s take a look at the content of the master drawing.

Class 1 - All that's needed here is the board layout, which acts as the master drawing. Notes will still need to be added to provide the necessary information to your manufacturer. However, notes are not necessary to pass any kind of Class 1 inspection.
Class 2 - All Class 2 products require a master drawing that clearly describes the physical dimensions of the board and includes the following details:
- Pattern features not referenced by hole size or location need to be explicitly dimensioned through notes or referenced by a grid system.
- The coating thickness and plating of the board need to be specified.
- If required, quality conformance test markings can be included in the master drawing.
Class 3 - These types of boards require the most documentation and will need to include the details listed in the table below. Manufacturing processes must also be included, such as drilling, plating or etching.

Board Details	Type, size, and shape Board thickness Bow and twist, including tolerances Board layers stack table
Materials	Type and grade of material; if applicable include color Marking inks
Hole Details	Drill table Drill pattern Vias
Markings	Safety markings (UL, ESD, etc...) Electrostatic discharge Class 1 - Devices sensitive to voltages of 2,000 or less Class 2 - Devices sensitive to voltages between 2,001 and 4,000 Class 3 - Devices sensitive to voltages greater than 4,000 Marking inks
Processing Conditions	The location of quality conformance coupons or circuitry Process specifications and tolerances
Design Concepts	Include the location of test points Include the grid system used whether it be metric or inch based Datums
Documentation	Include notes and place them on the first sheet or include their location on the first sheet Artwork revision Callouts Include pattern drawings for each layer of the board

The information in the table above will be presented in detail in the sections to give you a complete understanding of the requirements for each entry.

Board Details

The board details defines board complexity and structure.

Board Type

The Continuation Sheet Block is used for sheets other than the first page. A Continuation Sheet Block needs to be placed at the bottom right corner of the page as shown in the example drawing below and should include:

Type 1 - Single sided
Type 2 - Double sided
Type 3 - Multilayer board through-hole components only
Type 4 - Multilayer board with through, blind and/or buried vias
Type 5 - Multilayer metal-core board through-hole components only
Type 6 - Multilayer metal-core board with through, blind and/or buried vias

Board Dimensioning

Board dimensioning is a large subject that warrants its own guidebook, this guide will touch on just a few key points as listed below. For a more detailed and complete look at dimensioning please refer to IPC-C-300[7-3] and ASME-Y-14.57-2].

You should add a tolerance to each dimension you place.
Avoid over defining a drawing with unnecessary dimensions.
Clearly dimension a drawing so that there is only one interpretation.
Arrange your dimensions to maximize readability.
Dimension without indicating manufacturing methods, such as what kind of drill bit to use when creating a particular hole.
Specify the origin to give yourself a reference point.
Linear dimensions should use a numerical value at its center with arrows in either direction.

Callouts

A callout connects an item with relevant detailed notes. Callouts are generally utilized to bring attention to a special component or when providing notes with limited space. An example of a callout can be seen in Figure 76 below referencing the notes from the title block.

Bow and Twist

The bow and twist notes tell you how flexible or durable the board is by testing how much a board can bend without breaking. Bow and twist requirements should be noted on the master drawing. An example of this can be found in the example notes (note number 11) at the end of this section.

Board Layer Stack

The board layer stack legend includes details about each layer in your board. It is recommended to include the five columns (Layer, Material, Thickness, Type, and Gerber) in every project to keep documentation consistent and streamlined across designs.

Materials

The materials section defines what materials should be mentioned in the notes section of your master drawing and should specify:

UL requirements
Laminate type
Copper foil

The material for the marking inks should also be mentioned. If the marking ink is conductive, then it needs to be properly isolated from the circuitry by spacing it away from other copper or given a coating.

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Overview of PCB Design Output Files Generating Gerber Files Push to Manufacturing with Altium 365 Project Release Design Documentation Features in Altium Designer

About Author

Zachariah Peterson has an extensive technical background in academia and industry. He currently provides research, design, and marketing services to companies in the electronics industry. Prior to working in the PCB industry, he taught at Portland State University and conducted research on random laser theory, materials, and stability. His background in scientific research spans topics in nanoparticle lasers, electronic and optoelectronic semiconductor devices, environmental sensors, and stochastics. His work has been published in over a dozen peer-reviewed journals and conference proceedings, and he has written 2500+ technical articles on PCB design for a number of companies. He is a member of IEEE Photonics Society, IEEE Electronics Packaging Society, American Physical Society, and the Printed Circuit Engineering Association (PCEA). He previously served as a voting member on the INCITS Quantum Computing Technical Advisory Committee working on technical standards for quantum electronics, and he currently serves on the IEEE P3186 Working Group focused on Port Interface Representing Photonic Signals Using SPICE-class Circuit Simulators.