How Your Choices Shape Your PCB

Building a custom keyboard is a journey of choices. From the size of the board to the feel of the switches, every decision helps shape your final creation. But here's the secret: almost every choice you make has a direct impact on the design of the Printed Circuit Board (PCB). The PCB isn't just a component you pick from a list; it's the canvas that brings your vision to life, and its design is a direct reflection of your priorities.

This guide will walk you through the key decisions you'll face and explain how each one influences the layout and features of your PCB. Understanding these connections is the key to designing a keyboard that is truly and uniquely yours, ensuring that form and function align perfectly.

Your Vision, Your PCB

Building a custom keyboard is a journey of choices. From the size of the board to the feel of the switches, every decision helps shape your final creation. But here’s the secret: almost every choice you make has a direct impact on the design of the Printed Circuit Board (PCB). The PCB isn't just a component you pick from a list; it's the canvas that brings your vision to life, and its design is a direct reflection of your priorities.

The Big Decisions and Their Consequences

1. Layout and Form Factor: The Blueprint of Your Board

Your keyboard's layout—the physical arrangement and number of keys—is the most fundamental choice you'll make, and it defines the PCB's physical footprint.

Physical Dimensions: A standard 60% layout will have a different switch matrix and physical dimensions than a 75% or a split ergonomic board. The PCB must be designed specifically to match the number of keys and their positions. This also affects compatibility with cases and plates, which are built around these standard sizes.
Split vs. Single Block: Are you building a traditional keyboard or an ergonomic split design? This is a major fork in the road. A split keyboard requires either two separate PCBs that communicate with each other (usually via a TRRS or USB-C cable) or a more complex single flexible PCB. This decision fundamentally changes the required electronics, as the two halves need a way to sync up.
Mounting Style: How the PCB and plate assembly sits inside the case also affects PCB design. A gasket mount requires a PCB with specific cutouts and a flexible design, while a tray mount needs screw holes in precise locations to attach to the case standoffs.

2. Switches: More Than Just a Feeling

The type of switches you choose has a surprising number of implications for the PCB's design and your build process.

Hot-Swap vs. Soldered: This is a critical decision. A hot-swap PCB comes with pre-installed sockets that let you plug in and remove switches without soldering. This requires a PCB specifically designed with these sockets, which adds to the cost and complexity. A soldered PCB has simple plated through-holes, giving you more layout flexibility (like supporting multiple bottom rows or a split backspace) but requiring you to solder the switches permanently.
Switch Footprint (MX, Alps, Choc): While most modern custom keyboards use MX-style switches, other types like Alps or low-profile Choc switches exist. Each has a unique pin layout (or "footprint"), and the PCB must have the corresponding holes drilled to match. An MX-style switch will not fit in a PCB designed for Alps switches.
5-Pin vs. 3-Pin Switches: MX-style switches come in two main varieties. 5-pin switches (also called PCB-mount switches) have two extra plastic legs that help align them securely on the PCB. A PCB needs to have the extra holes to support them. While you can clip the plastic legs to fit a 3-pin board, a 5-pin compatible PCB offers better stability, especially for builds without a plate.

3. Backlighting: Let There Be Light

Adding illumination to your keyboard is a popular choice, but it starts with a PCB that's designed for it.

Per-Key Backlighting: If you want each key to have its own light, the PCB needs a spot to mount an LED for every single switch. This adds significant complexity and cost to the board, requiring extra traces and often a more powerful microcontroller to handle the logic.
Underglow: For that cool, ambient glow from beneath the keyboard, the PCB needs a series of RGB LEDs mounted on its underside. This is generally simpler to implement than per-key lighting but still requires a specific PCB design.
LED Compatibility: The choice between single-color LEDs and full RGB LEDs also dictates the circuitry required. RGB LEDs require more complex wiring and control, which must be factored into the PCB's design from the start.

4. Connectivity and Controller: The Brains of the Operation

How your keyboard connects to your computer and the "brain" that runs it are defined by the PCB's electronic components.

Controller: The microcontroller (like an ATmega32U4 or a more modern ARM chip like the RP2040) is the chip that runs your keyboard's firmware (e.g., QMK/VIA). The PCB is designed around a specific controller, which determines its features, memory, and programming capabilities. A board with extensive RGB lighting will need a more powerful controller than a simple, non-backlit board.
Connectivity: Do you want a modern USB-C port or a wireless Bluetooth connection? The PCB must include the necessary components, whether it's the physical port itself or a dedicated Bluetooth module and a battery management circuit. Wireless keyboards are significantly more complex to design and require careful power management considerations.

By understanding how these choices are interconnected, you can plan your build more effectively and ensure that the PCB you choose—or design—has everything you need to bring your ideal keyboard to life.

Ready to dive deeper into specific features? Explore our guide on Exploring PCB Features and Options. If you're trying to figure out where to find the right board for you, check out our advice on Where to Find Your Perfect PCB.