Introduction
Mechanical keyboards have seen a surge in popularity among typists and gamers who appreciate their solid build quality, tactile feel, and customization potential. At the heart of every mechanical keyboard is the PCB or printed circuit board, which interconnects all the components. While traditional PCBs require soldering switches, many newer boards use hotswap PCBs which allow swapping switches without soldering. This article examines the differences between these two PCB technologies and their implications for mechanical keyboards.
What is a Mechanical Keyboard PCB?
A traditional mechanical keyboard PCB works as follows:
- FR-4 fiberglass PCB material with copper traces
- Matrix of traces connect to keyboard switch pins
- Supports plate mounted or PCB mounted switch designs
- Switches must be soldered onto the PCB pads
- Additional chips for microcontroller, RGB lighting etc.
- Edge connector or cables to connect to computer
Soldering the switches provides robust mechanical and electrical connections to the PCB. But desoldering existing switches to replace them is very difficult.
Figure 1: Example mechanical keyboard PCB with switch matrix traces
What is a Hotswap Keyboard PCB?
A hotswap keyboard PCB differs in some key ways:
- Uses special hotswap sockets on the PCB instead of pads
- Sockets have holes to insert switch pins without soldering
- Allows freely swapping switches with ease
- Metal alloy leaf springs inside sockets grip pins
- More complex PCB design to avoid blocking sockets
Enables customizing and tweaking switches without any soldering needed.
Figure 2: Hotswap keyboard PCB with visible hotswap sockets
Hotswap Socket Types
There are a few common types of hotswap sockets:
- Mill-Max – Gold plated brass pins, widely used, medium cost
- Kailh – Stamped steel with copper alloy coating, lowest cost
- Gateron – Brass alloy, higher spring force, compact
- Zeal – Gold plated phosphor bronze, higher cost, premium
Each uses alloy leaf springs and plated contacts for corrosion resistance and optimal electrical properties. The number of insertion cycles ratings range from 100 to 10,000+ depending on quality.
| Parameter | Mill-Max | Kailh | Gateron | Zeal |
|---|---|---|---|---|
| Material | Brass | Steel | Brass Alloy | Phosphor Bronze |
| Plating | Gold | Copper Alloy | Gold | Gold |
| Force | Medium | Medium | High | Medium |
| Pitch | 0.1″ | 0.1″ | 0.075″ | 0.1″ |
| Durability | 10K cycles | 1K cycles | 5K cycles | 50K cycles |
| Cost | Medium | Low | Medium | High |
Table 1: Comparison of popular hotswap socket types
Hotswap vs Soldered Stabilizers
In addition to switches, stabilizers play an important role in larger keys like spacebars. Hotswap PCBs often use hotswap sockets for stabilizers too:
- Allows easily changing stabilizers without desoldering
- Provides consistent fit between stabilizer and PCB
- Poor tolerance stackup can cause issues in soldered stabilizers
- Some PCBs still use traditional soldered stabilizers
Hotswapping stabilizers enables quickly testing different sizes or styles.
PCB Design Differences
Several PCB design considerations differ between traditional and hotswap boards:
Routing Channels
- Hotswap sockets are large and need clearance space underneath
- Channels route traces on inner PCB layers around sockets
Component Placement
- Must avoid blocking socket opening or leaf spring area
- Limits options for microcontroller and support IC placement
PCB Layers
- Additional layers needed to route matrix traces cleanly
- 4-5 layers common instead of 2-layer for basic boards
- Shielding helps minimize switch pin crosstalk
- Grounded copper fills around hotswap sockets
Careful engineering is required for reliable hotswap board operation.
Performance Differences
Hotswapping does come with some performance tradeoffs:
Latency
- Slight delay through socket resistance and connections
- Only μs level difference from soldered switches
Key Feel
- Very minor decrease in crispness from socket flex
- Negligible for most users
EMI Susceptibility
- Soldered provides 100% grounding
- Some gaps remain between socket and pin
- Primarily affects tightly packed boards
But for the vast majority of users, hotswap provides identical functionality to soldered keyboards.
Ease of Assembly
A key benefit of hotswap keyboards is dramatically easier assembly:
Soldered Keyboard Assembly
- Requires soldering 100+ switches by hand or machine
- Risk of cold joints or damaged switches
- Desoldering to change switches very difficult
Hotswap Keyboard Assembly
- Just press switches into sockets by hand
- No soldering skill or equipment needed
- Switches can be freely changed later
This allows keyboard enthusiasts to build fully custom boards with minimal tools and cost.
Customization Ability
Similarly, hotswap makes customizing and modding keyboards far simpler:
- Testing switch types only requires buying new switches
- Mixing switch types across keyboard
- No need to desolder to change layout
- Simpler to swap stabilizers or O-rings
It offers the convenience that many hardcore “switch testers” desire.
Cost Differences
Looking at costs:
Soldered Keyboard PCB
- Lower board cost, as little as $20-30
- Must buy soldering tools and equipment
- Time investment to assemble
Hotswap Keyboard PCB
- Board cost typically $50-100+
- No tools besides switches needed
- Very quick to assemble
For makers without soldering capability, hotswap eliminates equipment costs in exchange for higher board pricing.
Long Term Durability
An important consideration is long term durability:
- Hotswap sockets rated for hundreds to thousands of insertion cycles
- Springs and contacts eventually wear out
- Soldered joints last indefinitely with quality construction
Power users who regularly swap switches should expect reduced hotswap lifetime. Casual users who only modify occasionally will see very long hotswap viability.
Ease of Repair
Repairing issues is far simpler with hotswap boards:
Soldered Keyboard Repair
- Requires desoldering to replace damaged switch
- Tedious desoldering process prone to damage
- May need new PCB if traces or pads lifted
Hotswap Keyboard Repair
- Just unplug and replace faulty switch
- No desoldering needed
- Preserves rest of board/switches
This saves tremendous time and avoids collateral damage when troubleshooting.
Custom Hotswap PCBs
While hotswap PCBs are now available for common layouts, custom designs are possible:
- Custom layouts may require new hotswap PCB
- Must design appropriately around sockets
- Higher NRE cost than basic PCB
- Allows fully customized matrix and layout
Conclusion
In summary, hotswap and traditional soldered PCBs each have their pros and cons for the mechanical keyboard builder. Hotswap makes assembly far simpler and enables extensive customization with minimal tools or skills. But traditional soldered boards offer reduced costs and maximum electrical reliability for some users. Hotswap sockets are an innovation that has fueled greater access and creativity in the enthusiast mechanical keyboard community. The option between soldered and hotswap PCBs provides flexibility to balance cost, complexity, and convenience.
FAQs
Q: Does hotswapping switches void a keyboard’s warranty?
A: Most keyboard warranties are void as soon as the board is opened up. Hotswapping would likely not be covered in any circumstance.
Q: Can any mechanical switch work in a hotswap PCB?
A: Generally yes, but very thick or wide switch pins may not fit in the sockets. Always check socket specs.
Q: Do hotswap sockets work for through-hole diodes?
A: They can, but compatibility depends on diode leg thickness. SMD diodes avoid this issue.
Q: What is the average lifespan of a hotswap socket?
A: Lower quality sockets last 500-1000 cycles. Premium ones can exceed 50,000 cycles, essentially very long lifetimes.
Q: Can a hotswap keyboard work without any switches installed?
A: No, the switches complete the electrical connections in the matrix, so at least some are needed for functionality.
