Keycap Kevin: how to hot swap on any keyboard

Hot swap boards allow you to swap out your switches quickly and easily. Unfortunately, not every keyboard is built for this. Hot swap models usually have a fixed layout. If you want to try different variations, you usually have to solder.

Thankfully, Mill-Max connectors offer an alternative. You have to solder them too, but only once. This has its pitfalls, but is doable.

The Mill-Max principle

Mill-Max connectors are soldered to the contact point with your board. Visually, they resemble hollow nails. Into this cavity you insert the pins for your switches. This establishes contact between the switch and the board.

Mill-Max connectors come in various sizes. For keypad boards, the 0305, 7305 and 3305 models can be used. 0305 is relatively long at 3.94 millimetres, but easier to solder than the other two. 7305 and 3305 are both 2.67 millimetres long. 3305 are flattest at the top when in place, allowing the switch to lie flat on the board. It’s why they’re the most suitable in my eyes.

The connectors cost quite a pretty penny. I paid around 60 francs for 200 pieces. I only need about 150 for my 70-per cent keyboard, but at least I have a few to spare. You’ll also need either switches or heat-resistant tape to hold the sockets in place before soldering. Both have their advantages and disadvantages, which I’ll explain below.

Here’s how it works

No matter what you choose, the first thing you have to do is to insert the connectors into the contact holes of your keyboard board. The best way to do this is to use tweezers. After that, fix them in place by either inserting the switch or covering them with tape.

The first option has the advantage of the connectors being exactly in the place they should be. Tape isn’t as firm and the connectors can shift a bit during soldering. You have to be careful not to put too much pressure on the connectors when soldering.

With the switch method, the risk of failed solder joints is greater. If you apply too much solder to the contact point, you may connect the connector and the switch. The switch is still soldered to the board – goodbye hot swap. Separating switch and pin again is very tedious.

Personally, I prefer the tape variant, as it’s less prone to errors. In addition, at almost 40 years of age, I no longer see so well at short distances, which is why this option is particularly suitable for me.

Once all the connectors are in place, you just have to solder them on. Watch this video to find out just how to do it. After you’re done, you can swap your switches as you please.

I chose the XOX70 board for my Mill-Max project. I don’t expect to swap out my Gateron Irene switches. But in future, I might well use a different keycap set with a split spacebar. The one I’m after isn’t out yet, so I’m using another one for now. Once the right set is out, I can change my layout without soldering thanks to the Mill-Max connectors.