Hotswap Sockets

Dave · September 21, 2020, 1:48pm

A few months ago I added Holtite sockets to a Leopold FC980m. After some trial and error I stumbled across someone who had a one liner Reddit comment reply saying use solder paste. I ordered some on Amazon and it worked out great I was able to get all of the sockets flush with the PCB. No shenanigans with tinning the sockets and minimal filling sockets with traditional solder.

After at least 4 whole board switch swaps I only had a problem with one socket that was pulled out with a switch. I was able to resolder paste and install the socked quickly. (I think it came out because I was using switches that had been soldered before and didn’t have super clean pins.)

I did try some Mill-Max sockets (models: 7305 & 0305) but didn’t like how the lip of the sockets made the switches sit above the PCB. I couldn’t get one of the switches to sit flush against a plate in a numpad set up so I went the Holtite direction.

I am about to start doing this again on another board and I realized that Holtites fell out of popularity a while back. I am curious does anyone know why? (ie Mill-Max are just superior, Holtites are too hard to install and/or PCB compatibility is not good failures etc)

Is there any other alternative to Holtite or Mill-Max? (Kailh ones require being designed into the PCB so they aren’t an option for my case)

korbin73 · September 21, 2020, 2:24pm

In my opinion Kailh sockets are hands down the best. There is one problem. The PCB has to support them, so unless you are building a board that has a PCB that supports them, you won’t be able to use them. As far as I know Holtites and Mill-Max are your only option.

Dave · September 25, 2020, 7:28pm

Thanks for you feedback. I will stick with Holtites for this build.

My current technique is good but but I ordered some of those one key PCBs to see if I can turn it into a jig for under the PCB while soldering to keep the sockets super straight.

snagy · September 25, 2020, 10:26pm

One thing I’d like to see PCB designers start doing is sizing their PCB pinholes to the 7305 spec size (1.524mm), which is a tiny bit bigger than the cherry MX spec footprint hole size. I switched my switch footprints to the larger size and 7305s sit lower on the PCB, install more cleanly and look nicer.

Manofinterests · September 25, 2020, 10:28pm

Oh do you have a pic of the switches sitting lower? I major complaint I’ve always heard is the switches sitting too high

snagy · September 25, 2020, 10:33pm

Unfortunately i don’t have any PCBs with 7305s installed that aren’t currently built into a keyboard. Next time i have something disassembled I’ll snap some shots…I can’t say for certain that it changes how the switches sit, I just noticed a clear improvement in how the sockets sit when installing the 7305s. Maybe i’ll pop some sockets into a spare PCB tonight and see if I can tell a difference on how the switch sits.

Dave · September 26, 2020, 1:28am

Had some extra Mill-Max sockets lying around so Dremmeled one down to be as thin as possible while still having a lip. This is really hard to see in person let alone in a picture. But even the dremeled one sits just off the PCB. Maybe I could create a 3d printed part to fit under the switch like a switch film but that seems like way more work then I want to get into right now.

I would love to see if PCBs could be made to better handle these sockets with a stepped holes or ones that are at an angle to better handle these. I want to like the Mill-Max more they are easier to install, look more durable but I am still a fan of that flush install of the Holtites

Photo sockets:

Mill-Max 7305
Mill-Max 0305
Mill-Max 0305 ground down
Switch is just sitting in the PCB

Mill-Max Socket close up. (The one I Dremmeled in the photo was an oopsie but in reality it is about 1/2 the lip height of the 7305.

Deadeye · September 26, 2020, 1:50am

I can totally see it in the photo - the un-modified ones don’t let the little corner nubs touch the PCB.

I’m really glad I found this out before I soldered a bunch of those in, because I did just get some Milmax sockets - though reading through this thread and checking back through my keeb modding playlist I realized it was Holtite sockets that I meant to get. This guy makes installing them look pretty easy:

At least it’s not a wash - I’ve got plenty of abrasive dodads to experiment with…

Dave · September 26, 2020, 2:51am

That is a good video! It varies greatly from PCB to PCB. Some are very tight and it is a squeaky to push it to the right spot, others are super loose. If it is loose you can apply a little bit of solder then suck it out and it slightly reduce the diameter of the hole, holding the socket tighter (or you can try solder paste, which I am still experimenting with).

Regardless of the technique, it is extremely satisfying to get the sockets flush. Good luck!