How does the PCB affect the sound of the keyboard?

[Gimbal]

I am in the process of planning my very first custom keyboard and I would like to use mx clear switches, which unfortunately pings awfully. If I hold a switch in my hand I can’t get it to ping at all, but once mounted in a keyboard they sings like sirens.

So I wonder how the PCB affects the sound of the keyboard. Does anyone know if there is a noticeable difference in the sound between a normal switch plate with a normal PCB, and the same switch plate without a PCB (hand wired)?

One could imagine that the PCB would transmit the sound quit effectively being solidly soldered in to the switch, but I don’t know, maybe it doesn’t.

[Leslieann]

PCB will have minimal effect, despite being connected, it's a soft material and the plate tends to take the actual impact regardless of mount.
The plate will change the sound of the ping, but more importantly it can and usually does amplify it. Brass and plex seems to dampen the most (by quite a lot). Foam in the bottom and between the plate and PCB can also help.

Ping itself is caused by the springs, thinner gauge springs tend to be worse for this, try some different ones (Cherry tend to be bad for it). Coated/plated ones also may do it less but I haven't had a chance to verify that yet, makes sense though since it can be a softer metal and also thickens the spring. Lubing the top and bottom of the springs tends to also help.

One other thing I would suggest is try some other switches, like I said, Cherry springs ping more than some other.

[Gimbal]

Yes it's the vibrating ping from the spring that haunts me. It's enough to brush the fingers over the keyboard for the springs to start singing. So I'm guessing that when the spring starts to sing the vibrations has to translate both up through the steam and into the key cap, and down through the bottom of the switch into the switch plate and the PCB.

But since I can still here the ping even if I don't let go of the key cap I have to guess the sound is not emitting through the key cap but through the switch plate. Even though I painted the steel plate with several layers of some sort of plasti dip before installing the switches, which means that the switches have a thin rubber gasket between them and the plate. I thought it was a brilliant idea but it seems it didn't do much at all.

[Leslieann]

Painting it isn't a bad idea.
Coating the plate with a thin layer of silicone might do even more but ultimately you're treating the symptoms not the cause.

[Gimbal]

Yes, the spring being the cause, but I am not that keen on opening and lubricating every switch since that is only a temporary solution as I understand it.
But maybe using a softer material in the switch plate would do the trick. I did try hitting the empty steel switch plate with a bit of metal and it sounded like hitting a bell, a small bell but still. I have not tried doing the same with a plastic switch plate (as I don't have one) but I'll bet it has a lower resonance frequency.

[fpazos]

I'm not too expert on this matter but I thing that the plastic may reduce the propagation but will also change the sound. Recently y changed a cheap chinese build to isollated gasket mount and 3d printed case and completely improved the sound. I'll upload the buildlog this weekend.
To reduce sound and ping the best options are to change to isollated gasket mount (maybe use dampeners between pcb and screws if it is bottom mount) and to reduce the empty space inside the keeb (use foam between plate and pcb).
That's a really complex thing and you never know how'll be the final result beforehand.

Enviado desde mi Redmi Note 7 mediante Tapatalk

[Findecanor]

I have to guess the sound is not emitting through the key cap but through the switch plate.

I have a vintage Cherry keyboard with PCB-mounted switches, and it pings. Here, it is the PCB that reverberates because there is no plate.

At the other end of the spectrum I have a keyboard where both plate and PCB are tightly sandwiched between plastic and it is quite loud but it does not ping at all

[Leslieann]

Yes, the spring being the cause, but I am not that keen on opening and lubricating every switch since that is only a temporary solution as I understand it.

Silicone lube doesn't dry out or evaporate the way petroleum lubricants do, not that you should use that on plastic anyway (it can damage plastics), Telfon based lubricants are the same way. Regardless, a spring swap can do as much as lube to quiet ping.

No one ever said any of this was easy.

I have a vintage Cherry keyboard with PCB-mounted switches, and it pings. Here, it is the PCB that reverberates because there is no plate.

A plate reduces the pcb's ability to do this, the irony of it is that while the pcb is quieted the plate is worse.

[Gimbal]

Thanks everyone for your input, it does help to get a better understanding of the problem. I have some Ideas now that I'm going to try out. A Varmilo numpad with clears and a steel switch plate will be the target for some experiments. My first idea of a skeleton PCB is replaced for a sandwich construction involving a thick rubber mat between the plate and the PCB.

As for the switches I don't want to change springs in the clears, as it is the heavier spring I like about them. But they might end up with some silicon lube inside them...