Individual Scissor Switches for DIY Projects

[vaskoiii]

Can somebody help me find more keyboards with scissor switches like the rendered image on the deskthority wiki? I want to source parts to produce individual scissor switches for DIY projects.

Specifically I am looking at:

wiki/Scissor_switch#Internals

Unfortunately, most scissor switches differ from the rendered image in that the flexible printed circuit (fpc) with the metal contacts is almost always sandwiched between the blue and darker gray parts in the rendered image. Having the circuitry sandwiched rather than separate and below the entire scissor switch assembly greatly reduces potential for DIY circuits (ie. using copper tape).

So far I have only found 1 keyboard like the rendered image and do not know what the model is. This particular keyboard uses plastic corresponding to the darker gray parts on the rendered image rather than the usual aluminum (making it way easier to cut out cleanly). Also because the scissor switch assembly is completely separate from the circuit layer, it is easy to test and utilize with DIY circuitry of varying thicknesses.

Please advise.

[Daniel Beardsmore]

The diagram is most likely wrong — I didn't have a keyboard to dismantle (read: destroy) when I drew it. From what I can tell, the structure varies, but the membranes are indeed sandwiched.

It's all extremely thin, so thin that many laptop keyboards bend when you type on them, and you can't clearly make out the structure without pulling it all apart.

The drawing is likely based on my RM notebook:



I can't determine the actual structure from that picture. However, I can confirm that the scissor arms are attached to a lower sheet of metal.

Now, my T43 keyboard is totally different. I have nothing to photograph it with, so I'll try to describe it.

It's far thinner than the RM keyboard. Above the membranes is a thin metal sheet, and above that is a thin black plastic sheet, presumably held down with adhesive (both are extremely thin). This top metal sheet has hooks that retain square black plastic frames, and the scissor arms attach to these frames instead of into the metal directly. The scissor arms hold a plastic platform—the scissor switch equivalent to a slider—and the keycap fits onto this platform.

It's much more complicated than a normal scissor switch. It does however have the property that the whole scissor system is entirely above the membranes, but the membranes are still sandwiched by sheet metal above, and presumably more sheet metal below.

There are so many different designs. I should amend my diagram though to be closer to a typical approach, by adding in the back panel. It's not even drawn to scale, as membrane thicknesses have to be exaggerated in diagrams.

[Edit: You can see the ThinkPad T43 keyboard here: http://www.machinaelectronics.com/store ... inkpad_T43 — hinge type K07]

[vaskoiii]

K07 Hinge Type Option

The K07 hinge type looks like it might work! Also, the "Installation Instructions" from your link demonstrate the assembly well at:
http://www.machinaelectronics.com/blog/hinge-type-k07/

Sourcing parts from this keyboard may require using something like "knipex tools sheet metal nibbler" to get clean cuts on the metal part that holds the scissor switch assembly in place.

Any Other Options?

The keyboard I was referring to earlier with scissor switch assemblies like the "diagram" on the deskthority wiki looks on the outside like:
https://www.amazon.com/GMYLE-Compact-Wi ... B010WMSZ2K

However, there are several different brands/manufacturers with an identical looking keyboard and I am not sure how consistent certain brands are with the internals, which are described vaguely at best.

Perhaps it is possible to tell if someone has the "right" keyboard without disassembly by removing a keycap and just ensuring the scissor attaches to plastic instead of aluminum. Plastic is so much easier to cut! If someone does actually happen to disassemble an entire keyboard like this, be aware that there may be an aluminum backing held on by several melted beads of plastic, which was the case for me, but this was "easily" removed and discarded.

The most important point for a keyboard that I am looking for is that the circuit layer is below and completely separate from the scissor switch assembly just like the "diagram" - If the membrane is connected to this circuit layer that is also ok.

[Daniel Beardsmore]

The diagram is a rough hint, nothing more. It's not based on actual measurements or analysis as I didn't take apart a keyboard for inspection. I've retired a number of laptops and I should have saved a keyboard for disassembly to get proper measurements of the sizes and shapes of the parts. I don't really even want to alter the drawing without having something to measure, as I would still be guessing.

[vaskoiii]

No need to modify the "diagram" - It is conceptually perfect.

[Daniel Beardsmore]

No need to modify the "diagram" - It is conceptually perfect. :D

It should be closer to reality — what I need is some illustrations to work from. It may be a while until I have another knackered old laptop to play with. The membranes I guess are going to be the usual ca. 0.06 mm outer and ca. 0.09 mm inner.