Soldering SMD lights onto normal 2 pin LED pads?

[Petch]

Is this something one can do? I want to backlight some Kailh BOX switches for a friends KBD75, and they're only compatible with SMD lights

Looking at these but they're pricey (£20 for 100) http://www.mouser.co.uk/ProductDetail/Broadcom-Avago/ASMT-UWB1-NX3G2/?qs=sGAEpiMZZMseGfSY3csMkeNEFgJPYWeCZWWh94XTRqY%3D

Aliexpress has some for a lot cheaper, but I question the longevity

[TalkingTree]

Is this something one can do?

LED holes are 2.54 mm apart from their respective centres and the copper ring is 0.32 mm wide (at least on my PCBs). Those SMD LEDs are 3.5 mm long and the contact surface on each pad is 0.8 mm ± 0.3 mm.
Given these measurements, I'd say it's doable.

Keep in mind that the LEDs are 1.9 mm ± 0.2 mm tall, so you need compatible switch housings.

[Petch]

Is this something one can do?

LED holes are 2.54 mm apart from their respective centres and the copper ring is 0.32 mm wide (at least on my PCBs). Those SMD LEDs are 3.5 mm long and the contact surface on each pad is 0.8 mm ± 0.3 mm.
Given these measurements, I'd say it's doable.

Keep in mind that the LEDs are 1.9 mm ± 0.2 mm tall, so you need compatible switch housings.

Thanks for the measurements

The Kailh BOX switches look like they have enough room cut out for them, but I don't have an accurate way to measure - I'll assume they'll fit as they're meant to support SMD lights...

As far as the electronics go, there should be no reason for them not t work right? I'm pretty sure the KBD75 PCB doesn't support RBG backlights which is why I'm going for the milky whites

[TalkingTree]

As far as the electronics go, there should be no reason for them not t work right?

Correct.

[woodkeys]

I have personally used through hole 2x3x4 LEDs with box switches. You just have to solder them on the board first and make sure they are straight which can be tricky. I also have a friend that used SMD LEDs with box switches on a planck. That's a little more difficult because the planck doesn't have the solder pads exposed on the top side. Other than that it worked fine. If you have a more typical board with the solder pads exposed it won't be a problem.

Sent from my Nexus 6P using Tapatalk

[Petch]

I have personally used through hole 2x3x4 LEDs with box switches. You just have to solder them on the board first and make sure they are straight which can be tricky. I also have a friend that used SMD LEDs with box switches on a planck. That's a little more difficult because the planck doesn't have the solder pads exposed on the top side. Other than that it worked fine. If you have a more typical board with the solder pads exposed it won't be a problem.

Sent from my Nexus 6P using Tapatalk

Yes, the pads are visible on both sides 

Could you ask you friend where he got his SMDs from? £0.20 each seems expensive, and I'm not sure what the quality of ones on aliexpress will be

[woodkeys]

He got them from Mouser: http://www.mouser.com/Search/ProductDetail.aspx?R=150120AS75000virtualkey51110000virtualkey710-150120AS75000

These are amber LEDs, but you should be able to find something similar in white. Looks like they are about $.16 each if you buy 100, so about $16. Not sure what that would be in the UK though.

[Petch]

He got them from Mouser: http://www.mouser.com/Search/ProductDetail.aspx?R=150120AS75000virtualkey51110000virtualkey710-150120AS75000

These are amber LEDs, but you should be able to find something similar in white. Looks like they are about $.16 each if you buy 100, so about $16. Not sure what that would be in the UK though.

Nearly half the price of the ones I was looking at, though the design is a little difference

[Petch]

More electronics noob questions - looking at different LEDs, the current seems to vary between 20 and 35mA

If I stick a 20mA and 35mA LED to the same PCB, will they both receive whatever the PCB gives (25 for example) or will they get 20 and 35 respectively?

Basically i don't want to get some 35mA and them be too bright