reverse mountable led?

Erik Friesen · 2009-08-01 16:39

What could the implications be of reverse mounting this led? www.dialight.com/Assets/Brochures_And_Catalogs/Indication/MDEI5981210BI.pdf

Mike Green · 2009-08-01 16:57

The obvious ones ...

1) It's not designed for soldering upside down. Look at how the solder pads are designed

2) There's a clear plastic molded encapsulation over the chip that's not intended to have significant loading on it

You could glue the device upside down over a hole in a PCB, then hand solder short leads from the PCB to the solder pads that are now a short distance above the PCB top surface on the now top surface of the device.

Post Edited (Mike Green) : 8/1/2009 5:03:03 PM GMT

Erik Friesen · 2009-08-01 17:02

Yeah, sometimes a person gets tempted to do it wrong.

A bicolor through hole led would work for me as well if I could find one shorter than 0.200" from the pcb.

What kind of loading would it place on the encapsulation? Most of the solder would be in the end cup anyway, not?

Erik Friesen · 2009-08-01 17:03

I am making a capacative touch panel, and I don't feel like sm soldering to both sides of the board.

Mike Green · 2009-08-01 17:14

They don't give a dimension, but the surface of the solder pads would be at least 0.4mm above the mounting surface. You could hand solder them. That should work.

T Chap · 2009-08-01 18:30

Look up on Digikey:

Osram Point led or TopLed

Reverse mounted LED's for smt backlighting. Often label reverse entry. They have a version that is around .2 diameter and smaller ones.

media.digikey.com/pdf/catalog%20drawings/Optoelectronics/475-1249_DIM1.jpg

Post Edited (TChapman) : 8/1/2009 6:35:48 PM GMT

Erik Friesen · 2009-08-01 19:06

Good eye chapman.

Here are two I found thanks to you www.mouser.com/Search/Refine.aspx?N=254242+4293994460&Keyword=log&FS=True and www.mouser.com/Search/Refine.aspx?N=254249&Keyword=LSG&FS=True

Its a bit tough to find the dual color reverse mounted. Especially when I need red/green and ??/green

For some reason the search refining on those big companies doesn't always get the products in the right category. The red/green and the green/orange are not even grouped together in a search for the osram, and there is no reference to the fact that they are reverse mounted.

T Chap · 2009-08-01 19:12

I went through the same process on a Quantum QT160 based keypad, I put .20" holes in the center of the pads with X and Y around the hole, and wanted a light to pass through the hole where a number was placed with silk screen.

Osram does take a little work, you really need to go to their site and digest the product range, then go to the suppliers (I like digi) and try the product names, a l a Topled or point led etc, even then you have to dig.

Erik Friesen · 2009-08-01 19:15

I am using the qt60160. These chips are amazing out of the box.

T Chap · 2009-08-01 20:43

I never got it to work properly using their own Read following the interrupt(change)output. Instead, I just poll each pad separately in a sequence 0-15 comparing it to a set threshold, and if it triggers, poll it again as a "debounce". If it triggers, stay looping that pad until it drops below the threshold, this adds the adjacent key suppression. I found setting up my own poll worked better and fixed sticking keys that were problematic and unsolvable using their built in logic. Their compensation was doing weird things that I didn't like, had to abandon it after many weeks trying to solve it with their tech.

Definitely a nice part though.

reverse mountable led?

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