SFH5711 IC has overly large recomended footprint...why?

[treez]

Hello,
This chip’s (SFH5711) recommended footprint (6th page of datasheet) is very oversized.
Do you know why?
The part is only 2.95mm long but the recommended footprint has pad copper extending to 3.9mm.
Why is this?

SFH5711 Datasheet
https://www.osram-os.com/Graphics/XPic9/00200854_0.pdf/SFH 5711.pdf

 

[KlausST]

Hi,

I assume it is to get enough solder for the concave pad form.

Klaus

 

[treez]

Thanks, i suppose you are right, but isnt it unusual?...i mean, why in that case use concave pads?
(i am not criticising yourself for this Klaus, i know you are jut stuck with the same conundrun as myself on this.)

 

[KlausST]

Hi,

Some LEDs use similar package. Maybe the pad form has something to do with optics or the used plastic.
I don't know. Just assumption.

Klaus

 

[Mattylad]

That's not overly large, it's only 0.5mm each side.
I have seen many datasheets for LEDs with far larger footprints.

If your assembly processes can solder the LED without as big a pad then make it smaller, have you checked what the IPC footprint tool creates for it?

 

[treez]

Thanks, IPC pad tools costs quite a bit i believe?

- - - Updated - - -

thanks i just downloaded it...free

 

[marce]

That footprint is OK