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Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
Hi there,
I'm about to get a densely packed single sided board ready and the only spot left for two LEDs is so small that 0805 ones will fit. I've occasionally seen LEDs mounted on top of holes that emit downward through the PCB, that would be right what I needed.
My question would be: are these standard cuboidal LEDs that were just soldered facing the board or are there LEDs that have suitable solder tabs on both top and bottom surface. I have seen that there are Osam TOPLEDs with flipped gullwing tabs that can emit downward but I'm at a loss with finding smaller ones.
Any suggestions are much appreciated
Greetings, hboy007
ps. I just found out that they are called "reverse mount smd leds"... ok. but there are only 1206 and larger ones oO ... come on! This is so not fair!
Registered Member #63
Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425
Hi hboy007,
The LEDs you're looking for are commonly sold in 1305 packages, and feature metallization on both sides of the ceramic substrate. I first encountered them in Nokia 3315 handsets as keypad-illuminators.
wrote ... ps. I just found out that they are called "reverse mount smd leds"... ok. but there are only 1206 and larger ones oO ... come on! This is so not fair!
PS, it's probably too tricky to drill a hole between two reflowable pads of an 0805, then plate that hole without touching the pads
PPS, if it's a dim status light that needs only to be visible, you could use a side-mounting 0805, and position a hole in your PCB near the lens as appropriate.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
Hi Blackplasma,
thank you for the hint. If I get stuck on the LED problem again, I'll be able to make good use of what I've learnt today Just for closure I show you what I mean with "no space left". There are no vias needed, the board is single sided and will be tinned with hot air leveling. Soldering will be done manually, propably using the reflow technique. A slit would be cool...
However, I've chosen to just let there be two 0805 LEDs on the back of the board (the only alternative would be a bipolar red/green duo LED in a 1206 or 1305 package). If they light up, the user is in big trouble, anyway (blown fuse or wrong supply polarity)
Again, thanks for the help and enjoy your sunday evening!
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
For hand assembly, chip LEDs can generally be mounted upside-down in a hole as the metal is usually on both sides - it's more of a problem for production pick & place, as they're the wrong way up on the tape. Osram do some very nice thru-board LEDs in a circular package about 3mm dia - pointled range I think.
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rear mount / flip mount / downward emitting SMD LEDs ... can't find them anywhere
