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Optoelectronics - die pictures

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Hi all!

I need a topic for optoelectronic pictures.  8)

You can find the main page here:

Today I have uploaded pictures of the 7 segment led display VQB17 built in the "Werk für Fernsehelektronik Berlin":

In a red cap there is a opaque foil above a white light shaper with a black textured surface.

You can see the LEDs through the light shaper.
...In the middle there is a loose bondwire...

To connect the pins to the board they used pressfit technology. Very cool!  :-+

The die is 310µm x310µm.
You can spot a MESA structure and a dark square. I assume the dark square is some highly doped contact area.

You can´t really recognize which part of the structure is glowing because the light spreads through the semiconductor and the protective coat all over the die surface.
It start´s glowing at 5µA.

The LED glows also at -12V (2,5mA)...  ;D
The light is much less uniform and of course a lot darker.

More pictures here:



Let´s look inside a blinking LED:


You can´t burn the package stuff like epoxy mould. There is always some sticky dirt left. But you can take pictures through the package. The quality is a bit worse but it´s ok...

The "controller" is 0,48mm x 0,46mm the LED is 0,2mm x 0,19mm.

As expected there is a RC oscillator which frequency is divided with the help of 19 flip-flops.
And hey, the die has two outputs. It can be used to drive two LEDs alternating.
Since the outputs a current sources the not used output is connected to ground.

The current flowing into the LED shows that the second stage consumes nearly the same current as the first stage.
The blinking frequency is round about 1,2Hz.

You can see the oscillator frequency between the pins. The frequency is 0,59MHz. Devided by 19 you get 1,1Hz. That´s quite close to the 1,2Hz observed in the current flow. The frequency is not very stable.


Thanks a lot.

What does Pre mean?

Presumably you don't need a series resistor for that particular LED? I always thought flashing LEDs still needed one.

Another thing which interests me is the maximum operating voltage is seldom mentioned on flashing LED datasheets. In another thread someone ran one off rectified 24VAC, so nearly 34V, via a suitable resistor, with no problems.

Looks nice.

Hey, what's your camera/optics/filters/polarization/lighting?
(I can't find any info on your website, auf Englisch oder Deutsch.)

David Hess:
I thought the old style blinking LEDs were fabricated as one chip.


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