[Laser] Re: DVD LD

[Chuck Hast]

On 6/18/07, Tim Toast <toasty256 at yahoo.com> wrote:
> hi Chuck
> sorry i dont have a clue about the part number but i had a
> chance to look at another high powered 650nm dvd diode in a
> dvd burner recently (couldn't keep it though sadly) and it
> was nothing like i expected.
> At first i thought i was looking at a photo diode pickup
> array, but i saw it already had one of those on the other
> side of the pickup unit. Apparently it was an integrated
> type pickup with photo diodes in the same package. The
> 'laser chip' was about 1 square cm in size and flat,
> looking more like a ccd chip than a diode. In fact it was a
> chip. A surface mount type package with about 20 pins - ten
> on each side. One whole surface of the chip had a coated
> glass window covering it. The back of the 'diode' was in
> thermal contact with a small heat sink that looked to be 2
> or 3 square inches surface area altogether and folded up
> around the pickup body. (there was also a fan in the case
> that blew air at it)
> With a 25x microscope i took a closer look at the chip
> through its window. Near the middle of the chip was a
> rectangle shaped area that was larger than the other
> structures, it was about 1mm by 3mm i think. There were
> larger copper traces on the little flexible circuit board
> going to the two ic pins conected to that area, so im
> assuming that was the actual laser diode. There appeared to
> be a little 1mm square photo-diode next to the big
> rectangle and some other smaller squares and rectangle
> patterned areas that i guess were the various circuits and
> photo diodes for the pickup.
> I didnt remove the other pickup IC to look at it but it had
> a similar number of pins, but no heat-sink - it may have
> been the 780nm laser with built-in pickups since most dvd
> players or recorders use both wavelengths. I know some of
> the lower powered diodes in dvd players are dual
> wavelength, but have a more conventional package with only
> 4 pins. I didn't get a good look at the corrector optic if
> there was one, just a grey tinted plain window about the
> same size as the chip window is all i could see.
>
Yes, I have seen these too. I opened up several CD burners and out of
the lot there was one with that type of diode/sensor and the rest had
discrete diodes.

The one I found was sort of like the diode cases but oblong,and it had I
believe 10 pins on it, appeared to be 8 on each side and 1 pin on each
narrow end.


-- 
Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."