D9-1C diode array

Note that I was mentioning SOT523 and not SOD523.

Have you ever tried hand soldering mini-melf compared to SOD123? At least for me, much quicker and easier.

I didn’t liked mini-melf as it is round (worse to keep with tweezers). We tried also some diodes I would call rectangled mini melf (MCL4148 is an example I just found). After such tries we decided (previous century) to use transistors and diodes only in SOT323 (BC847W, BC857W, BAV99W, BAV70W, BAW56W). So even we needed one diode we used double. In my opinion it is extra protection against mistake with soldering diode the other way round (you can’t do it with SOT323). Recently (means 5…7 years ago) I decided to get back to use single small signal diodes and because of it I have SOD123, SOD323 and SOD523 footprints but my designs are assembled by contract manufacturer and not manually. I stopped worrying about incorrect assembly - it is his worry :slight_smile:

Hi Piotr

It is surprising to me that one person (you) would find the mini-melfs to be more difficult and another person (me) would find the SOD123 more difficult.

  1. The cathode band is MUCH easier to see on the mini-melf
  2. You can (reasonably) lay down the SOD123 8 different ways on the pads (including on its side, upside down, reverse polarity) of which only one is correct. You can reasonably lay down the mini melf two different ways on the pads, of which one is correct. SOD123F may be a little easier to keep upright than ordinary SOD123.
  3. My hands are not so steady but I have no problem with the mini melf in tweezers. My hands are better for scrambling eggs than for doing surgery. :frowning:
  4. The square mini melfs might be OK; but with one hand holding diode in tweezers and the other hand holding soldering iron (with solder already on one pad) the cylindrical mini melf diode will not roll away. The square mini melfs seem to be less common and more expensive than the cylindrical ones.

Reminds me of our decision when (with my employer) we started with SMT during 1990s. We used SOT23 transistors, 1206 resistors, and BAV99 diodes in SOT23 (even if using only one diode.) I do not remember what capacitors we used but probably mostly 1206s.

Fortunately we have a choice :slight_smile:
Those time (about 1990) we (me and my brother) didn’t choose between diodes in mini-melf and SOD123 but between resistors in mini-melf and 1206. The flat side surfaces of the 1206 grip better with tweezers than round glass (larger contact area - mini-melf easier rotates vertically, and jumps out). Those time we used only resistors SMD. Other elements were hard to get. It was only 1 year after Poland left the socialist bloc (means lack of everything, including phone numbers - we, as a firm, had to wait 2 (or more) years to get a phone number, my parents were waiting 19.5 years until they got a number).
About 1995 we bought a semi-automatic machine for SMD assembly. The elements were taken by negative pressure with a flat metal tube (diameter of the order of 2mm). Flat top of element is better to get with it (the air does not escape). I suppose those rectangled mini melf were done because of it. I didn’t used that machine so I’m not sure but I can imagine that if you want to rotate element (and do it fast) then mini melf can not exactly follow this tube rotation because poor contact with it.
I have checked my footprints - mini-melf occupies 4.8x2.4=11.52 and SOT323 3.2x2.6=8.32 (we skip over using SOT23 very fast). So there were no reasons to use diodes in mini-melf as you had 2 in smaller package. End effect was - we used only Zener diodes in mini-melf as they could dissipate higher power and accept higher current pulses.
Regarding SOD123 - I wold never consider those extra 4 positions. It is practically not possible to not notice that legs are not at PCB.

Hi, Piotr

That mostly makes sense. I can imagine that vacuum pickup does not work as well with mini-melf (SOD80).

But just to confirm; I am unsure about your double negative:

Do you mean that you have no problem with SOD123 or that you find it difficult?

One difficulty is to see how the diode is rotated, but the greater difficulty:
When I put down the SOD123, it is probably laying on its side or upside down. Cylindrical mini melf cannot be on its side or upside down,
The difficulty is to rotate SOD123 correctly with tweezers even if the misplacement is obvious.
It is also difficult to see the cathode band.

Guys, funny to see you chatting along :rofl:

Just excuse me for a second’s interruption and let me leave my symbol and footprint for the D9-1C here:

Diode_Array_8_Common_Cathode.kicad_mod (2.6 KB)
d9-1c.dcm (105 Bytes)
d9-1c.lib (606 Bytes)

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My guess is that these are commercially obsolete.
Not much is made in through hole these days and these were obscure even in their day

Not possible to not notice means I’m sure I will notice if diode will be upside down. So I don’t expect any problem with it. Nowadays I am not soldering anything myself (only when I am looking for the source of problems in product) but when touching the sharp soldering tip you see that it goes under the diode leg instead of leaning against it.

What else are you doing here :slight_smile:

obsolutely absolete. I am not sure what commercial production these days uses small through hole parts. Also the quantities and price at Mouser don’t seem commercially viable.

Obsolete or not, to my eye the package looks like a SIP resistor package. I suspect that who ever made these (back when they did make these) they probably just used the leadforms and tooling for SIP resistors instead of inventing their own wheel. Yes, I would expect the legs to be flat in profile, but I’d still use a round hole. Much like DIP ICs have flat legs, but you use round holes for the footprint. In fact, if I couldn’t already find a SIP footprint to use with these, I’d probably base it on a DIP footprint. I wouldn’t start with a pinheader footprint simply because the holes would be way too large.

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That is what I did - reduce the diameter of the holes to 0.8mm Additionally I named the pins according to the specs. If you like, have a look at the files attached to my previous post.

In real life, I will be using a combined footprint to alternatively let one solder 8 SMD diodes instead. So for my comfort I will use the arrays as long as I have some in stock, but may further use the PCB after that.

What if you use 7 pointed star shaped holes? :crazy_face:

That looks like the SIL resistor arrays. Maybe you can steal the footprint from them.

That is what @SembazuruCDE said above. You try hard not to develop a custom lead frame

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