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Weird size SMD Tantalums

Some company went out of business and we inherited their substantial parts inventory. While most of it is pretty regular stuff there was something there that I can't figure out.

There are more than a hundred reels of weird size tantalums. They are all

4.7mm long x 2.7mm wide x 2mm thick (plus/minus caliper tolerance.) There are several different values ranging from 1uF 35/50V to 4.7uF 16V. Most of those are from unknown manufacturers -- the reels are re-labeled by component dealers with their own labels with manufacturers' part numbers but without mention who the manufacturer is/was. Google finds nothing meaningful on those part numbers like e.g. ICTB335K16T (3.3uF 16V part.) Some of those are black, some regular mustard color.

The only exception is something like 30 reels of AVX TAJM105M035R parts that are supposedly their TAJ series but according to their part numbering scheme those should be of "M" size that doesn't exist. Furthermore I can't find ANY tantalum even close to 4.7x2.7mm (4727/1909?) from ANY manufacturer. The closest standard size of ANY SMD chip is 1808 but I don't know any TANTALUMS of this size and it is still not an exact match -- 1808 is 4520 that is slightly short and significantly more narrow than 4.7x2.7mm.

Does anybody know what it is? We would've liked to use those and although it is not rocket science to make custom footprints for them but the mystery of what it is won't let us sleep peacefully...

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Reply to
Sergey Kubushyn
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You can find out most of what you need to know (at least for light duty use in noncritical applications) by seeing how they're made and how hard they are to detonate. For the first, use a ball peen hammer to crack off the epoxy and see if there's a proper lead frame. (Some lead frame parts have the springy ends wrapped round to form the pads, but iirc some don't.) You really want lead-frame parts for reliability.

For the detonation test, I'd use a lab supply, a BFC for charge storage, some large-gauge clip leads, and an upside-down coffee mug or something to contain the fragments. I'd wear safety glasses even so, because sometimes those things create lots of very hot shrapnel. (Legal disclaimer: This should only be done by trained personnel with proper protection equipment in a well-ventilated area.)

Folks with more production experience than I have can probably weigh in on how big a safety factor you want vis a vis the detonation test, but good makers perform 100% inrush testing at 110% of rated voltage. See e.g.

and

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

Sounds like reels of firecrackers.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

That is all definitely right but the question remain -- WHAT IS THAT

4.7x2.7mm SIZE IS? Or what is Tantalum M size is?

I was not asking what part it is -- I DO know those are solid tantalums and even have their manufacturers' part numbers. I happened to hear about tantalums derating during my 40 years engineering career and saw several thousands of blown tantalums, saw them catching fire and much more fun.

But that is all irrelevant. The question is does anybody know what that

4.7x2.7mm or size M is? Is it any standard? It might be something e.g. Japanese specific. 
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Reply to
Sergey Kubushyn
[...]
[...]

For a wild guess, could it be that this size was chosen so that the caps fit (for whatever reason), say, a SOD-128 footprint? Scanning through the Wikipedia article [1] doesn't seem to uncover anything else quite like that.

[1]
formatting link 
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FSF associate member #7257  http://am-1.org/~ivan/
Reply to
Ivan Shmakov

That is the mystery that won't let me sleep :)

Those were definitely made to some standard as I have more than a hundred full reels of several different values from different manufacturers and they are all of exactly same size that can't be a coincidence. Furthermore, those TAJMxxx from AVX fit into their numbering scheme perfectly assuming they do have a size "M" package. Those are original AVX reels so it is not a wild guess but their EXACT part number. The only problem is that there is no such size mentioned anywhere at AVX :( It looks like size "B" but 1.2mm longer (4.7mm instead of size "B" 3.5mm.) All other dimensions seem to fit into size "B" tolerance range.

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Reply to
Sergey Kubushyn

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