standard size for smt tantalums?

M

Michael Noone

Guest
Hi - I was just wondering - I've noticed that there are very few tantalums
made in the standard discrete surface mount sizes (1206, 0805, etc.). I was
able to find a very limited selection of such capacitors made by TAC (for
example, Digi-Key part # 478-2562-1-ND). But these are expensive (over $2
each for an 0805 in quantites of 100, compared to $.50 for similarly
specced tantalums in different packages). So my question is this: Are there
standard sizes for tantalums? Or does each manufacturer have their own
sizes?

As long as I'm on the topic of tantalums - can somebody tell me why they
are reccomended for power smoothing? Would a ceramic work just as well? (as
they're cheaper and available in sizes I'm more used to)

Thanks,

M. Noone
 
"Michael Noone" <mnoone.uiuc.edu@127.0.0.1> wrote in message
news:Xns9689A2EA41978mnooneuiucedu127001@216.196.97.136...
Hi - I was just wondering - I've noticed that there are very few tantalums
made in the standard discrete surface mount sizes (1206, 0805, etc.). I
was
able to find a very limited selection of such capacitors made by TAC (for
example, Digi-Key part # 478-2562-1-ND). But these are expensive (over $2
each for an 0805 in quantites of 100, compared to $.50 for similarly
specced tantalums in different packages). So my question is this: Are
there
standard sizes for tantalums? Or does each manufacturer have their own
sizes?
Click to expand...
I don't have the specs handy, but I suspect the largest size tantalum that
would fit in a 1206 package would be around 1 ufd at 10V.
As long as I'm on the topic of tantalums - can somebody tell me why they
are reccomended for power smoothing? Would a ceramic work just as well?
(as
they're cheaper and available in sizes I'm more used to)
Click to expand...
Check the price on a 1 ufd ceramic; and where would you buy one that is 100
ufd?

Tam
Thanks,

M. Noone
Click to expand...
 
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in
news:MaidnVKRO-GpSVTfRVn-qA@comcast.com:

I don't have the specs handy, but I suspect the largest size tantalum
that would fit in a 1206 package would be around 1 ufd at 10V.
Click to expand...
The part I mentioned is a 22uf 6.3V tantalum in a 0805 package.

Check the price on a 1 ufd ceramic; and where would you buy one that
is 100 ufd?
Click to expand...
You're right - I forgot that ceramics are normally multiple orders of
magnitude smaller in capacity than tantalums.
 
You can now get a 100 uF 1206 ceramic, but they have rotten tc's and
voltage/capacitance coefficients.

There are five or six standard surfmount tantalum sizes. DON'T use
them for power supply bypasses; they tend to detonate. The new polymer
tantalums are OK.

John
Click to expand...
Yep. Even though we do burn in, a fair amount of these standard tantalums
have decided to explode at our customers' sites.

The polymer tantalums seem to be working okay as supply bypassers, for us.

Bob
 
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
news:0kojc1tvbu83ttbp263s8rqfplq6u5i7s7@4ax.com:
You can now get a 100 uF 1206 ceramic, but they have rotten tc's and
voltage/capacitance coefficients.

There are five or six standard surfmount tantalum sizes. DON'T use
them for power supply bypasses; they tend to detonate. The new polymer
tantalums are OK.

John

So for power supply bypassing I should use polymer tantalums? Or is there
Click to expand...
something better than that? I should mention that size is a bit of a
constraing here... The smaller the parts I can use the better! I was
looking on the Digi-Key catalog and found a couple different series' of
surface mount polymer tantalums:

Kemet: (Digi-Key page 970: http://dkc3.digikey.com/PDF/T052/0970.pdf)
T520 Series - KO-CAP Polymer Tantalum
T525 Series - KO-CAP Polymer Tantalum
T530 Series - KO-MAT Polymer Tantalum

Epcos: (Digi-Key page 976: http://dkc3.digikey.com/PDF/T052/0976.pdf)
B45294R & B45296R Polymer Ultra-Low ESR Series
B45496R Polymer Multiple Anode Ultra-Low ESR Series

Do any of these look like good choices for power supply bypass? (or any
others that I missed - though I looked fairly carefully)

Thanks!

-Michael J. Noone
 
"Michael Noone" <mnoone.uiuc.edu@127.0.0.1> wrote in message
news:Xns9689B5AB6FF33mnooneuiucedu127001@216.196.97.136...
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in
news:MaidnVKRO-GpSVTfRVn-qA@comcast.com:

I don't have the specs handy, but I suspect the largest size tantalum
that would fit in a 1206 package would be around 1 ufd at 10V.

The part I mentioned is a 22uf 6.3V tantalum in a 0805 package.

Check the price on a 1 ufd ceramic; and where would you buy one that
is 100 ufd?

You're right - I forgot that ceramics are normally multiple orders of
magnitude smaller in capacity than tantalums.
Click to expand...
You got me looking at the Mouser catalog, and on the MuRata page I see they
are pushing ceramics as tantalum replacements. They look expensive, but they
claim that in replacing a tantalum, if the frequency is above a few hundred
KHz, you can use a much smaller value of ceramic. I would go to the MuRata
or AVX, or whatever web site and see what they say.

As somebody else mentioned, tantalums can have their own problems. We used
to derate them X2 voltage wise to be sure they did not blow up. Running them
at 90% of rated voltage made for fireworks.

BTW, there are standard sizes for SM tantalums. 3216 is a common size, once
you get above the 0805 and 1210 sizes.

Tam
 
On Mon, 04 Jul 2005 22:35:07 -0500, Michael Noone
<mnoone.uiuc.edu@127.0.0.1> wrote:

John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
news:0kojc1tvbu83ttbp263s8rqfplq6u5i7s7@4ax.com:

You can now get a 100 uF 1206 ceramic, but they have rotten tc's and
voltage/capacitance coefficients.

There are five or six standard surfmount tantalum sizes. DON'T use
them for power supply bypasses; they tend to detonate. The new polymer
tantalums are OK.

John

So for power supply bypassing I should use polymer tantalums? Or is there
something better than that? I should mention that size is a bit of a
constraing here... The smaller the parts I can use the better! I was
looking on the Digi-Key catalog and found a couple different series' of
surface mount polymer tantalums:

Kemet: (Digi-Key page 970: http://dkc3.digikey.com/PDF/T052/0970.pdf)
T520 Series - KO-CAP Polymer Tantalum
T525 Series - KO-CAP Polymer Tantalum
T530 Series - KO-MAT Polymer Tantalum

Epcos: (Digi-Key page 976: http://dkc3.digikey.com/PDF/T052/0976.pdf)
B45294R & B45296R Polymer Ultra-Low ESR Series
B45496R Polymer Multiple Anode Ultra-Low ESR Series

Do any of these look like good choices for power supply bypass? (or any
others that I missed - though I looked fairly carefully)
Click to expand...
How about aluminum electrolytics? Since they're tall, you get at least
as much capacitance per pcb footprint as you do with tantalums.

John
 
Hi Michael,

Hi - I was just wondering - I've noticed that there are very few
tantalums made in the standard discrete surface mount sizes (1206,
0805, etc.). I was able to find a very limited selection of such
They have standard-sizes. Only the smallest fits a 1206 pad. (in
Click to expand...
millimeters:
1.2 x 0.1 inch = 3.05mm, 0.6 x 0.1 inch = 1.53mm so an 1206 equals
a (non-existing) 3116 sized tantalum...)
The sizes are coded A or in Numbers 3216 (which means 3.2mm x 1.6mm),
B (3228), C (6032), D (7343) and E (same as D but greater hight).
Sometimes additional sizes are available (depending on the
Manufacturer.
Check out AVX, Murata, TDK
e.g. http://www.avx.com/docs/catalogs/taj.pdf

capacitors made by TAC (for example, Digi-Key part # 478-2562-1-ND).
But these are expensive (over $2 each for an 0805 in quantites of
100, compared to $.50 for similarly specced tantalums in different
packages). So my question is this: Are there standard sizes for
tantalums? Or does each manufacturer have their own sizes?
As others alredy mentioned... these might be ceramic caps.
Click to expand...

As long as I'm on the topic of tantalums - can somebody tell me why
they are reccomended for power smoothing? Would a ceramic work just
as well? (as they're cheaper and available in sizes I'm more used to)
Ceramics work much better (lower ESR, long-term stability) but are
Click to expand...
much more expensive (you mentioned $2 each).
Many (not cost-sensitive) designers prefer to use ceramics, since they
are much more reliable than tantalums.

cu
Bernhard Spitzer
--
bash.org - Top 100...
<erno> hm. I've lost a machine.. literally _lost_. it responds to ping, it
works completely, I just can't figure out where in my apartment it is.
 
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
news:6e2kc1pqdi6d3d9f0d7cu93jtdarg7sgnr@4ax.com:

How about aluminum electrolytics? Since they're tall, you get at least
as much capacitance per pcb footprint as you do with tantalums.

John
Click to expand...
Will electrolytics work as well for power supply bypassing? Tantalums don't
have any special characteristics that other types of capacitors don't have?

By the way - how does a Digi-Key 399-3178-1-ND look? It's a 10V 33uf Kemet
T520 Series KO-CAP Polymer Tantalum, datasheet here:
http://www.kemet.com/kemet/web/homepage/kechome.nsf/vapubfiles/F3102T520/
$file/F3102T520.pdf

It's a B package - just slightly bigger than a 1206, so I shouldn't have
much trouble fitting it on my board. Not to spendy at a little over $1 in
single quantities.

-Michael
 
There is a very coherent discussion of different capacitor chemistries in
http://focus.ti.com/lit/ml/slup206/slup206.pdf


"Michael Noone" <mnoone.uiuc.edu@127.0.0.1> wrote in message
news:Xns9689D14D8452Amnooneuiucedu127001@216.196.97.136...
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in
news:0kojc1tvbu83ttbp263s8rqfplq6u5i7s7@4ax.com:

You can now get a 100 uF 1206 ceramic, but they have rotten tc's and
voltage/capacitance coefficients.

There are five or six standard surfmount tantalum sizes. DON'T use
them for power supply bypasses; they tend to detonate. The new polymer
tantalums are OK.

John

So for power supply bypassing I should use polymer tantalums? Or is there
something better than that? I should mention that size is a bit of a
constraing here... The smaller the parts I can use the better! I was
looking on the Digi-Key catalog and found a couple different series' of
surface mount polymer tantalums:

Kemet: (Digi-Key page 970: http://dkc3.digikey.com/PDF/T052/0970.pdf)
T520 Series - KO-CAP Polymer Tantalum
T525 Series - KO-CAP Polymer Tantalum
T530 Series - KO-MAT Polymer Tantalum

Epcos: (Digi-Key page 976: http://dkc3.digikey.com/PDF/T052/0976.pdf)
B45294R & B45296R Polymer Ultra-Low ESR Series
B45496R Polymer Multiple Anode Ultra-Low ESR Series

Do any of these look like good choices for power supply bypass? (or any
others that I missed - though I looked fairly carefully)

Thanks!

-Michael J. Noone
Click to expand...
 
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