Really small SMT: Popular packages?

[Joerg]

After getting used to 0402 and 0201 passives it seems my next design has
to also shrink for the transistors, this time all of them. I have
designed in things like SC-75 in the past but there is quite a
bewildering number of choices in the "below SOT-23" category.

What might percolate as the most popular transistor and diode size in
"micro-SMT"?

 

[Tim Shoppa]

After getting used to 0402 and 0201 passives it seems my next design has
to also shrink for the transistors, this time all of them. I have
designed in things like SC-75 in the past but there is quite a
bewildering number of choices in the "below SOT-23" category.

What might percolate as the most popular transistor and diode size in
"micro-SMT"?

SOT-323 had the most choice earlier in this millenium but your SC-75's
are already smaller!

Two-transistor arrays with built-in resistors are the real space-saving
step but they can have substantial supply-line problems if you're
working in medium quantities and use anything outside the most usual
values.

If your designs are "wide enough" there are some transistor and
resistor and diode arrays that make great sense. Almost always I see
these used in data or address bus situations and I think you fall
outside that realm.

Tim.

 

[DJ Delorie]

After getting used to 0402 and 0201 passives it seems my next design
has to also shrink for the transistors, this time all of them. I have
designed in things like SC-75 in the past but there is quite a
bewildering number of choices in the "below SOT-23" category.

I've found there are two sub-sot23 sizes I like, which are
approximately sot-323 and sot-523. These correspond to sc-70 and
sc-75, and sot-523 corresponds to sot-416. The sot-323 part
corresponds roughly to a 0.65mm pitch (i.e. the space between the two
pins on the same side is 1.3mm); the sot-523 approx 0.5mm. Note that
"approximate" is the relative size only; each package has specific
details that differ from others, check the specs to be sure.

Photos of the relative sizes can be found here:

http://www.delorie.com/pcb/smd-challenge/mine-back.jpg

The blue parts are 0402, the LEDs are 0603. The two transistors are
sot-323 and sot-416. The grid is 1/16".

Other cross references from my notes (mm is lead-lead, not pitch):

SOT-23 1.9 mm
mini 3P 1.9 mm
SC-59 1.9 mm
SOT-143 1.9 mm

S-mini 3P 1.3 mm
SC-70 1.3 mm
SC-88A 1.3 mm
SOT-323 1.3 mm

SC-75 1.0 mm SOT-416
SOT-523 1.0 mm
SS-mini 3P 1.0 mm (chiplead, not gull-wing)

SSS-mini 3P 0.8 mm (chiplead)

Then you get into CSPs (i.e. micro-bga style).

 

[Joerg]

SOT-323 had the most choice earlier in this millenium but your SC-75's
are already smaller!

SOT-323 is a massive boulder

Two-transistor arrays with built-in resistors are the real space-saving
step but they can have substantial supply-line problems if you're
working in medium quantities and use anything outside the most usual
values.

Those are indeed nice. Anything more than two was a disappointment so
far. Found some nice quads wired up in an H-bridge. But they almost
wanted a whopping $1 for these in qties. No way, I can do that for under
10c with four discretes. What were they thinking?

If your designs are "wide enough" there are some transistor and
resistor and diode arrays that make great sense. Almost always I see
these used in data or address bus situations and I think you fall
outside that realm.

In the past I found that the sales of 6-7 transistor arrays were a bit
of a closed market. Hard to buy and really only available from Asian
sources. Which might be ok for designs that are produced in China, as
long as the arrays cost 10c or less and come in TSSOP or smaller.

BTW, what's up with Digikey? Fails a lot, saying "server is currently
updated", then comes back after a minute or so. Is everything freezing
up there?

 

[Joerg]

I've found there are two sub-sot23 sizes I like, which are
approximately sot-323 and sot-523. These correspond to sc-70 and
sc-75, and sot-523 corresponds to sot-416. The sot-323 part
corresponds roughly to a 0.65mm pitch (i.e. the space between the two
pins on the same side is 1.3mm); the sot-523 approx 0.5mm. Note that
"approximate" is the relative size only; each package has specific
details that differ from others, check the specs to be sure.

Do you think SC-75 is here to stay? That would at least yield a factor
of two improvement over SOT23, roughly.

Photos of the relative sizes can be found here:

http://www.delorie.com/pcb/smd-challenge/mine-back.jpg

Nice! Looks like a bit much in solder. Try Kester 15mil and a Weller ETS
tip. Probably I'll have to find even smaller solder soon. Plus a nice
USB camera if there is one that can be fitted with a zoom lens (macro is
too close to the iron). I don't like microscopes much and the 3x glasses
in the lab aren't going to cut it anymore for 0201.

The blue parts are 0402, the LEDs are 0603. The two transistors are
sot-323 and sot-416. The grid is 1/16".

Other cross references from my notes (mm is lead-lead, not pitch):

SOT-23 1.9 mm
mini 3P 1.9 mm
SC-59 1.9 mm
SOT-143 1.9 mm

S-mini 3P 1.3 mm
SC-70 1.3 mm
SC-88A 1.3 mm
SOT-323 1.3 mm

SC-75 1.0 mm SOT-416
SOT-523 1.0 mm
SS-mini 3P 1.0 mm (chiplead, not gull-wing)

SSS-mini 3P 0.8 mm (chiplead)

Then you get into CSPs (i.e. micro-bga style).

I always wondered why they splintered up the descriptors so badly.
Couldn't agree, I guess. Like with those dreaded EU and US differences
in resistor sizes that can easily cause costly purchasing mistakes.

 

[Tim Shoppa]

In the past I found that the sales of 6-7 transistor arrays were a bit
of a closed market.

Gotta limit yourself to ULN2003-alikes .

BTW, what's up with Digikey? Fails a lot, saying "server is currently
updated", then comes back after a minute or so. Is everything freezing
up there?

They recently revamped the search engine. I see some good from the
revamp, but it frustrates the hell out of me that every value is now
specified to 4 or 5 significant digits! Like we'd have to tell the
47.000 uF caps from the 47.001uF caps!

Tim.

 

[DJ Delorie]

Do you think SC-75 is here to stay? That would at least yield a
factor of two improvement over SOT23, roughly.

There are enough footprints in that size, and the cost is comparable.
I think it's here to stay. IMHO the SSS-mini is still wait-and-see,
perhaps the CSPs will supercede it.

Nice! Looks like a bit much in solder. Try Kester 15mil and a Weller
ETS tip.

Those were hand soldered with Kester 20mil, with a Metcal 20mil
conical tip. Since then I've gotten a syringe of paste, it works even
better than wire solder - dab a bit of paste on the pad, place part,
heat leads with iron, paste melts.

Plus a nice USB camera if there is one that can be fitted with a
zoom lens (macro is too close to the iron). I don't like microscopes
much and the 3x glasses in the lab aren't going to cut it anymore
for 0201.

Most of my close-ups are taken with an IntelPay QX3 microscope. The
bigger ones are taken with a digital camera; the Canon A70 has a macro
setting that works real well if you put a few layers of paper in front
of the flash to reduce the glare.

Other side: http://www.delorie.com/pcb/smd-challenge/mine-front.jpg

Here are some other photos taken with the QX3:
http://www.delorie.com/pcb/smd-challenge/fp-pix/

As for actually soldering, I use a 3.75x mag visor (10 diopter) for
the 0201's and 01005's, and a 2.5x (5 diopter) for everything else. I
got them from Woodcraft (they're sold for scroll sawing, which I also
use them for).

I always wondered why they splintered up the descriptors so
badly.

I'm guessing it has to do with lead size, length, etc.

 

[Joerg]

There are enough footprints in that size, and the cost is comparable.
I think it's here to stay. IMHO the SSS-mini is still wait-and-see,
perhaps the CSPs will supercede it.

That would be great if SC-75 became a staple. So, might be time to
generate the CAD models now.

Those were hand soldered with Kester 20mil, with a Metcal 20mil
conical tip. Since then I've gotten a syringe of paste, it works even
better than wire solder - dab a bit of paste on the pad, place part,
heat leads with iron, paste melts.

Good point. Paste is the next thing I want to try out.

Most of my close-ups are taken with an IntelPay QX3 microscope. The
bigger ones are taken with a digital camera; the Canon A70 has a macro
setting that works real well if you put a few layers of paper in front
of the flash to reduce the glare.

Other side: http://www.delorie.com/pcb/smd-challenge/mine-front.jpg

Nice job on the chips. Looks like they were done with paste.

Here are some other photos taken with the QX3:
http://www.delorie.com/pcb/smd-challenge/fp-pix/

As for actually soldering, I use a 3.75x mag visor (10 diopter) for
the 0201's and 01005's, and a 2.5x (5 diopter) for everything else. I
got them from Woodcraft (they're sold for scroll sawing, which I also
use them for).

I don't like working with something between me and the board while I'd
have no problem soldering while looking at a monitor in another
direction. But I am in the minority here, most folks at clients don't
like to do that at all.

 

[Boris Mohar]

BTW, what's up with Digikey? Fails a lot, saying "server is currently
updated", then comes back after a minute or so. Is everything freezing
up there?

They told me that they had a pipe burst and the hamster got all wet. I am
trying to complete an order and it has been really flaky.

 

[DJ Delorie]

Nice job on the chips. Looks like they were done with paste.

Nope. Also hand soldered.

 

[Joerg]

They told me that they had a pipe burst and the hamster got all wet. I am
trying to complete an order and it has been really flaky.

And no mirror server? Oops.

Pipe bursts can be bad. We just had a large retirement home evacuated
and they said it'll take 4-6 weeks for restoration of the place.

 

[qrk]

After getting used to 0402 and 0201 passives it seems my next design has
to also shrink for the transistors, this time all of them. I have
designed in things like SC-75 in the past but there is quite a
bewildering number of choices in the "below SOT-23" category.

What might percolate as the most popular transistor and diode size in
"micro-SMT"?

I've been using SC89 6-pin parts for my dual transistors from ROHM.
Still haven't ventured into 0201 parts yet.

 

[Joerg]

I've been using SC89 6-pin parts for my dual transistors from ROHM.
Still haven't ventured into 0201 parts yet.

On the design I am doing right now I'll be lucky if I can avoid the use
of 01005 resistors :-(

 

[DJ Delorie]

On the design I am doing right now I'll be lucky if I can avoid the
use of 01005 resistors :-(

Those take me about 20 minutes each to hand solder (place, inspect,
solder, inspect, resolder, etc). We've renamed those to "quantum
capacitors". One moment they're on the board, the next moment they're
gone!

I'll stick to 0201s or 0402s from now on.

 

[Joerg]

Those take me about 20 minutes each to hand solder (place, inspect,
solder, inspect, resolder, etc). We've renamed those to "quantum
capacitors". One moment they're on the board, the next moment they're
gone!

Tell me about it. Much of the inspecting effort goes into ascertaining
whether it is actually there. Or if not, where the heck it went. Before
soldering all it takes is uncle Leroy next door to sneeze and it's gone.
One of my clients actually thought that I'd switched to pixie dust.

 

[Rich Grise]

.

BTW, what's up with Digikey? Fails a lot, saying "server is currently
updated", then comes back after a minute or so. Is everything freezing
up there?

Everything is "freezing" all over the place these days.

I think it's the fault of U-tube and those "get a date for free" sites.

And blogs, of course. >:-(

Thanks,
Rich