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'[EE]: 0805 underpass, handsoldering'
2002\02\15@070919 by NDuckworth

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This post reminded me of rumors that 1206 packaged components are being phased
out, anyone on the list know why or when? I find the 1206 allows compact
layouts with fairly easy hand soldering, I'll miss them if they do disappear.

Nigel

On Friday, February 15, 2002 11:00 AM, Stuart Meier
[SMTP:spam_OUTstuartmeierTakeThisOuTspamRYG1.FREESERVE.CO.UK] wrote:
{Quote hidden}

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2002\02\15@100346 by Douglas Butler

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My January-April 2002 Digi-Key catalog still has 1206 R's and C's.  The
whole product lines of the last three companies I have worked for would
require revisions if these went away!  I have got to believe that as
long as market demand stays strong there will be supply.  There are
still plenty of RN55 size leaded resistors available, though they have
gone from 1/4W to 0.4W.

Sherpa Doug

> {Original Message removed}

2002\02\15@183350 by Ashley Roll

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Hi Everyone,

Just to add my $0.02.. I recently went to talk with an assembly contractor
and they "suggested" that I stick with 0805s or 0603s as the 1206s where
being phased out by the manufactures as the 0805 is much more popular.

This doesn't mean that you can't or won't be able to get 1206s, just that
they will become rarer and take longer to source and also be more expensive.
If you want your product to be easily manufacturable in a few years, go with
the 0805s..

I've run a trace between the 0805 pads before and didn't have a problem
using the 8mil/8mil rules.. It was a "last resort" type of thing though, but
I did have a solder mask and that really helps. Virtually no chance of
messing it up then :)

Cheers,
Ash.

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Digital Nemesis Pty Ltd
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Mobile: +61 (0)417 705 718




> {Original Message removed}

2002\02\15@190809 by Spehro Pefhany

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At 09:31 AM 2/16/02 +1000, you wrote:
>Hi Everyone,
>
>Just to add my $0.02.. I recently went to talk with an assembly contractor
>and they "suggested" that I stick with 0805s or 0603s as the 1206s where
>being phased out by the manufactures as the 0805 is much more popular.

The prices on 0603 resistors are less than 0805s- in quantity (100K+)

0402 here we come... and those pesky 0201s are probably not far behind,
at least for resistors. Capacitors won't shrink as fast, for obvious
reasons.

Best regards

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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2002\02\15@192054 by Ashley Roll

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Hi Spehro,

Yep, unfortunately I still have to hand assemble some stuff.. 0603s are
about my limit there I think  :) Sometimes I think its a shame that the 1206
or 0805 size resistor arrays are so expensive (compared to the individual
ones).. 4 or 8 resistors in one go!

I wonder how long it will be until its easier and faster to just print the
resistors directly on the PCB during manufacture or assembly.. Does anyone
know if this is being seriously developed? I know there are a bunch of 3D
printing efforts..

Cheers,
Ash.

---
Ashley Roll
Digital Nemesis Pty Ltd
http://www.digitalnemesis.com
Mobile: +61 (0)417 705 718




> {Original Message removed}

2002\02\15@194630 by Spehro Pefhany

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At 10:18 AM 2/16/02 +1000, you wrote:
>Hi Spehro,

Hi!

>Yep, unfortunately I still have to hand assemble some stuff.. 0603s are
>about my limit there I think  :) Sometimes I think its a shame that the 1206
>or 0805 size resistor arrays are so expensive (compared to the individual
>ones).. 4 or 8 resistors in one go!

I calculate the break-even at two resistors for the 4-resistor 8-pin arrays!
I use LOTS of them, even for analog stuff. The price is good in quantity,
and the area/mounting cost is low. Plenty of sources. They can be hand-
soldered easily enough with a bit of practice.

Yes, I agree that 0603 is about as low as I want to go by hand.
Unfortunately, the PCB designs are committed to the size, so you can't
properly just use whatever's available at the moment without re-laying
out the board. 8-(  Not a problem if you're making cell phones with a
6-month design life, but for the rest of us..

>I wonder how long it will be until its easier and faster to just print the
>resistors directly on the PCB during manufacture or assembly.. Does anyone
>know if this is being seriously developed? I know there are a bunch of 3D
>printing efforts..

It's difficult- they used to make hybrids by screen-printing resistors and
firing on alumina. All the variables- it was hard to get 30% tolerance without
trimming. The cheap little 5% and 1% resistors are not bad for almost free!
But for consumer stuff, I think there are organic (low temperature)
compounds that you can print on and "fire" at reasonable temperatures- like
the carbon stuff that they use to replace gold-plating for silicone key
contacts, and for printed jumpers on low-end PCBs.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
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2002\02\15@222909 by Matt Pobursky

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Another *very* important point to remember concerning chip
resistors is power handling ability. I do a lot of industrial
designs where the resistor carries some current and dissipates
some power, often continuously under overload or error
conditions. They are also mostly high-reliability designs. Factor
in elevated ambient temperatures and things get a bit more
complicated as the power dissipation of the chip is reduced.

Remember that a 1206 chip is basically a 1/8W->1/10W resistor. I
don't like to run more than about 60% maximum power on any
resistor to reduce the maximum chip temperature and maximize long
term reliability.

Once you get to 0805, 0603 and 0402 chips, you begin to have to
worry about even LOGIC signals possibly damaging a resistor in an
overload state -- for instance a 220 Ohm, 0402 in series with a
PIC output to say a Mosfet gate. If the gate gets shorted to
ground and the PIC output is high (near 5V), the power in the
resistor becomes ~110mW and that will cook an 0402 resistor (or
even an 0603 and will be borderline on an 0805, depending on
ambient temperature). This is also something to remember when
sizing resistors for input overload clamping circuits. It's easy
to forget when designing with SMD chip resistors [not that I've
ever made that mistake ;-)]

I can see where the smaller parts will continue to be cheaper and
preferred over time, but I also see a need for the larger chips
for a long time also. I don't think they'll go away any time
soon, but I have started using 0805's wherever possible.

Matt Pobursky
Maximum Performance Systems

On Fri, 15 Feb 2002 19:21:14 -0500, Spehro Pefhany wrote:
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2002\02\16@033319 by Peter L. Peres

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>I wonder how long it will be until its easier and faster to just print
>the resistors directly on the PCB during manufacture or assembly.. Does
>anyone know if this is being seriously developed? I know there are a
>bunch of 3D printing efforts..

Printed resistors have been a standard for hybrid circuits for a very long
time. Several kinds of high volume consumer products use this all the time
(like pocket calculators and IR remote controls). If you have a high
enough volume and space constraints and strange resistor values then it
may be good for you.

Peter

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2002\02\18@063810 by Alan B. Pearce

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>and those pesky 0201s are probably not far behind,
>at least for resistors. Capacitors won't shrink as fast,
>for obvious reasons.

Hmm these require the use of face masks, I am told, because they are like
dust and are easily blown around.

Anyone for silicosis from 0201 components?

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