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"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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