Re: Future: 0603 versus 0402 parts

See commonts inserted below:

"Joerg" <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:SNGJh.8099$P47.7027@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Spehro Pefhany wrote:

On Tue, 13 Mar 2007 22:51:16 GMT, the renowned Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:


John Larkin wrote:


On Tue, 13 Mar 2007 21:01:41 GMT, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:



Ok, have to decide whether to default to 0603 or 0402 for resistors
and
stuff on a new design. Wow, this time I am not size constrained.

Looking at Digikey it comes up with 143 pages (has risen) for 0402
resistors and 218 pages for 0603. Looking at prices 0603 still has a
leg
up, around $0.003 for a 10K while its 0402 counterpart runs about
twice
that. Is 0603 going to be a good choice for the next years? Or better
stick to 0402?

Of course from a debug point of view I hate to deal with 0402. With
chips the situation seems to be more clear cut. Things definitely seem
to be going TSSOP there.


My production people hate 0402's... they tombstone a lot. We still use
0805's when there's plenty of room, 0603's for tight stuff, occasional
0402's for picosecond stuff where it matters.


Hmm, I never had tombstoning with those. OTOH nearly all my clients
contract out circuit board stuffing so they don't have to bother with
that. Sometimes even the whole production. Sometimes I have a chat with
the contract producers and they'd tell me if they weren't happy with
parts of a design. Like when zeners began to miss data *** limits I
had an instant email from China about it.


I saw some 0402 tombstoning on a fairly recent batch of boards from a
China assembly facility (SnPb process). Zero problems with the 0805s
(no 0603s on that design).


One of the problems with a mixed design (where there are also some large
devices on the PCB) seems to be the paste. Too much and you get
tombstoning, too little and the big parts won't solder reliably.

I have never seen this problem, and have produced a lot of boards with a
large variety of parts. Ever see 1206's, 0603's, 0402's, a few 2220 caps,
QFN's fine pitch QFP's and BGA's all on the same board? Or fine pitch BGA's
with all 1206's? We just did a fairly complex board with 0.4 mm pitch parts
(those are not nice), tons of 0.5 mm pitch parts including large QFP's,
SOIC's, DPAK's, littered with 1206's a few 0805's and some 0603's. It's all
in designing the footprints and solder paste stencil correctly.

Like
those pellet stoves where they haven't figured out how to automate
intake air. Throttle too high and it'll go out on "1". Throttle too low
and it'll smoke on "3" or higher.


You can still buy lots of 1206's and 2010's and such. They're not
going away.


Good to know, thanks.


You may not like the price, though.


Actually a 1ohm 1206 costs roughly the same as a 10K in 0402, around
$0.007. A 2010 size can pop to several cents. Still, I don't see a
reason for anything larger than 0603 unless it is in a current sense
path or RF bridge.

See comments in other post! 1206's are about 1.5 to 2 times as expensive as
an 0603. Don't use Digikey prices for production prices. 1210's are for
specialty purposes, eg voltage / wattage / capacity issues.

Jeff


[...]

--
Regards, Joerg

http://www.analogconsultants.com


.

Quantcast