revisiting the 1000 faces of 0402
Werner Almesberger
werner at openmoko.org
Sun Jan 23 07:46:41 EST 2011
Adam Wang wrote:
> I would also recommend to read this[4] Soldering Capacity to know more
> Hand/Flow/Reflow soldering types and Vapor phase/InfraRed/Convection oven
> reflows even I realized you have referred to an IPC-7351B.
All the literature agrees that flow/wave doesn't go along with QFN.
In the various data sheets I consulted, I've seen IR reflow only
mentioned once (page 10 of [4]), and it came with huge tolerances
and was only for 0603. I haven't seen any vapor vs. convection
references. Convection sounds like the most common these days, no ?
> [2] http://en.qi-hardware.com/wiki/File:M1_RC2_Stencil.dxf
Hm, QCad doesn't like this one :-( Anyway, the footprints I picked
are pretty much what everybody recommends in the case of 0402, and
well within the range of recommended values for 0603.
> [ IPC paper ]
Thanks ! I found only one significant difference, and that's the
width of the 0603 footprint. According to the paper (*), it should
be no wider than the component itself, e.g., 0.8 mm. Industry
choices are 0.8 mm or 0.9 mm, with only Taiyo Yuden daring to go to
0.7 mm.
(*) Page 4, "Testing done in Japan in the late 1970's indicated [...]"
Perhaps the answer lies in the tolerances (all 0603):
Package width Footprint width
Panasonic [1] 0.75/0.8/0.95 -
Vishay [2] 0.75/0.85/0.95 -/0.9/-
Taiyo Yuden [3] 0.7/0.8/0.9 0.6/-/0.8
Yageo [4] -/0.8/0 0.75/0.9/1.05
Lite On [5] * 0.7/0.8/0.9 -/0.8/-
* The soldering terminal is only 0.60/0.70/0.80
The 0.9 mm may simply represent a slightly more pessimistic view
on the tolerances. In all cases where complete data is available,
Package(max) <= Footprint(typ). This is also true for the 0.9 mm
width I picked for 0603.
[1] http://industrial.panasonic.com/www-data/pdf/AOA0000/AOA0000CE1.pdf
[2] http://www.vishay.com/doc?20035
[3] http://www.yuden.co.jp/ut/product/pdf/djmk_e.pdf
[4] http://www.yageo.com/exep/pages/download/literatures/UPY-C_GEN_13.pdf
[5] http://optoelectronics.liteon.com/en-us/api/DwonloadFileHandler.ashx?txtSpe
cNo=DS-22-99-0151&txtPartNo=LTST-C190KRKT
- Werner
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