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Re: gEDA-user: IPC standard SMT footprints (0603, 0402 vs. RESC0603N etc.)
On Wed, May 25, 2011 at 7:56 AM, Gabriel Paubert <paubert@xxxxxxx> wrote:
> On Wed, May 25, 2011 at 07:11:49AM -0700, Colin D Bennett wrote:
>> On Wed, 25 May 2011 06:41:26 -0700
>> Colin D Bennett <colin@xxxxxxxxxxx> wrote:
>>
>> > (1) Why is RESC0603L/N/M much smaller than '0603'?
>> > (2) Why is there no similarly named set of RESC0805L/N/M for 0805
>> > size? (3) Why does RESC1608M nearly match the '0603' footprint?
>> > Â Â Is there an imperial/metric naming confusion happening? ÂI thought
>> > Â Â 0603 was a standard name for this size.
>>
>> I think I've answered some of this for myself... from Wikipedia's
>> âSurface-mount technologyâ article:
>>
>>   01005 (0402 metric) : 0.016" à 0.008" (0.4 mm à 0.2 mm)
>>   0201 (0603 metric) : 0.024" à 0.012" (0.6 mm à 0.3 mm)
>>   0402 (1005 metric) : 0.04" à 0.02" (1.0 mm à 0.5 mm)
>>   0603 (1608 metric) : 0.063" à 0.031" (1.6 mm à 0.8 mm)
>>   0805 (2013 metric) : 0.08" à 0.05" (2.0 mm à 1.25 mm)
>>   1206 (3216 metric) : 0.126" à 0.063" (3.2 mm à 1.6 mm)
>>
>> So the source of the confusion over footprints is that '0603' is a valid
>> name for both a metric and an imperial size.. both different? ÂWhoever
>> decided to name the packages that was must have been on crack.
>
> Indeed. I found a set of recommended footprints that distinguishes
> resistors from capacitors:
>
> http://www.ibselectronics.com/pdf/pa/walsin/smt_notes.pdf
>
> I have used it quite successfully, including for long edge
> capacitors (0612 or 1632 metric) and 4 resistors in a single package
> (4x0603 or 4x1608 metric). I also took into account the recommendations
> on page 10 when ordering the stencil, shrinking a bit the solder paste
> apertures generated by PCB.
>
And don't forget Tom Hausher's blog series on the subject "PCB Design
Perfection Starts in the CAD Library":
http://blogs.mentor.com/tom-hausherr/blog/2010/07/08/metric-vs-imperial-measurement-systems/
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