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Subject: Re: SMD popular component sizes

From: "derekhawkins" <eldata@...>
Date: 2006-01-27

> What would the changes be in the "modify them accordingly" step?

Using 0402 as an example. Here is a picture of a 0402 cap;

http://rocky.digikey.com/WebLib/Panasonic/Web%20Photos/ECD-GOE%
20Series.jpg

Here is a data sheet;

http://www.panasonic.com/industrial/components/pdf/abj0000ce8.pdf

Editing with your imported standard reflow layout, you would;

1. Lengthen the solder area as Leon indicated;

2. Shorten the width to just over .5 mm

3. Shorten the pad area beneath the chip so that the contact area on
each side of the chip ends where the pad ends under the chip. In
other words, for 0402, only about .5 X .2 mm (W X L1 or L2) of the
pad is under each side of the chip.

1 above allows for easy soldering and aids heat dissipation. 2 and 3
above allow for quick alignment along X and Y axes. Remember, you'll
be hand soldering so a layout pattern that facilitates sutface
tension centering is no longer applicable. If heat dissipation
requirements, say in the case of a resistor, are near the limit of
the device then either stick with the reflow pattern or use a bigger
package size with standard pad layout.

--- In Homebrew_PCBs@yahoogroups.com, Dave Hylands <dhylands@g...>
wrote:
>
> Hi Derek,
> What would the changes be in the "modify them accordingly" step?
>
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
>