You did not describe what kind of problem the contractor mfg is
having for mounting chips.

To design a proper chip component pad, you have to know that
the amount of solder for reflow is controlled by the thickness of
solderpaste stencil and for wavesoldering is controlled by the
amount of smt pad exposure to flowing molten solder.  Therefore
a smt chip pad for wavesoldering application should not be as
for smt reflow.

The idea is to have a maximum exposure of smt pad for
flowing molten solder but too much exposure produces
excessive solder joints or solder bridges.  To work around this
problem, a chip smt pad for wavesoldering is designed to be
narrower and longer than pad for reflow.   For example, you
mentioned 603 pad size of 0.036 x 0.043.  The size of 0.025(to
0.030) x 0.060 is better suited for wavesoldering application.  I
recommend 0.030 gap btw pads.  Glue dots should be placed
off-centered to prevent smearing of it into pads.

I hope this will help.  1206 and 805 are better suitable for gluing
and wavesoldering than 605.

mpark
NII Norsat Intenational Inc.

>>> "E.A. Speer" <[log in to unmask]> April 3, 1998  5:03 am >>>
I would like to know the pad geometries my colleagues are
using for
resistor and capacitor sizes 0603 and 0805 in relation to reflow
and
wave solder.

My ops manager insisted on a deviation from IPC specs in the
gap
dimension for 0603 caps.  His edict was to use 0.036 X 0.043
pads with
0.074 center to center and a gap of 0.038.  Our contract
manufacturer
requested a gap of 0.040 between pads to facilitate their glue dot
dispenser.  Now, to their surprise they are having problems
mounting the
caps.

Thanks in advance for all replies.



> E.A. Speer
> Artwork Engineer
> email: [log in to unmask]
> Telephone: (770) 246-8684
> Fax: (770) 246-8765
>
> American Megatrends, Inc.
> 6145-F Northbelt Parkway
> Norcross, GA  30071
> Telephone: (770) 246-8600
>
>
> http://www.ami.com
>
>

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