On 6 January, Mike wrote:
> Has anyone had any experience applying epoxy to pcb's for 0603
> components.If so what is the suggested screen thickness and diameter
> hole typical for doing this. I have been screening 0805's and 1206's but
> never 0603's.
Hi Mike,
Hoo-doggies! 0603's? Man, that's getting down there for epoxy! I've never
gone down that small using epoxy.
But according to the IPC-SM-782 design standard, the gap between the pads is
the same for 0805's or 0603's, .6mm (.0235") minimum, .8mm (.0315") maximum, so
the same diameter that you're using for the 0805's should work (if all the
footprints are according IPC standards).
It's been my experience that it's been kinda' "dicey" for 0805's, ya' know,
ya' gotta' be very, very accurate even with 0805's or you'll wind-up with epoxy
"bleeding-over" onto the pads.
One thing I've seen before with bottomside passive pads, is to make them a
little narrower than the component termination itself. See below:
EPOXY DOT
/
/
_______ ,-~-,________
| ( ) |<------------COMPONENT
__________|_____ `-,-` _____|__________
| | | | | |
| | | | | |
| PAD | | | | PAD |
| | | | | |
|__________|_____| |_____|__________|
| ,-~-, |
|_______( )_______|
`-,-`
\
\
EPOXY DOT
With this type of layout, gettin' epoxy all over the pads is less of a problem.
The fillets that ya' get coming outta' wave ain't too bad...they'll kinda' fan
out and wet along the whole length of the termination making kind of a "wedge"
shape from the pad to the termination. It looks like a good solder joint to me,
(I ain't done no HAST on it though...), and the customer who used this passive
footprint design used it on all their products (they're pretty well known BTW).
All I know is it made things A LOT easier when doing bottomside 0805's, and we
didn't have ANY misalignment defects on the components that used that footprint
at all, the components were always 100% on the pads...so something like this
should work good for 0603's too....Good Luck!
__\/__
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# Steve Gregory #
# SMT Process Engineer #
# The SMT Centre Incorporated #
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#________________Oooo.__________#
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