----- Original Message -----
Sent: Tuesday, April 09, 2002 8:12
PM
Subject: Re: [TN] 0402 tombstone
problem
I just heard something
not too long ago, that round pads for 0402's are the way to go.
Never
heard of that before, but just recently received a board for quote that uses
round pads for the 0402 components...anybody else ever heard of
this?
Guess I'll find out how it works inna little while, while
pondering why a round pad would work better than a square
pad....
-Steve Gregory-
Edward,
When we do everything correct on 0402 and 0201
and still have components
standing-up, we often look to the component
terminations and find poor
plating.
Good luck
Dave
Fish
----- Original Message -----
From: "Edward S. Wheeler"
<[log in to unmask]>
To: <[log in to unmask]>
Sent:
Tuesday, April 09, 2002 10:59 AM
Subject: [TN] 0402 tombstone
problem
> Hi folks, we are running a new board with 0402 parts
on it. It seems that
> we are having a tombstone problem as well as a
problem with parts not
> staying centered on the pads. We are
currently using 20 mil square pads on
> the board, with 20 mils of
spacing between them. Our stencil is 6 mils
> thick, laser cut and
electro polished. The trapezoidal walled apertures
are
> slightly
reduced, 17 mils square, and centered on the pads. It appears the
>
chip shooter is placing the parts perfectly. We are using eutectic
solder
> paste with an OA flux, and reflowing the parts using the
recommended
profile.
>
> Are there any suggestions any of you
might have concerning this size of a
> part? Is there a better stencil
design, reflow profile, or pad design that
> could help us out? I
would appreciate any suggestions.
>
> Thanks.
>
>
Ed