Guys, I think that the 'blistering' - as you call it occurs whenever the
copper is first plated, and then covered with soldermask.

When the board goes through Assembly process, it is often times put in
'reflow', and the solder under the soldermask also reflows - hence the
uglies. You would have this 'uglies' effect even if you did cross-hatching.

If you specify SMOBC 'SoldermMask Over Bare Copper', you do not get this
effect.

Regards,

James Jackson
Oztronics

> Dear Ted Tontis,
>
> Ted Tontis <[log in to unmask]> on 2001-06-14 12:15:59 PM further
clarified:
> >        isn't the crosshatching on the outer layers primarily used to
avoid
> >blistering?
>
> Every FR4 board I've done for the past 2 years has had a big (covering
roughly
> 1/8 the entire board) solid (not cross-hatched) polygon on an outer layer
> (opposite the component side). I haven't heard of any problems with it.
Over 5
> years ago, I saw some boards with ugly-looking wrinkles in the green
solder mask
> over solid copper areas. It was merely a cosmetic blemish, it didn't
affect
> functionality -- but even that doesn't happen with modern LPI solder mask.
There
> is no longer any reason to do crosshatching.
>
> >A sold plane (large plane >2mm) would hold the heat from the
> >reflow process, or wave, and possibly damage the sub straight?
> >
> >Ted
>
> That's not a problem. Check out page...
> [Flips through reference book] I thought I could turn right to the page
that
> explained proper ``copper balancing'', but I can't seem to find it just
now.
> Does anyone know a web page or some other reference to explain proper
``copper
> balancing'' ? Maybe I've just been lucky in this area.
>
> --
> David Cary
>
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