Re: Green solder mask and heatsinking

In article <wm5Pk.7938$Dm5.1486@xxxxxxxxxxxx>, unknown@xxxxxxxxxx
says...

"Phil Hobbs" <pcdhSpamMeSenseless@xxxxxxxxxxxxxxxxxx> wrote in message
news:490CD7E1.7080401@xxxxxxxxxxxxxxxxxxxxx
If you're solder-plating the copper anyway, there's no reason not to open
the solder mask--the cost is no different, and the heat transfer will be
very slightly better.

Large areas of unetched copper is considered bad practice, especially with
Mil-Spec, because of the differing thermal expansion between the copper
laminate and the (typically fiberglass/epoxy) substrate. When large areas
are needed because of shielding needs or a ground plane for a stripline, the
etching pattern normally used is a grid or parallel traces which allow for
thermal expansion without the copper lifting from the board during reflow.
Unfortunately this means the loss of surface area for heat convection.

Interesting. Large pours are "normal" in some neighborhoods (I've
never done it) and certainly solid internal planes are the norm.
How do they get away with the differential thermal expansion
problem?

--
Keith
.

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