Hi Phil - oh, if I could only have an 90 mil board with 2 oz copper layers!
I routinely see pwb designs, primarily power supplies, which are 60  mils
 - 120 mil with 2, 3 or 4 oz internal layers. As your detailed, soldering
can be "an adventure" with these designs. A selective solder process is
your friend as it has the thermal mass to permit adequate soldering of the
PTH components.  There are many of these types of designs that manual
soldering is no longer a valid option (IMHO). You may have some luck with
reducing the number of internal layer connections and or how the PTH is
connected to the internal layer to make soldering slightly better. Good
luck.

Dave Hillman
Rockwell Collins
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On Mon, Dec 19, 2016 at 12:34 PM, Nutting, Phil <[log in to unmask]>
wrote:

> Hi All,
>
> We have several designs in which we use the thru-hole pad and surrounding
> etch to act as a heat sink for device heat being transmitted via the
> component leads.  Typically 2 ounce copper and often on 0.090" thick FR-4
> boards.  With the added copper thickness and larger pad area for better
> "heat sinking" we now introduce greater difficulty in getting a quality
> solder joint and don't get me started on the increased difficulty in
> removing a bad component.
>
> So my questions are:
> Is this a common practice?
> Does it really provide effective device heat sinking?
>
> Phil Nutting  |  HVP Development Engineer   |  Excelitas Technologies Corp
>
> Lab: +1 978.224.4332   |  Office: +1 978.224.4152
> 35 Congress St, Salem, MA  01970 USA
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>
>
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