look like very effective heat sink, that is part of the reason you have
difficulty soldering... (few on the net will tell you insufficient ground
soldering could occur if pre-heat is not long enough... same reason). 
IMHO.
> 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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