How to protect circuit boards that must be exposed to weather?

I have another problem - display panels on an outdoor hammer game - the style that you swing a hammer at a pedestal and it lights up a column of LED panels with 8x8 graphics.
The one I am repairing was made in 2001 and it is breaking down. The surface mounted serial drivers are loosing connection to the PCBs from being thermally stressed over a couple of decades of outdoor use and I want to make replacement panels (the original company has abandoned the product) that will be more durable.
Currently on the rear (somewhat protected) side of the board is the electronics, covered (or course) with a conformal coating. The outer side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64 pixels on the panel.
There are 40 - 8 x 8.75 inch panels going up around 30 feet...
Is there a better way to solder on SMD devices to help avoid thermal solder failure? After connection corrosion, the biggest problem is solder failure of the SMD pads to the PCBs.
Thanks!
John :-#)#
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