The cut in the board, near the middle of the picture, helps to get higher voltages. In the pic above, there is a high voltage cap across the gap. There is another high voltage component near the top left.
Although the solder is not as good a conductor as copper, it does compensate by sheer volume. The solder line can be about 1mm thick. If the copper foil gets hot, it simply delaminates (it is stuck wtih eopxy glue). This is a good trick for many boards based on paper phenol (bakelite) boards.