Because Metal core Aluminum is conductor,could not fix DIP components.
Insulated holes technology is the solution to solve this problem.

Aluminum pcb with insulated hole Manufacturing  step:

step 1:
Drilled the big holes through the aluminum,

Step 2:
filled the holes by epoxy resin.

Step 3:

Lamination process,copper + high thermal conductivity insulation layer

Then drill the small insulated holes.