Wall thickness of 1.8 to 2.25 should be good enough. But to provide a good strength, have integral ribs outside the box. The more closed ribs, more strength to the case.
PCB Overmolding is required. In Past, we had used PA678 material with low pressure molding provision. But it attracts moisture through cables inside PCB. What should be the best alternative to avoid moistures. Now we are looking similar low pressure molding but need to avoid moisture inside...