This person warned me that using this type of device on a custom PCB without proper "clearance" (?) could be dangerous.
2. PCB Design. There are specifications on trace to trace and pin to pin separation and trace widths and wire gauges on PCBs when routing power, especially at higher voltages (including 120VAC) and/or at higher currents.The latter is more likely to what they were referring, but the first is also important to keep in mind when you stuff a lot of stuff that is capable of generating heat in a small box and then place it in a (potentially) insulated environment (like an insulated wall) such that only the face provides any heat transfer area.