.:madworm:.'s photos with the keyword: cut

and fully cleaned.

So far I've managed to kill 5 of these PT4115 LED drivers, and I don't think that I've abused them - at least when compared to what I've done to other devices that survived no problem. The failure mode is very consistent. Either it stops working altogether (no more switching, output switch permanently open) or the output switch is permanently closed and the LEDs suffer over-current. Common to both manifestations is that the DIM pin shows unusually low resistance (about 6Ω) to GND. This makes me believe that this pin gets trashed somehow. Therefore I will test if adding a Zener + dropper resistor will help to protect the chip. Voltage clamping at 5V1 definitely works, so lets see how things go. Adding a Zener + resistor is the way to go. No more premature demise.

The result is pretty good. I think I could use an even smaller tool (spear-point drill). Using sub-1mm fluted end-mills can get a bit tricky, especially if they're not of the short and stubby kind. They break quite easily - and cost a lot.

1k dropper resistor + 5V1 Zener diode BZX84C5V1.

I shouldn't be able to say this, but I AM surprised how small these traces actually are. I will need to use a magnifier to be able to cut them - if the blade is narrow enough...