enclosureinsulation
For a miniature product, I want the smallest possible product enclosure around the PCB. I figure I can get away with a 1mm thick metal sheet enclosure.
But I (probably) also need an insulator between the circuit board and the case, so nothing shorts out. What's the thinnest way I can make the inside of the metal case insulative? Paint? Powder coat? Paper?
As Steven says, that transformer is intended to be PCB mounted using its solder tags.
However, if you wish to mount it to the steel panel directly a very usual way is to add a "clamp" as seen below - copied from here. You could make something similar. In this case your wiring will be on one side and you would need to connect wires to it and insulate them for safety. Using a PCB arrangement will be easier in many cases.
The makers are in Carlsbad, New Mexico, USA, but people would be able to manufacture similar clamps easily in Turkey. Note the side portions which stop the transformer sliding out of the main loop. You could just make a simple square C sguare loop with feet relatively easily BUT the screws have to provided enough pressure and friction to stop the core sliding out sideways.
IF the core has mounting holes or IF it is stell and can be safely drilled, you can do something like below. If the core is ferriote it would pro=bably be destroyed by drilling. The method below and a number of others are shown here
(This answer refers to UK regulations, as the questioner is in the UK.)
Given 2MOhm resistance as discussed in your question, earth leakage current would be acceptable at 0.1mA.
Another point to consider is that the class-Y/class-X capacitors which are typically used for RFI suppression are put through safety testing, and are required to fail open circuit. The same may not be true of the resistors you choose to use.
According to the 16th edition wiring regulations, there is a limit on earth leakage current for class 1 appliances:
5.9.3
Maximum permitted leakage currents are listed in Appendix L of the 2nd Edition of Guidance Note 1, and vary from 0.25 mA for Glass II appliances to 3.5mA for information technology equipment (see {7.8.2})
Appliances with higher leakage must have warning labels and a high integrity earth connection.
7.8.2
Any piece of equipment having a leakage current exceeding 3.5 mA must be fitted with a label adjacent to the primary power connection which reads:-
HIGH LEAKAGE CURRENT
earth connection essential before connecting the supply
Best Answer
(1 mm steel is thick!)
The isolation may not be required, since you're probably (S)ELV. Anyway, it's not going to cost you much space-wise. I wouldn't mess with paint sprays and such. Agreed, it's the thinnest, but I assume you can afford the thickness of a 0.1 mm PP (PolyPropylene, PP has very low water absorption) sheet?
Try to use only SMT parts, and mount them single-sided. PTH components will add at least 2 mm because of the pins sticking out at the other side. A single-sided PCB may be glued directly onto the PP sheet, which in turn you glue to the bottom of the enclosure. If you manage to do the wiring of the PCB single-sided as well you don't even need the PP insulation. It may be worth using a couple of 0 Ω jumpers to ease the layout.
You can save an extra couple tenths of mm by using a 0.8 mm PCB instead of the standard 1.6 mm. The thinner PCB is less stiff, but at the small size it's not a problem, and when glued against the enclosure it won't get any mechanical strain anyway.