Toner Transfer for PCB

tssop20 CortexM0 PCB

Recently I get sight to back of my laser printer, old good HP 4P, and realized that there is kind of anniversary - 20 years of work. Fist 10 years was spend in publishing, next decade I've used it in  PCB prototyping and custom production up to A4 format size.
Usually people think toner transfer tech is kind of DIY methods, painful way to save some money. However, for me money economy not so important, like to save a lot of time and avoid worry.
Toner transfer allow me to complete whole cycle of  PCB design in my workshop, and make all possible mistakes (and correct it) before sending PCB file to board manufacturing service. Usually I need about 1-2 day to make PCB in service,  and a whole day to bring PCB back. And what a pity when returned PCB had an error! In my workshop all this design loop takes 10 min instead of 2-3 days. Considerable saving of time, is't it? For transport spendings and nerves too.
As a base for transfer at large sizes I use glossy back  paper from sticker film (waste product in front panel design). But for small sizes (and high accuracy) thin aluminum foil is perfect.
Key is right temperature, I always use digital measuring with calibrated thermo-pair, ±5° error may kills everything. For my type of toner optimal 105C°, but most of modern printers use more high temperature toner. Better way to buy laminator machine, but I haven't find yet the one, that can swallow some of my 2.5mm thick PCBs, without deep modification.
Etching in ferric chloride (or another solution, it doesn't matter) needs to be quick, not more than 3-5 min. If it becomes longer, make solution more dense.