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Homebrew_PCBs@yahoogroups.com, "John" <jferrell13@...> wrote:
>
> This has become a humpling experience!
I use acetone to clean my boards. Most types of paint/lacquer thinner, mineral spirits, etc seem to leave an oily film. That would be my first guess as to why you can't get the toner to stick. My general procedure is to first use a 00 steel wool-like material to clean off the oxidation and rough up the copper (it's not actually steel wool but some composite), then I use acetone to wipe it clean.
I then print using HP high resolution toner on glossy old magazine paper. I find it needs a temperature of about 260-270F as the sweet spot for transfer. That is about the middle heat setting on my iron, verified with my thermometer. Most people recommend way too high a setting but maybe it depends on the specific toner and/or iron used. When using an iron I put very little pressure on it because too much that causes the toner to deform. I mostly use just the very front tip end of the iron along with the edge of the iron to try to get every place on the board. I use a piece of wood under the PCB when ironing. The wood doesn't pull away much heat and it keeps the board flat.
That works pretty good but I find using an iron can be difficult to get even pressure on every single part of the board. Instead I'm experimenting with using a hotplate (or normal non-inductive electric stove) with an 1/8" aluminium plate on top. I first tack the paper with toner on the PCB using an iron (just a quick pass to make it stick in place) then I put the PCB on the hotplate and once it reaches the correct temperature∗ I press the toner on with a piece of neoprene (I need to make a neoprene roller). Because the neoprene is soft it helps me press evenly around the board and prevents me from putting too much pressure so I get perfect sharp traces. I spend a good amount of time pressing around everywhere on the board. I haven't perfected this technique because I just started using it but I'm getting close and it's much easier to get 100% transfers than using an iron.
∗ I find that I can't get a reading from bare aluminium with my IR thermometer so I check the temperature of the PCB board itself.
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0.8mm is fairly standard for most holes.
1.0mm for "normal" larger parts like some diodes, headers, etc.
Those two are by far the most common for me.
Then 1.2mm and larger for large (power) headers and such.
If you use PCB software then you should be able to check the exact hole size in there.
I use a small drill press at the maximum speed I can get it to run (only about 1700 RPM). With a slow steady hand and a firmly held board it works fine.
I agree that drilling holes is a huge pain (especially hard to aim perfectly in the center while viewing at an angle) which is the reason I try to do everything surface mount if I can.
Dev