Andrew wrote:
>>>Me wrote:
>>>The CNC drill is a MUST. It is the only
>>>sensible way to drill holes before etching.
>>
>
>>Derek with the nice photos wrote:
>>It's the only sensible way to drill holes IMO.
>>But drilling before etching makes no sense to
>>me.
>
>
> Drilling before etching is what you HAVE to do
> if you want through plated holes or multi layer.
>
> Drill holes in blank copper
> activate the holewall
> Plate the holes through
> Apply the photoresist
> Develop
> Etch
> strip
>
>
>>CNC drilling seemed to have been high on
>>wish lists in the group until the resident
>>machinist declared that any backlash greater
>>than .001" (or some similar nonsense from his
>>textbook) just wasn't going to cut it.
>>Surprisingly, he seems to still drill by hand.
>
>
> I reckon I woudl be happy with one thou
> backlash. And if I was not happy with it I
> reckon I would just always approch a hole from
> the same direction.
>
> CNC is a must I feel fot PTH. If you don't
> have CNC you have to do and extra photo
> development at the start to act as guide to
> drill by.
>
It makes no real difference if boards are PTH or not, both need similar
hole accuracy. If you're doing 'tent and etch' boards (as you described
above) then you must position holes well within the pad boundary or else
the resist film cannot successfully tent the hole. For 'pattern plate'
boards you can drill a hole wherever you feel like and still have it plated.
PATTERN PLATE
----------------
drill holes on blank board
apply photo resist
expose/develop
electroplate copper
electroplate 2~6um tin
strip resist
etch copper
I cannot comprehend the justification for a hobbyist owning a dedicated
CNC PCB drill who, on average, makes no more than 1 PCB/fortnight. A
well built hand drill press does the job. And, especially since
everything is SMD (or soon will be), the only things left to drill are
connectors, power components, and of course vias.
Adam