Drilling PCBs

[Mark Hammer]

I simply put on a pair of really strong reading glasses, or more recently, my magnified headset with the flippable lenses.  Good lighting helps too.  I should probably make use of some of the superbright white LEDs I have and aim them at the drilling target.

Of course, the precision of the visual information available to the driller is only as useful as the precision of the chuck.  I use one of those $80 table-top drill presses.  The chuck is pretty decent, but maybe not as precises as I need it to be.  Though the precision would seem to be a function of the diameter of the shank inserted into it.

I used to tin my boards as soon as they were etched and buffed, and then drill them.  Over time, I came to the conclusion that sometimes the solder pads might be a little thicker here or there, providing inclines, and coaxing the bit to wander.

And THAT is why I have to go buy a bunch of new carbide bits this weekend.

I have since switched to drilling first, and then tinning.

[R.G.]

Copper may be opaque but there's no copper on the board where you want to drill provided you've etched first.

If and only if you have put proper-sized hole locating etches on the pads. I have some experience with getting it wrong both ways. 

[defaced]

A couple cool implementations that are variations on this basic theme:

http://www.imajeenyus.com/electronics/20080628_pcb_drilling_viewer/index.shtml
http://www.turtlesarehere.com/html/pcb_drill.html
http://www.youtube.com/watch?v=-ZguqDxH81k

[CodeMonk]

Copper may be opaque but there's no copper on the board where you want to drill provided you've etched first.

If and only if you have put proper-sized hole locating etches on the pads. I have some experience with getting it wrong both ways.  

Oh yes, I have gotten it wrong on more than one occasion.
And I've been doing a lot of double sided boards these days.
I've scrapped more than a few when first trying to do double sided boards.
That makes it even harder.
But John Lyons gave me a good tip for getting things lined up better. (This wasn't the post towards me, but this is basically what he said to me : http://www.diystompboxes.com/smfforum/index.php?topic=78081.msg642339#msg642339 )
This light table I found several years ago helps quite a bit.




I've been using a #62 carbide drill bit (0.0380 Inch, 0.9652 mm) and 0.8 mm holes sizes in DIYLC.
I've been thinking about changing the holes sizes in DIYLC.
I've been etching my own boards for about 5 years so I have gotten good enough with the iron to transfer the pattern with very very little "squish".

I also got a cat toy laser today. $2.99 at CVS Pharmacy
The beam is far to large to be able to use it as is to line up the holes perfectly.

I've got some double sided copper clad that has the cheap ass fiber as the board.
I mean the really crappy stuff.
I've just been using them for first run prototype on new layouts. Definitely not something I would use in something I would sell (Maybe for something I would give away though).
I'm going to glue a few together and use one of these to create a smaller hole to confine the beam :


That's the plan anyway

A couple cool implementations that are variations on this basic theme:

http://www.imajeenyus.com/electronics/20080628_pcb_drilling_viewer/index.shtml
http://www.turtlesarehere.com/html/pcb_drill.html
http://www.youtube.com/watch?v=-ZguqDxH81k

That second one looks interesting.
Except Chrome says I need to install a media extension, which gave me this message :

I don't think so.

[defaced]

I did not get that message with Waterfox (64bit Firefox), i wouldnt have posted the link if i had. I definitely wouldn't install it.

[R.G.]

A couple cool implementations that are variations on this basic theme:
http://www.turtlesarehere.com/html/pcb_drill.html]http://www.turtlesarehere.com/html/pcb_drill.html

I really like this one. Use the camera UNDER the drill press table and don't modify the drill press much. Use a clear plate over the camera to keep the drillings out, and blow air across it to clear the swarf (that's a technical term ).

At 15X, it's remarkably hard to find the next drill location to drill to. Not so much a problem for double sided, but for single sided, you're looking at the blank side of the board stock. I think I'd print a copy of the traces as seen from the top side where you're looking but not drilling, and tape it to the top of the PCB. This would let you align the board roughly at 1X by eye, then glance at the monitor for the fine adjustment of position to drill.

With a pedal to stroke the drill instead of a lever, you could use both hands to move the drill I suspect that you could drill a LOT of holes well with this thing and use the proper speeds as well.

[CodeMonk]

I did not get that message with Waterfox (64bit Firefox), i wouldnt have posted the link if i had. I definitely wouldn't install it.

I think it was just so I could play whatever video format they had on the site.
Nothing to do with the program or other info on the site as far as I can tell.
It still looks to be pretty cool though.

I have no problem installing most extensions, but that one seems to want a bit to much for my comfort.

[PRR]

> The copper pad is completely opaque to laser light.

Not for long; if the laser has POWER. (Hole may not be in the right place but it gets holy. OTOH a 2-power laser can aim then burn with perfect alignment.)

> trying to hold the PCB firmly enough

Use your thumbs. (I ass-ume the PCB-stuff is NOT so tough that the bit&board will grab and gash your hand.)

> Could be the long lever arm cuts the radius of movement down enough

We should also minimize the travel/swing. The drill-bit should be almost-grazing the bottom of the board while you line-up. In practical terms, much less than the thickness of the PCB board, or about a point-set, or matchbook-cover thickness (0.030" in numbers).

With the old plan I was thinking an NO switch above the platform to power the Dremel when you press-down the platform. With 0.03" slack this will be very difficult. I do think a foot-switch is in order. (No, not the typical stomp-switch; verify it is rated for 120V AC 3 Amps. The genuine Carling switches were, but a lot of imitators aren't.)

> A laser dot as small as the hole is probably OK.

Or an ice-pick. Sharpened to a needle point. (Or a needle; but I like the look of the ice-pick better.) Set this too about 0.03" above the board so you can rough-aim, then lift the platform a trifle to dent the pad and be sure you are spot-on. Then drop the board onto the bit.



Apropos: (warning: naughty language) http://www.smallpeculiar.com/?p=279

[Perrow]

How 'bout printing a crosshair ("positive" or "negative") on a transparency and projecting it with a magnifying glass?

Much like this.

Materials used, led(s) resistor(s), a piece of tube or a small box, transparency, lens (magnifying glass, lens from cheapo reading glasses).

You should be able to get descent focus (maybe experiment with "tilt/shift") and thin lines. I'll have to experiment some with this (and get a drill press ).

[Perrow]

If you just want a small dot, you should be ok with just a led (small but bright) a tube, and a lens (magnifying). Led at one end of the tube, the lens at the other. Say a 20cm tube (8 inches) and a bright 3mm led. Much like "those other kids" used to burn ants with a magnifier, but with a led.

No cross hair, but simpler.

[johngreene]

I've done hundreds of my own boards and I've always just made sure when I print the artwork it's set to the leave the hole in the middle of the pad open. As long as it etches even the most minuscule amount it will 'pull' the drill bit into the center. I always set the drill size in the layout software to be smaller than the actual drill bit size I'm going to use. Which means I etch first and then drill. The Dremel 'drill press' is sloppy at best. But I've tried using a 'tighter' drill press and ended up breaking a lot more drillbits. So the Dremel press seems to work the best in this case. Once I get the rhythm down I can crank through an entire board lickidy split. 
Resharpened PCB drillbits on eBay work great in a dremel and are cheap enough that breaking a few doesn't hurt much.

--john

[R.G.]

The Dremel 'drill press' is sloppy at best. But I've tried using a 'tighter' drill press and ended up breaking a lot more drillbits. So the Dremel press seems to work the best in this case.

The main bearing support on the collet end of the Dremel shaft is rubber in all the ones I've opened (-er, autopsied) so there's some compliance.

You can do much the same with a tighter drill press if you relax your clamping force on the PCB blank just as the drill bit contacts the spot. As the bit self-centers, it's as easy for it to pull the PCB stock to its center as it is for the bit to pull the drill press to the center of a fixed PCB position.

Lots of ways work, but starting a carbide bit on a non-copper side with both bit and board fixed is easy, if you can keep them fixed for the duration of the drilling.

[Gurner]

The Dremel 'drill press' is sloppy at best.

Agreed, which is why I suggested earlier that folks buy the Proxxon MB 140/S instead.

[davent]

Endoscope arrived from china-Я-us. ooh... need to trim those nose hairs, cool toy. Quick pcb snap handheld a couple inches above the board. Will focus physically closer or digitally zoom.



Using a generic webcam software from Oasis Scientific as the supplied was lacking.

Now need to rig it above the drillpress table and i should be good to go.

dave

[davent]

Bought one of the magnetic flashlight holders i linked to earlier to mount the 'scope to the drillpress. Found a small software utility that by hotkey turns my cursor into a full screen roving crosshair, center it on the drilled hole- hit another hotkey and it freezes the crosshairs  returning the cursor to normal.

Looking good- yet to be tested. Figure i'll get a thin sheet of polycarbonate with a tiny hole to use on top as a safe table and cover up the big holes in the drillpress table.

dave

[R.G.]

Bought one of the magnetic flashlight holders i linked to earlier to mount the 'scope to the drillpress. Found a small software utility that by hotkey turns my cursor into a full screen roving crosshair, center it on the drilled hole- hit another hotkey and it freezes the crosshairs  returning the cursor to normal.

Beauty.

[davent]

Thanks R.G.... just implementing your ideas, wouldn't have known where to begin otherwise!