4
\$\begingroup\$

As shown in the photo below, the PCB design was sent for fabrication without the drill data. Is it still possible to drill the via holes so we can save the PCBs?

This is a 2 layer board, most of the traces are on the top, a few are below. Is it practical to send the drill file to a machining shop and have them drill the holes? Will the drill file already specify the holes, or is there a standard hole size which I can let the machining shop know?

enter image description here

\$\endgroup\$
  • 21
    \$\begingroup\$ What kind of useless supplier doesn't flag a missing drill file? \$\endgroup\$ – Spehro Pefhany Oct 31 '14 at 18:22
  • 3
    \$\begingroup\$ How many layers? Drilling through internal layers is likely to short them. \$\endgroup\$ – Matt Young Oct 31 '14 at 18:27
  • 6
    \$\begingroup\$ @MattYoung: That's the whole point of a via! \$\endgroup\$ – Dave Tweed Oct 31 '14 at 18:38
  • 13
    \$\begingroup\$ Please tell us which supplier this was so that I can make sure to never use them. \$\endgroup\$ – David Högberg Oct 31 '14 at 18:55
  • 2
    \$\begingroup\$ @MattYoung: The OP said that the only thing missing was the drill file, implying that everything else (the copper layers) had been correctly defined. \$\endgroup\$ – Dave Tweed Oct 31 '14 at 18:57
9
\$\begingroup\$

It will be possible to drill these if you have a very rigid drill press and carbide bits. Back the PCB up with a sacrificial piece of laminate, get bright light and safety glasses and get very close to get the holes near the center. Use the highest spindle RPM your drill press is capable of (30,000 RPM is not too much) and feed slowly, especially when the bits break through.

If your drill press is not rigid enough or the bits are the slightest bit dull, they will break off and can go anywhere, so safety glasses are not optional.

If you use steel bits (use the best cobalt steel if you try this) they may work okay, but they'll tend to skate around on the pad and not be in the center. Replace them every 50 holes or so as they dull in the glass laminate.

You'll still have to find a way to solder them on the top or add additional jumper wires from top to bottom. If that thing is a terminal block, for example, you'll have to add ugly jumper wires on the bottom to a number of the pads. It won't be pretty but it might help you debug.

I doubt it's economical to get a machine shop to do this unless the boards are very, very expensive or you're willing to pay a lot of money to compress schedule.

In the future, look at your files with a gerber viewer that includes NC drill files, make a checklist for what files have to be with a given number of layers PCB, and (IMHO) never do business with this supplier again.

\$\endgroup\$
  • 1
    \$\begingroup\$ Plus one for using a gerber viewer and verifying the drill data with the artwork \$\endgroup\$ – Some Hardware Guy Oct 31 '14 at 20:25
  • \$\begingroup\$ What gerver viewer will you recommend? \$\endgroup\$ – Nyxynyx Nov 1 '14 at 1:11
  • \$\begingroup\$ @Nyxynyx I generally use Camtastic (which comes with Altium) and in the past I've used CAM350 and Gerbview (Orcad), but there are also a number of free ones out there depending on your OS (eg. Gervb for Linux) and your preferences. Of course that doesn't help if you simply forget to include the file with the order, so I suggest a checklist. It generally takes 9 files to describe a simple 2-layer board, including a mechanical layer for the outline and a readme (not including P&P and paste layers if you're doing PCBA) so it's easy to omit one & delay the order. \$\endgroup\$ – Spehro Pefhany Nov 1 '14 at 7:34
5
\$\begingroup\$

The problem with drilling the holes is that they won't be plated. Normally the top and bottom rings are connected through the board. In addition to electrical routing, this allows strong solder connections.

In your case, these look like connector locations. When you solder the connectors in place, you'll only be making electrical contact with the bottom side. A few of your traces are connected to the rings on the top, so it's not going to work for you.

Another reason not to is if you are using a 4+ layer board. In this case, the inner layers would have exposed copper at the edge of the drill holes, which could cause problems.

Sorry for the bad news.

\$\endgroup\$
3
\$\begingroup\$

Drilling will be very difficult, you are very likely to strip the whole copper pad. Even if you drill it successfully you will have to solder a wire through each via on both sides. Have a new board manufactured, it's not worth the hassle. Plus you can improve your board, like adding labels to the connectors. Speaking about connectors, you won't be able to solder them to the top layer because you will cover the pad with connector, so you really need to make a new one.

\$\endgroup\$
2
\$\begingroup\$

I say go for it, (what do you have to lose?) As long as there are no internal layers that the vias need to connect to. A nice little drill and high speed. I've got some carbide tipped drill bits that won't dull when they go through the fiber glass. But for a one-of just throw away the drill bit when you are done. The copper layer may be interesting, (gummy) If you had a little starter drill, maybe touch the tops off the copper with that.

\$\endgroup\$
1
\$\begingroup\$

You can definitely do this; I've done it before. You just need patience and one of these:

enter image description here

Sit down at the bench and very carefully drill a little bit, then reverse and back out. Blow off the drill shavings and then repeat. Try to keep it straight up and down :)

I've tried and succeeded using a standing drill press, but it's easy to screw up that way. Sometimes the bit will catch your board or you put too much pressure on it and ruin it/break the bit.

By hand it takes a bit (no pun intended), but it lets you correct yourself.

Good luck!

\$\endgroup\$
  • 1
    \$\begingroup\$ also I see you have connectors, so you could: remove the plastic part and just insert the metal pins using the female as a guide. If they are females or you can't do that you could solder them standing a bit above the holes so you can make those topside connections. Or use some rework wire, superglue the connectors right next to them (takpak works great for this), and then jumper them over with some rework wire. \$\endgroup\$ – Some Hardware Guy Oct 31 '14 at 19:42
1
\$\begingroup\$

The best facility to attempt to salvage these boards would be a PCB manufacturer. Maybe you could send them back to the place that originally screwed up the order and ask them to drill + plate them in lieu of re-running the whole batch. Or if they're off-shore, find a local place.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.