Author Topic: PCB design problems  (Read 846 times)

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Offline AzraelsTopic starter

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PCB design problems
« on: March 07, 2013, 12:02:01 AM »
I think I've got the laser printer/ iron on pcb board down although it took more than a few tries. So tonight I finally have a board I was satisfied with and I go to start drilling my holes and the vias  start ripping up as soon as the drill bit touches them. Seriously frustrating! I have used Eagle, the lite version, to design the board which is a driver for two steppers and an H-bridge. I have been using the pinhead library for my headers which is just the standard headers you use with arduino boards. I do know how to edit the libraries after reading another post on here, thank you Soeren.

I thought maybe  to re-size to a larger hole might help but I'm not for sure.  After googling I have read to make the drill hole smaller. I would really rather not make another new board for experimenting. So I just wanted some more opinions.
My drill bit for the headers is 1/32" or .0370" on the caliper. The only smaller size I have than that is 1/64" which is to small for the headers.  But it still ripped up the vias for the resistors and chips!
When the bits dont rip up the vias they still deform the copper on the other side of the board when the bit pushes through. I have tried using a backer plate.
The drill press is set at its maximum speed which is 3100 rpm.
Hope you guys can help me out!
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Offline Jon_Thompson

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Re: PCB design problems
« Reply #1 on: March 07, 2013, 07:41:33 AM »
If the pads on the back side of the board are pulling up, it sounds like a registration problem. The hardest part of making PCBs at home (I've always found) is getting the vias to line up. I use a hand-held battery drill and angle it as I go to compensate for this problem. It's a good idea to add an extra pinhead to the board so that you can drill it first to work out how to compensate.
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Offline jwatte

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Re: PCB design problems
« Reply #2 on: March 07, 2013, 11:09:39 AM »
In typical machining, you want to drill first, then cut. This is so that the drills go through as rigid a piece as possible. I recommend doing that for home-made PCBs, too.

Also, you may be able to "spot" the holes from both sides, and drill through half the board, without coming out the back, from each side, for less punch-through problems.

Finally, the quality of your drill bit does make a difference. Try different brands and cuts. I'd probably stay away from big-box brands like DeWalt or Bosch or whatever for drill bits -- they are overpriced and underperforming. Go to a hardware supply store and see what they have. Maybe even use a high-quality center cutting (or ball) end mill instead of a drill, for more precision in the cutting surface, assuming you have a rigid holder ("hand drill" doesn't sound like it, though :-)

Regarding the "I'd rather not make another board" comment -- when you're learning something you haven't done before, you *have* to plan to try several times until you perfect the skill. That's how learning works :-) And, because of all the annoying parts of making a home board (be it etched or milled,) I've switched to using OSHpark.com (formerly dorkbot-pdx) and iteadstudio.com for making my boards. The boards are 100x nicer than I can make at home, and actually work :-) A two-week wait is well worth it.

Offline AzraelsTopic starter

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Re: PCB design problems
« Reply #3 on: March 07, 2013, 12:10:04 PM »
Thank you Jwatte, I had been considering drilling all the holes first, but didnt know if this might actually weaken copper around the holes when the acid is doing its job.
I have also gone in and edited all of my common components making the drill size slightly larger and the pads/vias larger.

And yes I know I have to experiment, this will be about the 4th remake of this board, I just hate  "reinventing the wheel."

Will see how this one goes.
If your first post is, "I want to build a super complex robot with object recognition, etc..but I have never done programming or electronics...etc." 
Your doing it wrong. Start Simple and Work Up.

Offline AzraelsTopic starter

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Re: PCB design problems
« Reply #4 on: March 07, 2013, 12:12:59 PM »
If the pads on the back side of the board are pulling up, it sounds like a registration problem. The hardest part of making PCBs at home (I've always found) is getting the vias to line up. I use a hand-held battery drill and angle it as I go to compensate for this problem. It's a good idea to add an extra pinhead to the board so that you can drill it first to work out how to compensate.
Thanks, I will have to try to angle the table on the drill press and see if that helps
If your first post is, "I want to build a super complex robot with object recognition, etc..but I have never done programming or electronics...etc." 
Your doing it wrong. Start Simple and Work Up.

Offline Billy

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Re: PCB design problems
« Reply #5 on: March 08, 2013, 02:43:37 PM »
I've switched to using OSHpark.com (formerly dorkbot-pdx) and iteadstudio.com for making my boards.

Never heard of these places but OSHpark looks like a really cool idea.  I have to give them a try. I've never tried PCB123 for home projects due to the cost. My least favorite part of doing electro-mechanical stuff at home is making circuit boards. As someone who only spends a few hours here and there on the hobby, 2-3 weeks is an easy wait for me as well. If I was younger or had more time to spend on it, that wait would bother me.

Offline ErikY

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Re: PCB design problems
« Reply #6 on: March 08, 2013, 02:57:20 PM »
Are you truly using a via? meaning 2 sided PCB to connect one layer to the next?

I have been avoiding dual sided at all costs, and have even had a few boards where I needed to run about 5 or 6 jumpers since there was no way I could do a one sided board with all of my wires done on the PCB.

I have never had this happen to me, I wonder if this is not a quality of board issue?

Possibly you are heating to long when transferring the toner to the board?

I always use a dremel and a 1/32 dremel bit for all of my holes to start, and then if I need them bigger, I increase to the final size.

Offline AzraelsTopic starter

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Re: PCB design problems
« Reply #7 on: March 08, 2013, 04:23:21 PM »
Success!!!! ;D
I had my doubts about drilling first because of every other website saying to drill after you etch, but it worked fine. Maybe even the thing I was worried about turned out to be to the benefit because the acid ate away the roughed up copper around the drill holes leaving a nice clean hole. The resist actually worked better at centering the bit, that stuffs pretty hard!

Are you truly using a via? meaning 2 sided PCB to connect one layer to the next?

I have been avoiding dual sided at all costs, and have even had a few boards where I needed to run about 5 or 6 jumpers since there was no way I could do a one sided board with all of my wires done on the PCB.

I have never had this happen to me, I wonder if this is not a quality of board issue?

Possibly you are heating to long when transferring the toner to the board?

I always use a dremel and a 1/32 dremel bit for all of my holes to start, and then if I need them bigger, I increase to the final size.
Actually I was confusing via and pad. It was ripping up pads. I am making double sided boards and this is my first one using IC's. I haven't had any aligning issues yet. I just hold the two magazine sheets up to bright light, I leave a bit of excess paper, align the holes, hold it tightly in place, staple paper together at different places (not on the design area of course), place the board in the sleeve again holding up to light to check placement, then iron on.

You could be right on the issues of quality of board, or leaving the iron on it to long, or possibly it was even in the etch to long but I think Im gonna stick with this method now as it worked well.

The only thing I had would have done different was going ahead and pushing the drill bit on through. I did half the board only going half way through then switch to the other side. I got impatient with this after awhile and switched. It worked fine.
And also I learned a lot more about Eagle than I did before this problem.
« Last Edit: March 08, 2013, 04:28:30 PM by Azraels »
If your first post is, "I want to build a super complex robot with object recognition, etc..but I have never done programming or electronics...etc." 
Your doing it wrong. Start Simple and Work Up.

Offline voodoo

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Re: PCB design problems
« Reply #8 on: March 08, 2013, 09:48:14 PM »
I have used most ways of pcb making. I prefer to print on acetate & use a uv box. The pads & lines come out spot on with some practise. I have built a tiny robot thats got amazing circuits in this way ;D

Offline ErikY

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Re: PCB design problems
« Reply #9 on: March 09, 2013, 09:37:11 AM »
Success!!!! ;D
I had my doubts about drilling first because of every other website saying to drill after you etch, but it worked fine. Maybe even the thing I was worried about turned out to be to the benefit because the acid ate away the roughed up copper around the drill holes leaving a nice clean hole. The resist actually worked better at centering the bit, that stuffs pretty hard!

Are you truly using a via? meaning 2 sided PCB to connect one layer to the next?

I have been avoiding dual sided at all costs, and have even had a few boards where I needed to run about 5 or 6 jumpers since there was no way I could do a one sided board with all of my wires done on the PCB.

I have never had this happen to me, I wonder if this is not a quality of board issue?

Possibly you are heating to long when transferring the toner to the board?

I always use a dremel and a 1/32 dremel bit for all of my holes to start, and then if I need them bigger, I increase to the final size.
Actually I was confusing via and pad. It was ripping up pads. I am making double sided boards and this is my first one using IC's. I haven't had any aligning issues yet. I just hold the two magazine sheets up to bright light, I leave a bit of excess paper, align the holes, hold it tightly in place, staple paper together at different places (not on the design area of course), place the board in the sleeve again holding up to light to check placement, then iron on.

You could be right on the issues of quality of board, or leaving the iron on it to long, or possibly it was even in the etch to long but I think Im gonna stick with this method now as it worked well.

The only thing I had would have done different was going ahead and pushing the drill bit on through. I did half the board only going half way through then switch to the other side. I got impatient with this after awhile and switched. It worked fine.
And also I learned a lot more about Eagle than I did before this problem.

Glad to hear you got it working.

I will try out that method for lining up, maybe I will do a simple board just for test purposes to see how it works. Thanks for the tip.

Offline felipe80

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Re: PCB design problems
« Reply #10 on: May 16, 2013, 02:07:25 PM »
For Pad size calculation use this formula.
Minimum Pad size, P = (2 x R) + FA + D
P = Pad size, R = Annular ring, FA = Fabrication allowance, D = Drill or tool diameter

For hobby level PCB design, add 1 to 2 mm to drill size to get the Pad size. 

Offline tinkerbee

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Re: PCB design problems
« Reply #11 on: May 17, 2013, 02:02:07 AM »
I know this is probably stupid but would it be possible to use a conductive pen for spot repairs?

 


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