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Milling PCB, components flipped

Posted: Mon Feb 29, 2016 9:32 am
by Auarhau
Hey.
So I milled my first PCB this weekend, and it was mostly a success. The board looks perfect.

BUT:
I designed everything on the top level. and when I go to solder it I have to put the components in from the other side (I can only solder on the copper side). And now everything is flipped over, so the IC pins no longer match etc.
I "solved" it this time by bending the pins on my IC around completely to the opposite side. Which made me cringe hard.. :o , but it worked. It also meant that all my careful placements of inputs and outputs came out completely in the wrong spot once I flipped the board :?

I realize this is a rookie mistake. But I wonder how people normally solve this? Is there a better way to work in Eagle so that this never happens. Or can I flip the board in software somehow before I send it to chilipeppr?

I'm hoping there is an easy way to deal with this so that I can keep the human error element to a minimum :mrgreen:

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 9:51 am
by xfredericox
you can't expect a machine or software to prevent a human mistake like that :-)

lesson learned, experience gained, so look at this as a positive thing! You won't be making that mistake again anytime soon i am sure.
Personally i would have redone it in order to also learn how to do it right.

Every graphic or CAD software has a mirroring command.

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 12:29 pm
by Auarhau
Maybe my question needs to be put more precisely. I don't expect anything, I am asking for the best practice on how to deal with this when milling PCB's. That said I'd be surprised if Eagle did not have some function to deal with this, I just haven't found out how yet.

So far my googling of the "problem" turns up nothing. Which is a little strange I think. This must surely be very essential in how to design boards for milling. Maybe it's obvious to everyone else... :lol:

Is the answer to mirror the board? If so, do you mirror every component and then draw the traces, or can you mirror the entire completed PCB after designing?

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 12:46 pm
by cvoinescu
If I have just one layer, I route it on the bottom layer, exactly as it will be on the actual board. Board manufacturers want all layers viewed from the top, and know to flip them for the ones that are manufactured with the board upside down. That keeps confusion to a minimum.

So, if you make the board yourself, you should flip the bottom copper layer, and the hole positions if you drill them from the bottom. As @xfredericox says, all layout programs have an option to mirror the board for you, but they can't know which layer needs to be mirrored and which doesn't for your specific process. Maybe you're using the toner transfer method, in which case the printout for the bottom layer must be as seen from the top; maybe you're using isolation routing, in which case you need the mirror image.

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 1:14 pm
by CrazyBillybob
Eagle should have (it did a long time ago when I last used it) option in the the print dialog to print mirrored. I had to use it when I was doing Toner transfer on some boards.
Some programs let you set the print mirrored for each layer (look in layer properties). I'm not really sure how Eagle does it now.


CBB

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 1:22 pm
by Auarhau
I don't know either. I'll work on it more tonight. Is flipping a layer the same as mirroring a layer?

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 6:36 pm
by Auarhau
Figured it out: File-> Run ULP -> Choose the "mirror-board.ulp" file and hit open.

I printed the mirrored one onto a piece of paper and tried the IC. The pins now match up as they should :D

See, I knew there was an easy fix. No redoing it! I'm very glad I don't have to juggle a mirror image of the board in my mind, it's hard enough planing it the right way up. :lol:
This way I can make the board the logical way (for me at least), as long as I remember to mirror it as the last step. I wonder if this is possible to include as a warning in the design checks.. ? I really like the different checks Eagle has. Really helps minimize the human error I was talking about. Automatically checks if something is too close or too small etc. Super helpful, and well worth looking into.

Also, printing it on paper first was a economical way of checking if I messed something up.

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 6:58 pm
by cvoinescu
The DRC (design rule check) doesn't help with workflow problems. It just ensures the board is laid out according to the rules, not that you do the right thing with the output...

Re: Milling PCB, components flipped

Posted: Mon Feb 29, 2016 7:15 pm
by Auarhau
cvoinescu wrote:The DRC (design rule check) doesn't help with workflow problems. It just ensures the board is laid out according to the rules, not that you do the right thing with the output...
I hoped I could be able to add some checks of my own. Would be a nice feature. I think I'll be printing it on paper first from now on, so that should work as a pretty fool proof check in any case.