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Bottom Layer Component Population

Former Member

Hi All,

 

I have recently been using Eagle for a slightly more adventurous design, where SMD components are to be placed on both sides of the multilayer PCB. This is possible with the wonders of modern assembly techniques, where one side of the board is maintained under the melting temperature of the solder paste and the other is allowed to re-flow. Sweet tech guys.

 

Having driven into a whole world of pain with Eagle recently with Hierarchical Design (see my previous post Eagle 7 Hierarchical Design - REPLICATING LAYOUT BLOCKS), I was dismayed to have the rug pulled from under me again by the latest massive Eagle Fail, namely that of properly instigating reverse side component placement.

 

Here are a few positives to temper the, well erm TEMPER.

 

Thanks for the Eagle 6.x-7 upgrade guys. sweet install and some nice enhancements, 100% stable so far and I love the general way Eagle works. Managed after some sideways steps to import some lovely curved traces from Illustrator to wrap around curves in the PCB design, have successfully exported to .dxf etc. Its a little limited, but all good so far. Just been playing with Design Link, which is useful. Funny how it only offers Farnell as a supplier...........

 

To keep it simple, here's the workflow:

 

0) Spend £500 on Eagle, (with the likelihood of needing to double that to make the larger board design I have in the pipeline).

1)  Create a myriad of components

2)  Create a schematic

3)  Jump over to the layout and start populating the board with all the fun of summer

4)  Periodically select and [mirror] the bottom side placement components, such that the pads switch from top copper to bottom and the outlines, document, silk etc flip respectfully over to their appropriate layers

5)  Spend another two weeks piddling around getting all the intricate details taken care of and drawing up BOMs etc

6)  Run the final Gerber data past the board houses and get the green light

7)  Upload the gem of a design to the supplier.

8)  Take a break before pressing go

9)  Take one final glance and scratch my head as to why a transistor has its Gate and Source swapped on the layout

10) Hit the roof.

 

The mirroring of components, although it shows all the signs of switching the components to the under side of the PCB, does not do this. It leaves all the connections reversed and there is absolutely no satisfactory way of resolving this. (enter embarrassingly obvious solution here PLEASE)

 

(caveat: it's 'fine' if you just want to mirror two lead components, as the effect is not seem as long as their pads are symmetrical)

 

I am completely perplexed, surely the core functional reason for flipping components over is that they are usefully represented after the flip. Why would I want to flip an op amp and thence leave it essentially perfectly ready to be assembled on the top side of the bottom copper layer. Yes, literally inside the FR4 material on the reverse side of the pads. That my friends is mind bogglingly stupid.

 

The only solutions I can find are:

 

1) Create new versions of all the components I want to place on the reverse side with bottom copper pads in place of the top copper ones and wire them all up, supply all the attributes etc. This sucks, as the time involved is much longer than the time it is going to take for my to write this post, run around the yard screaming, spend time with a doctor and redraw them by hand using an etch-a-sketch. The origin also ends up on the wrong side and two databases of components need to be maintained if any are to be used on the reverse of the design

 

2) Create new versions of all the components I want to place on the reverse side with all the top copper pads in reverse position from the data sheet and wire them all up, supply all the attributes etc, add them to the schematic and then flip them, hopefully leaving them correctly corrected. This sucks for all the same reasons, plus its counter intuitive and prone to errors and mind boggling debugging fails.

 

3) Get wasted and throw the computer with the Eagle installation into the sea.

 

Although 3) looks like a pretty good option, there are knock on implications. I wanted to see if anyone else has any better ideas before I go down that route.

 

J

  • 0

    Jacob Skinner wrote:

    The mirroring of components, although it shows all the signs of switching the components to the under side of the PCB, does not do this. It leaves all the connections reversed and there is absolutely no satisfactory way of resolving this. (enter embarrassingly obvious solution here PLEASE)

     

    When you create a footprint, always draw/design it like if you want to place it on the topside of the board. Only when the schematic is finished and you started to lay-out the board, mirror the components that need to be placed on the bottomside of the board.

     

    Best Regards,

     

    Joop

  • 0 in reply to Joop14

    Thanks for the answer. I think one of us is missing something. Flipping the component does not work. It leaves all but the most simple and symmetric two pin devices wrongly orientated on the reverse side copper.

     

    Try it with an op amp or something and you should be able to reproduce the behavior. I took my printing the design out on paper and physically putting the device on the pads to be sure I wasn't going mad. The left and right sides of the device are swapped over.

     

    I am happy to take back my rant, but I fear it is the case that the mirroring (flipping) process does not work in the way required for anything over two pin devices.

     

    Great if you want to flip text or resistors!

  • 0 in reply to Former Member

    Lot's of people use Eagle to create double-sided boards with components on both sides, so something else must go wrong.

     

    After mirroring a component in the board-editor, can you already see that the pins are reversed? Or does the problem occur after exporting the layout to Gerber?

  • 0

    On 02/09/14 15:51, Jacob Skinner wrote:

    The mirroring of components, although it shows all the signs of

    switching the components to the under side of the PCB, does not do this.

    It leaves all the connections reversed and there is absolutely no

    satisfactory way of resolving this. (enter embarrassingly obvious

    solution here PLEASE)

     

    Sorry, but you're talking bollocks. I've been doing that with Eagle (v4)

    for years. If you take a component designed for top-side placement (all

    SMD pads on layer 1) and mirror it, then it will be both reflected and

    swapped to layer 16. That's all that's needed.

     

    So the question is, on what grounds are you so convinced it's not doing

    that?

     

  • 0

    To check what the back side looks like, display only the layers of the back

    side and then export the image.  (Try layers 17, 20, 22, 24, 26 and 52.)

    Open that saved image with your favorite editor (mine is GIMP) and flip the

    image horizontally and you'll see what the back side will look like...

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • 0

    As no one actually confirmed they were drawing their comments from v7 I

    downloaded v7.1 and reviewed its behaviour when mirroring packages to the

    bottom layer.

     

    It works as it has in the past mirroring the view.

    Have a look at the sample that comes with eagle Projects > tutorial >

    demo1.sch

    Generate a board from that schematic.

    Move IC2 into the board area.

    Observe where it's airwires connect back to the other components

    Mirror IC2 and confirm the airwires are still connected correctly.

     

    Remember the view of the bottom layer is down through the board

     

     

    HTH

    Warren

     

     

     

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • 0 in reply to autodeskguest

    CadSoft Guest wrote:

    Mirror IC2 and confirm the airwires are still connected correctly.

     

    In addition, in Options -> Set -> Misc activate the checkbox "Display padnames".

     

    Joop

  • 0

    All,

     

    Indeed, I was wrong. The integrity of the board is fine and as per the answers above there is no issue with reverse connection of the components. The issue was with understanding that the board is viewed from above and not from below in the case of the bottom copper). In the cold light of day this makes perfect sense, but after 15 hours staring at the design, it was not so clear.

     

    Many thanks for the replies and apologies to Eagle peeps for slandering their product!

     

    Best

     

    J

  • 0 in reply to Former Member

    Glad to see I'm not the only one with palm prints on my forehead from one

    of those "duh" moments (and it is amazing how many times something obvious

    gets overlooked - like the Martian spacecraft where one team was using

    imperial units and the other MKS - the numbers matched, but the units

    didn't and it crashed.  Talk about red faces !! )  Thanks for letting all

    know what the issue was.

     

    mikey

     

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

  • 0 in reply to autodeskguest

    Does my recollection serve me right that the Hubble had a US vs European dimensions error as well or something of that ilk? I seem to remember that it  ended up completely unfocused once deployed and there either ended up being a new mission to repair or something?

     

    ! silly humans