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Question regarding layer preferences

Former Member

Hi,

As a newcomer to Eagle I am trying to create a two layer pcb with mainly

through hole components but with a couple of smd ic's on the top.

When I use the Autorouter it chooses to put the majority of tracks on the

top even for the through hole components.

Is there a way I can get Eagle to give preference to the bottom layer and

use only the top when necessary?

I understand that if I want to put the smd ic's on the bottom layer I can

use the Mirror command. I tried this and it works.

However, I would like to mount a pin header to connect from the bottom of

the board with the pads on the top. The mirror command does not seem to

work for this. I there a way around this? I don't have the facility of

through hole plating.

Regards

Don m5aky

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

 

Parents

  • Thanks for the reply Jorge.

    OK about the mirroring of through hole devices.

    How do I adjust the layer cost factors?

    Don

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

     

  • in reply to Former Member

    On 3/2/2015 2:40 PM, Don wrote:

    Thanks for the reply Jorge.

    OK about the mirroring of through hole devices.

    How do I adjust the layer cost factors?

    Don

     

    Hi Don,

     

    In the new autorouter, when you get to the variants dialog(the one that

    has the Start job button) you'll see a button on the bottom left that

    looks like >>. Click that button, this will show you all of the cost

    factors for the various variants.

     

    Each tab represents a pass of the autorouter, so on each one you would

    adjust the layer cost factors. The higher the cost the less likely EAGLE

    is to use the layer.

     

    hth,

    Jorge Garcia

     

Reply
  • in reply to Former Member

    On 3/2/2015 2:40 PM, Don wrote:

    Thanks for the reply Jorge.

    OK about the mirroring of through hole devices.

    How do I adjust the layer cost factors?

    Don

     

    Hi Don,

     

    In the new autorouter, when you get to the variants dialog(the one that

    has the Start job button) you'll see a button on the bottom left that

    looks like >>. Click that button, this will show you all of the cost

    factors for the various variants.

     

    Each tab represents a pass of the autorouter, so on each one you would

    adjust the layer cost factors. The higher the cost the less likely EAGLE

    is to use the layer.

     

    hth,

    Jorge Garcia

     

Children
  • in reply to autodeskguest

    Jorge Garcia wrote on Mon, 02 March 2015 21:47

    In the new autorouter, when you get to the variants dialog(the one that

     

    has the Start job button) you'll see a button on the bottom left that

    looks like >>. Click that button, this will show you all of the cost

    factors for the various variants.

     

    Each tab represents a pass of the autorouter, so on each one you would

     

    adjust the layer cost factors. The higher the cost the less likely

    EAGLE

    is to use the layer.

     

    hth,

    Jorge Garcia

     

     

    Can I join in on this thread, please?

     

    What are the ranges for these cost factors? I have tried several

    combinations such as: 0/50, 0/100, 0/1,000.

    None of which seem to make any difference? Approaching from an alternative

    angle, can you suggest a pair of weightings that will ensure that all

    tracks are on the bottom. Except, of course, those that can't complete

    unless routed across the top.

     

    My reason for such a one-side view (sorry for the pun) is to assist in any

    remedial work that may be needed. It is a lot easer to make track changes

    on the bottom rather than the top.

     

    Best regards, Martin

    --

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

     

  • in reply to mprowe@peritonlane.net

    Can I join in on this thread, please?

    Of course you can Martin,

     

    What are the ranges for these cost factors? I have tried several

    combinations such as: 0/50, 0/100, 0/1,000.

    Chp 7 of the EAGEL manual covers each of the cost factors in detail and

    provides suitable ranges of values.

    None of which seem to make any difference? Approaching from an alternative

    angle, can you suggest a pair of weightings that will ensure that all

    tracks are on the bottom.

    That's the thing with autorouter, you can skew the cost factors to

    really favor routing on the bottom. (Set the bottom cost factor to 0 and

    set the Top cost factor to 99). But it won't guarantee that you won't

    have tracks on the top. That's the key takeaway with the autorouter

    there is no hard guarantee in general. If you really want to avoid the

    top layer at all costs then you can set it's direction to N/A in the

    general tab of the autorouter.

     

    EAGLE will give a warning that the top layer is used but not enable,

    just ok it. If you're just doing two layers this might be OK but on

    multi-layer boards you risk via collisions because the top layer isn't

    taken into account.

     

    hth,

    Jorge Garcia