Auto-Routing Double Sided Board with non Plated Through Holes

Antzy,

A super simple way to deal with the through holes is to just feed a small wire through the 'via' holes and solder the wire top and bottom.  Instant plated through hole!

Gene

That works for vias but not for pads. For pads, the only way to connect top and bottom is by soldering on both sides and that isn't possible for most components (ICs, electrolytic capacitors, headers, etc).

What I'm asking is how to prevent autorouter from routing between layers using pads, and so, only route between layers using vias(which you then proceed to solder using the method you mentioned)

Antzy,

That is a good point. I do not have the auto-routing feature on my software (license) so I can not test any of the settings.  Even when I did have the correct license, I found that the auto-router did a very poor job, so I would never use it.

You might be able to manually place vias in the area where the component limits your access to both the top and bottom.

Just a thought.  Good luck finding a settings based solution to your problem.

Gene

Ah ok. I know the autorouter isn't too good but sometimes you're in a hurry and instead of spending an hour figuring out the best layout, you just want to let the autorouter dp your work and modify it to your requirement. Still think the ULP method I mentioned in the original question is the way forward. Thanks for your suggestions.

On 16/12/2017 7:18 a.m., Antzy Carmasaic wrote:

As a hobbyist, I find it much faster for prototyping make my own boards and recently got a CNC router to speed up prototyping. I usually route the boards myself but sometimes don't have enough time to do it by hand. The problem is that while the auto-router works fine for hand-made single sided boards, for double-sided boards, there is no way to turn off PTH for the pads. It will always assume the top and bottom of all pads to be connected by default and route accordingly. As everyone knows, making PTH at home is not feasible(time and money).

Is there any setting to tell the auto-router not to assume pads' top and bottom to be connected?

One way I see is by using a ULP that places pads' duplicate shapes on bRestrict for parts on bottom side and on tRestrict for parts on the top side. Is there any such ULP available?

 

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Hi

I don't remember hearing of such a ULP but one could be built.

Maybe a project over the Christmas break.

As with any coding, one needs to define the problem to be solved so lets

clarify yours.

(1) You wish to use the auto-router to route traces on the top and

bottom of the board. A double sided board.

(2) There are some PTH pads on the top or bottom layer that you wish to

have the auto router not connect to. For those PTH pads, the auto-router

can route on one layer but not the other.

(3) Not all pads on a side (layer) would be barred to the auto-router.

That would be a single sided board which can be handled already.

(4) You accept vias that the auto router places which you will use wire

to connect top and bottom layers

(5) There may be areas that vias should not be placed

(6) For a given device the restrict and keep-out requirements would be

the same for all other identical devices on the board

Let us know if that covers it

Warren

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On 16/12/2017 7:18 a.m., Antzy Carmasaic wrote:

As a hobbyist, I find it much faster for prototyping make my own boards and recently got a CNC router to speed up prototyping. I usually route the boards myself but sometimes don't have enough time to do it by hand. The problem is that while the auto-router works fine for hand-made single sided boards, for double-sided boards, there is no way to turn off PTH for the pads. It will always assume the top and bottom of all pads to be connected by default and route accordingly. As everyone knows, making PTH at home is not feasible(time and money).

Is there any setting to tell the auto-router not to assume pads' top and bottom to be connected?

One way I see is by using a ULP that places pads' duplicate shapes on bRestrict for parts on bottom side and on tRestrict for parts on the top side. Is there any such ULP available?

 

--

To view any images and attachments in this post, visit:

https://www.element14.com/community/message/232393

 

Hi

I don't remember hearing of such a ULP but one could be built.

Maybe a project over the Christmas break.

As with any coding, one needs to define the problem to be solved so lets

clarify yours.

(1) You wish to use the auto-router to route traces on the top and

bottom of the board. A double sided board.

(2) There are some PTH pads on the top or bottom layer that you wish to

have the auto router not connect to. For those PTH pads, the auto-router

can route on one layer but not the other.

(3) Not all pads on a side (layer) would be barred to the auto-router.

That would be a single sided board which can be handled already.

(4) You accept vias that the auto router places which you will use wire

to connect top and bottom layers

(5) There may be areas that vias should not be placed

(6) For a given device the restrict and keep-out requirements would be

the same for all other identical devices on the board

Let us know if that covers it

Warren

--

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(1) You wish to use the auto-router to route traces on the top and

bottom of the board. A double sided board.

 

(2) There are some PTH pads on the top or bottom layer that you wish to

have the auto router not connect to. For those PTH pads, the auto-router

can route on one layer but not the other.

That's correct.

(3) Not all pads on a side (layer) would be barred to the auto-router.

That would be a single sided board which can be handled already.

You nailed it. If it's easier to code, we can do away with the option of . Then the only way to

Do you mean that a few of the pads could be PTH(such as resistors which are easy to solder on both sides)? If so, that is a nice feature but to simplify, it can be assumed that there are no PTH pads and only way to connect top and bottom layers is through vias.

(4) You accept vias that the auto router places which you will use wire

to connect top and bottom layers

 

(5) There may be areas that vias should not be placed

Yes, the vias will be connected using wire soldered at both sides of the board. As you mentioned, there will be a few places where vias shouldn't be placed, such as bottom of ICs and buttons since soldered vias add a bit of a solder bump.

(6) For a given device the restrict and keep-out requirements would be

the same for all other identical devices on the board

Although that is true for 99% of cases, I can imagine a case where a component might be placed on both top and bottom layers. Then the restrict and keep-out layers will be opposite for the two.

I'm a programmer so I can certainly make it myself. But as I don't know anything about ULP programming, would need help and guidance to make it. Any good tutorials for learning ULP programming?

I'm guessing that this ULP can benefit a lot of folks designing, etching and drilling PCBs by themselves. Eagle's autorouter is a big help when starting out with single sided PCBs but when it comes to advancing to more complex double-sided PCBs, you have to route it by hand. Just having the option out there to use the auto-router will help a lot of people to switch easily from single-sided to double-sided boards.

This is what I got till now:

if (!board)
{
    dlgMessageBox("Start this ULP in a Board");
    exit (-1);
}


string result;
    
board(B)
{
    B.elements(E)
    {
        E.package.contacts(C)
        {
            if (C.pad)
            {
                string temp;
                sprintf(temp, "%s (%d) - %d, %d", C.name, C.pad.diameter[LAYER_BOTTOM], C.pad.x, C.pad.y);
                result += temp + "\n";
            }
        }
    }
    
    dlgMessageBox(result,"+OK");
    
    exit(0);
}

This does give me the correct pad names for all pads on board. But the diameter, x and y are way too large. For a board on a 0.05" grid, I'm getting diameter of 422656 and positions like 2844800 and 2032000. Can anyone help me get the correct pad positions and diameter?

I'm planning to draw circles in tRestrict and bRestrict layers at pad positions according to diameter of pad. Not perfect for square or oblong pads but should work as a base code.

If I'm going in the wrong direction, do guide me in any way to copy the exact pad shape to another layer. Thanks.

On 12/17/2017 02:26 PM, Antzy Carmasaic wrote:

I'm getting diameter of 422656 and positions like 2844800 and 2032000. Can anyone help me get the correct pad positions and diameter?

I think you need to add a member identifier to specify units on your

output. ie mils in mm or such. Look at some of the ULP's for pick and place.

Paul

Thanks Paul. It was actually because ULPs get all positions and dimensions in Eagle's internal units. They have to be converted using u2mic, u2mil, u2mm or u2inch. The funny thing is all their examples in their ULP manual just prints without conversion as well. Only by going through other ULPs could I find these functions, given only a small section in the ULP doc:

EAGLE stores all coordinate and size values as int values with a resolution of 1/10000mm (0.1µ). The above unit conversion functions can be used to convert these internal units to the desired measurement units.

Anyways, I got the script made. It works well and does almost everything I had initially planned. Here it is for those looking for a similar solution:

#usage "Allows using auto-router for double-sided boards without PTH\n"
       ""
       "Eagle assumes all pads as PTH which is not true for hand fabricated boards. "
       "This ULP copies pad shape in tRestrict for normal elements' pads, "
       "and in bRestrict for mirrored elements' pads. "
       "This prevents the auto-router from routing between top and bottom layers "
       "using the pads, and so forces it to use vias."
       "The vias can be physically connected to top and bottom using "
       "a wire soldered at both ends."
       "
"
       "Currently, only circular pad shapes are copied in restrict layers. "
       "Other shapes are assumed as the largest circle which can fit inside the shape. "
       "This works well for square, octangon and long pads."
       "
"
       "Author: antzy.pantzy@gmail.com"


// THIS PROGRAM IS PROVIDED AS IS AND WITHOUT WARRANTY OF ANY KIND, EXPRESSED OR IMPLIED


if (!board)
{
    dlgMessageBox("Start this ULP in a Board");
    exit (-1);
}


string result, s;


s += "GRID MM FINEST;\n";
s += "CHANGE WIDTH 0;\n";


board(B)
{
    B.elements(E)
    {   
        E.package.contacts(C)
        {
            if (C.pad)
            {
                string temp;


                if(!E.mirror)
                {
                    s += "CHANGE LAYER tRestrict;\n";
                    sprintf(temp, "CIRCLE (%.4f %.4f) (%.4f %.4f);\n", u2mm(C.pad.x), u2mm(C.pad.y), u2mm(C.pad.x) + (u2mm(C.pad.diameter[LAYER_TOP]) / 2.0), u2mm(C.pad.y));
                }
                else
                {
                    s += "CHANGE LAYER bRestrict;\n";
                    sprintf(temp, "CIRCLE (%.4f %.4f) (%.4f %.4f);\n", u2mm(C.pad.x), u2mm(C.pad.y), u2mm(C.pad.x) + (u2mm(C.pad.diameter[LAYER_BOTTOM]) / 2.0), u2mm(C.pad.y));
                }
                
                s += temp;
            }
        }
    }
    
    s += "GRID LAST;";
    
    exit(s);
}

Here's a screenshot of a quick test I did. 1 of the caps is mirrored, so will be placed on the bottom side. So traces should only go to it from the top side. The autorouter did exactly that. There are also 2 bRestrict areas separating caps, an 8-pin connector and a TO-220 component. The autorouter only took traces to them across the bRestrict using top layer and then assuming pads as disconnected on top layer, used vias to connect to them from the bottom layer. So yeah, works perfectly!!!