Auto-Router and Via Diameter

Am 24.12.2013 14:36, schrieb James Morrison:

How do I get the auto router to use a specified diameter for the vias?  I

hate using the DRC to specify the annular ring of holes since it then means

that large holes and small vias all have the same minimum annular

ring--which is wrong.

 

I want my vias to have a 0.020" diameter but the auto-router keeps setting

them to auto.

 

James.

 

James,

the Autorouter always takes the "auto diameter" option for vias. It's

the resulting diameter from minimum drill and restring from the Design

Rules. There is no other option.

--

Mit freundlichen Gruessen / Best regards

Richard Hammerl

  CadSoft Support -- hotline@cadsoft.de

  FAQ: http://www.cadsoft.de/training/faq/

On 2/01/2014 10:17 p.m., Richard Hammerl wrote:

Am 24.12.2013 14:36, schrieb James Morrison:

How do I get the auto router to use a specified diameter for the vias?  I

hate using the DRC to specify the annular ring of holes since it then

means

that large holes and small vias all have the same minimum annular

ring--which is wrong.

 

I want my vias to have a 0.020" diameter but the auto-router keeps

setting

them to auto.

 

James.

 

 

James,

 

the Autorouter always takes the "auto diameter" option for vias. It's

the resulting diameter from minimum drill and restring from the Design

Rules. There is no other option.

 

 

Hi

Refining Richard's response:

If you have a net class set with drill sizes greater than the minimum

drill size set in the DRC then the auto-router will use the drill size

of the net class and calculate the restring size from it.

Warren

On 25/12/2013 2:36 a.m., James Morrison wrote:

How do I get the auto router to use a specified diameter for the vias?  I

hate using the DRC to specify the annular ring of holes since it then means

that large holes and small vias all have the same minimum annular

ring--which is wrong.

 

I want my vias to have a 0.020" diameter but the auto-router keeps setting

them to auto.

 

James.

 

Yes, another legacy feature that needs updating.

I would approach it this way and hope that the real world needs don't

conspire to change the approach.

For any design the via hole is likely to be the smallest drill. So I set

this in the DRC minimum drill setting. Any drill hole found smaller than

that will throw a DRC error.

Let's say it's going to be 10 mil

I also decide that the smallest restring I require is with this smallest

drill and that is quite likely. All bodes well if this is the case

Next, any active net class (one that is used in the design)  should have

a minimum drill size that is equal to  this minimum size. 10 mil again.

No hole in any net should be less than the minimum for the design.

Larger minimum drills in a net class cause us problems.

Power nets can be different. Per hole, larger holes have less

resistance. trouble is we name it a power net and it remains one even

when it is dripping uAmps into an IC. It doesn't require larger via

holes at this point.

Next, set up the DRC for VIAs

(1)  Based on the minimum drill diameter make the rest ring minimum

achieve the desired via diameter. In our case it would be 5mil.

5mil (restring) + 10mil(our via drill)  + 5 mil(restring) = 20mil

(desired diameter)

(2) Set the percentage. There is some balancing to achieve here.

     (i) The maximum, for our example is 50% otherwise we will exceed 20 mil

     (ii) The minimum is the largest restring you would like for your

largest hole (TPH) and that cannot exceed 50%

(3) Set the maximum size for the restring in the DRC such that you limit

the size of restring on your largest hole that requires plating.

It's far from ideal but I hope people find some value it

Warren