Via size when switching layer

On 27/09/2014 7:50 a.m., Blake Hodder wrote:

I am currently routing a project and have run into an issue. I have set

my drill hole to 6 mil and diameter to 10 mil as well as adjust the

restring to 10 mil 0% inner and outer. However, once the via is created

it creats as an inner and outer diameter of 26 mil. How do I stop this

from happening? This hinders my project as it prevents me from routing

the BGA chip.

 

Thanks,

Blake

 

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Would have helped if you posted a screen shot of your DRC > Restring

settings.

I'm guessing you have 10mil set for the minimum hence you get 10 + 6 +

10 = 26

If so make the minimum 0 along with 0%

Your drill hole of 6 mil and diameter of 10 mil will give a restring of

2mil which is small. Check with your board house what their minimums

are. Once you know that you can set the restring minimum to that and

have the DRC assist by creating restrings of that size, ensuring you

don't go below that figure

HTH Warren

Hi Warren,

Sorry, attached is picture of my DRC. I will try what you have stated now. How does the calculation occur that would turn my minimum into much larger?

Blake

On 27/09/2014 9:17 a.m., Blake Hodder wrote:

Hi Warren,

 

Sorry, attached is picture of my DRC. I will try what you have stated

now. How does the calculation occur that would turn my minimum into much

larger?

 

Its a two step deduction.

First the drill diameter is taken and the specified percentage of that

is used to reach an intermediate figure. With 0% that result is zero. so

the hole at this point has no surrounding copper.

Then, depending on whether you have specified a diameter for the via or

left the setting at 'auto' a result is reached.

With 'auto' set, the intermediate result is compared with the minimum

and maximum values set in the DRC. If smaller than minimum the value is

increased to be the minimum value. If larger than maximum the value is

reduced to be the value of the maximum seting.

With a diameter specified, the same happens as above for minimum but for

maximum the larger of the intermediate or maximum setting is used.

Remember the rest ring is a width not a diameter. it goes around the

hole so you get that width on both sides of the hole so the diameter of

the via is restring width + drill diameter + restring width.

It all in the manual and help and the image you posted

HTH

Warren

Hi Warren,

Interesting, it does not work the way I expected it to work. Please correct me if I am wrong. When you set the diameter then you are actually setting the rest ring width not the the diameter of the over all PAD. This does aid in setting the DRC. I do have my DFM settings from the manufacture and will be putting these in. But if I understand correctly I will have to modify the min values to handle that it is the ring width not the diameter.

Thanks,

Blake

On 29/09/2014 6:07 a.m., Blake Hodder wrote:

Hi Warren,

 

Interesting, it does not work the way I expected it to work. Please

correct me if I am wrong. When you set the diameter then you are

actually setting the rest ring width not the the diameter of the over

all PAD. This does aid in setting the DRC. I do have my DFM settings

from the manufacture and will be putting these in. But if I understand

correctly I will have to modify the min values to handle that it is the

ring width not the diameter.

 

Thanks,

Blake

 

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Many have a problem accepting how this works.

You are specifying your desired diameter but you don't get it

unconditionally.

Like I wrote earlier, if you don't specify a diameter and leave it as

Auto then the design rules will calculate a restring width and that

constrained by the max and min settings and combined with the drill size

will result in a pad diameter.

If you specify a diameter for your pad rather than leave it set to Auto,

you will get that diameter if it is larger than the calculated diameter.

If the calculation is larger you will get that diameter, not the one you

specified.

So for those that always want to specify their pad diameter, they should

ensure the calculated one is always going to be smaller than what they

specify, for all drill sizes on the board.

HTH

Warren