kicad-developers team mailing list archive

[Jean-Paul Louis <louijp@xxxxxxxxx>]

Today, the smallest SMD chip is the 01005 which is 0.010”x0.005”, which in metric units is about 0.25mmx0.125mm(0.13mm). using a grid of 0.05mm will drive the courtyard to be odd shaped in relation to the part. I would suggest to be able to lower the grid resolution to 0.01mm to deal with these minute sized parts.

Just my $0.02,
Jean-Paul
N1JPL

> On Feb 16, 2016, at 3:26 AM, jp charras <jp.charras@xxxxxxxxxx> wrote:
> 
> Le 16/02/2016 09:08, Mikael Arguedas a écrit :
>> Hi,
>> 
>> 
>> 
>> 
>> On Mon, Feb 15, 2016 at 11:49 PM, jp charras <jp.charras@xxxxxxxxxx> wrote:
>> 
>>> Le 16/02/2016 07:44, Mikael Arguedas a écrit :
>>>> Hi Miguel,
>>>> 
>>>> Thanks for the clarification. I can now appreciate the difference. In
>>> this
>>>> case it's indeed more useful to have a minimum size that won't be 0.
>>>> 
>>>> Actually I thought these were 1nm steps. My intent was to have every
>>>> courtyard size to be rounded to 0.1mm and thus land on a 0.05mm grid as
>>>> specified in the KLC.
>>>> Anyway I tested it on a couple of footprints and it seems to be giving
>>> the
>>>> expected result.
>>>> 
>>>> Thanks for reviewing and for the explanation!
>>> 
>>> In fact the patch needs a bit of enhancement:
>>> - It uses values given in internal units. this is not a good practice
>>> if you want to use a value of 0.5 mm, use 0.5 mm. (like for all uthers
>>> values)
>>> 
>> - I did use the values already used by the scripts themselves (variables
>> sizex and sizy are expressed in 1nm steps). All this patch does is rounding
>> the values already used by the scripts to draw the recangle. I didnt want
>> to change the internals of the script given that they all use the same
>> format.
>> What I can do:
>>  - Use pcbnew.FromMM() method to make clearer where these numbers come
>> from.
>>  - Implement this ceiling function in the parent class and just call it in
>> all the scripts using it.
> 
> Yes, this is a good idea.
> 
>> 
>>> The meaning of values just given as integer is always not easy to
>>> understand.
>>> - Because the rounding is subject to change, and used 6 times, only one
>>> method called 6 times is more easy to change, and more easy to
>>> understand for the reader.
>>> - the KLC say 0.05 mm rounding. Why to use 0.1 mm? Leave 0.05 rounding
>>> level.
>>> 
>> All the scripts seem to give the size of a rectangle to draw. This
>> rectangle is centered on the origin. So if I use 0.05 for rounding the
>> courtyards line may endup on a 0.025 grid. That is the reason I used 0.1mm.
> 
> In fact, AFAIK, some scripts use the size of a rectangle, and some
> others the distance (coordinate) from X or Y axis.
> 
> Rectangles are used for SMD ICs, but connectors do not use always
> rectangles to build the courtyard.
> 
> If you are implementing the ceiling function in a parent class, use 0.05
> mm, because it will be not necessary used for sizes, but also for
> distances, and round the half size if needed.
> 
>> 
>>> 
>>> Thanks for your interest at Kicad.
>>> 
>> You're welcome I love this project. I'm using it everyday so I'm happy to
>> contribute back!
>> 
> 
> -- 
> Jean-Pierre CHARRAS
> 
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