PCB design in Mils (Inch) or MM's?

[neuralc]

HI,

I normaly use mm to place the components, and make my measurments (PCB size, buttons place, leds place, ...). To build new footprints place tracks , ..., normaly I use mils, but I think that is a question of train...

NeuralC

 

[gometric]

The selection of the units is also a kind of selection what accuracy you need.
selecting MM,MILS,UM (micrometer) and the appropriate amount of decimals will give you either a smooth working or all the time a lot of rounding errors which can impact your work a lot.

for instance working in Allegro with MILS and 4 decimals will all the time you do an autovoid of shapes give you nice results, Allegro is converting every X/Y location into an internal database value (independent of MIL,MM,UM) wich cause very often round off errors...

Tobias

the same thing does PADS!!

 

[gometric]

mils is so standart because of all components sizes and pins are related mils.

Not the new BGA's, QFN's, lok at IPC, everything is referenced to mm.

 

[gometric]

I use MM for placement of critical items, such as board outline, mounting holes etc so as not to get wrong values as the mechanical drawings are all in mm now.

I also use MM when creating a footprint (unless the spec is only in thou).

Then I use thou when placing and routing.

As for the industry moving over to MM, oh yeah, like I'll believe that when it actually happens. Just because industry stds want us to does not mean that we will.

LONG LIVE THE INCH!!!

I know what you feel and I understand it. But don't worry if me coming from a metric way of life I managed to start working and counting on 8's, 16's or 32's... of and Inch you will do much better than me ehrn moving to the metric world: you only count in 10's, isn't that great????

 

[wdavid]

I use mil as the unit in PCB design, because the PCB manufacture factory mostly use mil.

 

[knight]

Mill's been so common nowadays, although mm is what we should be using in this country, but everybody still accept the english way of measurments. Besides it is what you choose to use, both works, and our tools seem to have no problems handling these units.

 

[fastelec]

I use both mils and mm.mils when i draw pads and mm when i`m making pcb.Using mils or mm depends only of the manifacturer`s equipment, because most of the firms i worked with want the drill file to be in mils.

 

[jodokus]

It really does not matter wether you design in mils,mm or feet. The only thing that matters is that the measurement units are clearly for anyone who has to use them and obey any tolerance restrictions. All important eda and cam packages can convert between the regular measurement units. So design in whatever you like and at the end convert if that pleases your customer.

 

[Sukohi_Berkut]

hi
I use mm while creating component foot-prints which are

0.5 mm, 0.65 mm, 1mm apart

and use mils while routing them

the disdavantage with the combination of both units is that you will have conversation error

ex, mil has an accuracy of 5:2 where as mm can go to 2:4

allegro now won't allow you to change the accuracy more than 2 digits for mils. (you can override it by setting the param drawing_4mils in the user preference)

the point is if you change the units now and then your data will have inconistant measurements along the board.

one good practice is use mm for component creation and mil for board layout
regards

 

[stronghu]

both are ok!

i use MM while making foot-prints ,
MIL while layout

 

[Ash488]

For design ¨mm¨ & for manufacturing ¨mils¨.

Regards.

 

[flaxa]

I use mils.
Some manufacturers use milimeters for component dimensions
in their datasheets. In such cases I convert mms to mils
(by hand/head/calculator 8), then use mils dimensions for new
components in libraries.
Oh I almost forgot that I talk about OrC*d.

 

[manjeet_hp]

hi
whatever is happenig is a transition period from mils to mm but still majority of people (including me ) do board layout in mils.
mani

 

[simce]

My experience tells me that most of chips are designed in mil's, and it will be easier to you to make you own footprints in mil's. Also transition from mil to mm is not hard to acheive, this way it is not that trivial what measures you'll use.

 

[nikhil]

hi

u can use any of the unit according to ur convenience but insure desired unit recommended by ur manufacturer at the time of final gerber generation .
mean while during pcb design phase for shake of convenience u can use mils .
while decal making select unit according to unit mentioned in datasheets .

be flexible

nikhil

 

[xvibe]

I really don't understand why people are using INCHEs and MILs.
Isn't the SI units km, m, mm, um? So, why do you use inches? I know that US is driving the marketing but for what are the standards?
Is a 3/8 of an inches better to undersant than 9.5mm? I think not...
The problem of the programs converting mm to mils is because they are made in the US. Maybe the European ones convert internally mils to mm!
And why do you guys say .90nm stepping or 13um and not X mils?
I think that every should use the same standard.
And what is 1 inche? Is this more naturally than mm? The lenght of inche of who, my friend?

 

[gorkin]

I used mils, its easy for draw components footprints!

I am talk from Brazil and I think most pcb designers here use mils...
Gorkin.

 

[amjad]

I have used both mil and mm

 

[kejitongxin]

in my country we use mm

 

[cktay]

For PCB placement and trace routing, I use mil because pcb manufacturer normal refer to this standard.

For component or footprint making, I use mm or inch because most of the datasheet use these standard measurement in their design.

For PCB thickness or stack-up design, normal all used Ounce where it is the standard pcb manufacturer refer to.