# Re: [SI-LIST] : Recommendations for High Density PCB to PCB Connection

From: sweir ([email protected])
Date: Thu Nov 04 1999 - 08:27:23 PST

Gentlemen,

Down here in the US a mil has always been 1/1000th of an inch. Is this a
difference between definitions in Canada and the US? For example, American
wire gauge tables are in circular square mils, which translate to 1E-6
square inch / square mil.

Regards,

Steve.

At 12:12 PM 11/4/99 -0500, you wrote:
>Mike Ventham wrote:
> >
> > Laurence,
> >
> > I still think you are having calculation problems.
> > Your answer was correct but
> >
> > 1 sq inch = 1000 mils * 1000 mils = 1000000 sq mil. NOT 10000 sq mil
> >(deleted )
>Ermm... No...
>1 inch = 100 mils 1 sq inch = 10000 sq mils
>1 meter = 1000 millimeter 1 sq meter = 1000000 sq millimeter.
>
>Contrary to SI prefixes, 1 mil isn't 1/1000 inch.
>It's 1/100 of an inch. That's one of the places I made a mistake.
>
>Using my trusty \$X000 computer as a simple calculator:
>
>gitm\$ units
>you have: inch
>you want: mil
> * 1.000000e+02
> / 1.000000e-02
>you have: m
>you want: mm
> * 1.000000e+03
> / 1.000000e-03
>you have: inch2
>you want: mil2
> * 1.000000e+04
> / 1.000000e-04
>you have: 25 mil2
>you want: mm2
> * 1.612900e+00
> / 6.200012e-01
>you have: 0.0025 in2
>you want: mm2
> * 1.612900e+00
> / 6.200012e-01
>
>Strange, but true.
>
>Anyone else care to share their mistakes with the rest of the world?
>
> > Laurence Michaels wrote:
> > >
> > ( deleted)
> > > Argh... I was asleep when I did that calculation. Time to check
> > > everything else I did yesterday :-)
> > >
> > > 0.2*0.5=0.1 square inch.
> > > 0.1/40=0.0025 square inches per connection
> > >
> > > (calculation error was probably here... 0.0025 square inches does
> > > NOT equal 2.5 square mils... that's what I get for using non-metric
> > > units, and only turning on half of my conversion algorithms.
> > > 1 sq in = 10000 sq mil 1 sq meter = 1000000 sq mm)
> > >
> > > 0.0025 square inches gives 1.6 sq mm per connection
> > > 25 square mils gives 1.6 sq mm per connection
> > >
> > > I'm not usually that stupid. (I hope)
> > >
> > > Thanks,
> > > --
> > > Laurence Michaels
> > >
> >
> > --
> > Regards
> >
> > Mike
> > ________________________________________________________________
> > | Mike Ventham - Vice-President Engineering, |
> > | Quantic EMC Inc Headquarters |
> > | Croft House, Chilcompton, 191 Lombard Ave, Winnipeg, |
> > | Somerset, UK, BA3 4JA Manitoba, Canada R3B 0X1 |
> > | Tel: 44 (0)1761 232191 Tel: (204) 942 4000 |
> > | Fax: 44 (0)1761 233549 Fax: (204) 957 1158 |
> > | Email: [email protected] http://www.quantic-emc.com |
>
>--
>Laurence Michaels
>Fiat GDC
>
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