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

From: Laurence Michaels ([email protected])
Date: Thu Nov 04 1999 - 09:12:03 PST

Mike Ventham wrote:
>
> Laurence,
>
> I still think you are having calculation problems.
>
> 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 |
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```--
Laurence Michaels
Fiat GDC
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