I have a very cool ruler, made of FR4. One side is inches and tenths. The
other side is centimeters and halves, quarters and eighths.

Guy Ramsey
Senior Lab Technician / Instructor


E-Mail: [log in to unmask] <mailto:[log in to unmask]>
Ph: (610) 362-1200 x107
Fax: (610) 362-1290



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Eric Christison
Sent: Monday, July 23, 2001 11:44 AM
To: [log in to unmask]
Subject: Re: [TN] Component Mass / Pad Geometries


Nice to see some consistent units - g/in^2 here. Haven't seen this mix since
I came across a stress quoted in N/in^2 ;-).....





> Hi Steve!
>
> The formula that has been floating around for a while is that you get
> 30-grams of surface tension for every square inch of pad surface....
>
> -Steve Gregory-
>
>
> > Question?
> >
> > There is a formula somewhere which I can use to calculate the maximum
> > allowable mass of a component in relation to the pad lands. Basically
>  I
> > want to make sure our designers do not put components on the underside
> > of the PCB which are going to fall off during doublesided reflow.
> >
> > I would like to point out that this is a design for manufacturability
> > question, not an attack on the tentative grasp on reality some card
> > designers have.
> >
> > Steve.
> >
>
>
>


Eric Christison

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