I believe the context of the message you refer to is considered 'a
joke.'




> -----Original Message-----
> From: JaMi Smith [mailto:[EMAIL PROTECTED]] 
> Sent: Friday, October 11, 2002 10:40 PM
> To: Protel EDA Forum
> Cc: JaMi Smith
> Subject: Re: [PEDA] flipping board
> 
> 
> I am not quite sure of what the context of this statement is, 
> since the thread took a rather twisting road to get to this 
> point, and I could not quite follow it, so I will just 
> comment on the statements below just as they stand, and hope 
> that it is not too far out of context.
> 
> According to IPC, the top side of the PCB is the is the 
> "Primary Side" of the PCB, which generally corresponds to 
> what we used to call the "Component Side", and the bottom 
> side of the PCB is the "Secondary Side" of the PCB, which 
> generally corresponds to what we used to call the "Circuit Side".
> 
> The "Primary Side" of the PCB us usually chosen or selected 
> by the Designer for some distinctive reason, such as being 
> the side with the most components, or most complex features, 
> etc., but this is not necessarily so, and there may be no 
> other reason beyond the Designers preference for this side 
> being chosen as the "Primary Side" of the board..
> 
> Physical Layers of the PCB are numbered beginning from the 
> "Primary Side" (top layer) being numbered as Layer 1, and 
> counting down sequentially thru the board to the "Secondary 
> Side" (bottom layer), and then continuing with Solder Mask 
> (Top, then Bottom), and then Silkscreen (or "overlay") (also 
> Top then Bottom), etc., etc..
> 
> The PCB also is usually demensionally defined as having three 
> mutually perpendicular datum planes. The first of these is 
> called the "Primary Datum", and is defined as being the 
> "Bottom Side" (or "Back Side"), of the PCB, or I suppose one 
> could say that it is the theoretical plane upon which the PCB 
> is said to rest.
> 
> This sometimes leads to confusion, because the "Top Side" of 
> the PCB is the "Primary Side" of the PCB, but the "Botton 
> Side" (or "Back Side") of the PCB is the "Primary Datum 
> Plane" of the PCB.
> 
> For further confusion on the subject, see IPC-2221 Generic 
> Standard on Printed Board Design, Sections 5.4.3 Datum 
> Features, and 11.2.1 Viewing (which will refer you to IPC-D-310).
> 
> JaMi
> 
> ----- Original Message -----
> From: "Michael Reagan (EDSI)" <[EMAIL PROTECTED]>
> To: "Protel EDA Forum" <[EMAIL PROTECTED]>
> Sent: Thursday, October 10, 2002 12:22 PM
> Subject: Re: [PEDA] flipping board
> 
> 
> > The only thing left now is Jun is now producing a design 
> counter to IPC
> > guidelines for documentation,   Primary side is on the bottom.
> >
> >
> >
> 

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