Having alternate boards flipped in a symmetrical layout means that
only one solder paste screen is required. Also, the same placement
control files and machine setups may be used, since the assembly panel
looks the same whichever side is up. In really high volume it's not
so much an issue, since a separate SMT line will be used to screen
and place the second side of the board anyway.

This technique needs to be used with some caution if the boards are
thin (e.g. PCMCIA) and there are fine pitch components on only one
side of the card. In this scenario, the assembler is likely to have
a preference for running the close-tolerance parts first up, when
the boards are pristine, flat and have high solderability (if the
board has a sacrificial solderability preservative like OSP or
white tin, the reflow heat of the first side will also affect the
yet-to-be-placed side, so the solderability of the second side won't
be quite as good as the first).

In short, talk to your assembler for their guidelines.

John Haddy

> -----Original Message-----
> From: Dennis Saputelli [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, 28 February 2002 12:16 PM
> To: Protel EDA Forum
> Subject: Re: [PEDA] Flipped on panel Paired Mechanical layers (ex
> Inversion ...)
> 
> 
> Ian Wilson wrote:
> > real reasons why correct inversion would be useful, another would be to
> > facilitate panelisation where alternate rows of boards are flipped - to
> > minimise machine setup.  Leaving this to a PCB maker can be a source of
> > error.  Doing it in Camtastic is my preferred option but some 
> companies I
> > work for like to have the panel in Protel for whatever reason.
> 
> i've seen those panels with some boards flipped and never understood, in
> fact i still don't
> can you pls explain what this offers?
> 
> thanks
> Dennis Saputelli
> 
> -- 
> __________________________________________________________________
> _________
> www.integratedcontrolsinc.com            Integrated Controls, Inc.    
>    tel: 415-647-0480                        2851 21st Street          
>       fax: 415-647-3003                        San Francisco, CA 94110
> 

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