> ----------
> From:         Phil Hersey[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Phil Hersey
> Sent:         Thursday, May 28, 1998 1:15 PM
> To:   [log in to unmask]
> Subject:      [TN] Metallized teflon film
> 
> First, you should realize that "Teflon" is a trade name that DuPont
> applies to several families of fluropolomer films.  The Teflon film
> used for flex circuits is FEP which is also used as a thermoplastic
> bonding film for PTFE based laminates.
> 
> Pure PTFE has excellent electrical properties.  The dielectric
> constant is 2.1 and the dissipation factor is 0.00045 over a wide
> frequency range.
> 
> The disadvantages of pure PTFE are it's poor dimensional stability and
> mechanical strength.  It is also very difficult to get copper to stick
> to it.
> 
> The material you inquired about is made by Polyflon Company makes a
> copper clad laminate by electroplating copper on pure PTFE.
> 
> A dielectic constant of 2.1 is not significantly lower than the 2.17
> to 2.20 available with the glass reinforced Type GY and GR laminates.
> The dissipation factor of 0.00045 is half that of the 0.0009 typical
> of the glass reinforced Type GY and GR laminates.  To get the lower
> dissipation factor of pure PTFE there is a significant cost associated
> with PCB fabrication, circuit card assembly, and assembly into the
> subsystem.  
> 
> Unless you absolutely must have the lower dielectric loss associated
> with pure PTFE, the other costs make it undesirable.
> 
> 
> I understand that prior to polyimide, vacuum metallized Teflon film
> was used for flex PCB's.  Seems to me this would be an excellent RF
> board material in place of  PTFE panel material (at 2 mil thickness a
> 50ohm trace would be 6 mil wide).  Has it disappeared totally and if
> so, why?
>    
>    
> Phil Hersey
> [log in to unmask] <mailto:[log in to unmask]> 
> (702) 884-5388x128 
> 

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