I also have to agree with John and Phil. There are several variables at work
here, pre-preg specifications just being one of them. The 3 mils for 1080
John refers to, I've seen specified as low as 2.4 mils depending on the
pre-preg manufacturer. Then there are other factors: Lamination pressures,
heat ramp-ups etc. If impedance values are the key, suggest getting dsign
input from your board supplier as best you can.
Bob Dube
-----Original Message-----
From: John Anselmo <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Monday, February 07, 2000 1:47 PM
Subject: Re: [TN] PREPREG
> I would agree with Phil. If you need a controlled dielectric,
> specify that on the print, not the type of prepreg to use.
> 1 ply 1080 has a nominal thickness of 3.0 mils (based on resin
> content and glass). So no, the supplier cannot add as much or little
> resin as they want. But, there can be up to a 10% variation in this
> thickness.
> Specifying prepreg severely limits the board manufacturer options,
> and increases the chances of the board not meeting your requirements.
>
>
> John Anselmo
> Hadco - Tech Center Austin
> 512-246-5616
>
>
>______________________________ Reply Separator
_________________________________
>Subject: Re: [TN] PREPREG
>Author: Phil Crepeau <[log in to unmask]> at smtplink-hadco
>Date: 2/7/00 10:06 AM
>
>
>hi,
>
>i would strongly recommend that, if at all possible, you leave these
details
>up to the board fabricator. and here's why: if the board doesn't meet your
>end product requirements you can blame the fabricator. if you specify the
>details, you will be responsible if the board doesn't meet your end product
>requirements.
>
>best of all, you should be involving the board fabricator at the initial
>stages of you design. and by the way, i am not involved in the board
>fabrication business.
>
>phil
>
>-----Original Message-----
>From: Brunker Ed [mailto:[log in to unmask]]
>Sent: Monday, February 07, 2000 8:37 AM
>To: [log in to unmask]
>Subject: [TN] PREPREG
>
>
>Is there anyone out there who can help me with understanding prepreg. If we
>specify a given prepreg, (1080) does that give us any control over board
>construction. I'm told that 1080 specifies a glass matt. So does this mean
>that for a given glass matt the resin added to it can be as little or as
>much as a supplier wants and the characteristics of that resin can be
>whatever? So sheets of prepreg can be any thickness and have any flow
>characteristics.
>Also for mobile phone usage what are people using in FR4 to achieve
>approriate dielectric characteristics? Are there a range of prepregs being
>used or just 1080?
>
>Regards
>Edward Brunker
>
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