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| From: | |
| Reply To: | TechNet E-Mail Forum. |
| Date: | Tue, 13 Jul 2004 10:28:09 -0700 |
| Content-Type: | text/plain |
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See below:
I have tried to answer you specific questions to some extent.
The key here is to communicate with your Fabricator to see if they can fit your requirements with the least variations.
Talk to your Supplier!!! it is important and will make both your and their lives easier.
Call me if you want to discuss further.
Hope it helps,
FNK
Frank N Kimmey CID+
Principle PCB Designer
Powerwave Technologies
EDH 916-941-3159
FAX 916-941-3195
CEL 916-804-2491
-----Original Message-----
From: Brooks,Bill [mailto:[log in to unmask]]
Sent: Tuesday, July 13, 2004 9:46 AM
To: [log in to unmask]
Subject: Re: [TN] 7628 prepreg?
So in a stackup that requires a .031 core with 2 oz. Cu both sides and a
symmetrical build up of 2 layers of 7628 on both sides (4 total) and then
1.5 oz Cu finished outside... Would the objective then be to control the
spacing from the outer conductors to the inner ground plane at .014 in.?
FNK - That would have to be determined at design.
Does the PCB require an isolation or fit interface or clearance?
Is the DK of 7628 different than other glass epoxy materials? I would like
to calculate the impedance of the traces on this board.
FNK - The Dk of Epoxy (FR-4) is about 3.9 prior to adding glass.
The glass package is used to adjust the Dk to the appropriate value.
If used with controlled impedance requirements then the alternatives are to:
A.) Fix the acceptable glass packaging in the stackup on the Master Drawing.
B.) Allow Fabricator to modify and verify using TDR to meet Impedance requirement stated on Master Drawing.
Is there a materials sheet available on-line that describes the electrical
and physical characteristics of the prepreg material? And does it change
when laminated?
FNK - Materials are available from most Laminators web sites or contact your Fabricator for data.
This is an older board and I'm just trying to decipher the designer's
intent.
Thanks in advance...
Bill Brooks
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
http://pcbwizards.com
-----Original Message-----
From: Jeffrey Bush [mailto:[log in to unmask]]
Sent: Tuesday, July 13, 2004 4:10 AM
To: [log in to unmask]
Subject: Re: [TN] 7628 prepreg?
7628 glass has different yield thickness based on resin content and the
rheology. You can purchase 7628 in epoxy from a yield per ply thickness
of .0065" to where you are with yours. 7629 glass can give you up to
.009" in yield as this is some what heavier glass. I think the standard
has been a .007" per ply yield - this is fairly standard from laminate
suppliers.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technolog Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
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Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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