Swati,
To answer in the simplest terms...
Combination of lower resin content, typically 43% and thicker glass weave,
which when placed adjacent to thick copper, say 2 oz and above can lead to
poor encapsualtion and fill capabilities. Best to go for higher resin
content prepregs when bonding thicker coppers, or attempting to fill buried
via's.
Regards,
Colin McVean
Circuit Manufacture Ltd
Unit 9-12
Rowleys Green Lane
Longford
Coventry
CV6 6AG
Tel: 02476 666168
Fax: 02476 637089
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Parial Swati
Sent: 16 July 2004 04:41
To: [log in to unmask]
Subject: Re: [TN] 7628 prepreg?
Why is it that laminate voids are likely with such a combination ?
Regards,
Swati...
|---------+---------------------------->
| | Eddie Rocha |
| | <[log in to unmask]
| | M> |
| | Sent by: TechNet |
| | <[log in to unmask]>|
| | |
| | |
| | 07/15/2004 10:29 |
| | PM |
| | Please respond to|
| | "TechNet E-Mail |
| | Forum."; Please |
| | respond to Eddie |
| | Rocha |
| | |
|---------+---------------------------->
>---------------------------------------------------------------------------
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|
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| To: [log in to unmask]
|
| cc: (bcc: Parial Swati/NAN/ATS/IN)
|
| Subject: Re: [TN] 7628 prepreg?
|
>---------------------------------------------------------------------------
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7628 aginst 2 oz copper is not recommended. Possible lamination issues are
likely, i.e. lam voids.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brooks,Bill
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.?
Is the DK of 7628 different than other glass epoxy materials? I would like
to calculate the impedance of the traces on this board.
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?
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 Technology 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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