If you buy, say, 2.4 mm laminate with 70 or 105 µm copper, do you think
it is made with high-resin content prepregs? No way, it is made with
7628 or even lower resin content styles. A high resin style would cause
slippage in the press.
Brian
Colin McVean wrote:
> 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 |
> | | |
> |---------+---------------------------->
>
>>---------------------------------------------------------------------------
>
> -----------------------------------|
> |
> |
> | To: [log in to unmask]
> |
> | cc: (bcc: Parial Swati/NAN/ATS/IN)
> |
> | Subject: Re: [TN] 7628 prepreg?
> |
>
>
>>---------------------------------------------------------------------------
>
> -----------------------------------|
>
>
>
>
> 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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