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May 2004

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Subject:
From:
Colin McVean <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 19 May 2004 08:04:17 +0100
Content-Type:
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In general, the 7628 prepreg comes in either a low, standard or high resin
content. This same resin content variation can also be applied to other
glass styles, such as 2116, 1080 etc. It is very much dependant on what
volumes are required by the fabricator, which would justify the production
run by the laminator.

"B" stage is simply the resin state, which in prepreg format is the tack
dried resin system, capable of going through a rheology curve in the press,
which then melts, encapsulates and sets to a solid "C" stage irreversible
cured state.

Polyclad are one such supplier, who can offer 7628 with a 43% rc standard
and 48% high rc. I have found that it is usually the fabricator who
specifies a higher rc, when he has free reign on the build of the panel, and
this is normally for cost, where one ply of high rc 7628 replaces 2 plies of
2116 etc.

Only concern is where the fabricators have a fair amount of encapsulation to
achieve, either by via hole filling or high copper weights. When using high
rc products, it is also best to use vacuum lamination where possible.

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: Tom Bresnan [mailto:[log in to unmask]]
Sent: Wednesday, May 19, 2004 5:16 AM
To: [log in to unmask]
Subject: Re: [TN] FW: [DC] Core Constructions

Let me also add that lead-time may increase as well as cost. Be sure you
absolutely 'need' the material. Most fab houses won't have it on the shelf
(can't anticipate every customer's needs) and there may be minimum run costs
incurred as well. Work with your board vendor(s) to come up with a standard
material stackup to lessen the impacts.

-----Original Message-----
From: Jeffrey Bush [mailto:[log in to unmask]]
Sent: Tuesday, May 18, 2004 4:17 PM
To: [log in to unmask]
Subject: Re: [TN] FW: [DC] Core Constructions


You are able to get higher resin contents from most laminate suppliers.
They will have a part listing of standard glass styles with varying
resin contents.  Increasing the resin content in usually done to solve
an issue like poor wet-out of the glass, or voiding due to thicker
copper.  Generally thickness yield per ply will increase with the RC, as
will the cost.



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



-----Original Message-----
From: Brooks,Bill [mailto:[log in to unmask]]
Sent: Tuesday, May 18, 2004 3:50 PM
To: [log in to unmask]
Subject: [TN] FW: [DC] Core Constructions


Is there a materials expert out there that can answer Mike's question
below?

B-stage epoxy resin is somewhat of a mystery to many designers. Perhaps
someone can clarify the reference to "High Resin Content" as apposed to
? what other options are available and how they affect the construction
of the FR4 board. Please copy to the group too so we can all learn from
this.

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: Mike Valle [mailto:[log in to unmask]]
Sent: Tuesday, May 18, 2004 12:24 PM
To: [log in to unmask]
Subject: [DC] Core Constructions

Hi, I need some help trying to find some information on FR-4
construction and thickness. I've come across a 4-layer stackup on a
cross-section detail on one of our drawings and I can't seem to find it
in IPC-4121. Our b-stage construction calls out for 1 ply of b-stage HRC
(high resin content) 7628 .0068. Another detail on another drawing calls
out for 1 ply of b-stage HRC (high resin content) 7628 .008. What I've
been finding in IPC-4121 is that there is a FR-4 11 (7.087) 7628 40% RC
and a HFR-4 11 (7.087) 40% RC, which is a high tg. So, my question is -
is there such a thing as HRC - high resin content with varying
thicknesses?

Thanks,
Mike Valle
Project Engineer, PCB Design
Shure Inc.
(847)424-4616
[log in to unmask]

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