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 ________________________________________________ This email is confidential and intended solely for the use of the individual to whom it is addressed. Any views or opinions presented are solely those of the author and do not necessarily represent those of the Company. If you are not the intended recipient, be advised that you have received this email in error and that any use, dissemination, forwarding, printing, or copying of this email is strictly prohibited. If you have received this email in error please notify the Company by telephone on +44 (0)24 7666 6168 or reply by email to the sender and delete the email. ________________________________________________ Whilst every effort has been made to ensure that there are no viruses embedded in this email, we highly recommend that you virus scan any attached files using your own anti- virus software. -----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. 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