Hi Mike,
Most of the laminate manufacturers have what is called as Standard, low
resin & high resin prepregs or B-Stage, they could also formulate to a
particular resin content type if you are a strategic customer & buy the
minimum prepreg quantity that comes in a roll which could be a few thousand
sheets.
The basic reason why anyone would use the different resin content prepregs
would be to meet the dielectric thickness, impedance & overall thickness
requirements per the customers spec. In certain designs where the copper
thickness on the surface is thick or unevenly distributed you may need a
resin rich prepreg to fill the spaces otherwise you may end up with laminate
voids. Some customers may spec. this in their drawing based on design
considerations or past experiences with concerns noticed with using standard
material.
There is also another factor one would like to consider is the type of FR-4
material that is being used with the different resin contents, whether ii is
a low, medium or high flow prepreg as this would also have an effect on the
final dielectric thickness one is targeting to achieve.
Hope this helps.
Krishnan
SANMINA-SCI
Quality Assurance / NPI Manager
E-mail: [log in to unmask]
Phone (Off): 082-363000 Ext. 1602
Mobile: 012-8888-379
-----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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