Marcus, Most people use a minimum 2 ply construction. Some us this a minimum due to some misconceptions regarding UL requirements. Check your UL file and determine what the specified minimum dielectric thickness is for the pre-preg you intend to use. Unless a single ply would not meet the minimum thickness or a 2 ply minimum is stated in the file notes, I don't see a problem using a singe ply. The only restriction I can find regarding UL is in UL 796 specification section 12.8 under electrical insulation. It states that "the total buildup shall be equivalent to a base material layer with respect to its electrical relative thermal index." If a single ply meets that requirement, then it should be acceptable. I would not recommend a single ply for dielectrics below .004". This may create some electrical problems in the board. For this concern, I would check with designer of the part. I hope this helps. Ed Cosper Graphic Electronics Inc. Tulsa OK ---------- From: [log in to unmask][SMTP:[log in to unmask]] Sent: Monday, April 28, 1997 6:52 PM To: [log in to unmask] Subject: one prepreg? Hi everyone! I have a question to you about the minimum numbers of prepregs between two conductive layers. In our standards it is specified a minimum of two prepregs to secure good reliability. However, in order to reduce cost we would like to use only one. What kind of drawbacks can I expect? Is there a minimum prepreg thickness or epoxi content that can be used? Every comment is highly appriciated Thanks in advance, //Markus Markus Gauffin M.Sc. Printed Board Assembly Technology Ericsson Telecom AB e-post: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************