Hi Susan, Aside from long-term reliability, the issue is how well your board suppliers can produce 4 mil lines and spaces. If your suppliers can not produce these features with high yields there may be delays in the delivery of the boards. Furthermore, there are questions on how well your board suppliers maintain line width control. For example, when you request 4 mil lines with specification limits of ± 10%, a supplier without the necessary capability may deliver boards with lines that average 3.2 mils in width, with a range of 2.2 mils to 4.3 mils, substantially missing the target. Line width control is process dependent and some suppliers have their processes controlled better than others. We offer a testing and analysis service that provides process capability data on PCB manufacturing capabilities. If you need help in understanding you board suppliers capabilities please feel free to contact me. Tim Estes Conductor Analysis Technologies Inc. Phone: 505-294-6936 Fax: 505-294-6596 Email: [log in to unmask] Web: http://biz.swcp.com/cat ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################