Positive etchback was a general requirement for Aerospace and in developing the IPC standard performance sheets for this a concession was made. However, the commercial standard for post connection did allow negative etchback and this was determined not allowable for flight systems and the no-negative etchback was added in this sheet. This is a good rule for any design in my opinion for hi-rel products. Same applies for the vias where a plugged via may have issues that affect the reliability of the barrel - expansion, chemistry entrapment, and I also think the ability to inspect the holes. This in counter-intuitive as a via that is filled with the correct materials/process will improve the reliability of the via. Jeffrey Bush Director, Quality Assurance and Technical Support VERMONT CIRCUITS INCORPORATED 76 Technology Drive - POB 1890 Brattleboro, Vermont 05302 Voice: 802.257.4571.21 Fax: 802.257.0011 http://www.vtcircuits.com -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of schaefer, dave Sent: Friday, August 26, 2005 11:30 AM To: [log in to unmask] Subject: [TN] IPC-6012B Class 3A Questions I have a few questions regarding the requirements of IPC-6012B classification "3A" (ref. "IPC-6012B Performance Specification Sheet for Space and Military Avionics"): - Why does the Performance Sheet define NEGATIVE ETCHBACK (3.6.2.8) as being unacceptable? - The description of "Through Via Plugging" requires clarification - is the Performance Sheet indicating that Vias and Through Holes cannot be plugged? If so, why? Thanks, Dave Schaefer Bristol Aerospace (204)775-8331 ext 3186 --------------------------------------------------------------------- "Confidentiality Disclaimer: This message and the documents attached is intended for the addressee(s) only and may contain privileged, private or confidential information. Unauthorized review, disclosure, dissemination, distribution, duplication or other use of this information is strictly prohibited. If you have received this message in error, please notify the sender immediately via telephone or return email. Please, then delete the original email and all copies from your system, servers, backups and archives". --------------------------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------