In a message dated 11/17/2006 11:02:43 A.M. Eastern Standard Time, [log in to unmask] writes: So, what do they mean by "HDI"? Reading the document, in boils down to the thinner surface layers, equal to or less than .006" thick, used in conjunction with microvias, "these vias are the central characteristic of HDI". Valerie - In the late 90's IPC committees worked up three standards to 'bolt onto" the rigid board standards - one for HDI (microvia) materials, one for boards made principally with a multilayer core and microvias on the outer layers, and one for microvia board design. The standards pertain only to the added layers to the core controlled by the rigid board spec. Characteristic microvia layers then were 3-4 mils thick, non-reinforced material like RCC or photosensitive epoxy. So, thickness and "surface" were defining features. . I raised the question on TechNet about 2 months ago - was anybody using IPC 6106 for microvia boards, 4104 for microvia materials, and 2227 (from memory) for microvia design. The result was a resounding "no", from what I could tell. People specify and quality check to the interpreted rigid board documents, and extend that to microvia boards. Well, I have a committee plaque to show that I (and many others) worked on the standards. Denny Fritz MacDermid, Inc. --------------------------------------------------- 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 -----------------------------------------------------