Joe, Having been a part of the committee that worked on 6016, I am sure the issue of remaining foil thickness ever came up. Quarter ounce, and thinner foils were not envisioned during the late 90's. Couple of processing points to remember - 1. Will you have enough copper cross section to carry the current you intend to put through the conductor? 2. The step after via drill and "laser ash removal" is metallization. That step, either electroless copper or direct metallization, will include a microetch step to remove copper, you must have enough copper left to allow that - usually less than 0.1 mil or 2.5 microns. Half ounce foil, as pointed out below is 17 microns or quarter ounce is 9 microns - should be enough to allow microetch. 3. You did mention "foil", so I assume you are not trying to build up from some additive or semi-additive copper feature from an embedded device like a capacitor or resistor. Denny Fritz MacDermid, Inc In a message dated 12/5/2007 7:30:10 A.M. Eastern Standard Time, [log in to unmask] writes: Joe; From a laser drilling standpoint, we prefer to use a minimum of half ounce copper for capture pad foil thickness. We have laser drilled a few parts with quarter ounce capture pad foil, but it is tricky to do so as the thin coppers buckle and damage easily from the localized heat of a laser beam. We have also produced blind vias on plated up sub assemblies that start with half ounce foil. We also routinely laser drill boards for power management devices that utilize one and two ounce copper foils. The thick foils are really hard to damage. Dave Simonik Laser Process Technician Sanmina SCI Corp. Owego NY Division -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US SSA) Sent: Tuesday, December 04, 2007 11:54 AM To: [log in to unmask] Subject: Blind Via Question For HDI vias, what minimum target pad foil thickness is allowed after hole preparation, prior to deposition and copper plating? IPC-6016 does not provide any requirements similar to those in IPC-6012 Table 3-7 for HDI applications. Joe Kane BAE Systems Johnson City, NY **************************************Check out AOL's list of 2007's hottest products. (http://money.aol.com/special/hot-products-2007?NCID=aoltop00030000000001) --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 -----------------------------------------------------