(More wood to the bonfire...) In addition to the other comments, to expand on what Moonmeister said, possible that your vendor is using foil construction now versus core construction. For 4-layer boards, foil construction starts with a core board already processed and adds laminate/prepreg to the outside with copper foil added last, then processed. Core construction uses 2 cores (Layers 1 & 2, then Layers 3 & 4) with laminate/prepreg in between. Does the master (or drill) drawing define board construction, or is it left to the vendor's discretion? Roger M. Stoops, CID [log in to unmask] TRIMBLE NAVIGATION LLC -----Original Message----- From: Genny Gibbard [mailto:[log in to unmask]] Sent: Tuesday, February 26, 2002 11:36 AM To: [log in to unmask] Subject: Re: [TN] The board looks funny... That is kind of what I was wondering, Moonman. Does it appear that our board manufacturers usually etch the copper on the back of the top sheet of FR4, and instead this manufacturer etched it on the top of the inner sheet of FR4, so we are seeing the other side of the copper? As far as I figure, the layer spacing would be effectively the same, so can anyone see any problems with one type of construction over the other? The deeper layer is dark like the close layer usually appears, so to me it looks like the same processes were used but both inner layers were etched on the inner sheet of FR4, versus etching them on the inside of the outer two sheets. Or, considering the other answer I received regarding no oxide coating, or double treatment: are these bad things? Thanks. -----Original Message----- From: Earl Moon [mailto:[log in to unmask]] Sent: February 26, 2002 10:14 AM To: [log in to unmask]; [log in to unmask] Subject: Re: The board looks funny... Just depends on which layer you look at - one on the back of the top layer or one more down MoonMan ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------