My solution on a recent BGA289 1mm design was to use a -7mil soldermask rule for the vias under the BGA and used it for both top and bottom. Production wants to probe on future revs so I will have to combine gerbers from separate rule applications. For this proto type I made the via size under the BGA different from the rest of the board so that I could easily select them. I converted them to pads and then defined a pad class 24dia 10 hole. My tracks were 5mil and spaces 5mil. This resulted with mask in the holes only by the amount of the misregistration of the soldermask. The PCB engineer at my board house suggests soldermask webs no narrower than 6mil. This prevents inconsistencies in appearance. I wish for a way to design rule check the soldermask for narrow webs and solder drains. My thought on the probe problem is that on BGA designs the probes can be done elsewhere on the board, there are vias galore. Dave Eloranta Locus Inc. Madison, WI
-----Original Message----- From: JaMi Smith [mailto:[EMAIL PROTECTED]] Sent: Wednesday, September 18, 2002 9:16 PM To: Protel EDA Forum Cc: JaMi Smith Subject: [PEDA] Selective tenting on one side only Hi All, Can I selectively tent only one side of a via, without having to tent the entire via and then manually go in there and put a little round pad on the solder mask layer on only one side of the hole, to prevent mask on that side. (My first mistake may be in assuming that a pad on the soldermask layer will actually prevent "mask" from being applied there.) I know that this sometimes yields less than perfect results, since the mask can simply run down the barrel of the hole, from the inmasked side to the masked side and gum up the masked side a bit, but I am willing to live with that. I have to use tenting on the top side of a board underneath a BGA, simply to prevent any solder from being wicked into the hole in the via, and causing a bad BGA "ball". But at the same time, this is a prototype board, and I have left all of the unused pads (pins) of the BGA still connected to a via, so that they can be accessed from the backside of the board if necessary, and it would be nice if everything was not tented there (at least intentionally and aside from what may run down the hole), so that people do not have to scrape off the soldermask with an xacto knife to get to the pad if they want that signal. JaMi * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
