Jack: Use a 4.1 to 4.35 standoff. seems simple enough to me :) "Jack C. Olson" <[log in to unmask]> Sent by: DesignerCouncil <[log in to unmask]> 03/21/2005 03:30 PM Please respond to "(Designers Council Forum)" <[log in to unmask]>; Please respond to "Jack C. Olson" <[log in to unmask]> To To [log in to unmask] cc Subject Re: [DC] Floating SMT components? Caterpillar: Confidential Green Retain Until: 04/20/2005 Retention Category: G90 - General Matters/Administration Well. just to clarify since several people asked... We have a mated pair of board to board connectors that are about 4mm once the two boards are snapped together. We noticed when looking at several boards that the plastic part of the connector is not always flush to the board, like it is slightly riding on the solder paste We also have standoffs that are 4mm, but I was asked if we should design our own 4.1mm standoffs to keep the pressure/warpage down. So the board thickness tolerance is NOT an issue, we are concerned with the space BETWEEN the boards. So that just got me curious, how high do components sit above the surface of a board? (with no mechanical retaining feature) Most people answered 2-2.5mils Thanks for the feedback, Jack (the "not an assembly guy" guy) [log in to unmask] com 03/18/2005 11:43 To AM To "(Designers Council Forum)" <[log in to unmask]> "Jack C. Olson" <[log in to unmask]> cc Subject Re: [DC] Floating SMT components? Caterpillar: Confidential Green Retain Until: 04/17/2005 Retention Category: G90 - General Matters/Administration Hi Jack- Good question; no answer from me, but... Just out of curiosity, what do you see as being "the surface of the board"? If you're worried about a mil or two of solder, then the difference between bare laminate vs. base conductor+ plating+finish vs. either/both with soldermask added becomes significant... I only ask because that comes up from time to time here. My answer is: "It depends... why do you ask?" Since the board thickness usually has a 10% tolerance, if it's 1.5MM or thicker PCB, I'd just leave solder under the connector out of the stackup, but I'm lazy that way. And I guess the connector config. would have a lot to do with it. Does it have a mechanical retaining feature? If so, I say disregard the solder. It's gonna be where it's gonna be within the tol. built into the snap, lock, or whatnot. -Chris "Jack C. Olson" <[log in to unmask]> To: [log in to unmask] Sent by: DesignerCouncil cc: <[log in to unmask]> Subject: [DC] Floating SMT components? 03/18/2005 12:08 PM I have been asked a question that I've never read anything about before, so I'm hoping someone will know this... We have a mechanical engineer who is trying to predict the distance between boards after soldering SMT board-to-board connectors. We know the connector mating height, but the question is: "If the connector is sitting in solder-paste, how high will it stay above the surface of the board?" Common sense tells me the connector will not be flush to the surface, there will be some solder under there, and I think we are using 6mil paste screens. Has anyone had to document something like this before? Jack --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------