I have a very cool ruler, made of FR4. One side is inches and tenths. The other side is centimeters and halves, quarters and eighths. Guy Ramsey Senior Lab Technician / Instructor E-Mail: [log in to unmask] <mailto:[log in to unmask]> Ph: (610) 362-1200 x107 Fax: (610) 362-1290 -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Eric Christison Sent: Monday, July 23, 2001 11:44 AM To: [log in to unmask] Subject: Re: [TN] Component Mass / Pad Geometries Nice to see some consistent units - g/in^2 here. Haven't seen this mix since I came across a stress quoted in N/in^2 ;-)..... > Hi Steve! > > The formula that has been floating around for a while is that you get > 30-grams of surface tension for every square inch of pad surface.... > > -Steve Gregory- > > > > Question? > > > > There is a formula somewhere which I can use to calculate the maximum > > allowable mass of a component in relation to the pad lands. Basically > I > > want to make sure our designers do not put components on the underside > > of the PCB which are going to fall off during doublesided reflow. > > > > I would like to point out that this is a design for manufacturability > > question, not an attack on the tentative grasp on reality some card > > designers have. > > > > Steve. > > > > > Eric Christison ---------------------------------------------------------------------------- ----- 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 the following message: SET Technet NOMAIL 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 the following message: SET Technet NOMAIL 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------