Date : 15/11/96 14:03 Msg From: TECHNET IMO pad width doesn't play a role in stress on the solder joint.Even if your pad width is .35mm for a .5mm pitch device you are going to print only .25mm paste on the pad otherwise you might have solder bridges.Pad length certainly palys a very important role in that.If you refer to IPC SM 782 , you'll find that this determines the Toe and Heel fillet heights and certainly the solder joint strength.You need to determine optimum pad geometries according to the component geometry. Atul Rastogi Altos India Ltd >>>>>>>>>>>>>>> Posted: Wed, Nov 13, 1996 8:18 PM Msg: FJJG-2574-6716/20 From: ("RFC-822": <TechNet-request(a)ipc.ipc.org>, SITE:INTERNET) To: ("RFC-822": <TechNet(a)ipc.org>,SITE:INTERNET) CC: ("RFC-822": <cwills(a)juno.com>,SITE:INTERNET), AIL.EHTP/PCL Subj: Re: Pins popping up RFC-822-Headers: Resent-Date: Wed, 13 Nov 1996 08:10:50 -0800 Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> Encoding: 53 Text Resent-Message-ID: <"zL0LY1.0.QSI.feSYo"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/7640 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] Hi Charles - One question: I would not expect a 13x4, 0.062, 8 layer assembly to be overly "flexible" - are you experiencing the problem due to simple handling or as part of a testing or stress screening operation? Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Pins popping up Author: [log in to unmask] at ccmgw1 Date: 11/12/96 10:29 PM Technet: I have a board about 13.5" x 4.5" (PC plug in card), .062" thick, 8 layer, FR4, 1 oz copper, 2 power planes, with 16 100 pin TQFP packages (0.5mm lead pitch) spread across the board (2 rows of 8), as well as many other PLCC and SOIC devices. The problem we are having with these prototypes is that some pins on the TQFP's pop up durring handling. The boards seem to be too flexable, which probably causes the pins to break off the pads. Is there a way to make the board more rigid besides using board stiffiners? In other words can anything be done as far as changing the board stack up, or will using thicker copper help this situation? Or are there different types of FR4 available? Or is there something I am not looking at? Also, what would be a good pad size for the 100 pin TQFP chip? Currently I am using 1.2mm x .25mm, but I think the IPC recommends 1.6mm x .35mm, but it doesn't look like it would allow any soldermask between pads. Or does anybody even bother with soldermask between pads at .5mm pitch? What is the middle ground? Thanks in advance! Charles Wills [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** <<<<<<<<<<<<<<< *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************