Here we go again! If you want to get down to the root cause, have the assembly analyzed! One of the last times we had a similar discussion here the root cause turned out to be very interesting and as far as I remember no one "guessed" it correctly. Regards, Vladimir Igoshev SENTEC Testing Laboratory Inc. Quoting Uppina Nagaraj <[log in to unmask]>: > Hi George, > > Surface finish is ENIG. > > Regards, > U.Nagaraj > > > > U.Nagaraj > > > > What was the PCB surface finish? > > > > Regards, > > George > > George M. Wenger > > Senior Principal Reliability / FMA Engineer > > Andrew Corporation - Wireless Network Solutions > > 40 Technology Drive, Warren, NJ 07059 > > (908) 546-4531 Office (732) 309-8964 Mobile > > E-mail: [log in to unmask] > > > > -----Original Message----- > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Uppina Nagaraj > > Sent: Wednesday, March 16, 2011 10:28 PM > > To: [log in to unmask] > > Subject: [TN] Query on failure of assembled PCB > > > > Dear All, > > > > 1. We are manufacturers of PCBs. One of our customer has reported > > failure in assembled boards. The main observation is that after > > assembly, the assembled units were functioning normally > > and had passed all the stipulated electrical tests. These parts > > were kept at the assembly house for around over 3-4 months. Later > > when the assembled units were scheduled to be integrated into > > the system, the assembled units were tested again, but now they > > see failure. > > > > These are the inputs given to us.......... > > a) Failures are intermittent in nature. > > b) Failures are concentrated in and around the area where > > BGA is mounted. > > c) Some failures are recovered by applying mechanical stress on > > the PCB. > > d) Some are recovered by subjecting to reflow. > > e) There are no component failures. > > > > 2. Our customer's assembly process flow is… > > a) 100Deg C, 16 hours baking > > b) Assembly done within 24 hours after baking > > c) Pb-free reflow conducted with a peak temperature of 262Deg C > > d) Reflow is done 2 times (once for each side of components) > > e) Visual and physical inspection done > > f) Cycling done at -20~+70Deg C for 10 cycles. First 9 cycles > > are 30minutes per cycle and the last cycle is 1 hour cycle > > g) Electrical testing > > > > 3. We had retrieved a blank PCB from the same batch and conducted > > the following trial...... > > > > a) A standard step of baking prior to assembly (100Deg C, > > 16 hours baking) was skipped due to time constraint. > > b) 2x reflow done at customer's place using standard profile > > used for assembly of this part. > > > > Electrical Testing (BBT) on bare PCB passed . > > > > c) 10 cycles of temp. cycling done at customer's place using the > > standard cycling profile used for assembled unit. > > > > Electrical Testing (BBT) on bare PCB passed . > > > > d) Repeated 2x reflow (2nd time) at customer's place using > > standard profile used for assembly of this part. > > > > Electrical Testing (BBT) on bare PCB passed . > > > > Based on the above trial, we feel that the failure seen is > > not due to PCB failure. > > > > > > 4. This particular PCB is a 8 layer PCB, built using ISOLA FR370HR > > material. > > ----------------------------------------------------------------- > > > > > > Please share your inputs and thoughts on the failure phenomenon and > > how to ascertain if the failure is due to PCB or assembly. > > > > Thanks in advance! > > > > Best Regards, > > U.Nagaraj > > > > > > > > > > ______________________________________________________________________ > > This email has been scanned by the MessageLabs Email Security System. > > For more information please contact helpdesk at x2960 or [log in to unmask] > > ______________________________________________________________________ > > > > --------------------------------------------------- > > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > > 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 or (re-start) delivery of Technet send e-mail to > > [log in to unmask]: SET Technet NOMAIL or (MAIL) > > To receive ONE mailing per day of all the posts: send e-mail to > > [log in to unmask]: SET Technet Digest > > Search the archives of previous posts at: > > http://listserv.ipc.org/archives > > Please visit IPC web site > > http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums for additional > > information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 > > ext.2815 > > ----------------------------------------------------- > > > > > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 or (re-start) delivery of Technet send e-mail to > [log in to unmask]: SET Technet NOMAIL or (MAIL) > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search the archives of previous posts at: http://listserv.ipc.org/archives > Please visit IPC web site > http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 > ext.2815 > ----------------------------------------------------- > ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------