That is some funny s**t right there! Made my day. Who is it? regards, - Graham Collins -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Thursday, March 17, 2011 8:06 AM To: [log in to unmask] Subject: Re: [TN] Query on failure of assembled PCB Here 'tis: http://stevezeva.homestead.com/Black_Pad_Blues.wmv Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M. Sent: Thursday, March 17, 2011 6:39 AM To: [log in to unmask] Subject: Re: [TN] Query on failure of assembled PCB Rex, Well put!. The real problem with Peter's button is that it does exist but it doesn't work very well. It doesn't make ENIG disappear but it does add another strike against it every time it is pushed. I know several people including myself who push that button as often as possible and slowly but surely it has an effect. I'm not sure who wrote the attached "Black Pad Blues" tune but I like harmonic music and except for the name of the song, which I hate and I which they would redo the song as "ENIG Blues", but I keep a copy on my laptop desktop and I play it for every designer who asks me what I think about ENIG. Actually I'm surprised the tune isn't on Steve's web page. If it were I know it would be played often. 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 Rex Waygood Sent: Thursday, March 17, 2011 4:45 AM To: [log in to unmask] Subject: Re: [TN] Query on failure of assembled PCB I went to a lecture about 20 years ago by Peter Starkey who said that if there were a button that could make ENIG disappear as a surface finish from the face of the earth he would push it. I have often been second in line for that button. Some ENIG defects are worse with second reflow. Thin Ni can cause solderability problems. The problem often reveals itself when the second reflow is attempted. Thin Ni can result in joints that look OK but are not mechanically sound as complete wetting hasn't taken place. Then you can have porous gold or partially passivated Ni prior to gold deposition. Again this produces joints that look OK but the wetting to the Ni has occurred in patches on the pads. Both of these defects do not just affect BGAs. Shear testing on other chip components can reveal the weakness of the joints. When the cause is at its worst solderability is obviously very bad. Unfortunately there is an in between where the joints don't look too bad, but they are mechanically unreliable. I have seen components fall off the PCB when the board edge is tapped on a bench from these defects! There is also an ENIG problem which can be just associated with BGAs. I know this as we are awaiting the arrival of a remake! If the designer of the pcb has put tented or half tented vias amongst the BGA pads then microetch can get trapped in the vias which then prevents the electrochemistry working correctly at Ni plate. This gives poor Ni at the BGA pads causing poor solderability and unreliable joints. Any of these defects mean the boards are not usable but could result in shipped product with a compromised reliability if the defect is at a low level.. In the recent batch problem we had we thought the yield would allow us to recover the situation for the customer if we had the boards Hot Air Levelled. The boards looked absolutely normal but the yield was very low. Interestingly using state of the art HASL machines produced a finish even in the fine pitch BGA area that we would have been very comfortable doing the SMT on. The company doing the HASL were unable to optimise their hot air level as the pcbs were in routed panels and the machines are designed to work on complete master panels. These boards were HASL'd lead free. Where is the evidence that HASL is not suitable for fine pitch work? If we receive a HASL'd board it is unlikely to not solder. I would prefer to receive a pcb that has been through a HASL process prior to BBT and prior to our reflow process. I am sure there are other ENIG defects that may cause your problem but we have experience the three I have listed that might cause your problem. We have experienced other ENIG problems but they won't cause intermittent joints on BGAs! :-) Regards Rex Rex Waygood Technical Manager Hansatech EMS provides value manufacturing through engineering and quality Hansatech EMS Limited Benson Road Nuffield Industrial Estate Poole Dorset BH17 0RY +44 (0)1202 338200 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Uppina Nagaraj Sent: 17 March 2011 02:28 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 ----------------------------------------------------- ______________________________________________________________________ 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 -----------------------------------------------------