Sorry, I am lost in translation. What is HOP?
Regards,
~wee mei~
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Monday, March 21, 2011 11:48 AM
To: [log in to unmask]
Subject: Re: [TN] Query on failure of assembled PCB
Look a bit skimpy on Au to me. HOP possibly is my guess for the fault (if it is, buy me a cup of coffee. Pete's will do:-), consider Ni-oxide is not easily solderable.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Uppina Nagaraj [mailto:[log in to unmask]]
Sent: Sunday, March 20, 2011 11:33 PM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Query on failure of assembled PCB
Hi,
Ni is around 3.9~5 microns & Au is around 0.07 to 0.10microns.
Thanks!
U.Nagaraj
> How thick is the ENIG?
>
> Victor,
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
> Sent: Wednesday, March 16, 2011 10:43 PM
> To: [log in to unmask]
> Subject: Re: [TN] Query on failure of assembled PCB
>
> U.Nagaraj
>
> Chris and Joyce have suggested good possibilities. The intermittent
> failures could be brittle solder joint fractures at BGA ball / PCB pad
> interface or they could be HOP failures. If the boards really do work
> immediately after they are built but are intermittent a couple of weeks
> later and they have not been under any mechanical stress then HOP might be
> the cause. With HOP you might get enough contact immediately after
> soldering to pass test but as the solder surfaces oxidize the contact
> resistance could increase causing intermittent failures.
>
> 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: Joyce Koo [mailto:[log in to unmask]]
> Sent: Wednesday, March 16, 2011 11:20 PM
> To: [log in to unmask]; Wenger, George M.
> Subject: Re: [TN] Query on failure of assembled PCB
>
> One major difference: the exit test is possibly connectivity test: open or
> short, not function. The BGA intermittent is a functional test. You
> could pass open or short, but still got intermittent fault. HOP may pass
> open short test if it got some contact, sounds like either bga cracked, or
> hOP,or microvia cracked. All of them will exhibit intermittent but
> partially show connectivity when apply pressure. Are those parts
> underfilled?
> --------------------------
> Sent using BlackBerry
>
>
> ----- Original Message -----
> From: Wenger, George M. [mailto:[log in to unmask]]
> Sent: Wednesday, March 16, 2011 10:42 PM
> To: [log in to unmask] <[log in to unmask]>
> Subject: Re: [TN] Query on failure of assembled PCB
>
> 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
>
>
>
>
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