How were the assemblies packed?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Toby Carrier
Sent: Wednesday, March 16, 2011 10:43 PM
To: [log in to unmask]
Subject: Re: [TN] Query on failure of assembled PCB
How were these assemblies stored for the 3-4 months?
Toby
On Wed, Mar 16, 2011 at 11:39 PM, Chris Mahanna <[log in to unmask]>wrote:
> Joyce,
> Agree 100%. I assumed from the story that both PBA tests were the same.
> If one root cause, and reflow fix and flexure fix then very likely hop.
> But he may well have more than one root cause.
> Chris
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
> Sent: Wednesday, March 16, 2011 11:20 PM
> To: [log in to unmask]
> 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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