Hi Victor,
I don't have much information on that.
What I know is that after assembly and the temp cycling
test, the assemblies undergoes conformal coating before
they are integrated into the system.
I'm trying to get more information from my customer on this.
I'll discuss with you if I could get any further information.
Thanks & Regards,
U.Nagaraj
> 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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