Ed,
I am assuming final assembly is one up and not in an array? If it is an array has each section of the array been evaluated?
How many functional testes do you have? If multiple testers, have the same boards been run across all testers to insure there isn't one or multiple testers creating a defect?
When was the last PM and calibration ran on the testers, was it recent or close to the first you saw the lower yields?
When do you expect to have a replacement reel in?
Ted T.
-----Original Message-----
From: Ed Popielarski [mailto:[log in to unmask]]
Sent: Friday, November 01, 2013 12:05 PM
To: TechNet E-Mail Forum; Tontis, Theodore J
Subject: RE: [TN] SMT transformer failures
Do you know how the manufacturer of the transformer is testing them prior to shipping? NO
Are they 100% tested, functional and or hi-pot? UNK
I don't recall if you mentioned if samples were taken directly from the reel (prior to placement) and tested if so, what were the results? YES, OK prior to assembly, OK after reflow
After replacing the transformer do the boards pass test? YES, at the same fallout rate as prime pass.
Are they the same transformers from the reel in question or from a different reel? SAME REEL
Functional or ICT? FUNCTIONAL
Have samples been sent to the manufacturer for evaluation? YES
Has the test system or test operators been checked out that damage isn't being introduced at test? YES
Ed Popielarski
Engineering Manager
970 NE 21st Ct.
Oak Harbor, Wa. 98277
Ph: 360-675-1322
Fx: 206-624-0965
Cl: 949-581-6601
https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&spn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Theodore J Tontis
Sent: Friday, November 01, 2013 9:43 AM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures
Ed,
Do you know how the manufacturer of the transformer is testing them prior to shipping? Are they 100% tested, functional and or hi-pot?
I don't recall if you mentioned if samples were taken directly from the reel (prior to placement) and tested if so, what were the results?
After replacing the transformer do the boards pass test? Are they the same transformers from the reel in question or from a different reel? Functional or ICT?
Have samples been sent to the manufacturer for evaluation?
Has the test system or test operators been checked out that damage isn't being introduced at test?
Ted T
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Popielarski
Sent: Friday, November 01, 2013 11:11 AM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures
Robert,
These are VERY small SMT transformers (~20 would fit on a penny). No tape between layers, the wire gage is >40AWG as the wire measures approx.. 0.003" including the insulation. The wires (2) are would around the bobbin in parallel.
We don't test this material at incoming, since it's on tape & reel, it would be difficult to return to same, so Hi-pot testing degradation is not a possibility.
Replacing the transformer by hand has consistent failure rate to the original first pass. I've also examined them on the X-ray system (Dage Diamond) and see noting out of the ordinary before and/or after failure and/or replacement.
Ed Popielarski
Engineering Manager
970 NE 21st Ct.
Oak Harbor, Wa. 98277
Ph: 360-675-1322
Fx: 206-624-0965
Cl: 949-581-6601
https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&spn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Friday, November 01, 2013 8:21 AM
To: 'TechNet E-Mail Forum'; Ed Popielarski
Subject: RE: [TN] SMT transformer failures
Ok, That says there was not only a failure of the wire insulation but also of any tape layers between the windings.
So three failures in the same location:
Primary Wire Insulation
Secondary Wire Insulation
insulation tape between layers. (I assume this was there)
Sounds like someone was doing a high pot test, destroying the transformers, and then putting them in the "Good" bin? I doubt that.
Now another likely failure is a circuit failure where they are being used. A simple short on a board or other assembly / component failure might result in excessive current melting down a section of internal windings. That would be my guess. This might also explain the "Bad" insulation you saw coming off the wires.
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Popielarski
Sent: Friday, November 01, 2013 11:02 AM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures
Functional test fails on power up (no DCV SEPIC app) and ohmmeter confirms short between primary and secondary windings. Disassembled the transformer under a microscope, it's only 5mm X 5mm including the outer frame.
Ed Popielarski
Engineering Manager
970 NE 21st Ct.
Oak Harbor, Wa. 98277
Ph: 360-675-1322
Fx: 206-624-0965
Cl: 949-581-6601
https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&spn=0.0
11188,0.033023&ctz=420&t=m&z=16&iwloc=A
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, October 31, 2013 5:42 PM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures
I would ask again:
What lead someone to suspect a transformer as bad? What lead to disassembly in the first place?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Don Vischulis
Sent: Thursday, October 31, 2013 7:36 PM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures
Yes, this is a polyurethane based insulation system. My experience is with MW16C (polyimide). Based on general knowledge, polyurethanes are not very sensitive to solvents. I think that the fuzzy finish you observed is failure of the wire insulation because the coils are impregnated and the adhesion within the insulation is less than the adhesion within the impregnant.
My experience is that breaks inside the coil are due to flaws in the conductor. One failure mechanism is from expansion and contraction from thermal cycling. Usually it takes small diameter (39 awg) and some pretty extreme conditions with hundreds of cycles to cause this to happen. Another possibility is defective wire or handling damage. Does the manufacturer have any record of unplanned interruptions during the winding cycle? Is the manufacturer purchasing from a low cost source?
Sorry I can't offer more.
Don Vischulis
Sent from my iPad
> On Oct 31, 2013, at 10:07 AM, Ed Popielarski
> <[log in to unmask]>
wrote:
>
> NEMA MW82-C Class 180 C
>
> Ed Popielarski
> Engineering Manager
>
>
> 970 NE 21st Ct.
> Oak Harbor, Wa. 98277
>
> Ph: 360-675-1322
> Fx: 206-624-0965
> Cl: 949-581-6601
>
> https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&s
> pn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
>
>
> -----Original Message-----
> From: Don Vischulis [mailto:[log in to unmask]]
> Sent: Thursday, October 31, 2013 4:10 AM
> To: TechNet E-Mail Forum; Ed Popielarski
> Subject: Re: [TN] SMT transformer failures
>
> Any idea what type insulation is on the magnet wire or the NEMA
designation of the magnet wire?
>
> Don Vischulis
>
> Sent from my iPad
>
>> On Oct 30, 2013, at 12:04 PM, Ed Popielarski
>> <[log in to unmask]>
wrote:
>>
>> Good Morning Esteemed Colleagues,
>>
>> We have recently been experiencing increasing failure rates of an SMT
(5.2 X 5.2 X 1.2 mm) transformer. The first build in September showed about 6% fallout. Subsequent builds from the same reel have increased to 25% most recently. These components have been stored in a normal ambient environment.
I have verified and re-verified reflow conditions are well within manufacturer's specifications (confirmed by the manufacturer).
>>
>> When this problem was first identified, I "dissected" one of the
>> failing
devices and found the wire pair (primary and secondary) in good condition on the outer windings, but as I continued to unwind down to about 1/3 deep, the insulation began to stick both side by side and to subsequent layers which would "fuzz" as it was pulled apart with exposed copper implied.
>>
>> I am beginning to suspect "cold flow", a problem that was prevalent
>> in
the days of wire wrapped backplanes.
>>
>> Has anyone experienced a similar condition? The manufacturer has been
"working on it" since mid-September and has yet to provide any root cause and/or solution.
>>
>> Any insight would be appreciated.
>>
>>
>> Ed Popielarski
>> Engineering Manager
>>
>> [Description: FullLogo]
>> 970 NE 21st Ct.
>> Oak Harbor, Wa. 98277
>>
>> Ph: 360-675-1322
>> Fx: 206-624-0965
>> Cl: 949-581-6601
>>
>> https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&
>> s pn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
>>
>>
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud
>> service.
>> For more information please contact helpdesk at x2960 or
>> [log in to unmask]
>> _____________________________________________________________________
>> _
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or
> [log in to unmask]
> ______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
|
