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&spn=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
>>
>>
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