I agree, except run them 10C hotter than normal reflow.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
Sent: Friday, November 01, 2013 12:53 PM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures
I recommend You to pass 100 transformer through Reflow soldering (without
PCB, on a plate), check them through electrical test and than pass them
through the cleaning process and than check them ET.
If the PCB pass 2 reflow soldering process, pass them the same.
On Fri, Nov 1, 2013 at 6:42 PM, Theodore J Tontis <[log in to unmask]
> wrote:
> 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&s
> pn=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&s
> pn=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,-122.64357
> >> 8& s pn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A
> >>
> >>
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--
Best Regards,
*Reuven Rokah*
Mobile: 972-52-6012018
Tel: 972-3-9360688
Fax: 076-5100674
<http://www.rokah-technologies.com/>[log in to unmask]
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