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October 2013

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Subject:
From:
"Whittaker, Dewey (EHCOE)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Whittaker, Dewey (EHCOE)
Date:
Wed, 30 Oct 2013 19:00:23 +0000
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What, you think my career is winding down and I'm just left with my core competency?
Dewey 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Wednesday, October 30, 2013 11:51 AM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures

I have a lot of experience (unfortunately) with SMT transformers falling apart but it is not usually the windings themselves but rather the core bonding adhesive separating.  In my experience, the insulation on the windings is pretty rugged.  It takes a lot to degrade that material so I would suspect exposure to something nasty (solvent wise) or else as received from the manufacturer of the wires.  Fuzzy could be anything......go ahead Dewey......!!

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
Sent: Wednesday, October 30, 2013 11:09 AM
To: [log in to unmask]
Subject: Re: [TN] SMT transformer failures

What kind of failure mode?


On Wed, Oct 30, 2013 at 7:04 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
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>
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>
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*Reuven Rokah*

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