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Re: [TenTec] Orion 565 failure due to electromigration of solder

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Orion 565 failure due to electromigration of solder
From: Gary J FollettDukes HiFi <dukeshifi@comcast.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 16 Oct 2016 23:39:38 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
The definition of electromigration is migration of conductor material in a 
circuit trace due to the momentum transfer from charge carriers (usually 
electrons) flowing in the conductor traces and the phenomenon bears 
characteristics of diffusion. The species undergoing electro migration need not 
be ionic, or charged in any way. The electron flow is simply pushing the 
conductor metal out of the way.

Electromigration CAN NOT TAKE PLACE in the absence of significant current 
density flow in the conductor in question. 

In electromigration, conductors migrate atomistically in a direction orthogonal 
to a current flow, causing flow of conductor material in a path that leads away 
from the conducting trace. This phenomenon can cause either a short circuit to 
an adjacent trace or an open circuit in the trace if sufficient material 
migrates. Much effort to reduce this effect, especially in Aluminum 
metallization in IC chips, was undertaken in the late 1970’s. Electromigration 
on the macro scale, the size of PC boards and associated parts, has never been 

More likely what you saw was solder whisker formation, a recurrence of what 
took place decades ago with low Lead solders and which is coming to the 
foreground once again with Lead-free formulations. These whiskers can grow due 
to heat, stress and other environmental stresses, mostly in purer metals, but 
can also take place in certain alloys (no need for current flow) and cause the 
formation of short circuiting bridges as you describe. The small sizes of the 
whiskers, on the order of the wavelength of light, is what gives rise to the 
whitish appearance. These types of whiskers caused failures in satellites and 
in some nuclear power plant metering systems. The term “electromigration” is 
incorrectly applied to this phenomenon even in Wikipedia. They correct their 
mistake later in their discussion when they point out that no current flow is 
required for whisker formation to take place. Current flow is required for 
electromigration to take place, though the current can be a corrosion current 
in an appropriate corrosion cell.

They do show some pretty cool images of such whiskers, many of them several 
millimeters in length, more than enough to cause the problems you experienced. 

If you had a small sample of the stuff you removed, I could send you some nice 
scanning electron microscope images of them along with their compositions… That 
would take about 15 to 30 minute of my time.



> On Oct 16, 2016, at 10:48 PM, A R <raf_3@msn.com> wrote:
> Just recovered from a failure of my Orion 565 that looks to be a result of 
> ionic solder migration.
> Orion was purchased two years ago from original owner's estate. Details of 
> his operation/use are unknown.
> Replaced snaphat battery, A9 caps, and intermittent VFO encoder. Orion 
> performed flawlessly for over a year following those measures, and was 
> relegated to back-up status about 3 months ago.
> When it was brought back into service, receiver worked fine, but no 
> transmitter output on either ANT 1 or ANT 2 outputs. Two master resets were 
> performed, but no joy. Covers were removed, and interior subjected to the 
> burnt component "smell test", and visually inspected for any obvious causes 
> (loose cable connectors, etc.). Discovered powdery substance on the I/O board 
> that surrounded the entire periphery of TXEN 1 rca jack solder pad (perfectly 
> circular around solder pad) intersecting the adjacent +13vdc wire conductor 
> solder pad, with a "track" extending to ground side (anode) solder pad of 
> adjacent 5KP15A surge suppressing diode. Removed the powdery deposit using 
> Q-tips and 90% isopropyl, followed by judicial flushing with distilled 
> water.Gently and slowly dried with warm (not hot) air, and after 10 minutes 
> of ambient air dry time, applied power. All sytems are "go", and the Orion 
> lives again.
> I have never used the TXEN or TXOUT jacks, but don't know whether the 
> original owner did. At any rate, the condition (which I attribute to 
> electromigration of the solder) had to have resulted/propagated with no 
> externally applied potential to the TXEN jacks, since the condition only 
> became "fatal" after two years of problem-free operation/life. The internally 
> applied potential to the TXEN pad/lead is just +3.3vdc. And, the distance 
> from the TXEN's pad edge to the diode's anode (ground) pad edge is more than 
> 1/2 inch, and distance from the +13vdc pad edge is approx 3/16 inch. Since 
> the deposit was uniformly centered around the TXEN's pad (and, not the +13vdc 
> pad edge), it would seem that the donor was the TXEN pad/solder.
> Given the wide spacing between these pads/solder and the low potentials 
> involved in this case, the potential (no pun intended) for similar failure 
> conditions elsewhere (with closer pad separation) would seem quite possible. 
> So...I guess my counsel is to do a close visual inspection (under 
> magnification) of boards when unexplain/unprovoked failures occur. Or, maybe 
> better...periodic visual board inspections...or, even cleaning...BEFORE 
> electromigration causes a failure. Fortunately, in this case, the condition 
> didn't result in permanent (and catastrophic) damage. An ounce of 
> prevention....etc.
> 73,
> Allen--W7GIF
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