Author Topic: Flat-flex "dendrites"  (Read 2256 times)

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Offline I_Code_4_HugsTopic starter

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Flat-flex "dendrites"
« on: July 04, 2018, 07:16:31 pm »
My Samsung Blu-ray player had been acting up by randomly switching off.  Upon disassembly, finding nothing loose, I put the cable under the microscope and found "dendrites" shown in the attached image.

Disconnecting the flat-flex solved the problem.  Simple fix, but interesting failure mode.

Has anyone else seen something similar?
 
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Online joeqsmith

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Re: Flat-flex "dendrites"
« Reply #1 on: July 04, 2018, 07:40:44 pm »
Yes, on a hard drive ribbon cable that went to the head. 

Offline kony

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Re: Flat-flex "dendrites"
« Reply #2 on: July 04, 2018, 07:41:32 pm »
What voltage is present across those two tracks? Looks like electromigration of the printed thick film paste metal to me.
 

Offline In Vacuo Veritas

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Re: Flat-flex "dendrites"
« Reply #3 on: July 04, 2018, 08:29:31 pm »
Looks like CAF.
 

Offline chickenHeadKnob

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Re: Flat-flex "dendrites"
« Reply #4 on: July 05, 2018, 03:29:47 am »
What voltage is present across those two tracks? Looks like electromigration of the printed thick film paste metal to me.
I would agree there must be a DC voltage present, one side is clearly an anode the other cathode. As I understand tin pest is different, it generates from the surface energy of the plated tin all by itself. With even  no DC present, you would  expect whiskers coming in randomly from all directions.
 

Offline helius

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Re: Flat-flex "dendrites"
« Reply #5 on: July 05, 2018, 04:23:49 am »
Looks like CAF.
For those playing along at home, CAF are conductive anodic filaments.
This failure mode can be very hard to detect when it migrates on interior layers.
 

Offline mzacharias

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Re: Flat-flex "dendrites"
« Reply #6 on: July 06, 2018, 05:31:43 pm »
SATA connector, never used, went up in flames inside my desktop computer. Apparently they can grow these internal shorts.
 

Offline Ranayna

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Re: Flat-flex "dendrites"
« Reply #7 on: July 06, 2018, 07:42:14 pm »
Those Molex to SATA adapters with the molded SATA power connector are infamous in IT.
They spawned the expressen "Molex to SATA - lose all your data"...
There are a lot of pictures of various SATA devices going up in flames, and in almost all cases, one of those stupid things was used.
 
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Offline envisionelec

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Re: Flat-flex "dendrites"
« Reply #8 on: July 06, 2018, 09:20:53 pm »
Yes, on a Maytag dishwasher control panel. $150 for a new one...  :--

You might be able to blow the dendrites away with a carefully controlled burst of energy between the two conductors.
« Last Edit: July 06, 2018, 09:22:24 pm by envisionelec »
 

Offline exit_failure

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Re: Flat-flex "dendrites"
« Reply #9 on: July 06, 2018, 09:57:11 pm »
Has there been any real explanation for the countless instances of melted or even burning SATA to Molex adaptors? Thin wires? Bad mechanical construction? Divine retribution?
 

Offline german77

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Re: Flat-flex "dendrites"
« Reply #10 on: July 07, 2018, 01:25:27 am »
Has there been any real explanation for the countless instances of melted or even burning SATA to Molex adaptors? Thin wires? Bad mechanical construction? Divine retribution?
Yes basically they are made as cheap and fast as possible. The cables inside are basically not in the correct position and some build failures like the flat-flex until they arc.

This video has a nice examples of the bad manufacturing
 

Offline oventech

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Re: Flat-flex "dendrites"
« Reply #11 on: July 13, 2018, 03:17:48 am »
Are they made with a mechanical  connection?    Reminded me of tin whiskers due to ROHS.
 


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