Drive Died (arcing between pins on the PCBA)

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Discussion Overview

The discussion centers around the recurring failure of a drive in a production area, specifically due to arcing between two inputs on a control board. Participants explore potential causes, including environmental factors and material accumulation, while considering the implications of voltage levels and manufacturing issues.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the possibility of spontaneous arcing between two points 5mm apart, seeking examples of voltage or gases that could facilitate such an event.
  • Another participant suggests that a wet and dusty atmosphere could lead to contamination that promotes arcing, asking about evidence of contamination on the PCB assembly.
  • A participant notes that the area is clean and dry, mentioning that the drive has been in use for six months and has failed multiple times in a short period, raising doubts about contamination as the sole cause.
  • One participant raises the question of whether anything in the environment changed before the first failure, suggesting that nearby equipment could have influenced the situation.
  • Another participant introduces the concept of "tin whiskers" associated with lead-free solder, suggesting that arcing might occur at solder joints and recommending the application of insulating paint to mitigate the issue.

Areas of Agreement / Disagreement

Participants express differing views on the causes of the arcing and failures, with no consensus reached on whether environmental factors, manufacturing issues, or material properties are to blame.

Contextual Notes

Participants note the lack of evidence for contamination and the results of a study on the incoming power feed, which showed no notable issues. The discussion remains open regarding the specific conditions that could lead to arcing.

MaintenanceMGR
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Hello:

I have a problem with a drive located in a small production area. It has failed three times due to arcing between two inputs to a control board. These inputs are about 5mm apart and the manufacturer is saying that this could be from material collecting on these terminals or from gases. Now I can understand material conducting between the inputs, but gases seems rather far fetched. The drive is not sealed and it is at regular atmospheric pressure and cooled with a small muffin fan. The drive does not use any high voltage conversion and the input voltage is only 480V. I remember that it usually takes about 3000V/mm for a spark to develop in air, but I can't find any thing in that range in the drive.

My question is it possible for an arc to develop spontaneously between to points 5mm apart? And if it is what are some examples of voltage or gases that may be present to facilitate such an event.

BTW: Please forgive my ignorance on some of this, I know enough only to get things wrong.
 
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MaintenanceMGR said:
Hello:

I have a problem with a drive located in a small production area. It has failed three times due to arcing between two inputs to a control board. These inputs are about 5mm apart and the manufacturer is saying that this could be from material collecting on these terminals or from gases. Now I can understand material conducting between the inputs, but gases seems rather far fetched. The drive is not sealed and it is at regular atmospheric pressure and cooled with a small muffin fan. The drive does not use any high voltage conversion and the input voltage is only 480V. I remember that it usually takes about 3000V/mm for a spark to develop in air, but I can't find any thing in that range in the drive.

My question is it possible for an arc to develop spontaneously between to points 5mm apart? And if it is what are some examples of voltage or gases that may be present to facilitate such an event.

BTW: Please forgive my ignorance on some of this, I know enough only to get things wrong.

Welcome to the PF.

If the atmosphere is wet and dusty, there could be an accumulation of gunk that helps the arc to happen. Do you see evidence of contamination in other areas of that PCB assembly? Have you considered cleaning and conformally coating the PCBA in that area?
 
berkeman said:
Welcome to the PF.

If the atmosphere is wet and dusty, there could be an accumulation of gunk that helps the arc to happen. Do you see evidence of contamination in other areas of that PCB assembly? Have you considered cleaning and conformally coating the PCBA in that area?

The area is pretty clean and not wet. Specifically the area is a show area for customers that does small production runs, so they keep up with standards very well. Also the drive has been installed for 6 months, and recently the original failed and then two replacements failed as well, within 2 weeks from start to finish. So contamination could have caused the first but the succeeding two, ??
 
MaintenanceMGR said:
The area is pretty clean and not wet. Specifically the area is a show area for customers that does small production runs, so they keep up with standards very well. Also the drive has been installed for 6 months, and recently the original failed and then two replacements failed as well, within 2 weeks from start to finish. So contamination could have caused the first but the succeeding two, ??

Also we have conducted a study on the incoming power feed, which had nothing of note within a ten day study. My gut is telling me this could be manufacturing issue, but I don't want to take a stand on this without a better understanding of the science and how arc's can form.
 
How can you be sure that it was arcing between those 2 pins that caused the failures? Was anything else changed in the environment around the drive shortly before the first one failed? Like a new piece of equipment being used/installed nearby?

Can you post a picture of the pins you are talking about?
 
Lead free solder is notorious for "whiskers". Search on "tin whiskers"

http://nepp.nasa.gov/whisker/Is the arc-over right at a soldered joint?
If so,
Try applying a dab of "Glyptol" insulating paint, or ordinary polyurethane woodworker's varnish (oil based) over the solder pads on the next board.

I'd guess 480 makes quite a flash when it goes. Current limiting fuses like Shawmut 101 might help preserve some clues.
 

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