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Anonymous Poster

PCB testing

03/12/2008 7:59 PM

Hi

Please help me to explain the concept of the term "Isolation" used while electrical test of PCBs.I want to know the causes of isolation, as our GM says it always happens because of less pressure i.e 450psi applied to panels while lamination(But recommended pressure is 350 psi).Please explain the other factor i.e baking before lamination etc. is it responsible for that or not?

Thanks

Antonio Gonzeppa
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Snaketails
Guru

Join Date: Sep 2007
Location: Wrong end of the yellow brick road in Oz
Posts: 930
Good Answers: 15
#1

Re: PCB testing

03/14/2008 12:08 AM

I'm guessing your building the PCB's in your company? could you give more information in your build process?

Just curious, I'm not up with PCB lamination technology as I possibly should be.. I'm more in the net testing area, usually with flying probe systems.

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Anonymous Poster
#2
In reply to #1

Re: PCB testing

03/14/2008 7:24 AM

While lamination we press the kaptons (Polymide) to the bare copper (i.e after exposing & plating) and the we press it at 365F, then we do immersion gold and after this we send it to electrical test.There we got the reply of Isolation failure.I want to know is it concerned with pressure as I am already pressing at the pressure 450psi) higher than the recommended (350psi).Please hepl me.

Thanks

Antonio
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Keywalker
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Join Date: Mar 2006
Location: Valdosta, GA
Posts: 361
Good Answers: 8
#3
In reply to #2

Re: PCB testing

03/14/2008 4:11 PM

This is just a guess as I am not an expert in this area but I would recommend going back to the recommended 350 psi. If the traces on the board do not pass the isolation test that indicates to me that they are not sufficiently seperated from one another some how. Electrical isolation means that current cannot flow between the conductors. The higher the voltage the greater the likelyhood that the current will jump to another conductor in the circuit. Excess pressure may be eliminating some of your isolating material from the board.

This is of course totally unrelated to electrical isolation by using a transformer to isolate AC from AC.

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Snaketails
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Join Date: Sep 2007
Location: Wrong end of the yellow brick road in Oz
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#4
In reply to #3

Re: PCB testing

03/16/2008 8:52 PM

I would tend to this as well, that the extra pressure could be pressing the track layout in the mid layers thru the substrate

Is the tracks clean, and free of burrs after the etching process, this could be piercing thru the substrate layers with the extra forces and breaking your isolation barrier in the HI-POT tests?

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Su
Participant

Join Date: Aug 2010
Posts: 1
#5

Re: PCB testing

08/20/2010 10:25 AM

Hey,

I am new to this field of testing and quality analysis. I have worked with PCB boards but would like to know how to test a whole order of PCB boards coming in before I start assembling my unit. Is there a way to test the boards for quality? Really appreciate your help.

Thank you
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Snaketails
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Join Date: Sep 2007
Location: Wrong end of the yellow brick road in Oz
Posts: 930
Good Answers: 15
#6
In reply to #5

Re: PCB testing

09/02/2010 9:36 AM

Request that your PCB manufacturer run a opens/shorts test on the PCB before delivery, I know a few of the PCB fabrication houses here in Australia run Probots to test their PCB's before dispatch

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