Re: [PSES] low voltage insulation coordination

[Peter Tarver]

It’s important to remember that, while conformal coatings do have incidental 
insulative functions, test houses (in general) only accept them for the 
purposes of keeping the underlying surface clean, thereby reducing the PD.

Some solder masks have been tested in end-products as conformal coatings, but 
not many have certifications for that application.


Peter Tarver

From: Richard Nute
Sent: Wednesday, May 17, 2017 12:43

Solder mask is, necessarily, a reasonable solid insulator.  The trace-to-trace 
insulation construction is

trace - solder mask - air - solder mask - trace

The solder mask is thin, so there is a depression between the traces.  This 
depression makes air a part of the insulation between the traces.

The construction is three capacitors in series.  Assuming the areas of each 
capacitor plate is the same, the capacitance of each is a function of the 
dielectric constant (and the distance through the dielectric).  The dielectric 
constant of air is 1; the dielectric constant of the solder mask is greater 
than 1.  The voltage divides according to the capacitance of each capacitor.  
The air is the weakest link, and will break down.  The heat of the arc may 
damage the solder mask.

A conformal coating is thicker, and would not have as much depression between 
traces; its dielectric strength would be higher than a solder resist coating 
scheme.

Rich

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Re: [PSES] Q on Systems Integration and Testing Requirements

[Ron Wellman]

Many times on this forum it has been determined that B + B does not always =
B. Test to make sure and then declare victory if the results are B. 

 

Best regards,

Ron Wellman

 

From: Grasso, Charles [mailto:charles.gra...@dish.com] 
Sent: Wednesday, May 17, 2017 1:50 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Q on Systems Integration and Testing Requirements

 

Hi,

 

Scenario: Company A is the manufacturer of  a PC tested and compliant to FCC
Class B.

Company B is the manufacturer of a USB accessory tested and compliant  to
FCC Class B.

 

Company A imports the accessory and distributes the accessory as part of the
system.
The accessory is not changed in anyway.

 

Q1 Is additional testing REQUIRED ?

 

If the accessory is now rebranded to reflect the logo from company A, same
question.

 

Q2 Is additional testing REQUIRED ?

 

If the answer to Q1 is No and the answer to Q2 is Yes - please explain the
difference

 

TIA

 

Best Regards

Charles Grasso

Compliance Engineer

Echostar Technologies

(w) 303-706-5467

(c) 303-204-2974

(e)   charles.gra...@dish.com

(e2)   chasgra...@gmail.com

 

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Re: [PSES] Q on Systems Integration and Testing Requirements

[John Woodgate]

The regulator cannot tell that the product with the A logo is identical
internally to the product with logo B. If company B is not totally
trustworthy, there might be differences.

 

With best wishes DESIGN IT IN! OOO - Own Opinions Only

www.jmwa.demon.co.uk   J M Woodgate and
Associates Rayleigh England

 

Sylvae in aeternum manent.

 

From: Grasso, Charles [mailto:charles.gra...@dish.com] 
Sent: Wednesday, 17 May 2017 21:50
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Q on Systems Integration and Testing Requirements

 

Hi,

 

Scenario: Company A is the manufacturer of  a PC tested and compliant to FCC
Class B.

Company B is the manufacturer of a USB accessory tested and compliant  to
FCC Class B.

 

Company A imports the accessory and distributes the accessory as part of the
system.
The accessory is not changed in anyway.

 

Q1 Is additional testing REQUIRED ?

 

If the accessory is now rebranded to reflect the logo from company A, same
question.

 

Q2 Is additional testing REQUIRED ?

 

If the answer to Q1 is No and the answer to Q2 is Yes - please explain the
difference

 

TIA

 

Best Regards

Charles Grasso

Compliance Engineer

Echostar Technologies

(w) 303-706-5467

(c) 303-204-2974

(e)   charles.gra...@dish.com

(e2)   chasgra...@gmail.com

 

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[PSES] Q on Systems Integration and Testing Requirements

[Grasso, Charles]

Hi,

Scenario: Company A is the manufacturer of  a PC tested and compliant to FCC 
Class B.
Company B is the manufacturer of a USB accessory tested and compliant  to FCC 
Class B.

Company A imports the accessory and distributes the accessory as part of the 
system.
The accessory is not changed in anyway.

Q1 Is additional testing REQUIRED ?

If the accessory is now rebranded to reflect the logo from company A, same 
question.

Q2 Is additional testing REQUIRED ?

If the answer to Q1 is No and the answer to Q2 is Yes - please explain the 
difference

TIA

Best Regards
Charles Grasso
Compliance Engineer
Echostar Technologies
(w) 303-706-5467
(c) 303-204-2974
(e) charles.gra...@dish.com
(e2) chasgra...@gmail.com


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Re: [PSES] low voltage insulation coordination

[Richard Nute]

The only time I’ve seen trace-trace breakdown was on a PV combiner circuit 
board, where the creepage distance was about ¼ of what was called out by the 
standard.  The resulting failure was repeatable using impulse voltage withstand 
testing, which suggested that it was a clearance failure rather than creepage.  
The board was not conformal coated, although there was solder mask.


Solder mask is, necessarily, a reasonable solid insulator.  The 
trace-to-trace insulation construction is


trace - solder mask - air - solder mask - trace

The solder mask is thin, so there is a depression between the traces.  
This depression makes air a part of the insulation between the traces.


The construction is three capacitors in series.  Assuming the areas of 
each capacitor plate is the same, the capacitance of each is a function 
of the dielectric constant (and the distance through the dielectric).  
The dielectric constant of air is 1; the dielectric constant of the 
solder mask is greater than 1.  The voltage divides according to the 
capacitance of each capacitor. The air is the weakest link, and will 
break down.  The heat of the arc may damage the solder mask.


A conformal coating is thicker, and would not have as much depression 
between traces; its dielectric strength would be higher than a solder 
resist coating scheme.


Rich





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Re: [PSES] low voltage insulation coordination

[Ralph McDiarmid]

A classic reference.  We have a copy in our library here.

The only time I’ve seen trace-trace breakdown was on a PV combiner circuit 
board, where the creepage distance was about ¼ of what was called out by the 
standard.  The resulting failure was repeatable using impulse voltage withstand 
testing, which suggested that it was a clearance failure rather than creepage.  
The board was not conformal coated, although there was solder mask.

I’ve long assumed that creepage distance requirements in 60664 have lots of 
margin built in.  Pollution degree microenvironments are defined in a way which 
makes distinction a little vague.

Pollution degree 2
Only non-conductive pollution occurs except that occasionally a temporary 
conductivity
caused by condensation is to be expected

Pollution degree 3
Conductive pollution occurs or dry non-conductive pollution occurs which becomes
conductive due to condensation which is to be expected.

PD2 likely a suitable assumption for any used at home, at an office, a 
classroom, a retail store in mall,  or in a well air-conditioned building.  
However, I wouldn't expect condensation in those environments.  

PD3 likely a suitable assumption for equipment in a garage, a shed, a workshop, 
or inside buildings which are neither air-conditioned nor heated, or in 
bathrooms, change rooms and the like.  Accumulation on surface of the PCBs and 
on components could be conductive when dry.  (e.g. soot or carbon dust)  And, 
condensation would be expected.


Ralph McDiarmid
Product Compliance
Engineering
Solar Business
Schneider Electric


From: Richard Nute [mailto:ri...@ieee.org] 
Sent: Wednesday, May 17, 2017 10:53 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] low voltage insulation coordination


With the help of Dan Roman (thanks!), the research into clearance and creepage 
distance by Klaus Stimper, "The physical fundamentals of LOW-VOLTAGE INSULATION 
CO-ORDINATION" is now available at:

http://www.ieee-pses.org/Downloads/low_voltage_insulation_coordination.pdf

This classic research is the basis for IEC 664 and IEC 60664-1 standards.  If 
you have ever wondered why our spacings are what they are, this treatise is for 
you.  Enjoy.

Best regards,
Rich

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Re: [PSES] Mil-Std-704A

[Brian O'Connell]

Ametek. And the imperious power of Python. All hail the emperor.

Also look at Mil Std 1275.

Brian


From: Gray, David [mailto:dg...@tuvam.com] 
Sent: Wednesday, May 17, 2017 8:33 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Mil-Std-704A

Hi group, Have anyone performed Mil-Std-704A testing? I am looking for 
information on Mil-Std-704a section LDC 104. What test equipment do you use and 
any software associated with it.

Thanks In advance
David Gray

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[PSES] low voltage insulation coordination

[Richard Nute]

With the help of Dan Roman (thanks!), the research into clearance and 
creepage distance by Klaus Stimper, "The physical fundamentals of 
LOW-VOLTAGE INSULATION CO-ORDINATION" is now available at:


http://www.ieee-pses.org/Downloads/low_voltage_insulation_coordination.pdf

This classic research is the basis for IEC 664 and IEC 60664-1 
standards.  If you have ever wondered why our spacings are what they 
are, this treatise is for you.  Enjoy.


Best regards,
Rich



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[PSES] Mil-Std-704A

[Gray, David]

Hi group, Have anyone performed Mil-Std-704A testing? I am looking for 
information on Mil-Std-704a section LDC 104. What test equipment do you use and 
any software associated with it.

Thanks In advance
David Gray

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[PSES] Radio Equipment Labeling - Brazil and Japan

[Jim Hulbert]

Greetings.  I have a question regarding labeling of radio equipment in Brazil 
and Japan.

Suppose we have a product with an integrated WiFi module.  U.S. FCC Rules are 
clear that the end product must have a visible label that states the equipment 
contains a module with FCC ID: xx.   I think there is something similar for 
Canada IC certification.

However, are there similar regulations for the Brazil Anatel certification or 
the Japan MIC certification?  Neither of these certification marks on the 
module will be visible or accessible to the user after the module is 
integrated.   However, I cannot find anything in the Anatel or MIC labeling 
requirements that state the end product needs any labeling for the integrated 
module.  Common sense tells me there should be a label, but our product design 
team of course wants the fewest number of labels possible.  If it's mandatory, 
there will be no argument, but I can't find anything in the regulations that 
says it is mandatory.

Can someone on this list provide me a little guidance?

Thank you.

Jim Hulbert
Pitney Bowes




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