The minimum clearance/creepage distance for the outside and inner PCBs

[Ashish1710]

Hello FEDEVEL family,

I am new in Automobile domain, I have one query in that they mention for measure the clearance/creepage distance they use IEC60664-1 standard and material group better than IIIb, pollution degree 2.
and I'd like to confirm the minimum clearance/creepage distance for the outside and inner PCBs.
the Input voltage is 400V and 800V DC

How I confirm the minimum clearance/Creepage distance .
Is there any calculation formula or document available

Thanks in advance...

[qdrives]

If I look a bit at some pictures of 60664, table 4 material group I needs a CTI >= 600, group II CTI >= 400 and group III CTI >= 100.
So you need to check what the requirements are for the CTI to get in the standard "printed wiring material". You would need to ask the fabricator what the CTI of your board will be.
Then there are the tables in 60664 that state the creepage and clearance required for 400V and 800V.
Do not forget the distances in IPC2221 too. Both state the MINIMUM.

One other note: If you want to claim that you product complies to 60664-1, you need to own a copy of it.

[Ashish1710]

qdrives Thanks for the information.
The CTI is 100 ≤ CTI < 175.

Based on following information how I calculate/measure the clearance/creepage distance for the outside and inner PCBs

1.IEC60664-1 standard
2.Material group better than IIIb,
3.Pollution degree 2.
4.Input voltage is 400V and 800V DC

[qdrives]

It is best to own the standard. It is not the cheapest standard, to be polite.

However, if I am not mistaken, the inner layers are pollution degree 1 as the outside pollution cannot reach it.
Then you need to determine the impulse withstand voltage.
This table then states the clearance you need http://i.stack.imgur.com/2kdPC.jpg
And for the creepage it is this one https://i.stack.imgur.com/9RKgF.jpg

Is the mentioned CTI (100...175) of what your board is or what material group IIIb is?

[Ashish1710]

From manufacture we received following information

1.Standard -IEC60664-1
2.Material group - IIIb,
3.Pollution degree- 2.
4.Input voltage is 400V and 800V DC
5. CTI- 150

[qdrives]

If your material group needs to be "better than IIIb", it cannot have a CTI of 150. CTI must be above 175. That means you need to use a different PCB material.

A CTI of 150 sounds like a polyimid board to me. Most FR4 boards have a CTI > 175, or material group IIIa.

Here is a good (first) post for you on LinkedIn:

https://www.linkedin.com/pulse/alfs-musings-20-alfonso-mart%25C3%25ADnez-de-la-torre/

[Ashish1710]

I received feedback from the supplier that the clearance/creepage for the outside and inner PCBs is different.
The minimum clearance and creepage for outer PCB is 2.4mm & 4.8mm. The minimum clearance and creepage for inner PCB is both 1mm

[qdrives]

So how did your supplier come with those values?

"How I confirm the minimum clearance/Creepage distance." -- Do you simply have to confirm that the supplier did it correct?

[Ashish1710]

Based on following input supplier come with those value

1.Standard -IEC60664-1
2.Material group - IIIb,
3.Pollution degree- 2.
4.Input voltage is 400V and 800V DC

[qdrives]

So should it be material group IIIb or better than IIIb (i.e. IIIa, II or I)?

[Ashish1710]

material group better than IIIb

[qdrives]

So if it needs to be "better than" IIIb, it cannot be IIIb, which also means it cannot have a CTI of 150.

Today there was the second post on creepage and clearance. This time according to 60664.

https://www.linkedin.com/pulse/alfs-musings-21-alfonso-mart%25C3%25ADnez-de-la-torre/

[Ashish1710]

I have only this information from supplier. and supplier also not entertainment on this topic. they said this value are correct as per standard
But I want to verify how they calculate those value . And I don't have much knowledge on this topic.
Please consider you CTI based on better than" IIIb , PCB material is FR-4 and help me how to calculate/verify creepage and clearance based on those value.

[qdrives]

Let me ask you another set of questions:
- What is/does your supplier? Is it a design house, a fabricator, assembly company? Do they sell you the complete product?
- What is your role exactly?
- What does your company do?

I am asking these questions as I am trying to understand WHO should do WHAT.

So in other words:
- Who designs the product?
- Who builds it (fabrication and/or assembly)
- Who sets up the specifications
- Who is responsible for the 'quality' and safety.

As I stated before, whenever you want to claim that it complies to 60664, you need to own that standard. In that standard are all the details to calculate the creepage and clearance.
If your supplier is a fabricator or assembly company, they can tell you what the CTI is, but not what the pollution degree is.
If your supplier is a design house, then they should be able to provide you with all the details so you can verify (their documentation). However, from what you have shown here, if that were the case, I would switch to another design house.

In my opinion, the company that designs it, should have the standard and be able produce documentation on the calculations.
This documentation can/should be used for the quality and safety for verification.
The fabricator should tell you what the CTI is, but this (minimum) should be specified in the production data to begin with (it must be better than the requirements).
The party that set the specifications give the pollution degree, max altitude, and possible standards to comply too.