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MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

Dear Sirs and Madams,

 

Please tell us about the contents described in the application note AN85951.

AN85951 - PSoC® 4 and PSoC® 6 MCU CapSense® Design Guide URL

https://www.cypress.com/file/46081/download

 

Section 7.4.2 contains the following :

MaMi_1205306_0-1638753731696.png

"You should use flex circuits with thickness 0.01 inches (0.25 mm) or higher for CapSense."

What does the 0.01 inch shown in this sentence mean?

Is it the thickness of the flexible substrate?

Or is it the thickness of the copper foil on the flexible substrate?

We would like to know what 0.01 inch refers to.

 

Regards,

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1 Solution
Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi @MaMi_1205306 

 

The 0.01 inch is the total thickness of the flex PCB - the thickness of the flexible substrate. The regular copper thickness can be added to this. 

 

Best regards, 
Hari

View solution in original post

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3 Replies
Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi @MaMi_1205306 

 

The 0.01 inch is the total thickness of the flex PCB - the thickness of the flexible substrate. The regular copper thickness can be added to this. 

 

Best regards, 
Hari

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MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

Hari-san,

 

Thank you for your response.

I understood your answer.

However, We think that the thickness of a general flexible substrate is generally "12.5 to 25 um" or "0.5 to 50 mil".

MaMi_1205306_0-1638779700171.png

カバーレイ(の)層:Coverlay layer

(カバーレイの)接着層:Adhesive layer

銅箔(の)層:Copper layer

ベース(材の)層:Base layer

厚み(理論値):Thickness (Theoretical value)

 

0.01 inch = 0.254 mm

 

I think 0.01 inch is an order of magnitude different, but what about it?

Does that mean that the use of thin flexible boards is not recommended?

Please confirm again.

 

Regards,

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Hari
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi @MaMi_1205306 

 

That design would be fine. The total thickness in this case as well comes up to 0.1mm for the flex PCB and this design is supported by CapSense. We have flex kits that are of the same dimension and it will work reliably.

 

I will work with our documents team to get the AN updated with the right value. Thank you for pointing this out...

 

Best regards, 
Hari

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