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Induranga Randika , 12-16-2024, 12:16 AM

Hello everyone,

Normally for prototype I was using JLCPCB since 1 year. Recently I designed a PCB which involves high speed interfaces which need usual 10% impedance tolerance. But when ordering only I know that JLCPCB only support +-20% impedance tolerance after they sent me a follow up email saying "They currently don't have any service which provides impedance controlling according to impedance tables or fab notes as other fabricators do. "

Then what is their controlled impedance option in the order page even mean ?

My question is how they managed to even fabricate PCB's for very high speed interfaces like PCIe which need small tolerance ? This is too much which not to be omit in my opinion ? (Anyway I know they don't have HDI also. But 20% is way off for me.)

has anyone any experience with JLC about fabricating high speed boards and work without no SI issues with them ?

Robert Feranec , 12-16-2024, 06:04 AM

If impedance is important, then you may want to use a PCB manufacturer which is able to verify it (when you ask them, they will also send you the report from measurements). Possibly, you can include impedance coupons on your PCB and measure it by yourself (but then you also need the equipment).

If someone knows how accurate the impedance from JLCPCB is, please share this info. I am also interested to know (also if it is consistent between different batches).

corlas , 12-16-2024, 06:54 AM

we ordered some PCBs (45pcs total) with USB3 and only selected impedance control in the PCB specs, everything works fine. The worst thing is to use their specific stackup to be honest. I don't know how precise it is but since USB3 is okay, I think most of the interfaces will be fine.

Induranga Randika , 12-16-2024, 09:45 AM

Yeah Robert. I asked them about the report. They told, they won't give any verification

Induranga Randika , 12-16-2024, 09:47 AM

Thanks Corlas. How much of data transfer speed you could be able to archive ?

corlas , 12-16-2024, 10:32 AM

hard to tell, we use CYUSB3014-BZXI and I think the MAX data transfer is 250MB/s

Induranga Randika , 12-16-2024, 02:07 PM

@Robert Feranec Today I confirmed from JLCPCB live agent. They told, they only support 20% for now.

This is the response

QDrives , 12-16-2024, 03:53 PM

If I read all this, I think JLCPCB just does a defined stack-up. That is, the impedance is calculated theoretical depending on the stack-up and trace width.
If you want better, you need to go to another fabricator.

But the best question is from @Robert Feranec "*also if it is consistent between different batches*"!

Induranga Randika , 12-16-2024, 05:08 PM

Yeah

Sniper2 , 12-16-2024, 05:48 PM

that would be interesting