First production of KL25 based PCBs - firmware upload problem

[offin]

Hello,

We made a first production of 1000 PCBs with a KL25 IC. We are not able to upload the firmware with 40pcs. With another 30pcs, we were able to upload the firmware, but it stopped working after mounting the PCB into the casing. The other 930pcs are working well.

We use MCUXpresso software & MCU-link USB probe to upload the firmware. When trying to upload the firmware on the bad pcs, MCUXpresso says, "failed to receive response (to op 32) from server after 60000ms - timed out".

We are trying to understand what could be the problem. This is of course not easy to check the connections in the PCB. We are presently able to say this:
- the pins DIO, CLK RST and GND are connected to the programming port. I can not confirm there is no shortcut between two KL25 pins, but i do not think this is the case for the 70pcs.
- the pin VDD outputs 3,3V

I understand that the first possible reason is simply bad component solder on PCB. May be this is the reason, but 70 bad pcs from 1000pcs is indeed a lot (the usual rate of bad pcs with our previous KL27 based productions is less than 1%).

So my question is: do you have some other suggestions for some other control to do ?

Regards.

[jingpan]

Hi @offin ,

Can you share schematic? If you don't want to post it here, you can create a ticket in support.nxp.com. We can review your schematic.

Regards,

Jing

[offin]

Hello,

When i try to log in support.nxp.com, i see the following error: ErrorDescription=Unable to create user&ErrorCode=5&ErrorDetails=Federation ID of returned user did not match. So i finally post the schematics here.
Please let me know if you need other infos.

Regards.

[jingpan]

Hi @offin ,

PTA4 is NMI_b function. If you do not disable it in Flash setting, you should pull it up with a 4.7k resistor. The reset_b should connect a 4.7k~10k resistor to power and a 104 cap to ground. PTA3 is SWDIO. It's better to pull up with a resistor.

Regards,

Jing

[offin]

Hello,

NMI_b is disabled in the configuration of the boot loader.

I took 3 of the non working PCBs.
I added a R/C to reset_b.
And i added a pull-up resistor to SWDIO.

But this unfortunately does not change the behaviour of the PCBs.

May there was really a big problem during the production process (?)

We just started a new production. The programming process will be in end of december or beginning of january 2022. I will come back in this thread to tell you the results.

Regards.

[jingpan]

Hi @offin ,

Here is some guide. Please take a look.

Regards,

Jing

[offin]

Hello,

Thank you for these documents.

Lots of reading !!!

We will read this carefully and see if we can improve the PCB.

Regards.

[offin]

Hello,

Thank you for this tips.

We will make the changes in some of our non working PCBs, and then i will come back to you to tell you the results.

Regards.

[offin]

Hello,

Thank you for your help.
As soon as i have the up to date schematics, i will create a ticket with them in support.nxp.com .

Regards.