Ultrasonic welding and nRF52

[kmalmiv16]

Hi,

our product is small tag, size of 70x35mm2. 

Plastic covers are welded together and now looks like after welding some HW does not work properly. Flashing is successful, but it does not operate as it should. It looks like it is in some sort of reset loop. Average current consumption is about 4mA, so it look like CPU is operational.

Yes, we have sleep clock with low frequency oscillator and crystal. We know that crystal is sensitive for ultrasonic, but it does not help when we have changed the crystal.

How about nRF52 is SoC. How about its bonding wires, could those be harmed by ultrasonic somehow? Those are bonded by ultrasonic in fab, isn't it? Frequency is probably higher in IC production 60kHz? Whereas we are using 25kHz for ABS welding.

Thank you in advance!

MVH,

        -Kari

[Andreas]

Hi Kari,

 

We know that quite a few of our customers do manufacture their enclosures, housings or parts of it using ultrasonic welding, at least to some extent. To date we have no reports that this has damaged our parts.

 

Still, I fail to see how a broken bonding wire would cause this issue. What is the reset reason? Do you measure stable voltages on all DEC pins (except perhaps when resetting)? Have you changing the LF clock source, or running a simple code that just initializes the oscillators, and reports the outcome e.g. by toggling a GPIO?

 

Best regards,

Andreas

[kmalmiv16]

Hi Andreas,

Thanks for quick response!

OK, good you have not heard any issues with ultrasonic welding and bonding wires. Then there might be something else,

LF clock is running, voltages are ok in all pins, flashing is successfull (=>HF clock is running), but device's average (continuously) current consumption is about 4mA. Regularily there is 7mA current pulse, see figure.

I will continue studies...

Rgds,

      -Kari-

[Kenneth]

Hi Kari,

Have you tried some basic \blinky example to check if pins are operational? Have you tried debug the application to check for asserts? What about just using a simple BLE beacon example without any pins or debug output? Maybe there is a floating input (e.g. UART flow control or RXD) that is not connected.

Best regards,
Kenneth