We are having a very difficult time soldering the nRF52840 to the PCB. Our Operations Department is asking what the lead finish of the BGA balls is. Would be great to get on the phone with you guys to discuss all the things we have tried. You might have some ideas. Thank you!
Hi John,
hm.. their must be something wrong during the production, soldering, the failure rate is most decently form the IC not being properly soldered to the PCB.
Have you given an feedback to the production house, that the IC is not soldered properly? Then they will most likely adjust the amount of solder paste, to get the IC to sink deeper and then get better soldered to the PCB.
- This is not my area of expertise, but I have sent a request to our package expert, so he might have some more suggestions.
I will also hear with one from our test group, she's back on Monday.
Best regards,
Kaja
Hi Kaja,
Thanks for getting back to me. We solder the nRF52840 right here in our facility, so I work with the folks that are trying to resolve this soldering issue. We've tried different stencils and oven profiles but we don't have the process good enough yet.
I was wondering, however, if the VSS ball (B7) becomes unsolderd from the PCB, will that cause the internal 1.3V or 1.1V regulators to fail? We are using the on-board buck regulator to generate the core voltage as shown in Figure 212 of the product spec.
Thank you!
Hi Kaja,
Is there any chance we could have a conference call with your package expert for the nRF52840? Our process people have done everything they can but we are still seeing many PCBs where the nRF52840 is resetting. We are temperature cycling the PCBs in our environmental chamber from +70C to -30C. All resets are occuring very close to when the chamber gets to -30C. We've never seen a reset at any other temperature. We also noticed that the reels have an expiration date. We've made a lot of these boards with ICs that are a few months past the expiration date. Not sure if this is an issue because we had some newer reels, made some PCBs from those parts and we are still seeing the problem. We could send some of these ICs back to you for your inspection. We don't believe the reset issue is due to the power circuitry, but we will tripple check this. We operate the PCB from two AAA alkaline batteries and VCC is generated from an external boost supply with a 3.3V output. We use the nRF52840's internal buck regulator to generate 1.3V for the core. There are many DECn pins on this processor and the product spec doesn't get into a lot of details on their function. Our circuit is basically a copy of Reference Circuit 5 shown in Figure 212 of the product spec. If we short out any of the DEC caps, the processor resets. Thank you!
Hi John,
we are waiting for a reply form our production house at the moment,to see if they have an updated reflow profile for us.
If they have an updated one it would be great if you could test that before sending us boards, to see if that fixes the problem.
Could you send some pictures of the failing boards?
Have you preformed some X-rays? - If yes, tt would be great to have a look at those as well.
John said:I was wondering, however, if the VSS ball (B7) becomes unsolderd from the PCB, will that cause the internal 1.3V or 1.1V regulators to fail? We are using the on-board buck regulator to generate the core voltage as shown in Figure 212 of the product spec.
John said:We don't believe the reset issue is due to the power circuitry, but we will tripple check this.
- Difficult to say, but not having proper grounding of the IC, not specifically B7, can probably contribute to the issue.
Could you also share the design files? - So that I can have a look at the design as well.
Best regards,
Kaja
Hi John,
I'm trying to set up a meeting with our package expert, but his in Asia, so we have to find a day where you can join the call in the evening (your time), because we want our production house to join as well.
But they would like some more information from you:
1) What kind of solder paste are you using ? SAC305?
2) Can you return failure samples so that we can conduct solderability test to check pad status?
3) Is this your first time using this device?
4) Is this your temperature setting in anyway different from the reflow profile?
5) Could you share pictures of the failing boards?
6) X-rays?
Best regards,
Kaja
