A mesh-capable LoRa® data radio with support for AT commands & MODBUS

Oct 14, 2020

Project update 3 of 3

Working Toward Production

by Sramrajkar

In the last few days, we have been concentrating on getting our production and logistics in place and tested. To do so, we comissioned a 12 unit pilot batch with our selected design house "All PCB".

LoMesh PCB panel

The boards arrived back at our labs where we tested them thoroughly. Testing yielded the following observations:

  1. Initial yield was 8/12 boards. Of the failed boards all the errors we found were solder bridges on the radio. All other components were working well on all boards.
  2. Of the four boards that failed, two were fixed by hand and restored to working condition. Two were damaged while attempting repair. Hence the total yield was 10/12 boards.
  3. This issue was promptly communicated to the fabrication house and they acknowledged the issues.
  4. The pilot batch had no end of line test plan in place. If a test plan had already been in place, all the errors found in the pilot batch would be detected in the factory, where they should be able to fix issues before shipping.
  5. One other issue identified was that the boards were shipped in panels. This was also communicated to the PCB fabrication house. In the future the boards will be shipped as individual PCBs. You can see a picture of the PCB panel below.

Here is a picture of fully assembled board along with the new antenna that was used during module FCC certification.

LoMesh with production antenna

Overall, the quality of PCB assembly is acceptable. With a good end of line test plan in place, the production yield should be near 100%. In the days to come we will be working on implementing a solid end of line test plan. We’ll need to add some code to help with this EOL testing.

We are also developing stress tests for the devices. For this, we’ve written Node-Red scripts with Dashboard that can perform long-term stress tests.

All in all, between now and product fabrication, we should be in a good place to produce and deliver quality product.

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