Flextronics BBU Power Supply Manufacturing: A Step-by-Step Guide

1. ICT (In-Circuit Test)

Purpose: To check the integrity of the BBU’s circuits, detecting issues like shorts, opens, or faulty components.

Explanation:

• The ICT system checks for faults that may have occurred during soldering or component placement.
• The unit is placed into a fixture, which makes contact with various points on the board, such as vias, pins, or pads. A series of tests are run to verify if the circuits are intact.

Tools/Software:

• Test System: Keysight 3070, Teradyne ICT, or other similar platforms.
• Command: Load the test plan file that contains the testing sequence for the specific board being tested.
  For example, in Keysight 3070:
  load testplan.bbu

Procedure:

1. Load the BBU unit onto the ICT fixture.
2. Initiate the test through the software interface.
3. Monitor the results. A "PASS" indicates the unit is free from major circuit faults; a "FAIL" prompts inspection of error codes (e.g., "IC U7 pin 14 open").

2. BMS Programming

Purpose: To flash the Battery Management System (BMS) firmware onto the unit’s memory.

Explanation:

• The BMS is crucial for monitoring battery health and ensuring safety during charging and discharging.
• This step involves programming the unit with the necessary software that controls its functions.

Tools/Software:

• Programming Software: SEGGER J-Link, STM32CubeProgrammer.
• Command Example (STM32CubeProgrammer CLI):
  STM32_Programmer_CLI.exe -c port=SWD -w BMS_Firmware_V3.4.hex -v

Procedure:

1. Connect the BMS to the programmer via JTAG or SWD.
2. Open the STM32CubeProgrammer tool.
3. Load the correct firmware for the BMS.
4. Flash the firmware by running the command above.
5. Verify that the checksum matches after flashing.

3. ACT BMS

Purpose: To test the Battery Management System (BMS) in an active test environment.

Explanation:

• The BMS must be tested in real-world conditions to ensure it monitors battery voltage, temperature, and current properly.

Procedure:

1. Mount the BMS onto a test fixture with a battery simulator.
2. Launch diagnostic software (e.g., LabVIEW) to monitor outputs from the BMS.
3. Check the voltage, current, and temperature readings against expected values:
   • Voltage: 11.1V to 13.0V.
   • Temperature: 25°C to 45°C.
4. Record the data for traceability and to ensure the unit operates within spec.

4. ACT DSP (Digital Signal Processor)

Purpose: To program and verify the DSP used in power management and communication functions.

Explanation:

• The DSP is responsible for processing signals related to power conversion, communication, and monitoring of the system.
• In this step, the DSP is programmed with the firmware and tested for proper signal handling.

Tools:

• Software: Code Composer Studio, TI Flash Programmer.

Procedure:

1. Connect the DSP via JTAG interface.
2. Open Code Composer Studio and load the appropriate DSP firmware (e.g., DSP_Main.hex).
3. Program the DSP with the software.
4. Test the DSP’s output using communication protocols (e.g., UART, CAN).

Command Example:
dslite --config=ccxml_file --program DSP_Main.hex --verify

5. ACT Fixture Assembly

Purpose: To assemble all the active components (BMS, DSP, etc.) into a fixture for further testing.

Explanation:

• This step involves physically assembling the test fixtures, wiring, and other components needed to run subsequent tests.

Procedure:

1. Place the BMS, DSP, and other necessary components into their designated slots within the fixture.
2. Use a torque screwdriver to secure the components, ensuring that no components are loose.
3. Perform a final visual check to ensure everything is aligned and properly seated.

6. Power ACT

Purpose: To supply power to the fixture and ensure all components receive the correct voltage.

Explanation:

• This step is critical to verify that the system boots up correctly and that there are no power issues that could affect later stages.

Procedure:

1. Connect a DC power supply (e.g., 12V at 5A) to the test fixture.
2. Observe the system’s boot process, including LED indicators or console outputs.
3. Measure the current drawn by the unit and verify it stays within expected limits (e.g., ~300mA idle).

7. BI Fixture Assembly (Burn-In)

Purpose: To stress-test the unit under controlled conditions to identify early-life failures.

Explanation:

• Burn-in is crucial for eliminating units that fail under continuous operation.
• The unit is placed in a burn-in fixture that applies power and simulates load conditions.

Procedure:

1. Place the unit in the burn-in fixture with necessary connections (AC input, battery simulators).
2. Run the unit for several hours (typically 6–24 hours) under controlled conditions, including monitoring temperature, power, and communication.
3. Log data for traceability.

8. ACT Power Converter

Purpose: To program and test the power converter functionality.

Explanation:

• Power converters (DC-DC converters) are crucial for regulating the power supplied to the battery.
• This step involves ensuring the power converter’s voltage and current outputs are correct.

Procedure:

1. Connect the power converter to a PC using a PMBus interface.
2. Use the PMBus GUI software to load the configuration settings (e.g., 12.4V output).
3. Command Example:
   write_register 0x20 VOUT_COMMAND 0xC4 (to set 12.4V).
4. Use a multimeter to verify the output matches the expected voltage.

9. Burn-In

Purpose: To stress-test the unit under load for prolonged periods.

Explanation:

• This step helps to identify any defects that only occur during prolonged usage.

Procedure:

1. Set the burn-in unit to operate for an extended period (6–24 hours).
2. Ensure the system remains within operational limits, monitoring temperature and voltage.
3. After testing, ensure the unit functions correctly by verifying data and system performance.

10. BI Fixture Disassembly

Purpose: To remove units from the burn-in station.

Procedure:

1. After burn-in testing, power down the burn-in station.
2. Carefully remove the units from the fixture.
3. Inspect for any visible defects such as overheating or physical damage.

11. Box Build 1–7

Purpose: To assemble the BBU into its final enclosure, including attaching necessary components.

Procedure:

1. Assemble the BBU by adding necessary components such as fans, cables, and connectors.
2. Secure all parts according to specifications using the appropriate torque settings.
3. Follow the assembly SOP to ensure proper placement of every component.

12. Pre ATE

Purpose: To perform a final check before the Automated Test Equipment (ATE).

Procedure:

1. Inspect all connections to ensure they are secure and correctly placed.
2. Verify the firmware version and ensure the unit is correctly labelled.

13. Universal Auto Cycle Test 2 (UACT2)

Purpose: To run an automated test that cycles the unit through different power states and checks performance.

Procedure:

1. Insert the unit into the UACT2 station.
2. Let the system run through its test plan, including charging, discharging, and backup simulation.
3. The system logs the results, including any failures.

14. Final ATE

Purpose: To verify that the BBU functions correctly under all test conditions.

Procedure:

1. Connect the unit to the final ATE tester.
2. Run the test plan to check power, communication, and backup performance.
3. Log and evaluate the results.

15. Online Charge

Purpose: To ensure the unit charges properly.

Procedure:

1. Connect the unit to an AC power supply.
2. Ensure the unit charges correctly to 100%.
3. Check the charging LED and verify the system displays the correct charge status.

16. Labelling

Purpose: To label the unit with essential identification information.

Procedure:

1. Print out labels containing the unit’s serial number, MAC address, and firmware version.
2. Attach the labels securely to the unit casing.

17. Final Inspection

Purpose: To ensure the unit is free of defects before packing.

Procedure:

1. Perform a visual inspection to check for missing components or cosmetic damage.
2. Ensure the unit passes the final functionality checks.

18. OBA (Out of Box Audit)

Purpose: To audit random units and ensure they meet quality standards.

Procedure:

1. Open a random sample unit from the packing line.
2. Perform a power test and inspect the unit for any defects.
3. Document any discrepancies and send to QA if necessary.

19. Packing

Purpose: To package the unit for shipment.

Procedure:

1. Place the unit into an anti-static bag.
2. Insert foam protectors to prevent damage during transit.
3. Place the unit in a box with necessary documentation (e.g., user manual, warranty).
4. Scan the unit's barcode and mark it as ready for shipping.

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