PCB News - What is the PCBA stress test and PCBA defect repair process?

1. What are the principle steps of PCBA stress testing?

There are many steps in PCBA processing, so let's introduce the principle and steps of PCBA stress test?

Firstly, the strain gauges are attached to several different positions of the PCB. During the process or station operation, the strain gauges are connected to the measuring instrument system so that the stress can be quantitatively displayed and recorded.

Namely: strain-resistance change-voltage (or current) change-amplification-recording-data processing

PCBA processing-what are the principle steps of PCBA stress testing?

1. Select strain gauge

Strain gauge is a sensor that can linearly change the resistance value according to the magnitude of the stress. When the strain gauge is deformed, the resistance value will change accordingly.

2. Paste the strain gauge

Select the PCBA mounting board according to the process to be tested, and select the test point on the PCB to paste the strain gauge according to the position of the stress. If there is not enough space to stick the strain gauges on the board, you have to remove the parts that have been fixed on the board to make room. Pay attention to the specific bond gauge required by the strain gauge. Generally speaking, at least two to three PCBAs to be tested are required to be installed and tested to prove the correctness and consistency of the test.

3. Measure strain

Connect the lead of the strain gauge to the data acquisition instrument of the test system, adjust the scan frequency (also called sampling rate), sampling resolution, gain setting, excitation voltage, number of channels and other parameters, and run the test program to determine the length of the test time Variable, generally can run for 5-10 seconds and record data.

For the PCBA board strain test, the recommended scanning frequency range is 500Hz-2kHz, and generally try to choose a higher frequency to capture the instantaneous stress change.

4. Analyze and record data

Analyze the collected strain data, calculate the stress (maximum stress and minimum stress) experienced by the PCBA during the test, and record all the data.

2. What is the repair process for defective PCBA boards?

In the PCBA production process, due to improper operation of the production personnel or due to the quality of the materials, defective PCBA boards often appear, and the defective PCBA boards need to be repaired at this time.

PCBA board-PCBA repair process

The PCBA repair process is:

Visually inspect PCBA - measure all POWER - poor power-on test - repair according to the bad phenomenon - self-inspection after repair - test fixture test - visual inspection full inspection

The tools that need to be prepared for PCBA repair are: oscilloscope, digital meter, constant temperature soldering iron, hot air gun, needle-nose pliers, diagonal pliers, tweezers.

PCBA repair process-PCBA board repair process

1. Visual inspection PCBA

Mainly check PCBA for obvious appearance defects. Such as: short circuit, empty welding, missing parts, extremely reversed components, burnt out of wrong components, etc.

2. Measure all POWER

Mainly measure whether the power supply has a short circuit to the ground

3. Poor power-on test

DOUBLE CHECK is bad using the test fixture after power-on

4. Repair according to bad phenomena

Perform repairs based on bad phenomena and circuit principles. You can refer to the engineering to provide repair work instructions

5. Self-check after maintenance

After repairing, self-inspection is required for the repaired part. Main inspections: short circuit, empty solder, tin bead, tin slag, and appearance of solder joints

6. Test fixture test

Use the test fixture to check whether the PCBA is repaired or not

7. Visual inspection and full inspection

Fully inspect the repaired product

The role of PCBA defective board repair is to reduce the scrap of the board and reduce the production cost of the PCB factory by repairing the defective PCBA board.