The Reliability Test Methods of Printed Circuit Board (PCB) Quality
PCB plays an important role in today's life. It is the foundation of electronic components. In this regard, the quality of the PCB is very critical. To check the quality of the PCB, the following reliability tests must be carried out.
1. Ion contamination test
Purpose: Check the number of ions on the surface of the circuit board to determine whether the cleanliness of the circuit board is qualified.
Method: Use 75% propanol to clean the surface of the sample. Ions can be dissolved in propanol, thereby changing its conductivity. The change in conductivity is recorded to determine the ion concentration.
Standard: less than or equal to 6.45ug.
2. Chemical resistance test of solder mask
Purpose: To check the chemical resistance of the solder mask
Method: Drop dichloromethane on the surface of the sample. After a while, wipe the methylene chloride with white cotton. Check whether the cotton is stained and the solder mask is dissolved.
Standard: No dye or dissolution.
3. Hardness test of solder mask
Purpose: To check the hardness of the solder mask
Method: Place the circuit board on a flat surface. Use a standard test pen to scratch a certain range of hardness on the boat until there are no scratches. Record the minimum hardness of the pencil.
Standard: The minimum hardness should be higher than 6H.
4. Stripping strength test
Purpose: Check the force that can strip the copper wire on the circuit board
Equipment: Peel strength tester
Method: Strip the copper wire at least 10mm from one side of the substrate. Place the sample plate on the tester. Use vertical force to strip the remaining copper wire. Record power.
Standard: The force should exceed 1.1N/mm.
5. Solderability test
Purpose: To check the solderability of pads and through holes on the board.
Equipment: soldering machine, oven, and timer.
Method: Bake the board in an oven at 105°C for 1 hour. Definitely put the board into the soldering machine at 235°C, and take it out in 3 seconds, inspect the area of the solder pad that is immersed. Put the board vertically into a soldering machine at 235°C, take it out after 3 seconds, and check whether the through-holes are immersed in the tin.
Standard: The area percentage should be greater than 95. All through holes should be immersed in the tin.
6. Withstand voltage test
Purpose: Test the withstand voltage capability of the circuit board.
Equipment: Withstand voltage tester
Method: Clean and dry the sample. Connect the circuit board to the tester. Increase the voltage to 500V DC (direct current) at a speed not higher than 100V/s. Keep it at 500V DC for 30 seconds.
Standard: There should be no faults on the circuit.
7. Glass transition temperature test
Purpose: To check the glass transition temperature of the board.
Equipment: DSC (differential scanning calorimeter) tester, oven, dryer, electronic scale.
Method: Prepare the sample, its weight should be 15-25mg. The sample was baked in an oven at 105°C for 2 hours and then placed in a desiccator to cool to room temperature. Place the sample on the sample stage of the DSC tester, and set the heating rate to 20°C/min. Scan 2 times and record Tg.
Standard: Tg should be higher than 150℃.
8. CTE (Coefficient of Thermal Expansion) Test
Goal: evaluate the CTE of the board.
Equipment: TMA (Thermal Mechanical Analysis) tester, oven, dryer.
Method: Prepare a sample with a size of 6.35 * 6.35mm. The sample was baked in an oven at 105°C for 2 hours and then placed in a desiccator to cool to room temperature. Put the sample on the sample stage of the TMA tester, set the heating rate to 10°C/min, and set the final temperature to 250°C to record the CTE.
9. Heat resistance test
Purpose: To evaluate the heat resistance of the board.
Equipment: TMA (Thermal Mechanical Analysis) tester, oven, dryer.
Method: Prepare a sample with a size of 6.35 * 6.35mm. The sample was baked in an oven at 105°C for 2 hours and then placed in a desiccator to cool to room temperature. Put the sample on the sample stage of the TMA tester, and set the heating rate to 10°C/min. The sample temperature was increased to 260°C.
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