PCB circuit boards play an important role in today's life. It is the foundation and highway of electronic components. In this regard, the quality of the PCB is critical. To check the quality of the PCB, several reliability tests must be performed. The following paragraphs are an introduction to the test.
1. Ion contamination test
Purpose: To check the number of ions on the surface of the circuit board to determine whether the cleanliness of the circuit board is acceptable.
Method: Use 75% propanol to clean the sample surface. Ions can dissolve into propanol, changing its conductivity. The change in conductivity was recorded to determine the ion concentration.
Standard: Less than or equal to 6.45ug.NaCl/sq.in
2. Chemical resistance test of solder mask
Purpose: To check the chemical resistance of the solder mask
Method: drop qs (quantum satisfactory) dichloromethane on the surface of the sample. After a while, wipe the methylene chloride with a white cotton. Check to see if the cotton is dyed and if the solder mask has dissolved. Standard: No dye or dissolve.
3. Hardness test of solder mask
Purpose: To check the hardness of the solder mask
Method: Place the circuit board on a flat surface. Scratch a range of hardness on the boat with a standard test pen 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: To check the force that can strip the copper wire on the circuit board
Equipment: Peel Strength Tester
Method: Strip at least 10mm of copper wire from one side of the substrate. Place the sample plate on the tester. Strip the remaining copper wire using vertical force. Record power. Standard: The force should exceed 1.1N/mm.
5. Solderability test
Purpose: To check solderability of pads and vias on the board.
Equipment: Soldering machine, oven and timer.
Method: Bake the board in an oven at 105°C for 1 hour. Dip Flux. Put the board flatly into the solder machine at 235°C, and after 3 seconds, inspect the area of the pads that are immersed in tin. Put the board vertically into a soldering machine at 235°C, take it out after 3 seconds, and check whether the through hole is immersed in tin. Standard: Area percentage should be greater than 95. All through holes should be tin immersed.
6. Withstand voltage test
Purpose: To test the withstand voltage capability of the circuit board.
Equipment: Withstand Voltage Tester
Method: Clean and dry samples. Connect the board to the tester. Increase the voltage to 500V DC (direct current) at a rate no higher than 100V/s. Hold it at 500V DC for 30 seconds. Standard: There should be no fault on the circuit.
7. Glass transition temperature test
Purpose: To check the glass transition temperature of the plate.
Equipment: DSC (Differential Scanning Calorimeter) tester, oven, dryer, electronic scale.
Method: Prepare the sample, its weight should be 15-25mg. The samples were 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
Target: CTE of the evaluation board.
Equipment: TMA (Thermo-Mechanical Analysis) Tester, Oven, Dryer.
Method: Prepare a sample with a size of 6.35*6.35mm. The samples were 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 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 thermal resistance of the board.
Equipment: TMA (Thermo-Mechanical Analysis) Tester, Oven, Dryer.
Method: Prepare a sample with a size of 6.35*6.35mm. The samples were 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 TMA tester and set the heating rate to 10 °C/min. The sample temperature was raised to 260°C.
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