Ten Reliability Tests of PCB

Reliability test flow of PCB board
In order to ensure the reliability of PCB, it must go through a series of rigorous tests. The following are some common test methods and standards:


A, ion pollution test

Objective: To evaluate the cleanliness of the board surface and ensure that the ion pollution is within the acceptable range.

Principle: By measuring the change of solution conductivity, the number of ions can be indirectly reflected.

Methods: The sample was washed with 75% isopropanol solution for 15 minutes, and the change of conductivity was observed.

Standard: the ion pollution shall not exceed 6.45ug NaCl/sq.in

Second, the curing test

Objective: To test the chemical stability of solder mask and characters.

Material: dichloromethane.

Methods: After dripping dichloromethane, wipe it with cotton cloth and observe the change.

Standard: cotton cloth does not stick to solder mask or characters, and the board surface does not dissolve or change color.

Third, the thermal stress test

Objective: To evaluate the high temperature resistance of substrate and copper layer.

Equipment: constant temperature tin furnace, oven, etc.

Methods: After high temperature baking and tin surface floating test.

Standard: no delamination, white spots, solder mask falling off, no fracture or cavity in copper layer and base material.

Fourth, solderability test

Objective: To test the welding quality of surface conductors and through holes of printed boards.

Equipment: constant temperature tin furnace, oven.

Methods: Bake the board, dip in flux, swing the tin surface and test vertically.

Standard: The wetted area of SMT pad is at least 95%, and the through hole is completely wetted.

Five, PCB peeling test

Objective: To measure the peeling strength of printed circuit board wires.

Equipment: peeling strength tester.

Methods: The sample was fixed, and the wires were peeled off by uniform tension.

Standard: The peeling strength of conductor shall not be less than 1.1n/mm..

Six, solder mask hardness test

Objective: To measure the hardness of solder mask and ensure its wear resistance.

Test pencil: from 4B (softest) to 6H (hardest)

Method:

(1) Place the board on a firm horizontal surface.

(2) First, put the hardest test pencil on the solder mask, make an angle of 45 degrees, add 10N force, and push forward reversely. (3) Make the pencil move forward for 1/4 "at a uniform speed on the solder resist layer, leaving a scratch on the coating. (4) Continue to test with the next soft pencil until there is no scratch. When there are no scratches on the solder mask, the hardness of the pencil is the test result, and the minimum pencil hardness is 6 hours.

Seven, withstand voltage test

Objective: To evaluate the insulation performance and voltage resistance of PCB.

Equipment: voltage withstand tester

Method:

(1) Wash and dry the sample to be tested properly. (2) Connect the+/-terminals of the withstand voltage tester to one end of the conductor to be tested. (3) The voltage value of the withstand voltage tester is increased from 0V to 500VDC, and the boosting rate is not more than 100V/s.. (4) Under the action of 500VDC, the duration is 30s.

Standard: During the test, there should be no arc or discharge between insulation medium or conductor spacing.

Eight, Tg test

Objective: To determine the glass transition temperature (Tg) of PCB by DSC.

Equipment: DSC tester, electronic balance, oven and dryer.

Method:

(1) sampling and polishing the edge of the sample, and controlling the weight of the sample between 15 and 25 mg.

(2) Bake the sample to be tested in an oven at 105°C for 2 hours, take it out and put it in a dryer to cool it to room temperature for at least 30 minutes.

(3) Place the sample on the sample table of DSC, set the heating rate at 20 C/min, and the scanning termination temperature depends on the Tg result of the sample.

The scanning was repeated twice, and the glass transition temperatures Tg and △Tg were obtained from the obtained heat flow curve by Universal Analysis software.

Nine, CTE test

Objective: To measure the coefficient of thermal expansion (CTE) of PCB and evaluate its stability under temperature changes.

Equipment: TMA tester, oven and dryer.

Method:

(1) Sampling and polishing the edge of the sample, with the sample size of 6.35*6.35mm.

(2) Bake the sample to be tested in an oven at 105°C for 2 hours, take it out and put it in a dryer to cool it to room temperature for at least 30 minutes.

(3) Place the sample on the sample table of TMA, set the heating rate at 10 C/min and the scanning end temperature at 250 C..

(4) From the obtained heat flow curve, the CTE of the plate before and after the Tg point is obtained by using Universal Analysis software.

Ten. Burst plate test

Objective: To evaluate the heat resistance of PCB substrate at high temperature.

Equipment: TMA tester, oven and dryer.

Method:

(1) Sampling and polishing the edge of the sample, the sample size is 6.35*6.35mm.

(2) Bake the sample to be tested in an oven at 105°C for 2 hours, take it out and put it in a dryer to cool it to room temperature for at least 30 minutes.

(3) Place the sample on the sample table of TMA, set the probe pressure to 0.005N and the heating rate to 10 C/min.

(4) Raise the sample temperature to 260 C..

(5) When the temperature rises to 260°C, keep this temperature for 60 minutes, or stop scanning until the test fails. When obvious stratification occurs, scanning can be stopped.

(6) The burst time is defined as the time from constant temperature to obvious delamination. Record this time.

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