Common PCB quality inspection’s diagnosis and treatment

- May 21, 2019-

1) Diagnosis and treatment of tinning

(1) Phenomenon description: There is a little paste between the two welding pads. When welding at high temperatures, it is often pulled back by the main tin body on each welding pad. Once it cannot be pulled back, it will cause short circuit or solder ball, resulting in defective soldering.

(2) Diagnostic tinning: less amount of tin powder, low tin powder viscosity, large tin powder particle size, high room temperature, too thick printing, and high pressure.

(3) tin treatment: increase the proportion of metal components in the solder paste; increase the viscosity of the solder paste; reduce the particle size of the tin powder; reduce the environment temperature (below 270 ° C): reduce the thickness of the printed solder paste (fall to overhead) Height, reduce the pressure and speed of the auxiliary blade): strengthen

The accuracy of the paste; adjust the various construction parameters of the solder paste; reduce the pressure applied by the placement of the parts; adjust the temperature curve of the preheating and fusion welding.

 

2) Diagnosis and treatment of tin infiltration

(1) Phenomenon description: After printing finish, there is excess solder paste or burrs near the solder paste.

(2) Dialysis of tin infiltration: insufficient blade pressure, too small blade angle, too large opening of the steel plate, too small PCB and PAD size, misaligned printing, unreasonable setting of printing machine parameters, and untight bonding between PCB and steel plate. The solder paste has insufficient viscosity and the bottom of the PCB or steel plate is not clean.

(3) Tin infiltration treatment: adjust the parameters of solder paste printing; clean or replace the template, clean or replace the PCB; improve the printing accuracy; improve the viscosity of the solder paste.

 

3)Diagnosis and treatment of powder paste collapsed by solder paste

(1) Phenomenon description: The solder paste is poorly formed on the PCB, the printing height is different, and the solder paste is in the form of powder and granularity.

(2) Solder paste collapse solder paste powder diagnosis: too much solvent in the solder paste, too much solvent when the bottom of the steel plate is wiped, the solder paste is dissolved in the solvent, the wiper paper does not rotate, the solder paste quality is poor, and the printed PCB placed in the air for a long time, the PCB temperature is too high, and so on.

(3) solder paste collapse solder paste powder treatment: increase the proportion of metal components in solder paste; increase the viscosity of tin paste; reduce the particle size of tin powder; reduce the environment temperature (below 270 ° C); reduce the printed solder paste thickness (falling to overhead height, reducing blade pressure and speed); enhancing the accuracy of the paste; adjusting various construction parameters of the solder paste; reducing the pressure applied by the placement of the parts; avoiding the solder paste and the printed PCB in the air for a long time; reduce the activity of flux in the solder paste; reduce the lead content in the metal.

 

4) Diagnosis and treatment of solder paste tip

(1) Phenomenon description: The solder paste is poorly formed on the PCB, the smear area is too large, and the solder joint pitch is too small.

(2) Solder paste tip diagnosis: the steel plate opening is not smooth, the steel plate opening size is too small, the demoulding speed is unreasonable, the PCB solder joint is contaminated, the solder paste quality is abnormal, and the example plate is not cleaned.

(3) Solder paste tipping treatment: cleaning or replacing the steel plate and the PCB; adjusting the printing parameters; replacing the solder paste with better quality.

 

5) Diagnosis and treatment of less tin

(1) Phenomenon description: The amount of solder paste on the PCB is insufficient.

(2) Diagnosis of less tin: Unreasonable opening size of steel plate, too thin plate mold, steel plate plug hole, steel plate pollution, demoulding speed and unreasonable method.

(3) Less tin treatment: increase the thickness of the paste, such as cleaning or replacing the template; adjust the printing parameters; improve the accuracy of printing.

 

6) Diagnosis and treatment of excessive tin

(1) Phenomenon description: The amount of solder paste on the PCB pad is excessive.

(2)Excessive tin diagnosis: the opening size of the steel plate is unreasonable, the plate mold is too thick, the room temperature is high, the printing is too thick, and the placing pressure is large.

(3) Excessive tin treatment: select the appropriate opening form; reduce the thickness of the paste; adjust the printing parameters; improve the accuracy of printing.

 

7) Diagnosis and processing of offset

(1) Phenomenon description: The printed solder paste deviates from the welding pad on the PCB.

(2) Offset diagnosis: the position of the steel plate opening is unreasonable, and the PCB positioning is not accurate.

(3) Offset processing: re-adjust the printing position of the PCB, replace the template, and improve the printing accuracy.

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