What Are the Common Defects in Solder Paste Printing?
2024-08-27 17:06
I. Diagnosis and Handling of Solder Bridging
1.Phenomenon Description: A small amount of solder paste overlaps between two pads. During high-temperature soldering, this overlapping solder paste is usually pulled back by the main solder mass on each pad. If it fails to be pulled back, it will cause solder balls or circuit short circuits, leading to poor soldering.
2.Diagnosis of Solder Bridging: Insufficient solder powder content, low solder powder viscosity, improper solder powder particle size, high room temperature, excessive printing thickness, and high placement pressure.
3.Handling of Solder Bridging:
a. Increase the proportion of metal components in the solder paste to enhance its viscosity.
b. Reduce the solder powder particle size and lower the ambient temperature.
c. Decrease the thickness of the printed solder paste.
d. Improve the precision of solder paste printing.
e. Adjust various process parameters for solder paste application.
f. Reduce the pressure applied during component placement.
g. Adjust the preheating and soldering temperature profiles.
II. Diagnosis and Handling of Solder Paste Smearing
1.Phenomenon Description: After printing, there are burrs or excess solder paste around the printed solder paste.
2.Diagnosis of Solder Paste Smearing: Insufficient squeegee pressure, too small squeegee angle, excessively large stencil aperture, mismatched PCB and PAD sizes, misaligned printing, incorrect printer parameter settings, poor adhesion between the stencil and PCB, insufficient solder paste viscosity, and contamination on the bottom of the PCB or stencil.
3.Handling of Solder Paste Smearing:
a. Adjust the parameters of the solder paste printer.
b. Clean or replace the stencil.
c. Clean or replace the PCB.
d. Improve the precision of the printer.
e. Increase the viscosity of the solder paste.
III. Diagnosis and Handling of Solder Paste Collapse and Powdering
1.Phenomenon Description: Poor forming of solder paste on the PCB (uneven printing height) and powdering of the solder paste.
2.Diagnosis of Solder Paste Collapse and Powdering: Excessive solvent in the solder paste, excessive solvent used when wiping the bottom of the stencil (causing the solder paste to dissolve in the solvent), non-rotating wiping paper, poor solder paste quality, prolonged exposure of the PCB to air after printing, and excessively high PCB temperature.
3.Handling of Solder Paste Collapse and Powdering:
a. Increase the proportion of metal components in the solder paste to enhance its viscosity.
b. Reduce the solder powder particle size and lower the ambient temperature.
c. Decrease the thickness of the printed solder paste and improve the printing precision.
d. Adjust various process parameters for solder paste application.
e. Reduce the pressure applied during component placement.
f. Avoid prolonged exposure of the solder paste and printed PCBs to humid air.
g. Reduce the activity of the flux in the solder paste.
h. Decrease the lead content in the metal component.
IV. Diagnosis and Handling of Solder Paste Tailing
1.Phenomenon Description: Poor forming of solder paste on the PCB, excessively large smearing area, and too small spacing between solder joints.
2.Diagnosis of Solder Paste Tailing: Uneven stencil apertures, excessively small stencil aperture size, unreasonable stencil separation speed, contaminated PCB solder joints, abnormal solder paste quality, and incomplete stencil cleaning.
3.Handling of Solder Paste Tailing:
a. Clean or replace the stencil.
b. Clean or replace the PCB.
c. Adjust the printing parameters.
d. Replace with solder paste of better quality.
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