The causes and Countermeasures of printing defects when printing solder paste by solder paste printer are the following seven points (tin lapping problem, cortical problem, too many paste stars, insufficient problem, insufficient problem, insufficient adhesion problem, collapse problem and fuzzy problem):

Reasons: small amount of tin powder, low viscosity, large particle size, room temperature, too thick printing paste, too high placement pressure, etc. (usually, when there is a little paste between the two welding pads, it will often be pulled back by the main tin body on each pad during high-temperature fusion welding. Once it cannot be pulled back, it will cause a short circuit to form a Capricorn ball, which is very dangerous to the fine spacing).

Countermeasures:

1. Increase the proportion of metal components in solder paste (to more than 88%).

2. Increase the viscosity of solder paste (above 700000 CPS)

3. Reduce the particle size of tin powder (for example, from 200 mesh to 300 mesh)

4. Reduce the ambient temperature (below 27oc)

5. Reduce the thickness of the printed solder paste (reduce to the overhead height snap-off, reduce the scraper pressure and speed)

6. Strengthen the essence of printing paste? Accuracy.

7. Adjust various construction parameters of printing paste

8. Reduce the pressure exerted by parts placement.

9. Adjust the temperature curve of preheating and fusion welding.

2、 Cortical burst problem:

Reason: because the activator in the solder paste flux printed by the solder paste printer is too strong, the ambient temperature is too high and there are too many lead stars, it will cause the oxide layer on the outer layer of the particles to peel off.

Countermeasures:

1. Avoid exposing the solder paste to moisture.

2. Reduce the activity of flux in solder paste.

3. Reduce the lead content in the metal.

3、 Too much solder paste after printing by solder paste printer:

Reason: similar to "bridging"

Countermeasures:

1. Reduce the thickness of the printed solder paste.

2. Improve the accuracy of printing.

3. Adjust the parameters of solder paste printing.

4、 Insufficient solder paste after printing by solder paste printer:

Cause: it occurs during steel plate printing, which may be caused by too thick wire diameter of mesh cloth, too thin plate film, etc

Countermeasures:

1. Increase the thickness of printing paste, such as changing mesh or plate film

2. Improve the accuracy of printing.

3. Adjust the parameters of solder paste printing.

5、 Insufficient adhesion of solder paste after printing solder paste by solder paste printer:

Cause: high ambient temperature and high wind speed cause too much solvent loss in solder paste and too large particle size of tin powder Conditions to eliminate solvent escape (such as reducing room temperature, reducing blowing, etc.).

Countermeasures:

Reduce the percentage of metal content.

Reduce the viscosity of solder paste.

Reduce the particle size of solder paste.

Adjust the distribution of solder paste particle size.

6、 Collapse after solder paste printing:

Reason: similar to "bridging".

Countermeasures:

1. Increase the metal content percentage in the solder paste.

2. Increase the viscosity of solder paste.

3. Reduce the particle size of solder paste.

4. Reduce the ambient temperature.

5. Reduce the thickness of printing paste.

6. Reduce the pressure exerted by parts placement.

7、 Solder paste blur after printing solder paste by solder paste printer:

Cause: the cause of formation is very similar to bridging or collapse, but there are many reasons for poor printing construction, such as too much pressure, insufficient overhead height, etc.

Countermeasures:

Increase the percentage of metal content.

Increase the paste viscosity.

Adjust the ambient temperature.

Adjust the parameters of solder paste printing.