Why does the grape ball phenomenon occur in smt reflow soldering?

GenerallysmtPart of the reflow soldering process during the surface mount technology (SMT) processingSolder pasteInstead of completely melting, they are welded together to form individual tin beads or tin balls stacked together, creating a phenomenon similar to bunches of grapes. Now, JJY solder Paste Manufacturer will take you to understand the main causes of grape ball formation and the preventive measures:

I. Main Causes of Possible grape ball phenomenon

1Premature evaporation of flux in solder paste: The flux in solder paste is the main factor affecting the performance of solder paste. Its primary function is to remove surface oxides of metals. In fact, it has another function, which is to wrap the solder paste and prevent it from coming into direct contact with air before soldering. If the flux evaporates prematurely and cannot remove surface oxides, and the solder paste comes into direct contact with air, it will cause poor soldering. In addition, excessive preheating time during reflow soldering can also cause the flux to evaporate prematurely. Therefore, it is necessary to control the preheating time reasonably.

2Excessive humidity causes the solder paste to get damp and oxidize

The oxidation of solder paste is the main cause of the grape ball phenomenon. There are many reasons for the oxidation of solder paste, such as high humidity in the workshop environment, improper operation of solder paste by workers, expired or improperly stored solder paste, and failure to warm up and stir solder paste, etc. All these reasons can cause the solder paste to get damp and thus affect the quality of soldering.

Ii. Methods to Avoid the Phenomenon of grape balls

1Reasonably prevent the solder paste from getting damp and oxidizing.

2Give priority to choosing high-quality solder paste with high activity and strong antioxidant capacity.

3Reasonably control the preheating time of reflow soldering to reduce the premature evaporation of flux.

4Appropriately increasing the amount of solder paste printed and the thickness of the holes in the steel mesh can reduce the oxidation of the solder paste during printing.

Shenzhen JJY Industrial Technology Co., Ltd. mainly produces and operates: lead-free solder paste, lead-free high-temperature solder paste, lead-free medium-temperature solder paste, lead-free low-temperature solder paste, etc. If you have any needs, please feel free to contact us.