The lead-free solder paste must first be able to truly meet the environmental protection requirements, and the lead cannot be removed, and new toxic or harmful substances are added; the solderability and post-soldering reliability of the lead-free solder must be ensured, and customers must be considered. costs and many other issues. In summary, lead-free solders should try to meet the following requirements:

Lead-free solder should have good wettability; under normal circumstances, the time the solder stays above the liquidus line during reflow soldering is 30-90 seconds. During wave soldering, the soldered pins and circuit board substrate surface and tin liquid The contact time of the wave peak is about 4 seconds. After using lead-free solder, it is necessary to ensure that the solder can show good wetting performance within the above time range to ensure high-quality soldering effect; the melting point of lead-free solder should be as low as possible. The eutectic temperature of 63/37 tin-lead alloy is close to 1830C. If the eutectic temperature of the new product is only a few degrees higher than 1830C, it should not be a big problem. The minimum solidus temperature is 1500C, and the liquidus temperature depends on the specific application (tin bar for wave soldering: below 2650C; tin wire: below 3750C; solder paste for SMT: below 2500C, usually the reflow soldering temperature should be lower than 225 - 2300C).

Solder bubble complete solution

1. Choose a relatively high-quality solder paste.

2. Pay attention to the printing speed and angle adjustment of the printing machine.

3. Reflow soldering preheating zone 160-190 should be around 90 seconds as much as possible.

If the above still doesn't work, there is another way to make a sample.

1. Pre-tin the PCB pad with solder wire and soldering iron, and then level it.

2. Normal operation.

3. Check if the bubbles disappear.

Tried more than 90% of the bubbles will reduce or even disappear, which can meet the bubble area requirement of less than 20% of DELL.

What are the differences between solid die solder paste and ordinary solder paste?

1. It is tin powder: choose No. 5 or No. 6 powder with very small particles.

2. Packaging: Most of the packaging is 30ml or 10ml syringe packaging.

3. Function: It is mainly used to replace the silver glue welding core.

4. The lead-free solder paste fully meets the environmental protection standards such as RoHS and halogen-free, and is used for LED chip packaging and other The encapsulation of power devices such as diodes can achieve fusion between metals, which can greatly reduce the thermal resistance of the LED heat dissipation channel, while achieving better conductivity and connection strength.