How can one generally identify the environmental friendliness of lead-free solder paste?

Generally, when we are identifying lead-free solder paste, in fact, solder paste contains many different components, namely: tin-copper alloy, tin-bismuth alloy (low-temperature?139Therefore, many customers do not know which one to choose when selecting products that can be soldered according to their own products. A better solder alloy is tin-lead alloy63/37Lead-free solder alloys are currently better for electronic products, but they also have a relatively high cost performance. Therefore, many customers cannot accept them. Now, the solder paste manufacturer will tell you how to determine whether lead-free solder paste is suitable or not?

1. Evaluate it after printing. If there are five kinds of defects in solder paste printing:Bridging, skinning, insufficient adhesion, collapse and blurriness can be identified in terms of the solder paste itself, apart from its own operational issues:

1Bridging, collapse, blurring and uneven proportions of metal components in solder paste;The viscosity is insufficient and the tin powder particles are too large.

2 The appearance of a skin layer indicates that the activity of the solder paste in the solder paste is too strong. If there is lead solder paste, its lead content may be too high.

3Insufficient adhesion might be due to the fact that the solvent in the solder paste is prone to evaporation, the metal proportion in the solder paste is too high, or the particle size does not match.

 Second, after welding, there should be no functional defects on the appearance. Most functional defects are caused by technical problems or operational issues. Generally speaking, since there are fewer defects in solder paste, the appearance mainly depends on whether there are residues after soldering. Are there any tin beads on the surface?Will it corrode the surface of the circuit board?

    In addition, we should also consider the application environment of lead-free solder paste, as using it in an unsuitable environment can cause adverse reactions to the lead-free solder paste. Therefore, we should choose the appropriate environment.

    The application environment of lead-free solder paste generally has the following requirements:

1After the solder paste is printed, it should be refilled within four hours. If the storage time is too long, the solvent will evaporate and the viscosity will decrease, which will lead to poor weldability of the parts or cause welding requirements after moisture absorption. Especially for circuit boards with silver conductors, if at room temperature30℃Humidity80%Under such conditions, when printing solder paste and then setting it aside, the soldering force after reflow will become very low.

2Solder paste can be affected by humidity and temperature, so it is recommended that the working environment be at room temperature23-25Degree, humidity is60%. The viscosity of the solder paste can be adjusted to23to25The appropriate viscosity between degrees. Therefore, if the temperature is too high, the viscosity will be too low, and if the temperature is too low, the viscosity will be too high. As a result, the desired effect cannot be achieved after printing. Due to the hygroscopic effect of solder paste, it will absorb moisture from the air in a high-temperature and humid environment, resulting in solder balls and spatter.

3If the solder paste is blown away by the wind, the solvent will evaporate, which will reduce the viscosity and cause the shell to open. Try to avoid using the electric fan of the air conditioner to blow solder paste directly.

The above is what I have told you allLead-free solder pasteHow to choose the right product for yourself? I hope this is useful to everyone. If you want to learn more about soldering, please continue to follow JJY Solder Paste Factory and leave a message online to interact with us.