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Why choose Lead-free solder in electronic manufacturing?


The size of solder joints in microelectronic devices is getting smaller and smaller, and the mechanical, electrical and thermal loads they bear are getting larger and larger, and the reliability requirements are getting higher and higher. The quality of solder joints determines the quality and reliability of electronic products. Therefore, solder becomes particularly important as the factor affecting the quality of solder joints.

The traditional SnPb solder used in SMT and BGA technologies contains lead. Lead and lead compounds are highly toxic substances, and long-term use will bring great harm to people’s lives and the environment. Lead-free solder is constantly replacing lead-based solder due to its environmental benefits.

What is Lead-free Solder and its composition?

What-is-Lead-free-Solder-and-its-compositionLead-free solder is a solder made of the eutectic phenomenon of tin and other metals such as copper, bismuth, silver and other metals at the eutectic point or non-eutectic point.Lead solder is the original, however lead-free solders are adopted in its stead due to the dangers and safety issues it poses.

Different metals make up a lead-free solder’s composition. But the most common one is the tin-copper lead-free mix. Whose melting point is 217°C and also unique properties which make them differ from ordinary lead tin mixes. A typical lead-free solder has the following composition.

● Zinc
● Copper
● Bismuth
● Antimony
● Nickel
● Silver
● Tin

What’ s the use of Lead-free Solder?

Like normal solder, lead-free solder is also used as a filler metal for PCB soldering, connecting two metals together tightly, but the composition is more harmless. In addition, it can be melted to form slag, which has a protective and metallurgical effect on the molten metal.

What are the properties of lead-free solder?

Properties of lead-free solder are following.What' s the use of Lead-free Solder
● Solder without lead has a melting point of 2170C.
● It does not contain substances that pollute the environment, and the toxicity is small.
● Good mechanical properties, good electrical conductivity and serviceability.
● Lead-free solder has high surface tension.
● Can use existing equipment, has better wettability
● The speed of solder oxidizes is very fast..
● Due to high temperatures, the low dielectric materials are more susceptible to errors.
● Lead-free soldering is also cost effective. It is because of the fact that lead is almost tenth of the price lead.
● Because of the lead-free solder’s poor hydrophilicity, the solder junction performs poorly and inefficiently.
● Lead-free solder has an adverse effect on joint dependability. Additionally, they produce surface oxides and alloy deposits, both of which might lead to subpar substitution of contact resistance.

What’ s the advantage and disadvantage of lead-free solder?

advantage-and-disadvantage-of-lead-free-solder● Advantages:

Lead-free solder is available in sufficient supply and at low cost. Lead-free solder has high working temperature. There are less chances of fatigue. The bond created with a lead-free solder is stronger and a reliable and long-lasting joint is made. It has also enhanced resilience to thermal cycle fatigue. Moreover, when an impurity like silver or copper is added it reduces the chance of whisker formation.After using lead-free solder, it is easier to inspect solder joints.

● Disadvantages:

Its high melting point can cause problems such that the higher melting temperature oxidizes the solder really quickly and can also led to component stress. As compared to lead-solder it’ s cost effective. Therefore, the price of a product rises as tin content does. The delayed wetting is another drawback. Joints frequently function less effectively in terms of automated ability, maximum tensile, and shear capacity.

what’s the difference between lead solder and lead-free solder?

Compared to lead-free solder, lead-based solder is simpler to use, less expensive, and more widely accessible. The toxic nature of lead is a significant disadvantage of utilizing lead solder. Even after even brief, repeated exposures to lead, the human body may begin to accumulate it. It can enter the human body though skin, eyes, nose and mouth. The higher melting temperature of lead make it more challenging to work with.

In addition to the effects on human health, other differences between lead-free and leaded solder include:

1. The ingredients are different
The composition of tin and lead commonly used in lead processing is 63/37, while the composition of lead-free alloy is SAC305, namely Sn: 96.5%, Ag: 3% and Cu: 0.5%. Lead-free processes cannot be absolutely lead-free, but only contain very low levels of lead.

2. The cost is different
Tin is more expensive than lead, so lead-free processing costs much more than lead-free processing.

3. Different melting points
The melting point of lead and tin is 180°~185°, and the working temperature is about 240°~250°. The melting point of lead-free tin is 210°~235°, and the working temperature is 245°~280°. Due to its lower melting point than lead-free solder, lead solder causes fewer quality issues with joins.

4. Different colors
Typically, leaded solder surfaces are bright white, while lead-free solders are yellowish.

5. Different infiltration
Lead-free solder is less wettable than lead-based solder.

Requirements of lead-free solder during soldering

Requirements of lead-free solder during soldering
1. Components. Components shall be lead-free and resistant to high temperature.
2. PCB flux. Flux with better wettability can make up for the shortage of solder.
3. Welding equipment and process. To select specific equipment and processes that meet the welding temperature.
4.PCB. PCB shall not be deformed after lead-free soldering, and the surface shall also be lead-free

What temperature should I use for lead-free solder?

650° to 700°F is the ideal working temperature for lead-free solder. The soldering tip must be hot enough to efficiently melt the solder, but too much heat might damage components since it passes through the leads and reduces the tip’s lifespan.

FAQ about lead-free solder?

Most frequent questions and answers

You will know by checking the ratio of lead to Tin which is stated on the packaging. A ratio like 30/70 means that there will be 30 percent tin and 70 percent lead. To see if lead is present, use a properly tinned soldering iron.

Given that lead soldering produces hazardous and deadly dust and fumes. And can seriously harm a human body when inhaled through mouth or nose. Lead solder is still being phased out because of these particular reasons as well as its negative effects on the environment and human health.

It was until 2006 when lead solder was widely used in almost all electrical departments. With a few limited exceptions, a European Union (EU) directive passed in 2006 prohibited the use of lead solder in most consumer electronics goods.


We hope that this essay about lead-free solder has clarified all of your concerns and possibly even taught you something new. You may read instructional materials, ask more about PCB design and PCBA service that we can provide, and access information on the IBE website.



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