Lead Solder vs. Lead-Free Solder

Almost all manufacturing processes for electronic devices use solder to join parts with printed circuit boards (PCBs). While lead solder was once the go-to choice for assembling these boards, manufacturers have begun shying away from the use of lead in all products, from industrial applications to cell phones.

There are multiple types of solder, and the best options will depend on the application. These days, lead-free soldering is the most popular choice for electronics with PCBs.

Learn more about lead solder vs. lead-free solder and the benefits of going without this toxic and potentially dangerous element.

What Is Solder?

Solder is a metal alloy used to join two metals together. It’s commonly used in manufacturing electronics. Various types of solder are used for joining different types of metals. Each type is classified by the following characteristics:

  • Form
  • Core syle
  • Composition

The solder must have a lower melting point than that of the metals it is joining together.

Soldering works by first mounting a component to the printed circuit board and applying heat to the joint. Then assemblers apply solder to the joint to adhere the part to the board before cutting the component leads.

Lead solder and lead-free solder are the two primary types used for electronic assembly. The most popular choice is lead-free rosin core soldering, though lead options were previously preferred.

So, what are the differences between the two?

Lead-Free Solder vs. Lead Solder

Here are some of the key differences between these types of solder.

What Is Lead Solder?

Lead solder is also referred to as SnPb solder as it is a metal alloy with tin (Sn) and lead (Pb) used as base components. This type of solder was previously preferred for the following reasons:

  • Cooling: Lead solder cools more slowly than other metal options. This reduces the possibility of the joint cracking.
  • Wet joints: Using this type of solder is effective in wetting joints, providing an effective electrical connection for both leads and printed circuit board pads.
  • Melting point: Instead of having a melting range like many metal alloys, lead solder has a defined melting point. This makes it easier to create automated PCB assembly processes. And since the melting point is lower than other options, it is less likely to damage electronics and is easier to reach the temperature.

However, lead is known to have adverse effects of lead on human health and the environment. The United States Centers for Disease Control and Prevention (CDC) notes that lead exposure can result in a range of health concerns, from memory loss to reduced fertility.

Additionally, laws and regulations from the United States Environmental Protection Agency (EPA) regarding the disposal of lead waste ban manufacturers from using lead solder for their products.

What Is Lead-Free Solder?

Lead-free solder is typically a metal alloy blend that has varying percentages of the following elements:

  • Antimony
  • Bismuth
  • Copper
  • Nickel
  • Silver
  • Tin
  • Zinc

The most commonly used lead-free blend includes tin and copper, but different applications work better with different alloys. Lead-free solder has a higher melting point compared to lead options. This type also creates stronger and harder joints when joining metals compared to lead soldering.

As electronics have integrated into nearly all aspects of our lives, it has become increasingly important to avoid products with lead in them.

While lead-free solder is not ideal for critical applications such as aerospace or medical products, it works well for electronics assembly. Lead-free soldered joints can lack the surface tension needed to resist external forces. Since most electronics do not have to endure high-stress environments, this is not a major problem for printed circuit board applications. There are significant benefits to working with lead-free solder.

5 Benefits of Lead-Free Solder

Using lead-free solder comes with many advantages. Here are some of the most significant benefits:

5 Benefits of Lead-Free Solder

1. Better for Health

Using lead-free solder is more beneficial for the health of humans and animals. Short-term lead exposure can cause health concerns, such as:

  • Weakness
  • Tiredness
  • Headaches
  • Memory loss
  • Abdominal pain
  • Pain in hands and feet

Higher levels of lead and longer-term exposure can cause severe health ailments, from brain damage to death.

Opting for lead-free solder is the best choice for the health and wellness of both the workers assembling electronics and the users of those devices.

2. Better for the Environment

Products made with lead can wreak havoc on the environment. Lead can contaminate air and soil when its dust settles. Plants can absorb the metal dust through their leaves, and shavings can leech into the ground and waterways.

With so many electronics in the world today, many of them end up in our landfills. Using lead-free solder is essential for minimizing lead’s negative impacts on the environment and public health.

3. Ideal for Electrical Circuit Board Soldering

Compared to lead soldering, lead-free alloys work better for electrical printed circuit board applications.

Lead-free solder does not spread out during reflowing. This creates stronger bonds without significant challenges like rapid stencil wear. Lead soldering practices are more likely to cause voids or fillet lifting. Overall, solder without lead produces better results for the PCBs used in electronics.

4. Complies With Regulations

For nearly 20 years, the following regions have banned the use of lead in consumer products:

  • The European Union
  • California
  • China

Using lead-free solder is essential for creating electronic devices that can be distributed and sold in these areas.

In September 2020, the EPA published regulations on lead-free soldering to reduce lead in public drinking water. The government also offers tax benefits for manufacturers that avoid the use of lead in their processes. Lead-free solder also complies with the Restriction of Hazardous Substances (RoHS).

5. Compatibility

One of the other benefits of lead-free solder is its compatibility with existing manufacturing processes. Most PCB producers can easily shift their practices away from using lead solder without many drawbacks.

Steps toward eliminating lead in consumer products mean that the U.S. may begin restricting lead soldering practices in the coming years. Utilizing lead-free options will likely become a necessity.

Explore Lead-Free Options at Millennium Circuits Limited

A few key characteristics make lead-free solder a better option for printed circuit board assembly processes. From environmental safety to producing harder bonds, lead-free solder has many benefits.

At Millennium Circuits Limited, we prioritize compliance and offer RoHS-compliant surface finishes and materials for every one of our products. We always provide every circuit board shipment with a RoHS Certificate of Compliance.

Are you interested in learning more about our lead-free options or have additional questions? Contact Millennium Circuits Limited today!

Explore Lead-Free Options at Millennium Circuits Limited