Lead vs Lead Free Solder Differences for PCB Manufacturing

Introduction

A debate of Lead vs Lead Free Solder is important in PCB manufacturing where both solder contributes to the performance of a product, its safety, as well as environmental compliance. In this discussion, we’ll look into their differences, properties and impacts so that you can get the important bits of information that’ll guide your decisions to get the most out of your projects.

What is a Lead Solder?

Tin and lead are one of the combinations that make up a leaded solder (also called soft solder). Having a lower melting point, about 183 °C (361 °F), it has a lesser affinity to cause bonding with the crystals. As such, it’s gentler on your PCB and components. Also, at a lower heat the risk of damage is reduced. Bright and smooth joints are also created by lead solder. The joints are typically less quality problem prone than lead free. But it’s toxic due to the lead content. As this is the case, many industries now choose lead free alternative. Lead solder works well, but of course it has health implications.

What is a Lead Free Solder?

Lead free solder is a combination of one or more metals that is devoid of lead. It is tin, copper, silver or zinc. The most common mix is tin and copper. Lead free solder melts at a higher temperature than the leaded solder. It has a melting point from 50 °C and over to 200 °C. It is safer to health and the environment. In 2006 lead free solder became the normal solder, as regulations became stricter. It usually works well with about 2% flux.

• Tin Copper – the most common lead-free solder combination. Copper makes your solder joints tougher.
• Tin-Silver – has excellent electrical conductivity. Silver helps prevent oxidation and resists corrosion.
• Tin-Zinc – melts at lower temperatures. Cost-effective and convenient. Suitable for sensitive parts that require less heat.

What are Lead and Lead-Free Solders Made Of?

Tin and lead make up leaded solder. It has also been called SnPb solder, melting at 183°C. It works with the ease, it’s shock resistant and is less flawed when cooled. Lead is, however, harmful to your body and to the environment.

Lead free solders are composed of metals like tin, copper, silver or zinc. The common mix is tin – copper, at 217°C. Has higher melting point that makes it harder to use in PCB manufacturing compared to leaded solder. But it is safer and better to use for the planet and engineers.

What is the Difference Between Lead vs Lead Free Solder?

Rusting

Leaded solder will rust much quicker than lead free solder. It may form a stable protective layer on its surface, which prevents corrosion. As a result, it is ideal for humid areas. But this is not the case with leaded solder, it corrodes faster and without this protection over time. Poor joints will cause corrosion which will weaken them and possibly shorten your PCB’s life.

Melting Point

Solder containing lead melts at 183°C. As a result this facilitates the work with during soldering. This solder melts at a higher and variable temperature than lead free solder. Its customary range is from 218°C to 250°C. Sensitive PCB components or tracks are damaged with higher heat. Lead free solder requires very careful control of temperature.

Physical Features

Soft, shiny and smooth are the characteristics of leaded solder joints. They are also easy to inspect for quality. But lead free solder joints are harder and not as shiny. Additionally, they can appear rougher or dull. Long term reliability is lead free solder. Because of its higher melting point, it is more stable than over time. Nevertheless, its less wetting property may deteriorate the bond strength.

Health Concerns

The lead in the leaded solder is toxic to the human. Lead can enter into your body inhalation, ingestion or skin contact. Accumulating with time it develops into a serious health problem. Especially at risk are children and older adults. This danger is eliminated through lead free solder, which is safer to use. Today, lead free options have been preferred to protect health and safety.

Cost

Lead free solder is much more expensive. Lead is cheaper than copper or silver. Engineers want lead-free solder but the pricier alloys used to replace the lead make the cost go up. There are, however, environmental and health benefits to it that justifies its price. For projects using the leaded solder, it also may still be a reasonable choice from a budget perspective.

Bond Strength

Strong and reliable initial bonds are provided by leaded solder. The soft surface is able to easily spread over surfaces. Over time lead free solder forms harder more durable bonds. Performance under mechanical stress is superior to that of the silver coated copper, making it suited to high strain applications.

Environmental Impact

Leaded solder is toxic and therefore harmful to the environment. If disposed of improperly they can pollute soil and water. Lead-Free solder is eco-friendly and can be free of lead, which means it will be safer for recycling. It is RoHS compliant. Lead free solder is waste free and supports the use of sustainable manufacturing practices.

Electrical Conductivity

Lead free solder has better electrical conductivity than lead solder. It is suitable for high performance circuit. Leaded solder has however remained the reliable conductor for standard electronics.

Wettability

The wettability of leaded solder is excellent, easily spreading on surfaces. It also easier to form strong initial bonds. Wettability and spreading of lead free solder are poorer. Soldering can be challenging for beginners because of this. Improving performance of lead free solder is a function of proper flux use.

Ease of Use

Lead solder is easier to work with for beginners. The reduction of its lower melting point lowers the risk of overheating components. Also, lead free solder is harder to use because of its higher temperature. You need to be careful not to break sensitive parts.

Properties of Lead vs Lead Free Solder

Here is the comparison table of the properties of two types of solder:

Advantages and Disadvantages of Lead vs Lead Free Solder

In choosing it is important to know its advantages and disadvantages in comparison with the lead – lead free solder. Lead solder is easy to use but dangerous to your health. Safer, lead free solder is harder to work with. So let’s break this down into what’s good and bad.

Advantages

Lead Solder

• Low Melting Point – Lead melt solder has melting point at low temperature. So, its usage is very easy. This solder does not damage the parts much.
• Excellent Wettability – Lead solder wets well on surfaces. It results in clean and smooth joining. This, in turn, contributes to lesser mistakes.
• Cost-Effective – Lead solder is cheaper to produce. It saves you a buck or two on projects.
• Proven Reliability – Lead solder has been in existence for several decades. It is trusted and reliable in electronics.

Lead Free Solder

• Better for Health – Lead-free solder is safer to use. It does not pose health risks. You do not have to worry about lead poisoning.
• Better for the Environment – Eco-friendly and doesn’t harm the environment like lead.
• Ideal for Electrical Circuit Board Soldering – Works very well with electrical circuit boards. Produces strong, reliable joints.
• Complies With Regulations – Lead-free solder complies with health and safety regulations. It is mandatory in several industries.
• Compatibility – Lead-free solder suits most PCBs. This is very suitable for present electronics.

Disadvantages

Lead Solder

• Toxicity – Lead solder is toxic. Both humans and the environment are affected. Causes skin damage, neurotoxicity, and damage to the kidneys.
• Regulatory Restrictions – Lead solder faces many restrictions. Laws limit its use in some areas.
• Lower Thermal Fatigue Resistance – It is not very good at taking on heat changes. This can cause solder joint failure over time.
• Declining Viability – More companies are finding it less viable to use lead. Safer alternatives have replaced it.

Lead Free Solder

• High Melting Point – Needs higher heat to melt which makes it harder to use.
• Low Wettability – Doesn’t spread as easily as lead solder that can cause weak joints.
• Deposits – May leave more residues that will cause issues with electrical connections.
• Tin Whiskers – Lead-free solder can form tin whiskers which are tiny filaments can short-circuit your board.
• Metal Dendrites – Sometimes, lead-free solder can grow metal dendrites that can cause electrical failures.

Effects of Lead vs Lead Free Solder on Different Types of Soldering

Quality and performance of your PCB depends on solder, which is lead or leadfree. By keeping soldering conditions tightly regulated, PCB manufacturers have control over many issues. But, your layout design and component selection have a large effect in producing a solderable assembly. The choice depends on the design of your PCB. Select a proper layout and components to prevent soldering problem and to make it operate smoothly.

FAQs About Lead vs Lead Free Solder

• What Are the Steps for PCB Manufacturers to Handle Lead-Free Solder’s Higher Temperatures?

PCB manufacturers must take part to handle the higher temperatures of lead free solder. Adjust your soldering equipment to adjust to the heat. Recalibration of reflow ovens, soldering stations and more. Then, lengthen the heat dissipation by redesigning the board and the use of thermal buffers. Use components that do not get broken if they stay in high temperature. Thermal shock will be prevented if you preheat the PCB.

• What Are Some Challenges of Lead-Free Solder in High-Frequency and Precision Applications?

Lead free solder does not work so well in high frequency or precision applications. Property of lead free solder is higher melting point and lead free solder has different properties from leaded solder. Even signal strength and component performance are affected. Lead free solder may also increase resistance and decrease wettability when working at high frequencies. It can result in signal interference. Lead free solder will also result in a greater number of joint failures later in time.

• What Are the Alternatives to Lead Free?

Lead free alternatives to lead solder are now being introduced into electronics manufacturing. Different properties of new alloys make them ideal for different jobs. Sn-Ag-Cu is widely used. It’s a strong reliable material that’s easy to satisfy with environmental standards. Other lead free alternative alloys are tin bismuth (Sn Bi), tin gold (Sn Au), and tin palladium (Sn Pd). The task is approached with unique advantages for each alloy. For example, tin bismuth melts at a low temperature. Tin gold likes high performance applications. Tin palladium is more corrosion resistant. These alternatives to road use offer increasing environmental concerns more options for different projects.

Conclusion             

This leads to our conclusion that when it comes to solder of a lead vs lead free solder variation, everything affects the PCB in one way or another. We at PCBMay know how crucial it is to pick the best solder for your project. We customize our manufacturing process so that you get lead-free solder for environmental purposes or you can go with lead solder, which has higher reliability and lower cost.