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60/40 Vs 63/37 Solder – What are their Similarities and Differences

Posted:03:18 PM October 11, 2023 writer: iotbyhvm


In this concise exploration, we focus on comparing the two most prevalent solder compositions, 60/40 and 63/37, often hailed as the best solder for electronics. These alloys are crucial for making smooth connections between different parts. Now, let's uncover the main differences and advantages they provide.

60/40 solder comprises 60% tin and 40% lead. It offers versatility and finds wide application in electronics and various soldering tasks, thanks to its relatively low melting point, which sits at around 183°C. This solder type is a reliable workhorse but lacks the eutectic properties of its counterpart.

63/37 solder, on the other hand, is a unique blend consisting of 63% tin and 37% lead. Its melting point matches that of 60/40 solder at 183°C. However, the fundamental advantage of 63/37 solder is its eutectic nature, which means it has a single, sharp melting point. This property is particularly advantageous when precise temperature control is essential. The distinctions between these two solder alloys extend beyond their melting points. 63/37 solder exhibits better fluidity during soldering, resulting in more even and smoother flow. It's important to note that while both solders create strong and reliable solder joints, 60/40 solder may be slightly less robust due to its non-eutectic nature.

Additionally, 60/40 solder contains a higher lead content, which raises concerns regarding environmental regulations such as the Restriction of Hazardous Substances (RoHS) directive. In contrast, 63/37 solder contains less lead and is closer to meeting RoHS requirements. the choice between 60/40 and 63/37 solder hinges on the specific demands of your soldering project. Both have their merits, but 63/37 solder shines in applications where precise soldering control is crucial.

What is Solder made of?

Solder is a crucial material in creating strong bonds between metal parts, commonly composed of a metal alloy that blends various elements like lead for soldering. Traditionally, solder comprises more tin than lead, and its fundamental property lies in its ability to melt at temperatures lower than the pieces it joins. The melting part is very important because when the melted solder cools down, it sticks the parts together permanently. In electronics, engineers use solder to attach parts to circuit boards, and it's crucial that the solder conducts electricity well. For a long time, people have primarily made solder from what is solder made of.

However, environmental and health concerns surrounding lead prompted the rise of 63-37 solder as a safer alternative. Typically, solder exhibits a low melting point, hovering around 60 40 solder melting point, ensuring it remains below the critical temperatures of the components it binds. When comparing 63/37 vs 60/40 solder, it's important to consider their melting points. 60/40 rosin core solder and 40/60 rosin core solder are commonly used for electronic applications.

Solder wire with a 60/40 rosin core is often preferred for its properties, such as solder temperature 60/40 and solder melting point 60/40. Additionally, 60 40 solder and 63 37 solder are variations of solder alloys, each with its own melting point and performance characteristics.

For specific applications like pcb solder or motherboard solder, choosing the right solder composition, such as 63/37 solder, can be critical. In certain situations, such as military or high-performance applications, specialized military solder may be required.

In summary, solder plays a crucial role in electronics and various other applications, with its composition, melting point, and performance characteristics being important factors in its selection. The transition from lead for soldering to lead-free solder like 63-37 is driven by environmental and health concerns.

Types of Solders

Solders come in various compositions, each designed for specific applications. Common solder types include lead-based and lead-free solders. In the past, people widely used lead for soldering, but they are now replacing them with lead-free alternatives due to environmental concerns. The choice of solder type depends on the specific requirements of the task at hand. Here are some common types of solders:

  1. Lead-Based Solder: This traditional solder, known for its 60 40 solder melting point, contains a significant amount of lead in its composition. Common alloys include 60/40 (60% tin and 40% lead) and 63/37 (63% tin and 37% lead). These solders feature low melting points, making them easy to work with, with the solder melting point 60/40 being a key characteristic. However, environmental and health concerns associated with lead are phasing them out, especially given the safer properties of 63 37 solder melting point alternatives.
  2. Lead-Free Solder: To address environmental and health issues, lead-free solders have gained popularity. They typically contain combinations of tin, silver, copper, and other metals. Lead-free solders may have higher melting points than lead-based ones, but they comply with regulations such as the Restriction of Hazardous Substances (RoHS) directive.
  3. Flux-Core Solder: Flux is like a helper in soldering. It does three important things: it cleans away rust, makes the solder stick better, and stops more rust from forming while you're soldering. Flux-core solder is solder with this helper already inside, so you don't have to add it separately when soldering. It makes soldering easier.
  4. Rosin-Core Solder: This type of solder contains a rosin-based flux core. Rosin is a natural resin derived from pine trees and is widely used in electronics soldering. It provides good wetting properties and is suitable for various electronic applications.60 40 rosin core solder and 40/60 rosin core solder are used in various applications, each with its own melting point. Rosin-core solder is often preferred for electrical work.
  5. Silver Solder: Silver solder, also known as silver brazing, is used in applications requiring high-strength joints. It contains a significant amount of silver and is commonly used in jewelry making and plumbing. Silver solder requires higher temperatures to melt and form strong bonds.
  6. Aluminum Solder: Soldering aluminum can be challenging due to its high melting point and oxide layer. Specially formulated aluminum solder works with aluminum surfaces, often containing zinc and other alloys to enhance adhesion.

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What is 60/40 solder?

60/40 solder, also known as alloy Sn60Pb40, consists of 60% tin and 40% lead, belonging to the soft solder category. Despite its melting point, closely resembling the eutectic temperature, it's classified as non-eutectic solder with a melting point at 190 degrees Celsius. This solder flows smoothly, making it user-friendly.

Renowned for excellent thermal and electrical conductivity, 60/40 solder forms robust, permanent metal bonds, ideal for electronics and PCB manufacturing. Proper storage in a non-corrosive, dry environment, ranging from 10 to 40 degrees Celsius, is crucial. However, its drawback lies in its non-eutectic nature and a relatively high melting range.

Suitable for joining copper and its alloys, it's less apt for shock or vibration-exposed joints. Offered in solid wires, acid core, and rosin core varieties, it's favored for dip soldering baths due to its narrow melting range.

60/40 solder proves perfect for electronic and electrical connections, compatible with heat sources like air-fuel torches and soldering guns. It complies with ASTM B32 Alloy Grade Sn 60 and J-STD-006 Sn60Pb40Sb0.4 standards. Being soft, it minimizes crack formation when joints encounter movement during cooling.

What is 63/37 Solder?

63/37 solder, often referred to as eutectic solder, is another commonly used solder alloy. It contains 63% tin and 37% lead. Unlike 60/40 solder, 63/37 solder is eutectic, which means it has a single, sharp melting point. This property makes it particularly suitable for applications where precise control over the soldering process is crucial.

63/37 solder, composed of 63% tin and 37% lead, boasts a low melting point at 183 degrees Celsius, distinguishing it from 60/40 solder. Its standout feature is its eutectic nature, bypassing a semi-solid state, making it remarkably user-friendly and less prone to flawed joints. Ideal for hand soldering tasks, it finds common usage in plating and wave soldering. In plating, it serves as a corrosion-resistant coating, doubling as a soldering base. It's available in various forms, including foils, solder paste, and bars, and many people know it as 63Sn/37Pb solder, appreciating its ease of use and dependable properties.

Difference between 60/40 vs 63/37 Solder

Now, let's explore the key differences between 60/40 and 63/37 solder:

- Melting Point: One of the most significant differences is the melting point. 60/40 solder has a lower melting point, typically around 183°C (361°F). In contrast, 63/37 solder, being eutectic, has a sharp melting point at 183°C (361°F). This means that 63/37 solder transitions directly from a solid to a liquid state, making it ideal for applications where precise temperature control is necessary.

- Fluidity: Due to its eutectic nature, 63/37 solder also exhibits better fluidity during the soldering process. It flows more evenly and smoothly, reducing the likelihood of solder bridges or cold joints.

- Strength and Reliability: While both solders create strong and reliable solder joints, 60/40 solder may be slightly less robust due to its non-eutectic nature. However, this difference is often negligible for most electronics applications.

- RoHS Compliance: In recent years, there has been a shift towards lead-free solder due to environmental regulations such as the Restriction of Hazardous Substances (RoHS) directive. 60/40 solder contains a higher lead content and may not be RoHS compliant, whereas 63/37 solder has a lower lead content and is closer to meeting RoHS requirements.

- Application Specificity: 60/40 solder serves as a versatile choice for general soldering tasks, finding common usage in electronics, plumbing, and hobbyist applications. Conversely, 63/37 solder proves preferable for applications demanding precise soldering control, notably in aerospace and military electronics.

The Working Principle of Solder

Understanding the working principle of solder is essential for achieving successful soldering results. Applying heat to the solder joint causes the solder alloy to melt, and it wets the surfaces to be joined, forming a metallurgical bond as it cools. This bond ensures electrical conductivity and mechanical stability.

The composition of solder alloys plays a pivotal role in their solidifying behavior. Pure metals solidify at specific temperatures, forming crystals, while eutectic alloys solidify at a single temperature. In contrast, non-eutectic alloys exhibit a more complex solidification process, with non-eutectic stages precipitating, often in the form of intermetallic compounds. Eutectic alloys, on the other hand, enter a "mushy" state, with a combination of solid particles present.

Solder, a widely used material, finds application in various fields. The prevalent 60/40 solder, for instance, is commonly utilized. However, solder alone isn't sufficient; flux is a crucial component for ensuring the formation of strong joints. Flux serves to prevent oxides from forming on the joint's surface and aids in creating a robust and clean bond.

In electronics manufacturing, solder is typically used in wire form. The 63/37 wire solder, with its eutectic properties, simplifies hand soldering tasks. Consequently, it stands as an excellent choice for various hand soldering applications, ensuring ease and reliability in the soldering process.

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What is the Function of Flux and Rosin Core Solder?

Flux is a crucial component in soldering. It serves multiple purposes, including:

Flux improves soldered joint quality by preventing oxidation and enhancing wetting. Rosin core solder contains channels with embedded flux, cleaning joints before solder application, making it ideal for electronics. Avoid acid core solder in electronics. Lead-free and leaded solder can be rosin core. Lead-free solder, with 60% tin and 40% copper, is a safer alternative to lead-based solder, which is harmful to health and the environment. Copper is a preferable substitute for lead.

- Removing Oxidation: Flux assists in the removal of surface oxidation from the metals being soldered, ensuring a clean and strong bond.

- Enhancing Wetting: Flux promotes the wetting of solder onto the surfaces, allowing it to flow evenly and create a solid connection.

- Preventing Oxidation: During soldering, the flux creates a protective barrier, preventing the formation of new oxide layers on the heated metal surfaces.

Rosin core solder is a type of solder that contains a flux core made from rosin, a natural resin. This type of solder is common in electronics because it offers both the solder alloy and the necessary flux, simplifying the soldering process.


In conclusion, the selection between 60/40 and 63/37 solder hinges upon the precise demands of your soldering project. While 60/40 solder's versatility makes it suitable for a broad range of applications, 63/37 solder excels in providing precise control and superior fluidity, especially crucial in tasks demanding soldering precision. Moreover, it's essential to take environmental regulations into account and opt for lead-free solder when required to ensure compliance with standards like RoHS. A through understanding of the characteristics and distinctions between these solder alloys empowers you to make well-informed decisions, paving the way for successful soldering outcomes in your diverse projects. So, whether you're working on electronics, plumbing, jewelry, or other applications, your choice of solder alloy, including soldering temperature 60/40, solder composition, 60 40 solder temperature, electrical solder rosin core, and solder wire 60/40 vs 63/37, will play a pivotal role in achieving strong, reliable, and compliant connections.


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