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

Solder is a metal alloy that comprises lead and tin. The combination of thin and lead is what produces solder. Also, these two materials are usually melted using hot iron. There are several parameters that determine the composition of solder. These parameters include reflow characteristics, melting point, and creep behavior among others.

In most cases, tin accounts for more percentage than lead. In this article, we will be comparing the most common solder compositions which are 60/40 Vs 63/37 solder. What is the difference between these two types of solder and what benefits do they offer?

What is Solder made of?

Solder is a material used in creating a strong bond between metal parts. It is a metal alloy that combines different materials like tin and lead. Traditionally, solder comprises tin and lead with more percentage of tin.  Solder is generated by melting the solder. For solder to create a strong bond, its melting point should be below the pieces it is joining.

After the melting phase, the solder cools down and the parts bond permanently. In electronics production, engineers make use of solder to fix components to circuit boards. Therefore, solder used in this field must have great conductive properties. For many years, tin and alloy have been used to make solder.

As time went on, there were concerns about the environmental and health hazards of lead. Therefore, this made lead-free solder more commonly used in recent times. Typically, solder features a low melting point which is always around 200 degrees Celsius.

Also, solders are available in different form factors. Some solders are specially designed for specific applications or industries.

Types of Solders

60 40 Solder

There are two major types of solders based on the use of lead. These are lead alloy solders and lead free solders.

Lead alloy solders

These types of solders comprise lead and other metals. 60% tin and 40% lead or 63% tin and 37% lead are the most common composition. Also, leaded solder feature very low melting point which is usually about 180 degree Celsius. Therefore, this makes then bond materials well. Also, it is easy to work with leaded solder. Lead alloy solders feature properties which make people refer to them as soft solders.

Furthermore, the use of lead in this alloy has the formation of tin whiskers. Lead is a dangerous substance as it is poisonous to humans and their environment. It can contaminate ground and soil water. The EU restricted the use of hazardous substance by issuing the Restriction of Hazardous Substances directive in response to the concerns about the use of lead.

Lead free solder

Lead free solders comprise different metals. Tin serves as the base material of this solder. Lead free solders offer more strength to alloy. Other metals used include nickel and silver. However, the melting points of lead-free solders are higher than leaded ones. Therefore, lead free solders have more stress on components during PCB assembly. Furthermore lead-free solders don’t flow well and they tend to form less strong joints.

Manufactures had to develop solders that feature unique properties to prevent these problems. For instance, tin-silver-copper alloy features a very low melting point of 217 degrees Celsius. The integration of Silver helps in reducing oxidization. Also, copper enhances mechanical strength and conductivity. The mixture of nickel in alloy or the use of conformal coatings can help in preventing tin whiskers from forming.

What is 60/40 solder?


60/40 solder is a metal alloy that comprises 60% tin and 40% lead. It is also referred to as alloy Sn60Pb40. This solder is one of the alloy in the soft solder family. The melting point of 60/40 solder is very close to eutectic temperature. However, it is still referred to as non-eutectic solder. Also, 60/40 solder melting point is 190 degree Celsius. This solder flows well and it is very easy to use.

60/40 solder features good properties such as exceptional thermal conductivity and electrical conductivity. Furthermore, this solder composition creates a strong and permanent bond in metals. The 60/40 solder is ideal for use in electronics and PCB manufacturing.

It is crucial to store this solder in a non-corrosive and dry environment. The temperature of the environment should be between 10 to 40 degrees Celsius. One of the drawbacks of the 60/40 solder is that it is not eutectic.

The 60/40 solder features a high melting range. Also, this solder is suitable for joining copper and copper alloys. However, it is not suitable for joints exposed to vibration or shock. The 60/40 solder is available in solid wires, acid core, and rosin core. This solder is ideal for use in dip soldering baths due to its narrow melting range.

60/40 solder is a perfect option for soldering electronic and electrical connections. Also, the heat sources used include air-fuel torches and soldering guns. The 60/40 solder is ASTM B32 Alloy Grade Sn 60;J-STD-006 Sn60Pb40Sb0.4.

Also, this solder is soft. This implies that cracks don’t easily form if there is movement in the joint during cooling.

What is 63/37 Solder?

The 63/37 solder is a metal alloy that comprises 37% lead and 63% tin. This melting point of this solder is 183 degrees Celsius. 63/37 solder has a lower melting point compared to 60/40 solder. One of the benefits of the 63/37 solder is its eutectic property.

The 63/37 solder is eutectic and as such doesn’t feature a semi-solid state. Therefore, it is much easier to work with since it doesn’t produce much bad joints. Furthermore, the 63/37 solder is ideal for use in hand soldering application due to its properties. Also, it is commonly used in plating and wave soldering. During plating, 63/37 solder serves as a coating to prevent corrosion. It is also a base for soldering.

63/37 solder is available in foils, solder paste, and bar among others. This solder is also referred to as 63Sn/37Pb.

Difference between 60/40 vs 63/37 Solder

The main benefit of 63/37 solder is its narrow temperature range. This solder usually melt and becomes solid at a single temperature. The melting point of 60/40 solder is higher than that of 63/37 solder. The fact is that 63/37 solder features no plastic region. This means the solder solidifies quickly when it cools down. On the other hand, 60/40 features a plastic region.

The 63/37 solder is eutectic. Due to the cost of tin, this solder is more pricey than 60/40 solder. 60/40 solder was manufactured due to the high cost of tin. Therefore, it served as an alternative when cost is a major factor. The 63/37 solder features slightly more mechanical strength than 60/40. However, the 60/40 solder is a popular choice in the electronics manufacturing industry.

One main benefit of 60/40 solder is cost. However, the major drawback of this solder is its 50C plastic region. The 60/40 solder turns to plastic at 183 degree Celsius and melts at 188 degrees Celsius. A cold solder joint forms when the joint moves as the solder moves through the plastic region. Hand soldering can be very frustrating when this happens. The plastic region will have no consequences on the solder joints if the solder joints isn’t disturbed or moved until the solder has become fully solid.

63/37 solder is eutectic. This means that this solder moves from solid to liquid without experiencing plasticity. Since it features no plastic region, the 63/37 solder is better to work with. Joints made using the 63/37 solder look shiner. Therefore, the 63/37 solder has a better cosmetic effect than 60/40 solder. The 60/40 solder is widely used for small connections. However, it is not a good option for portable water or plumbing applications.

The Working Principle of Solder

The composition of alloy impacts the solidifying behavior of solder. Pure metals will become solid at a particular temperature and form crystals. Also, eutectic alloys can become solid at a single temperature. when non-eutectic alloys cools down, the non-eutectic stage starts precipitating in the case of intermettalic compounds.

Furthermore, a mushy state is the combination of solid particles in eutectic. Solder is widely used in different applications. The most common solder type is 60/40. However, flux is also needed in solders to ensure the formation of good joints. Flux prevents oxides from the joint’s area. Also, flux helps in forming a string and good bond.

The type of solder integrated in electronics manufacturing is usually in a wire form. The 63/37 wire solder makes hand soldering easy. Therefore, it is an ideal option in hand soldering applications.

What is the Function of Flux and Rosin Core Solder?

Lead free 60 40 Solder

Flux helps in improving soldered joint’s quality. It prevents oxidization from surfaces. Also, it chemically eliminates oxidation from the soldered surfaces and as well enhances the wetting of the surfaces when applying solder.

There are channels inside rosin core solder. These channels contain rosin flux. The embedded flux will clean the joint before any flow of solder. You should always use resin core solder for electronics. Lead-free and lead alloy solder can be rosin core.

The rosin core has a hollow core. None of the residues of rosin core solder will corrode. Since it is quite difficult to remove residue in electrical connections, the resin core solder is commonly used for soldering electrical products. Lead free and leaded solder can be rosin core. Avoid using acid core solder in electronics manufacturing. This type of solder is ideal for plumbing.

The lead-free rosin core solder is a great choice for soldering electronic components. Also, this solder comprises tin and lead with tin accounting for 60% and lead accounting for 40%. You can use copper in place of lead. Copper is a better option since lead is hazardous to human health and the environment.

Frequently Asked Questions

What is the strongest type of solder?

The 60/40 solder produces the strongest joints. Also, this solder composition has a very low melting point. Therefore, it is very easy to work with. However, it is more expensive.

What is the 50/50 Solder?

The 50/50 solder comprises 50% of tin and 50% of lead. It accounts for half of lead and half of tin. This type of solder isn’t ideal for electronics. It is commonly used for plumbing. If you use this type of solder for electronics manufacturing, it may result in failed joints. This is because the 50/50 solder doesn’t exhibit the properties of 60/40 vs 63/37 solder. Also, the 50/50 solder has lower ductility and higher melting point. Furthermore, this solder can have flux in it just like resin core solders.

Which solder is ideal for electronics?

The lead-free rosin core solder is a great choice for soldering electronic components. Also, this solder comprises tin and lead with tin accounting for 60% and lead accounting for 40%. You can use copper in place of lead. Copper is a better option since lead is hazardous to human health and the environment.

What is flux-core solder?

You will find flux core solder when wires cut in an object. During soldering, the flux releases and gets rid of oxidization built up on the surface of the metal. Then, the surface of the metal is cleaned and ready for soldering.

Is the 63/37 solder ideal for electronics?

Yes, the 63/37 solder is a suitable option in electronics manufacturing. It is commonly used in soldering electronic components. The melting point of this solder is 183 degrees Celsius. The eutectic property of this solder makes it an ideal choice in some applications.


It is crucial to choose an ideal solder composition when building electronic circuits. The two most common solders used are 60/40 vs 63/37 solder. During soldering, it is important to carefully consider the parameters that may affect the performance of your solder. Also, it is crucial to pay much attention during soldering by ensuring the hot soldering iron doesn’t cause injury.

In the electronics industry solder is often considered least. This shouldn’t be the case as solder plays a vital role in the performance of an electronic device. Therefore, it is crucial to understand the properties and nature of solder.




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