Melting Point of Solder | Key to Flawless Solder Joints

Soldering is an essential process in manufacturing and assembling electronics, especially for the production of high-quality printed circuit boards (PCBs). Understanding the melting point of solder is pivotal.

At PCBMay, we understand the critical importance of using solders with the ideal melting point to achieve precision bonding of components. We closely monitor the entire soldering procedure, including the heating process, to ensure our engineers choose the right type of solder alloy.

We ensure high-quality PCB assembly by precisely controlling the solder’s melting point. This allows the solder to melt, flow, and resolidify effectively, creating strong mechanical and electrical connections.

What is a Solder?

Solder alloy bonds metal through heat-enabled fusion. Low melting point types like tin-lead flow at relatively cool temperatures to permanently unify joint pieces upon cooling into an electrically conductive whole sturdy enough for mechanical stress.

Due to environmental concerns, lead-free variations made from tin, copper, and silver have become increasingly common alternatives.

The unique properties of solder alloys allow them to act as an electromagnetic glue, joining disparate metals through heat-enabled flow, cooling, and fusion.

Solder Is a Fusible Metal Alloy Composed of Tin and Lead

Solder Is a Fusible Metal Alloy Composed of Tin and Lead

Here are completely reworded versions within similar lengths:

SAC305 dominates electronics solder as 95.5% tin plus 4% silver and 0.5% copper balances wetting and other attributes. Varying the metallic recipe adjusts melting point, strength, and malleability to optimize solder properties where applied.

What Are the Types of Solder?

There are two main types of solder used in electronics assembly – eutectic solder and non-eutectic solder.

Eutectic solder

Eutectic solder alloy means it melts and solidifies at a single temperature point, 183°C for 63/37 tin/lead solder. This provides sharp melting behavior at a predictable temperature needed for reliable PCB manufacturing.

Non-eutectic solder

Non-eutectic solder has a range of melting points. This type of solder doesn’t transform from solid to liquid at a single temperature. Instead, it goes through a “pasty” phase where it is partially melted.

A common non-eutectic alloy of 60% tin and 40% lead melts over a range from 183°C to 190°C (361°F to 374°F).

Eutectic and Non Eutectic Solders are Two Types of Solder

Eutectic and Non Eutectic Solders are Two Types of Solder

What Are the Uses of Solder?

Solder has become an essential material in various industries due to its ability to permanently join metals through a process called soldering. Its primary use is to create electrically conductive and mechanically robust joints between metal components, particularly in the assembly of PCBs.

Let’s discover the uses of solder.

PCB Assembly

The most common use of solder is in electronics. Nearly every electronic device, from computers to mobile phones, contains soldered connections.

Solder allows different components like PCBs, wires, and processors to be permanently and reliably connected. The solder itself acts as both an adhesive that bonds the metals together and an electric conductor that allows current to flow smoothly across the connections.

Component Repair and Re-work

Solder is not just for initial assembly; it’s equally vital in repair and modification works. Skilled technicians use solder to replace defective components or to modify circuits.

This involves melting the existing solder, removing the component, and then re-soldering a new component in place.

Splicing Wires

Solder is also used in splicing wires, where it creates a strong, conductive connection between wire ends. This application is prevalent in both electronics and electrical work.

Creating Electrical Contacts

In switches, connectors, and other electrical interfaces, solder is employed to establish secure and conductive contacts. This is essential for maintaining the integrity of electrical connections over the lifespan of a device.

Formation of Conductive Traces

In some advanced manufacturing processes, solder can be used to form conductive traces directly on non-traditional substrates. This application is particularly relevant in flexible electronics and in situations where traditional etching methods are not feasible.

Sealing and Mechanical Strengthening

Solder can provide mechanical strength and sealing. It can be used to fill gaps or reinforce mechanically weak points in a circuit. This application is especially important in high-vibration environments or where physical stresses might be applied to electronic components.

Heat Sinking

Solder sometimes serves as a medium for heat conduction. In certain designs, it helps dissipate heat away from sensitive components, contributing to thermal management within the device.

What is the Melting Point of Solder?

Solder effectiveness hinges on heat-dependent fluidity. At melting points tailored composition-wise, rigid interconnecting metal suddenly flows for fusion, optimally somewhere between too viscous or too precariously drippy for joining conductors.

Average Solder Melting Point is 180_C to 190_C

Average Solder Melting Point is 180° C to 190° C

Let’s check out the melting point of different solder compositions.

SolderTin (%)Lead (%)Melting Point (°C)Melting Point (°C) – High
63/37 Lead Solder6337183220
60/40 Lead Solder6040183188
50/50 Lead Solder5050183212
45/55 Lead Solder4555183224
40/60 Lead Solder4060183234
96S Lead Solder964221
95A Lead Solder955236243
Alloy No. 1 Lead Solder183215
Alloy No. 2 Lead Solder183190
HMP 5S Lead Solder296301
LMP 62S Lead Solder6238179
TLS/5 Lead Solder296301
TIN (Pure Tin) Solder1000232
99C Non-Lead Solder991227
97C Non-Lead Solder973230250
SAC3 Non-Lead Solder96.53217219
MC1 Non-Lead Solder99.70.3232

 

What Factors Affect the Melting Point of Solder?

Solder Melting point is influenced by several factors.

Alloy Composition

The exact melting point of a solder alloy depends on its metallic composition and the ratios of its constituent elements. By adjusting the percentages of metals like tin, lead, silver, copper, bismuth, and more.

The richness of the alloy – the percentage of the primary metal, usually tin, determines the baseline melting point, with pure tin melting at 232°C.

Adding lead, which readily forms alloys with tin, significantly reduces the melting point in a relatively linear relationship. The eutectic 63/37 tin/lead ratio yields the lowest melting point of 183°C.

Silver and copper also decrease the melting temperature to around 220°C in small amounts while strengthening the solder joint microstructure. Higher silver and copper levels impede intermetallic formation, however.

The difference between 1-2% silver content in tin-silver-copper solders produces a melting point spread of nearly 25°C. The reflow profile design must match alloy melting properties.

Alloy Composition Affects the Solder Melting Point the Most

Alloy Composition Affects the Solder Melting Point the Most

Physical Form of Solder

The form of solder, whether it is wire, paste, or preformed shapes, can influence its melting behavior. Solder paste, for example, might exhibit different melting characteristics due to the flux and other additives present.

Flux Content

Flux, used in solder to clean and prepare the metal surfaces for bonding, can impact the melting point. Certain flux components may lower the melting point, thereby affecting the solder’s behavior during the soldering process.

Environmental Conditions

External factors such as ambient temperature and humidity can slightly affect the melting point of the solder. In controlled environments, like those maintained in professional manufacturing settings, these effects are minimized.

Aging and Storage Conditions

Over time, the properties of solder can change due to oxidation and other chemical reactions, especially if stored improperly. This can lead to a shift in the melting point, underscoring the importance of proper storage and handling.

What are the Factors You Should Consider When Choosing Solder

Selecting the optimal solder alloy is critical for manufacturing quality electronics assemblies. The ideal solder balances different properties based on the application requirements and production processes.

Let’s discover the factors you should consider when you are choosing solder.

Type of Project

The nature of the project dictates the solder type. High-performance devices operating under extreme conditions may benefit from silver alloy solder due to its high electrical conductivity and temperature resistance.

Material Compatibility

You should select a solder that matches the components’ material properties. Different materials require specific solder alloys for optimal results.

Melting Temperature Range

The melting temperature of the solder should align with the materials being soldered. You should select a solder with a melting point lower than the materials being joined. Temperature control is also crucial to prevent overheating or underheating, which can affect solder joint reliability​​.

Flux Core Presence

Opt for flux-filled solder to enhance bonds. Built-in cleansing agents curb surface oxidation that impedes wetting.

Flux catalyzes fluid spread while preventing ragged beading behind faulty connections or bridging risks. Its corrosion-fighting flow assistance fortifies joins.

Environmental Impact and Safety

Normal solder use lead which is harmful to you. Lead-free solders are environmentally friendlier, reducing toxic lead release.

Regulatory Requirements, and Cost

When selecting solder, consider regulatory compliance with regional environmental and health standards, cost-effectiveness balanced against quality, and reliability.

Different regions or industries may have specific regulations or standards governing the use of certain types of solder, particularly about their composition. It’s essential to be aware of and comply with these regulations to avoid legal issues.

The price of solder varies depending on the type and quality. While it may be tempting to opt for a cheaper option, it’s important to consider the long-term implications of this choice. You should balance the cost with the requirements of the project.

Wire Size

Consider the size of the solder wire influences the soldering process. Thinner wires are better for precision work on small components, while thicker wires suit larger components or joints.

What Are the Differences Between High-Temperature and Low-Temperature Solders?

Solders can be broadly divided into high-temperature alloys that melt above 230°C and low-temperature alloys melting below 230°C. The melting point requirements depend greatly on the components and materials being joined, process parameters, service environment, and other specifications.

Let’s see the differences between High-Temperature and Low-Temperature Solders.

Composition and Melting Point

Lead-free, high-tin, and gold alloys form solders forging temperature-resilient bonds above 450°F upon recrystallization.

Lower melting point solders mix tin with bismuth, and indium, between 117 and 320 degrees Fahrenheit for connections where heat taxes more delicate assembly.

Applications

Used in aerospace, automotive electronics, power electronics, and high-power LED lighting.

Ideal for heat-sensitive components, flex circuits, and step soldering processes.

High Temperature Solder Melts at 232_C

High-Temperature Solder Melts at 232° C

Benefits

Offers enhanced reliability, improved thermal management, and environmentally friendly options.

Reduces thermal energy requirements, extends equipment life, and lowers electrical usage.

Challenges

Requires specialized soldering equipment and techniques due to higher melting points, with potential issues of thermal expansion mismatch and IMC formation.

Generally less suitable for high-temperature environments and may have lower mechanical strength.

Frequently Asked Questions

1. What are Solder Blends?

Solder blends are mixtures of different metals that create various types of solder, each with unique properties. These blends often include lead, tin, and flux, but may also contain other metals like antimony, bismuth, copper, indium, nickel, and silver.

2. Which Solder Is the Best to Use?

The “best” solder depends on various factors, including the types of components used, the operating temperature of the device, and environmental considerations. Generally, for most applications, a lead-based solder with a 60% tin and 40% lead composition is preferred due to its low melting point and strong electrical conductivity.

3. How Does the Melting Point of Lead-Based Solder Compare to Lead-Free Solder?

60/40 tin/lead mixtures dominated solder lubricating metal merges near 183°C, but toxicity truncated use despite superior wetting even at lower temperatures. In contrast, lead-free solder typically melts at about 217 degrees Celsius. The higher tin content in lead-free solders raises the melting point.

Conclusion

The melting point of a solder alloy is one of its most fundamental properties in enabling the effective joining of metallic surfaces. Understanding the varying melting points across different solder types enables manufacturers to tailor their approach to the specific requirements of each project.

PCBMay is one of the companies that excels in the PCB soldering process. Since 2008, PCBMay has been making outstanding PCBs with the best soldering quality. Our commitment to quality and reliability has made customers and clients believe in us.

If you need a quote or any other help regarding the soldering process, our experts are ready to answer all your queries.

Update cookies preferences
Scroll to Top

Get a Quick Quote!

x
Upload File

Get a Quick Quote!

x
Upload File