Does Solder Wire Require Flux?

What Is Solder Wire?

Solder wire consists of a metal alloy that can join together two or more electrical devices typically during the construction/assembly of electronic devices/circuit boards. The most commonly used solder wire consists of an alloy comprised of tin and lead (for example: 63/37 solder wire would contain 63% tin and 37% lead; or 60/40 solder wire refers to its percentage composition ratio). For those who don't want to use lead, tin/silver/copper (SnAgCu) alloys are popular alternatives.

The way that solder wire is made affects how well it will perform. For instance, 63/37 solder wire will be made with a eutectic mix, this means that it goes from solid to liquid without having to go through a plastic (mushy) state; therefore making it easier to create precision solder joints.

What Is Flux and Why Use Flux?

Flux is a chemical cleaning material added to your solder wire (or added before you solder) in order to chemically remove any oxidation from metal surfaces. This provides you with a clean surface for making a solid connection (bond) between your solder and the electrical devices being soldered. Oxide buildup can hinder a reliable bond between metal surfaces and ultimately lead to weak solder joints. Therefore, removing oxides is an important part of creating any type of electrical connection, and will allow you to have a successful and strong solder joint.

There are two types of solder that you can choose from: rosin-core solder and solid-core solder. Rosin-core solder has a flux that is built into it so that the solder can be used by itself for most applications. Solid-core solder does not have any type of flux in it; therefore an outside source of flux must be used before using solid-core solder.

Is Flux Needed When Soldering Wire?

The answer depends on the type of solder that you are using along with the type of application you are doing. If you are using rosin-core solder, since there is already flux in the solder it is not necessary to use any additional flux unless you are trying to solder on heavily oxidized surfaces and need to further clean the surface before using solder. However, with solid-core solder, there is no flux in the wire and flux will have to be added to create a strong and dependable connection.

For novice solderers, using a rosin-core solder is the best way to go, as the built-in flux eliminates the need for a separate source of flux. Rosin-core solder makes it easy to solder wires, PCB components, or small electronic devices. Advanced solderers may prefer to use solid-core solder with a separate source of flux, as it allows more control of the soldering process.

Which Type of Wire Is the Best Wire For Soldering?

Choosing the best wire for soldering depends on what you are trying to accomplish with your soldering project. The following are crucial guidelines for soldering:

1. In situations when soldering electrical/electronic components, the best types of solder wire are typically 63/37 or 60/40 due to their low melting points and predictable melting points.
2. Consider using lead-free solder wires when soldering in more environmentally conscious/high-compliance situations, such as using tin-silver-copper (SAC) alloys.
3. Regarding solder wire diameter, thinner wires (e.g., 0.6, 0.8 mm) are ideal for precise soldering applications, and thicker wires (e.g., 1.2, 1.5 mm) are suitable for large component connections.

If you are looking for the best of both worlds when it comes to ease of use and soldering performance, a rosin-core solder that is 63% tin, 37% lead will be best suited for the majority of projects.

Factors to Consider When Buying Solder Wire

There are several factors to consider when purchasing a solder wire to get the best results from your soldering task:

1. Material Used in Making Solder Wire

The composition of solder (i.e., whether it has lead or is lead-free) influences the performance of individual solder wires. While lead solder generally has better flowing characteristics and superior wetting, some communities have phased out the use of lead due to its environmental impact. Conversely, lead-free solder has been developed as an alternative material for soldering because of its more environmentally and biologically friendly attributes.

2. Type of Flux

Rosin-core solder wires are convenient because they contain the flux required for soldering; solid-core solder wires will require some type of auxiliary flux to aid in soldering to complete the soldering process. High-activity flux is used to solder items with larger degrees of oxidation, while low-activity flux is sufficient for soldering to clean materials.

3. Cost of Solder Wire

Solder wire comes in various forms with fluctuating prices depending upon their materials and how they were made. For example, 63/37 solder is generally priced slightly lower than its lead-free alternatives. However, because it contains lead, it will not pass the RoHS compliance test. It is recommended that you compare brands of solder and read product reviews before deciding which one you would like to use, in order to get a combination of good quality, price, and performance.

4. Quantity and Diameter

Solder wire is available in many sizes of spools and diameters. The diameter of the wire should be chosen based on the size of the project you will use the solder wire for. For most basic electronics, a diameter of 0.8mm should suffice.

Tips for Successful Soldering

To help ensure that your soldering project is a success, some recommendations are:

• Use the correct temperature setting on the soldering iron (overheating will damage parts, while underheating can result in weak joints).
• Clean and tin the tip of the soldering iron prior to using it, in order to get the most heat transfer and consistent results.
• Do not store your solder wire in humid/damp areas or expose it to moisture, as this will decrease the performance of the solder wire.

Frequently Asked Questions

What is the best solder wire?

There is a different type of solder wire that is better for different purposes. For most electronic projects, the commonly used 63/37 rosin-core solder is an excellent choice because of its reliability. Use SAC (tin-silver-copper) alloys for lead-free solder.

Why does solder stick poorly to surfaces?

This often occurs when a surface is previously oxidized or not enough flux is used. Make sure you use the correct flux and that all surfaces are thoroughly cleaned before soldering.

Can I solder without flux?

While in some unusual cases, soldering can be done without flux, most of the time using flux with solder will be more effective. The use of flux removes oxidation and aids in the flow of solder, thus providing for a good, clean bond. Without the use of flux, strong and reliable joints will be difficult to produce.

Conclusion

So, does solder wire require the use of flux? Not all solder wires require the addition of flux, as rosin-core solder wire normally has flux included in their formula. However, solid-core solder wire will require the addition of flux when using it. When choosing a solder wire for a specific project or purpose, please consider the material or type of solder wire you would like, type of flux, cost, and your need for solder wire to achieve the best results.

Soldering is a necessary skill used in electronic and electrical applications. By selecting the proper solder wire along with utilizing proper solder techniques, you will be able to create durable connections that last. For a beginner to soldering, using a high-quality rosin-core solder wire such as the 63/37 solder wire will allow you to have great success with your soldering projects. Happy soldering!