There are different types of solder available in the market. In this article, you will find all about them, their properties, and everything you need to know so that you can choose the right type of solder for your projects.
Let’s get started!
Solder is a metal alloy with a relatively low melting point commonly used to attach metallic objects. The solder is melted using a heat source like a soldering iron and flows through the parts being soldered.
Solder solidifies once the heat source is removed, creating a strong bond between them.
It’s important to highlight that solder has a lower melting point than the parts to be joined to prevent damaging them.
Solder is used for attaching different components or parts to form an assembly or connection.
There are different types of solder depending on the field you are working with. For example, the solder used for electronics is not the same as the one used for plumbing.
I will make a list of the most common uses of solder.
Solder is made of different metal alloys and, in some cases, may contain materials like rosin, flux, or other non-metallic substances. Tin and lead are the two commonly used material for solders.
The composition of solder varies based on its intended use and application. For example, solder used in electronics and electrical jobs needs to be an excellent electrical conductor, a characteristic that is irrelevant for applications like plumbing.
When talking about solder, most people immediately think of tin and lead alloys. However, with the passing of time and the evolution of technology, there are currently more than one hundred varieties.
For simplicity and practicality, I will focus on the most commonly used alloys and materials you can find at hardware stores. As an interesting fact, only in the aerospace and heavy industries, there are at least fifty special alloys designed for specific uses and functions.
Solder’s materials and composition usually have more incidence in the final melting point and its applications.
Lead was one of the main materials used to manufacture solder because of its low fusion point; however, in the past years, the awareness about its toxicity and environmental impact caused the appearance of lead-free alloys. In some countries, lead solder became a forbidden substance; in others, it’s still available, but more and more people are moving to lead-free alternatives.
Depending on where you live, you can still find tin and lead solders and, in some cases, a third material is added to improve the alloy’s overall characteristics. For example, silver or copper is added to improve the alloy’s conductivity, ideal for electronics, and antimony for plumbing applications because it adds hardness and mechanical stress resistance to the solder.
According to the composition, we can group solders mainly into types.
Below, you will find a list of the most common types of lead and lead-free alloys and their uses:
Tin-Lead: These alloys are represented by numbers in the format of 63/37. The first number indicates the percentage of tin, and the second is the percentage of lead in the alloy.
The most common ratios or proportions are:
Other popular lead-based solders are lead-copper alloys and trimetallic alloys, where a third element is added to obtain extra features.
Examples of trimetallic alloys are:
It’s important to consider that commercial lead-free solders have melting points from 5 to 20 °C higher than similar solders containing lead.
There are different ways to classify solder.
We have already discussed the different types of solder based on the alloy composition in detail in the previous section.
So, let’s see the other two types of solders.
Solder alloys are split into two groups based on their melting points.
Soft solder has a relatively low melting point, which goes from 90 to 450°C (194 to 842°F), and solder with a melting point above 450°C or 842°F is considered as hard solder. Soft solder is ideal for electronics and working with delicate or heat-sensitive materials, as it enables soldering without subjecting components to potentially damaging high temperatures.
Hard Solder: On the other hand, high melting point solder (or hard solder), is used for applications such as plumbing or automotive repairs due to its ability to withstand high temperatures and mechanical stress. Besides, hard solder is more malleable and, thanks to its longer cooling time, allows molding it while it’s being applied.
According to the American Welding Society, soldering involves using soft solder with melting points below 450°C or 842°F. Processes that require more heat than this fall into other categories, such as brazing or welding.
Considering that the most powerful soldering irons can reach up to 480°C (896°F), it’s essential to know the solder’s melting point before starting a new project.
Solder can also be classified by its core or the lack of it.
Solder comes in different shapes, depending on the application. It’s commonly sold in reels with a wire solder that comes in different thicknesses, being most common .05mm, .08mm, and 1mm.
Plumbers usually use much thicker solder, which is sold in bars.
Solder is also sold in thin sheets, ideal for jewelry making and other crafts.
When choosing the solder for your project, it’s important to consider its intended use, melting point, electrical and mechanical resistance, and practicality.
For example, if you are working on an electronic project, it’s important to check how much heat the components you are working with can endure so that you can make sure to use solder that won’t lead you to overheat them. In the case of plumbing, roofing, and copper soldering, where mechanical strength is key, you should choose a solder with excellent mechanical properties but with a melting point that matches your tool’s heating capacity.
As a rule of thumb, when working on electronics, choose a solder that provides reliable electric and mechanical connections with a melting point way below the components you are working with.
When working in plumbing and roofing, choose the hardest solder you can but within the limits of your tool’s heat output. If you have a proper torch, you won’t have a problem using any solder, and you can go for the hardest types.
When working in electricity, make sure to choose a solder with good mechanical and heat resistance.
Another thing to consider is the environmental and health factor; try to avoid lead-based solder when working in plumbing applications where the lead will be exposed to running water that you or others may end up drinking or may contaminate other water sources.
Besides, lead-free solder is safer since its fumes are not as poisonous and dangerous as lead-based solder.
While lead-based solder is sometimes better in terms of conductivity and ease of use, try to avoid it as much as possible.
Below, you will find a list of the most common soldering problems and their solutions.
This problem can be caused by several things.
First, make sure that you are using a soldering iron or heating source with enough heat to melt the solder. If you are using the right soldering iron, check the tip.
Oxidation and dirt act as insulators, preventing heat from reaching solder properly. If that’s the case, try to clean and re-tin your soldering iron’s tip and try again.
If that doesn’t work, check for damage on your soldering iron’s tip. It might need replacement.
If the tip is clean and in good shape and still doesn’t heat properly, check that it’s correctly plugged into the soldering iron’s heating element, mostly if you removed it recently for cleaning. Loose tips don’t make good contact with the heating element, becoming unable to heat solder properly.
If you are working with a high melting point or thick solder, pour some flux on the tip and try again. If none of this works, it may be time to get a new soldering iron.
The causes of solder not sticking can be the same as listed above, and besides, you should check some additional issues:
Ensure that the surfaces you are soldering are clean and rust-free. Dirt, corrosion, and impurities prevent solder from sticking properly. Also, check you are using the right type of solder for the intended application.
If none of this works, try using some flux to clean the parts and improve the solder’s efficiency.
Solder bridges can be formed due to excess solder on the soldering iron’s tip. This can be caused by an incorrect tinned tip, excessive solder, or using solder thicker than the component’s gap. Excessive temperature or humidity can also cause bridging issues; ensure not to overheat the parts or the PCB when soldering.
Another cause of solder bridges is using a thicker soldering iron tip than the gap between the components. Using a thinner tip may solve the problem.
A tip in bad shape can also cause solder bridges.
In other cases, mostly if you are building a project, it could also be a defect of the PCB, where the soldering pads are too close to each other. In that case, you can fix it using soldering masks, which are templates designed to prevent this problem.
There are countless types of solder and uses for it. However, if you get familiar with the parts or pieces you want to solder, finding the right solder for your application becomes much easier.
When it comes to electronic use, I always recommend 63/37 solder with rosin core; it provides excellent results and is easy to use and find.
For plumbing and roofing applications, I think choosing a lead-free solder is the best way to go, to care for your dear ones, other people, and the environment, besides avoiding contaminating water sources.
For applications like stained glass, you should use solder that matches the foil or lead came you are using; in both cases, remember to use flux to improve your joints.
Remember to follow the safety precaution listed in this and other of my soldering articles to prevent accidents and injuries, and remember that although it seems a simple task, it involves heat, fumes which usually are dangerous for your health, and in most cases, electricity, so solder responsibly.
Remember to keep your soldering iron clean for a pleasant and trouble-free soldering experience. Don’t rush; take your time and make sure to have everything ready before starting soldering and remember, like in any other jobs, when you solder, the more you rush, the slower it goes.
David Castillo is an automotive industry expert specializing in vehicle electronics and stand-alone fuel management systems. He has over 20 years of experience and owns a car repair garage and tuning shop.
David still runs his shop but is now more focused on pre-purchase car inspections and writing for FinePowerTools.
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