How Strong is Solder

How Strong Is Solder? [Everything About Solder]

You’ve decided to solder your electronics to establish a connection. But you have some confusion about the strength and durability of the solder. You want to know if solder is strong enough for such work.

The question is, how strong is solder?

Solder is very strong and capable enough to hold heavy metals together. The strength of solder is measured by its tensile strength. For Silver solder, the tensile strength can range from 40,000 to 70,000 psi(pounds per square inch).

The properties and strength of solder vary depending on its filler alloy components and their proportions. High-duty solder requires higher temperatures to melt and bond.

Keen on learning more? Read this article about different types of solder and their difference in strengths.

What Makes Solder Strong?

Solder is a melted combination of tin and lead, making it a great alloy for joining heavy metals.

You can use soldering to join different types of metal together by melting solder. Solders can hold metal and secure them together to create solid metal joints. Thanks to it’s bonding strength, it’s gotten popular in the RC communities.

It helps to connect components with each other and builds an electrical connection. In fact, a lot of technical works that require joining metals prefer solder as the joining agent.

That leads us to question,

Is solder strong?

Yes, Solder is a strong alloy capable of holding heavy metals together. Solder has a high tensile strength that makes it durable and capable of holding heavy metals against each other.

Now, the next thing we all want to know is how solder works to form such powerful bond.

Solder alloy is melted beyond its melting point (600 degrees Fahrenheit) before cooling down to create a strong bonding material. It is melted using a temperature controller. Once the melted solder is cooled down, it creates the soldered joint.

To understand solder better, let’s look at some of the notable properties of solder:

Filler Materials

Tin, lead, cadmium, zinc and indium are the primary filler materials used to form the Solder alloy. The presence of the fillers are tweaked in solder depending on its application. The strength, durability, and solderability highly depends on the alloy fillers used in it.

The leads and tins in solder are melted using hot iron that are initially transformed into an alloy possessing strong electrical bond onced cooled.

Generally, your typical solder contains about 50-70% tin, 30-50% lead, and the rest are consisted of copper, antimony and other metals. Modern solders usually avoid using lead and instead, looks to possess about 99% tin and .75% copper. This ratio and filler metals can change depending on the type of soldering.

For example, silver solder possesses about 65% fine silver, in addition to 20% copper and 15% zinc.

Tin is used in solder for its low melting point. On the other hand, lead is preferred for prevent the growth of tin whiskers. A higher concentration of tin in solder ensures better tensile strengths.

Temperature

The melting point of solder can vary from the range of 90 to 450°C(200 to 840°F).

This means that depending on the alloy composition, the melting point of solder can be as low as 90°C(200°F) to 450°C(850°F) at maximum.

For better understanding, here’s a solder melting temperature chart showcasing the different melting point for different kinds of solder:

Solder TypesMelting Temperature
Soft Solder200°F-840°F
Silver Solder1490°F-1760°F
Brazing840°F
Lead-Based Solder361°F
Lead-Free Solder422°F
Melting Point for different Solder types

Now, let me explain the table:

As we can see, based on the solder type, the melting point differs. Silver solder melts within 1490°F and 1760°F. Brazing on the other hand, melt easily above 840°F.

Lead-based solder melts over 361°F, which is actually lower than the lead-free solder which melts over 422°F temperature.

Conductivity

Just like the melting point, the conductive properties of the solder depends on the ratio of the metals present in it.

Here’s a chart of the difference in electrical conductivity of different solders:

SoldersElectrical Conductivity
Soft Solder9-13%
Silver Solder20-40%

The electrical conductivity of soft solder is less in comparison to silver solders. A soft solder has an electrical conductivity range of 9 to 13 percent. Whereas, you can expect about 20 to 40% of electrical conductivity from silver solders.

Liquid solders can also create a conductive joint between metals and establish an electrical connection. A great example of it is solder paste. This is possible due to the liquid solder possessing a fair amount of metals in it.

Again, all this depends on the variation of the composition.

Different Types of Solder

Based on the material properties and presence of different metals, solders are mainly classified into 3 different types:

  • Lead-based solder
  • Lead-free solder
  • Flux

I’m going to go through them one by one and explain them in detail:

Lead-Based Solder

The lead-based solder have a blend of 60% tin and 40% lead alongside some other minor amounts of metal. The melting point of lead-based solder lies around 361°F.

The lead-based solder is often referred to as the 60/40 solder, or more recognizably as the soft solder. This is the most common solder composition used worldwide and is widely popular for its ease of application.

Lead-based solders used to be the most popular solder due to being very cheap.

However, leads are toxic substance and can be dangerous for human health. Dust and fumes produced from lead-based soldering can result in occupational asthma and severe irritations.

As a result, modern soldering avoid the use of lead-based solder and opts to go for different options.

Lead-Free Solder

The lead-free solder started gaining popularity after EU restricted the use of lead in consumer electronics.

Lead-free solders is the composition of tin, copper, silver, nickel, bismuth, zinc, and an assortment of other metals.

Lead used to be an effective metal to prevent the tins present in the solder alloy from growing whisker. But now, with the implementation of modern techniques, inclusion of nickel and conformal coating can do the same job.

Unlike the lead-based solder, lead-free solders have a higher melting point, being above 422°F.

Flux

Flux helps to reduce the reverse oxidation of metal to provide thorough electrical connection. It helps in both soldering and desoldering by removing the oxide coating that forms on the metal surface.

Not only that, but flux also eases the solder’s wetting ability, making it flow uninterruptedly without facing any resistance.

Flux is known as Rosin in electronics. It’s actually a great option for joining electrical wiring and other such components.

However, flux colored solder has a very short shelf life. How long the flux will last is determined by the alloy used in the solder. Alloys consisting of 70% or higher ratio of lead will make the shelf life approximately 2 years long from manufacturing date.

This is pretty much low compared to other alloys that have 3 or more years of shelf life.

Many often confuse flux as solder paste. While solder paste is used to glue metal alloys to each other, flux is more of cleaning agent that’s added to the metal surface before applying solder paste. Flux increases the effectiveness and longevity of the solder paste by making the surface clean and contamination free.

Using the flux is not mandatory in every soldering case. But you can make the soldering surface cleaner by using solder flux.

Application of Solder

Soldering is used in electronics, plumbing, and other metalworks. It’s even employed in jewelry! But recently, there has been another sector where soldering is getting popular every year. And that’s RC Cars!

Gold, silver, brass, iron, and copper are the metals that can be soldered. The fillers melt to create highly strong joints.

In electronics, Soldering is used to solder copper to printed circuit boards. For plumbing, plumbers use solder to connect copper pipes.

Electrical works that need precision require soldering. For example-soldering bullet connectors with wires to establish electrical connection.

On the other hand, stronger soldering is used in joining jewelry components and plumbing. Whatever the use, no one can deny how strong and effective it is at its job.

Now, what does solder stick to?

Solders stick to flat metal surfaces, such as tin, copper, lead, brass, and bronze. How effectively you can solder depends on the solderability of that particular alloy/metal. You can increase the effectiveness of the solder by using flux on the metal surface before going on with the soldering.

Not all alloys will accept solders that easily. For example, take aluminum.

Unlike other metals, solder won’t stick to aluminum that easily. Heating up and melting the solder is not enough to make it stick to the aluminum surface. The aluminum itself has to be hot enough to let the solder alloy sit on it.

Another similar case is steel. You can solder steel and stainless steel. But for that, you need to follow specific techniques to make the solder stick to the steel surface.

That’s why people prefer brazing or welding over soldering for such types of metal surfaces.

Different Kinds of Soldering

Let’s have a look at some of the common soldering types:

Soft Soldering

This is the most commonly used soldering when it comes to making electrical connections. The solder joint itself has almost no mechanical strength.

It is also widely used as the iron for soldering RC car connectors to batteries. 

Silver Soldering

It is a stronger option than soft soldering and is used in plumbing and jewelry materials. But it can also be used in joining copper, brass, and gold together.

Brazing in High Temperature

Brazing requires much higher temperatures than soldering iron and gives much stronger joints.

The filler metal in brazing is stronger than that of silver and soft solder. These solders are formulated primarily for their strength. 

It’s time to compare the solders side-by-side- 

 SolderingSilver SolderingBrazing
Melting Point200°F-800°F1200°F-1436°FAbove 840°F
ApplicationsElectronics, plumbing, sheet metal work., Jewelry, silversmithing, plumbingBonding dissimilar materials due to the different melting points.
Tensile StrengthAround 8,000 40,000-70,000 psi110,000(average)
Permanence of JointsSemi-permanentSemi-permanentSemi-permanent

Note: Tensile strength may vary from different external factors.

Soft leads are the primary ingredients of soft solder. It uses the lowest temperatures and in doing so, stresses components the least thermally. But it also fails to make strong joints in the process.

The soft solder is also highly unsuitable for high-temperature applications due to its low melting point. Thus, losing its strength and melting eventually. So it is perfect for lightweight operations, like connecting an ESC to a receiver in an RC car.

Silver soldering requires a high-temperature source due to being stronger than soft soldering. It also greatly dominates in tensile strength, making it capable of building strong joints.

Brazing ultimately dominates the rest due to its high melting point and strong, durable bonding properties. The brass alloy offers the most tensile strength among all other solders.

How to Make Solders Stronger?

Tweaking the proportion of the alloy constituents to an optimal value can make the solder stronger. As most of the properties of the filler metal influence the strength of the solder.

Rods, ribbon, powder, paste, cream, and wires are generally used as the components of the filler alloy for brazing. Compared to tin and copper used in soft solders, the filler alloy of brazing is stronger.

Besides filler alloy, the temperature and the solder’s ability to wet surfaces impact its strength too.

Industries prefer welding over any form of soldering to join their metals. Welding gives a permanent and the strongest bond compared to all solders. It is used for heavy-duty industrial repairing and construction.

Although welding provides a stronger bond, soldering is preferred over it for its electrical conduction properties.

FAQs

What is the easiest metal to solder?

Answer: Tin, cadmium, gold, silver, palladium, and rhodium are the most solderable metals out there. They are easier than any other metal to solder.

Does silver solder go bad?

Answer:  Silver solder doesn’t go bad. It might get a bit tarnished over time. But If fluxed and soldered properly, the silver solder doesn’t have any effects on it.

Question: Does solder stick to all metals?

Answer: Almost all kinds of metals can be soldered. But their solderability will vary depending on their properties. Some metals will be harder to solder than others.

EndNote

We now have a clear understanding of how strong is a solder. Now you can choose the perfect solder and soldering technique suitable for your operation.

We hope that this article proves helpful to you in the future when dealing with soldering.

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