The Best Solder For Circuit Board - How To Choose?

Because of the many types of solder in the market, choosing the right one can be confusing. While you are out there looking for a solder make sure you know the exact use and the type of work you are about to undertake. So how do you choose the best solder for your custom circuit board?


WellPCB knows the importance of having a solder suited to various temperature ranges and applications. Choose the best solder for circuit boards, and you'll get the electrical connections you need. But how to choose? Quickly come with me to read this article!

1、What is the Solder?

Solder is a metal alloy that is fusible metal made of an alloy used to create strong and permanent bonds on circuit boards. Identifying the best solder for circuit boards is by understanding what it is and how best to use it.


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The type of solder used in electrical bonding contain different materials with the most common one composed of 60% tin and 40% lead, thus the name 60/40 solder. There are two dominant types of solder.


•  The lead-based solder


•  The lead-free solder


Next, we'll take a closer look at the solder used for the board and the differences.

2、Board Best Solder Category

The three significant categories of solder suitable for your circuit board:  


•   Lead-based solders


•   Lead-free solders


•   Silver alloy solders


The defining difference between the three is the melting temperature, from this difference and the kind of work at hand, choose the one that appeals to you.


2.1  The Lead-based Solder

The lead alloy solder has been industry standard for a long time. It contains a mixture of tin and lead in the percentage of 60/40. The melting temperature for this compound is between 180-190 degrees Celsius.


The tin in this alloy mixture is to lower the melting temperature because the circuit boards are sensitive to high temperatures.


Lead is poisonous when inhaled for a long time, and that is why the European Union is encouraging you to think about alternatives to lead-based solders. It is a solder without the lead. Several standardization bodies require that we use lead-free solder because of the dangers posed by lead. However lead-free solder has a higher melting point and difficult to work with but by far better if you consider the health issues related to lead poisoning.


It is thought to form stronger joints compared to the lead-based solder because naturally, tin is strong and hard. Tin needs around 380 degrees Celsius to melt and may take some seconds longer to cool leaving shiny and clean solder joints.


Wrongful handling of lead in a soldering environment may lead to exposure from lead fumes. Some of the possible health effects are reproductive problems, digestive problems, muscle pain, joint pain, and concentration problems. All these health risks are brought about by either ingestion or inhalation.


2.2  Silver Alloy Solders

The silver alloy solder could be a combination of lead or no lead at all. Silver was added to the alloy to prevent silver migration that takes place when silver plated components are soldered.


When you use silver alloy solder, it will leach out the joint giving it a brittle and weak joint. Common lead alloy with silver has 2% silver, 62% tin, and 36% lead. The mixture will limit the silver migration effect with better overall properties than lead alloy solder, which has led to an increase in its cost.


So how do you choose solder for your board? What factors should we pay attention to? Then please read on.

3、Things to Consider When Soldering for Circuit Boards

Different kinds of soldering irons are in the market to serve different types of soldering jobs. Some irons release intense heat and ensure that the soldering joint quickly melts the bonds. Here are some of the things to consider when choosing the best solder for circuit boards.


3.1  Wire Size

The solder wires are available in a variety of sizes otherwise known as gauges. The diameters range from inches or millimeters. The wire size depends on the work at hand; therefore, it is better if you can have both bigger and small lead wires the better.


3.2  Flux

Flux helps the flow of solder and sticking it to the surface. It is slightly acidic and removes any oxidation from the board’s surface. Most of these wires are sold with rosin flux, which is at the center of the wire.


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Flux cleanses the area to be soldered making it easier for the solder to flow and hence a perfect solder joint. The flux will change the surface tension as it increases adhesion properties in the solder joint.


Flux is available in three different forms:


•   Water soluble


•   Rosin-based


•   No-clean


You can minimize solder inventory by using the water-soluble flux for circuits making cleaning a simple and straightforward process.


Rosin core flux wire should be enough, but it is nevertheless helpful to have separate flux. You only need to add a bit of flux to the surface of the soldering point is useful because leaving it on top of the soldering iron.


3.3  With or Without Lead

The debate on what solder alloy to use on circuit boards because the discussion on whether to use lead or lead-free solder is still going on. Despite the debate grounded on environmental and health issues, some individuals seem to use them without any issue at all.


Here are some of the issues that surround the use of lead-based solders:


Technique: solders made from tin alloys need proper technique to obtain the best results. With the same procedure, you will still get good results.


Equipment: failure to use the right soldering iron tip matters a lot because it goes as far as the temperature regulation.


Quality of Materials: Regardless of the nature of the materials used to some extent, make sure that how you use the solder, nobody gets in harm's way. Sometimes it may be solder, but the quality may have come from recycled materials that have been used. In such circumstances, the problems may not be caused by alloy but impurities from the materials.


If you have been soldering for quite some time now, you must have realized lead-free solder alloys have an excellent reputation in the market. For a beginner and anyone using a cheaper soldering iron then the 60/40 or 63/37 tin-lead solders. Therefore, the best advice on the type of solder to use as the best circuit board is any solder that is lead-free and with a flexible resin core.


If you decide to opt to check via the manufacturer website, look for a datasheet that has all the details of the standard solder, where testing was done to prove that what you choose to buy is the recommended solder for your type of circuit board.


You can make the final decision on the type of best solder for your circuit board that can either depend on whether the alloy has some composition of lead. Remember that what you need is the soldering technique.


You may be tempted to throw away some of the lead components because of the fear that is a danger to the environment. Throwing electronic waste away may not solve the immediate issue; however, switching to the lead-free soldering components could be the safest bet.


Now we know what to pay attention to when choosing solder. Next, let's see how to choose the right solder.

4、Tips When Selecting the Right Solder

Choosing the right solder is daunting for most beginners and to some extent the experienced hands as well. Let us share some ideas that will make the process less tedious so that you can make an informed choice. Look at the following ideas:


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4.1  Diameter

You have to know the size of the diameter needed before handling the work on the table. A small diameter solder is favorable for small amounts of solder and is very handy for soldering surface mounted circuits.


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Larger components such as connectors use a longer solder to get to the exact point of connection. The larger size also extends risk to nearby circuits and overheating some board components.


4.2  Shelf Life

Solder does expire, and industry recommendation dictates that it be used within three years from the date of manufacturing. The shelf life is indicated on the solder paste. After some time the oxidation may take place on the surface of the solder rendering it less effective.


After oxidation takes place, there will be no smooth flow and soldering the joint becomes too difficult. A solder paste has a shelf life of six months. You can extend the shelf life of the paste by refrigerating it, and it may serve you for more than one year. You have to make sure that soldering paste cannot be stored in the same fridge that is used for food storage.


We anticipate that the information shared in this article gives an overview of solders that are available in the market. You have also read about the difficulty involved in choosing the best solder for circuit board. After reading the article to this point, you can be assured that selecting the best solder for electrical work in not as difficult as earlier thought.


WellPCB provides you with better service to meet customer needs. Such as we need to choose the most suitable solder for your board, and rest assured that you will get good electrical connections and have a joint that will last for many years. Every item must be tested and qualified, and every detail is strictly checked. If you need PCB assembled, please contact us, we will be happy to help you.

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