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What are the Best Practices of PTH Soldering?

Pin through hole or PTH is used in defining the processes through which the legs or leads of an electronic component is inserted via some designated holes which are inside the PCB and then soldered using some soldering techniques. The process is called conventional assembly.

Furthermore, the formed solder joint is extremely strong as this component is usually soldered via the printed circuit board in contrast to the SMT component soldered onto the CB surface only. The technology has been used in manufacturing products whereby space isn’t an issue. For example, in early computers, TV manufacturing, etc, it was necessary for strong interconnections to happen between the circuit boards.

What Does Solder Mean?

Before you learn soldering, it is advisable to learn about solder, understand its history, as well as the terminology used when discussing it. As a word, solder is useful in two main ways. The noun form, Solder, describes the alloy (which is a substance made up of at least two metals) which typically comes as a thin, long wire in tubes or spools. The verb form, solder is the act of joining two metal pieces together in a solder joint. Therefore, we solder using solder!

The skill of soldering is a very important skill required when venturing into the electronics world. Both of them work hand in hand. Although you can learn about electronics and build them without having to pick a soldering iron, soon, you’ll discover that there is a new world created with this skill.

Lead-free vs Leaded Solder

One important thing to take note when referring to solder is, traditionally, the main constituent of solder is lead, tin, and some trace metals. The solder is referred to as leaded solder. Humans have now learnt that lead is harmful and could lead to poisoning if exposed to huge amounts. Sadly, lead is an important metal, and is the best metal when it comes to soldering. This is because its melting point is low and it can create the best solder joints.

Knowing fully well the negative consequences of leaded soldering, some individuals and nations took the decision that leaded solder wasn’t to be used anymore. The EU, in 2006, adopted the RoHS directive. This directive restricted the utilization of leaded solder in electrical and electronics equipment. With this, the utilization of any lead-free solder was now the electronics manufacturing norm.

The lead-free and leaded solder is very similar. The only difference is seen in its name; the lead-free type has no lead in it. Rather it is composed of tin and trace metals such as copper and silver. Normally, the solder is marked with a RoHS symbol. This notifies potential buyers that it conforms and works in line with the standard.

Best Practices of the PTH Soldering


You will become better at soldering with repetition. The best place to begin is through-hole soldering because the holes and leads of the components are larger compared to that of the surface mounts and you can work with it easily.

First, you need to equip yourself with great soldering materials and tools. Your soldering iron has to be comfortable and easily maneuvered. Also, make use of solder designed for printed circuit boards. The rosin core solders are the best when making sure that applied flux is very consistent with your solder.

Also, make sure that the surfaces of the metal you are soldering are clean and contaminants-free. Majority of these usually clear off easily, but some might need industry-approved cleaners to be removed. Once done with all these, you can begin the soldering process.

PTH Soldering Process

  • Begin with the melting of some solder at the soldering iron tip. The step would help in conducting the needed heat.
  • With the insertion of the component leads via the board’s hole, hole the tip of the iron well against the hole and the lead.
  • For some seconds, ensure the iron is kept in place to thoroughly heat the hole and component leads thoroughly; however, be careful so the board doesn’t get burned because you have waited too long
  • Next, feed some of the solder onto the iron tip and heated surfaces until much of the solder is added to create great joints. The solder has to fill up the hole, thereby creating a filet round the lead.
  • Immediately after melting the solder, take out the iron and then let this joint cool down for some seconds. Now, it is very important that you don’t stress this connection till it is properly cooled. This is to make sure that great solder joints have been formed.

The best way you can learn PTH soldering is by desoldering. There are reasons why you have to desolder: salvage, upgrade, repair, etc.  If you are not sure if your newly-created solder joints are making electrical connections, then you may use multimeters to carry out a continuity test.

These guides above will go a long way in creating a great connection. However, good soldering will also depend on the placement of these parts.

What are the Issues Usually Encountered During PTH Soldering?

Generally, through hole components are larger compared to the SMD components. However, this doesn’t indicate that PTH soldering is something easy to handle. There may be some issues and obstacles during PTH soldering, this depend on the individual’s skill as well as the manner in which the design of the PCB was handled.

Finding it difficult to place the PTH components on the footprint is strange. This only indicates that the pad’s hole created is too small. Also, when the hole is too large, this will make the component loose whenever you are slotting it in. This type of situation will happen whenever the components are generic parts and where the person isn’t guided on the footprint dimension recommended.

Also, you might face issues during the soldering of the pin to the pad. When the annular rings are extremely narrow, you’ll discover that this solder faces some issues with holding to the pad. Also, excessive heating might tear the pad off from the base of the PCB.

However, this isn’t the end of the horror issues with respect to PTH soldering. Ground pins are known to dry or crack the solder joint. This is because the connection of the pad is done to the ground plane. Also, the heat quickly dissipates before the formation of the solder joint.

One reliable way of overcoming possible challenges with PTH soldering as well as hole desoldering is by learning of the possible pitfalls that could happen with both processes.

Optimizing the PCB Design for the PTH Soldering Process

Though it is true machines are now handling the soldering processes of most components, there are some of these components that are soldered manually. This holds true when the printed circuit board houses the SMD components on the two layers.

Whatever way, this practice is great for optimizing the PCB design to achieve through hole soldering. To begin, make sure that the annular ring and hole size are adequate for inserting the physical pin and soldering it. Work with the dimension that has been recommended by a component manufacturer.

During the application of the ground plane on the through hole components, make sure the provision for the thermal reliefs are set up. With thermal reliefs, the ground plane would be prevented from connecting onto the pad in the full circumference. Rather it connects onto the pad with about 2 to 4 thin copper traces. With this, heat is prevented from dissipating very quickly as well as creating joint problems.

In order to maximize efficiency, attempt to place all the SMD components on one side of your through hole components. When you do this, it will allow these components to be soldered with a machine rather than having to undergo a more expensive process of labor soldering.

PTH Soldering Tools

desoldering gun

Below are some of the tools used for PTH Soldering

Soldering Irons

Soldering entails so many tools. However, none of them are as important as the soldering iron. No matter the case, you will need an iron at least and some solder for accomplishing the task. Furthermore, soldering irons appear in different form factors which range between simple and complex. However, they usually function at the same time.

Solder Vacuum

This is also called the solder sucker. This tool is great for taking out solder that is left in the through holes during the desoldering of components.

Solder Wick

The solder wick functions as the soldering pencil’s eraser. Whenever you are dealing with problems like jumpers or removing parts also called desoldering, this solder wick is usually very useful and important. Solder wick, also called desoldering braid, is made up of a thin copper wire that is braided together.


Flux can be described as a form of chemical agent, which aids in lead-free solder flow. The flux pens permit the dabbing of stubborn components with a liquid flux in creating solder joints that are better looking. This is necessary for the cleaning and removal of any water soluble flux remaining on your board.


We hope you understand the processes involved in PTH soldering. If you have issues understanding any of the information above, please reach out to us.

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