HowTo: Electronics – Solder THT components by hand

Soldering THT components (THT = Through Hole Technology) is one of the basics you need to build kits, prototypes and the like. This is because many electronic components, especially ICs, are still available in this "through-hole" version.

Modern/new components in particular are often only used as SMD variant Nevertheless, this assembly technology is indispensable - especially in the DIY sector.

The following article describes what you need to consider when assembling PCBs with THT components and how to proceed.

Safety instructions

I know the following notes are always kind of annoying and seem unnecessary. Unfortunately, many people who knew "better" have lost eyes, fingers or other things due to carelessness or injured themselves. Data loss is almost negligible in comparison, but even these can be really annoying. Therefore, please take five minutes to read the safety instructions. Because even the coolest project is not worth injury or other trouble.

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Helpful articles:
You can find more helpful information on the basics of soldering in the following article:
Electronics - My friend the soldering iron
Electronics - Solder connections, clean and remove components

Required material:

In the following list you will find all the parts you need to implement this article.

Required tool:

In the following list you will find all the tools you need to implement this article.

General procedure

The general procedure for soldering THT components can almost be summarized as a general rule.

  1. Insert the component from above - i.e. the side with the placement print - correctly oriented through the PCB.
  2. Fix the component. In most cases, a small strip of sellotape/adhesive tape is sufficient for this. Sometimes you can also bend the legs slightly apart on the underside.
  3. Turn the circuit board over and solder (only) the first contact to the circuit board.
  4. Check the correct orientation of the component again. (An error has been quickly corrected at this point).
  5. If necessary, heat the solder joint again to align the component properly.
  6. Solder the remaining contacts.


To be added.

JST sockets

JST sockets are basically just reverse polarity protected and latching connectors. They are available in various pitches and as THT or SMD components. This example shows how a JST connector is assembled as a THT component.

View of the JST connector with associated mounting location on a printed circuit board.
In order for the JST connector and its pins to be soldered, they must first be positioned on the corresponding mounting location and the pins inserted through the circuit board.
To prevent the JST connector from falling out when the circuit board is turned over, you should now secure it with a small strip of adhesive tape.
Then you can turn the circuit board over and...
...solder the first contact of the JST connector to the circuit board. It is important that you only solder one contact at first, because... you can check whether the component is mounted straight by viewing it from several sides.
The plug should therefore lie flat on the circuit board.
If the connector does not lie flat, you can briefly heat the first soldered contact again to position the component correctly. This will be considerably more difficult if you have soldered more than one contact right at the start.
If the JST connector lies flat, you can solder the remaining contacts of the connector to the circuit board.

Pin headers

Pin headers are basically the big brother of JST plugs/sockets. Compared to these, they only have the disadvantage that they are not reverse polarity protected and the connectors on the pin headers do not lock into place.

Pin headers are available in both THT and SMD versions.

However, soldering the pin headers is just as easy as soldering the JST connectors.

View of the pin header with the corresponding mounting location on the PCB.
The pin header is inserted through the PCB from above.
The pin header should be inserted vertically through the circuit board and lie flat everywhere.
Before you can turn the circuit board over, you should secure the pin header with a small piece of adhesive tape to prevent it from falling out.
Then you can turn the board over and ...
...solder the first contact of the pin header to the circuit board.
As with the JST connectors, you solder the remaining contacts on the pin header later, because...
...first of all, you should check that the pin header is perpendicular to the PCB and lies flat everywhere. If not (as in the case shown), you can briefly heat the solder of the soldered contact again and align the pin header correctly while the solder is soft/liquid.
The pin header should then be inserted into the circuit board as shown.
Especially in the longitudinal direction, it is important that the pin header stands upright on the PCB.
Now you can start...
... also connect the remaining contacts of the pin header to the circuit board.
This should then look something like this.
Other view.
Other view.

Tub plug

Tub connectors are another relative of pin headers. In principle, as the name suggests, these connectors are pin headers that are surrounded by a kind of "trough". These are used in particular in conjunction with flat cable connectors. These can be plugged into the tray connectors to prevent polarity reversal.

Illustration of the tub connector including mounting location on the circuit board.
To solder the tub connector, it must of course first be inserted into the circuit board.
The tub plug should then be secured against falling out with a piece of adhesive tape.
Now you can turn the circuit board over and solder the first contact to the circuit board as you did with the simple pin header.
Before you solder the remaining contacts, a possibly crooked tub connector should be... straightened.
Then you can also add the remaining contacts...
...completely soldered.

Post bushes

To be added.


Many of the ESP8266 boards are available either as a version with a pin header (for example on a Wemos D1 Mini) or as an SMD component. In the first case, you can solder the ESP8266 or its pin headers like a normal pin header. The soldering of the second case - i.e. as an SMD component - is described in the article Electronics – Solder SMD components by hand under the paragraph ESP8266 ESP-12 described.

IC sockets can save IC lives

Especially when soldering ICs in DIL housings, there is a small but simple tip that can save you a lot of time and effort if the worst comes to the worst. For each type of DIL housing there are suitable sockets that can be soldered in place of the IC. The desired IC is then plugged into these sockets later.

Should a defect occur in the IC in question, it can simply be replaced. So you save yourself the trouble of unsoldering and re-soldering. In addition, the probability that you will destroy or damage the IC due to excessive temperatures during the soldering process is virtually zero.

The (low) additional material costs for the IC socket are therefore worthwhile in any case.

Top view of an 18-pin DIL IC - also known as DIL-18 - including matching socket.
Side view.
Side view.
18-pin DIL IC including matching socket on a breadboard. The "notch" on the right-hand side, which makes it easier to orient and align the component, is also clearly visible here.
To solder the IC socket to the circuit board, it must first be soldered in the right place.
... through the breadboard. Make sure that the socket is correctly aligned. This also means that the notch on the narrow side of the socket is on the correct side. This will make it easier for you to insert the IC itself in the correct orientation later on.
Usual procedure: To prevent it from falling out when turning the breadboard, the base must first be fixed in place with some adhesive tape.
The breadboard can then be turned around and...
...the first contact must be soldered.
A possibly crooked socket can be "straightened" slightly at this point. To do this, briefly heat the solder of the already soldered contact again and align the socket correctly.
As soon as the IC socket is straight and correctly aligned, can get another and...
...solder the remaining contacts of the socket to the breadboard.
Once you have completely soldered the IC socket, it should look something like this.
The IC can now be inserted into the socket. The IC should be fully inserted into the socket so that it does not fall out in the event of vibrations.
Side view of the inserted IC.

THT push-button

Soldering THT push-buttons is particularly easy. This is because they snap into place so well when they are inserted at the mounting location - thanks to appropriately bent contacts - that they are already aligned and can be soldered directly.

View of the push-button next to its future mounting location.
To solder this, the push-button is first plugged into the circuit board at its mounting location.
Make sure that the push-button rests "up to the stop" and straight on the circuit board. In this position, it should be firmly stuck in the circuit board due to the slightly clamping contacts. At least tight enough to prevent it from slipping until it is soldered.
Now you can turn the circuit board around and...
...solder the first contact of the push-button.
At this point, check again to make sure that the push-button is straight.
If everything fits, you can also solder the remaining contacts.
Side view of the soldered push-button contacts.

SMD push-button

The soldering of SMD buttons is described in the article Electronics – Solder SMD components by hand under the paragraph SMD push-button described.

5mm and 3mm LEDs

To be added.

Closing and opening solder jumpers

Solder jumpers are a great way to add modifications or adjustable options to the PCB in advance without giving up the "professional look".

Later, various options and settings can be activated or deactivated by opening or closing this soldering jumper.

The solder jumper is closed by placing or removing a solder bridge over its two contacts.

View of the - still open - solder jumper "SJ4".
To close this, you should first apply some solder to the first and ...
...then "apply" to the second contact.
These two contacts can then be connected very easily by heating both contacts with a soldering iron and fusing them together.

Further information

Have fun with the project

I hope everything worked as described for you. If not or you have questions or suggestions please let me know in the comments. I will then add this to the article if necessary.
Ideas for new projects are always welcome. 🙂

PS Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you think it's cool that I share the information with you, I would be happy about a small donation to the coffee fund. 🙂

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