How to Solder Circuit Boards

This article focuses on pcb soldering for beginners and explains how to solder various components using several different techniques. Although pcb soldering may seem daunting at first, once you give it a try, you will find that it is easy to do in most applications.

Manual solderingtools

Electric iron, ferrochrome frame
A soldering iron is a handheld tool plugs into a standard 120V AC outlet and heats up with melted solder around an electrical connection. For beginners, it is recommended that you use a pen soldering iron in the 15W to 30W range. Most soldering irons have interchangeable tips that can use for different soldering applications. Be very careful when using any soldering iron, as it can heat up to 896′ F, which is very hot.

A soldering iron holder is very practical and convenient. The holder helps prevent the hot soldering iron tip from coming in contact with flammable materials or causing accidental injury to your hands.

identification of circuit board components

Conditions of soldering

Components must be weldable
The soldering pads of the component shall be kept clean
Appropriate using the flux
Appropriate soldering temperature
Suitable soldering time

The solder

Tubular solder wire
Antioxidant solder
Silver solder
Solder paste

Selection of flux

Flux can improve the soldering performance, common fluxes are:
Solder paste/oil: Solder circuit boards is corrosive and can not be used to sold electronic components and printed circuit boards. After soldering, the residual solder paste/oil should be cleaned up.
Rosin:Rosin should be used as a flux when the pins of the components are tin-plated.
Rosin solution: If the printed circuit board has been coated with rosin solution already, then there is no need to use flux when soldering.

Soldering steps

Prepare for soldering: In the process of solder circuit boards,the left hand holding the solder wire, the right hand holding the iron, the iron head is required to keep clean, and the surface coated with solder.
Heating: Heating the whole soldering part is heated, sustain about 1 ~ 2 seconds.
Feed the soldering wire: When solder circuit boards, the soldering points of the component are heated to a certain temperature, then can feed the solder wire to contact the solder pads.
Remove the soldering wire: When solder circuit boards, the wire is melted for a certain amount, immediately remove the wire in the direction of 45° to the left.
Remove the soldering iron: After the solder is melted in solder pads and the soldering parts, move the soldering iron to the upper right 45° to end the soldering.

Notes for circuit board soldering

When solder circuit boards, the PCB shall first check its appearance to see whether there is any short circuit or open circuit, and then compare the schematic with the silkscreen layer of PCB to avoid any discrepancy between the schematic and PCB.
The components are classified according to their size for the convenience of subsequent soldering.
Before solder circuit boards, wear an anti-static ring and other anti-static measures to avoid electrostatic damage to components.
The chips before solder circuit boards to ensure that the orientation of the chip is placed correctly.
Distinguish positive and negative electrodes for LEDs, tantalum capacitors, and electrolytic capacitors.
For crystal oscillator, passive crystal has no positive and negative requests, and generally only two leads, active crystal generally has four leads, should distinguish the positive and negative when solder circuit boards.
For plug-in components, the pins of the components can be trimmed before soldering.
If any component packaging error, installation problem, incorrect pad design, and other problems are found in the solder circuit boards process, record them in time for subsequent improvement.
After solder circuit boards should use a magnifying glass to check the solder joints, check whether there is a poor soldering or short circuit.
After the completion of the circuit board soldering, the surface of the circuit board should be cleaned.
To keep the iron head clean, the iron head is in a high-temperature state for a long time when solder circuit boards.
The tin-plated parts of the components shall be heated evenly during solder circuit boards to avoid damage or hidden dangers that are not easily detected.
Do not move the components when solder circuit boards. It is necessary to remove the tweezers after the solder is solidified, otherwise, it is easy to cause poor soldering.
The evacuation of the iron should be timely, and the angle and direction of the evacuation are related to the formation of the solder joint.
The correct amount of solder. Generally, the diameter of the solder wire should be slightly less than the diameter of the solder pad.
The correct amount of flux should. Excessive use of rosin flux, after solder circuit boards, is bound to need to erase the excess flux, and prolong the heating time, reduce the solder circuit boards efficiency.

Circuit Board Soldering Skills

First, the correct use of electric soldering iron

1, Should apply the solder on the electric iron before using it.

2, The soldering time should not be too long, otherwise, it is easy to damage the components.

3. After the completion of soldering, to use alcohol to clean the residual flux on the circuit board,

4.The electric iron should be placed on the ferrochrome frame.

Second, correct soldering sequence

To facilitate soldering and save time, the soldering sequence of components should be difficult first, low first, and SMD first.

1. Difficult components first, if the difficult components, such as the integrated chip with dense leads, are placed in the last soldering, once the soldering fails, the soldering pad will be damaged. So there should solder the easy parts first.

2. Low parts first and then tall parts. If the tall components are dense and numerous, soldering the tall components first may hinder the soldering of other components.

3. SMD parts first and then DIP parts. If the DIP components are soldered first, the circuit board will be uneven on the solder circuit boards table, resulting in subsequent soldering difficulties.

Then, the method of manual soldering

When solder circuit boards, the temperature of the electric iron should be moderate, generally about 400 degrees. First on the clean solder coated with the flux, again with a clean constant temperature solder circuit boards iron to solder on a thin layer of solder (generally have tin-plated already when circuit board production, but sometimes the manual on the solder is very necessary), place your components to the circuit board and alignment, fixed them after applying solder, then pick one side with iron vertical direction is relatively slow slip pin, At the same time, press the side of the component slightly, and then solder the opposite side in the same way. After finishing the soldering, make a final check and repair the bad parts.

Inspection method: first visual inspection, and then use a sharp thing to check whether each pin loses, and finally can be measured with a multimeter. If the short circuit between the two pins, then can be coated with some flux, while the alcohol is not volatile with a solder circuit boards iron once again to fix.

What are the different solder circuit boards techniques?

There are various methods of soldering circuit boards. They are mainly divided into two different techniques: hard soldering and soft soldering.

1. soldering pcb board- Soft soldering

Soft soldering is used to connect small components to a larger PCB. Of course, soldering pcb board is not simply melting the details but must use an additional step to connect the pieces to the board. In this case, this extra step is a filler metal, usually a tin-lead alloy.
The use of this alloy is critical in the soldering process because it acts as the glue between the component and the board, holding the two together firmly.

2. soldering pcb board – hard soldering

Hard soldering is a process that uses a solid solder to join two different metal components together. As a soldering pcb board process, hard soldering consists of two smaller sub-processes called silver soldering and brazing.

How to Desoldering

The solder used can be easily removed by desoldering techniques. This can come in handy if you need to remove components or make corrections to electronic circuits.

To desolder a solder joint, you need a solder core, also known as a desoldering braid.

Step 1 – Place a piece of desoldering braid on top of the solder you want to remove.

Step 2 – Heat the soldering iron to touch the top of the braid and heat it for a period of time. You can remove the braid to see that the solder has been extracted and removed. Be careful touching the braid as it heats up as it will get hot.

How to a lot of desolder

If you have a lot of solder that you want to remove, you may need to use a device called a solder sucker. This is a handheld mechanical vacuum that can suck out hot solder with the push of a button.

To use it, press the plunger down on the end of the solder suction cup. Heat the joint with a soldering iron and then place the tip of the sucker on the hot solder. Press the release button to suck out the liquid solder. To empty the solder sucker, press the plunger.

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How to Solder Circuit Boards Yourself