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A detailed guide to PCB soldering process-types, defects and solution

 

The process of PCB soldering is for joining metallic and electronic components together on the surface of PCB with the help of soldering wire which is a metal. The soldering wire has a lower melting point compared to other metals on the PCB surface. PCB soldering is a critical process in the electronic industry and has the primary function of joining the electronic components together to acquire a combined function.

Furthermore, PCB soldering or just soldering is also utilized for different purposes such as plumbing, joining pipes, making jewelry, roofing, etc. This article deals with detailed information about PCB soldering, its types, defects, and avoiding the defects.

What does PCB soldering mean?

PCB soldering is also known as the procedure for soldering the electrical and electronic components onto the circuit boards. Such soldering is among the basic techniques that anyone can follow for making printed circuit boards. There are numerous ways through which the soldering process can be completed but the easy way is joining small parts together onto the surface of the PCB. PCB soldering can be considered as the way for connecting different electrical components to achieve a single goal.

What are the 3 types of soldering?

There are three types of PCB soldering explained below in detail.

Fusion soldering

Fusion soldering is a very common soldering method,in the soldering process, the joint of the weldment is heated to the melting state, and the soldering can be completed without pressure. Such as arc soldering, gas soldering and plasma soldering.

fusion soldering

Pressure soldering

Contrary to fusion soldering,pressure soldering in the pressure soldering process, pressure must be applied to the soldering parts to complete the soldering method. Pressure soldering may be done with or without heat. Such as ultrasonic soldering, pulse soldering and forging soldering.

Brazing

Brazing soldering is involving higher temperatures for melting the material to be soldered. It is like hard soldering because the pieces of metal to be joint must be heated. The heat is being applied for a specified amount of time but the metals are not supposed to be melted.

Brazing is to be placed over the surfaces to be heated and it melts instantly and a bond is created. This procedure is also known as capillary action.According to the melting point of the solder, it is also divided into soft brazing (melting point below 450℃) and hard brazing (melting point above 450℃).

brazing

Which solder is best for PCB?

For PCB soldering numerous solder types are utilized.

Types of Flux Core

Acid and Rosin are two basic types of cores. The acid core is mostly utilized for soldering in applications such as plumbing and rosin is utilized for electronics.

Diameter

Diameter is referring to the thickness of soldering wire. Thinner the diameter will result in better results. However, thicker diameters are preferred where larger PCBs and multi-strand wires are to be used.

Length of Spool

Solders are coming in spools, and there is no specified metric for its measurement. The larger spools might be a little expensive but are highly recommended as these bear the best results.

Materials and equipment needed for soldering a PCB

The following is the list of materials and equipment required for the soldering of a PCB.

  • Soldering station
  • Soldering iron
  • Soldering gun
  • De-soldering station
  • Soldering pencil
  • Butane soldering iron
  • Soldering wire
  • Soldering flux
  • Soldering flux pen
  • Soldering seal wire connectors
  • Solder tips
  • Soldering wicks
  • Soldering paste
  • Soldering sucker
  • Electrical socket to put a plug of soldering iron

What are the 3 steps to proper PCB soldering?

The following are the main steps for proceeding with proper PCB soldering.

  • Preparing the iron and surface on which soldering is to be performed.
  • Placing the components onto PCB and applying to heat.
  • Add solder to the joints and apply soldering iron.

PCB soldering

What are the 4 steps in PCB soldering first aid?

Soldering is not considered a hazardous activity in general but a few points must be kept in mind while proceeding with soldering.

  • High temperatures are involved. It means that the temperature remains at 350oF and may cause burns, so it must be handled with care.
  • The stand must be used while handling soldering iron for keeping its users safe.
  • The solder can drip itself, so while soldering components onto PCB, it must be handled with care to avoid contact with the human body.
  • Soldering must be avoided with direction to face because fumes from coatings and flux may irritate resulting in eyes and respiratory harm.
  • While handling soldering onto PCB, the face must not be touched directly with hands as it has Lead which may cause skin harm.

Key factors in the perfect PCB soldering process

The following factors must be taken into consideration to achieve perfect PCB soldering.
Use the fluxes.

  • The reflow must be simple.
  • Using liquid flux where needed.
  • Controlling the heat with the use of heat sinks.
  • Small-sized components should be preferred.

What temperature should I solder PCB?

The temperatures are usually high when PCB soldering is considered. The temperature may vary between 600oF to 750oF. However, excessive heat of the soldering iron may cause damage to the components reducing its efficiency of working.

PCB manual soldering

What are the main PCB soldering defects? How should the manufacturers avoid these defects?

Numerous soldering defects arise because of different reasons that range from pollutants to operator errors. Following are the most common defects.

  • Tombstoning
  • Solder bridges
  • Position shifts
  • Webbing
  • Holes
  • Skips
  • De-wetting and non-wetting

The following measures must be taken to avoid the defects that incur during the process of soldering. for example, there must be a balance among the weight of components throughout the board when solder bridging is to be avoided. For getting rid of pinholes and blowholes, the orientation of the components must be in the same direction. For avoiding soldering bridging, there must be a sufficient gap between the solder mask and pads.

For avoiding tombstoning, components having similar solder thermal profiles should be utilized. For ensuring there is no non-wetting and de-wetting, all components must be within solderable shelf life. For avoiding skips, the pad sizes must be according to the specific SMD.Professional PCBA companies has a complete inspection process and high quality production equipment, so there are fewer defects.

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