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What is a Solder Bridge | How to Avoid it in PCB Design

Introduction


One of the common issues found in electronic circuits and assemblies is solder bridging. It causes issues like electronic shorts, signal interference, poor circuit performance, component damage, etc. By understanding the factors that cause solder bridging and taking preventive measures, engineers can ensure the safety of electronic projects. 

It is seen that solder bridging affects the performance and functionality of electronic circuits. It is a prevalent issue that must be sorted out with preventive solutions. Mastering the techniques of fixing solder bridging can save the electronic circuits and assemblies. This article will comment on the concept of solder bridging and will highlight its causes, preventive ways, and solutions. 

What is a Solder Bridge?


A solder bridge is defined as an unintended connection present between two or more adjacent solder joints. The solder bridge is a connection of two or more pads by applying an excessive amount of solder. It creates a bridge between the pads. It is present on top of the PCB's solder mask. 

The solder bridge makes the pads thermally connected and inadvertently electrically. It is seen that the presence of an undetected solder bridging results in short-circuiting, malfunctioning, and burning of components, etc. Engineers, technicians, and electronic manufacturers need to understand the implications of solder bridging present in different electronic projects. 

What Causes a Solder Bridge?


Different factors aid in the formation of solder bridging in an electronic circuit. One of the primary causes of solder bridging is when an increased volume of solder is applied during the soldering process. The overflow of solder spreads across the adjacent joints and connects them unintentionally. It is seen that less spacing between the solder pads or components can also increase the chances of solder bridging. Improper soldering techniques used in an electronic circuit increase the probability of solder bridging. This problem can occur on machine-assembled PCBs even. Therefore, it is recommended that you conduct a thorough inspection of the PCB board before putting it into any live test.
 

How to Prevent Solder Bridging in the Circuit?


Various factors contribute to solder bridging during the process of soldering. It needs extra attention to save the electronic circuits and assemblies against poor functioning and component damage. Moreover, the presence of a solder bridge in a circuit can reduce the lifespan of components. Following are some of the techniques that can be used to prevent solder bridging:

Correct Application of Solder Paste


Solder bridging is one of the PCB defects commonly found in circuits. It happens when the solder gets to where it should not be. It can be prevented by minimizing the volume of solder paste. Stencil modification can help in the accurate application of solder paste, preventing the solder from bridging. 

Proper Application of Solder Mask


A solder mask is a coating that is applied on the surface where solder is not needed. There is no adherence of solder to the solder mask. It is critical to apply solder masks in important places of any circuit design, especially in between the pins of components. Failure to apply a solder mask at necessary places increases the risks of solder bridging. 

Placement of Fiducial Marks


Fiducials are placed on a circuit board by PCB manufacturers to place the parts on the PCB correctly. They help the circuit designers attach the components to the board efficiently. It is seen that improper placement of fiducial markers results in misplaced components on the board. This increases the risk of solder bridging. It is imperative to avoid poor fiducial marks. 

Stencil Thickness


A thick stencil can also cause solder bridging in any circuit. The volume of the solder paste present on the pad is affected by the thick stencil. Thick stencil leads to an overflow of solder paste from one pad to another and increases the risk of solder bridging in an electrical circuit or assembly.

Printing Process of Solder Paste


Any problem found in the printing process of solder paste can be one of the primary reasons for forming a solder bridge in the electrical circuit. For example, any grime or dust particles found at the bottom of the stencil will lead to a gap during printing. This will cause solder paste to be applied inaccurately. This can be one of the reasons for the presence of solder bridging in any circuit assembly or circuit design. 


Reduce Spacing Between the Solder Pads


Sufficient spacing between solder pads and the proper placement of components reduces the risk of solder bridging. It is disastrous to have soldered bridging on the PCB—solder bridging leads to serious operational issues and circuits malfunctioning.


Use of Surface Tension


The solder bridge can be detached using the surface tension of molten solder without the need for a wick. It is done using a soldering iron with a clear top. Ensure that there should not be overheating of pads or ICs. 


Temperature Monitoring


It is seen that the tip of the soldering iron must transfer the required amount of heat needed for the solder wick to melt and absorb the excessive solder. There is a need to monitor the temperature continuously. It should surpass the temperature to some degrees for soldering. For example, soldering at 250 degrees should increase to the temperature of 270 degrees. The increased temperature would cover the wick's heat absorption from the solder joint. 

Therefore, it is vital to take preventive measures to minimize the problem of solder bridging and its occurrence during PCB assembly and soldering process. Basic approaches such as solder mask application, component spacing, and working on pin configurations help minimize the risk of solder bridging in any electronic circuit. Flux-resistant materials and proper techniques used during the process of soldering ensure that there is no solder bridging. Follow the accurate approaches, identify the problem, and alter it before any damage occurs. 

How to Fix a Formed Solder Bridge?


Soldering bridges can be a big problem if formed in any electronic circuit or assembly. However, following the proper techniques can fix a formed solder bridge. Given below are some of the steps that can be followed to fix the problem of the solder bridge in a circuit:


● The right tools, like flux, pliers, solder wire soldering iron, etc, need to be used for fixing the formed solder bridge. 


● Safety precautions and safety measures are required to be followed for fixing the solder bridge. 


● Heat the solder joint where required and remove the excess solder. 


● Clean the area to avoid any malfunctioning of the circuit. 


● Apply flux to the surface. 


● Solder the joints and allow them some time to cool down. 


● Inspect the joints overall to analyze if everything is in order now. 


The solder bridge is removed using a soldering iron. The tip of the soldering iron is heated to remove the excess solder. The removal can be done using precision tools and tweezers. Another option to remove the formed solder bridge is by using the desoldering pump. It uses vacuum suction to remove the excess solder from pads and component pins. Flux can also be used to soften the stubborn solder-bridged connections found on the PCB. 
Precise and careful removal of solder plays a pivotal role in avoiding any damage caused to components and electrical assemblies. A thorough inspection needs to be done after the removal of the formed solder bridge to ensure proper functionality of the electronic circuit. 

Conclusion


Today, the electronic devices are smaller and more compact. Due to this reason, the soldering of components is becoming more complex. This complexity leads to different imperfections and issues in the assembled circuit board. Solder bridging is one of the typical issues found in the circuits, as discussed in this article. Solder bridging is produced when an excessive amount of solder flows over the undesired locations in an electrical circuit, so forming a bridge in a location where there should not be one. Solder bridging can create different problems in an electrical assembly, like damaged components, signal interference, poor circuit performance, electrical shorts, etc. 

Solder bridging harms the functioning and performance of an electrical circuit. Preventive measures can save the electrical assemblies and can improve performance. Electronic circuits and assemblies can be salvaged if the procedures for repairing solder bridging are mastered well. This article has discussed the concept of solder bridging and its implications in an electrical project. It has also discussed the causes of solder bridging and solutions to fix this problem. 


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