DFA is a procedure that consists of a total of three stages. In the first stage, the whole design of the circuit board is taken into deep consideration. In the middle of this stage, clearance is required among the components. That is often done where the soldering or the reduction of the cost occurs. 

While in the second stage different files are gone through to clear off the footprints and to know other cleaning procedures. Lastly, during the final stage other factors are identified like, wave soldering, reflowing soldering, manually done soldering and other things. 

By the end of this article, you will be able to know the importance and things you need to know about DFA in PCB design. 

What are the objectives of DFA?

Some of the objectives of DFA in PCB design are as follows.

Standardization 

Usually, every board of printed circuit board has a difficult time identifying the challenges. These challenges often tend to arise when you are proceeding with your work on a new printed circuit board. The main goal or objective of the standardization is to lower the levels of confusion. That is by putting the parts and other techniques into work. 

Some of the top ways which are used for ensuring the standardization to the maximum level are mentioned below.

• Try to understand where each component is coming from. This will help with getting firm on ensuring that the components that are being used are real. The unauthorized ways of components are a source of increasing delays, false information, and malfunctioning parts. 
• Another way is to reduce the total number of components that are labeled as unique. This can be a good way to reduce and ease up the overall design for the process of assembly. It can also enable you to make fewer mistakes and the chances of potential errors are also reduced. 

Validation of components

One of the other objectives that are determined to be primary is to demonstrate the components that are used in the board. Some of the guidelines of DFA in PCB design that can help the manufacturer to assemble the board efficiently are mentioned below.

• The components that are present within the BOM must be available and should not be dead. This is necessary to follow as it signifies the production or the delays shortly. 
• The MPN that stands for manufacturing part number should be identical to the one present on the PCB’s footprint. This helps in the removal of any mismatching.
• You should stick to the guidelines that are related to the spacing of components. This makes sure that the manufacturing of your printed circuit board is done properly. That is why DFA in PCB design is important.

Reduction of the errors during assembly

DFA in PCB design mainly focuses on the elimination of errors that might arise during the process of assembly. Other than the above-discussed points, other points that help manufacturers to invent PCB design are mentioned below.

• Sticking to the size, space, and limit for the holes that are drilled. This is important for the overall working of your printed circuit board. 
• You should thoroughly follow the limits that will prevent any problems with your PCB capacity.
• Make sure to follow the rules that are related to the clearance. 
• Ensuring the shape of the board enables penalization.
• Inputting of the thermal outputs wherever they are necessary. 

The standards of DFA

As we have mentioned earlier to know about the DFA in PCB design helps you to invent a board in a very efficient way. Not only effective but also in a way that is far more cost-friendly. 

Some of the most important DFA in PCB design rules and regulations are explained in detail below.

Orientation of the components

The component orientation is among the most necessary factor that has to be considered. This should be done during the stage before assembling. For an assembly that is free of problems, it is important to follow a clear and confined technique. 

Requirements for spacing 

The spacing that is present in between different components affects the requirements of the printed circuit board. Some of the ways that should be looked into to ensure top quality of the board are as follows.

• Part edge spacing 

The Part to edge spacing is the known distance from a certain component present on the board to its end. During this procedure, the components that are near the edge of the boat will be confined to much pressure. this might affect the joints that are soldering. Hence it is recommended to have at least 125 mil clearance presents between the edge of the board and the smd within the board circuit. 

• Part two hole spacing

This spacing should be taken into consideration for both components. This kind of spacing usually includes two main factors that should be met to get a good quality of assembly. The first is measured from the real whole edge to the edge of the pad.

Spacing that is required for the minimum extent is up to 8 mills. The second is known as the Part of the annular ring that is measured from the hole annular ring to the edge of the pad. The minimum required spacing must be around 7 mils.

Assembly standards of IPC

Few assembly standards for IPC will do good for your board assembly. 

Some of them are mentioned below. 

• IPC – A – 600 

This IPC is also known as IPC 600. It is used to specify the level of allowance criteria for every product. It is used for the definition of requirements of the board that includes desired product permission and constant factors. 

• IPC – A – 620C 

This IPC is used to describe the materials of a standard and to dictate a procedure or test for the acceptance criteria. That is further used for the harnessing of cable and other assemblies. 

• IPC – A – 630 

It is used the definition of the electronic standards and their enclosure. This kind of standard is usually employed when the CM is assembled and is used for the process of inspection. 

Common defects that occur in assembly 

Now we will be discussing those defects that often occur during the assembly. Along with that some of the ways to prevent such issues are also mentioned below. 

Tombstones

This is also known as the Manhattan effect. This refers to a certain scenario where a component is half or entirely removed from the landing pad. This one is common in the small passive of the SMD. This usually occurs due to the imbalance during the soldering. 

The ways by which you can prevent the Tombstones or Manhattan effect are as follows. 

• Ensuring a high level of component validity and a high temperature beforehand.
• avoiding exposure to extreme factors like temperatures and humidity.
• extending the zone of soaking to help balance the force of wetting on either side of the pads before it tends to reach the molten state. 

Bridging solder

This usually occurs when the soldier is present between the two types of conductors that should not be connected electrically. It can also cause short circuits. 

Ways that can prevent such cases are mentioned below.

• You should ensure that the content of metal that is present in the paste of solder must be up to 90 percent.
• The alignment of the stencil should be accurate and have a reduced size of 10 percent.
• The profile should be secured properly.

Solder balls 

The solder balls are quite common defects that often occur during the assembly of the surface. It is the basic way of developing a small spherical particle of the solder. This often causes issues related to the functioning of the printed circuit board.

Ways to prevent such cases are mentioned below.

• The size of the pad and the spaces should be according to the one in the datasheet.
• The printed circuit board should be baked before the solder paste. 
• You should ensure the overall thickness of the plating hole. It should be more than 25 micrometers which avoid the water trapping inside. 

Voids of solder 

The spaces that are empty or have holes in the joint of solder are called solder voids. It is caused when the amount of solder is not enough to carry on with a connection. It usually consists of air only. 

Ways that can avoid the void of the solder are mentioned below.

• Increasing the channel and giving access to escaping from the board.
• Try to opt for using a lead-free solder paste.

Once the printed circuit board design is completed, the manufacturers have to perform various inspections and procedures to ensure quality. 

Conclusion

The whole process of certain steps that mainly target the process of assembly is DFA. The DFA in PCB design ensures the proper working of the printed circuit board. That makes it easier for the manufacturers and users to ease up with the product. Therefore, it is recommended to work accordingly to the DFA in PCB design.