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What Is Automatic Optical Inspection?

The demand for PCBs is growing at a rapid pace in different domains. Over the years, consumers have been more inclined towards PCB-integrated smart devices and electronics. 

It means that PCBs are the fundamental blocks of electronics and devices. There should be no error in the configuration of PCBs at all. It is because if a PCB is not performing properly, it will hamper the device’s performance as well. 

Therefore, it is important that manufacturers pass their PCBs through extreme quality check methods. It will rule out errors and defects in these PCBs to ensure fine performance. 

The complex nature of PCBs is inevitable for futuristic devices, but it increases risks as well. Today, PCBs are at their finest, and the quality control methods for them need to be accurate at the same time. 

Speaking of which, there is not just one PCB inspection method. You can select from multiple techniques as per your requirements and PCB variant. 

Now, we are going to take an insightful look at the importance of PCB inspection and quality control. 

Why Do PCBs Need Automatic optical inspection?

RayMing AOI
RayMing AOI

When you design PCBs, it is important to check the final product. It makes sure that everything is in place. Defective PCBs can lead to irreversible damage to the devices in the future. 

The PCB inspection methods detect the problems so that you can fix them in time. Sometimes issues with PCBs are not visible, and you might overlook them. Now if these issues show up in the future, it will complicate the PCB’s performance. 

When you pass your PCBs through strict quality control methods, you can point out hidden and unseen defects easily. Faulty PCBs are a big threat to the manufacturer’s reputation, and this is how. 

If a manufacturer does not make sure that its PCBs are ready for use, it can disappoint its clients. If you need to make your customers happy with your PCBs, never compromise on their quality. 

Defective PCBs can cause electrical glitches and current leaks and can also leave bare wires that can give shocks to the users. A faulty PCB integrated into an electronic device can even lead to fatal consequences for the users. 

Now, you know why inspecting PCBs before handing them over to your customers is significant to ensure consumer security and longevity of electronics. 

Inspection Methods for Printed Circuit Boards

You can define PCB inspection as a method to detect possible faults in PCBs, re-check the positioning of PCB parts and verify the quality of individual components after the production process.

There are different ways of inspecting PCBs. Some manufacturers use high-end quality control equipment and inspection machinery for this purpose. At the same time, others use automated testing methods for completely inspecting PCBs for defects. 

However, for small and less complex PCBs, there is no need for such measures. Workers can easily manually inspect them for faults. 

It’s time to consider manual inspection and its importance for different PCB producers in the next section!

Manual Visual Inspection

Manual visual inspection of PCBs is a basic and simplest checking method. Workers mostly visualize PCBs themselves or might use a magnifying glass or a microscope for this purpose. 

It mostly comes in handy when PCBs are small and not too complex. The technicians will double-check the details of the design of PCBs for the final product so that they can verify whether the final product matches these details or not. 

The workers can manually inspect PCBs whenever they feel to. There is no thumb rule for this type of inspection at all. However, it is better to know what factors you should inspect while performing MVI. These factors would be:

  • The width of the PCBs should be accurate. The texture of their surface needs to be appropriate as well. 
  • The sizes of the PCB components should be suitable, and the electrical connectors also need to be of appropriate sizes to not make the area congested.
  • The conductive components of PCBs should be standard. Make sure the solder is in suitable amounts. There should be no gaps left on PCBs in terms of soldering at all.
  • The surface of PCBs should be free of holes, impressions, and ridges.
  • Make sure the wiring is in place and they are in optimum condition.
  • The pad plating should also be working at its finest, and to make sure of this, there should be no extra roughness and rigidness.
  • The quality of the coating should be flawless, and for this, you need to verify its amount of flux and placement.

· Now, let’s have a look at some benefits of using MVI for PCB manufacturers:

  • It is not a complex method, and workers can perform it easily
  • It is affordable and does not disturb a manufacturer’s budget at all
  • MVI does not work with complex futuristic quality control tools 
  • The technicians can perform MVI at different intervals of the production process 


The only thing that you should keep in mind for executing MVI is the eligible workers. Skillful technicians that know how to get along with MVI come in handy. They will help in precisely detecting the problems with PCBs without using any tools and equipment.


  • It does not detect hidden defects of PCBs
  • It is not viable to use for complex PCBs
  • There are more chances of overlooking possible defects of PCBs due to MVI

Automated Optical Inspection


MVI is a simple inspection method, but it does not guarantee positive results. There is still a margin left for human error. However, one remarkable inspecting technique called automated optical inspection of PCBs can save you from errors. 

The process involves a video camera and lights to ensure 100% quality of PCBs. The purpose of the lights is to emphasize PCBs to easily detect their faults. Light from all directions helps in identifying the flaws in them.

After this, the cameras will film the PCBs and take images as well. In this way, the technicians will match this final product with the design requirements in the end. The process uses high-end equipment that includes 3d and 2d cameras. 

You can even use colored lights from different directions for this purpose. AOI is the latest technique that can prove to be a great alternative to MVI in the near future.

Automatic Laser Test Measurement

In case the former methods were not of use to you, try Automatic later test inspection of PCBs.

The purpose of ALT is to verify the sizes of solder joints of PCBs and their parts. The process involves different industrial-grade lasers that help to detect the assembly of PCB parts. 

The worker will reflect the light on the components to check their positioning and detect any faults in them. The process is useful and works on different calculations to see if the PCB is of quality or not. You can ALT, especially when there is a need to apply solder paste on the PCB parts every time. 

Not only this, there are other benefits of using ALT. Have a look at them below:

  • Helps with the PCB parts assembly
  • Detects the viscosity
  • Identifies the component cleanliness
  • It also assists with the printing of solder paste when needed
  • It is an insightful method and gives output data in the form of analysis and stats


  • The final data given by ALT is always correct; however, factors like interference and shielding can change the values if not controlled before or during the process.

What Is Via Filling?

No PCB design can work in an optimal environment without its vias. These are an integral part of PCBs that give them different features to perform naturally. The role of PCB vias is to transfer signals within all the layers of PCBs precisely.

 Vias in the PBs are to make sure that each layer is sending and receiving signals without any disturbance. These vias are just small holes packed with copper. These vias also join the layers with each other. 

The copper in the vias should leave no space in order to achieve positive results. However, the filling of copper should be controlled since overfilling can make the PCB layers hefty. An extra copper filling will also overweight the PCBs. 

Today, small and portable PCBs are common, and the vias for these are also small. Sometimes regulating everything in a small area becomes troublesome; however, a seasoned PCB manufacturer will perform this challenging task efficiently.

Advantages of a Via Fill PCB

flex pcb manufacturing process aoi

The PCBs with via fillings are more promising than those without vias. These PCBs collectively benefit your electronics in many ways. We are going to see why via-fill PCBs are crucial.

  • The components of such PCBs offer great surface mounting when needed.
  • The via-fill PCBs never stop liquids and air from escaping from the system, which makes them more reliable than other forms of PCBs
  • The PCB assembly will be free of defects making it dependable in the long run for the users. 

Copper-Filled and VS Copper-Plated Via

The two types of vias for PCB designs are either copper-filled or copper plated. Now, don’t get excited to know this because there are different applications of these types. We are going to discuss the benefits of copper-filled vias in detail for you. 

  • Such vias are important for boosting thermal conductivity due to the presence of copper.
  • Copper vias are also beneficial in enhancing the performance of PCBs when it comes to handling hot temperature conditions.
  • Copper can absorb large amounts of heat and leaves enough space for other components to stay cool in the case when the temperature exceeds
  • The heat can flow from one portion to the other, which reduces the chances of defects due to copper vias. 

Benefits of Copper over Gold for a Via Fill PCB

You might be wondering, at this point, why not use gold for via-fill PCBs? Well, it’s shocking to know that different PCB manufacturers will use epoxy resins and gold as fillings in place of copper for such PCBs. 

However, at the end of the day, you will get positive results from these fillings. For this purpose, copper gives the best output as compared to resins and gold. 

Below are some facts that will make you realize why using copper for via-fill PCBs is recommendable:

  • Gold has less potential for thermal conductivity and electrical transmission than copper
  • Copper enhances the longevity of PCBs for users
  • Copper is much more affordable than gold which makes it a reliable option to use via fill PCBs
  • Different analysis shows that copper via fill PCBs are more reliable 
  • High-powered electronics and smart gadgets can hugely benefit from copper vias instead of using gold and resins 


Humans always get confused when making their choice between two options. To save you from such frustration, we are giving you some factors that will help you weigh down via filling options easily.

  • Consider your application: Get to know about your purpose completely. The purpose you are going to use via filling entirely depends on the application.
  • Keep in mind the price: Some via fillings, like gold fillings, are too expensive to waste in errors, so make sure you are using an affordable via filling for your PCBs
  • Aim to make the design as straightforward as possible: Complicating your PCBs will not set you apart from other manufacturers; instead, always keep the designs basic which will help in ruling out errors in them as well. 

The End Note

Via Fill PCBs have a bright future because of their vast applications for users. In this post, you have learned about the role, significance, and benefits of using copper via fill PCBs for your future projects. 

However, in case you have any queries in mind, consult a seasoned PCB producer near you. They will clear your mind and also can assist you with cost-efficient via-fill options for your PCBs. 




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