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PCB X-ray Machine

X-ray is widely used to measure the quality of electronic components because it can penetrate and generate images of the inside of devices it passes through, thus, clearly detecting the internal state of electronic components. For Complex electronic components, we can adjust the x-ray tube’s angle, voltage, current, image contrast, and brightness to obtain effective image information.

 

For example, after BGA is welded, it is impossible to observe and check the welding quality of all soldered joints by traditional visual inspection method, especially under the belly of the welded joint, the AOI (automatic optical inspection) equipment can’t be used to evaluate the appearance of soldered joints. X-ray inspection equipment can only be used to inspect the physical structure of BGA soldered joints.

PCB (Printed Circuit Board) is the indispensable part used in the manufacturing of electronic products. Hence, you should rely on high-precision machinery and testing equipment to complete the excellent control of PCBA. For the accurate and high-performance testing, you need equipment such as AOI inspector, component cutting foot machine, wave soldering, X-ray machine, ICT test fixture, FCT test fixture, aging test stand, etc..    

 

So, let us discuss PCB X-ray inspection in detail.

 

X-ray test is used to detect the sample that cannot be detected by the appearance of the position. X-ray penetrates the material of different densities due to the change in its light intensity. The resulting contrast effect can form an image to show the internal structure of the object to be measured. Hence, this X-ray test can detect the problem areas within the object to be tested without destroying its properties. 

 

What does X-ray imaging detect?

1. Inspect the defects in the IC package, such as layer peel, bursts, voids, and integrity testing of wire.

2. Detect the defects in the PCB process, such as poor alignment or bridging, and open circuits.

3. Detection and measurement of voids in SMT solder joints.

4. Tests the possibility of open circuits, short circuits, defects, or improper connections in connection circuits of varied types.

5. Integrity testing of solder balls in solder array packages and cladding chip packages.

6. Detect cracks in higher density plastic material. 

7. Measures chip size, marking and wire arc, and tin component area ratio.            

 

Uni X-ray was established in 2002 and has become a national high-tech X-ray equipment supplier engaged in the research of precision X-ray technology as well as the development and manufacture of X-ray intelligent inspection equipment. Our technology and equipment are widely used in testing SMT, BGA, CSP, Flip-Chip, IC semiconductor components, connectors, wire, photovoltaic components, batteries, ceramic products, and other electronic products. Our manufactured equipment is ergonomic, easy to use, cost-effective, reliable, highly qualitative, long-lasting. Our equipment is used by many domestic and foreign companies, including PCB manufacturing companies for testing services.

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The Complete Guide Of PCB X-Ray Inspection

Table of Contents

 

PCB is a common term in the field of electronics and it stands for the Printed Circuit Board. These are non-conductive materials that have printed conductive lines embedded on their surface. Different electronic components are then etched on the surface of the board.

 

PCB is a common feature on most modern electronic appliances. It is attributed to the modern revolution in the field of electronics where we are seeing appliances becoming smaller and smaller over the years.

 

Also, PCB is preferred for its ability to accommodate many components. The printed circuit lines are accurately designed for their respective functionality. This explains why circuit boards are used even in the most sensitive applications. The process of manufacturing PCB entails X-ray inspection. They must be inspected for their accuracy and functionality.

 

What is X-ray Inspection?

X-ray inspection is a subset of digital X-ray image processing. This is a process in which a digital X-ray machine is used for detecting any traces of defects on a PCB weld.  One of such defects is the corrosion under insulation, an issue that is difficult to detect when using other imaging methods.

 

In the past, conducting such an inspection would be a hectic process as several sample areas would have to be identified before the inspection is carried out here. The whole process will take a significant amount of time and also had a low success rate.

 

X-ray inspection utilizes the principle of radiography to inspect the target area. This is mainly because both the X-rays and gamma rays are designed to penetrate through metal obstacles and be directed to a photosensitive material where they will generate a photographic film.

 

The inspection is based on the transmission of the electrons from the source to the receiver. The gamma rays and the X-rays travel from the source through a pipe and are directed to a detector where all the photons are received. The photons are also counted and the tally will be used for creating the film.

 

The pattern of the radiation that will be printed on the photographic film varies due to the defect on the weld or corrosion. This makes it easy to get an accurate image of the corrosion on the photographic film. The final position, size, and property of the film will be displayed in a non-destructive way.

 

The principle is also based on the fact that X-ray radiation has a short illumination time and is also super-fast. Also, the sensitivity of the display defect tends to be high when the thickness of the metal does not exceed 30mm.

 

Developments behind the PCB X-ray inspection

 

PCB X-ray 1  
Image of X-ray inspection

The PCB X-ray inspection technology has come a long way to reach its current position. In recent years, we have seen the applications of PCB in many different industries including telecommunication, aerospace, military automotive among others.

 

However, doing the PCM inspection using the traditional X-ray method is a herculean task. The process can be prone to errors and may not deliver the desired results. The use of surface mount technology (SMT) has resulted in smaller electronic packages rendering other inspection methods null.

 

Initially, manufacturers were using voiding as a method of inspecting defects on their electronics and semiconductors. However, this method became unreliable as it can lead to cracking of the joints. Voiding can also be the source of the thermal issue in an electronic.

 

Also, most PCBs tend to have high densities at their soldiered joints. Some of the joints are completely obscured making it almost impossible to inspect.

 

Such trends in the field of electronics and semi-conductor technology provide a fertile ground for advanced inspection systems.

 

X-ray proved to be a better alternative than most of the alternative inspection methods. That is why companies dedicated their resources to this imaging method.

 

The number of X-ray equipment manufacturers has also been growing at a steady rate. This has made it even easier and affordable for manufactures to use digital X-rays for PCB inspection.

 

The popularity of X-ray was further enhanced by its ability to be used on both thick and thin materials regardless of their complexities. It is also possible to generate different types of images from the X-ray inspections on PCB products.

 

How PCB  X-ray Inspection on Works

The working principle of X-ray inspection is based on the ability of the materials to absorb the X-ray radiation. The absorption of the rays varies from one material to another depending on the density, thickness, weight, and atomic numbers.

 

Usually, dense materials tend to absorb more X-rays than less dense materials.  This means that it is easy to generate images from dense materials. On the other hand, light or less dense materials tend to be more transparent to X-ray radiation.

 

The image below gives an accurate illustration of how the inspection works

 

pcb x-ray inspection

 

Image of X-ray inspection

 

From the image above, the dark sections represent the dense or heaviest parts of an object. Materials in this section are dense. The transparent sections represent the light sections of the object.

 

The beams from an X-ray machine penetrate through the object to give different output. The inspection will be able to uncover defects, holes, openings and sections that are not properly aligned with others.

 

These key components are heavily involved in the working of the X-ray inspection;

 

-The X-ray tube is used for generating the x-rays. These are the beams that will determine the output of the imaging process.

 

-Sample platform: The function of this platform is to allow the operator to view or inspect an object from different angles. The platform is designed to move along with the sample.

 

-Detector: The function of the detector is to catch or receive X-rays. It then converts the transmitted beams into a human-readable form.

 

The process of X-ray inspection starts with the generation of the X-rays from the tube. The rays will pass through the PCB which is under inspection.

 

The PCB is made of different materials and each has a unique absorption rate that is based on its atomic number. This difference results in different projections of the X-ray image. Some sections will have a dense projection while others will have a less dense projection.

 

The X-ray beams that pass through dots or holes are fully absorbed to form black images. This makes it easy to identify the defects on the board.

 

An image is generated from the procedure and it will provide the basis for analysis and inspection. The image should also be clear for easy understanding. The x-ray PCB inspection machine should provide adequate magnification that will eventually improve the quality of the image.

 

The machine should also allow the X-rays to radiate through the oblique angles when inspecting PCB boards. This way it is easier to obtain detailed and accurate output regardless of the thickness of the object.

 

You can improve the quality of the images by adjusting different settings on the X-ray machines. Also, changing the position and angle of alignment will give you different views of the PCB boards under inspection.

Since the image is in digital form, it can be printed for interpretation and analysis. It can also be sent to remote locations.

 

Steps of X-ray Inspection

Here are the procedures that are undertaken when inspecting PCB using X-ray inspection;

 

PCM void analysis

The purpose of the void analysis during the X-ray inspection is to determine the physical characteristics of the circuit board. This helps to improve the accuracy of the image that will be generated by the X-ray machine.

 

The analysis is achieved by exaggerating the contrast that exists between the voided area and the soldered section of the PCB. The difference should be significant enough for the detection of the voids.

 

Image optimization

Image optimization is done to improve the quality of the image generated during the inspection process. Image optimization can be achieved by changing different settings on the X-ray inspection system Computer software can also be used for the optimization.

 

X-ray power settings

This is the very first thing that you should do after starting a PCB X-ray inspection. The power is determined by the current and voltage settings. Select the right power settings based on the properties of the PCB that you are inspecting. While doing the settings, ensure that the machine does not operate at extreme levels. It should not be too or too low. It will be safer to keep it in the midrange.

 

Filtering

Filtering is necessary as it corrects the whiteout scenario due to the overexposure of the PCB to the X-rays. A physical filter can be used and it entails placing a copper filter over the source of the beams. The filter will control the amount of radiation that will be received by the target object.

 

Types of X-ray inspection systems for PCB

There are different ways of classifying PCB x-ray inspection devices. The first method is based on the mode of operations. Here we have offline X-ray inspection systems and online X-ray inspection systems.

 

One thing about offline X-ray devices is they can be used anywhere and can be integrated into any stage of production. They also allow for the inspection of the PCBs at any given time without dealing with too many constraints.

 

On the other hand, online X-ray inspection systems are more suitable for the mass inspection of the PCBs and when you intend to do few type changes on the board.

 

 The main issue with online x-ray inspection systems is they tend to slow down the assembly process. Also, they are not cost-effective as the offline X-ray systems. This explains why most PCB manufacturers still prefer offline X-ray systems.

 

Another method of classification is based on the output images. Here we have 2D X-ray machines and 3D X-ray machines. Even though both two systems are capable of inspection, there are some variations in their output.

 

As the name suggests, 2D X-ray inspection systems are capable of displaying 2D images of a PCB simultaneously. They display both sides of an object. On the other hand, 3D X-rays generate 3 –dimensions of an object. They do a cross-section image of a sample by rebuilding many 2D images.

 

Regardless of the type, the X-ray inspection system that you use, the whole process must be supervised. This is vital as it will help to cut down the cost of doing the PCB inspection.

 

Advantages of PCB X-ray inspection

The benefits of PCB x-ray inspection include

  • Does not require the removal of insulation
  • Minimum surface preparation on the material
  • Can work on both magnetic and non-magnetic materials
  • Does not require physical contact
  • Can inspect both the internal and external corrosion

 

PCB X-ray inspection

 

Sample of PCB X-ray inspection

 

Factors to consider when doing X-ray inspection

While you would like to get the full benefits of PCB x-ray inspection, this may not happen due to various factors.  Here are some of the key factors that you can use to increase the accuracy of your X-ray inspection process.

 

-Type of X-ray tube: There are different types of X-ray tubes that you can use for PCB X-ray inspection. Choosing the right tube will guarantee quality and precise images from the inspection. You can choose either an open tube or a closed tube. It is advisable to choose a high-resolution x-ray tube. You can be sure of getting quality and more accurate images from this type of tube.

 

Target type:  These are the materials that the x-rays are supposed to penetrate through. The materials are usually divided into two categories-penetrative and reflective target. The target type will play a role in determining the sample and the tube focus. This will eventually the magnification of the X-ray inspection system.

 

X-ray power and voltage:  The penetrating capacity of the x-rays is directly proportional to the power supplied. High voltage is used for inspecting large objects that have thick densities. You can use low voltage when inspecting thin and single-sided PCBs.

 

Conclusion

It is clear that the benefits of PCB x-ray inspection are immense. It is high time that you start using this inspection method for your PCB boards. Are you looking for the best PCB x-ray inspection systems? We have the right solutions.

At  Unixray, we design and sell reliable PCB X-ray inspection systems for various applications. Contact us and we will help you choose the right solution.

 

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