Solder joint inspection is a process of visual and x ray examination of a solder joint. It is an important quality control method used to ensure the quality of the solder joints. It can be used to detect several defects such as cold solder joint, bridging defect, voiding defect, and solder balling defect.
However, due to the complexity of a solder joint and its irregular shape, it is difficult to inspect a solder joint by a visual inspection method.
Before we understand why x ray imaging is perhaps the most effective method for BGA inspection, let’s take a look at the common methods of BGA inspection.
When inspecting a solder joint, the most common methods are:
1. Visual BGA inspection:
Visual BGA inspection is a good method for the detection of defects such as lack of solder in the joint area, closed circuit, etc. With visual inspection one can detect most defects on pads and leads.
This is a simple method, which is carried out with the naked eye. One sees the solder joint to check for any defects. The following are the main defects that can be detected during a visual inspection:
The advantage of visual inspection is that it is very easy to carry out, does not require any expensive equipment, and can be carried out in a short period of time.
However, the main disadvantage of visual inspection is that it is subjective, and one inspector may see a defect while the other does not. It is also possible that an inspector may miss a defect.
2. X ray BGA inspection:
X ray BGA inspection is a good method for the detection of defects such as incomplete wetting, bridging defects, voiding, etc. With X ray inspection one can detect most defects on pads and leads.
One uses an x ray device to inspect the solder joints. An x ray machine consists of an x ray source and a detector. These are connected to a system that is used to transfer the image onto a screen. The advantages of x ray inspection are that it can detect a wide range of defects, it is fast, and can be automated, thus saving time.
However, there are several disadvantages of x ray inspection. It is expensive, and can take a long time to carry out. It is also very difficult to get a clear image due to bright spots, shadows, etc.
Which is the best method for the inspection of a solder joint?
There is no best method for BGA inspection. Each method has its own advantages and disadvantages. It depends on the type of defects you want to detect, and the type of solder joints you want to inspect.
For example, if you only want to detect defects such as lack of solder, closed circuit, etc., then visual inspection is the best method for you.
The best ways to determine when to use x ray to inspect a solder joint BGA
Before you can determine when to use an x ray machine to inspect a solder joint BGA, you have to know the different types of defects that can be detected using an x ray machine.
X ray machines are used mainly to detect voiding defects. It can also be used to detect other defects such as cold solder joints and bridging defects.
Voiding defect is a type of solder joint defect that occurs when excess solder is not deposited on the substrate. This type of defect can only be detected by using an x ray machine.
Cold solder joint is a type of defect that occurs when the solder paste has insufficient heat and/or pressure applied to it. This can also be detected by using an infrared camera, but a BGA x ray machine can also be used to detect this defect.
Bridging defect is a type of defect that occurs when the solder paste is applied to the dual-side copper or when the paste bridges between the package and board. This type of defect can also be detected by using an infrared camera, but an x ray machine can also be used to detect this defect.
The best way to determine when to use an x ray machine is to know how it works. This will help you determine when it is the best time to use it for your solder joints BGA. You will be able to maximize the use of your device, and this will help you avoid incurring unnecessary expenses in terms of time and money.
What is a BGA X ray machine?
An X ray machine is an electronic device used to take the x rays of a solder joint. It is also called an X ray scanner, and it is used in the BGA x ray inspection of solder joints. It is used mainly to detect voiding defects. But it can also be used to detect other defects such as cold solder joints and bridging defects.
The x ray machine consists of an x ray source and a detector. These are connected to a system that is used to transfer the image onto a screen.
The x ray source can be either a rotating anode or a rotating target x ray tube. It is used to generate x rays. The detector is used to collect the x rays that have passed through the product. The system is composed of a camera and computer monitor, which are used to display the image on the screen.
How does a BGA X ray machine work?
X ray machine operates by emitting a beam of X rays at the sample being inspected. The beam passes through the sample and strikes the detector. The detector is used to collect x rays that pass through the sample and to convert them into an electrical signal.
The electrical signal is then converted into a digital image by the computer, which is then displayed on the computer monitor. This digital image can be saved in a file for future reference.
BGA X ray machine is used for inspecting solder joints of BGA (ball grid array). It can also be used to detect voiding defects of other types of solder joints.
X ray machines can be used for other purposes such as detecting cracks and voids in ceramic products such as board, disc brake drum, etc.
How do you inspect a ball-grid-array (BGA) solder joint?
The first step is to choose an appropriate x ray equipment and to place the device on the worktable. A BGA board is placed on the x ray table and fixed with a blanket. Then the X ray machine will be switched on. The object should be positioned so that it is perpendicular to the x ray source. The next step is to press the “take picture” button to obtain an image. The most important thing is that you should check if there is a solder ball missing or whether there is any solder bridging defect. If there is any missing, a new BGA chip must be soldered before the BGA x ray inspection.
The BGA X-Ray Image Analysis Method
The x ray image analysis method of a BGA solder joint is as follows:
1) Quantitative Analysis of Solder Joints: The number of solder balls and spacing are counted by the image processing software and then calculated to get the percentage of missing balls, spacing, and spacing difference.
2) Detection of Missing Balls: By analyzing the solder joint images, we can see whether any solder balls are missing or not. The missing ball will appear as a gap in the solder joint image. The radiolucent material is air in the void space. If there are several gaps, then it indicates that there are multiple missing solder balls. We can count the number of gaps in a solder joint to identify the number of missing balls. For example, if there are three gaps in a solder joint, then it indicates that there are three missing solder balls.
3) Detection of Bridging Defect: By analyzing the solder joint images, we can see whether there are any bridging defects or not. The bridging defect is a gap between solder balls and its location is above the surface of the substrate. The radiolucent material is air in the void space. It appears as an abnormally bright spot on the image. When you observe a solder joint with a microscope, you can see that the top of the solder ball forms a dome shape. If there is a bridging defect, then this dome shape will be broken. This is why the bridging defect appears as a gap above the surface of the substrate.
4) Detection of Voiding Defect: The voiding defect is another type of solder joint defect. It appears as an abnormally bright spot on the image. The radiolucent material may be air in the void space or some solder paste. If the radiolucent material is air, then this indicates that there is a voiding defect.