As the source of the rapid development of the modern electronic information technology industry, the chip has widely penetrated and integrated into various fields of economic development. It is an important support for the digital economy, information consumption and even the long-term development of the country.
BGA is an essential part of electronic components. Sometimes, voids often appear in BGA packaging and welding. The main cause of voids is that the organic matter in the flux is cracked at high temperatures to generate bubbles, causing the gas to be surrounded in the alloy powder and forming voids. Soldering voids are likely to cause poor contact with electronic components during later use and affect the service life. In this article, we will share common methods for detecting BGA solder joint defects to help make better judgments.
What is BGA inspection?
BGA inspection, or Ball Grid Array inspection, is a process used in electronics manufacturing to ensure the quality and reliability of soldered connections on a printed circuit board (PCB) where the integrated circuit (IC) is attached using a grid of tiny solder balls. This inspection is crucial because BGAs, with their dense array of solder balls hidden underneath the component, can make it challenging to detect issues like soldering defects or misalignment once the component is in place. The inspection typically involves specialized equipment such as X-ray machines or automated optical inspection systems that can peer through or around the component to check for proper soldering, alignment, and other potential issues that could affect the performance of the electronic device. This ensures that the final product operates reliably and meets quality standards.
Why is BGA inspection so important?
BGA inspection is crucial because it ensures the reliability and performance of electronic devices by checking the hidden solder connections between the Ball Grid Array (BGA) component and the printed circuit board (PCB); since BGAs have their solder balls underneath, traditional visual inspections can’t detect problems like soldering defects, misalignment, or short circuits once the component is in place. This inspection uses advanced techniques like X-ray or automated optical systems to reveal issues that could lead to device failure or reduced functionality, thus preventing costly malfunctions and ensuring that the final product meets high-quality standards and operates as intended.
How to inspect BGA solder joints?
To inspect BGA solder joints, you typically use specialized techniques such as X-ray inspection to look beneath the component for issues like poor solder connections or hidden defects, since the solder balls are not visible once the BGA is mounted on the printed circuit board. Additionally, automated optical inspection systems can be employed to examine the board for alignment and soldering issues that might affect the component’s performance. These methods help identify problems that could otherwise lead to device malfunctions, ensuring the integrity and reliability of the final product.
Non-destructive detection method
Visual inspection
Visual inspection can be carried out during the entire production process of electronic products. Observe solder joints through a high-power magnifying glass, and initially detect whether there are obvious defects in solder joints from the appearance.
- Purpose:
To observe the solder joint simply, quickly and intuitively, and check whether there is continuous welding on the outside of the solder joint and the surrounding surface.
- Shortcoming
However, visual inspection has great limitations. It can only be used as a preliminary judgment when we do not have other testing equipment. It is impossible to judge whether there are other defects inside the solder joint or whether there are holes on the surface of the solder joint.
What is a BGA X-ray machine?
A BGA X-ray machine is a specialized tool used in electronics manufacturing to inspect the solder joints beneath Ball Grid Array (BGA) components on a printed circuit board (PCB), providing detailed internal images of these connections that are otherwise hidden from view. By using X-ray technology, this machine can detect issues such as soldering defects, misalignments, or short circuits that could affect the performance and reliability of the electronic device, ensuring that all solder joints are properly made and that the final product meets quality standards.
X-ray inspection
Radiographic inspection is a non-destructive physical perspective method, which uses X-ray perspective components to detect bubbles, cracks, and abnormal bonding lines in the internal packaging of components without destroying the chip.
(1) 2D X-ray
Records the light intensity changes after X-rays penetrate materials with different densities for the position of the sample that cannot be detected by the naked eye. Then it can form a contrasting image, showing the internal structure of the measured object. Problems can be observed without destroying the object.
- Purpose
To observe defects such as empty soldering, virtual soldering, internal displacement analysis, bridging, and short circuits of BGA soldering by X-ray scanning.
- Shortcoming
It only observes two-dimensional plane images. The principle is to display a three-dimensional sample on a two-dimensional display for imaging. For products with complex structures, the information in different depth directions overlaps, which is easy to confuse.
For example, when the components are on different surfaces at the same position, the shadows formed by the solder will overlap, which will affect the accuracy of the test results, so it is often used as a preliminary rapid determination of products with complex structures.
(2) 3D X-ray (CT scan)
3D X-ray better covers 2D X-ray limitations and presents three-dimensional images with high-density resolution and high spatial resolution. Besides, it can also realize simulated tomography images.
- Purpose
To clearly and accurately observe the soldering quality and structural defects of BGA solder joints. It enables to display of the shape, location and size of soldering internal defects.
- Shortcoming
Using the above non-destructive testing methods to detect solder joint defects, both visual inspection and 2D X-ray have limitations. 3D X-ray (CT scanning) is the most advanced non-destructive testing technology at present, which can solve the problem of solder joint defects well.
However, the detection cost is relatively expensive. If the product can be destroyed, the destructive detection method described below can be considered.
How does a BGA X-ray machine work?
A BGA X-ray machine works by passing X-rays through a printed circuit board with a Ball Grid Array (BGA) component, capturing detailed images of the hidden solder joints and internal structures on the other side. As the X-rays penetrate the board, they are absorbed at different rates by various materials, such as the solder and the PCB itself, creating contrast that the machine’s detectors use to generate clear, high-resolution images. These images allow technicians to inspect the quality of the solder joints and detect any potential issues, like poor connections or hidden defects, that could affect the performance and reliability of the electronic device.
Destructive detection method
Red ink test
The red ink test is suitable for verifying the solderability of BGA and IC on printed circuit boards. Soldering cracks can be judged by observing and analyzing the dyeing of solder joints of printed circuit boards and integrated circuit components.
The principle of the red ink test is to use the permeability of the liquid. Put the solder joints in the red dye, let the dye penetrate into the weld cracks, and the dry solder joints are forced to separate, and judge whether the solder joints are broken by observing the color state of the crack interface.
Simply, it is divided into five steps: cutting→infiltration→drying→separation→observation
- Purpose
In general, the red ink test can see the soldering phenomenon of all solder balls under the entire BGA. It is a common method to analyze the welding quality of electronic components. It can check whether there are defects such as virtual welding, false welding and cracks in the welding process of electronic components.
Slice analysis
Slice analysis technology is an important technology for PCB/PCBA failure analysis.
The steps of slice analysis technique are: Sampling→cleaning→vacuum mounting→grinding
→polishing→microetching (if necessary)→analysis.
The quality of slices will directly affect the accuracy of fault site confirmation, so the ability of inspectors is highly required.
- Purpose
It can be used to detect internal voids of PCBA solder joints, interface bonding status, wettability evaluation and circuit board quality.
SEM&EDS combination
On the basis of slice analysis technology, if you want to know the cause of solder joint defects, SEM&EDS can be also used to analyze the cause of failure.
Acceptance criteria for BGA solder joints
Acceptance criteria for BGA solder joints typically include ensuring that each solder joint is well-formed, with no visible defects like cracks, cold solder, or insufficient solder; joints should have a consistent, appropriate height and should form a good mechanical and electrical connection between the Ball Grid Array (BGA) and the printed circuit board (PCB). The joints must be free of bridging or shorts between adjacent solder balls, and X-ray inspection should reveal clear, uniform connections with no voids or irregularities. Meeting these criteria ensures the reliability and performance of the electronic device.
Common defects in BGA solder joints
Common defects in BGA solder joints include issues like solder bridges, where excess solder creates unintended connections between adjacent balls; cold solder joints, which are poorly made connections resulting from insufficient heating; and insufficient solder, where the amount of solder is inadequate to form a solid joint. Other defects can be solder voids, where air pockets or gaps are trapped within the solder, and misalignment, where the BGA component is not properly positioned over the PCB pads. These defects can cause electrical failures, reduce the reliability of the device, and impact overall performance.
Design considerations to avoid BGA defects
To avoid BGA defects, it’s essential to carefully design the printed circuit board with accurate pad sizes and spacing to ensure proper solder ball alignment and reduce the risk of solder bridges or shorts; also, choosing high-quality solder materials and ensuring precise reflow soldering processes can prevent issues like cold solder joints and insufficient solder. Incorporating thermal and mechanical design considerations, such as proper heat management and minimizing thermal stress, can also help maintain the integrity of the solder joints. Regular inspection and testing during and after assembly further help catch and address potential issues before they impact device performance.
Conclusion
Solder joint defect detection is necessary for BGA packaging. Mastering some common detection methods is beneficial for us to lower the loss as soon as possible and improve product quality. IBE is a professional and experienced EMS manufacturer. We provide one-stop turnkey solutions for various industries. Advanced equipment and technology are adopted to ensure product quality before delivery.
Founded in 2005, IBE Electronics is committed to providing high-quality EMS ODM/OEM services from home and abroad. Currently, we have 4 manufacturing bases located in China, USA and Vietnam with over 75,000 meters. Besides, we also provide customerized product services like automotive-used PCBA, and BMS PCBA, etc.. If you have any demands, please feel free to contact us.
The Ball Grid Array (BGA) packaging method replaces pins with a matrix of solder balls that sit at the base of the package.
- Visual inspection
- X-ray inspection
- Red ink test
- Slice analysis
The BGA package is a type of integrated circuit packaging that has an array of tiny solder balls on the bottom.
Last updated on September 2nd, 2024 at 08:11 am