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PCBX: Master the art of PCB assembly. Delve into expert guides on PCB assembly processes, techniques, and quality control procedures. Elevate your PCB assembly skills now! 

PCBA Resources - PCB Expert Manufacturing - PCBX

Through-hole assembly has been one of the foundational elements in electronics manufacturing since the birth of printed circuit boards over 60 years ago. While surface mount technology is rapidly gaining traction in recent decades, through-hole technology remains very relevant in many critical applications where strength, reliability, and high power are not compromised. At PCBX, we are fully aware of the relevance that through-hole assembly still has and the vital role it plays in many applications where robustness and cost-effectiveness are called for.Through-hole technology includes passing the leads of electronic components through pre-drilled holes on a PCB and soldering them for stable electrical connections. Despite the fact that SMT has dominated most compact, high-density applications, through-hole assembly has remained imperative, especially in industries of aerospace, automotive, and industrial equipment, where boards face mechanical stress and harsh conditions.<img src="https://img.pcbx.com/dev/file/image/article/20241205/079a74c9cabe40bb83f1d5e6513ef36b.jpg" alt="Through-Hole Assembly Process-PCBX" data-href="" style="width: 100%;"/><h3>Key Steps in Through-Hole Assembly Process</h3>In most instances, there are several key stages involved in through-hole assembly. In addition, they require a degree of accuracy and professionalism, especially when high-quality results are desired with assurance. We will now discuss the primary stages: <h4>Component Insertion</h4>Manual Insertion: Conventionally, components are placed manually by hand using tools. Labor-intensive and slower, it is still applicable for prototyping or low-volume orders where setup flexibility and ease of inspection are valued.Mechanical/Pneumatic Insertion: Automated insertion machines, with vibratory bowls or complex mechanisms, can insert components with speed and consistency over larger runs of production while minimizing manual handling errors. Odd Form Insertion: Equipment for atypical components includes those needing lead forming or custom tooling, therefore extending the type of parts that can be used from the norm. <h4>Soldering Techniques</h4>Wave Soldering: Dominant in high-volume production, wave soldering involves passing the entire PCB over a wave of molten solder. This method efficiently solders all joints simultaneously, ensuring repeatability and high throughput.Selective Soldering: Employed when a board combines through-hole with sensitive SMT components, selective soldering lays molten solder only where required, thereby precluding any damage from a wave process.Hand Soldering: It is still applicable today for prototypes, repairs, and small batches. Hand soldering is dependent on operator skills but allows more control over each joint, thus is quite suitable for work that requires a lot of precision.<h4>Cleaning and Finishing Steps</h4>After soldering, there may be a cleaning stage following soldering to remove flux residues, which will help the board last longer. The process also includes adhesive curing, conformal coating, and stringent testing, among others, in completing the assembly.&lt;button class="center btn-lg" data-href="/order/manufacturing/pcb"&gt;Get an Instant Quote for PCB Manufacturing & PCB Assembly&lt;/button&gt;<h3>Design Considerations for Optimal Through-Hole Assembly</h3>Effectively designing PCBs for through-hole assembly involves a specific set of considerations to facilitate manufacturability and durability. Component and Lead Spacing: The spacing should be enough to avoid any probable defects such as tombstoning or solder bridges. The design should take into consideration the physical footprint and orientation needed for reliable insertion and soldering. Thermal Relief Pads: These should be employed around heat-sensitive components to control heat transmission, reducing the risk of thermal damage during soldering.Solderable Surfaces: The engineers should ensure that pads are accessible for full solder coverage, and no obstruction may obstruct the process.Mixed Technology Strategies: Positioning should be done in such a way that when SMT is integrated, the risk of damage during reflow is minimal. Through-hole components shall be used where strong connection and high mechanical stability are required.<h3>Common Defects in the Through-Hole Assembly</h3>Despite maturity, through-hole assembly can still have defects regarding soldering and component placement. Identification and prevention of these are essential: Tombstoning: This defect is related to the lifting and standing of the components vertically while soldering. It can be minimized by proper lead spacing and enough clinching after insertion. Solder Skipping: Missing solder fillets are usually due to insufficient heat or contaminated surface conditions. Regulated thermal profiles with clean contacts will help address this issue.Solder Bridging: This can be avoided by keeping enough spacing between pads and using solder masks to avoid the accidental connection of adjacent leads.Cold Solder Joints: Insufficient heat or oxidation of surfaces causes dull, weak joints. The solution is in temperature adjustments and verification of the accuracy of the process.<h3>Rework and Repair Strategies</h3>In case defects are present, through-hole assemblies have accommodating repair options:Manual Soldering: This allows for precise heating to remove and replace faulty components.Desoldering Tools: Employ vacuum or thermal technology to remove faulty components with minimum damage.Reclip and Bypass: In cases of more serious faults, component leads can be clipped and bypassed with jumper wires.<h3>Process Control Implementation</h3>Good quality through-hole assembly requires rigorous process control in many aspects:Solderability Testing: Proper hole wall wetting indicates good soldering and advises process adjustments.Lead Testing: Clinch height and pull force testing prevents tombstoning.Thermal Profiling: Thermocouples facilitate monitoring heat distribution and time for soldering, reducing defects.Automated Optical Inspection (AOI): Provides oversight through verification of placement accuracy and formation of solder joints. It is done by using statistical process control to identify opportunities for continuous improvement.<h3>Mixed Technology Assembly</h3>For a large number of today's electronics, mixing through-hole and SMT components on the same board brings substantial benefits. This hybrid approach leverages the strengths of both technologies:THT: Better mechanical stability, especially power handling; easy to inspect or repair.SMT: Designs can be much compact and closely packed with lower assembly costs at quantity levels.Progressive introduction of SMT on a through-hole infrastructure takes care of technology evolution, avoiding unnecessary loss of capital and maximizing investments. Early implementation or use of SMT could be confined to drop-in replacements for standard Through-Hole components. As SMT capability improves, designs can migrate to higher-density solutions with few through-hole components. <img src="https://img.pcbx.com/dev/file/image/article/20241205/0c445031352a431ba37599c56628afee.jpg" alt="Through-Hole Assembly Process-PCBX" data-href="" style="width: 100%;"/>Despite the development of SMT, through-hole technology keeps its niche as a relevant technique in electronics manufacturing. We at PCBX preach its continued integration with SMT for a balanced synthesis of reliability, performance, and efficiency. Through-hole assembly, if executed with precision and backed by strong process controls, continues to provide unrivaled robustness and reliability in application and has become indispensable for modern and legacy electronic designs alike.

Through-hole assembly remains essential in electronics, offering strength and reliability, especially in critical applications, despite SMT's rise in compact designs.

Through-Hole Assembly Process

In the complex world of manufacturing for PCB assemblies, ensuring functionality and reliability are crucial success factors for electronic devices. In-Circuit Testing, a thorough testing methodology that verifies the integrity and functionality of individual components and their interconnections on a PCB, has a very important role in this process. The process of ICT testing not only reduces early defects in the production process but also maintains overall reliability and quality expected in finished electronic products.In-Circuit Testing is a very accurate test applied to check operation on PCBs with the help of special test equipment called ICT testers. These testers use a set of electrical probes to contact the PCB test points to measure parameters like resistance, capacitance, and signal integrity. The tight process makes sure that each component on the board operates within pre-set parameters, and hence defects such as short circuits, open circuits, wrong value components, or faulty solder joints are highlighted efficiently.<img src="https://img.pcbx.com/dev/file/image/article/20241107/52825a6872d2497fb417e71a2813d315.jpg" alt="In-Circuit Testing (ICT)-PCBX" data-href="" style="width: 100%;"/><h3>How Testing Works with ICT</h3>In achieving this, the process of ICT is based on a sequence of steps that have been cautiously laid down to ensure that every electronic component on each PCB will work without fault. Let me look at how ICT testing works:Test Fixture Setup: The PCB then goes into a custom test fixture which fixes the board in place and aligns it correctly with the probes used to test. This setup is highly critical; proper measurement depends on this, as well as consistency.Program Loading: A particular test program is loaded into the ICT system, which is generated to meet the particular design of each PCB and components making it up. It contains test sequences and parameters that are needed for complete scrutiny.Power Application: The application of power to the PCB for functionality would be in conditions that have been simulated similar to when it would actually be in use. This allows for effective functionality of the components to be evaluated in natural operating conditions.Electrical Connection Testing: The system will check the PCB's connectivity by contacting the test probe with various test points to make sure accurate signal paths are made and detects open circuits or broken connections.Component Verification: All components are tested individually with the purpose of checking if they fall within specified electrical parameters-resistance, capacitance, and inductance-that validate their integrity and performance.Functional Testing: This is the checking of operational performance by the PCB to see whether the output signals are correct and whether the circuits perform according to the designed specifications. This step further advances the work of the board in real time operation, confirming its overall performance.Data Collection and Analysis: ICT testing also covers data collection and analysis, which is done in much detail in real time. Advanced software tools conduct automated analysis and can pinpoint any discrepancies or faults immediately, thus providing feedback in no time.Fault Diagnosis and Reporting: Once a fault is detected, the ICT system produces comprehensive diagnostic reports showing location and nature. This information is invaluable in the identification of the problem and aids in speedy repairs.Re-testing After Repair and Final Quality Check: Once the faults identified have been corrected, the PCB is put once more to testing. Final quality checks entail confirmation that the PCB is to specification without defects and hence fit for distribution.&lt;button class="center btn-lg" data-href="/order/manufacturing/pcba"&gt;Get an Instant Quote for PCB Assembly Service&lt;/button&gt;<h3>Advantages of ICT</h3>ICT presents a host of advantages which make it indispensable in the field of electronic manufacture to wit:High Accuracy and Speed: Speed and accuracy with which the defects can be correctly detected make ICT indispensable when volume productions are concerned.Extensive Fault Coverage: There is great exposure in ICT to a wide number of defects that one could find on a board, thus allowing the manufacturer to deal with myriads of issues systematically.Easy Use: The simplicity of setup and operations of systems using ICT contributes to reduced user errors and improved reliability.Flexibility: ICT systems can easily accommodate most types of PCB design without any problem and are readily updated for more current testing techniques or methodologies as they emerge, so that even evolving technologies would keep them useful.<h3>Challenges and Limitations</h3>Despite its many strong points, ICT does face a number of challenges:High Fixture Costs: In-circuit test fixture generation is generally an investment; the initial costs are such that they often tend to be highly prohibitive for lower volumes of production.High-Density Component Testing: With ever-denser PCBs using ever-smaller surface-mounted components, good contact with tightly packed test points may problematize ICT in practice.Requiring Regular Maintenance: The systems need periodic cleaning and, above all, replacement of the test probes in order to deliver their results with full, true accuracy.<img src="https://img.pcbx.com/dev/file/image/article/20241107/f24672eb542849b880751338e1ce7788.jpg" alt="In-Circuit Testing (ICT)-PCBX" data-href="" style="width: 100%;"/>While most electronic products become increasingly sophisticated and compact, In-Circuit Testing remains a standard method of testing PCB boards. Helping to ensure each component and every connection on a board functions correctly, ICT enhances product reliability at final assembly and testing. We are committed to the application of state-of-the-art ICT systems at PCBX, ensuring our products meet the best-in-class performance and dependability standards-a commitment keeping pace with the latest developments in technology at PCB manufacturing.

In-Circuit Testing ensures PCB reliability by verifying component integrity and connections, with advantages in accuracy and coverage, but high setup costs.

In-Circuit Testing (ICT)

Inspections and Tests in the SMT Assembly Process

With SMT assembly being the primary technology in current electronics manufacturing, new materials, technologies, and equipment will be developed indefinitely. This is consistent with the ever-increasing assembly density, an increasing number of pins, and decreasing pitch diameters. Furthermore, more and more SMDs are packaged with visionless pins.These developments have raised scrutiny and test demands in the SMT assembly process. There is a growing need for careful development of inspection and test procedures coupled with the selection of suitable inspection technologies.<h2>SMT Inspection and Test Technology</h2>Among others, some of the usual techniques applied in inspecting and testing during the SMT assembly process are visual inspection, AOI, use of X-ray, and ICT.<h3>Visual Inspection</h3>The name implies that visual inspection involves staff inspecting product quality against manufacturing standards with their naked eyes. This method is widely used since it is simple to use and inexpensive, but its accuracy is strongly dependent on the staff's expertise and attitude. However, due to physical limitations, visual inspection is not able to inspect 0603 or 0402 packages and some fine-pitch components. Visual checks in the SMT manufacturing line normally occur after solder paste printing, before reflow soldering, and after reflow soldering. Of these, the one before reflow soldering is the most critical.<h3>AOI</h3>AOI normally makes its foray right after post-reflow visual inspections to identify the defects with the help of high-speed and high-accuracy Optical technology. The AOI machine captures images of the targets it inspects and does a comparison with predefined parameters stored in a database to mark PCB defects.Finally, AOIs include simple programming and operations. The approach, however, cannot be used to undertake structural inspections on components with visionless solder connections, such as Ball Grid Arrays. Furthermore, AOI cannot detect hidden problems like as component or PCB warpages.<img src="https://img.pcbx.com/dev/file/image/article/20240814/93b143dca2f34a2ab7f67ba727fa6987.jpg" alt="Automated Optical Inspection-PCBX" data-href="" style="width: 100%;"/><h3>ICT</h3>ICT normally utilizes flying probe testers and bed-of-nails testers to test modules right after SMT assembly. The electrical performance of the PCB's components can be tested, and ICT can discover improper circumstances such as missing, incorrect, or damaged components, shorts, opens, and assembly problems.<img src="https://img.pcbx.com/dev/file/image/article/20240814/42f4698607f041f4a6ecdcbd8749a3f3.jpg" alt="ICT-PCBX" data-href="" style="width: 100%;"/><h3>X-ray Inspection</h3>X-ray inspection checks the quality of the solder joints by scanning the PCB. Because of X-rays' penetrating capacity, the quality of soldering could be seen in great detail. Compared to AOI, the technique of the X-ray inspection could let out more dimensions of the solder joints; however, this is more expensive.<h2>SMT Inspection in Placement Settings</h2>Inspections happen at all levels while the sub-assembly process of the SMT progresses—from acceptance of the raw materials to completion of the same assembly.<h3>Pre-assembly Incoming Inspection</h3>The incoming inspection process mainly monitors the quality of all the materials used for SMT assembly, from PCB bare boards to stencils, components, and solder paste.<h3>Process Inspection during SMT Assembly</h3>Process inspection during SMT assembly tests the performance, and identifies, and addresses the defects emerging from the solder paste printing, chip mounting, and reflow soldering.<h3>Module Inspection and Rework after Reflow Soldering</h3>In the end, the quality of reflow soldering and the functionality of the assembled module are checked for defects, and rework measures are taken.<h2>Incoming Inspection</h2>The incoming inspection includes bare boards of PCBs, components, and solder paste.<h3>PCB Bare Board Inspection</h3>Size and Appearance: Size inspections include checks for aspect ratio, space, tolerance, and size related to the edge of the PCB. The appearance inspections are targeted inside/outside layers of multi-layer and single/double-sided PCBs. Such inspections look for open, short, scrape, line width, tracing, and other flaws.Warpage: Warpage is measured by pressing corners of the board to a surface and measuring the distance from the fourth corner to the surface.Solderability: Checks pads and electroplated through holes using edge dips, rotation dips, wave dips, and solder ball tests.Internal Defects: Techniques like microsectioning inspect internal defects such as the thickness of copper, conductive layers' alignment, and integrity of lamination.<img src="https://img.pcbx.com/dev/file/image/article/20240822/d664caea78de4c6ca51fc07536cc9933.jpg" alt="PCB Bare Board Inspection-PCBX" data-href="" style="width: 100%;"/><h3>Component Inspection</h3>This is an orbital inspection procedure in which elements are evaluated for performance, specifications, package, order requirements, product reliability, assembly technique, and storage. Lead coplanarity and layer thickness are also checked to assure technological compatibility and thermal endurance.<h3>Solder Paste Inspection</h3>Qualified solder paste should contain 85%-92% metal content, curing strength, and adhesion from 200 Pa·s to 800 Pa·s.<h2>In-Process Inspection</h2>The primary procedures involved in SMT assembly include solder paste printing, chip mounting, and reflow soldering. The entire process should be inspected to guarantee a high pass rate; quality checks need to be done immediately after every fundamental process to detect defects at an early stage. Some of the processes detailed above include:<h3>Solder Paste Printing Inspection</h3>The standards are:The solder paste is well distributedCorrect alignment with pads in size and shapeCorrect solder quantity and thicknessMolded solder paste with no collapse or cracksAdequate coverage area<h3>Chip Mounting Inspection</h3>Chip mounting defects include misplacement, missing parts, excessive glue, incorrect parts, wrong direction, floating, and rotation. With the occurrence of said defects, an immediate parameter adjustment is necessary.<h3>Reflow Soldering Inspection</h3>Common defects are tombstones, insufficient solder, oxidation, void soldering, solder balls, and cold soldering. Each of these qualities requires correct rectification to ensure appropriate soldering procedures do exist.<h2>Product Inspection and Rework</h2><h3>Product Inspection</h3>Following the SMT assembly process, items must undergo ICT and functional testing. The flying probe tester is one of the most often used pieces of ICT equipment today. This test equipment uses probes instead of a nail bed fixture and can record tests straight from CAD software. This improves flaw detection accuracy.Functional tests performed after ICT evaluate the system's adherence to design specifications. The system is powered by input signals, and the output signals produced are examined to ensure that they match the functional indices.<h3>Rework</h3>Modules that fail to qualify are subject to manual or station rework. In the case of manual work, sophisticated tools, and skillful people will be required. On the other hand, professional rework stations are required in the case of complex PCBs.Chip Component Rework: Correct tombstones, insufficient solder paste, shorts, misplacement, and cracks by providing accurate manual adjustments and refilling the solder paste.IC Component Rework: This includes bridging, inadequate tin, and displacement repairs; most of the time, the components must be removed and resoldering manually.Manufacturers can reduce rework occurrences and boost product pass rates by implementing rigorous inspection and rework processes.

With SMT assembly at the forefront of electronics manufacturing, advanced inspection technologies like visual, AOI, ICT, and X-ray are essential due to increasing component complexity. Inspections throughout all stages—incoming, process, and post-reflow—address defects, ensuring quality and reducing rework.

Inspections and Tests Applied in the SMT Assembly Process

The article provides a thorough introduction to the SMT (Surface Mount Technology) assembly process and elaborates on its future development trends.<h2>SMT Assembly Process</h2>The article provides a thorough introduction to the SMT (Surface Mount Technology) assembly process and elaborates on its future development trends.The process of SMT assembly consists of several complex steps, including solder paste printing, chip mounting, reflow soldering, cleaning, inspection, and rework. All these steps are equivalent in ensuring that the product performs well and is high quality.<h3>Solder Paste Printing</h3>Solder paste printing applies solder paste to PCB pads via stencil apertures. The solder paste printer will be the first piece of equipment added to the SMT assembly line to do this.<img src="https://img.pcbx.com/dev/file/image/article/20240821/ead027ed4d9949a6b19d51bf9f493f9e.png" alt="Solder Paste Printing-PCBX" data-href="" style="width: 100%;"/><h3>Chip Mounter</h3>Chip mounting—this is a process that places components onto the PCB according to the design specification. In other words, it is done by a chip mounter, the second machine in the line of SMT assembly after a solder paste printer.<h3>Reflow Soldering</h3>During reflow soldering, this solder paste would be melted to bind the SMC or SMD onto the PCB. Likewise, it takes place in the reflow soldering oven downstream of the chip mounter in the assembly line.<h3>Cleaning</h3>There are potentially hazardous residues in the area that need to be cleaned that were probably left behind after the cleaning procedure. A cleaning machine, which can be online or offline to the SMT manufacturing line, performs this procedure.<h3>Inspection</h3>Inspection confirms the quality of soldering and assembly according to the set standards. A lot of inspection equipment and tools are utilized, such as magnifying lenses, microscopes, In-Circuit Testers—ICT, flying probe tests, Automated Optical Inspection (AOI), X-ray inspection, and functional testers. All of these can be tactically positioned along the assembly line.<img src="https://img.pcbx.com/dev/file/image/article/20240814/cf041a45a54f4d94a10003d61a9a9f1c.jpg" alt="Automated Optical Inspection-PCBX" data-href="" style="width: 100%;"/><h3>Rework</h3>Rework addresses and rectifies the flaws found during the inspection process. This process uses equipment such as electric soldering irons and rework stations and can be placed anywhere in the line of SMT assembly where appropriate.<h2>Future Trends in SMT Development</h2><h3>Fast, Flexible, and Rapidly Responsive Systems</h3>Swift, adaptable, and agile technical systems will be more and more important to enterprises as they seek to maximize profitability and seize market opportunities in more competitive conditions. In this respect, SMT machinery will need to improve in areas like responsiveness, speed, and flexibility.Thus, SMT assembly lines evolved from a single to a multi-equipment setup to increase production volumes without necessarily losing the high-efficiency levels desired, which remains indicated by productivity and control efficiency. Modern SMT lines are taking the route of a double-line setup to improve production rates while reducing space occupied.<h3>Green and Environmentally Friendly Practices</h3>Environmental protection will become increasingly crucial in SMT assembly. Starting with the materials used, from the packaging, solder paste, adhesives, and flux to the way assemblies are made, there was always an environmental impact associated with SMT manufacturing. Improvements in the future deal with green manufacturing lines.Green manufacturing puts the requirement of meeting environmental standards from the start. For this purpose, every single phase of the assembly process will be critically thought out for its potential to produce pollution, which will define the choice of suitable SMT equipment and materials, test manufacturing regulations, and create environmentally friendly conditions. More eco-friendly awareness will play a vital role in directing SMT line design, equipment selection, and operation.<h3>High-Efficiency and Intelligent Systems</h3>SMT equipment has evolved with the progress of SMT assembly. The manufacturing efficiency of SMT will be the main criterion for performance evaluation of SMT equipment in the future, which requires structural adjustments and improvements in performance enhancement for the machinery of SMT.SMT equipment's versatility allows users to rewrite services to meet individual requirements. Modular designs can handle a wide range of tasks, allowing for diverse component mounting needs at varying levels of accuracy and speed to provide improved overall manufacturing efficiency.<h2>Conclusion</h2>Because of its inherent advantages and potential for widespread application to numerous industries, partially or replacing traditional assembly processes, it creates a tremendous revolution in electronics. To fully realize its potential in numerous industrial applications, the SMT assembly process and its development patterns must be understood.

The article introduces the SMT (Surface Mount Technology) assembly process and future trends. Key steps include solder paste printing, chip mounting, reflow soldering, cleaning, inspection, and rework. Future trends highlight fast, flexible systems, green practices, and high-efficiency, intelligent systems. SMT's potential revolutionizes electronics manufacturing with wide industrial applications.

SMT Assembly Procedure and Future Trends

As the lines on PCB (Printed Circuit Board) intended for SMT (Surface Mount Technology) assembly continue to shrink, along with components becoming miniaturized, and SMD (Surface Mount Device) more densely packed, the original visual inspection methods can not meet the quality demands. In turn, AOI (Automated Optical Inspection) has become a very important technology in SMT assembly for the inspection of solder joint performance. The increasingly applied and technologically developed AOI tends to intelligent inspection modes in SMT assembly.<h3>Working Principle of AOI Technology</h3>Despite the various forms that AOI can take in SMT assembly, generally, they share a common underlying technique, and that is the process of using optical techniques to capture images of the target to be inspected and analyzed, and judged based on some criteria. The commonly used methods in AOI systems are DRC (Design Rule Check), and CAD (Computer-Aided Design) data comparison.<h4>DRC</h4>The DRC method applies inspection to design patterns according to predetermined rules. For example, a PCB circuit pattern can be checked to ensure that all lines end at solder joints, have the same width, and that their positioning concerning each other lies within a distance. In this manner, the DRC method could achieve that the algorithmic validity of the pattern is secured and some benefits, including easy setup, high-speed performance, minimum program, and insignificant data storage. Thus, this method is extensively used in AOI systems.However, the DRC method's limitation lies in its ability to determine boundaries, thus requiring particular methods to establish boundary positions.<h4>CAD Data Comparison</h4>Compared digital image patterns stored in the AOI system to real captured images this method could develop the inspection results. The accuracy depends on inspection precision, definition, and all the steps involved in the inspection, which means the method is highly concerning accuracy but requires high data storage and real-time behandeln capabilities.Although both techniques have advantages, the CAD data comparison method is chosen more for its gains in a wide range.<h3>Inspection Functions of AOI Technology</h3><img src="https://img.pcbx.com/dev/file/image/article/20240814/cf041a45a54f4d94a10003d61a9a9f1c.jpg" alt="AOI Technology-PCBX" data-href="" style="width: 100%;"/>AOI is applied in inspecting bare PCBs, solder paste printing, components, and solder joints.In the production process, bare PCBs and solder joint inspections are usually done by separate AOI equipment, which inspects in a non-real-time manner.An AOI system often integrates solder paste and component inspection into one, including real-time inspection with solder paste printers and chip mounters. An example would be the advanced solder paste printer with two heads, capable of real-time inspection of the printing thickness and the edge collapse through AOI systems.Inspection Items:Disconnection, wire-tapping, scratches, pinholes, mass-area defects, line space, and trace, edge roughness, for bare PCBs.Lead formation and bending of solder joints, missing components, misplacement, orientation of components, solder joint quality, etc.If AOI system detected unqualified components, they would usually give reminders to operators for replacement, which could help to prevent big mistakes.<h3>Structure of Common AOI Systems</h3><h4>AOI System for Bare PCBs</h4><img src="https://img.pcbx.com/dev/file/image/article/20240808/e13e6382fabe4eeb9397e09ea3fbf2e2.PNG" alt="AOI System for Bare PCBs-PCBX" data-href="" style="width: 100%;"/>This system has a comparison function and two cameras. The 1D image sensor installed in the inspection subsystem photographs the images of the traces of the PCB. After correcting and high-speed A/D transforming, it sends the signals to the control subsystem to decide the defects, scanning by moving the inspection station linearly to offer the 2D image output signals. After detecting some defect, it allows real-time marking and a magnified display in the monitors, thereby easing off the judgment of vision.This system operates interactively through a monitor, with digital and real image monitoring, as well as a printer and a synchroscope, allowing digital and real images to be displayed or printed, and the image signal figures and the digital clip levels can be observed by a synchroscope. The inspection speed is several meters per minute, with a resolution at the micrometer level and minimum line width/spaces.<h4>AOI System for Solder Joints</h4>AOI for solder joints uses an optical camera for image capturing in 3D. After processing, the data is compared with standard images to detect and classify defects and their position.<h4>AOI System for Solder Paste Printing</h4>The overall system is comprised of a camera and an optical fiber x-y system. The x-y axes of the x-y table facilitate the imaging of PCBs, while an ideal condition in solder paste printing uses the paste corresponding to the thickness of the stencil. During this process, slant light is applied from the annular optical fiber and the annular reflector of the inspection system; the camera takes such images of the paste for measurement of the edges and the thickness of the paste, so the shapes are now converted into optical changes for checking.<h3>AOI Services at PCBX</h3><img src="https://img.pcbx.com/dev/file/image/article/20240814/5919f72760b04d05bf14331a9073af4d.jpg" alt="AOI Services at PCBX-PCBX" data-href="" style="width: 100%;"/>PCBX offers free AOI services for our customers who ordered PCBs and PCBA. X-ray inspection service is also provided to guarantee better quality and reliability of your products.These free AOI services help manufacturers to get complete quality control over their SMT assembly process, thus increasing the performance effectively.&lt;button class="center btn-lg" data-href="/order/manufacturing/pcba"&gt;Start Your Custom PCBA Quote Now&lt;/button&gt;

As PCBs and components shrink, AOI (Automated Optical Inspection) replaces visual inspection in SMT assembly, ensuring high-quality solder joint performance through intelligent, optical techniques.

Significance of AOI in SMT Assembly

As the lines on PCB (Printed Circuit Board) intended for SMT (Surface Mount Technology) assembly continue to shrink, along with components becoming miniaturized, and SMD (Surface Mount Device) more densely packed, the original visual inspection methods can not meet the quality demands. In turn, AOI (Automated Optical Inspection) has become a very important technology in SMT assembly for the inspection of solder joint performance. The increasingly applied and technologically developed AOI tends to intelligent inspection modes in SMT assembly.<h3>Working Principle of AOI Technology</h3>Despite the various forms that AOI can take in SMT assembly, generally, they share a common underlying technique, and that is the process of using optical techniques to capture images of the target to be inspected and analyzed, and judged based on some criteria. The commonly used methods in AOI systems are DRC (Design Rule Check), and CAD (Computer-Aided Design) data comparison.<h4>DRC</h4><img src="https://img.pcbx.com/dev/file/image/article/20240808/579bb7f3a7bc49d4946bddcf9cf67d51.png" alt="design rule check-PCBX" data-href="" style="width: 100%;"/>The DRC method applies inspection to design patterns according to predetermined rules. For example, a PCB circuit pattern can be checked to ensure that all lines end at solder joints, have the same width, and that their positioning concerning each other lies within a distance. In this manner, the DRC method could achieve that the algorithmic validity of the pattern is secured and some benefits, including easy setup, high-speed performance, minimum program, and insignificant data storage. Thus, this method is extensively used in AOI systems.However, the DRC method's limitation lies in its ability to determine boundaries, thus requiring particular methods to establish boundary positions.<h4>CAD Data Comparison</h4>Compared digital image patterns stored in the AOI system to real captured images this method could develop the inspection results. The accuracy depends on inspection precision, definition, and all the steps involved in the inspection, which means the method is highly concerning accuracy but requires high data storage and real-time behandeln capabilities.Although both techniques have advantages, the CAD data comparison method is chosen more for its gains in a wide range.<h3>Inspection Functions of AOI Technology</h3><img src="https://img.pcbx.com/dev/file/image/article/20240808/abb43c99af634429996bf11d68b46a91.jpg" alt="Inspection Functions of AOI Technology-PCBX" data-href="" style="width: 100%;"/>AOI is applied in inspecting bare PCBs, solder paste printing, components, and solder joints.In the production process, bare PCBs and solder joint inspections are usually done by separate AOI equipment, which inspects in a non-real-time manner.An AOI system often integrates solder paste and component inspection into one, including real-time inspection with solder paste printers and chip mounters. An example would be the advanced solder paste printer with two heads, capable of real-time inspection of the printing thickness and the edge collapse through AOI systems.Inspection items:Disconnection, wire-tapping, scratches, pinholes, mass-area defects, line space, and trace, edge roughness, for bare PCBs.Lead formation and bending of solder joints, missing components, misplacement, orientation of components, solder joint quality, etc.If AOI system detected unqualified components, they would usually give reminders to operators for replacement, which could help to prevent big mistakes.<h3>Structure of Common AOI Systems</h3><h4>AOI System for Bare PCBs</h4><img src="https://img.pcbx.com/dev/file/image/article/20240808/e13e6382fabe4eeb9397e09ea3fbf2e2.PNG" alt="AOI System for Bare PCBs-PCBX" data-href="" style="width: 100%;"/>This system has a comparison function and two cameras. The 1D image sensor installed in the inspection subsystem photographs the images of the traces of the PCB. After correcting and high-speed A/D transforming, it sends the signals to the control subsystem to decide the defects, scanning by moving the inspection station linearly to offer the 2D image output signals. After detecting some defect, it allows real-time marking and a magnified display in the monitors, thereby easing off the judgment of vision.This system operates interactively through a monitor, with digital and real image monitoring, as well as a printer and a synchroscope, allowing digital and real images to be displayed or printed, and the image signal figures and the digital clip levels can be observed by a synchroscope. The inspection speed is several meters per minute, with a resolution at the micrometer level and minimum line width/spaces.<h4>AOI System for Solder Joints</h4>AOI for solder joints uses an optical camera for image capturing in 3D. After processing, the data is compared with standard images to detect and classify defects and their position.<h4>AOI System for Solder Paste Printing</h4>The overall system is comprised of a camera and an optical fiber x-y system. The x-y axes of the x-y table facilitate the imaging of PCBs, while an ideal condition in solder paste printing uses the paste corresponding to the thickness of the stencil. During this process, slant light is applied from the annular optical fiber and the annular reflector of the inspection system; the camera takes such images of the paste for measurement of the edges and the thickness of the paste, so the shapes are now converted into optical changes for checking.<h3>AOI Services at PCBX</h3>PCBX offers free AOI services for our customers who ordered PCBs and PCBA. X-ray inspection service is also provided to guarantee better quality and reliability of your products.These free AOI services help manufacturers to get complete quality control over their SMT assembly process, thus increasing the performance effectively.

As PCB lines and components shrink, traditional visual inspection fails; AOI using DRC and CAD methods is crucial for quality SMT assembly, offering intelligent, accurate inspections.

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