From cheap toys and smartphones to sophisticated computers and radar detector systems, printed circuit boards (PCBs) are critical components for today's electronic and industrial technology. Almost every electronic device has one of the independent modules of complex interconnected electronic components, including resistors, capacitors, transistors, diodes and fuses.
The electronics industry is turning to more miniaturization, leading design engineers to produce faster, smaller and more complex circuit board technology with higher quality and lower cost.
It is important that the printed circuit board performs its function and supports the larger electronic device. As a result, PCB manufacturers must have a system that monitors and tests each component to ensure it meets various standards and ensures maximum performance.
When a component fails, analysts should use various processes, tools, and techniques. They must accurately determine why the device has failed and how it will prevent future malfunctions. The following operations present unique challenges for electronic failure analysis:
The production of a complete PCB assembly requires a number of machines and materials, including:
Some machines have automatic features that perform checks at various points, and operators perform visual inspections before, during or immediately after a task is completed.
However, many PCBs will probably fail in the final test. When a problem arises, it is important to conduct an effective electronic failure analysis to get clear and precise details about the source of the problem and to ensure that the problem does not happen again.
The technician should perform root cause analysis - not the symptoms - to determine the cause of the error and take corrective action to resolve the problem. Failure analysis also provides design engineers with valuable feedback on how to:
Any company that produces electronic equipment tries to achieve zero defect production. To achieve this goal, manufacturers must be capable of performing some printed circuit board failure analysis. Some companies rely on external expertise for more complex problems.
Malfunctions can be devastating for many high reliability systems, such as oil platforms, space satellites, implantable medical devices, and other systems. When it comes to consumer products, a single failure mode that can be replicated thousands or millions of times can ultimately have a big impact.
Electronic device failure analysis provides a systematic process to help organizations investigate and understand why an electronic component has failed. Depending on the nature of the failure, an effective research can identify the failure mode, the mechanism, and the factors that determine the stresses and other problems causing the failure.
For example, solder joint errors largely constitute PCB failure. Manufacturers can discover the root cause of defective connections such as lack of solder paste, gap between the PCB pad and component cable, or poor reflow profile, and then apply preventive measures. To eliminate future malfunctions, there may be possible solutions to avoid solder paste contamination or to ensure the correct aspect ratio. The methods used in the analysis depend on the severity of the failure and the type of problem. They can range from simple electrical measurements to the evaluation of sample sections under a microscope.
An effective and effective root cause analysis enables manufacturers to initiate the necessary corrective action to prevent the problem from recurring. Error analysis processes evaluate the reliability of a working component product and determine how the product is developed.
There are a number of appropriate tests to identify errors. Once the failure analyst understands errors and how to prevent them, they can improve the production process and the assemblies it produces.
Traditional techniques used for printed circuit board failure analysis focus on the "slice and dice" method. This technique uses a combination of external techniques, such as electrical testing, visual inspection, x-ray, and sectional area.
The following PCB tests have the highest success rate and offer advantages for PCB manufacturers:
Micro-section, sometimes referred to as Section or Metallographic Preparation, refers to a PCB test method used to investigate:
Thermo-mechanical failures
Component errors
Open or shorts
Machining errors due to solder reflow
Raw material assessments
The error analyst removes a two-dimensional slice from a sample, which reveals the features on the card. Micro-section analysis, considered a destructive test method, provides the technician with a precise technique that isolates the relevant electronic component and removes the part from the PCB sample.
The technician puts the component in an epoxy resin or other potting medium and leaves it to harden and harden. After the component has hardened, the technician uses a wear technique to retrieve and reveal the component and polish the part until it is reflective and ready for testing. The micro section requires the analyst to compare the sample with another processing component. An advantage of this test method is that it can place the sample on a flat surface and invest each part together.
Electron and optical microscopy equipment can examine plate thickness, intermittent metallic layer thickness, or defects in solder joints. The analyst should emphasize the damage and identify the cause of the destruction. PC-MS-810 and ASTM E3 quality standards regulate micro-section tests.
According to IPC-T-50, "base solderability" describes the ease of wetting a metal or metal alloy material surface with molten solder under minimum realistic conditions. Generally, the source of PCB manufacturing process assembly problems can be issues related to oxidation and misapplication of the solder mask. To minimize the possibility of failure, most produce test component and PCB pad soldering ability to ensure the stability of the surface and increase the probability of creating a reliable soldering joint.
The solderability failure method re-establishes the contact between the solder and the material and evaluates the wetting power and quality of a solder. The soak balance process measures the soak force and the time from contact to the soak force. The solderability test can verify that the components will meet specifications and quality standards.
The technique also helps to determine what effect storage, if any, on soldering components has on PCBs. It also provides a precise measurement of why an error occurred. Solderability testing works for a variety of applications, including:
PCB coating evaluation
Solder assessment
Flux assessment
Comparison
Quality control
Failure analyst should have experience distinguishing various surface conditions and understanding acceptable requirements of the test technique. The analyst must also have the necessary expertise to properly apply certain conditions. The IPC-J-STD-002 and 003 standards regulate all solderability tests.
Contamination can cause various problems such as corrosion, deterioration, metallization and rapid breakdown of wire bond interconnections. Although printed circuit board processing and assembly is done in an extremely clean environment designed to keep air and components away from contamination, infection occurs and represents one of the most common causes of part failure.
Human by-products, use, flux residues and reaction products are often sources of contamination. Many manufacturers use aggressive chemical processes during PCB manufacturing, which include:
Copper engraving fluid
Hot air leveling powders
Electrolytic solutions
Water soluble soldering
The use of chemicals typically requires a cleaning process. The electronics industry has launched the ionic pollution test, which measures cleaning efficiency and stability of the cleaning process. The contamination test measures the amount of ionic contamination in a sample. Contamination testing involves immersing the PCB sample in a solution. The solution dissolves ionic contamination, which causes a change in the structure of the solution and has a significant effect on values or readings.
The technician measures the change in the resistance of the solvent solvent - a resistance change that a failure analyst can measure. The analyst then draws the level of pollution into a pollution test curve and compares the value with industry standards.
When a reading exceeds a specified level, it verifies that there is a problem with the manufacturer's cleaning process. This can cause harmful effects, including corrosion and electrochemical migration, when the components remain in the component. This decoding technique can detect even the smallest parts.
One of the advantages of contamination analysis is its sensitivity and accuracy. Contamination analysis must meet the IPC-TM-650, method 2-3-25 standards for iconic cleaning.
Optical microscopy can be one of the most popular and preferred test methods used to detect soldering and assembly-related errors, defects and problems. Many customers choose optical microscopy because of its speed and accuracy. The process uses a high-powered microscope with visible light. The microscope, which can reach up to 1000X, has a small depth area and displays the features in a single plane. Card integrity represents a major concern in electronics and frequent cause of failure. Microscopy testing can verify the inappropriate structure that can lead to stresses that can reveal defects in certain sections.
Sometimes PCB failure analysis requires more powerful magnification tools. Scanning electron microscopes or SEMs provide a highly effective test technique for conducting semiconductor mold failure analysis. Even if a defect on the integrated circuit is only a few nanometers wide, the SEM failure analyst provides detailed images at higher magnifications up to 120.000X. It is typical to have a magnification of 50.000 to 100.000X and resolutions up to 25 angstrom. The analyst creates a record and record of the findings based on images.
With SEM technology, the depth of field provides error analysts a three-dimensional view, for example. SEM exams can verify semiconductor mold metallization, integrity and quality. SEM also provides evidence of heat treatment and identifies the metal or alloy used. Many analysts pair SEM with a micro-sectional test.
Many x-rays provide users with a powerful tool for non-invasive failure analysis. With basic film X-ray, real-time X-ray and 3D X-ray systems options, users can use tools to detect real or potential imperfections. They can also examine hidden joints or a component with parts located under a chip. The analyst uses an X-ray examination instead of visible light equipment to evaluate the PCB.
Even with basic X-ray inspection capabilities, technicians can perform the following types of internal component examinations:
Inner particles
Inner wire dress
Mold insert quality
Gaps in the sealing cap
Substrate / printed circuit board monitoring integrity
Insufficient excess or weak soldering
The advantage of this test method is that it can detect surface and internal defects in a non-destructive manner while keeping samples under pre-test conditions.
Besides rapid innovation, shrinkage components and sophisticated circuit geometries, the production of a printed circuit board consists of many steps and moving parts. The nature of the manufacturing process provides many opportunities to accidentally bring a defect to the mixture.
As a result, failure analysts face several difficulties when finding manufacturing errors:
High Speed Printed Circuit Boards (HSCBs) HSCBs that are becoming more complex and using a variety of integrated components continue to gain popularity. However, the components require cards of two or three materials that increase the possibility of failure in extremely high speed applications. Errors are also caused by pins and chips incorrectly placed on the board.
Lead Free Assembly Process - The lead-free assembly process requires a higher temperature and traditional tin-lead soldering, resulting in higher temperatures for reflow and wave soldering. This results in a negative effect on solder connection and electronic components. Check out the NTS Tin Mustache Test services.
Coating Barrel Breaking - The most common failure mode is the muzzle fatigue, which is the environmental cracking of the copper coating that forms the coating hole (PTH wall). It is the result of differential expansion between the copper coating and the out-of-plane thermal expansion coefficient (CTE) of the printed plate.
Choosing the Right Surface Finish - The most important decision for electronic assembly can be surface supply, which affects process efficiency, required rework amount, field failure rate, ability to test, scrap rate and cost.
Conductive Anodic Filament Conductive Anodic Filaments (CAF) or metallic electro-migration describes an electrochemical process involving the transport of a metal through a non-metallic environment under the influence of an applied electric field. The condition causes current leakage, intermittent electrical shortening, and dielectric distortion between the conductors in the PCBs.
However, PCB manufacturers should take care to follow strict tolerances and specifications to avoid malfunctions. This requires an effective root cause analysis to investigate and inspect components and systems and to make the necessary quality improvements.
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