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How to Do Printed Circuit Board Failure Analysis?

From smartphones and cheap toys to radar detectors and sophisticated computers, the printed circuit boards (PCBs) form a very important component for the industrial and electronic technology of today.

Almost all electronic devices feature these complex electronic components that include capacitors, resistors, fuses, and diodes. Furthermore, the PCB (printed circuit board) can either cover just one task or many (multiple functions). There are three major types: multilayer, double-sided, and single-sided.

This industry is focused on achieving more miniaturization, with the need for design engineers to manufacture smaller, more complex, and faster, circuit board technology, costing less and having a higher quality improvement.

The printed circuit board needs to offer its support and function for larger electronic devices. Consequently, there must be a system for the PCB manufacturers that can monitor and test each of the components to make sure that it works in line with the different standards and offers maximum performance.

Anytime a component fails, then analysts must make use of different techniques, tools, and processes. With accuracy, these analysts must know the reason for that failure location and take measures on how to avoid and prevent future failures.

These processes below present some challenges for possible electronics failure analysis. These include:

  • Recycling requirements
  • Increased density
  • The importance of tuning PCBs to its precise values
  • Higher lead-free temperature requirements
  • Hazardous material
  • Other changes associated with PCB manufacturing

Analysis of the Root Cause

Fabricating a PCB assembly needs different materials and machines. These include solder paste, conveyors, reflow ovens, pick-and-place systems, conveyors, and automated optical inspection.

There are machines that feature automated features, which perform checks at different points, and the operators deliver visual inspections or appearance inspection immediately after, during, or before a task is completed.

However, majority of printed circuit boards (PCBs) usually fail the last test. When this issue happens, performing a reliable electronics failure analysis so as to get precise and clear detains regarding the problem source, and to make sure that the problem doesn’t arise again.

The technician has to conduct the root cause analysis. This helps in identifying the reason for the failure mechanism. It will also take actions to correct the issue. Also, with this quantitative analysis (failure analysis), designers will get invaluable feedback on ways to improve their product and correct little faults that were not seen during the first and initial design. It helps in improving the product.

Companies producing electronic hardware usually make efforts in achieving zero-defect production. In order to make this objective a reality, manufacturers should have the ability to perform some printed circuit board failure analysis. There are companies that bank on expertise from outside to achieve more complex issues or problems.

For high-reliability systems like implantable devices for the medical field, space satellites, as well as other systems, having pcb failures could be devastating. For consumer products, where there is one failure mode, that could replicate so many times.

Failure analysis offers a step by step process that assists organizations in investigating and understanding the reasons why a specific electronic part has failed. Also, depending on the failure’s nature, a better and effective investigation has the ability of identifying the elements and mechanism.

Types of Failure Analysis Tests

Some tests are suitable for the identification of defects. Anytime these failure analysts comprehend these faults, as well as ways of preventing them, this company helps in improving the entire production process coupled with assemblies that it manufactures.

 Furthermore, the traditional techniques needed for PCB failure analysis focuses on the slice & dice method. The technique makes use of different external techniques like X ray inspection, visual inspection, electrical testing, and cross-sectioning the area.

The PCB tests below feature the highest rate of success. It also provides benefits for different PCB manufacturers.

Solderability Testing

With reference to the IPC-T-50, the base solderability has to do with the ease at which you can wet a metal alloy or metal material surface by molten solder, with minimum conditions. Most times, the process of PCB manufacturing could be a source of problems in the assembly. This includes problems related to misapplications and oxidation of a solder mask.

To help reduce the failure’s probability, a good number of manufacturers test the ability of the PCB pad solder and the component to make sure of the surface’s robustness, as well as increase the chance of creating a solder joint that is reliable.

This failure method helps in evaluating the quality and strength of wetting the solder. This is by the reproduction of the contact formed between the material and the solder.

This process of wetting balance helps in measuring the wetting force as well as the contact time to the generation of the wetting force. With solderability testing, you will be able to verify that these components will meet the necessary quality standards and specifications.

This technique also helps in determining the effect of the solder components on the printed circuit boards (PCBs). This also offers a better measure of why this fault might have happened. Also, solderability testing functions for different applications, which includes quality control, benchmarking, flux evaluation, solder evaluation, as well as the evaluation of the PCB coating.

In addition, analysts conducting pcb failure analysis should have the experience necessary to differentiate the different surface conditions. Also, they must comprehend the testing technique requirements that are acceptable. Also, this analyst should have the expertise needed to apply the conditions accurately.

 Micro-sectioning Analysis

This is at times referred to as metallographic preparation or cross-sectioning. This has to do with a PCB testing method that is useful in investigating the following.

  • Shorts or opens
  • Defects in components
  • Evaluations of raw materials
  • Thermo-mechanical failures
  • Processing of failures as a result of solder reflow

Also, the failure analyst gets rid of slice of two dimensions from the sample. This helps in uncovering the features present in the board. This method gives the technician an accurate technique that helps in isolating the right electronic components. It also removes that part from your PCB sample.

Furthermore, the technician places the component in an epoxy resin, as well as another potting medium.  He or she then allows it to solidify after curing. Once the component has cured, the technician now makes use of the abrasion technique in receding and exposing the components. Next, the technician polishes that part till it becomes reflective as well as ready to undergo testing.

In addition, this method needs the analyst to draw a comparison between the sample other functioning components. A benefit of this method of testing is that the sample has the ability of positioning on the flat surface and also invests its parts together.

Optical microscopy and scanning electron microscopy equipment helps in examining plate thickness, layer thickness, as well as failure to the solder joints. Also, the analyst has to highlight the damages and also identify what has caused the destruction. ASTM E3 and PC-MS-810 quality standards also help in governing the micro-sectioning tests.

Optical Microscopy

This could be the most preferred and popular testing method that is useful in detecting problems, defects, and faults that are linked with assembly and soldering. Many customers prefer the use of optical microscopy due to its accuracy and speed.

This process makes use of high-power microscope having visible light. This microscope, which has the ability of reaching 1000X, shows different features in a plane and with a small or little depth field. Board integrity poses a significant concern as well as frequent causes of failure in different electronics.

Microscopy testing helps in verifying improper construction that can result in stresses, which could expose flaws present at different cross sections. At times, PCB failure analysis needs stronger magnification tools. SEMs (scanning electron microscopes) provide a very effective technique for testing for failure analysis of semiconductors.

Even if an issue or defect in the integrated circuit only measures a few nanometers in width, scanning electron microscopes offer the failure analyst some detailed images and at a higher magnification of about 120,000X. Typical magnifications can reach 50,000 – 100,000X. Feature resolutions can be 25 angstroms. This analyst makes a recording, and then records the findings with respect with the images.

This technology ensures that the field’s depth offers the failure analysts with the sample’s three-dimensional view. With SEM examinations, it also makes it possible to verify the quality, integrity, and metallization of the semiconductor die. Also, with SEM, it provides the evidence of a heat treatment. It also identifies the alloy or metal used. In addition, the majority of analysts pair the SEM with the micro-sectioning testing.

Testing for PCB Contamination

Contamination can result in different issues. These include degradation, metallization, corrosion, and a quick deterioration. Though the processing and assembly of a PCB usually occurs in a very neat environment (environmental factors) that are designed to ensure that the components are free from any contamination. Also, infection usually occurs and it represents a cause of PCB failure.

Reaction products, the byproducts of humans, flux residues, and handling, are the major sources of any contamination. Majority of manufacturers usually make use of chemistry processes when PCB fabrication is on. These include electrolytic solutions, liquid for copper etching, water-soluble soldering, and hot air leveling fluxes.

There is a need for cleaning when using chemicals. This is why the electronics industry brought what we call ionic contamination testing. This measures the stability and efficiency of your cleaning process. It also plays a huge role in measuring the ionic contamination present in the sample. The testing process deals with immersing the sample of the PCB in a solution. This solution then dissolves its ionic contamination that leads to a change in the solution’s constitution. It will also have a great influence on its readings and values.

This PCB failure analyst or technician also measures or calculates the change occurring in the solution solvent resist. When the reading surpasses the established level, this means that the manufacturer faces an issue concerning the cleaning process. Also, this can lead to detrimental effects including electrochemical migration and corrosion, where parts stay inside the component. The dissolving technique can even detect the smallest parts.

A benefit of contamination analysis is the accuracy and precision that it carries. Contamination analysis has to meet the IPC-TM-650 standard.

X ray Inspection

Many x rays offer users a reliable tool for any failure analysis that is non invasive. Choosing a basic film X ray, 3-dimensional x ray system, and real time x ray, users will be able to employ the necessary tools in detecting the potential or actual defects.

Furthermore, they could inspect components having hidden parts or solder joints located under a chip. Then the analyst makes use of the X ray inspection rather than use visible light equipment in evaluating the printed circuit board (PCB).

Even when using the basic capability for X ray fluoroscopy or inspection, technicians can go ahead to conduct the following examinations for its internal components.

  • Internal wire dress
  • Internal particles
  • Quality of the die attach
  • The integrity of the substrate or PCB trace
  • Poor, excessive, or insufficient solder

This method of testing has a major benefit. It is its ability in detecting internal and surface flaws in a constructive manner. It still keeps the samples in the pre-testing condition.

What are the Common PCB Issues or Challenges?

PCB fabrication comes in many moving parts and steps. The manufacturing process offers many opportunities to bring in defects into the mix, and unintentionally.

Consequently, those engaging in PCB failure analysis face different challenges when searching for manufacturing defects. These include

  • Lead-free assembly process
  • High-speed PCB (printed circuit board)
  • Conductive anodic filament
  • Plated through cracking
  • Accurate surface finish choice

Conclusion

Whatever the case is, PCB manufacturers have to ensure they take care when adhering to the exact specifications and tolerances in order to avoid any failure. Also, there is a need to work with an effective PCB failure analysis to help in the probing and investigation of the systems and components. It will also make the necessary improvements to the quality.