Eight Reasons for PCB Faults
Table of Content
- What Causes a PCB to Fail?
- 1. Plating Voids
- 2. Copper Too Close to Board Edges
- 3. Copper or Solder Mask Slivers
- 4. Missing Solder Mask
- 5. Acid Traps
- 6. Thermal Voids
- 7. Electromagnetic Issues
- 8. No Guiding Design-For-Manufacturing (DFM)
- How to Diagnose the Cause of a PCB Fault
- 1. Micro-Sectioning Analysis
- 2. Solderability
- 3. PCB Contamination
- 4. Optical Microscopy/Scanning Electron Microscopes (SEM)
- 5. X-Ray
- Get PCB Test Results Without the Confusion
Printed circuit board (PCB) systems and component failures disrupt the electronic devices taken for granted at your organization. Across industries and environments, faults in PCBs spell trouble for core front and back-house work to get done — for instance:
- In manufacturing, PCB faults threaten the computerized sensors, measuring equipment, controls, pumps and drives underpinning industrial operations, as well as the security systems protecting your infrastructure and the increasingly interconnected device ecosystem synthesizing it all.
- In labs and medical environments, repairing PCBs is vital for testing equipment, measurement devices and computerized systems to stay high-functioning, keeping lab schedules and outputs productive.
- In businesses and offices, PCBs harmonize your diverse range of electronic and smart devices into functional hardware, including desktops, laptops, smartphones, tablets, scanners, point-of-purchase systems, printers, digital signage, appliances and more.
- In commercial and residential HVAC systems, PCBs are responsible for safe and stable environmental controls, regulating temperature inputs and ensuring your office, business, factory floor, facilities and homes stay within the proper temperature and humidity ranges.
There are several common reasons why your PCB may be glitching. Knowing these top PCB component or system failures prevents your team from growing overwhelmed when malfunctions strike, bolstering quicker responses, proper circuit board failure tests, cost-effective and efficient repairs and less stress.
What Causes a PCB to Fail?
PCBs are intricate assemblies of electricity-conducting copper pathways etched into grooves and tracks atop base, non-conductive boards. These electric-pathway impulses and connections are considered the bedrock of all electronics. Without high-functioning, clean and well-maintained PCBs, your organization’s electronic infrastructure cannot work as it’s designed to.
However, errors are bound to happen given PCB’s design intricacies — as well as its around-the-clock running of front and back-house devices, equipment and controls. These are the most common problems with modern PCBs leading to faults and component failures:
1. Plating Voids
Functioning PCBs send electric impulses through copper-lined tracks etched into a supportive, non-conductive circuit board base layer.
Nestled into its circuit board base, these copper wires are known as thru-holes. Circuit board manufacturers use special fabricator drills to etch thru-hole tracks according to specific designs. After drilling, they carefully plate and line copper wiring into the microscopic trenches, completing the core design of a PCB and rendering it ready for use.
Plating voids, or gaps, occur when thru-hole tracks contain any kind of imperfection interrupting smooth electric current streams. Causes of these imperfections may be due to:
- Poorly cleaned trenches prior to copper plating.
- Air bubble formations during or after the plating process.
- Improper drill movements and speeds while cutting tracks.
- Improperly lined copper wires across tracks.
The existence of thru-hole gaps or holes will cause the entire PCB to malfunction, meaning your organization will likely have to order new PCBs from a maker or manufacturer.
2. Copper Too Close to Board Edges
Copper wiring must maintain appropriate distances from the nearby edges of its supportive base layer and sit apart from other conductive components. Threading copper too close to the circuit board’s edge or conductive metals risks a myriad of design faults, including:
- Exposed raw copper wires, leading to short circuits causing shocks upon contact.
- Poorly insulated and set copper tracks more susceptible to plating voids, etc.
- Quickly corroding copper wires requiring more frequent replacements.
- Improperly spaced PCB copper wire complications.
Improperly spaced copper tracks are often due to faulty PCB design for manufacturing (DFM) specs. PCB designs should be meticulously reviewed before ordering from reputable makers to minimize this layout risk.
3. Copper or Solder Mask Slivers
Solder masks are thin layers of lacquer — usually polymer — applied onto copper tracks before plating the pathways with any copper itself. The purpose of solder masks is to protect the copper from oxidation and erosion, as well as prevent gaps and bridges from forming between parallel conductive components, preserving the integrity of the PCB’s overall design.
Copper and solder masks slivers are tiny, broken chunks of copper wire or solder polymer that detach from its original placement. When these slivers break off, they can trigger two main issues:
- Unplanned conductive connections rendering the PCB defective.
- Exposed core copper plating, causing short circuits that also render a PCB defective.
4. Missing Solder Mask
Copper is a highly conductive material used to carry and route electric currents since the origins of the telegraph. Yet, its hyper-conductivity also courts a few downsides, namely the metal’s susceptibility to corrosion and oxidation.
To prevent onset rust on copper wires, PCB makers will coat trenches with those lacquer-polymer solder masks or similar protective layers. Those solder masks are instrumental in preventing corrosion and copper oxidation, but they will wear over time, leaving wiring exposed.
What’s more, trimming copper wires can scrub the solder mask off portions of a wire’s surface. Even minuscule amounts of trimmed solder masks heighten the PCB’s risk of short-circuiting and causing electric shocks, particularly if two exposed copper wires or plates come into contact.
5. Acid Traps
Take a good look at the next circuit board or circuit board picture you come into contact with. You’ll immediately note the near delta-like stream of copper wires webbing its way around the surface.
What you won’t — or shouldn’t — notice are numerous acute angles of wire tracks. This is done intentionally. Acute-angles and similar narrow, sudden track pathways increase the likelihood that acid will build up from drilling tools making contact with metal and other PCB materials during wire-etching fabrication. Such chemical acid deposits rapidly eat away at solder masks and the copper itself, permanently compromising tracks even if the build-up is removed.
6. Thermal Voids
Thermal voids, or starved thermals, refer to several issues which result in overheated PCBs. To understand a thermal void, you must first understand the temperature components involved in safely padding and transferring heat within a circuit board. There are three main electronic components involved in this important heat transfer:
- Planes/panels: At its simplest, a PCB plan or panel is the underlying, non-conductive, supportive layer thru-holes, surface mounts and other circuit components are etched into. At a minimum, a PCB must have at least two planes, one for circuit powering and one for circuit grounding.
- Pads: Pads are small, pin-like soldering points that allow PCB components to be connected to the panel.
- Thermals: Thermals surround pads, dispersing heat during moments of system stress, particularly during a PCB’s drilling and plating production steps.
Thermal voids and starved thermals strike when these thermal pieces aren’t properly configured or placed during the production phase. As a result, pads and planes experience higher rates of heat stress and more inefficient heat transfer, reducing your entire PCB unit’s durability and longevity from day one.
7. Electromagnetic Issues
General electromagnetic issues are typically the result of a PCB design flaw rather than a single piece or component failure. These electromagnetic issues express themselves in dozens of ways, including:
- Too little ground plane area in the PCB design.
- The existence of sharp, acute angles in the PCB design.
- A lack of shielding cables or metallic protective sheathing to reduce electromagnetic interference.
- Other electromagnetic compatibility or interference faults, each resulting in poor electricity conduction and, therefore, a poorly functioning circuit board.
8. No Guiding Design-For-Manufacturing (DFM)
Creating a streamlined, efficient and reliable printed circuit board requires foresight. Makers don’t merely assemble all components, stack pieces together then start soldering away.
Instead, trusted PCB manufacturers ideate detailed circuit board topography with the end-goal of DFM (design for manufacturability). DFM principles ensure there are no oversights across the layout, plating, trenching, heat transferring, soldering and other fabrication and manufacturing steps for creating final PCB products. What’s more, DFM software and prototype testing can preempt design weak-spots, uncovering the most likely system or component faults based on design specs.
How to Diagnose the Cause of a PCB Fault
Understanding PCB fault causes without the right expertise or approach can feel like spotting a needle in a haystack. Certain glitches might be visually obvious, such as eroded or burnt components damaged by a heat incident. However, other malfunctions will be imperceptible to the eye and require multi-phased, integrated circuit tests and multimeter readings to identify the source of the system fault, followed by an appropriate component replacement, cleaning or system re-installation.
Get to the root cause of your business’ PCB problems once and for all with these methods for root-cause analysis, each endorsed by circuit repair specialists:
1. Micro-Sectioning Analysis
Micro-sectioning, or cross-sectioning, is a form of PCB fault identification where technicians cut and remove portions of a printed circuit board to test individual layers and components.
This methodical approach is known as a destructive testing method, as it requires the disassembly of the PCB. However, micro-sectioning provides repair specialists with a granular and precise methodology exploring possible components in an isolated manner, allowing them to accurately confirm the source of faults.
Micro-sectioning analyses work best for the following perceived PCB problems:
- System shorts
- Material evaluations
- Thermo-mechanical glitches
- Solder reflow failures
- Overall processing failures
As the name suggests, a solderability analysis focuses on solder and mask-related damage. Undertaking solderability testing will let your organization uncover the state of solder-related components, as well as how misapplied or weathered soldering may be contributing to your organization’s underperforming PCBs.
However, to conduct a proper solderability test, analysts must have the tools and expertise to review surface conditions and administer appropriate surface testing techniques. They must also understand how certain conditions may affect the faults of soldering components, such as PCB storage, age and other environmental controls affecting total PCB quality.
Consider performing solderability tests for the following functions:
- Component and track polymer/lacquer evaluations
- Solder and solder mask analysis
- Flux and pad evaluations
- Overall PCB coating health and durability
To identify the right solderability failure experts, inquire about IPC-J-STD 002 and 003, which are the practicing standards for all solderability tests.
3. PCB Contamination
Many contaminants can impact the health and functionality of your PCB components. In fact, a PCB is most at risk for contamination during its fabrication stages, where manufacturers must use several chemical and cleaning agents alike to create electronic circuit boards.
Even PCBs fabricated in the cleanest and most controlled environments risk exposure to contaminating elements, such as:
- Oils and residue from manual handling
- Hot air leveling agents
- Chemical copper etching solvents
- Electrolyte cleaning and finishing solutions
- Water-based and water-soluble soldering techniques
During a PCB contaminant test, analysts will test and measure for traces of ionic compounds held within a PCB component sample. Samples are placed within special solutions that dissolve ionic materials, triggering property changes in the solution itself, which is then measured, recorded and interpreted for source faults.
4. Optical Microscopy/Scanning Electron Microscopes (SEM)
Optical microscopy and SEM tests use ultra-powerful microscopes to analyze PCB samples at extreme magnifications.
With precise depth fields and detailed image recording or capture capabilities, many analysts use optical microscopy and SEM as a first approach to investigating malfunctioning circuit boards, since these methods are so astute at spotting core design flaws. Both optical microscopy and scanning electron microscope equipment provide detailed images for fault analysts to decipher, capturing circuit defects or design flaws as small as a few nanometers wide.
Optical microscopy exams work well to identify numerous PCB fault cases, such as:
- PCB board and plane misconstructions, integrity flaws and general surface damage.
- Cross-section construction flaws.
- Heat treatment effectiveness.
- Copper and other PCB alloy metals’ quality.
Optical microscopy and SEM are popular methods for finding PCB faults because of their straightforward testing steps as well as accurate, image-based results. The most common applications for these two testing types reveal poor underlying PCB construction.
Last but not least, fault analysts may perform x-rays on PCBs to narrow down fault sources before actually taking apart a PCB unit.
The benefits of x-rays for circuit board testing include the fact its non-invasive, non-destructive physical testing methodology. Unlike micro-sectioning and other fault-finding methods on this list, PCB x-rays allow for internal explorations of an entire PCB system — sans the slow, painstaking disassembly. This makes x-rays a go-to choice for fault-testing early PCB prototypes as well as performing thorough, high-quality DFM fabrication practices.
Turn to x-ray PCB fault tests when PCB glitches could be associated with:
- Contaminant, residue or particle damage.
- Wire dress or sliver issues.
- Gaps or voids in sealing masks.
- Plate, substrate and wiring board quality reviews.
- Soldering quality reviews.
- A range of similar electromagnetic issues based on poor fabrication.
- And much more, given this technique’s fundamentally non-invasive approach.
Get PCB Test Results Without the Confusion
There’s no way your organization can run without electronics — commercial or industrial. And there’s no way for electronics to run without high-functioning PCBs.
Turn to Global Electronic Services for your PCB testing and fault-identifying toolkit. We offer:
- Certified, factory-trained technicians.
- Repair turnarounds in as little as one day.
- Upfront pricing with no hidden fees, charges or surprises.
- An 18-month in-service warranty (doubling the industry standard).
With Global Electronic Services as your side, you simplify the often convoluted and time-consuming process of fixing and repairing circuit boards both preemptively and when emergencies strike, plus work to understand the environments and causes that led to PCB faults to begin with.
Reach out with PCB repair and maintenance questions, or to schedule a review today.