Oct 30, 2018|Blog
Printed circuit boards are what make our electronics function as intended. So, when something malfunctions on the PCB, chances are the electronic device will stop working. PCB problems can be a big headache for manufacturers because many things can go wrong at every step of the design and assembly processes.
We created a list of some of the most common PCB problems people face. By knowing these issues, you can keep them in mind while building your board in hopes of avoiding them and causing damage to your PCB.
Burnt Circuit Board
Table of Contents
- 1 Burnt Circuit Board
- 2 Poorly Manufactured Components
- 3 Bad Soldering
- 4 Environmental Factors
- 5 Age
- 6 Plating Voids
- 7 Insufficient Copper-to-Edge Clearance
- 8 Slivers
- 9 Missing Solder Mask Between Pads
- 10 Acid Traps
- 11 Starved Thermals
- 12 Electromagnetic Issues
- 13 Not Using a DFM
- 14 Chemical Leakage
When manufacturing a PCB, the board is exposed to high temperatures throughout the process. It is common for components on the PCB to burn from the heat. Since each component can only withstand a certain amount of heat, if there is not enough space around the component, it eventually will burn.
Poorly Manufactured Components
Poor manufacturing is another common problem with PCBs. You’ll notice this problem as a result of loose components, connection troubles, and residual flux or a bad solder. The flux is a substance for soldering and can do a lot of damage to the components if left on the board.
Poor soldering can cause many issues in a PCB. Cold soldering happens when the technician doesn’t properly heat the solder. Moisture can also contaminate the solder, resulting in connection issues and the potential of components burning.
If the PCB is frequently exposed to environmental elements like heat, cold, dust, and moisture, it could lead to PCB problems. As the temperature changes, elements may expand or contract, which could warp and damage the board and soldering joints.
Too much moisture in the PCB could lead to oxidation, corrosion, and rust. If there is an excess of dust in the area of the PCB, the dust particles can build up and clog the board causing it to overheat.
Unfortunately, aging components are a common issue with PCBS that are beyond your control. As the components get older, they begin to lose their quality and break down. However, you can replace particular parts versus having to rebuild the whole board.
When plating thru-holes in the PCB, you will drill holes and puncture the materials on the PCB all the way through, and follow up with adding a layer of copper through an electroplating process. This will add a thin layer of electroless copper or with a direct metallization process using graphite to the PCB, a process known as deposition.
Through the deposition, it is possible to create voids in the plating. These voids are gaps or holes in the plating and can prevent electrical currents from passing through the whole. If there was not an even layer added through the deposition process, it could cause air bubbles, contamination, and many other issues.
Insufficient Copper-to-Edge Clearance
Because copper is a conductive metal, it is an active component of a PCB. However, copper can also cause many PCB issues because it is vulnerable to corrosion. To prevent corrosion from occurring, other materials cover the copper. When you trim the PCB though, if there isn’t enough clearance between the copper and the edge of the PCB, the coating will also be trimmed and cause the copper to be exposed.
During the PCB manufacturing process, small wedges of copper or solder mask, known as slivers, can form and cause numerous PCB problems. There are two common ways a sliver may occur. The first is when a long, thin piece of copper or solder mask gets etched away. Instead of dissolving in this process, it detaches and falls into the chemical bath, potentially landing on another board.
The second way is when you cut a part of the PCB design too deeply or narrowly. The etched area can detach from the board and cause either a floating sliver or a peeled-back sliver.
Missing Solder Mask Between Pads
The solder mask is what covers the PCB board’s copper layer. It helps protect the copper from the environmental elements, corrosion, and insulates the copper traces. The metal left exposed, which components are soldered to, are known as pads.
In some cases, there may not be enough solder, or none at all, between the pads. When this happens, it exposes the copper and can form a solder bridge during assembly. The solder bridge will lead to a short exposure to copper and the inevitable PCB problems.
Acid traps are also known as acute angles. They get the name acid traps because during the etching process, the angles trap in acid, if using ammonia based etching. The acid then stays in the corner for longer than what the design asks for, causing the acid to eat away at more materials than initially planned. This can result in compromised connections and circuit defects. Candor uses cupric chloride etching, which does not have this problem.
The small traces around the pads, which connect them to the plane, are known as thermals. They help the pads disperse heat and are key components for the soldering process. When voids form between the thermal and the pad or plane, it will lead to an incomplete connection. The result is less heat transfer. PCBs with starved thermals are then prone to overheating and the subsequent damage.
Electromagnetic compatibility (EMC) and electromagnetic interference (EMI) are two issues that are common on PCBs. EMC generates, propagates, and invites electromagnetic energy. EMI is the unwanted and damaging effects from the EMC. If there is too much EMI, the result is a defective board. Quite commonly, electromagnetic issues are from design flaws.
Not Using a DFM
DFM stands for Design for Manufacturability. It refers to the process of inspecting the board’s layout to eliminate as many issues that could arise during the assembly process. DFM is there to ensure the result is a functioning PCB. Not using DFM checks could mean that the manufacturer missed potential errors that could have been fixed before assembling the PCB.
There are many different chemicals used throughout the manufacturing process of a PCB. Although there are steps to ensure all traces of each chemical is cleaned away, there is the possibility of small traces being left behind. Chemical leakage will eventually cause corrosion and short-circuiting.