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Introduction
Ionic contamination is a very common problem in printed circuit boards that really needs to be addressed. It can affect the quality of your PCBs, and it’s important for you to understand this issue so that you know how to prevent it.
Brief Description of Ionic Contamination
It occurs when non-metallic impurities are introduced into the board during the manufacturing process. The most common culprits are dirt and dust, which can get mixed into the solder and leave behind unwanted particles.
It is also a phenomenon that occurs when salts are left in a circuit board after soldering. It can cause corrosion, which can damage the circuit board and lead to the failure of electronic components.
Ionic contamination has been found to cause all sorts of problems, from improper connections to overheating, and it’s also been known to reduce the lifespan of your electronics.
Ionic Contamination
How is Ionic Contamination Measured?
An ionograph is a device that measures the amount of ions in the air. The ionograph has a number of sensors, each one sensitive to a different type of ion. When an ion gets near one of these sensors, it creates an electrical charge and sends it to the computer system which records the data.
The ionograph is placed in a clean room and then the operator scans through the different sensor settings until they see an increase in ion readings. This is done by holding a piece of circuit board up to each sensor so it can be scanned for contamination.
Once all the sensors have been checked, if there is no evidence of contamination on any of them, then we know that there are no contaminants present at all. If there are indications that some kind of contaminant exists, then we will take steps to clean up those areas before moving forward with our manufacturing process so that we can avoid any possible issues later on down the road when it comes time for assembly or testing.
Why is this a Problem in your PCB?
Ionic contamination is a serious problem in your PCB. It can cause:
Electrochemical Migration
The process starts when an ionic contaminant is deposited onto the surface of your PCB. When an electrical current passes through this deposit, it causes a chemical reaction that creates new ions and results in an electrical field around the deposit which attracts more ions. This causes a buildup of ions around the initial deposit, which leads to a flow of current between the two points where they meet.
This process can cause corrosion on copper traces, which can lead to shorts or other problems with electrical connections within your product. In some cases, it can also affect other parts of your product (like batteries) by causing them to corrode as well.
Electrochemical Migration
Dendritic Growth
Dendritic growth occurs when ions that are present in the electrolyte (the liquid that conducts electricity) of the PCB’s insulating layer bond to the copper atoms in the copper tracks on the board. This is a big problem because it can lead to corrosion, which causes defects and poor performance.
Dendritic Growth
Corrosion
Ions are charged particles that are released by ionic contamination, and these ions will corrode nearby metal surfaces. The corrosion causes the metal to break down, which can lead to short circuits and other issues with your circuit board.
Corrosion
Measurement Techniques
It can be difficult to pinpoint the source of the ionic contamination, but it is important to do so as soon as possible so that you can take steps to fix the problem and prevent future occurrences.
There are several different ways to measure ionic contamination, including:
Resistivity of Solvent Extract (ROSE) Test
A simple, non-destructive method to detect ionic contamination in printed circuit boards. The test involves immersing the PCB in a solvent that will dissolve any contaminant. The contaminant, which is usually an electrolyte, dissolves into the solvent solution.
The ROSE test measures the change in electrical potential between two electrodes immersed in a solution. In this case, one electrode is connected to the ground and the other is connected to the PCB being tested. The current flowing between these two points will vary depending on how much of a particular substance is dissolved in the solvent solution surrounding them: if there’s more of it present, there will be more ions present as well; if not, there will be fewer ions present as well.
Resistivity of Solvent Extract Test
Ion Chromatography (IC) Test
The analyte is dissolved in a suitable solvent and introduced to the column through a syringe. The solvent is allowed to pass through the column, which separates the analytes based on their charge-to-mass ratio. A conductivity detector detects the presence of ions based on their change in conductivity with time.
The IC test can detect all types of ion contamination, including ions such as chloride, fluoride, sodium, potassium, copper, and cadmium. The IC test can also be used to determine if the PCB has been over-cleaned or if any traces of solvent remain on it.
Ion Chromatography Test
Possible Cause of Ionic Contamination
There are many ways that ionic contamination can occur, but here are some of the most common:
Dirty Bare Board
This is typically the cause of ionic contamination in printed circuit boards. This is because the bare board has no coating, and the surface is exposed to the environment. Dirt and dust can easily get trapped under the copper traces and pads on the PCB, which will cause a short circuit when electricity is passed through them.
Moisture in PCB
This contamination can cause a number of problems including corrosion, reduced electrical performance, and even complete failure. The most common cause of ionic contamination is moisture in the PCB. This can occur when there is a leaky seal or other openings on the PCB which allows water to enter through physical means.
Flux Residue
This is also a common cause of ionic contamination in printed circuit boards. The flux is applied to the board during manufacturing to help the solder to flow and form connections between the different layers of the board. After the board is manufactured, any remaining flux residue can become ionic contamination.
Etching Chemicals
Ionic contamination can result from the use of etching chemicals that contain metal ions. The metal ions can become embedded in the circuit board’s surface, creating a conductive path between two points on the board. This is because the etching chemical reacts with the copper in your circuit board, which then causes the copper to become ionized. The ions can then cause electrical fluctuations and short circuits.
Drilling and Plating Residue
A possible cause of ionic contamination in printed circuit boards is drilling and plating residue. This can happen when holes are drilled into the board, but they are not cleaned thoroughly enough before plating. The result is that the hole becomes coated with a layer of metal particles, which can cause corrosion to occur if not removed during cleaning.
Improper PCB Surface Cleaning
Improper PCB surface cleaning is one of the most common culprits. Before soldering, copper surfaces must be cleaned thoroughly to remove any contaminants that could lead to an unwanted reaction between components during the soldering process.
If you’ve been using improper PCB surface cleaning techniques, your board may have come in contact with impurities from your cleaning agents or even other contaminants on your workbench—and this could cause a reaction during assembly that leads to corrosion or even failure.
Processes to Eliminate Ionic Contamination in your PCB
Eliminating ionic contamination from printed circuit boards is a necessary step to ensure the quality of your final product. Here are some ways you can do this.
Vapor Phase Degreaser
These are used to remove oils and greases from PCBs. The process involves the use of caustic chemicals that are vaporized at high temperatures. The resulting vapor is then passed over the PCBs, which causes the grease to be removed.
Vapor Phase Degreaser
Aqueous Cleaning
A process that uses water and chemicals to remove contaminants from your PCB. It’s a good option if you want to avoid using harsh chemicals or solvents. You can use it for both dry and wet etching processes, but it isn’t as effective at removing some types of contamination as other processes are.
Aqueous Cleaning
Semi-Aqueous Cleaning
This process is used to remove ionic contamination on the surface of a PCB. It is often used in conjunction with other processes, such as dry or wet cleaning, to ensure all possible contaminants are removed. This process involves immersing the PCB in a solution that removes chemical and physical contaminants from the copper traces and pads.
Semi-Aqueous Cleaning
Vacuum Cleaning
A process that uses a vacuum chamber to remove contaminants from a PCB surface. The process is done by placing the PCB inside the vacuum chamber, which is then sealed and evacuated. After this, the chamber is filled with an inert gas such as nitrogen or argon, which will prevent any further oxidation of the PCB surface and provide protection against external particles in the air.
Vacuum Cleaning
Benefits of Ionic Contamination Testing
Without ionic contamination testing, you could end up with a product that doesn’t work, or even worse, a fire hazard.
Here are some of the top benefits of ionic contamination testing in your PCB:
Avoid Product Breakdown by identifying Possible Cause
Ionic contamination testing can help ensure that your board will be free from harmful materials that could cause short circuits, electrical failures, and other issues that could lead to product breakdown.
Testing for contamination can also help you identify the source of the problem before it becomes a larger issue.
Avoid Product Degradation or Malfunction
Ionic contamination testing is a vital part of the PCB manufacturing process. It helps manufacturers avoid product degradation or malfunction by identifying electrostatic discharge (ESD), which can cause issues with the PCB’s performance.
Ionic contamination testing can help you detect ESD before it causes problems. Ionic contamination testing checks for ions that have accumulated in your PCBs during manufacturing or shipping processes. These ions can cause corrosion on your circuit boards and lead to corrosion underneath layers of paint. This will eventually result in discoloration and other problems with your device.
Detection of Ionic Contamination Source in the Process
The most significant benefit of ionic contamination testing is the ability to detect the source of contamination in your PCB process. Ionic contamination can be an expensive problem, but there are ways to stop it before it becomes a major issue.
One way to find out if you have ionic contamination in your PCB process is by using ionic contamination testing. This type of testing will allow you to determine where the ionic contamination is coming from.
Cleanliness Compliance Procedures
Cleanliness is the most important factor in ensuring that your PCBs are free from contaminants. It is important to test your PCBs to make sure they meet all cleanliness requirements. This ensures that you meet all industry standards and regulations.
IPC Standard for Ionic Contamination
The IPC has a standard for the ionic contamination of printed circuit boards (PCBs). It’s used to ensure that your PCBs are free from ions, which can cause short circuits and other problems.
The standard also specifies how to test your PCBs to make sure they’re safe for use. The test involves placing an ionic contamination meter on the board surface and measuring its conductivity over time. The minimum required conductivity level is based on the size of the board and its design:
– For unassembled boards: Length x Width x 2 = Unpopulated Board Surface Area
– For assembled boards: Length x Width x 2 + up to 50% = Assembled Board Surface Area
Conclusion
All in all, ionic contamination is something that can be prevented quite easily. The best way to prevent it is to develop new and sustainably sourced chemicals and materials. That knowledge of ionic contamination can help designers in the manufacturing process.