Guidelines for Interpreting Ionic Contamination Testing

PCBs are huge assets for the fine performance and longevity of consumer electronics and futuristic smart devices. However, things can go south with PCBs due to ionic contamination.

 The contamination of PCBs normally occurs due to faulty fabrication and external factors. Now, these external factors can be anything. From flux remains to extreme weather exposure, such factors create a negative impact on PCBs. 

Nevertheless, there are some viable solutions to save PCBs from all such threats. It includes ionic testing of PCBs. The purpose is to detect the contamination first before coating the PCBs. There are many benefits of this checking method. We will learn about the ionic testing of PCBs in detail. 

WHAT IS THE Ionic Contamination Testing?

Ionic contamination means that the fragments of the flux are still remaining on the PCB surface. It normally occurs when you are assembling the PCBs. However, it has consequences as well.

 There are unbreakable electrostatic bonds between ions. These bonds can either be positive or negative. A fine example is Sodium Chloride, aka table salt. The sodium ions are positive, while chloride ions are negative. 

The PCB parts have their own ionic residues that can damage the PCB later. These can be:

• Corrosion-resistive substances
• Oils and liquids
• Biocidal entities

Not only this, but some non-ionic factors are also not healthy for the longevity of PCBs. These are oils used for the assembly process and molds. You cannot predict the contamination of PCBs at all. It can occur at any place and can lead to extreme damage. 

Ionic Contamination Testing for Cleanliness Prevents Issues 

As you know, flux has great importance in PCB assembling and its performance. You can rely on different types of flux for this purpose. These different types of flux are also beneficial for soldering. However, with each flux type comes contaminants as well. 

Some of the common flux used in the process of soldering are:

1. Resin (Rosin) Flux: It includes abrasive and non-abrasive fragments
2. Organic Flux: It produces removable residues that can be corrosive, and some can be less abrasive
3. Inorganic flux: Leaves extremely corrosive residues

Procedure of Ionic Contamination Testing – Plasma

Ionic contaminants can cause huge damage if not treated properly. These can also retard the fine performance of PCBs. Due to this reason, contamination checks are important to ensure everything is in place from time to time.

 You can use some special tools like a contain meter and omega meter for this checking method. These tools are helpful in detecting ionic cleanliness. You just need to add some ions into a special liquid that will give the precise amount of ions present based on the criteria of ions of NaCl. 

Advantages of PCB Ionic Contamination Testing

Now, you know why performing such checks is important to enhance the performance of PCBs. However, in the past days, manufacturers would use conformal coatings for the same purpose.

 Although they had high hopes for these coatings, they did not remove the contaminants completely. The purpose is to leave not a single fragment on the PCB surface. 

If you leave any residue unknowingly, it will lead to irreversible contamination. It will also invade new coatings afterward. Now this verification method also helps you remove the non-ionic fragments. Some major benefits of this process include:

• It completely excludes the invasive ionic fragments produced due to the soldering of PCBs
• Besides, it also comes in handy for boosting the ionic cleanliness of PCBs before you bring them into contact with any sort of coating.
• It removes the non-ionic invasive entities from the surfaces, ensuring 100% ionic cleanliness of PCBs 
• Besides, It is an affordable method and delivers positive results.
• It is not time-consuming as it just takes 24 hours for the completion.

Ionic Contamination Testing In Different Industries

The ionic contamination test is an important verification method for different domains. It is crucial for thorough testing of PCBs so that they can perform efficiently under extreme conditions. 

Also, it protects the PCB parts from undergoing future damage. Not only this, but this testing also ensures that the data stored in your setup is safe on all counts. The fields that never compromise ionic contamination testing are: 

• Solar energy sector
• Aerospace 
• Defense and military
• Computing industry
• Medical/healthcare sector

Problems arise due to Ionic Residues 

Below are the issues that arise if you do not ensure 100% ionic cleanliness throughout your PCBs:

1. Corrosion: Corrosion mostly invades the metallic PCB parts when there are ionic entities still present on the surface. Ionic contamination can lead to corrosion in just a short period of time. 

In order to make sure the PCB parts do not undergo corrosion, this test is inevitable. Also, moisture can lead to short circuits and electrical faults when it interacts with ions. The metallic surface slowly starts to crumble and hampers the performance of PCBs.

• Dendritic growth: It means an unusual build-up of metals starts to grow on the PCB surfaces. Dendritic growth is due to an electrolytic substance formed due to DC voltage bias. 

Metallic dendrites result from the left-out holes of a solder cover. Now, this solder cover would contain flux residues and other ions. If these dendrites combine with each other, it will lead to electrical failure, electrical fire, and other issues like short circuits. 

• Electrochemical migration: Electrochemical migration normally occurs due to the dendrites that form on a dielectric substance. These can contain conductive ions. Now these ions can re-route the current from its passage. Electrochemical migration is a major threat to the life length of PCBs. 

Ionic Contamination Testing And Cleanliness Measurements

There are some important measures for ensuring complete ionic cleanliness other than ionic contamination testing. These are equally important to boost the longevity of PCBs. We are going to discuss these in this section for better understanding!

1.  Resistivity testing: There is a special resistivity testing tool that is important for ensuring the cleaning of PCBs. However, it does not mean that it will provide desired results since the cleanliness of PCBs should meet the IPC criteria. 
2. ROSE test: ROSE testing is to identify the invasive ions that can cause problems to PCBs. It is beneficial because the ROSE test sketches the ions that are present. Now, it is much easier to detect these ions due to clear visualization. 
3. Modified ROSE test: The modified ROSE test is helpful because you can use it for thermal extraction as well. It just exposes the solvent to extreme temperatures. An ionograph gear is reliable for performing this test. 
4. Ion chromatography test: An ion chromatography test is also helpful for excluding all the ionic content completely. The test includes passing the solvent from ion chromatographs which makes this test highly important among the others. When you get the results, it will show what ions are still active in the solvent under observation.

Effects of Ionic Contamination and Testing in a PCB

By far, you are well aware of the adverse damage caused by ionic contamination. The PCBs can undergo extreme damage due to this type of serious threat. Before the production process starts, the raw boards might have flux remains, traces of etching chemicals, and solder fragments. 

There is no margin to leave these substances on the boards due to the worst consequences. 

• Electrochemical migration (ECM): Electrochemical migration happens when the entire metal disappears due to the electric field. It gives rise to ions between two metallic electrodes. Not only this, but it also initiates dendritic growth when ions interact with electrodes. These dendrites occur due to conductive ions. It is the main reason for adverse damage to PCBs and electrical glitches. 

Ionic contamination is not the only culprit here. There are some other factors that have the potential to damage PCBs as well. These are environmental conditions and exposure to extreme temperatures. 

It is recommendable to first bake the PCBs to remove all the moisture. You can even use a controlling tool to prevent ionic contamination. It is beneficial to make sure that all the steps of PCB production are accurate. 

Choosing RayPCB For Ionic Contamination Testing

RayPCB experts believe it to be highly tolerant of ionic contamination. Since ionic contamination is a budget-friendly and affordable test, plasma just adds up to its significance for major PCB producers. The ROSE test is also beneficial for the ionic cleanliness of your PCBs. Such tests for ionic contamination are not a threat to the environment as well. 

Also, you can take help from this test to see what type of cleaning technique fits well with the PCB you are assembling. There are some important things to remember after completing the test. 

We make sure to re-detect the PCB parts for ionic content. Our purpose is to provide you with industry-grade expertise so that your PCBs can serve you well in the long run without any hustle.