Ionic contamination is a significant problem for printed circuit boards and other precision conductivity products. This is what you should know about it, how you can find out if your products are affected by it, and what you can do if they are.
What is Ionic Contamination?
Ionic contamination happens when a sensitive conductive device such as a printed circuit board (PCB) is exposed to contaminants like salt, acids, sulfates, residuals from human handling, or flux activators during its fabrication or assembly.
These contaminants leave behind an ionic (positive or negatively-charged) residue on the surface of the conductive material. The ions in this residue can alter the conductivity of the material by changing its charge.
Why is Ionic Contamination a Problem?
Disrupting the charge on conductive materials like PCBs can affect their performance in a wide variety of harmful ways. It commonly rapidly hastens corrosion, which causes short circuits, inaccurate voltage readings and board damage.
Ionic solutions also facilitate the growth of dendrites, which are tiny conductive metal slivers that grow when electrolytic solutions are influenced by DC voltage bias. When dendrites come into contact with each other, they can also cause defects like short-circuiting.
Dendrites can even induce electrochemical migration, where currents flow through a conductive material differently than they were intended to. This can cause intermittent or total failures in PCBs, and can even be dangerous.
Ionic contamination accounts for 25% of all printed circuit board failures.
What is Ionic Contamination Testing?
Ionic contamination testing can identify the presence, concentration, and even composition of contaminants that create ionic solutions conductive material such as PCBs.
A wide variety of industries use the information from ionic contamination testing for product and manufacturing quality control. By testing their products, medical device companies and PCB manufacturers can narrow down where contaminants are getting into their products during assembly or manufacturing and fix the problem.
This testing is also commonly used for preventative or quality validation applications, such as to prove the efficacy of a cleaning agent or to define the basis for internal quality standards.
How Does Ionic Contamination Testing Work?
There are two common types of ionic contamination commonly used: the Resistivity of Solvent Extract, or ROSE test and Ion Chromatography (IC) testing.
The ROSE test
The ROSE test is the simpler, faster, and less in-depth form of testing. It determines the overall ionic content on the product, which allows us to make a comparable quantitative resolution of the contamination on the product itself.
How the ROSE test works
During ROSE testing, we extract the conductive sample using an isopropyl alcohol and deionized water solution. We subject this sample to extraction to measure resistivity change by running it through a dynamic ionic testing unit that uses a conductivity bridge and liquid conductivity cell to measure the sample’s resistance compared to a sodium chloride equivalent reference standard.
What to use the ROSE test for
The ROSE test determines total ionic contamination but it can’t actually identify the specific ions present.
This makes the ROSE test ideal for gauging the overall cleanliness of products after they’ve been manufactured for QA and Safety purposes or for establishing and monitoring internal quality standards, but it won’t let us identify specific contaminants or determine where those contaminants are coming from.
IC testing is the more in-depth form of testing between the two, and it can determine not only the amount of overall ionic contamination, but also the charge of the ions, specific ionic species present in the sample, and the concentration of each variety of ion.
How IC testing works
As with the ROSE test, during IC testing we extract a sample from the product using an isopropyl and deionized water solution. We run this sample through a high-performance liquid chromatography system that separates each ion by size, charge, and species.
The liquid chromatography system will have one of two charged columns: an anion column or a cation column. The samples enter the system as a mobile eluent solution, and as they move through the columns, they will either speed up or slow down based on their interactions with either column and therefore separate out.
Each of the different types of ions are moving at different speeds and are measured by an electrical conductivity detector as soon as they leave the column enclosure. This detector then produces a chromatogram which plots conductivity vs. time. By analyzing fluctuations in conductivity as the different ions leave the column enclosure, we can determine the type and concentration of ions that were removed from the sample.
What to use IC testing for
Unlike the ROSE test, we can use IC testing to identify specific contaminants and their concentrations.
Consequently, we can use IC testing to identify not only the contaminants themselves, but also, by understanding what the contaminants are we can determine how they may have been introduced to the sample during manufacturing or fabrication.
This gives our clients insights into where their products are vulnerable during their process in order to help them find and fix production issues that are affecting performance.
The experts at Innovatech specialize in IC testing, and can deliver accurate results in only five business days (faster times are available at premium rates). If you think you need IC testing, we’re ready to help now.