source: Kemet article
Monday, October 26th, 2015
Before starting with KEMET, I had limited experience with Tantalum-based capacitors. Like many young engineers, I was taught to avoid them, but never really told why. As I learned more about tantalum capacitors, I found there was, and still is, much misinformation and many misconceptions about these capacitors.
Don’t let these 5 Tantalum Capacitor Myths hold you back from using them in your design.
Tantalum Capacitor Myth #1:
World Demand for Tantalum Exceeds available supply
This myth got a little bit of life back around 2000 because of a shortage of tantalum ore leading to a shortage of tantalum capacitors. At the time, there was only a single mine sourcing the ore. The cost to mine the ore because prohibitive, so the mining operation shut down tantalum mining.
The situation that occurred back in 2000 was an isolated incident because, since that time, multiple mines have opened in Brazil, Canada, China, and Africa. Some of these mines are the same “Hard Rock Mine” type from 2000. Others, like the primary source KEMET, uses today are considered “Artisanal” mines. These open pit mines are far less expensive to operate.
With multiple regions contributing a mixture of ore production costs, the price for ore remains competitive. Capacitor manufacturers, like KEMET, have established a conflict-free and and broader supply chain to prevent constraints on supply.
Tantalum Capacitor Myth #2:
The world is running out of Tantalum
The “world is running out” myth is related to the first one. Rumors have circulated saying that the total available ore is running low. Again, this was in part because when the capacitor shortage in 2000 occurred when only one mine was operating.
Today, rich veins of ore have been discovered throughout the world. The US Geological Survey Fact Sheet 2014-3054 published in June of 2014 estimates enough supply for the next 500 years.
In other words, no anticipated shortage in my lifetime, your lifetime, or your product’s life cycle!
Tantalum Capacitor Myth #3:
The only use of tantalum is capacitors
For most electrical engineers, the only time you hear about tantalum is in regards to capacitors. So this leads many of us to believe that is the only reason for mining the ore.
Tantalum has high biocompatibility, making it suitable for medical implants. However, mechanically it is not very strong, compared to other metals. For some medical applications, the stronger stainless steel will be coated with tantalum, providing high strength and biocompatibility. Examples of its usage are stints, bone replacements, suture clips, and wire.
The metal is relatively very inert, and that makes it useful to line pipes, tanks, and vessels in harsh environments or transporting corrosive materials.
Usage outside the electronics industry is critical because it keeps demand high. Again, from the USGS June-2014 report, capacitors only account for about half of the world’s tantalum production.
Tantalum Capacitor Myth #4:
No Safe Fail Mode for Tantalum Capacitors
It is true, most engineers have a story related to a tantalum capacitor “failing.” Sometimes with what we call “ignition mode.” (Of course, these stories can also apply to ceramic or aluminum capacitors, as well as other components too!)
What many engineers call “tantalum” or “solid tantalum” capacitors are an older technology. Like all capacitors, there are two electrodes separated by a dielectric. The anode plate is tantalum, the dielectric layer is Tantalum Pentoxide (Tao), and the Cathode plate is Manganese Dioxide (MnO)
Inside of a T495 – Tantalum MnO Capacitor
As it turns out, when the dielectric layer has a fault, allowing too much current to flow, each heat can be generated in the MnO layer allowing the MnO to ignite.
It is important to note that the MnO layer is the ignition layer and not the tantalum or its oxide. One way to achieve safe tantalum capacitors is to use an alternative cathode material.
Tantalum Capacitor Alternative Technology
There are two other cathode technologies used for Tantalum-based capacitors. A “wet” style with a wet electrolyte and a newer solid “polymer” cathode.
Tantalum capacitors made with polymer cathodes, also known as “polymers” or “polymer electrolytic,” do not ignite on failure. In fact, we’ve found them to be significantly more reliable when compared to their traditional MnO counterparts–meaning fewer failures.
We name our Polymer Tantalum “KO-CAP®” and they feature a polymer cathode with a benign (or safe) failure mode.
Tantalum Capacitor Myth #5:
Few applications use Tantalum Capacitors
Maybe it is just the name, but it seems pretty common to think that tantalum capacitors are only for high-end exotic applications.
The average person carries from as few as 10 and up to 50 tantalum capacitors every day. You only need to look at a laptop computer, tablet, or smartphone to find examples.
Beyond computing, we have customers in every major electronics segment using tantalum capacitors. Automotive manufacturers use them in infotainment systems, ADAS, tire pressure monitors, and in under-the-hood ECU. We have an example of an aerospace customer who found polymer / KO-CAP reliability plus volumetric efficiency to be a big advantage to their program. We also come across FPGA reference designs with KO-CAPs surrounding the FPGA for decoupling.
Historical misconceptions and myths have given tantalum and tantalum capacitors a bad rap. With these myths dispelled hopefully you can now start to use tantalum in your designs and take advantage of all the technological advantages of tantalum.
If you still have concerns or questions about using tantalum capacitors in your design, use the Contact Form below to get in touch with one of our Field Application Engineers. They can help you determine if there is an alternative or help you understand if there is any risk with your design.