What are Tantalum Capacitors and is it Worth Scrapping Them?

Background

As we all know, a capacitor is a device used to store electrical energy in an electric field. Capacitors are commonly made from two metal plates separated by a dielectric material. When an electric current is applied, the capacitor will store energy in the electric field between the plates.

Capacitors can be made from a variety of metals but tantalum has had a significant impact in this field for many years now. So much so, it is a bedrock of modern electronics – and consequently e-waste

What is Tantalum?

Tantalum is a chemical element with the symbol Ta and atomic number 73. It is a rare, silvery-white, hard, corrosion-resistant metal. The metal occurs in several oxidation states, including +5 and +4, but the most common is +3. Tantalum is not found free in nature, but it is often obtained as a by-product of the production of other metals such as niobium.

Tantalum is typically found in a number of different minerals, including columbite, tantalite, and microlite. These minerals are often located in areas that have experienced significant geological activity, such as hot springs or volcanoes. Tantalum is also occasionally found in alluvial deposits, where it has been deposited by running water. The largest producer of tantalum is Australia, followed by Brazil and Canada.

So What is a Tantalum Capacitor?

Well, for starters tantalum is a great precious metal for storing energy. Compressed powder of the silver-grey tantalum beads can store a significant amount of charge compared to the material’s overall mass. In addition Tantalum is often used in electronic components because it does not corrode in the presence of other elements.

Tantalum capacitors are sometimes classified as MLCCs. They offer high capacitance values in a very small package, making them ideal for use in a variety of electronic applications. They are also regarded as electrolytic; this means they are polarized.

This means that we can safely shrink these components further than traditional capacitors. For instance mobile phones can be made even more compact by using these smaller capacitors.

History of the Tantalum Capacitor

Tantalum electrolytic capacitors were first developed for military use in the 1930s. Electrolyte and wound tantalum foils were used in these devices. Bell Laboratories developed the first solid electrolyte tantalum capacitors in the 1950s. Tadpoles were formed from the ground-up tantalum. Manganese dioxide was first used as a solid electrolyte, but it was later discovered that it could also be used as a liquid electrode.

Advantages

Some advantages of tantalum capacitors include their high capacitance values, their ability to operate at high frequencies, and their small size. In addition, because tantalum capacitors are non-polarized, they are not affected by the polarity of the voltage applied to them. This makes them ideal for use in circuits where the voltage polarity is unknown or changing. Finally, tantalum capacitors have a long life span and are able to withstand high temperatures without failure.

Disadvantages

Some disadvantages of tantalum capacitors include their high price tag, tendency to fail catastrophically when overloaded, and relatively low capacitance compared to other types of capacitors. Additionally, they are not widely available, so they can be difficult to find in some parts of the world.

How are Tantalum Capacitors Made?

The best description of their construction can be found at eepower.com

Tantalum electrolytic capacitors, just like other electrolytic capacitors, are consisted of an anode, some electrolyte and a cathode. The anode is isolated from the cathode so only a very small leakage DC current may flow through the capacitor. The anode is made of pure tantalum metal. The metal is ground into a fine powder, and sintered into a pellet at high temperatures. This forms a very porous anode with a high surface area. A high surface area directly translates to an increased capacitance value.

The anode is then covered with a layer of insulating oxide, which acts as a dielectric. This process is called anodization. This step must be precisely controlled to reduce tolerances and ensure correct capacitance values as the extent of oxide growth determines the dielectric thickness.

Electrolyte is added to the anode by means of pyrolysis in the case of solid tantalum capacitors. Solid tantalum capacitors are then dipped into a special solution and baked in an oven to produce a manganese dioxide coat. The process is repeated until a thick coating is present on all internal and external surfaces of the pellet. Finally, the pellet used in solid tantalum capacitors is dipped into graphite and silver to provide a good cathode connection. In contrast to solid tantalum capacitors, wet tantalum capacitors use a liquid electrolyte. After the anode is sintered and dielectric layer is grown, it is dipped into a liquid electrolyte within an enclosure. The enclosure and electrolyte together serve as the cathode in wet tantalum capacitors.

https://eepower.com/capacitor-guide/types/tantalum-capacitor/

Where Else is Tantalum Found?

• Heat exchangers
• Bayonet heaters
• Thermometer wells
• Vacuum tube filaments
• Chemical process equipment
• High temperature furnaces components
• Crucibles for handling molten metal and alloys
• Cutting tools
• Aerospace engine components
• inerts Surgical implants
• Alloy additive in superalloys

The Tantalum Shortage

In 2020 a tantalum capacitor shortage occurred and is ongoing. Global demand is on the rise and inventory is diminishing quickly; therefore, price increases and long lead times will be inevitable. That might mean your greedily hoarded capacity stock might be more valuable that you know.

Is it Worth Scrapping for Tantalum?

For the hobbyist there is little value in trying to refine and process tantalum capacitors at home. See this video for a demonstration https://www.youtube.com/watch?v=zCs1CQSwu-Y. You may be better off just farming your PCBs for capacitors and selling them on eBay to a gullible person.

Consider this: tantalum capacitor weights in laptop printed circuit are around 8 g in laptop printed circuit boards whereas this rate is 3 g in hard disc drives. Tantalum is priced anywhere from $250 to $300 per kg. So that 8g is worth about $2. Likely you have used up some of that on fuel, chemicals, even the petrol cost of getting the original materials. It had probably taken you several hours to refine. So you are well under minimum wage. You’ll probably get more for the board at Boardsort.com!!!!

And even if you do recover your tantalum. Who are you going to sell it you? Pretty sure your local scrap yard or refiner won’t be interested.