Capacitors are among the basic building blocks of electronic circuits. Learn what these electronic components do, how they’re used, and their types and key specifications.
What Capacitors Do
Capacitors are electronic components that store and release electrical energy. They’re used to smooth out voltage fluctuations, filter out noise, and supply sudden bursts of power.
How Capacitors Are Made
There are many types of capacitors, but most have two electrical conductors separated by an electrical insulator. The conductors are known as plates and are made of very thin aluminum foil. The electrical insulator, or dielectric, varies by capacitor type and directly affects performance.
Film Capacitors for High‑Voltage Applications
A film capacitor contains a plastic film such as polyester or polypropylene. These capacitors are widely used in high‑voltage or pulse applications because the dielectric film is stable, durable, and resistant to heat.
Aluminum Electrolytic Capacitors for Power Supplies
There are also aluminum electrolytic capacitors that contain a thin layer of aluminum oxide, an excellent electrical insulator. These components are commonly used in power supplies to smooth DC voltages.
High heat causes aluminum electrolytic capacitors to wear out more quickly, and there’s a rule of thumb that for every extra 10 degrees Celsius, a capacitor wears out twice as fast.
Aluminum electrolytic capacitors combine long life with high capacitance, but high heat can dry out the glycol‑water mixture that their paper dielectric is soaked in.
Multi‑Layer Ceramic Capacitors (MLCCs): High‑Density Energy Storage
Ceramic capacitors with a multi‑layer construction are especially popular today. Stacking many thin ceramic layers together maximizes surface area and supports high‑capacity energy storage for compact electronics.
Why Dielectric Thickness Matters: Capacitance and Performance
The thinness of the dielectric is important because it’s related to capacitance, which measures the ability to store an electrical charge. By cutting the dielectric’s thickness in half, the capacitance is effectively doubled.
Voltage Ratings and Dielectric Breakdown
In addition to capacitance, maximum voltage is a key specification. Applying excessive voltage causes the dielectric material to break down and can result in an arc.
Capacitor Manufacturing
During capacitor manufacturing, multi‑layer ceramic capacitors (MLCCs) are built by stacking layers into a block‑like structure. By contrast, the layers in aluminum electrolytic capacitors are wound into a roll.
Rolling the layers increases the surface area, but so does the chemical etching process that creates nooks and crannies in the dielectric—similar to the texture of an English muffin.
Film capacitors are typically wound up like a jelly roll. The plates can be made from aluminum foil or produced like a Mylar balloon, where thin plastic is coated with metal. In this process, the plastic film passes through a vacuum chamber where the metal is sputtered onto its surface.
Why Capacitors Matter
Capacitors come in a wide range of shapes, sizes, and capacitances, but they’re a basic building block of electronic circuits today. If you’re planning an electronic design or need to manufacture a product that uses these electronic components, contact Z-AXIS.