Chip capacitors are small, rectangular devices used in high-frequency electronic circuits. They consist of multiple layers of ceramic powder and conductive metallic ink, which are stacked, pressed, cut, and cooked before terminals are applied and electroplating takes place. The finished devices are tested, packaged, and sold in coils of thousands for less than $1 per 100 capacitors.
Capacitors are electronic charge storage and signal filtering devices that block direct current but allow alternating current to pass within their design parameters. Each capacitor includes two conductors with a polarizable insulating dielectric layer sandwiched between them. A chip capacitor is generally a rectangular device that is the capacitor of choice for high-frequency electronic circuits. Its size is typically less than a quarter of an inch (6.35 mm), and it operates at a power of a fraction of a watt. A chip capacitor is often sold not individually, but in coils, often in the thousands, and can cost less than US$1 per 100 capacitors.
A chip capacitor consists of multiple layers, which is why it is often called a multilayer ceramic chip capacitor (MLCC). The ceramic powder must be formed into sheets of a specific thickness. This means that the powder must be combined with carefully controlled amounts of binders and solvents. After it is mixed, the slurry is poured, then baked on conveyor belts. The ceramic sheets are not yet cut to size; conductor application and layering must occur first.
Conductive metallic ink is made of powdered metal, ceramics and solvents, using a crushing, mixing and finishing device called a three-roller mill. The ink or paste is then screen-printed through special pattern “screenprints” and dried with hot air. At this point, the structure can be compared to green pottery. The sheets are then stacked in the correct way and number. After applying pressure to join these layers into a single structure, it is cut into individual pieces.
Next, the pieces must be cooked. The heart of this process is a furnace with a very slow moving conveyor belt which transports the pieces through a tunnel with a very carefully profiled heating cycle and, if necessary, a controlled atmosphere. This step plays an important role in the characteristics of the finished devices. At this point the terminals must be applied to the two ends of the devices, using powdered metal and glass, with solvent. These are sufficiently licensed.
Electroplating is the final process that proceeds to testing. The plating takes place in layers, the first of which is a nickel barrier layer, to protect the underlying device. Subsequently, a layer of tinplate prevents corrosion of the nickel and, in end use, improves solder compatibility, if devices are to be soldered. After completing all these steps, the devices are tested. Quality control values and tolerances are carefully established and recorded, then the capacitors are packaged and sold.
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