Chip Capacitors Information
Chip capacitors are passive integrated circuit (IC) components that store electrical energy. Chip capacitors are simply capacitors manufactured as integrated circuit (IC) devices, also known as chips or microchips. They are typically square or rectangular, with the length and width of the device determining its power rating. Chip capacitors typically do not have leads and mount directly onto a printed circuit board (PCB), and are therefore considered surface mount (SMT) products.
A circuit board with mounted SMD components. A chip capacitor is highlighted at top center. Image credit: ham-radio.com
The following images describe the manufacturing of multi-layer ceramic chip capacitors (MLCC).
Initial (left) and final stages of chip capacitor manufacturing. Image credit: Johnson Dielectrics
Rectangular surface mount components, such as chip capacitors, are sometimes referred to by standard metric or imperial codes. These codes are listed below, first in imperial size with metric code in parentheses, then nominal metric dimensions. Note the direct correlation between the metric code and nominal size.
- 01005 (0402): 0.4 x 0.2 mm
- 0201 (0603): 0.6 x 0.3 mm
- 0402 (1005): 1 x 0.5 mm
- 0603 (1608): 1.6 x 0.8 mm
- 0805 (2012): 2 x 1.25 mm
- 1008 (2520): 2.5 x 2 mm
- 1206 (3216): 3.2 x 1.6 mm
- 1210 (3225): 3.2 x 2.5 mm
- 1806 (4516): 4.5 x 1.6 mm
- 1812 (4532): 4.5 x 3.2 mm
- 2010 (5025): 5 x 2.5 mm
- 2512 (6432): 6.4 x 3.2 mm
- 2920: 7.4 x 5.1 mm
Tantalum chip capacitor dimensions are specifically standardized by the Electronic Industries Alliance (EIA) and are based in part on metric codes, with an added code for maximum device height. For example, the nominal dimensions of an EIA 2012-12 capacitor are 2 mm x 1.2 mm x 1.2 mm (length x width x height).
Chip capacitors, like many other small electronic components, may be packed in tape reels, trays, or shipping tubes. All three methods provide compatibility with standard pick-and-place machines and other assembly equipment.
Tape reels consist of carrier tape with embossed cavities for individual components. After components are mounted on the tape, a cover tape seals the devices and the carrier tape is wound onto a reel. Tape and reel assemblies provide the advantage of component isolation. Tape is well-suited to SMT components.
Trays (or rails) are molded into rectangular outlines containing uniformly-spaced pockets for storing components. Trays are typically used to pack and ship components with leads, and are stacked and bound together to facilitate shipping and handling.
Shipping tubes are rigid PVC containers which protect components during shipping and provide proper component orientation and positioning.
A capacitor's attributes, as well as capacitance, are heavily influenced by the dielectric (insulating) material between the device's plates. Typical dielectric materials can be classified into three general groups: film, electrostatic, and electrolytic.
Capacitor applications by type. Image credit: Elcap
Film capacitors feature thin plastic film as a dielectric, and may be metallized, meaning that metal electrodes are previously vapor-deposited on the film. Common film capacitor materials include polyester, polypropylene, and polystyrene. Film capacitors are excellent general- purpose devices with high dielectric strengths, low moisture absorption, and high insulation resistance. Capacitors with single-layer dielectrics have slightly poorer temperature stability and resistance, while multi-layer dielectrics enable smaller device sizes and improved temperature stability.
Cross-section of a typical film capacitor. Image credit: Elcap
Electrostatic capacitors feature dielectric materials that naturally support an electrostatic field — which is crucial to the device's energy-storing function — and do not conduct electrical current. These devices may use a number of different dielectric materials, which are listed below along with their attributes or typical applications.
- Air - high voltage applications.
- Ceramic - excellent for use in timing applications. Depending on the specific ceramic material, may exhibit relatively high capacitance deviation over a wide temperature range.
- Glass - high voltage applications. Very stable, reliable, and resistant to radiation.
- Mica - highly stable, good temperature coefficient, excellent endurance and reliability.
- Oil - suitable for DC applications. Oil dielectrics often require maintenance and may need to be larger than other devices to suit their intended use.
- Electrolytic capacitors feature one plate comprised of a liquid electrolyte to achieve greater capacitance using a small package. Some electrolytic capacitors may be capable of several farads of capacitance.
Chip capacitors may be subject to different standards, many of which are developed and published by the Electronic Industries Alliance (EIA). Common chip capacitor standards include:
- EIA CB 11 - Surface mounting of MLCC
- EIA IS 36 - Multilayer Ceramic Chip Capacitors
- EIA/ECA-956 - Aluminum Electrolytic Chip Capacitors