Electrical and electronic supply chains are impacted by the effects of transient electrical anomalies that occur from anticipated events such as lightning or electrostatic discharge through touch.

Lightning is the most damaging because of the millions of volts dispelled, and the ability for the lightning to couple to power and telecommunication lines and dissipate energy into multiple consumer electronics products at once. For decades the solution to limiting the effects of the lightning on consumer electronics worldwide has been the use of redundant levels of protection that begin at the power transmission station or central office and work their way to strategic points of protection at service entrances and outlets throughout the supply chain.

ESD through touch is a high volume event, the damages of which have been effectively reduced through the use of ESD suppression components and technology over time.

Lightning is the most fascinating of the events to study and the most difficult to protect against, while electro-static discharge (ESD) is also intense (and visible to the consumer), the real culprit is line switching by power companies that have the greatest degrading effect on consumer electronics over time.

Furthermore, and with great historical sense, I also need to note that because there is a direct impact on the consumer, where the effects of transients can be seen and felt, it has been one of the most highly-regulated industries, with a large and diverse number of government agencies and industry-specific standards developed over time to address what design engineers within narrow segments of the high tech economy need to protect against. This also changes by world region, but always involves testing the voltage exposure over various amounts of preset time.

Multiple Component Solutions Available:

Because of the varying needs of individual industries to protect against lightning, ESD and other electrical transients, the resulting number of components is large and diverse and also differs from region to region around the globe. Thus the point of sale comes in helping the design engineer plan for and comply with industry and government specifications regarding circuit protection. This requires a combination of knowledge of standards and regulations in multiple industries that impact multiple end-use product segments. Furthermore, from a marketing standpoint, we note that every segment of electronics requires its unique form of circuit protection solution. This includes all consumer electronics, and also industrial platforms in telecom, automation, cars and trucks, railroad, boating, mining, defense, laboratory, campus and many more fragmented environments. This absolutely creates a market environment best served by distribution, and moreover, these vendors are all tapping into the following component technologies to create the core protection component platforms.

Overvoltage Protection Components:

Either silicon, mixed metal, gas, thick-film cermet or polymer technologies achieve overvoltage protection in electronic components. Overvoltage protection components that employ manipulated silicon as the core technology include zener diodes, silicon avalanche diodes (otherwise known as TVS diodes) and thyristors. Mixed metal technology is zinc-oxide based technology employed in metal oxide varistors. Similar technology is also employed in NTC thermistors, although different raw materials are used. Various gases are the active material employed in gas discharge tubes; while thick-films composed of palladium and silver on alumina substrates are also used for overvoltage protection. Polymer technology is employed in snubber capacitors and employs metallized polypropylene and polyester materials. Polymers are also the basis for new developments in overvoltage protection and find their roots in PTC thermistor developments for overcurrent protection.

Overcurrent Protection Components:

Overcurrent protection devices represent a larger dollar value market, but a lower unit volume market when compared to overvoltage protection components. The core technology associated with overcurrent protection is similar to overvoltage, and is based upon fusible metal elements; ceramic, mixed metal oxide and polymer technology. Overcurrent protection devices include traditional electronic fuses, which have fusible metal elements in either glass or ceramic, PTC thermistors, which may be titanate based or polymer based and NTC thermistors, which are mixed metal oxide based. Overcurrent protection markets are growing at a slower rate when compared to overvoltage protection component markets because the end markets into which overcurrent protection devices, such as large and small home appliances (white goods) are sold are growing at a slower rate when compared to the end-use markets where overvoltage protection components are sold.

Fusible Element Technology:

Electronic fuses available in axial, radial, and surface mount designs employ technology based upon glass or ceramic housings that contain a metallic fusible element. Fuses are employed exclusively for overcurrent protection of sensitive electronic devices, and the concept of using twisted pair elements to create a fuse still represent the largest circuit protection component market based upon revenues (because of its use in residential lighting and power and automotive fuse box applications).

Twisted Pair Element Fuses: These types of fuses are manufactured by using wires made up of two elements of unlike materials that are twisted together to become a compound element. The two types of wires, which are contained in a glass cartridge, have different temperature coefficients and melting points. Twisted pair element fuses are used in medium time delay fuse designs because they respond more slowly to an overload event when compared to single element fuses.

Solid Matrix Fuses: These fuse designs are somewhat new to the marketplace in comparison to the twisted pair fuse design. These designs offer greater levels of reliability in harsh environments when compared to twisted pair fuse designs. In these designs, the fusible link is enclosed in a ceramic filler material and is placed in the fuse package. These designs are used in surface mount applications.

Blade Fuses: These types of fuses are built for the automotive industry as molded plug-in devices. They operate in a similar method as their Twisted Pair Element Fuse counterparts but have a construction that is specified for the automotive industry.

Silicon Technology

There are three core products produced for applications in electronic circuit protection that employ silicon as the core technology. These include the zener diodes, the silicon avalanche diodes, and the thyristor.

Zener diodes are the least expensive circuit protection solution on the market. These devices represent the largest volume of units sold for electronic circuit protection throughout the world, and they are used in large volumes in a variety of consumer audio and video related products. None of the literature that surrounds zener diodes suggests that they will by themselves help a manufacturer of electronic devices and subassemblies comply with industry regulations and specifications, but they are used for circuit protection however, predominantly in pairs or in series, for just that application.

Silicon Avalanche Diodes, or more advanced silicon components, are employed primarily for electrostatic discharge protection to help original equipment manufacturers comply with IEC 61000 4-2 specifications; where they compete primarily against multilayered varistors.

Thyristors are the most advanced circuit protection device produced from silicon. These devices are extremely difficult to build, and they are used primarily to help telecommunications infrastructure equipment companies comply with the GR-1089 CORE specification.

Silicon solutions for overvoltage protection represent the second largest market for electronic circuit protection components in terms of value (fuses are slightly larger in revenues), because they have successfully made inroads in both telecommunications and portable consumer electronics environments.

Metal Oxide Technology

Electronic circuit protection devices constructed with mixed metal oxide technology include metal oxide varistors for overvoltage protection and NTC thermistors for overcurrent protection technology. Varistors, which come in both multilayered surface mount and leaded disc formats, are based primarily upon zinc-oxide technology. Multilayered varistors which employ either 100% platinum or a mixture of palladium and silver in their electrode structure are used primarily for ESD protection to help companies comply with IEC 61000 4-2 specifications; while the disc version of the varistor has considerably greater surge handling capabilities when compared to their multilayered counterpart and are used to help companies comply with the more demanding portions of the IEC 61000 specification. Multilayered varistors are used primarily in wireless communications devices and in automotive electronic subassemblies. Disc varistors are used in lighting ballasts and surge protector and suppresser modules.

NTC thermistors also employ a mixed metal oxide technology based polycrystalline semiconductor materials, or a combination of chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni). NTC thermistors are used in a variety of applications, including; automotive electronics, home appliances, battery chargers, medical electronics and general industrial electronics equipment as temperature sensing and compensation devices.

Titanate Ceramics

Titanate materials, which are employed primarily for applications in ceramic capacitors, are also employed for applications in ceramic PTC thermistors. PTC thermistors are used in a variety of applications which include subscriber line interface cards, automotive and other single phase motors, thermal print heads, power supply, CRT degaussing and lighting ballasts.

Polymer Protection

Polymers are employed primarily for PTC thermistor applications where they compete against titanate ceramics, primarily for applications in telecommunications equipment. The polymer PTC thermistor is typified by the Tyco/Raychem Polyswitch, which is, according to the relative patents, based upon the concept of polymer thermal expansion. Polymers are also the latest in overvoltage protection components, where they now are being applied to compete against multilayered varistors and silicon avalanche diodes for ESD protection. The historical development of overvoltage protection polymers can be traced directly to the development of the polymer PTC thermistor technology from Raychem.

Gas/Ceramic

Gas discharge tubes (GDTs) are used in both telecom and power line applications as primary protection devices, wherein the gas tube component is the integral part of a larger plug-in module protector for central office applications or station class protector for residential and business service entrance applications, but are losing ground to solid state thyristor technology, especially in central office protection applications in North America (GDTs are still quite popular in Europe and Asia).

Thick-film Cermets

Thick-film metallization composed of palladium + silver is the circuit protection material applied to alumina substrates for use in line-feed resistors (sometimes referred to as surge resistor networks). Line-feed resistors are generally applied to subscriber line interface cards for telecom and datacom switch applications, where they act as secondary line protectors for the sensitive network cards that they are designed to protect. Line-feed resistors are designed to help equipment manufacturers comply with the Telcordia (GR-1089 CORE) specifications.

Plastic Film

Power film capacitors constructed from metallized polypropylene or polyester film are also used for overvoltage protection in the form of snubber capacitors. Applications for metallized film capacitors used as snubber capacitors are primarily for protection of power semiconductors, such as IGBTs and GTOs, which are used primarily in variable speed drives for power conversion equipment, conveyor belt systems, locomotive engines, windmills and other related industrial devices.