Moving from leaded to chip resistors

A resistor is a device that opposes the current in a DC (direct current) circuit. This opposition is called resistance and is measured in ohms. Resistors are either fixed with a designated ohm value or are variable, with a designated range of ohm value. Variable resistors that control voltage, or rheostats that directly control resistance, are popularly known as potentiometers. These are further categorised as current sensing, electric heating, high voltage, high current, heating, inductive, non-inductive, light dependant, shunt, etc.

By Sandhya Malhotra

Monday, September 05, 2011: Resistors are manufactured using various technologies and are broadly available as carbon film resistors (CFR), metal film resistors (MFR), wire wound resistors (WWR), power resistors, metal oxide resistors (MOR), high voltage resistors, metal glaze resistors, fusible resistors, hybrid resistors, voltage dividers, resistors for lightning and motor run applications, resistors for HT & LT capacitor discharge applications, etc. But the most popular and widely used are CFR and WWR.

The basic function of resistors in a circuit is to control the current. They are used in all electronic gadgets, from the most complicated space equipment to the common man’s most used mobile phones. Resistors are also used in all kinds of power supplies, and automotive and locomotive applications. The growing number of electronics manufacturing service provider companies in India, assembling electronic circuits for major MNCs, is another emerging segment for resistor manufacturers to tap.

Demand for resistors

Pankaj N Kinariwala, managing partner, Pavan Industries, says, “Resistors are a basic electronic component; no electronic circuit can be thought of without a resistor associated with it (directly or indirectly). As a result, the market is ever growing. Resistors can be considered to account for within 1 per cent of the total cost of electronic equipment.”

Commenting on the challenges of the resistor market in India, Sujata Soparkar, CEO, Intron Electronics, says, “The resistors market is mature, with very well established players in different segments. Each manufacturer has its own client base, which is not usually encroached upon by others. Because resistors are under the zero duty regime, competition between imported and Indian manufacturers is very fierce. This has resulted in eating into the profit margins. It has also led to many manufacturers becoming mere traders.”

PN Khadilkar, director, Cermet Resistronics Pvt Ltd, says, “The resistor market for lower wattage (below 2W) is badly affected due to global players from China, Taiwan, Malaysia and Thailand. However, pricing for special products is still good due to various manual operations and custom built designs.”

Resistors, either fixed or variable, are manufactured by many organisations in the private sector, ranging from multinationals to large and small Indian companies. To name a few, there are Philips (Vishay), Goa Resistors, Watts Electronics, Cermet Resistronics, Thakur and Keltron, MFR Electronics, Intron, Omega, Kiyosh, Hi-Tech, PEC, RMC, Variturn, KSI, Pankaj, Potel, Pavan, Unipot, Carpo, Elcon, Stead, RESCO, and many others. There are many in the unorganised sector as well, who specialise in the manufacture of low cost carbon film resistors and potentiometers for the consumer products industry.

What players offer

Incorporated in 1953, Stead Electronics is a manufacturer of WWR, wire resistors, wire wound rheostats and potentiometers. Its products are extensively used by electronics industries and technical institutes/laboratories. They are used for testing as well as conversion from current to voltage and voltage to current. “Manufactured under stringent quality control measures, our products ensure smooth operation, accurate results and minimal long term wear and tear. The company sources most of the raw materials from Europe, Japan and Taiwan, and locally as well. It has the capacity to manufacture 3 million resistors per annum,” says OP Nangia, CEO, Stead Electronics India Pvt Ltd. “We manufacture special types of resistors in accordance with customer specifications,” Nangia adds.

Kaytron Components Pvt Ltd, an ISO 9001:2000 company, is engaged in the manufacture of various types of resistors including coated WWR, 1-7 watt, metal, carbon and metal oxide film resistors. “We manufacture and supply products as per customer requirements, everytime with improvements in quality management systems,” says Daljit Singh Kochar, director, Kaytron Components.

“Our group specialises in the manufacture of variable resistors using indigenous technology. All our products are import substitutes and our brands command a respectable position in the market,” informs Pankaj Kinariwala. The company also specialises in single turn, wire wound and conductive potentiometers of 1, 3, 5, 7.5 and 15 watt rating in the single cup or ganged variants; multi-turn wire wound potentiometers (3, 5, 10, 20 and 40 turns) in single or ganged variants; servo pot (wire wound and conductive plastic), linear motion potentiometers; short stroke linear motion potentiometers and paddle operated potentiometers with or without switches. The company has recently introduced contactless absolute servo encoders using ‘hall’s effect’ technology, digital potentiometers and motorised potentiometers.

Bengaluru based Resistors Manufacturing Company manufactures WWR, with silicon coating or ceramic encasing. “We manufacture the complete range of axial and radial leaded resistors. Our resistors mainly find application in power supplies, automotive and locomotive equipment. We also manufacture fusible resistors and surge resistors,” says Shobhana Prakash, managing partner, Resistors Manufacturing Company.

Cermet Resistronics Pvt Ltd is a leading manufacturer of electronics and electrical grade resistors in India. It is an ISO 9001:2000 certified company, which claims to be the only manufacturer of thick film, metal glaze, high voltage, hybrid resistors and resistive load banks in India. Cermet have supplied resistors to CERN, the European Organisation for Nuclear Research. It has received order for 3000 kW load bank against stiff technological competition from the European reputed manufacturers. Cermet is also known for making resistors of automotive industry such as resistors for fan blower assembly, fuel indicator and resistors for air conditioner.

Says Khadilkar, “We have the widest range of CFR, MFR, MOR, MGR and wire wound power resistors up to 1200 W. We offer solutions for varied applications such as high voltage and high mega ohm, current sense and shunts, fusible wire wound, network, precision metal film and metal glaze. We export to Germany, Italy, Russia, Middle East, Brazil, New Zealand and the USA.”

Watts Electronics manufactures carbon film resistors, metal film resistors, metal oxide resistors, WWR and current sensing resistors. “We market the complete range of chip resistors from our principals in Taiwan. We guarantee our products and if there is any fault, we arrange a complete replacement,” informs S Ramakrishnan, director, Watts Electronics Pvt Ltd. Watts Electronics is one of the largest manufacturers of resistors in the country, having a manufacturing capacity and production of over 1000 million resistors per annum.

Intron is a manufacturer of precision radial resistors with low tolerances down to 0.05 per cent and very low temperature coefficients (TCR) of 5 ppm. The company has a steady client base that serves manufacturers of professional grade quality equipment. Sujata Soparkar says, “We at Intron are concentrating on precision resistors and resistor networks. We cater to the needs of specialised applications wherein accuracy is paramount. We have also introduced hybrid networks, which serve our clients with custom designed products.” Intron offers good price-to-value ratio to its customers so that they do not have to compromise on accuracy.

Rabyte Electronics Ltd is a distributor of different types of resistors like chip resistors, carbon composition type resistors, film resistors, thick film resistor, WWR, ceramic and metal oxide resistors, adjustable resistors and resistor network. Says Raj Gaurav Batra, director, Rabyte Electronics Ltd, “Our resistors are imported from Yogeo Corporation (Japan), who has the largest range of resistors with best quality. We mainly specialise in the supply of surface mounted type resistors,which incorporates electrodes suitable for PCB surface mounting; carbon composition type resistors, which are used in general purpose circuits where initial accuracy and stability with variations of temperature are not deemed critical and adjustable resistors. These are used in audio and TV applications. Besides providing technical support to our customers, we keep large stocks to ensure on time delivery.”

Technological innovations

Over the years, new techniques and advances have helped shrink equipment size and put pressure on manufacturers of discrete components to develop devices that approach the ideal in performance. Among these devices are chip resistors, which remain in high demand today and are among the basic building blocks for many circuits. They are more space efficient than discrete encapsulated resistors and require less preparation prior to assembly. As they have grown more popular, their capabilities have also become more important.

Nagia of Stead Electronics further adds, “The demand for WWR has slowly started declining because of their size, bulkiness and weight. WWR are not available in true chip form (a chip without a moulding), and therefore, are not usable in applications where weight and size limitations demand precision in the chip resistor format.”

“Demand for smaller resistors continued to accelerate despite technical problems associated with the miniaturisation of electronic devices. Consumer demand for smaller, easily portable electronic products such as compact cellular phones, lightweight laptop computers, and personal digital assistants drove the market towards miniaturisation of components like resistors. Such miniaturisation heralded the increasing integration of resistors, capacitors, inductors, and logic circuitry into chip products via thin film on silicon technology,” says Daljit Kochar.

“The resistor market is entirely dependent on the development of the electronics and telecommunication industry within the country. Due to technological advancements, miniaturisation and cost advantages, the electronics industry is moving away from leaded to chip resistors,” says Ramakrishnan of Watt Electronics.

Agreeing to Ramakrishnan, Shobhana Prakash says, “Over the years, miniaturisation and customisation has started taking place, as a result, the size of electronic equipment is getting smaller. We work with OEMs from the design stage itself and develop resistors to most exact specification/requirements.”

Raj Gaurav Batra adds, “As miniaturisation is the recent trend, manufacturers have to make efforts to decrease the size of the resistors and increase its power to size ratio.

Another innovation taking place in resistors is precision—how accurate the resistor is. Resistors are specified with a nominal resistance value and a tolerance stated in percentage. This tolerance states the maximum deviation of a single resistor from its nominal value. Two resistors of the same value are not equal as their tolerances are high. Now, the resistors are coming with tight tolerances which can ensure optimal performance. As a result, technological innovations in the field of resistors has made the prices of the resistors quite competitive.”

Soparkar adds, “The latest development in the resistors field is the integration of the resistors into the PCB itself. The resistive material is coated or deposited onto the glass epoxy itself and etched to get the resistors along with the interconnections. At Intron, we are gearing up to provide our clients with custom designed products that would help them achieve flexibility, along with confidentiality.”

Khadilkar says, “Lower wattages (below 2W), more precision and imported SMDs are getting more popular. Keeping this in mind, we are coming up with high voltage thick film resistors of a special variety.”

Technology advancement, in general, has no boundaries, and so is the case with fixed resistors. Currently, metal film resistors that are highly stable and accurate, thick film cermet resistors for SMT and thick film power resistors have been catching up. And in the case of variable resistors/potentiometers, multi-turn cermet presets (leaded or SMD), multi-turn wire wound and conductive plastic have started gaining ground. However, India has yet to see the widespread use of hybrid potentiometers, with its advantage of high stability over a wide temperature range and its long life. This is due to its limited application and high cost.

Pankaj Kinariwala says, “Hall’s effect based contactless potentiometers that are used as position sensors in the automotive industry also find application in machine tools, printing machines and robotics. In future, once the cost comes down, these are all set to replace conventional types of potentiometers due to their very long service life.”

Buyers face challenges

Buyers are usually confused, weighing quality against price. The tendency is to always go for a lower price or for a particular brand. Buyers of small quantities tend to trust the source from where materials are procured, while not knowing anything about the quality and support. “These days, buyers have even begun to fear purchasing reputed imported brands due to counterfeit manufacturing activities in some other Asian countries. We feel it is always advisable to source Indian brands since not much is heard about the duplicate labelling of these products. One is also assured of quality and technical support,” Pankaj Kinariwala says.

Purchasing resistors or any such component is not like sourcing other equipment or white goods. Component specifications are generally well known to customers. The typical buyer’s requirement is quick delivery—preferably off-the-shelf, but this is possible only at a higher cost. “Most resistors, especially the wire wound type, are made to order. Hence, delivery periods range from 6-12 weeks, which again, buyers are not prepared for; and yet they fail to order well in advance. Therefore, on time deliveries is one of the biggest challenges faced by most manufacturers,” highlights Shobhana Prakash.

As the market is brimming with inferior Chinese products, buyers will have to be careful while buying resistors, since a number of poor quality imported products are readily available, cautions Ramakrishanan.

Raj Gaurav Batra also agrees that as most buyers are not aware of the authorised source that provides genuine parts, they face problems of components availability and pricing.

Tips for buyers

Since the resistors industry is unorganised, buyers should be very careful while making a purchasing decision. The credibility of the company should be looked into, and it is also essential to have some knowledge about the product.

Nangia says, “WWR manufacturing is very labour intensive, which is one of the reasons for doing fairly well in India. But since it is labour driven, volume production takes time. Therefore, buyers have to keep this in mind while planning their purchases.”

Even when buying a reputed brand, buyers should ensure the product’s quality is repeated in each batch, and ensure that technical and logistic support is available from the manufacturers or their agents. A long functional life with stable performance should be the main parameter while selecting resistors or potentiometers. The date of manufacture should also be considered, particularly while buying variable resistors (potentiometer) since very old unused products are susceptible to internal oxidation resulting in poor performance.

“We would like to encourage customers to be quality conscious rather than just cost conscious. It is better to get good value for money instead of going for the cheapest component. Although the resistor accounts for just a small percentage of the cost of the circuit, if not chosen judiciously, it could turn out to be the weakest link that causes a lot of damage. We provide technical assistance to choose the most optimum type of resistor depending on the application and, if necessary, we develop the resistor to the customer’s specifications,” concludes Soparkar.

According to Raj Gaurav Batra, while purchasing resistors, a buyer has to keep in mind the following factors such as resistance value, absolute tolerance, voltage rating, temperature coefficient of resistance and power rating, being the most important parameter.

Types of resistors

Precision wire wound resistors: Wire wound resistors are generally classified as either power wire wounds or precision wire wounds. Power wire wound resistors are subject to greater changes in service and are not used where precision performance is required.

Thin film resistors: Thin film resistors consist of a metallic deposition (made by vacuum deposition or the sputtering process). Thin films can produce a higher resistance and are cheaper as well. This makes them quite economical and more space—efficient where high resistances are needed with intermediate levels of precision.

Thick film resistors: Thick film resistors are much more universally used because of their much greater resistance density (high resistance/small size) and modrate cost. They have a faster frequency response, similar to thin films and foil, but are the noisiest of all currently used resistor technologies. Thick film is a unique technology having high voltage withstanding capability and high resistance values.

Foil resistors: A specific foil alloy with known and controllable properties (Ni/Cr with additives) is applied to a special ceramic substrate, resulting in a thermo-mechanic balance of forces. A resistive pattern is then photo-etched in the foil. These capabilities bring high stability and reliability to system performance without any compromise in accuracy, stability and speed.

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