Technical Trend of Resistors
Trend of Development
High density mounting
Mainboards of cell phones and smartphones have applied 0402 size electronic components. The requirements for higher performance in the restricted space are increasing, as requirements for composition of components are becoming remarkable than downsizing of chip product. In mounting technology, narrow space mounting is achieved by fillet-less mounting to improve mounting density. Not only a resistor but resistor network will need downsizing and BGA(electrodes on the product bottom).
To achieve high density mounting, DES(Device Embedded Substrate)technology is actively developed. DES technology is based on the idea of layouting components in three dimension by embedding electronic devices into a substrate, which varies whether embedding devices through the manufacturing process of the substrate or applying printing technology to include into the inner layers instead of embedding, etc. KOA is developing XR73, resistors for embedded as EPD( Embedded Passive Device ).
To achieve power management performance of portal devices, high precision measurement of current is required. To measure the circuit current in general, first you insert current sense resistors in serial into a circuit then measure each voltage of both ends of the resistor. Like cell phones, however, when the current gap happens to be more than a hundred times between standby and talking time or taking pictures, the current in both cases should be measured precisely and the current sense resistors required to be high precision of low T.C.R. , less affected by temperature change. Our thick film type low resistance resistorsUR73, SR73offer wide resistance and T.C.R. variation from 10mΩ to 10Ω and T.C.R. of ±１００ x10-6/K.
CPU power supplies of notebook PC apply DC-DC converters, which require output stability enabled to follow the load change of CPU, so the switching speed becomes extremely high. Parastic inductance of electronic components applied for control circuit of DC-DC converters will affect largely. So current sense resistors of low parastic inductance are required.
Our Metal plate chip type low resistance resistor TLR series has extremely small parasitic inductance and enables high precision current detection.
Car electronics devices require high reliability as they are under severe envinroment. Especially for engine peripherals, such devices have to work for long time under high temperature, humidity, tough vibration, dust and other chemical substances. Resistors applied for those applications should have excellent heat resistance, moisture resistance and sulfuration resistance, as well as the high reliability of junction to the PWB to tolerate continuous thermal stress and strong vibration.
High voltage type
For AV devices like plasma displays and LCD projectors, their power supplies use high voltage, which require electronic components in the drive circuits to have high max. working voltage. Vehicles increasingly apply high voltage circuits like discharge type head lamp. Power supply circuits of EV and HEV use high voltage, which also requires resistors to have high max. working voltage. High voltage type resistors
High voltage type resistors HV73、RCR
Electronic circuit substrate had been applying Pb-contained solder, alloy of tin and lead, but because of lead's adverse effect on human body and environment, the trend of Pb-free soder is becoming popular in recent years. As of July 2006, RoHS regulations in Europe prohibits to use six hazardous materials including lead. Even in other countries like Japan and China, such regulations are becoming enhanced while we are trying hard to eliminate environmental hazardous materials as well as to promote Pb-free terminal resistors in wide lineup.
Requirements for Resistors
Mounting reliability of 0402 resistors
To achieve 0402 size resistors, mounting technology is important. To mount extremely small components accurately, product shape is accurate and stable as well as high precision printing technology of cream solder and mounting technology. Carrier tape precision is also required.
High voltage withstanding, high reliability
To achieve high voltage type product and high reliability, resistive material itself needs improvement.
The movement of Pb-free is required now not to use Pb-contained solder for electrode plating of resistors. In the future, every one of material such as resistor film, protective film and inner connecting solder are required to be Pb-free.
The downsizing of resistors is nearly the limit and in the coming years DES(Device Embedded Substrate) compounding EPD including resistors, capacitors and inductors or semiconductor EAD(Embedded Active Device) seems to become popular. To enable high speed transmission or processing, a conventional current as an electric signal has achieved integrating with optical signal and emerged as electric and optical circuit. DES including optical components seems also to be promoted.
The recent market requires higher density mounting, which leads to the request for higher power at conventional product size. Resistors had been used with luxury of derating before while resistors are getting used with tight derating recently. We have to improve resistors themselves as well as to study the rated power of resistors, mounting method, recommended pattern layout, etc., to take necessary measures to these trends.