Electronic Components Blog

Friday, 26 September 2014 12:13

Isabellenhütte shunts differ from the competition

Isabellenhütte Presision and Power Resistors, -Alloys and Measurement

The precision and power resistors of Isabellenhütte primarily differ in terms of their manufacturing technologies: ISA-PLAN® (etched foil resistors) and ISA-WELD® (electron beam welded composite material of Cu-MANGANIN®-Cu).

These two technologies enable to meet the most demanding applications: high long term stability, continuous load capacity as well as high pulse power rating, minimized dissipated energy in high current metering, low inductance- and TC-values and low thermoelectric voltage against copper. Both technologies complement each other which results in a large portfolio of precision resistors.

The precision resistors guarantee:
• High permanent power in small sized construction
• Extremely low TC-values
• Very good long term stability
• Low ohmic resistor values start at 2 µOhm
• High continuous load and pulse load capability
• Standard delivery meeting the closest tolerances
• Thermoelectric voltage against copper eliminated as far as possible
 

ISA-PLAN® - TECHNOLOGY

Using etching technology, the resistance elements are manufactured from foils of precision resistance alloys (Manganin®, Zeranin®), that are mounted electrically insulated on a good heat-conducting metal substrate. The planar structures permit low-inductance design forms and very low thermal internal resistances. An optimized cur-rent-density distribution avoids the danger of Hot Spots.

Besides the conventional two and four-wire current-measuring resistors, there are presently seven SMD product families available. They offer a variety of possible uses, among others, in the fields automotive, power electronics, motive power engineering, energy measurement and medicine technology as well as aviation and aerospace.

The production process of ISA-PLAN®-resistors starts with bonding the MANGANIN®- or ZERANIN®-foil to a metal substrate of copper or anodized aluminium. This thermally conductive connection between resistor alloy and adhesive results in optimized adhesion, isolation and especially low thermal resistance. Following a pre-treatment under high pressure and temperature, the resistor and substrate are laminated in a vacuum. This assures a constant adhesion without voids or cavities.

After cleaning the marking and punching the fitting holes follows a photo lithographical process in which already single resistor structures are being defined. The entire construction in connection with the etching enables the production of ideal four-terminal SMD-resistors in the low-resistance range.

The four-terminal (Kelvin) connection effectively eliminates the influence of copper on the overall resistance. The TK of the components also assures highest reproducibility. Influences of the solder joint quality on the resistance value can here be excluded.

Together with the layout of the electrical panel the 2-terminal versions can realize a quasi 4-terminal connection. This connection replicates almost the ideal 4-terminal configuration.

After the etching process further chemical treatments are following as well as widely automated processes such as laser processing and trimming. To identify weak spots in the etching structure each resistor is tested by electric pulse load followed by an analysis of the IR-picture. The separation of the resistors and substrate is made possible by a lasering process, punching or sawing.

The finishing progress such as cleaning, resistance check, optical control, labeling and packaging are completely automated. The resistors are packed in tape and reels for the automated SMD-equipment. The ready reels are sealed in evacuated plastic bags and refilled with dry nitrogen to assure that solderability is maintained. Each reel is marked by a barcode label to insure the traceability of all product- and producing relevant datas. If desired an additional marking with a customer specific component number is of course possible.

ISA-WELD® - TECHNOLOGY

The resistors of the patented ISA-WELD®-method consist of massive, electron beam welded composite material of copper and one of the resistor alloys (MANGANIN®, ZERANIN®, ISAOHM® or Aluchrom). This composite material can be adapted to almost any form by punching and bending and enables highest flexibility in the field of application design. These shunts are used in high current applications of the automobile industry, industrial- and power electronics, battery charging, drive technologies and for electronic energy metering.

The resistors are punched out of three longitudinally welded strips in which the procedure is very flexible. Thickness and widths of the strips are as variable as the resistor materials used. The almost free shaping capability in the punching, bending and stamping process leads to increasing design solution options for the application in question.

The composite material is welded continuously at the strip in a vacuum via electron beam and without any additional material. Additionally the strips are cleaned upon machine entry and the flanks are finished by machine. By doing this impurities or oxides in the weld can be avoided and physically different materials can be welded cost-effeciently - with zero-defects. A special advantage is the small welding area with about one third of the metal thickness. Due to this the transition occurs abruptly which minimises the influence of the alloy area to the resistor value and the electric features of the metering resistor. Your advantage as user: the connection of resistor material and copper during the component assembly on the electrical panel or busbar must not be done by yourself.

The comparatively low leading resistance of the copper connections make sure that the total resistance value is only marginal higher than the actual measuring resistor. The total load is reduced to a minimum by doing this.

Additionally the heat which is generated in the resistor material is dissipated very efficiently in the conterminal copper connection.

Due to an extremely high conductivity the massive copper connections additionally ensures a uniform current density and heat distribution in the resistor. Hot Spots can be avoided this way and a high pulse and permanent load can be achieved.

SEE FOR YOURSELF

If you're designing an application in the above mentioned fields of work and you're feeling an interest in applying a low-ohmic precision resistor, please contact Heynen for some design-in support and supply of free samples. Even a sample PCB is available which can be connected to the electric circuit for testing purposes.