ROHM defines the ambient temperature as the temperature surrounding a an isolated (unconnected) resistor based on a number of factors. For reference, we list the following excerpts from JIS (Japanese Industrial Standards) defining ambient temperature (similar to IEC 68-3-1 and 68-3-1A). [Source: JIS Handbook ‘Electronic Test Methods: JIS C 0010 Environmental Test, Part 1 – General and Guidance (IEC60068-1:88)]. 4.6 Ambient temperature : Temperature of the air defined for the two following cases.Note : In applying these definitions, guidance should be sought from JIS C 0000/IEC 68-3-1 and its supplement 68-3-1A. 4.6.1 Non-heat-dissipating specimens : Temperature of the air surrounding the specimen. 4.6.2 Heat-dissipating specimens : Temperature of the air in free air conditions at such is neglibible. Note : In practice, the ambient temperature is taken as the average of temperature measured at a number of points in a horizontal plane situated between 0mm and 50mm below the specimen at half the distance between the specimen and the wall of the chamber or at 1m distance from the specimen, whichever is less. Suitable precautions should be taken to avoide heat radiation affecting these measurements. : unquote JIS C 0095 Background Information, Section One – Cold and Dry Heat Tests 1.4 Ambient temperature Users of components and equipments, particularly equipments, require to know the maximum and minimum values of ambient temperature between which the item will operate and these should be specific for the purposeof testing. Certain difficulties arise here due to the fact that heat transfer is connected with temperature gradients and that therefore the temperature of the medium surrouding device is necessarily varying in space. Consequently, the "ambient temperature" of the surrouding atmosphere shall be specially defined. : unquote
Rectangular chip resistors possess two electrodes consisting of three layers over a ceramic substrate (alumina). The bottom layer is a silver-based thick film material, the middle is composed of nickel, and the top layer is tin. Please note that all ROHM chip resistors are lead-free.
ROHM performs 3 types of tests: 1. Temperature cycling (3000 cycles, -30ºC/+80ºC) 2. High temperature/High humidity (60ºC, 80%RH, 2000hrs) 3. Storage at room temperature for 3000hrs The surface is then verified using a scanning electron microscope. Whiskers must be less than 0.1mm in length.
Please refer to the ‘Soldering Conditions’ section on our website for details. Generally, Pb-free solder paste (Sn-3Ag-0.5Cu) should be used. Flow and manual soldering is not recommended for ultra-compact chip resistors (0201 size) or chip networks (0402×2, 0402×4, 0603×2, 0603×8) due to possible solder bridging. However, if such methods will be used, ROHM recommends thorough testing under actual conditions before mass production.
The pulse limit is determined from the rated current or the maximum voltage per element, regardless of pulse time. In the case of a single pulse (one time voltage pulse), reference data is available. For continuous pulse operation data can be provided upon request.