Thick film resistor values typically range from 0.01 Ohm to 50GOhm. By using specialist materials and manufacturing techniques it is possible to manufacture very high-value resistors in the low TOhm range, but these tend to be high-cost devices for specialist applications.
The actual resistor value available depends on many factors. They include the type of thick film resistor package and application issues such as power rating.
Thick Film Resistor Package Styles
By far the most common thick film resistor package style is the surface mount package. The flip-chip variant of the surface mount package is found in more specialist applications.
MELF (Metal Electrode Leadless Face) and axial packages are common, general-purpose resistor devices. Where higher power handling capabilities are required the TO style package and packages specifically designed for heatsink application are the most common types.
For some applications resistor networks (both leaded and surface mount) are the best choice. Or, if a standard package will not match the demands of the application specialist manufacturers can deliver application-specific custom resistor packages.
Construction vs Resistor Value
The thick film resistor manufacturing process is discussed elsewhere in this blog. The standard process (and materials) are modified to suit the package style and application.
Surface mount thick film resistor values tend to be in the 0.1 Ohm to 100MOhm range. In contrast, MELF and Axial lead package values are usually in the 10 Ohm to low GOhm range.
TO style packages are primarily used in higher power applications with typical resistances in the 0.01 Ohm to 500KOhm range.
Thick Film Resistor Stability And Ageing
Several factors can degrade the resistor value. It is important to consider resistor ageing and its impact on system performance over the medium to long term. Thick film resistor stability over time is often a key consideration in power applications.
Thick film resistor value is one of many issues to consider when choosing a resistor. It is important to understand the application, especially power rating and environmental factors such as temperature and moisture. Thick film resistor tolerance can be a key factor in some applications.
The power rating and potential surge events will often dictate the package style and limit the range of resistor values available. An extensive range of standard thick film resistors is available. Where a standard product will not match the demands of the application a custom thick film resistor may be a solution.