The construction of metal film resistors by placing them in a vacuum and depositing a metal layer onto a high-purity ceramic cylindrical rod is a process referred to as the Vacuum Sputtering Process. In general, the thicker the metal film deposited, the more stable the resistor value.
Inside the vacuum drum, high-velocity electrons are firing at the nickel-chromium anode (known as the target) and surface molecules are dislodged to form a nickel-chromium vapor. Tumbling the rods in the drum causes the vapor to deposit evenly. The duration in the drum determines the thickness of the film, and it is this important process that determines the resistance of the final resistor. The precision of the film affects the noise of the final resistor, with thinner films being noisier than thicker films. If the nickel-chromium alloy contains impurities, it will become more granular, and this also causes noise.
The final process is to insert the end caps fitting to allow connection to the resistive film. These end caps are an interference fit onto the rods, and their precise fitting is critical.
Sannohm MFR resistors are manufactured with high-quality materials and a precise control process.
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