Can Fiber Lasers be Used to Cut Resistors?
Resistor trimming is a standard process in the electronics industry. Both thin film and thick film resistors are trimmed to fine-tune their resistance. They are designed so that after deposition, their resistance value is lower than required, and the resistance value is increased by removing material.
Thick film resistor laser trimming
Thick film resistors are deposited onto a substrate, typically ceramic, by screen printing a paste containing a resistor material such as ruthenium dioxide, glass frit, and an organic thixotropic medium in which the other contents are suspended. The substrate is subsequently fired using a carefully controlled heat cycle with a peak temperature of around 850 oC. This volatilises and burns off the organic medium finally fusing the ruthenium dioxide and glass, forming a strong bond with the ceramic substrate.
The fired resistor is in the order of 100 micrometres thick and has a glassy appearance. Such resistors may be added to an electronic hybrid substrate which includes additional circuitry, or it might be printed onto a substrate which is subsequently cut to form individual chip resistors.
Trimming is an ablation process that involves measuring the resistance and removing resistor material until the target resistance is obtained. Historically air abrasive processes were used, but today fiber lasers are used as they are much cleaner, reliable, reproducible and require very little maintenance.
Thin film resistor laser trimming
Thin films resistors are deposited onto a substrate using thin film deposition, usually sputtering. While alternative materials can be used to make the resistive element, the most common is an alloy of nickel and chromium. Substrates are typically ceramics, silicon, or glass. Unlike thick film deposition, it is a low-temperature process. Usually, the film is around 100 nanometres thick.
Fiber laser trimming is carried out similarly to thick film resistors. However, thin film resistors are usually significantly smaller than their thick film counterparts and more sensitive to processing conditions. Trimming can be exact, and many different trim patterns are used.
Fiber laser cutting is used extensively in the electronics industry to precisely adjust the values of thick and thin film resistors. This is just one of many processes where fiber laser technology is contributing to the increasing complexity and reducing the cost of electronics devices.
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Image Credit: Oskay
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