Thin film chip resistors are manufactured using proprietary versions of TaNx as  resistive material. Via a sputtering process, a very thin metallic film is deposited on a substrate under vacuum conditions. The deposited film is continuous and defect free conferring stability, very low TCR, very low current noise and negligible non-linearity. In contrast, thick film resistors normally use resistance metal oxides  with glass-based materials to form a paste for printing on the substrate. After burning off the solvents and after few other heat treatments the glass filled resistive material has a sponge like structure with random inclusions and defects. These films will absorb gases and moisture  (if not hermetically sealed) causing drifts and long term instability. The random defects are an obvious source of noise and detrimentally affect the temperature coefficient of resistance, TCR. Both thin film and thick film resistors use laser trimming to adjust the resistance value during final steps of the manufacturing process. However, the heat generated during laser trimming causes micro-cracks on a thick film resistor and therefore affects the short term and long term stability. Thin film resistors need less laser power than that needed for thick film resistor. Thin film resistors do not exhibit micro-cracking during laser trimming. Consequently thin film resistors show superior stability and noise performance.TaNx based thin film resistors can be heat treated to adjust the resistance value within 1% or better. This method while tedious and expensive, is preferred in special applications since it conserves the geometrical properties allowing for very good RF matching between devices. Thick film resistors can not be adjusted by same heat treatment method and as such they are 100% laser trimmed. Conclusion: Thin film resistors are the preferred material for all microwave passive and active power components like microwave power resistors, microwave power terminations, microwave resistive power dividers, microwave power attenuators.


 
 
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Advanced Microwave Components

 


APPLICATION NOTE 110
 
 

THIN FILM RESISTORS vs THICK FILM RESISTORS- HOW THEY COMPARE

 

Thin film chip resistors are manufactured using proprietary versions of TaNx as  resistive material. Via a sputtering process, a very thin metallic film is deposited on a substrate under vacuum conditions. The deposited film is continuous and defect free conferring stability, very low TCR, very low current noise and negligible non-linearity.

In contrast, thick film resistors normally use resistance metal oxides  with glass-based materials to form a paste for printing on the substrate. After burning off the solvents and after few other heat treatments the glass filled resistive material has a sponge like structure with random inclusions and defects. These films will absorb gases and moisture  (if not hermetically sealed) causing drifts and long term instability. The random defects are an obvious source of noise and detrimentally affect the temperature coefficient of resistance, TCR.

Both thin film and thick film resistors use laser trimming to adjust the resistance value during final steps of the manufacturing process. However, the heat generated during laser trimming causes micro-cracks on a thick film resistor and therefore affects the short term and long term stability. Thin film resistors need less laser power than that needed for thick film resistor. Thin film resistors do not exhibit micro-cracking during laser trimming. Consequently thin film resistors show superior stability and noise performance.

TaNx based thin film resistors can be heat treated to adjust the resistance value within 1% or better. This method while tedious and expensive, is preferred in special applications since it conserves the geometrical properties allowing for very good RF matching between devices. Thick film resistors can not be adjusted by same heat treatment method and as such they are 100% laser trimmed.

Conclusion: Thin film resistors are the preferred material for all microwave passive and active power components like microwave power resistors, microwave power terminations, microwave resistive power dividers, microwave power attenuators.


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