Editing Resistor (section)

===Thick and thin film===
[[File:Laser Trimmed Precision Thin Film Resistor Network.JPG|thumb|Laser Trimmed Precision Thin Film Resistor Network from Fluke, used in the Keithley DMM7510 multimeter. Ceramic backed with glass hermetic seal cover.]]
Thick film resistors became popular during the 1970s, and most [[surface-mount technology|SMD]] (surface mount device) resistors today are of this type. The resistive element of thick films is 1000 times thicker than thin films,<ref name="Film Comparison">{{cite web|title=Thick Film and Thin Film|url=http://www.digikey.com/Web%20Export/Supplier%20Content/Stackpole_738/PDF/Stackpole_ThickFilmXThinFilm.pdf|publisher=Digi-Key (SEI)|access-date=23 July 2011|archive-date=27 September 2011|archive-url=https://web.archive.org/web/20110927122203/http://www.digikey.com/Web%20Export/Supplier%20Content/Stackpole_738/PDF/Stackpole_ThickFilmXThinFilm.pdf|url-status=dead}}</ref> but the principal difference is how the film is applied to the cylinder (axial resistors) or the surface (SMD resistors).

Thin film resistors are made by [[sputtering]] (a method of [[vacuum deposition]]) the resistive material onto an insulating substrate. The film is then etched in a similar manner to the old (subtractive) process for making printed circuit boards; that is, the surface is coated with a [[photoresist|photo-sensitive material]], covered by a pattern film, irradiated with [[ultraviolet]] light, and then the exposed photo-sensitive coating is developed, and underlying thin film is etched away.

Thick film resistors are manufactured using screen and stencil printing processes.<ref name=Vishay08/>

Because the time during which the sputtering is performed can be controlled, the thickness of the thin film can be accurately controlled. The type of material also varies, consisting of one or more ceramic ([[cermet]]) conductors such as [[tantalum nitride]] (TaN), [[Ruthenium(IV) oxide|ruthenium oxide]] ({{chem|RuO|2}}), [[Lead(II) oxide|lead oxide]] (PbO), [[bismuth ruthenate]] ({{chem|Bi|2|Ru|2|O|7}}), [[chromel|nickel chromium]] (NiCr), or [[bismuth iridate]] ({{chem|Bi|2|Ir|2|O|7}}).

The resistance of both thin and thick film resistors after manufacture is not highly accurate; they are usually trimmed to an accurate value by abrasive or [[laser trimming]]. Thin film resistors are usually specified with tolerances of 1% and 5%, and with temperature coefficients of 5 to 50 [[Temperature coefficient|ppm/K]].  They also have much lower [[Resistor noise|noise]] levels, on the level of 10–100 times less than thick film resistors.<ref>{{cite web|title=Thin and Thick film|url=http://www.resistorguide.com/thin-and-thick-film/|website=resistorguide.com|publisher=resistor guide|access-date=3 December 2017}}</ref> Thick film resistors may use the same conductive ceramics, but they are mixed with [[sintered]] (powdered) glass and a carrier liquid so that the composite can be [[screen-printing|screen-printed]]. This composite of glass and conductive ceramic (cermet) material is then fused (baked) in an oven at about 850&nbsp;°C.

When first manufactured, thick film resistors had tolerances of 5%, but standard tolerances have improved to 2% or 1% in the last few decades.{{clarify timeframe|date=December 2021}} Temperature coefficients of thick film resistors are typically ±200 or ±250&nbsp;ppm/K; a 40-[[kelvin]] (70&nbsp;°F) temperature change can change the resistance by 1%.

Thin film resistors are usually far more expensive than thick film resistors. For example, SMD thin film resistors, with 0.5% tolerances and with 25&nbsp;ppm/K temperature coefficients, when bought in full size reel quantities, are about twice the cost of 1%, 250&nbsp;ppm/K thick film resistors.