Patent Description:
Resistors are used in various ways in numerous electronic devices and other devices, and different types of resistors have been developed over the years. A "surface mount" resistor generally represents a resistor having electrical terminals that are mounted on the surface of a printed circuit board or other substrate. A "thin film" resistor generally represents a resistor formed by depositing a thin layer of resistive material onto a ceramic base or other substrate. A "thick film" resistor generally represents a resistor formed by depositing a thick paste of resistive material onto a printed circuit board or other substrate.

Surface mount resistors are typically not low-profile or low-cost devices, and the use of surface mount resistors can lead to the creation of parasitic capacitances and parasitic inductances in circuits or devices. Thick film resistors often would be more suitable for use in higher-current or higher-power applications than thin film resistors. Unfortunately, thick film resistors can have difficulty adhering to certain types of substrates. Also, thick film resistors can still have limited current- and power-handling capabilities, which may prevent their use in certain higher-current or higher-power applications. Further, it is often more difficult to control the geometries (and therefore the resistances) of thick film resistors compared to thin film resistors. Thick film material used to form thick film resistors typically has high viscosity and high shrinkage after curing, which make geometry control difficult. In addition, manufacturing techniques for thick film resistors often involve sintering or other high-temperature operations, which can often involve temperatures of up to <NUM>° C, <NUM>° C, <NUM>° C, or even more. These temperatures can damage other electrical components, preventing the use of these manufacturing techniques for various applications.

<CIT> discloses a printed resistor comprising a ceramic base, an adherent layer of resistance material consisting of from about <NUM>% to about <NUM>% of cross-linked epoxy resin, from about <NUM>% to about <NUM>% of finely divided conducting particles and from about <NUM>% to about <NUM>% of finely divided non-conducting particles deposited upon said base, and terminal contact areas provided at spaced portions of said layer.

<CIT> discloses a high voltage resistor arrangement. The arrangement has resistance paths consisting of a polymer paste printed on a support material, where the support material is made of plastic. The polymer paste may comprise an epoxy resin in which there are embedded electrically conductive particles of carbon black and/or graphite, as well as dielectric particles of titanium oxide and/or aluminium oxide and/or silicon dioxide.

<CIT> discloses a method for manufacturing a thick film resistor including the step of sintering a thick film resistor paste. The paste may comprise a glass composition, such as CaO-based glass, SrO-based glass and ZnO-based glass, a conductive material, such as ruthenium oxide, and additives for the purpose of adjusting the resistance value and temperature characteristics. Examples of the additives include titanium compounds and metal oxides.

This disclosure provides thick film resistors having customizable resistances and methods of manufacture.

According to the present invention, there is provided a method according to appended claim <NUM>.

In some examples, depositing a modified carbon-based thick film material onto the structure comprises depositing the modified carbon-based thick film material onto the structure such that the deposited modified carbon-based thick film material connects multiple conductive traces.

For a more complete understanding of this disclosure, reference is made to the following description, taken in conjunction with the accompanying drawings, in which:.

As noted above, thick film resistors would often be more desirable or more suitable for use than thin film resistors and surface mount resistors, but thick film resistors can suffer from a number of disadvantages. For instance, thick film resistors can have difficulty adhering to certain types of substrates, such as those formed from polytetrafluoroethylene (PTFE) or other types of substrates, and may have limited current- and power-handling capabilities. Also, thick film material that is used to form thick film resistors typically has high viscosity and high shrinkage after curing, which makes geometry control (and therefore resistance control) of the thick film resistors difficult. In addition, manufacturing techniques for thick film resistors often involve the performance of sintering or other high-temperature operations, which can damage other components.

This disclosure describes various techniques for printing or otherwise forming thick film resistors having customizable resistances. As described in more detail below, a carbon-based ink, paste, or other thick film material can be modified by adding dielectric material (generally referred to as a "modifier") to the thick film material in order to produce a modified thick film material. According to the invention, the dielectric material includes at least one titanate, such as barium titanate (BT), strontium titanate (ST), or barium strontium titanate (BST). The amount of modifier added to the carbon-based thick film material may be based on the desired resistance of the modified thick film material. The modified thick film material is then printed onto printed circuit boards or other substrates or structures. cured, and processed to form thick film resistors.

The amount of modifier added to the carbon-based thick film material alters the resistance that can be obtained using the thick film material. This allows the resistances of the thick film resistors formed using the thick film material to be controlled or customized as needed. However, the amount of modifier added to the carbon-based thick film material does not exceed about <NUM>% by weight. This allows the carbon-based thick film material to retain adequate conductive carbon particles to achieve substantial current- and power-handling capabilities while also achieving at least double a resistivity (compared to the resistance of the thick film material itself).

In this way, thick film resistors can be manufactured having lower physical profiles and less parasitic capacitances and inductances than surface mount resistors while being able to handle higher currents or powers than thin film resistors. Moreover, because the surface energy of the modified thick film material is relatively low, the thick film material can adhere well to many substrates (including PTFE substrates). Further, these approaches allow for improved control of both the geometry and the resistivity of the thick film material. For instance, the viscosity of the uncured modified thick film material can be lower compared to typical thick film material, which allows for improved control in the deposition of the modified thick film material at higher thicknesses. In addition, thick film resistors can be cured at significantly lower temperatures (such as less than <NUM>° C) while achieving repeatable, stable performance. Overall, this allows thick film resistors to be fabricated having at least one desired geometry while allowing their resistances to be tailored as needed, which can occur using a variety of substrate types and customizable sheet resistivity in a manner that survives lamination temperatures while at the same time not requiring the high-temperature curing of typical resistive inks (often in excess of <NUM>° C).

<FIG> illustrate an example circuit <NUM> having a thick film resistor <NUM> with a customizable resistance according to this disclosure. In particular, <FIG> illustrates a cross-sectional view of a portion of the circuit <NUM> with the thick film resistor <NUM>, and <FIG> illustrates a top view of the portion of the circuit <NUM> with the thick film resistor <NUM>.

As shown in <FIG>, the circuit <NUM> uses the thick film resistor <NUM> to electrically couple two conductive traces <NUM> and <NUM> together, where the thick film resistor <NUM> and the conductive traces <NUM> and <NUM> are positioned over a substrate <NUM>. The conductive traces <NUM> and <NUM> represent any suitable conductive pathways through which an electrical signal can flow to and from the thick film resistor <NUM>. The conductive traces <NUM> and <NUM> may be formed from any suitable material. For example, the conductive traces <NUM> and <NUM> may represent copper traces or other electrical traces formed using one or more conductive metals or other material. Also, the conductive traces <NUM> and <NUM> may be formed in any suitable manner, such as by depositing and etching the conductive material. In addition, each of the conductive traces <NUM> and <NUM> may have any suitable size, shape, and dimensions. Note that the relative positions of the thick film resistor <NUM> and the conductive traces <NUM> and <NUM> in <FIG> are for illustration only and can vary as needed or desired. For instance, the conductive traces <NUM> and <NUM> may be formed over the thick film resistor <NUM>.

The substrate <NUM> represents any suitable structure in or on which electrical components and electrical pathways can be formed. For example, the substrate <NUM> may represent a rigid printed circuit board, a flexible circuit board, or any other suitable base or structure used to carry electrical components and conductive traces or other conductive pathways coupling the electrical components. The substrate <NUM> may be formed from any suitable material, such as cotton paper, woven fiberglass, or woven glass and epoxy resin, carbon, metal, alumina or other ceramic, or PTFE, polyimide, polyester, or other polymer. Also, the substrate <NUM> may be formed in any suitable manner, such as by using a single layer of material or by using multiple layers of material that are laminated or otherwise joined together. In addition, the substrate <NUM> may have any suitable size, shape, and dimensions.

The thick film resistor <NUM> is formed by depositing a thick film material over the substrate <NUM> (and over the conductive traces <NUM> and <NUM> in this example). Once deposited, the thick film material is cured and can then be further processed as needed to form the thick film resistor <NUM>. The thick film material is deposited via printing, such as by using a three-dimensional (3D) printer or other deposition system in an additive manufacturing process. Depending on the other components of a circuit or device, this may allow the entire circuit or device to be formed using an additive manufacturing process.

As described in more detail below, the thick film material used to form the thick film resistor <NUM> is a carbon-based thick film material, such as a carbon-based ink, that has been mixed with or has otherwise incorporated dielectric material (generally referred to as a "modifier"). Any suitable type of carbon-based ink or other thick film material may be used to form the thick film resistor <NUM>, such as a carbon-based ink (like the C-<NUM> carbon resistive ink from APPLIED INK SOLUTIONS). The dielectric material comprises a titanate. Example titanates include barium titanate (BT), strontium titanate (ST), and barium strontium titanate (BST).

The dielectric material incorporated into the carbon-based thick film material alters the resistance of the modified thick film material, and the change in resistance can be based on the amount of the dielectric material incorporated into the thick film material. This allows customization of the resistance of the thick film resistor <NUM> based on the amount of the dielectric material incorporated into the carbon-based thick film material. In some embodiments, the amount of dielectric material incorporated into a carbon-based thick film material can be relatively small and yet still have a large impact on the overall resistances that can be obtained using the modified carbon-based thick film material. A modified carbon-based ink contains up to about <NUM>% (by weight) of the dielectric material, and different percentages by weight of the dielectric material can be used to obtain different resistances of the modified thick film material.

In this particular example, the thick film resistor <NUM> is shown as being generally rectangular in shape (when viewed from on top or on bottom). However, modified thick film material can be printed or otherwise deposited in a wide range of geometries, allowing the thick film resistor <NUM> to be formed having any suitable size and shape for a specific application. Also, the modified thick film material can be printed or otherwise deposited in planar or non-planar geometries. Example types of non-planar geometries may include pyramidal, cylindrical, or rectangular prisms, as well as generally two-dimensional patterns deposited on curved or other non-planar substrates. By allowing both the customization of the resistance of the modified thick film material and the customization of the geometry in which the modified thick film material is deposited, this approach provides a highly-tunable solution that allows thick film resistors to be fabricated with a wide range of resistances and geometries for various applications.

Moreover, thick film resistors can be fabricated to achieve high sheet resistances without negatively impacting the current- and power-handling capabilities of the thick film resistors. This may occur since the bulk of the thick film resistor <NUM> is formed by the conductive carbon or other conductive material in a carbon-based ink or other thick film material (since the thick film material may include a relatively small amount of dielectric material). This allows the use of the thick film resistor <NUM> in higher-current or higher-power applications, such as applications involving up to about <NUM> mA of current and/or up to about <NUM> W or about <NUM> W of power, without fusing.

The modified thick film material allows for fabrication of thick film resistors using dry manufacturing processes. Of course, any other suitable manufacturing processes may use the modified thick film material to form thick film resistors. Also, note that one or more thick film resistors <NUM> can be formed on various types of substrates (including PTFE-based substrates), and each thick film resistor <NUM> can have smaller parasitic capacitance and inductance effects compared to surface mount resistors. Further note that the thick film resistor <NUM> can be stable at room temperatures and stable at high temperatures (depending on the substrate <NUM>). This means that the resistance of the thick film resistor <NUM> can remain substantially constant over time at room temperatures and possibly at higher temperatures.

Once the modified thick film material is deposited and cured (which can occur at relatively low temperatures as described below), additional operations may be performed to adjust the resistance of the thick film resistor <NUM> or to otherwise complete the fabrication of the thick film resistor <NUM>. For example, trimming operations may be performed to alter the shape and therefore the resistance of the thick film resistor <NUM>. Also, additional layers of material may be deposited over the thick film resistor <NUM> and the conductive traces <NUM> and <NUM>, such as to protect these components or to form other electrical components or electrical pathways over the thick film resistor <NUM> and the conductive traces <NUM> and <NUM>.

In some embodiments, the thick film resistor <NUM> can be fabricated to have standard dimensions established by a standards body or by industry practice. As a particular example, the thick film resistor <NUM> may be fabricated to have dimensions defined by standard surface mount device (SMD) resistor sizes. Here, for instance, a "<NUM>" resistor size may refer to a resistor that is about <NUM> inches or <NUM> millimeters in length, about <NUM> inches or <NUM> millimeters in width, and about <NUM> inches or <NUM> millimeters in height. A "<NUM>" resistor size may refer to a resistor that is about <NUM> inches or <NUM> millimeters in length, about <NUM> inches or <NUM> millimeters in width, and about <NUM> inches or <NUM> millimeters in height. Of course, thick film resistors <NUM> may be fabricated to have any other suitable standard or non-standard sizes and shapes.

Although <FIG> illustrate one example of a circuit <NUM> having a thick film resistor <NUM> with a customizable resistance, various changes may be made to <FIG>. For example, the thick film resistor <NUM> may have any other suitable size, shape, and dimensions. Also, the thick film resistor <NUM> may be used in any other suitable manner. In addition, a circuit <NUM> may include any suitable number of thick film resistors <NUM> in any suitable positions or arrangements, and different thick film resistors <NUM> in the circuit <NUM> may or may not have different sizes, shapes, or dimensions.

<FIG> illustrates an example operational flow <NUM> for forming thick film resistors having customizable resistances according to this disclosure. For ease of explanation, the operational flow <NUM> shown in <FIG> is described as being used to manufacture the thick film resistor <NUM> of the example circuit <NUM> shown in <FIG>. However, the operational flow <NUM> shown in <FIG> may be used to manufacture any suitable thick film resistor or resistors in any suitable circuit, device, or system.

As shown in <FIG>, the operational flow <NUM> includes a mixing operation <NUM>, a deposition operation <NUM>, and a curing operation <NUM>. In the mixing operation <NUM>, a mixer <NUM> generally operates to mix a carbon-based ink or other carbon-based thick film material with a titanate or other dielectric material. This helps to ensure that a modified carbon-based thick film material (such as a modified carbon-based ink or paste) has a substantially even distribution of titanate or other dielectric material within the conductive material of the thick film material. The mixer <NUM> represents any suitable structure configured to mix carbon-based thick film material and dielectric material, such as a centrifugal mixer.

During the mixing operation <NUM>, the amount of dielectric material added to the carbon-based ink or other carbon-based thick film material can vary based on the desired resistance of one or more thick film resistors <NUM> to be fabricated. As noted above, the amount of dielectric material added to the carbon-based thick film material can be limited to a relatively low amount, such as no more than about <NUM>% of the total weight of the combined conductive and dielectric materials. Even using relatively small amounts of dielectric material such as titanates in carbon-based inks or other carbon-based thick film material can greatly increase the resistance of the carbon-based thick film material. For example, adding about <NUM>% by weight of barium strontium titanate to a carbon-based ink (such as C-<NUM> carbon resistive ink) may increase the resistance of the carbon-based ink by more than <NUM>%. Thus, small amounts of titanate or other dielectric material can quickly increase the resistance of the modified carbon-based thick film material, which allows a fusing current of the manufactured thick film resistor <NUM> to remain high even with the presence of the dielectric material in the modified thick film material. The dielectric material at least doubles the resistivity of the carbon-based thick film material.

In the deposition operation <NUM>, a modified thick film material <NUM> (which is produced by the mixing operation <NUM>) is deposited onto a substrate or other structure. In this example, a printer <NUM> deposits the modified thick film material <NUM> onto a structure <NUM>', which represents the circuit <NUM> of <FIG> without the thick film resistor <NUM>. Of course, the printer <NUM> may deposit the modified thick film material <NUM> onto any other suitable circuit or other structure. The printer <NUM> represents any suitable structure configured to print thick film material <NUM> onto one or more structures in order to form one or more thick film resistors <NUM>, such as a 3D printer. As a particular example, the deposition operation <NUM> may be implemented using a high-precision dispensing system from NORDSON CORP. Note, however, that the deposition operation <NUM> may use any other suitable equipment to deposit the thick film material <NUM>, such as screen printing or spraying equipment.

When depositing the modified thick film material <NUM> onto a structure, the thick film material <NUM> can be deposited in any suitable manner. In some embodiments, for example, the thick film material <NUM> can be deposited by the printer <NUM> or other device using an "S" pattern fill from a center of the thick film resistor <NUM> being formed, where a width of the pattern depends on the size of the thick film resistor <NUM> being formed. This type of deposition pattern may help to reduce or prevent the formation of a large lip at a beginning edge of the deposited thick film material <NUM>. Note, however, that the modified thick film material <NUM> can be deposited in any other suitable manner.

In the curing operation <NUM>, the modified thick film material <NUM> that has been deposited onto the structure <NUM>' is cured. In this example, a heater <NUM> is used during the curing operation <NUM> to heat the structure <NUM>' and the thick film material <NUM> on the structure <NUM>' in order to cure the thick film material <NUM>. The temperature of the curing operation <NUM> and the time needed for the curing operation <NUM> can vary based on a number of factors, such as the composition of the modified thick film material <NUM> and the shape or thickness of the deposited thick film material <NUM>. In general, the temperature of the curing operation <NUM> may be about <NUM>° C or lower or about <NUM>° C or lower. As a specific example, the curing operation <NUM> may involve heating the structure <NUM>' and the thick film material <NUM> to a temperature of about <NUM>° C for about five hours or to a temperature of about <NUM>° C for about thirty minutes. The ability to cure the modified thick film material <NUM> at relatively low temperatures enables the use of various plastic substrates <NUM> or other components or materials in the structure <NUM>' that cannot withstand the elevated temperatures used in standard sintering operations or other high-temperature operations (which can often involve temperatures of <NUM>° C, <NUM>° C, <NUM>° C, or even more). Thus, the operational flow <NUM> enables the manufacture of thick film resistors <NUM> having high sheet resistances without requiring high-temperature sintering operations.

Ideally, the dielectric material added to the carbon-based ink or other carbon-based thick film material during the mixing operation <NUM> to produce the modified thick film material <NUM> is heat-stable. For example, titanates such as barium strontium titanate are heat-stable compounds, meaning the compounds do not decompose into their constituent elements (at least within the temperature range experienced by the modified thick film material <NUM> during manufacture and use of the thick film resistor <NUM>). Assuming a base (unmodified) carbon-based ink or other carbon-based thick film material is heat-stable itself, the modified thick film material <NUM> has a higher resistance and is also heat-stable. The heater <NUM> represents any suitable structure configured to increase the temperature of a deposited thick film material <NUM> in order to cure the thick film material <NUM>. For instance, in a larger manufacturing setting or other setting, the heater <NUM> may represent a large oven. In a smaller setting, the heater <NUM> may represent a smaller oven or even a device such as a hot plate.

Once the curing operation <NUM> is completed, any additional processing operations <NUM> may be performed to complete the fabrication of the thick film resistor <NUM> (if needed) or to complete the fabrication of a circuit, device, or system that includes the thick film resistor <NUM>. For example, the thick film resistor <NUM> may be etched to have a desired shape or final resistance value. In some embodiments, for instance, the thick film resistor <NUM> can be placed into a fluoro-etch bath at about <NUM>° C for about thirty seconds up to several minutes. The thick film resistor <NUM> or other components can also be cleaned, such as by using isopropyl alcohol or methanol. In addition, some amount of power (such as about <NUM> W to about <NUM> W) can be applied across the thick film resistor <NUM> once fabrication is completed to help prevent subsequent changes to the resistance of the thick film resistor <NUM>.

At some point during the operational flow <NUM> in <FIG>, one or more steps may need to be taken to reduce or prevent oxidation of the exposed surfaces of the conductive traces <NUM> and <NUM>. For example, when copper traces are used as the conductive traces <NUM> and <NUM> in the circuit <NUM>, copper oxide may form on the exposed surfaces of the conductive traces <NUM> and <NUM>. Copper oxide can form at relatively low temperatures, and the presence of copper oxide on the conductive traces <NUM> and <NUM> can lead to the formation of an electrically-insulative interface between the conductive traces <NUM> and <NUM> and the thick film resistor <NUM> to be formed. Various techniques may be used here to reduce or prevent the formation of oxides or other insulative material on the conductive traces <NUM> and <NUM>. As examples, electroless nickel/immersion gold (ENIG) surface plating can be used on the conductive traces <NUM> and <NUM>, or an encapsulant/epoxy/sealant can be placed on the conductive traces <NUM> and <NUM> to prevent oxygen absorption. As another example, a graphene-based ink can be mixed with the dielectric material to form the modified thick film material <NUM> since graphene is essentially a two-dimensional arrangement of carbon atoms and can reduce or prevent oxide growth. As yet another example, sodium borohydride can be added to the modified thick film material <NUM> to reduce or prevent the formation of oxide. As still another example, the thick film resistor <NUM> can be cured or baked in a vacuum oven or other oxygen-free environment. It should be noted that curing/baking typically causes a small but predictable change in the resistance of the thick film resistor <NUM>, which can be taken into account when fabricating the thick film resistor <NUM>. Of course, any other suitable material selections or techniques may be used to inhibit or avoid the formation of oxide on the conductive traces <NUM> and <NUM>.

Thick film resistors <NUM> manufactured in this manner can have various advantages over standard thick film resistors. For example, by allowing titanate or other dielectric material to be mixed with a thick film material, the resistance or conductivity of the modified thick film material <NUM> can be precisely controlled prior to deposition. Also, the modified thick film material <NUM> can have a more uniform composition, enabling more consistent fabrication of thick film resistors <NUM>. Further, by reducing or minimizing the amount of titanate or other dielectric material in the modified thick film material <NUM>, higher sheet resistances can be obtained while maintaining high fusing currents in the thick film resistors <NUM> and while maintaining high stability of the thick film resistors <NUM> over temperature. As noted above, for instance, in some embodiments, thick film resistors <NUM> may handle up to about <NUM> mA of current and/or up to about <NUM> W or about <NUM> W of power without fusing. In addition, in some embodiments, the thick film resistors <NUM> may have reduced or minimal porosity compared to other thick film resistors. This can help to provide improved or maximum stability of the thick film resistors <NUM> under changing conditions (such as changing humidity or thermal conditions). Finally, the thick film resistors <NUM> may have resistances that are substantially stable at room temperatures, meaning the resistances of the thick film resistors <NUM> remain substantially constant over time at room temperatures.

The operational flow <NUM> shown in <FIG> may be useful in a number of circumstances. For example, the operational flow <NUM> may be used in large manufacturing settings to manufacture thick film resistors <NUM> in various circuits, devices, or systems. As a particular example, the operational flow <NUM> may be used to support large additive manufacturing processes in which 3D printers or other devices fabricate thick film resistors <NUM> of various configurations in various structures. As another example, the operational flow <NUM> may be used in research and development facilities, laboratories, or other locations to fabricate numerous prototypes or test devices that incorporate thick film resistors <NUM>. The modifiable resistances and flexible geometries of the thick film resistors <NUM> enable the thick film resistors <NUM> to be incorporated quickly into many different designs.

Although <FIG> illustrates one example of an operational flow <NUM> for forming thick film resistors <NUM> having customizable resistances, various changes may be made to <FIG>. For example, the specific equipment shown as being used in the mixing, deposition, and curing operations <NUM>, <NUM>, and <NUM> are examples only. Any suitable equipment can be used to perform each of the operations <NUM>, <NUM>, and <NUM>. Also, the various additional operations <NUM> can be performed as needed or desired in order to fabricate thick film resistors <NUM>, and the additional operations <NUM> can vary based (among other things) on the materials being used to fabricate the thick film resistors <NUM> and/or the materials in the structure <NUM>' on which the thick film resistors <NUM> are being formed.

<FIG> illustrates an example method <NUM> for forming a thick film resistor having a customizable resistance according to this disclosure. For ease of explanation, the method <NUM> shown in <FIG> is described as being used to manufacture the thick film resistor <NUM> of the example circuit <NUM> shown in <FIG> using the equipment included in the operational flow <NUM> shown in <FIG>. However, the method <NUM> shown in <FIG> may be used to form any suitable thick film resistors in any suitable circuits, devices, or systems and may involve the use of any suitable equipment for various operations.

As shown in <FIG>, a thick film material is blended with a dielectric material to form a modified thick film material at step <NUM>. This may include, for example, blending a carbon-based ink or other carbon-based thick film material with barium titanate, strontium titanate, barium strontium titanate, or other dielectric material. The blending can occur using a mixer <NUM> that is designed to help ensure an adequate distribution of the dielectric material within the carbon-based conductive material. The amount of dielectric material added to the carbon-based ink or other carbon-based thick film material can be based on the desired resistance of the modified thick film material <NUM> being produced. In some embodiments, for example, the amount of dielectric material added to the carbon-based ink or other carbon-based thick film material may be limited to a maximum of about <NUM>% to about <NUM>% by weight of the modified thick film material <NUM>.

The modified thick film material is deposited onto a structure in a desired geometry at step <NUM>. This may include, for example, depositing the modified carbon-based thick film material onto conductive traces <NUM> and <NUM> of a structure <NUM>' using a printer <NUM> or other deposition system. As noted above, the geometry of the thick film resistor <NUM> being fabricated can vary as needed, such as based on the desired application and the available space for the thick film resistor <NUM> being fabricated. Note that while the modified thick film material <NUM> is described here as being deposited in a geometry during the fabrication of a thick film resistor <NUM>, this step may involve the deposition of the modified thick film material in multiple areas (using the same geometry or different geometries) during the fabrication of multiple thick film resistors <NUM>. Also note that this step may occur repeatedly for the same thick film resistor <NUM> if the modified thick film material <NUM> is being deposited in multiple layers to form the thick film resistor <NUM>.

The deposited thick film material is cured on the structure in a (relatively) low-temperature environment at step <NUM>. This may include, for example, placing the structure <NUM>' with the deposited thick film material <NUM> into the heater <NUM>. The curing strengthens or hardens the deposited thick film material <NUM>, ideally while most or all of the deposited thick film material <NUM> remains in the desired shape on the structure <NUM>'. Example curing temperatures and curing times are provided above and generally do not exceed about <NUM>° C in temperature. As noted above, this is significantly lower that other processes involving high-temperature sintering operations or other high-temperature operations that can easily exceed <NUM>° C, <NUM>° C, or even <NUM>° C in temperature. The ability to cure the deposited thick film material <NUM> at lower temperatures enables the use of plastics or other materials that cannot withstand the elevated temperatures used in standard sintering operations or other high-temperature operations.

Any additional processing operations for forming a thick film resistor are performed at step <NUM>. This may include, for example, etching the deposited thick film material <NUM> so that a final desired resistance value is obtained for the thick film resistor <NUM>. This may also include cleaning the thick film resistor <NUM> or other components of the structure <NUM>'. In addition, this may include applying power (such as about <NUM> W to about <NUM> W) across the thick film resistor <NUM> to help prevent subsequent changes to the resistance of the thick film resistor <NUM> (which occurs in a process that may be referred to as a "bum-in" process).

Fabrication of a desired structure is completed at step <NUM>. This may include, for example, forming one or more protective layers of material or additional electrical components over the thick film resistor <NUM> and the conductive traces <NUM> and <NUM>. This may also include electrically coupling the conductive traces <NUM> and <NUM> to other circuit components to incorporate the thick film resistor <NUM> into a larger circuit. Of course, the thick film resistor <NUM> can be used in any suitable manner, and the operations performed here can vary widely based on how the thick film resistor <NUM> is to be used.

Although <FIG> illustrates one example of a method <NUM> for forming a thick film resistor having a customizable resistance, various changes may be made to <FIG>. For example, while shown as a series of steps, various steps in <FIG> may overlap, occur in parallel, occur in a different order, or occur any number of times. Also, various additional operations may occur at any points in the method <NUM> in order to obtain certain results from the overall process. For instance, one or more operations may occur at some point during the process to help reduce or prevent oxide formation on the conductive traces <NUM> and <NUM>, such as by using the various techniques that are described above.

Claim 1:
A method (<NUM>) comprising:
obtaining (<NUM>) a modified carbon-based thick film material that comprises a carbon-based thick film material blended with a dielectric material comprising a titanate;
depositing (<NUM>) the modified carbon-based thick film material onto a structure;
curing (<NUM>) the deposited modified carbon-based thick film material on the structure at a temperature that does not exceed about <NUM>° C; and
processing (<NUM>) the cured deposited modified carbon-based thick film material to form a thick film resistor (<NUM>);
wherein an amount of the titanate blended with the carbon-based thick film material does not exceed about <NUM>% by weight of the modified carbon-based thick film material;
wherein the modified carbon-based thick film material is a modified carbon-based ink;
wherein obtaining the modified carbon-based thick film material comprises blending the dielectric material comprising the titanate with a carbon-based ink to form the modified carbon-based ink;
wherein depositing the modified carbon-based thick film material comprises printing; and
wherein the modified carbon-based ink has a resistivity that is at least double a resistivity of the carbon-based ink.