High-power thick-film chip resistor

Abstract

The invention relates to the technical field of resistors, and particularly discloses a high-power thick-film chip resistor which comprises a ceramic substrate, a resistance layer, electrodes and a protection layer, the resistance layer is printed by resistance paste and sintered on the ceramic substrate, the electrodes comprise three layers of structures and cover the two ends of the ceramic substrate, a heat dissipation structure is arranged in the resistance layer, and the protection layer is arranged in the heat dissipation structure. The electrode structure comprises an inner layer, a middle layer and an outer layer, the inner layer is in contact with two ends of the ceramic substrate and the resistive layer and is sintered on the ceramic substrate and the resistive layer, the middle layer is electroplated on the inner layer, the outer layer is electroplated on the middle layer, the protective layer comprises a first-layer structure and a second-layer structure, the first-layer structure covers the resistive layer, and the second-layer structure covers the resistive layer. The second-layer structure covers the second-layer structure and is an insulating layer; the thick film chip resistor is welded on the circuit board through the electrodes, the heat dissipation structure is arranged on the resistance layer, and the plurality of heat dissipation fins are arranged in the ceramic substrate, so that the heat dissipation efficiency of the resistor is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resistors, in particular to a high-power thick-film wafer resistor. BACKGROUND

[0002] The global anti-sulfur chip resistor market has maintained stable growth in the past few years and is expected to continue to expand in the coming years. Through technological innovation and product upgrading, the performance and stability of the resistor are improved, and the production cost is also reduced, thereby helping to reduce the cost of the resistor. Anti-sulfur chip resistors are widely used in electronic equipment, communication equipment, industrial automation and other fields. The demand for anti-sulfur chip resistors is growing rapidly. The rapid development of the global electronics industry and the popularity of emerging technologies will continue to drive the demand for anti-sulfur chip resistors, especially in the fields of new energy vehicles, smart grids and high-end equipment manufacturing. The market demand will be more vigorous. In the field of anti-sulfur resistors, it is urgent to solve the problem of carrying higher power in a unit volume while efficiently dissipating heat to avoid thermal failure.

[0003] The Chinese patent document with the authorization announcement number CN214175794U discloses a thick-film wafer resistor, which comprises a resistor body, a wafer body, an anti-sulfur layer, an edge electrode layer and a ceramic substrate. The bottom of the wafer body is provided with lower electrodes on both sides. The top of the wafer body is provided with upper electrodes on both sides. The outer side of the upper electrode and the lower electrode is provided with an anti-sulfur layer. The wafer body is provided with an edge electrode layer on both sides. One side of the edge electrode layer is provided with a second protective layer. The outer layer of the second protective layer is provided with a first protective layer. The upper electrodes on the top of the wafer body are provided with a ceramic substrate. The top of the ceramic substrate is provided with a glass fiber layer. The top of the glass fiber layer is provided with a resin layer. The utility model protects the ceramic substrate of the resistor by the cooperation of the glass fiber layer and the resin layer, avoids the damage of the ceramic substrate caused by external factors, prolongs the service life of the ceramic substrate, and ensures the normal and stable operation of the thick-film wafer resistor.

[0004] In the above technical solution, the first protective layer and the second protective layer are used in cooperation, the side surfaces of the first protective layer and the second protective layer are in contact with the side surface of the resin layer, the first protective layer is arranged outside the second protective layer, and the thickness values of the first protective layer and the second protective layer are the same. When the resistor is used, the resistor is given double protection, the protection effect of the protective layer is improved, the device has practicality, and the reliability of the device is improved. However, it is difficult to effectively manage the heat of the thick-film resistor. SUMMARY

[0005] The present application provides a high-power thick-film wafer resistor, which aims to solve the problem of low heat dissipation efficiency of the thick-film resistor in the related art.

[0006] The application discloses a high-power thick-film chip resistor, which comprises a ceramic substrate, a resistor layer, electrodes and a protective layer, the resistor layer is printed and sintered on the ceramic substrate by a resistor paste, the electrodes comprise a three-layer structure and cover two ends of the ceramic substrate, a heat dissipation structure is arranged in the resistor layer, the electrode structure comprises an inner layer, a middle layer and an outer layer, the inner layer is in contact with and sintered on the ceramic substrate and the resistor layer, the middle layer is electroplated on the inner layer, and the outer layer is electroplated on the middle layer, the protective layer comprises a one-layer structure and a two-layer structure, the one-layer structure covers the resistor layer, and the two-layer structure covers the two-layer structure and is an insulating layer, the resistor layer adopts a composition gradient change, for example, Cr-Si is changed from high resistance to low resistance, and a plurality of mounting grooves are formed in the ceramic substrate, and fins are arranged in the mounting grooves.

[0007] Effects of the application are as follows: the thick-film chip resistor has excellent mechanical strength, electrical insulation, high thermal conductivity and good high-temperature stability when in use, the resistor paste is accurately printed between the electrodes of the ceramic substrate by a screen printing process to form a required resistance pattern, target resistance values can be obtained by accurately controlling the paste composition, printing thickness and sintering process, the fragile resistor layer is protected from mechanical damage by the protective layer, the thick-film chip resistor is welded on a circuit board by the electrodes, the heat dissipation efficiency of the resistor is improved by arranging the heat dissipation structure on the resistor layer and placing a plurality of fins in the ceramic substrate, and the resistor layer adopts a composition gradient change to disperse pulse current impact.

[0008] Preferably, a plurality of copper strips are arranged on the resistor layer at intervals, and each copper strip is connected with a copper sheet, and the copper sheets are arranged at intervals; when the copper strips are connected with the copper sheets, the heat dissipation efficiency of the resistor can be greatly improved, the copper strips are arranged at intervals to avoid short circuit caused by contact between the copper strips, the size of the copper strip is adjusted and the conductivity is calculated, the size of the resistor layer can be controlled when the copper strip is arranged on the resistor layer, the copper strip, the resistor layer and the ceramic substrate can be sintered together when the copper strip is installed, and the resistor layer covering the copper strip can be removed after sintering.

[0009] Preferably, micron-level heat dissipation fins or grooves are designed on the surface of the resistor to increase the heat dissipation surface area; the heat dissipation area of the resistor can be increased by arranging a plurality of heat dissipation fins on the surface of the resistor, so that the heat dissipation efficiency of the resistor is improved, and meanwhile, the heat dissipation fins can cooperate with the copper strips, and the copper strips are arranged at gaps of the heat dissipation fins to improve the heat dissipation efficiency of the resistor.

[0010] Preferably, the ceramic substrate is made of aluminum nitride ceramic to increase the thermal conductivity; the thermal conductivity of the aluminum nitride ceramic is 8-10 times that of ordinary aluminum oxide ceramic, so that the thermal conductivity of the ceramic substrate can be significantly improved.

[0011] Preferably, the two ends of the heat dissipation fin abut in the mounting groove, and the thickness of the heat dissipation fin is less than the height of the mounting groove; by opening the mounting groove on the ceramic substrate and arranging the copper sheet in the mounting groove, the heat dissipation efficiency of the ceramic substrate can be further improved; when the ceramic substrate is heated, the ceramic substrate has a small deformation due to heating, and the heat dissipation fin deforms due to thermal expansion and contraction; since the thickness of the heat dissipation fin is less than the height of the mounting groove, the copper sheet can be bent and attached to the ceramic substrate when the copper sheet deforms; after the ceramic substrate cools down, the heat dissipation fin resets and is separated from the ceramic substrate.

[0012] Preferably, the slurry is composed of ruthenium dioxide, lead-free borosilicate and an organic carrier; the ruthenium dioxide serves as a conductive phase and has a particle size controlled in a range of 0.1-1.0 μm; the lead-free borosilicate serves as a glass phase; and the organic carrier includes terpineol, ethyl cellulose and dibutyl phthalate; the terpineol is a high-boiling solvent and has a content of 40%-60%, and influences the drying shrinkage; the ethyl cellulose provides a shear thinning property and determines the leveling property; and the dibutyl phthalate is a plasticizer and is added in an amount of 2%-5% to inhibit printing web marks.

[0013] Preferably, the inner layer material is a palladium-silver alloy and is sintered into a porous structure to form a low-resistance connection with the resistance layer, thereby ensuring efficient transmission of current; the sintering forms a chemical bond with the ceramic substrate to resist mechanical stress; the middle layer structure is electroplated nickel, and the thickness of the nickel is 2-5 μm; the dense structure of the nickel blocks diffusion of silver ions to solder; the dissolution rate of the nickel in solder is extremely low; the thermal expansion coefficient of the nickel (13 ppm / ℃) is between that of the ceramic substrate (7 ppm / ℃) and that of solder (25 ppm / ℃), thereby buffering stress; and the outer layer structure is a tin-lead alloy, and the thickness of the tin-lead alloy is 3-8 μm; tin instantaneously diffuses in molten solder to form a firm intermetallic compound, thereby covering the nickel layer and preventing oxidation of the nickel layer.

[0014] Preferably, the inner layer material is a palladium-silver alloy and is sintered into a porous structure to form a low-resistance connection with the resistance layer, thereby ensuring efficient transmission of current; the sintering forms a chemical bond with the ceramic substrate to resist mechanical stress; the middle layer structure is electroplated nickel, and the thickness of the nickel is 2-5 μm; the dense structure of the nickel blocks diffusion of silver ions to solder; the dissolution rate of the nickel in solder is extremely low; the thermal expansion coefficient of the nickel (13 ppm / ℃) is between that of the ceramic substrate (7 ppm / ℃) and that of solder (25 ppm / ℃), thereby buffering stress; and the outer layer structure is a tin-lead alloy, and the thickness of the tin-lead alloy is 3-8 μm; tin instantaneously diffuses in molten solder to form a firm intermetallic compound, thereby covering the nickel layer and preventing oxidation of the nickel layer.

[0015] By using the above technical solution, the application has the following beneficial effects:

[0016] 1. Thick film wafer resistors, during use, possess excellent mechanical strength, good electrical insulation, high thermal conductivity, and outstanding high-temperature stability thanks to the resistor's supporting framework. The resistive paste is precisely printed between the two electrodes of the ceramic substrate using screen printing technology, thereby forming the required resistor pattern.

[0017] 2. By precisely controlling the paste composition, printing thickness, and sintering process, the target resistance value can be obtained; a protective layer is used to protect the fragile resistive layer from mechanical damage; electrodes are used to solder the thick film wafer resistor onto the circuit board; a heat dissipation structure is set on the resistive layer, and multiple heat sinks are placed inside the ceramic substrate to improve the heat dissipation efficiency of the resistor; the resistive layer adopts a composition gradient change method to disperse the pulse current impact. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0019] Figure 2 This is a schematic diagram of the exploded structure of the present invention.

[0020] Figure 3 This is a schematic diagram of the structure of the copper strip and copper sheet of the present invention.

[0021] Figure 4 This is a schematic diagram of the mounting slot and heat sink of the present invention.

[0022] Figure label:

[0023] 1. Ceramic substrate; 11. Mounting groove; 12. Heat sink; 2. Resistor layer; 21. Copper strip; 22. Copper sheet; 3. Electrode; 31. Inner layer; 32. Middle layer; 33. Outer layer; 4. Protective layer; 41. Single-layer structure; 42. Two-layer structure. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] like Figures 1-4As shown, a high-power thick-film chip resistor includes a ceramic substrate 1, a resistance layer 2, electrodes 3 and a protective layer 4, the resistance layer 2 is printed and sintered on the ceramic substrate 1 by resistance paste, the electrodes 3 include a three-layer structure and cover both ends of the ceramic substrate, a heat dissipation structure is arranged in the resistance layer 2, the electrode 3 structure includes an inner layer 31, a middle layer 32 and an outer layer 33, the inner layer 31 is in contact with and sintered on both ends of the ceramic substrate and the resistance layer 2, the middle layer 32 is electroplated on the inner layer 31, and the outer layer 33 is electroplated on the middle layer 32, the protective layer 4 includes a one-layer structure 41 and a two-layer structure, the one-layer structure 41 covers the resistance layer 2, and the two-layer structure covers the two-layer structure and is an insulating layer, the resistance layer 2 adopts a composition gradient change, for example, Cr-Si transitions from high resistance to low resistance, and a plurality of mounting grooves 11 are arranged in the ceramic substrate 1, and a plurality of heat dissipation fins are arranged in the mounting grooves 11.

[0026] In use, the thick-film chip resistor provides excellent mechanical strength, electrical insulation, high thermal conductivity and good high-temperature stability through the support framework of the resistor, the resistance paste is accurately printed between the electrodes 3 of the ceramic substrate by a screen printing process to form a required resistance pattern, the target resistance value can be obtained by accurately controlling the composition, printing thickness and sintering process of the paste, the fragile resistance layer 2 is protected from mechanical damage by the protective layer 4, the thick-film chip resistor is welded on the circuit board by the electrodes 3, the heat dissipation efficiency of the resistor is increased by arranging the heat dissipation structure on the resistance layer 2 and placing a plurality of heat dissipation fins in the ceramic substrate 1, and the pulse current impact is dispersed by the resistance layer 2 adopting a composition gradient change.

[0027] A plurality of copper strips 21 are arranged on the resistance layer 2 at intervals, and each copper strip 21 is circumscribed by a copper sheet 22, and a plurality of copper sheets 22 are arranged at intervals; when the copper strips 21 are externally connected to the copper sheets 22, the heat dissipation efficiency of the resistance is greatly increased, and when the plurality of copper strips 21 are arranged at intervals, the copper strips 21 are prevented from contacting to form a short circuit, the size of the copper strip 21 is adjusted and its conductivity is calculated, the size of the resistance layer 2 is controllable when the copper strip 21 is arranged on the resistance layer 2, the copper strip 21, the resistance layer 2 and the ceramic substrate can be sintered together when the copper strip 21 is installed, and the resistance layer 2 covering the copper strip 21 can be removed after sintering is completed.

[0028] The surface of the resistance is designed with micron-level heat dissipation fins or grooves to increase the heat dissipation surface area; the heat dissipation area of the resistance is increased by arranging a plurality of heat dissipation fins on the surface of the resistance, thereby improving the heat dissipation efficiency of the resistance, and the heat dissipation fins can cooperate with the copper strips 21, and the copper strips 21 are placed at the gaps of the heat dissipation fins to increase the heat dissipation efficiency of the resistance.

[0029] The ceramic substrate material is aluminum nitride ceramic to increase its thermal conductivity; by using aluminum nitride ceramic, its thermal conductivity is ≥170 W / mK, which is 8-10 times that of ordinary alumina ceramic, and the thermal conductivity of the ceramic substrate can be significantly increased.

[0030] The two ends of the heat sink abut in the mounting groove 11, and the thickness of the heat sink is less than the height of the mounting groove 11; by opening the mounting groove 11 on the ceramic substrate, the copper sheet 22 is arranged in the mounting groove 11, which can further increase the heat dissipation efficiency of the ceramic substrate; when the ceramic substrate is heated, the ceramic is less deformed by heat, and the heat sink is deformed due to thermal expansion and contraction; since the thickness of the heat sink is less than the height of the mounting groove 11, when the copper sheet 22 is deformed, it can be bent and attached to the ceramic substrate; when the ceramic substrate cools down, the heat sink resets and separates from the ceramic substrate.

[0031] The slurry is composed of ruthenium dioxide, lead-free borosilicate and organic carrier; ruthenium dioxide is used as the conductive phase, and the particle size needs to be controlled in the range of 0.1-1.0 μm; lead-free borosilicate is used as the glass phase; the organic carrier includes terpineol, ethyl cellulose and dibutyl phthalate; terpineol is a high-boiling solvent with a gradient evaporation rate, and its content is 40%-60%, which affects the drying shrinkage; ethyl cellulose provides shear thinning properties and determines the leveling property; dibutyl phthalate is a plasticizer that inhibits printing mesh marks, and its addition amount is 2%-5%.

[0032] The inner layer 31 is made of palladium-silver alloy and sintered into a porous structure, which forms a low-resistance connection with the resistance layer 2 to ensure efficient transmission of current; during sintering, a chemical bond is formed between the ceramic substrate and the inner layer 31 to resist mechanical stress; the middle layer 32 is made of electroplated nickel, and the thickness of the nickel is 2-5 μm; the dense structure of nickel blocks the diffusion of silver ions into the solder; the dissolution rate of nickel in solder is extremely low; the thermal expansion coefficient of nickel (13 ppm / ℃) is between that of the ceramic substrate (7 ppm / ℃) and the solder (25 ppm / ℃), which buffers the stress; the outer layer 33 is made of tin-lead alloy, and the thickness is 3-8 μm; tin instantaneously diffuses in the molten solder to form a firm intermetallic compound that covers the nickel layer and prevents it from oxidizing.

[0033] The first layer structure 41 is a glass layer that covers the resistance layer 2 after resistance adjustment; it is also printed by silk screen and sintered to protect the fragile resistance layer 2 from mechanical damage, isolate moisture, pollutants, chemicals, etc., and improve long-term stability; the second layer structure is epoxy resin; the epoxy resin is a high-crosslinking-density resin to reduce the gap between molecular chains; it is printed or coated on the first protective layer 4 and then cured to provide stronger mechanical protection (scratch resistance) and better environmental sealing to prevent accidental contact of external conductors with the resistance layer 2.

[0034] Working principle:

[0035] In use, the thick-film chip resistor has excellent mechanical strength, good electrical insulation, high thermal conductivity and excellent high-temperature stability due to the support skeleton of the resistor; the resistor paste is accurately printed between the two electrodes 3 of the ceramic substrate by the screen printing process, thereby forming the required resistance pattern; the target resistance value can be obtained by accurately controlling the paste composition, printing thickness and sintering process; the fragile resistance layer 2 is protected by the protective layer 4 to prevent mechanical damage; the thick-film chip resistor is welded on the circuit board by the electrodes 3; the heat dissipation structure is arranged on the resistance layer 2, and multiple heat dissipation fins are placed inside the ceramic substrate 1 to improve the heat dissipation efficiency of the resistor; the resistance layer 2 adopts a composition gradient change to disperse the pulse current impact.

[0036] Although the embodiments of the present application have been shown and described above, it should be understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A high-power thick-film wafer resistor, comprising a ceramic substrate (1), a resistive layer (2), an electrode (3), and a protective layer (4), wherein the resistive layer (2) is printed and sintered on the ceramic substrate (1) by resistive paste, and the electrode (3) comprises a three-layer structure and covers both ends of the ceramic substrate, characterized in that: The resistive layer (2) is provided with a heat dissipation structure. The electrode (3) structure includes an inner layer (31), a middle layer (32) and an outer layer (33). The inner layer (31) is in contact with the ceramic substrate and the two ends of the resistive layer (2) and is sintered on the ceramic substrate and the resistive layer (2). The middle layer (32) is electroplated on the inner layer (31), and the outer layer (33) is electroplated on the middle layer (32). The protective layer (4) includes a single-layer structure (41) and a double-layer structure. The single-layer structure (41) covers the resistive layer (2), and the double-layer structure covers the double-layer structure and is an insulating layer. The resistive layer (2) adopts a composition gradient change. The ceramic substrate (1) has multiple mounting slots (11) inside, and heat sinks (22) are provided in the mounting slots (11).

2. The high-power thick-film wafer resistor according to claim 1, characterized in that, Multiple copper strips (21) are spaced apart on the resistive layer (2), and each copper strip (21) is connected to a copper sheet (22), with the multiple copper sheets (22) spaced apart.

3. The high-power thick-film wafer resistor according to claim 1, characterized in that, The surface of the resistor is designed with micron-level heat dissipation fins or grooves to increase the heat dissipation surface area.

4. The high-power thick-film wafer resistor according to claim 1, characterized in that, The ceramic substrate is made of aluminum nitride ceramic to increase its thermal conductivity.

5. The high-power thick-film wafer resistor according to claim 1, characterized in that, The two ends of the heat sink (22) abut against the mounting groove (11), and the thickness of the heat sink (22) is less than the height of the mounting groove (11).

6. The high-power thick-film wafer resistor according to claim 5, characterized in that, The slurry is composed of ruthenium dioxide, lead-free borosilicate, and an organic carrier.

7. The high-power thick-film wafer resistor according to any one of claims 1-6, characterized in that, The inner layer (31) is made of palladium-silver alloy and sintered into a porous structure. The middle layer (32) is electroplated nickel with a thickness of 2-5 μm. The outer layer (33) is made of tin-lead alloy with a thickness of 3-8 μm.

8. The high-power thick-film wafer resistor according to claim 1, characterized in that, The first layer (41) is a glass layer, and the second layer is an epoxy resin, wherein the epoxy resin is a high crosslinking density resin to reduce the gap between molecular chains.

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