A thin film chip resistor and a method for preparing the same

Abstract

The present invention provides a thin film chip resistor and a preparation method thereof, and relates to the technical field of resistors. The thin film chip resistor provided by the present invention comprises a substrate, a diamond substrate, a resistance layer, a diamond protective layer, an outer protective layer, a lead electrode and a terminal welding layer, wherein the resistance layer is arranged between the diamond substrate and the diamond protective layer. The present invention introduces a diamond substrate and a diamond protective layer on the basis of the existing thin film resistor, and arranges the resistance layer between the diamond substrate and the diamond protective layer, thereby improving the heat dissipation capacity and resistance power level of the resistance layer in the chip resistor, and avoiding the occurrence of electrochemical corrosion.

Description

Technical Field

[0001] The present invention relates to the technical field of resistors, and in particular to a thin film chip resistor and a preparation method thereof. Background Art

[0002] Existing conventional thin film resistor protection structures, such as Fig.21 As shown, epoxy resin is directly coated on the resistor layer using thick film screen printing technology as a protective layer. The advantages are single material and simple structure, and the disadvantages are that epoxy resin has certain water permeability and water absorption properties, and water vapor is easy to invade under high temperature and high humidity environment. If the product is powered on at the same time, electrical corrosion will occur; and the epoxy resin has poor thermal conductivity, and the protective layer formed after covering is not conducive to the heat dissipation of the product; in addition, there is a small gap between the epoxy resin and its filler, which may allow environmental gas to enter. Under long-term action, the surface of the resistor layer will be oxidized, nitrided, and even corroded, resulting in changes in resistance value.

[0003] High stability thin film resistor protection structure, such as Fig. 22 As shown, a silicon oxide protective layer is usually deposited on the surface of the resistor layer by CVD process, and then a photosensitive protective layer is coated on the silicon oxide surface. The protection covering the resistor layer is obtained by exposure and development, and then the uncovered part of the silicon oxide protective layer is removed by wet etching to obtain a silicon oxide protective layer that completely covers the resistor layer. Finally, epoxy resin is coated as an outer protective layer by thick film screen printing technology, so that the resistor layer is covered with aluminum oxide or silicon oxide protective layer above or below. Its advantage is that the water permeability and water absorption rate of silicon oxide are basically zero. Under the same high temperature and high humidity conditions, it can avoid corrosion caused by contact between water vapor and the resistor layer, so it has excellent high temperature and high humidity resistance. However, its disadvantages are also significant. Its silicon oxide protective layer has poor thermal conductivity, which is equivalent to forming a thermal barrier layer, resulting in reduced heat dissipation capacity of the resistor; and the production process is long, and it is necessary to introduce CVD process, yellow light lithography process, and wet etching process, involving many auxiliary materials, and complex structure and process. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the main purpose of the present invention is to provide a thin film chip resistor and a preparation method thereof, aiming to improve the heat dissipation capacity and resistance power level of the resistor layer in the chip resistor and avoid electrochemical corrosion.

[0005] To achieve the above objectives, in a first aspect, the present invention proposes a thin film chip resistor, comprising a substrate, a diamond substrate, a resistance layer, a diamond protective layer, an outer protective layer, a lead electrode and a terminal welding layer, wherein the resistance layer is arranged between the diamond substrate and the diamond protective layer.

[0006] In the technical solution of the present invention, on the basis of the existing thin film resistor, a diamond substrate and a diamond protective layer are introduced, and the resistance layer is arranged between the diamond substrate and the diamond protective layer. The thermal conductivity of diamond is about 2000W / m·K. When working, the heat generated by the resistance layer can be quickly conducted outward through the diamond substrate and the diamond protective layer, thereby improving the heat dissipation capacity of the resistance layer, thereby greatly improving the power of the thin film resistor.

[0007] In addition, diamond is impermeable and non-absorbent. When used as a substrate and protective layer, water vapor cannot penetrate, so that the resistor layer will not experience electrochemical corrosion, and the resistor can work stably for a long time in a high temperature and high humidity environment.

[0008] In addition, the present invention adopts a diamond protective layer, and laser can be used to cut and adjust the resistance of the resistor layer. During the cutting process, the laser can pass through the diamond protective layer without damage, and its air tightness will not be affected.

[0009] As a preferred embodiment of the thin film chip resistor of the present invention, the thickness of the diamond substrate is 1-50 μm, more preferably, the thickness of the diamond substrate is 20 μm; the thickness of the diamond protective layer is 1-10 μm, more preferably, the thickness of the diamond protective layer is 4 μm.

[0010] As a preferred embodiment of the thin film chip resistor of the present invention, the material of the substrate is alumina ceramic with a purity of >99%, and the Ra value of the substrate is 0.2-0.4 μm, and more preferably, the Ra value is 0.3 μm.

[0011] In a second aspect, the present invention also proposes a method for preparing a thin film chip resistor, using CVD deposition technology to prepare a diamond substrate and / or a diamond protective layer, and the CVD deposition technology includes at least one of hot filament (HFCVD) deposition, DC assisted plasma deposition, DC arc plasma jet (DAPCVD) deposition, microwave plasma (WMPCVD) deposition, and laser assisted (LACVD) deposition.

[0012] As a preferred embodiment of the method for preparing the thin film chip resistor of the present invention, a diamond substrate is prepared by microwave plasma deposition technology, including at least one of the following (a)-(c):

[0013] (a) CH4 / H2 is used as the gas source, and the volume ratio of CH4 and H2 is CH4:H2=(1-9):(91-99);

[0014] (b) microwave power is 10 kW to 15 kW;

[0015] (c) Gas pressure is 10-20 kPa.

[0016] In the technical solution of the present invention, a high-power WMPCVD process is used to deposit the diamond substrate, which can achieve rapid deposition of the diamond bottom layer.

[0017] As a preferred embodiment of the method for preparing the thin film chip resistor of the present invention, the volume ratio of CH4 and H2 is CH4:H2=5:95; the microwave power is 12.5kW; and the gas pressure is 15kPa.

[0018] As a preferred embodiment of the method for preparing the thin film chip resistor of the present invention, the diamond protective layer is prepared by microwave plasma deposition technology, including at least one of the following (d)-(f):

[0019] (d) using CH4 / Ar / H2 as the gas source, the volume ratio of CH4, Ar and H2 is CH4:Ar:H2=(1.5-3.5):(25-45):(52-72);

[0020] (e) microwave power is 500W-1000W;

[0021] (f) Gas pressure is 1-3 kPa.

[0022] Since the annealing temperature of the resistor layer is usually 300-600°C, if the temperature exceeds this range when depositing the diamond protective layer, it is easy to cause the resistor layer to have excessive temperature and high performance changes. Therefore, the low-temperature WMPCVD process is used when depositing the diamond protective layer in the technical solution of the present invention, which can reduce the substrate temperature during deposition and avoid performance variations caused by secondary heat treatment of the resistor layer.

[0023] As a preferred embodiment of the method for preparing the thin film chip resistor described in the present invention, the volume ratio of CH4, Ar and H2 is CH4:Ar:H2=2.5:35.5:62; the microwave power is 750W; and the gas pressure is 2kPa.

[0024] As a preferred embodiment of the method for preparing the thin film chip resistor of the present invention, the method for preparing the thin film chip resistor also includes a substrate pretreatment process, and the steps of the substrate pretreatment process are: placing the substrate in a mixed solution of anhydrous ethanol and diamond powder with a particle size of 0.05-0.15μm for ultrasonication.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) The technical solution of the present invention introduces a diamond substrate and a diamond protective layer on the basis of the existing thin film resistor, and sets the resistance layer between the diamond substrate and the diamond protective layer. The thermal conductivity of diamond is about 2000W / m·K. When working, the heat generated by the resistance layer can be quickly conducted outward through the diamond substrate and the diamond protective layer, thereby improving the heat dissipation capacity of the resistance layer, thereby increasing the power of the thin film resistor;

[0027] (2) Diamond is impermeable and non-absorbent. When used as a substrate and protective layer, water vapor cannot penetrate, so that the resistor layer will not suffer from electrochemical corrosion. The resistor can work stably for a long time in a high temperature and high humidity environment.

[0028] (3) The present invention uses a diamond protective layer, and laser can be used to cut and adjust the resistance of the resistor layer. During the cutting process, the laser can pass through the diamond protective layer without damaging it, and its airtightness will not be affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1-19 Schematic diagrams of structures corresponding to each step in the preparation process of the thin film chip resistor of the present invention, wherein each figure includes a front view (X-1) on the left and a shear surface schematic diagram (X-2) on the right;

[0030] Fig. 20 is a schematic diagram of a thin film chip resistor of the present invention;

[0031] Fig.21 A schematic diagram of an existing conventional thin film resistor protection structure in Comparative Example 1;

[0032] Fig. 22 A schematic diagram of an existing high-stability thin-film resistor protection structure in Comparative Example 2;

[0033] The figures are marked as follows: 1-substrate, 2-diamond substrate, 3-resistance layer, 4-diamond protective layer, 5-outer protective layer, 6-terminal welding layer, 7-lead electrode, 8-protective layer. DETAILED DESCRIPTION

[0034] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below through specific embodiments.

[0035] Example 1

[0036] The method for preparing the thin film chip resistor of this embodiment comprises the following steps:

[0037] S1, substrate pretreatment: the alumina ceramic substrate is placed in a mixture of anhydrous ethanol and diamond powder with a particle size of 0.05-0.15 μm and ultrasonicated for 15 minutes. Figure 1 As shown;

[0038] S2, depositing diamond substrate: using WMPCVD process to deposit diamond substrate on the front side of alumina ceramic substrate, using CH4 / H2 as gas source, CH4:H2=(1-9):(91-99); microwave power of 10kW-15kW; gas pressure of 10-20kPa, after treatment Figure 2 As shown;

[0039] S3, depositing a resistor layer: depositing a resistor layer on the surface of the diamond substrate layer by physical vapor deposition (PVD). The resistor layer is a binary or multi-element alloy such as Ni, Cr, Si, Cr, Al, and a Ta series alloy. Figure 3 As shown;

[0040] S4, electrode layer deposition: Based on S3, electrode layers are deposited on the front and back sides by PVD. The electrode layers are conductive metal layers such as Au, Ag, Cu, Al, etc., as well as adhesion enhancement layers at the bottom (usually metals and alloys such as Ti, TiW, nickel-chromium, etc.), and anti-oxidation passivation layers at the top (usually nickel-chromium alloy). After treatment, Figure 4 As shown;

[0041] S5, coating a photosensitive barrier layer: Based on S4, a photosensitive barrier layer is coated on the front and back surfaces. Figure 5 As shown;

[0042] S6, through exposure and development, remove part of the photosensitive barrier layer, and only retain the pattern designed as the electrode. Figure 6 As shown;

[0043] S7, using chemical etching to remove the electrode layer other than the photosensitive barrier layer, after treatment, Figure 7 As shown;

[0044] S8, a photosensitive barrier layer is coated on the entire front surface to completely cover the photosensitive barrier layer on the resistance layer and the electrode surface exposed after etching. Figure 8 As shown;

[0045] S9, through exposure and development, part of the photosensitive barrier layer is removed, and only the pattern of the part designed as the electrode and the resistor is retained. Fig. 9 As shown;

[0046] S10, chemical etching is used to remove the resistance layer other than the photosensitive barrier layer. Fig.10 As shown;

[0047] S11, remove all photosensitive barrier layers, and process as follows Fig.11 As shown;

[0048] S12, depositing a diamond protective layer, using WMPCVD process to deposit a diamond protective layer on the surface of the resistor and electrode, using CH4 / Ar / H2 as the gas source, the volume ratio of CH4, Ar and H2 is CH4:Ar:H2=(1.5-3.5):(25-45):(52-72); the microwave power is 500W-1000W; the gas pressure is 1-3kPa, and after treatment, Fig.12 As shown;

[0049] S13, coating a photosensitive barrier layer on the surface of the diamond protective layer, and treating Fig.13 As shown;

[0050] S14, by exposure and development, a part of the photosensitive barrier layer is removed, and only the pattern of the part designed as the diamond protection layer is retained. Fig.14 As shown;

[0051] S15, removing part of the diamond layer by dry etching, and only retaining the pattern of the part designed as the diamond protection layer. Fig.15 As shown;

[0052] S16, remove all photosensitive barrier layers, and process as follows Fig.16 As shown;

[0053] S17, using laser resistance trimming method, cut part of the resistance layer to achieve the target resistance value. Fig.17 As shown;

[0054] S18, coating a layer of epoxy resin protective layer on the surface of the diamond protective layer, and treating Fig.18 As shown;

[0055] S19, depositing nickel-chromium alloy, nickel, and tin layers on the electrode surface and end face in sequence as terminal welding layers, and after treatment, Fig.19 shown.

[0056] The thin film chip resistor of this embodiment is as follows Fig. 20 As shown, it comprises a substrate (1), a diamond substrate (2), a resistance layer (3), a diamond protective layer (4), an outer protective layer (5), an extraction electrode (7) and a terminal welding layer (6), wherein the resistance layer (3) is arranged between the diamond substrate (2) and the diamond protective layer (4), the thickness of the diamond substrate (2) is 1-50 μm, and the thickness of the diamond protective layer (4) is 1-10 μm; the material of the substrate (1) is alumina ceramic with a purity of >99%, and the Ra value of the substrate (1) is 0.2-0.4 μm.

[0057] Comparative Example 1

[0058] The thin film resistor protection structure of this comparative example is as follows Fig.21As shown, it comprises: a substrate (1), a resistance layer (3), an outer protective layer (5), a lead electrode (7) and a terminal welding layer (6).

[0059] Comparative Example 2

[0060] The thin film resistor protection structure of this comparative example is as follows Fig. 22 As shown, it comprises: a substrate (1), a resistance layer (3), a protective layer (8), an outer protective layer (5), an extraction electrode (7) and a terminal welding layer (6). The material of the protective layer (8) is aluminum oxide or silicon oxide.

[0061] The thin film chip resistor of Example 1 has the following advantages compared with Comparative Example 1 and Comparative Example 2:

[0062] 1. Since the thermal conductivity of diamond is about 2000W / m·K, the thermal conductivity of alumina ceramic is about 22W / m·K, the thermal conductivity of silicon dioxide is about 1.4-1.6W / m·K, and the thermal conductivity of epoxy resin is about 0.2-2.2W / m·K. The resistance layer of comparative example 1 mainly dissipates heat through the alumina ceramic substrate, and embodiment 1 adopts a diamond substrate and a protective layer, and the contact position increases the heat dissipation speed by nearly 100 times. The thermal conductivity of the silicon oxide protective layer of comparative example 2 is nearly 10 times lower than that of alumina ceramic, which is equivalent to forming a thermal barrier layer, and its heat dissipation capacity is worse than that of comparative example 1. The power of the thin film chip resistor of the embodiment can be increased by 20%-200% compared with comparative examples 1 and 2.

[0063] 2. The influence of the substrate and protective layer on water vapor transmission and absorption. Diamond, like silicon oxide, has the characteristics of being impermeable and non-absorbent. When used as a protective layer, water vapor cannot penetrate, and the resistance layer will not suffer from electrochemical corrosion. Therefore, the resistor products of Example 1 and Comparative Example 2 can work stably for a long time in a high temperature and high humidity environment. Comparative Example 1 uses epoxy resin as the outer protective layer alone. When working in a high temperature and high humidity environment, the resistance film is easily corroded.

[0064] 3. Comparative Example 1 uses epoxy resin as the outer protective layer. The epoxy resin itself and the coating process will produce fine pores; and there are fine gaps between the epoxy resin and its filler, which may allow ambient gas to enter. Under long-term action, the surface of the resistor film will be oxidized, nitrided, or even corroded, resulting in a change in resistance value. Example 1 uses diamond as the protective layer and substrate, and Comparative Example 2 uses silicon oxide or aluminum oxide product protective layer. After the protection is formed, the resistor film can be cut and adjusted with a laser. During the cutting process, the laser can pass through the diamond and silicon oxide protective layers without damage, and its airtightness is not affected.

[0065] In summary, the thin film chip resistor of Example 1 has the functions of simultaneously improving the heat dissipation capacity and resistance power level of the resistor layer and avoiding the occurrence of electrochemical corrosion.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A thin film chip resistor, characterized in that: It includes a substrate, a diamond substrate, a resistance layer, a diamond protective layer, an outer protective layer, an extraction electrode and a terminal welding layer, wherein the resistance layer is arranged between the diamond substrate and the diamond protective layer; the thickness of the diamond substrate is 20 μm; the material of the substrate is alumina ceramic with a purity of >99%, and the Ra value of the substrate is 0.2-0.4 μm; The preparation method of the thin film chip resistor is as follows: The diamond substrate is prepared by microwave plasma deposition technology, including the following (a)-(c): (a) CH4 / H2 is used as the gas source, and the volume ratio of CH4 and H2 is CH4:H2=(1-9):(91-99); (b) microwave power is 10 kW to 15 kW; (c) Gas pressure is 10-20 kPa; The diamond protective layer is prepared by microwave plasma deposition technology, including the following (d)-(f): (d) using CH4 / Ar / H2 as the gas source, the volume ratio of CH4, Ar and H2 is CH4:Ar:H2=(1.5-3.5):(25-45):(52-72); (e) microwave power is 500W-1000W; (f) Gas pressure is 1-3 kPa.

2. The thin film chip resistor according to claim 1, characterized in that: The thickness of the diamond protection layer is 1-10 μm.

3. The thin film chip resistor according to claim 2, characterized in that: The thickness of the diamond protection layer is 4 μm.

4. The thin film chip resistor according to claim 1, characterized in that: In (a)-(c), the volume ratio of CH4 and H2 is CH4:H2=5:95; the microwave power is 12.5kW; and the gas pressure is 15kPa.

5. The thin film chip resistor according to claim 1, characterized in that: In (d)-(f), the volume ratio of CH4, Ar and H2 is CH4:Ar:H2=2.5:35.5:62; the microwave power is 750W; and the gas pressure is 2kPa.

6. The thin film chip resistor according to any one of claims 4 to 5, characterized in that: The method for preparing the thin film chip resistor also includes a substrate pretreatment process, wherein the substrate pretreatment process comprises placing the substrate in a mixed solution of anhydrous ethanol and diamond powder with a particle size of 0.05-0.15 μm and performing ultrasonic treatment.

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