SMD (Surface Mount Device) zinc oxide varistor and production method thereof

Abstract

The invention discloses a surface-mounted zinc oxide varistor and a production method, and relates to the technical field of varistors, the surface-mounted zinc oxide varistor comprises a voltage-sensitive ceramic chip, the periphery of the voltage-sensitive ceramic chip is provided with a solder mask, and two sides of the voltage-sensitive ceramic chip are provided with electrodes. The preparation method comprises the following steps: preparing low-gradient zinc oxide powder; preparing powder, mixing and grinding the prepared powder, mixing the ground mixture with ZnO, grinding, adding glue, and spray-drying to obtain zinc oxide pressure-sensitive ceramic powder; pressing a green body, pre-discharging glue from the green body, then firing to form a pressure-sensitive ceramic chip, and then manufacturing electrodes: taking% silver paste, and respectively printing the electrodes at two ends of the pressure-sensitive ceramic chip in the length direction; after drying, sintering silver in a silver sintering furnace; and finally, taking the yellow UV photocuring ink corresponding to the K, respectively printing on two sides in the height direction, and performing UV photocuring to obtain a sample, the device adopts a fixed length, is convenient for PCB welding spot layout, is free of lead wires, is accurate and controllable in size, and is convenient for low-cost large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of varistors, in particular to a chip zinc oxide varistor and a production method thereof. Background Art

[0002] Currently, most lighting devices use LED lamp beads, which have relatively poor tolerance to surge impacts in the circuit and require surge protection. Due to the conductivity of the heat-dissipating aluminum substrate, it is not suitable for plug-in components. The surge protection varistors currently in use are all packaged in surface mount form to facilitate the mass production of LED lamp heads.

[0003] However, in the prior art, such as Chinese patents CN202211338129.4, CN201610472205.9, CN201510955379.6 and CN201010580937.2 disclose multilayer varistors and methods for manufacturing same, which adopt a multilayer ceramic capacitor process, using a tape casting machine for casting, printing internal electrodes, isostatic pressing, stacking and cutting, pre-drying, atmosphere sintering, electrode connection, nickel plating and tin plating and other processes. On the one hand, the investment in production equipment is large and the equipment requirements are high. On the other hand, due to the thickness limitation between layers, it is suitable for rated voltage 5V-100V voltage protection; during surge impact, due to the multilayer structure, heat imbalance easily leads to crack failure; for example, Chinese patent CN202010966184.2 discloses a method using traditional plug-in assembly and coating flattening. Processing, horizontal mounting scheme; Chinese patent CN201820356800.0 discloses a matrix varistor patch packaging scheme, and Chinese patent CN201711165632.3 discloses an embedded varistor flat-mount packaging scheme, both of which use traditional varistor chips. After lead or frame welding, the surface electrodes are parallel to the PCB board and flattened to achieve SMD mounting. However, the structure is relatively complex, the lead processing size consistency is poor, and production control is difficult. In addition, the chip is packaged horizontally, with superimposed leads and packaging layers, which occupies more PCB board area; for example, Chinese patent CN201822145675.1 discloses a series structure varistor patch scheme, which uses two varistors in series, but the distance between the two varistor electrodes is small, which is easy to be punctured by air, resulting in limited product application.

[0004] Therefore, providing a chip zinc oxide varistor is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a chip zinc oxide varistor and a production method to solve the problems of large investment in device production equipment, high equipment requirements, easy crack failure due to heat imbalance, relatively complex structure, poor consistency of lead processing dimensions, difficult production control, flat chip packaging, superimposed leads and packaging layers, occupying more PCB board area, and small spacing between two varistor electrodes, which are easy to be broken down by air, resulting in limited product application.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a chip zinc oxide varistor, comprising a varistor ceramic, wherein a solder resist layer can be provided on all four sides of the varistor ceramic, electrodes are provided on both sides of the varistor ceramic, the electrodes are made by printing and sputtering, the solder resist layer is fixed to both sides of the varistor ceramic by coating, the coating method includes electroplating, brush plating, chemical plating, physical vapor deposition, chemical vapor deposition, thermal spraying, surfacing, laser beam and electron beam surface cladding, and hot dip plating, the solder resist layer is made of UV light-curing ink with different colorants, and the UV light-curing ink refers to an ink that uses ultraviolet light of different wavelengths and energies under ultraviolet irradiation to polymerize monomers in an ink binder into polymers until the ink forms a film and dries.

[0007] As a further solution of the present invention: the varistor ceramic sheet has a length of 2.5-5 mm, a width of 1.5-3.5 mm, and a height of 1-3 mm.

[0008] As a further solution of the present invention: the electrode is fully coated on the edge of the varistor ceramic sheet.

[0009] As a further solution of the present invention: the production method of the chip zinc oxide varistor specifically includes the following steps:

[0010] Step 1, preparing powder: preparing low-gradient zinc oxide powder, preparing gradient G=140V / mm powder, taking ZnO, Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, each part has a molar percentage of 90-95.5%, 4-5.8%, 0.2-0.3%: 0.2-0.4%: 0.2-0.4%, 0.35-0.45%: 0.05-0.2%: 0.010-0.03%: 0.005%-0.01%, mixing and grinding Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, and then mixing the ground mixture with ZnO and grinding, adding glue and spray drying to obtain zinc oxide pressure-sensitive porcelain powder;

[0011] Step 2: Pressing green sheets: The mold size is 4.1×2.9R0.1mm. Press the green sheets on the dry press. The thickness is 2.36mm. The density of the pressed sheets is 3.4g / cm 3 ;

[0012] Step three, debinding and firing, the green embryo sheet is pre-debinded and then fired to form a pressure-sensitive ceramic sheet. In this embodiment, the pre-debinding is carried out at a temperature of 560° for 3 hours in a muffle furnace, and then fired at a temperature of 1185° for 4.5 hours to obtain a pressure-sensitive ceramic sheet with a size of 3.5×2.5×2.0 mm. The debinding can also be carried out at a temperature of 560° for 3 hours in a muffle furnace during debinding and firing, and then fired at a temperature of 1125° for 4.5 hours. After the product is positioned on the rocker plate, green solder resist ink is applied on the four sides respectively, and a solder resist layer is formed after UV light curing;

[0013] Step 4: Make electrodes. Take 80% silver paste and print 2.0×2.0 mm electrodes at both ends of the length direction of the varistor ceramic sheet 1. After drying, burn the silver in a silver furnace.

[0014] Step 5: Prepare a solder mask layer. Take the yellow UV light-curing ink corresponding to 471K, print a 3.4×2.5 mm solder mask layer on both sides in the height direction, and prepare a sample after UV light curing.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The rectangular pressure-sensitive ceramic piece is convenient for the nozzle of the placement machine to adsorb and is not easy to roll;

[0017] 2. Electrodes without margins are set at both ends of the length direction of the varistor ceramic chip to facilitate the contact between the electrodes and the solder paste to achieve reflow soldering;

[0018] 3. The setting of solder mask can effectively prevent solder paste from contaminating the lower side of the ceramic body, resulting in a drop in varistor voltage and side flashover during surge impact.

[0019] 4. Different colors of solder resist can effectively distinguish the varistor voltage specifications;

[0020] 5. No leads, no secondary processing leads, simple structure, and precise size control. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The main view of the present invention Figure 1 ;

[0022] Figure 2 For the top view of the present invention Figure 1 ;

[0023] Figure 3 The side view of the present invention Figure 1 ;

[0024] Figure 4 The main view of the present invention Figure 2 ;

[0025] Figure 5 For the top view of the present invention Figure 2 ;

[0026] Figure 6 The side view of the present invention Figure 2 .

[0027] In the figure: 1. Varistor; 2. Electrode; 3. Solder mask. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The following is an explanation of an embodiment of the present invention based on the overall structure of the present invention.

[0030] See also Figures 1 to 6In an embodiment of the present invention, a chip zinc oxide varistor includes a varistor ceramic 1, a solder resist layer 3 can be provided on all sides of the varistor ceramic 1, electrodes 2 are provided on both sides of the varistor ceramic 1, the electrodes 2 are made by printing and sputtering, the solder resist layer 3 is fixed to both sides of the varistor ceramic 1 by coating, and the coating method includes electroplating, brush plating, chemical plating, physical vapor deposition, chemical vapor deposition, thermal spraying, surfacing, laser beam and electron beam surface cladding, and hot dip plating, and the solder resist layer 3 is made of UV light-curing ink with different colorants. UV light-curing ink refers to an ink that uses ultraviolet light of different wavelengths and energies under ultraviolet light to polymerize monomers in an ink binder into polymers until the ink forms a film and dries.

[0031] Please refer to Figure 1 , 2 , 3, 4, 5 and 6, the pressure-sensitive ceramic piece 1 is 2.5-5mm in length, 1.5-3.5mm in width and 1-3mm in height. The rectangular pressure-sensitive ceramic piece is convenient for the nozzle of the placement machine to adsorb and is not easy to roll.

[0032] Please refer to Figure 1 , 2 , 3, 4, 5 and 6, the electrode 2 is fully coated on the edge of the varistor ceramic sheet 1 to facilitate the contact between the electrode and the solder paste to achieve reflow soldering.

[0033] Please refer to Figure 1 , 2 , 3, 4, 5 and 6, the production method of the chip zinc oxide varistor specifically includes the following steps:

[0034] Step 1, preparing powder: preparing low-gradient zinc oxide powder, preparing gradient G=140V / mm powder, taking ZnO, Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, each part has a molar percentage of 90-95.5%, 4-5.8%, 0.2-0.3%: 0.2-0.4%: 0.2-0.4%, 0.35-0.45%: 0.05-0.2%: 0.010-0.03%: 0.005%-0.01%, mixing and grinding Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, and then mixing the ground mixture with ZnO and grinding, adding glue and spray drying to obtain zinc oxide pressure-sensitive porcelain powder;

[0035] Step 2: Pressing green sheets: The mold size is 4.1×2.9R0.1mm. Press the green sheets on the dry press. The thickness is 2.36mm. The density of the pressed sheets is 3.4g / cm 3 ;

[0036] Step three, debinding and firing, the green embryo sheet is pre-debinded and then fired to form a pressure-sensitive ceramic sheet 1. In this embodiment, the pre-debinding is carried out at a temperature of 560° for 3 hours in a muffle furnace, and then it is fired at a temperature of 1185° for 4.5 hours to obtain a pressure-sensitive ceramic sheet 1 with a size of 3.5×2.5×2.0 mm. The debinding can also be carried out at a temperature of 560° for 3 hours in a muffle furnace during debinding and firing, and then it is fired at a temperature of 1125° for 4.5 hours. After the product is positioned on the rocker plate, green solder resist ink is applied on the four sides respectively, and the solder resist layer 3 is formed after UV light curing;

[0037] Step 4, making electrodes 2, taking 80% silver paste, printing 2.0×2.0 mm electrodes 2 at both ends of the length direction of the varistor ceramic sheet 1, and then drying them, and then firing the silver in a silver firing furnace;

[0038] Step 5, making a solder resist layer 3, taking a yellow UV light curing ink corresponding to 471K, printing a 3.4×2.5 mm solder resist layer 3 on both sides in the height direction, and making a sample after UV light curing.

[0039] The production principle of the present invention is as follows: prepare low-gradient zinc oxide powder; prepare powder with gradient G=140V / mm; take ZnO, Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, mix and grind Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, mix and grind the ground mixture with ZnO, add glue and spray dry to obtain zinc oxide pressure-sensitive ceramic powder; press green body: the mold size is 4.1×2.9R0.1mm, on the dry press table, press the green body sheet, the thickness is 2.36mm, the tablet density e: 3.4g / cm 3 ; Debinding and firing: the green embryo sheet is pre-debinded and then fired to form a pressure-sensitive ceramic sheet 1; at this time, the pre-binding is carried out at 560° for 3 hours in a muffle furnace, and then fired at 1185° for 4.5 hours to obtain a pressure-sensitive ceramic sheet 1 with a size of 3.5×2.5×2.0mm; then the electrode 2 is made: 80% silver paste is taken, and 2.0×2.0mm electrodes 2 are printed on both ends of the length direction of the pressure-sensitive ceramic sheet 1; after drying, the silver is fired in a silver furnace; finally, the solder mask 3 is made: the yellow UV light-curing ink corresponding to 471K is taken, and 3.4×2.5mm solder mask 3 is printed on both sides in the height direction; the sample is obtained after UV light curing. This device adopts a fixed length, which is convenient for the layout of the solder joints of the PCB board. At the same time, there are no leads, the size is precisely controllable, and it is convenient for low-cost large-scale production.

[0040] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A zinc oxide chip varistor, comprising a varistor ceramic chip (1), characterized in that: The varistor (1) may be provided with a solder resist layer (3) on all sides, and electrodes (2) are provided on both sides of the varistor (1). The electrodes (2) are made by printing and sputtering. The solder resist layer (3) is fixed to both sides of the varistor (1) by coating. The coating method includes electroplating, brush plating, chemical plating, physical vapor deposition, chemical vapor deposition, thermal spraying, surfacing, laser beam and electron beam surface cladding, and hot dip plating. The solder resist layer (3) is made of UV light-curing ink with different colorants. The UV light-curing ink refers to an ink that uses ultraviolet light of different wavelengths and energies under ultraviolet irradiation to polymerize monomers in the ink binder into polymers until the ink forms a film and dries.

2. A chip zinc oxide varistor according to claim 1, characterized in that: The pressure-sensitive ceramic sheet (1) has a length of 2.5-5 mm, a width of 1.5-3.5 mm, and a height of 1-3 mm.

3. A chip zinc oxide varistor according to claim 1, characterized in that: The electrode (2) is fully coated on the edge of the pressure-sensitive ceramic sheet (1).

4. The method for producing a chip zinc oxide varistor according to claim 1, characterized in that: The production method of the chip zinc oxide varistor specifically comprises the following steps: Step 1, preparing powder: preparing low-gradient zinc oxide powder, preparing gradient G=140V / mm powder, taking ZnO, Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, each part has a molar percentage of 90-95.5%, 4-5.8%, 0.2-0.3%: 0.2-0.4%: 0.2-0.4%, 0.35-0.45%: 0.05-0.2%: 0.010-0.03%: 0.005%-0.01%, mixing and grinding Bi2O3, Co3O4, Sb2O3, MnCO3, Ni2O3, B2O3, CuO, Al2O3 powders, and then mixing the ground mixture with ZnO and grinding, adding glue and spray drying to obtain zinc oxide pressure-sensitive porcelain powder; Step 2: Pressing green sheets: The mold size is 4.1×2.9R0.1mm. Press the green sheets on the dry press. The thickness is 2.36mm. The density of the pressed sheets is 3.4g / cm 3 ; Step 3, debinding and firing, the green sheet is pre-debinded and then fired to form a pressure-sensitive ceramic sheet (1). In this embodiment, the pre-debinding is carried out in a muffle furnace at a temperature of 560° for 3 hours, and then fired at a temperature of 1185° for 4.5 hours to obtain a pressure-sensitive ceramic sheet (1) with a size of 3.5×2.5×2.0 mm. During the debinding and firing, the pre-debinding is carried out in a muffle furnace at a temperature of 560° for 3 hours, and then fired at a temperature of 1125° for 4.5 hours. After the product is positioned on a rocker plate, green solder resist ink is coated on four sides respectively, and a solder resist layer (3) is formed after UV light curing. Step 4, making electrodes (2), taking 80% silver paste, printing 2.0×2.0 mm electrodes (2) at both ends of the length direction of the varistor ceramic sheet 1, drying, and then burning the silver in a silver furnace; Step 5, making a solder resist layer (3), taking yellow UV light curing ink corresponding to 471K, printing a 3.4×2.5 mm solder resist layer (3) on both sides in the height direction, and obtaining a sample after UV light curing.

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