A slurry for ceramic dielectric filter solder face and a preparation method thereof

Abstract

This invention discloses a slurry for welding surfaces of ceramic dielectric filters and its preparation method. The slurry comprises, by weight, 65-90 parts silver powder, 0.5-3 parts glass powder, 0.5-3 parts inorganic additives, 3-15 parts organic carrier, and 3-15 parts solvent. The silver powder comprises, by weight, 10-50 parts spherical silver powder, 5-40 parts flake silver powder, and 10-50 parts microcrystalline silver powder. And / or the glass powder comprises, by weight, 30-70 parts bismuth oxide, 10-40 parts copper oxide, 5-20 parts boron oxide, 1-15 parts manganese oxide, 0.1-15 parts silicon oxide, 0.1-5 parts aluminum oxide, 0.1-3 parts calcium oxide, 0.1-3 parts sodium oxide, and 0.1-3 parts lithium oxide. This invention introduces flake silver powder or microcrystalline silver powder to reduce the density of the silver layer, thereby improving the silver etching phenomenon during the soldering of the filter functional surface to the PCB, effectively enhancing solderability and improving the adhesion of the paste; or introduces Bi-Cu-B-Mn glass powder to improve the solderability of the paste and improve its adhesion.

Description

Technical Field

[0001] This invention belongs to the field of electronic paste technology, and particularly relates to a paste for the welding surface of ceramic dielectric filters and its preparation method. Background Technology

[0002] With the development of mobile communication networks, communication signals will use higher microwave and even millimeter-wave frequency bands, making filters increasingly important. Ceramic dielectric filters, due to their small size, low loss, and high Q value, are gradually replacing metal cavity filters as the mainstream filters. Thanks to their superior performance, they have a wider range of applications in the mobile communication field.

[0003] To improve the performance of ceramic dielectric filters, a silver paste layer is coated on the surface of the filter. Therefore, metallization is one of the key technologies for ceramic dielectric filters, directly affecting the filter's performance and reliability. One side of the filter serves as the functional surface and is soldered to the PCB board. Conventional pastes, in pursuit of higher Q values ​​and lower insertion losses, often use combinations of silver powders with higher sintering activity, resulting in an extremely dense silver layer. However, when soldering this dense silver layer to the PCB board, it can easily lead to low solder adhesion on the filter's ceramic surface, cracking between the ceramic surface and the silver layer, and solder joint delamination, thus affecting filter performance and shortening the product's lifespan. Summary of the Invention

[0004] To address the above technical problems, this invention provides a paste for the soldering surface of ceramic dielectric filters and its preparation method. This invention reduces the density of the silver layer by introducing flake silver powder or microcrystalline silver powder, thereby improving the silver etching phenomenon during the soldering of the filter's functional surface to the PCB, effectively enhancing solderability, and improving the adhesion of the paste; or by introducing Bi-Cu-B-Mn glass powder to improve the solderability of the paste and enhance its adhesion.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A slurry for welding surfaces of ceramic dielectric filters comprises, by weight, 60-90 parts silver powder, 0.5-3 parts glass powder, 0.5-3 parts inorganic additives, 3-15 parts organic carrier, and 3-15 parts solvent.

[0007] The silver powder comprises, by weight, 10-50 parts spherical silver powder, 5-40 parts flake silver powder, and 10-50 parts microcrystalline silver powder, and / or

[0008] The glass powder comprises, by weight, 30-70 parts bismuth oxide, 10-40 parts copper oxide, 5-20 parts boron oxide, 1-15 parts manganese oxide, 0.1-15 parts silicon oxide, 0.1-5 parts aluminum oxide, 0.1-3 parts calcium oxide, 0.1-3 parts sodium oxide, and 0.1-3 parts lithium oxide.

[0009] Preferably, the spherical silver powder has a weight ratio of 20-40 parts, a particle size D50 of 1-3 μm, and a specific surface area of ​​0.3-0.6 m². 2 / g, tap density 5-7g / cm³ 3 .

[0010] Preferably, the flake-shaped silver powder has a weight ratio of 10-30 parts, a particle size D50 of 1-4 μm, and a specific surface area of ​​0.5-1.5 m². 2 / g, tapped density 3-5g / cm³ 3 .

[0011] Preferably, the microcrystalline silver powder has a weight ratio of 20-40 parts, a particle size D50 of 0.1-0.3 μm, and a specific surface area of ​​2.4-4.0 m². 2 / g, tap density 2-4g / cm³ 3 .

[0012] Preferably, the glass powder comprises 40-60 parts of bismuth oxide, 12-30 parts of copper oxide, 7-15 parts of boron oxide, 3-12 parts of manganese oxide, 1-12 parts of silicon oxide, 0.1-3 parts of aluminum oxide, 0.1-2 parts of calcium oxide, 0.1-2 parts of sodium oxide, and 0.1-2 parts of lithium oxide.

[0013] Preferably, the inorganic additive is any one or more of bismuth oxide, copper oxide, zinc oxide, zirconium oxide, tin oxide, or iron oxide.

[0014] Preferably, the organic carrier is any one or more of ethyl cellulose, rosin resin, acrylic resin, diethylene glycol monobutyl ether, terpineol, or diethylene glycol butyl ether acetate.

[0015] Preferably, the solvent is any one or more of diethylene glycol monobutyl ether, terpineol, diethylene glycol butyl ether acetate, DBE, or alcohol ester twelve.

[0016] Based on the same inventive concept, the present invention also provides a method for preparing a slurry for welding surfaces of ceramic dielectric filters, comprising the following steps:

[0017] Step A: Preparation of glass powder: Weigh out analytical grade oxides according to the following mass ratios: 30-70 parts bismuth oxide, 10-40 parts copper oxide, 5-20 parts boron oxide, 1-15 parts manganese oxide, 0.1-15 parts silicon oxide, 0.1-5 parts aluminum oxide, 0.1-3 parts calcium oxide, 0.1-3 parts sodium oxide, and 0.1-3 parts lithium oxide. Mix the mixed oxides, melt them at high temperature, and then cold roll them to obtain glass flakes. Finally, ball mill the glass flakes and sieve them to obtain glass powder.

[0018] Step B: Take 65-90 parts silver powder, 0.5-3 parts glass powder obtained in step A, 0.5-3 parts inorganic additives, 3-15 parts organic carrier, and 3-15 parts solvent according to the mass ratio, place them in a reaction vessel with a dispersion plate and stir. After stirring, place them on a three-roll mill for three-roll milling to obtain a slurry with a fineness of less than 10μm.

[0019] The silver powder is either spherical silver powder or a mixture of 10-50 parts spherical silver powder, 5-40 parts flake silver powder, and 10-50 parts microcrystalline silver powder.

[0020] Preferably, the high-temperature melting of the oxide specifically involves placing the mixed analytically pure oxide in an alumina crucible, placing it in a high-temperature muffle furnace, and holding it at 1100-1200℃ for 40-60 minutes.

[0021] Preferably, the molten oxide is poured onto a cold rolling mill for cold rolling to obtain glass flakes.

[0022] Preferably, glass flakes, ethanol, and zirconium oxide ball milling beads are placed in a nylon jar and ball milled on a roller mill for 36-60 hours. The liquid in the nylon jar is then sieved through a 200-250 mesh screen, dried, and the dried powder is sieved through a 300-400 mesh screen.

[0023] Preferably, the organic carrier is a mixture of 10-20 parts by mass of ethyl cellulose and 80-90 parts by mass of diethylene glycol monobutyl ether. Specifically, the preparation involves mixing ethyl cellulose and diethylene glycol monobutyl ether, and then heating and stirring in a constant temperature oil bath at 90°C for 4 hours.

[0024] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art:

[0025] When existing filters are soldered to the PCB board, the dense silver layer easily forms an alloy with the solder. During the SMT (Surface Mount Technology) stage, this can easily lead to a complete reaction between the solder and the silver layer, causing silver etching and resulting in a lack of silver paste coating on the filter surface, affecting adhesion. The paste of this invention uses silver powder including spherical silver powder, flake silver powder, and microcrystalline silver powder. Compared to commonly used spherical silver powder, the introduction of flake and microcrystalline silver powders, with their irregular shapes, reduces the packing density of the silver powder, decreasing the density of the silver layer after sintering. The voids in the sintered silver layer can hinder the rapid etching of the solder, enhancing solderability and improving the adhesion between the silver layer and the ceramic filter. Therefore, this invention, by introducing flake and microcrystalline silver powders, allows the silver paste to sinter into a non-dense silver layer, improving the silver etching phenomenon during the SMT stage, thereby enhancing solderability and improving adhesion.

[0026] The present invention can also use Bi-Cu-B-Mn glass powder, which can remain in the gaps within the silver layer, hindering the solder from eroding the silver layer, improving the solderability of the paste, and enhancing the bonding force with the ceramic filter. Therefore, the Bi-Cu-B-Mn glass powder of the present invention has better solderability than conventional Bi-Zn-B and can improve adhesion.

[0027] The slurry provided by this invention can be used on the functional surface of ceramic dielectric filters to enhance the solderability of the filters, improve the adhesion of the silver layer, and thus enhance the reliability and service life of the filters. Detailed Implementation

[0028] The following detailed description, in conjunction with specific embodiments, provides a slurry for welding surfaces of ceramic dielectric filters and its preparation method, based on the present invention. The advantages and features of the present invention will become clearer from the following description.

[0029] Example 1

[0030] When the functional surfaces of the filter are soldered to the PCB board, existing solder pastes, in pursuit of higher Q values ​​and lower insertion losses, tend to use combinations of silver powders with higher sintering activity, resulting in extremely dense silver layers. However, this dense silver layer easily forms alloys with the solder, leading to a complete reaction between the solder and the silver layer during the SMT stage, causing silver etching. This results in the filter surface lacking silver paste coverage, affecting filter performance. Therefore, this embodiment introduces different flake-shaped silver powders and microcrystalline silver powders to improve the silver etching phenomenon.

[0031] The slurry for welding surfaces of ceramic dielectric filters in this embodiment comprises, by weight, 65-90 parts silver powder, 0.5-3 parts glass powder, 0.5-3 parts inorganic additives, 3-15 parts organic carrier, and 3-15 parts solvent.

[0032] The silver powder, by weight, includes 10-50 parts spherical silver powder, 5-40 parts flake silver powder, and 10-50 parts microcrystalline silver powder.

[0033] The preferred weight ratio of spherical silver powder is 20-40 parts, with a particle size D50 of 1-3 μm and a specific surface area of ​​0.3-0.6 m². 2 / g, tap density 5-7g / cm³ 3 .

[0034] The preferred weight ratio of the flake-shaped silver powder is 10-30 parts, with a particle size D50 of 1-4 μm and a specific surface area of ​​0.5-1.5 m². 2 / g, tapped density 3-5g / cm³ 3 .

[0035] The preferred weight ratio of microcrystalline silver powder is 20-40 parts, with a particle size D50 of 0.1-0.3 μm and a specific surface area of ​​2-4 m². 2 / g, tap density 2-4g / cm³ 3 .

[0036] Example 2

[0037] This embodiment provides a slurry for welding surfaces of ceramic dielectric filters, comprising, by weight, 65-90 parts silver powder, 0.5-3 parts glass powder, 0.5-3 parts inorganic additives, 3-15 parts organic carrier, and 3-15 parts solvent;

[0038] The glass powder, by weight proportion, includes 30-70 parts bismuth oxide, 10-40 parts copper oxide, 5-20 parts boron oxide, 1-15 parts manganese oxide, 0.1-15 parts silicon oxide, 0.1-5 parts aluminum oxide, 0.1-3 parts calcium oxide, 0.1-3 parts sodium oxide, and 0.1-3 parts lithium oxide.

[0039] Preferably, the glass powder comprises 40-60 parts of bismuth oxide, 12-30 parts of copper oxide, 7-15 parts of boron oxide, 3-12 parts of manganese oxide, 1-12 parts of silicon oxide, 0.1-3 parts of aluminum oxide, 0.1-2 parts of calcium oxide, 0.1-2 parts of sodium oxide, and 0.1-2 parts of lithium oxide.

[0040] In this embodiment, the introduction of Bi-Cu-B-Mn glass can also improve the weldability of the welding surface and enhance the adhesion of the slurry.

[0041] Example 3

[0042] This embodiment contains 10-50 parts of spherical silver powder, 5-40 parts of flake silver powder and 10-50 parts of microcrystalline silver powder from Example 1, and 40-60 parts of bismuth oxide, 12-30 parts of copper oxide, 7-15 parts of boron oxide, 3-12 parts of manganese oxide, 1-12 parts of silicon oxide, 0.1-3 parts of aluminum oxide, 0.1-2 parts of calcium oxide, 0.1-2 parts of sodium oxide and 0.1-2 parts of lithium oxide and glass powder from Example 2.

[0043] The inorganic additives in Examples 1-3 are any one or more of bismuth oxide, copper oxide, zinc oxide, zirconium oxide, tin oxide, or iron oxide.

[0044] The organic carrier is any one or more of ethyl cellulose, rosin resin, acrylic resin, diethylene glycol monobutyl ether, terpineol, or diethylene glycol butyl ether acetate.

[0045] The solvent is any one or more of diethylene glycol monobutyl ether, terpineol, diethylene glycol butyl ether acetate, DBE, or alcohol ester twelve.

[0046] The following uses specific experimental examples and data to illustrate the viewpoints of this invention.

[0047] Prepare the slurry based on the raw materials listed in the table below:

[0048]

[0049] The glass powder composition ratio mentioned above includes: 35 parts bismuth oxide, 8 parts silicon oxide, 30 parts zinc oxide, 17 parts boron oxide, and 10 parts calcium oxide.

[0050] The glass embodiments corresponding to the above embodiments 4-12 are as follows:

[0051]

[0052] The methods for preparing the above-mentioned implementation sample and control sample slurry include:

[0053] Step 1: Take 10 parts of ethyl cellulose and put them into diethylene glycol monobutyl ether, and heat and stir in a constant temperature oil bath at 90℃ for 4 hours to obtain an organic carrier;

[0054] Step Two: Weigh the analytical grade oxides according to the mass ratios listed in the above embodiments or comparative examples, mix them, and stir on a roller mill for 4 hours to ensure thorough mixing of all raw materials. Place the mixed powder in an alumina crucible, place it in a high-temperature muffle furnace, and hold it at 1100-1200℃ for 40-60 minutes. Remove it and pour it onto a roller cold rolling mill for cold rolling to obtain glass flakes. Place the glass flakes and alcohol in a nylon can, add zirconia grinding beads, and ball mill on a roller mill for 48 hours. After that, take the liquid from the nylon can and sieve it through a 200-250 mesh sieve. After sieving, dry the liquid in a 100-degree oven, and then sieve the dried powder through a 300-400 mesh sieve to obtain glass powder.

[0055] Step 3: Place silver powder, glass powder, inorganic additives, organic carrier and solvent into a reactor with a dispersion plate and stir for 2 hours. After stirring, place the mixture on a three-roll mill for three-roll milling to obtain a slurry with a fineness of less than 10 μm.

[0056] The prepared slurry was coated onto the same filter surface, and after sintering, a silver layer was obtained. The appearance of the silver layer was observed, and the thickness of the silver layer was measured. At the same time, the silver layer was soldered to the PCB board, and the solderability, solder resistance and adhesion of the silver layer were tested.

[0057] The final experimental results are as follows:

[0058] Sintered appearance Silver layer thickness Solderability weldability Adhesion Comparison Sample 1 smooth 8.5μm OK NG <![CDATA[15.6N / mm 2 ]]> Comparison Sample 2 smooth 8.0μm OK NG <![CDATA[16.2N / mm 2 ]]> Comparison Sample 3 smooth 8.2μm OK NG <![CDATA[17.3N / mm 2 ]]> Implementation Sample 1 smooth 8.4μm OK OK <![CDATA[22.5N / mm 2 ]]> Implementation Sample 2 smooth 8.3μm OK OK <![CDATA[21.3N / mm 2 ]]> Implementation Sample 3 smooth 8.5μm OK OK <![CDATA[20.8N / mm 2 ]]> Sample 4 smooth 8.6μm OK OK <![CDATA[21.0N / mm 2 ]]> Implementation Sample 5 smooth 8.2μm OK OK <![CDATA[22.6N / mm 2 ]]> Implementation Sample 6 smooth 8.1μm OK OK <![CDATA[21.9N / mm 2 <!-- 5 -->]]> Implementation Sample 7 smooth 8.0μm OK OK <![CDATA[25.9N / mm 2 ]]> Implementation Sample 8 smooth 8.5μm OK OK <![CDATA[26.4N / mm 2 ]]> Implementation Sample 9 smooth 8.4μm OK OK <![CDATA[25.9N / mm 2 ]]> Implementation Sample 10 smooth 8.5μm OK OK <![CDATA[26.1N / mm 2 ]]> Implementation Sample 11 smooth 8.3μm OK OK <![CDATA[25.5N / mm 2 ]]> Implementation Sample 12 smooth 8.3μm OK OK <![CDATA[26.0N / mm 2 ]]>

[0059] The experimental results above show that the solderability of samples 1-12 is good, and the adhesion is greater than that of control samples 1-3. Samples 1-3, compared to control samples 1-3, not only have improved solderability but also have greater adhesion. This indicates that the simultaneous use of spherical silver powder, flake silver powder, and microcrystalline silver powder can enhance the solderability of the paste and increase its adhesion. This is mainly because irregular flake silver powder and microcrystalline silver powder are introduced into the spherical silver powder base, reducing the packing density of the silver powder and decreasing the density of the silver layer after sintering. The voids in the sintered silver layer can hinder the rapid erosion of the solder, thus enhancing solderability and strengthening the silver layer. The adhesion of the samples 4-6 to the ceramic filter shows that compared with the control samples 1-3, the use of the glass powder of the present invention can also improve the solderability of the slurry and increase the adhesion. This is mainly because the Bi-Cu-B-Mn glass powder of this embodiment can remain in the gaps in the silver layer, hindering the solder from eroding the silver layer, thereby improving the solderability of the slurry and increasing the adhesion between the silver layer and the ceramic filter. The adhesion of the samples 7-12 is greater than that of the samples 1-6, indicating that using spherical silver powder + flake silver powder + microcrystalline silver powder as silver powder and Bi-Cu-B-Mn glass powder can increase the adhesion of the silver layer more significantly.

[0060] The embodiments of the present invention have been described in detail above with reference to the examples, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A paste for a ceramic dielectric filter solder face, characterized by, 65-90 parts of silver powder, 0.5-3 parts of glass powder, 0.5-3 parts of inorganic additive, 3-15 parts of organic carrier and 3-15 parts of solvent by weight ratio; The silver powder comprises 10-50 parts of spherical silver powder, 5-40 parts of flaky silver powder and 10-50 parts of microcrystalline silver powder by weight; the particle size D50 of the spherical silver powder is 1-3 μm, the specific surface area is 0.3-0.6 m 2 / g, and the tap density is 5-7 g / cm 3 ; the particle size D50 of the flaky silver powder is 1-4 μm, the specific surface area is 0.5-1.5 m 2 / g, and the tap density is 3-5 g / cm 3 ; the particle size D50 of the microcrystalline silver powder is 0.1-0.3 μm, the specific surface area is 2-4 m 2 / g, and the tap density is 2-4 g / cm 3 ; And / or, the glass powder comprises bismuth oxide 30-70 parts, copper oxide 10-40 parts, boron oxide 5-20 parts, manganese oxide 1-15 parts, silicon oxide 0.1-15 parts, aluminum oxide 0.1-5 parts, calcium oxide 0.1-3 parts, sodium oxide 0.1-3 parts and lithium oxide 0.1-3 parts by weight ratio.

2. The paste for a ceramic dielectric filter bonding surface according to claim 1, characterized by, The weight ratio of the spherical silver powder is 20-40 parts.

3. The paste for a ceramic dielectric filter bonding surface according to claim 1, characterized by, The weight ratio of the flaky silver powder is 10-30 parts.

4. The paste for a ceramic dielectric filter bonding surface according to claim 1, wherein The weight ratio of the microcrystalline silver powder is 20-40 parts.

5. The paste for a ceramic dielectric filter bonding surface according to claim 1, wherein The glass powder comprises bismuth oxide 40-60 parts, copper oxide 12-30 parts, boron oxide 7-15 parts, manganese oxide 3-12 parts, silicon oxide 1-12 parts, aluminum oxide 0.1-3 parts, calcium oxide 0.1-2 parts, sodium oxide 0.1-2 parts and lithium oxide 0.1-2 parts.

6. The paste for a ceramic dielectric filter bonding surface according to claim 1, wherein The inorganic additive is any one or several of bismuth oxide, copper oxide, zinc oxide, zirconium oxide, tin oxide or iron oxide.

7. The paste for a ceramic dielectric filter bonding surface according to claim 1, wherein The organic carrier is any one or several of ethyl cellulose, rosin resin, acrylic resin, diethylene glycol monobutyl ether, terpineol or diethylene glycol butyl ether acetate.

8. The paste for a ceramic dielectric filter bonding surface according to claim 1, wherein The solvent is any one or several of diethylene glycol monobutyl ether, terpineol, diethylene glycol butyl ether acetate, DBE or alcohol ester twelve.

9. A method for preparing the paste for the soldering surface of a ceramic dielectric filter according to claim 1, characterized by, Comprising the following steps: Step A: preparing glass powder: taking 30-70 parts of bismuth oxide, 10-40 parts of copper oxide, 5-20 parts of boron oxide, 1-15 parts of manganese oxide, 0.1-15 parts of silicon oxide, 0.1-5 parts of aluminum oxide, 0.1-3 parts of calcium oxide, 0.1-3 parts of sodium oxide and 0.1-3 parts of lithium oxide by weight ratio, mixing the analytical pure oxides, high-temperature melting the mixed oxides, cold rolling to obtain glass melting sheet, then ball milling the glass melting sheet and sieving to obtain glass powder; Step B: taking 65-90 parts of silver powder and 0.5-3 parts of glass powder, 0.5-3 parts of inorganic additive, 3-15 parts of organic carrier and 3-15 parts of solvent by weight ratio, stirring in a reaction kettle with a dispersion disc, then placing on a three-roll machine for three-roll to obtain slurry with fineness less than 10 μm; The silver powder is a mixed silver powder of 10-50 parts of spherical silver powder, 5-40 parts of flaky silver powder and 10-50 parts of microcrystalline silver powder.

10. The method for preparing a paste for a ceramic dielectric filter bonding surface according to claim 9, characterized by, The high-temperature melting of the mixed oxides in step A is specifically: placing the mixed analytical pure oxides in an alumina crucible, putting into a high-temperature muffle furnace, keeping at 1100-1200 ℃ for 40-60 min.

11. The method of preparing a paste for a ceramic dielectric filter bonding surface according to claim 9, characterized by, The cold rolling in step A is specifically: pouring the melted oxides on a lubricated rolling mill for cold rolling and rolling to obtain glass melting sheet.

12. The method for preparing a paste for a ceramic dielectric filter bonding surface according to claim 9, characterized by, The ball milling and sieving of the glass melting sheet in step A is specifically: placing the glass melting sheet, ethanol and zirconia ball milling beads in a nylon tank, ball milling on a double roller machine for 36-60 h, taking the liquid in the nylon tank for 200-250 mesh sieving, drying after sieving, and sieving the dried powder to 300-400 mesh.

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