Co-fired silver conductor paste for high-thermal-expansion-coefficient LTCC (Low Temperature Co-fired Ceramic) raw tape and preparation method thereof

Abstract

The invention discloses a co-fired silver conductor paste for a high-thermal-expansion-coefficient LTCC (Low Temperature Co-fired Ceramic) green tape and a preparation method thereof. The preparation method comprises the following steps: weighing 45-72 parts of silver powder, 8-22 parts of glass powder, 3-10 parts of LTCC medium powder, 8-24 parts of an organic solvent, 1.6-6 parts of organic resin and 0-2 parts of a thixotropic agent, putting the raw materials into a ball mill, and mixing for 20-30 minutes at the rotating speed of 100-400 rpm to obtain mixed slurry; the mixed slurry is taken out and put into a three-roller grinding machine to be dispersed and ground, and fine grinding slurry is obtained; the fineness of the fine grinding slurry is tested through a scraper fineness meter, and the fineness of the fine grinding slurry is smaller than 20 micrometers; and filtering the fine grinding slurry by using a 325-400-mesh screen to obtain the silver conductor slurry. The thermal expansion coefficient of the sintered silver layer is adjusted, and meanwhile, the LTCC medium powder is added into the silver powder, so that the matching performance with a high-thermal-expansion-coefficient LTCC substrate is enhanced.

Description

Technical field:

[0001] The invention belongs to the technical field of electronic packaging materials, and particularly relates to a silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient and a preparation method thereof. Background technology:

[0002] Green tape co-fired silver conductor paste plays a crucial role in low-temperature co-fired ceramic (LTCC) technology. Currently available LTCC green tape co-fired silver conductor pastes, such as Ferro A6M, A6ME, and L8, DuPont™ 9K7 and 951, and domestically produced LTCC co-fired silver pastes, are not well-suited for high-thermal expansion LTCC substrates. This is primarily due to poor flatness after co-firing, and interconnect conductors short-circuiting and failure after repeated temperature cycling.

[0003] Therefore, developing a silver conductor paste that has good compatibility with high thermal expansion coefficient LTCC substrates is an urgent problem to be solved.

[0004] The information disclosed in this background section is only intended to enhance understanding of the overall background of the invention and should not be considered as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention:

[0005] The present invention aims to provide a silver conductor paste for co-firing LTCC green tape with a high thermal expansion coefficient and a preparation method thereof. Glass powder with a high thermal expansion coefficient is mixed into silver powder to adjust the thermal expansion coefficient of the silver layer after sintering. At the same time, the powder has good sintering bonding with the substrate, further enhancing the adhesion, thereby overcoming the above-mentioned defects in the prior art.

[0006] To achieve the above object, the present invention provides a silver conductor paste for co-fired LTCC green tape with a high thermal expansion coefficient, the components of which are: 70-90 parts of inorganic and metal powders and 10-30 parts of an organic vehicle; wherein the inorganic and metal powders include 45-72 parts of silver powder, 8-22 parts of glass powder, and 3-10 parts of LTCC dielectric powder; and the organic vehicle includes 8-24 parts of an organic solvent, 1.6-6 parts of an organic resin, and 0-2 parts of a thixotropic agent.

[0007] Preferably, in the technical solution, the silver powder is at least one of silver powders having a D50 particle size of 0.6-0.8, 0.7-2, 3-5, and 0.2-0.5.

[0008] Preferably, in the technical solution, the silver powder is silver powder with a D50 particle size of 0.6-0.8, 0.7-2, or 3-5, among which 11.5-15 parts of silver powder with a D50 particle size of 0.6-0.8, 15-49 parts of silver powder with a D50 particle size of 0.7-2, and 11.5-15 parts of silver powder with a D50 particle size of 3-5.

[0009] Preferably, in the technical solution, the silver powder is silver powder with a D50 particle size of 0.6-0.8 and 0.2-0.5, wherein 40-50 parts of silver powder with a D50 particle size of 0.6-0.8 and 5-32 parts of silver powder with a D50 particle size of 0.2-0.5 are used.

[0010] Preferably, in the technical solution, the components of the glass powder are: 10-30 parts of SiO2, 5-25 parts of B2O3, 5-10 parts of BaO, 40-65 parts of MgO, 0.5-5 parts of ZrO2, 0.2-3 parts of P2O5, and 0.2-5 parts of M2O, wherein M represents an alkali metal.

[0011] Preferably, in the technical solution, the organic solvent is at least one of diethylene glycol monobutyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, α-terpineol, β-terpineol, and γ-terpineol.

[0012] Preferably, in the technical solution, the organic resin is at least one of ethyl cellulose and acrylic resin.

[0013] Preferably, in the technical solution, the thixotropic agent is castor oil or a castor oil derivative.

[0014] A method for preparing a high thermal expansion coefficient LTCC green tape co-fired silver conductor paste, comprising the following steps: (1) weighing 45-72 parts of silver powder, 8-22 parts of glass powder, 3-10 parts of LTCC dielectric powder, 8-24 parts of an organic solvent, 1.6-6 parts of an organic resin, and 0-2 parts of a thixotropic agent, placing the raw materials in a ball mill, and mixing them at a rotation speed of 100-400 rpm for 20-30 minutes to obtain a mixed paste;

[0015] (2) taking out the mixed slurry and placing it in a three-roll mill for dispersion grinding to obtain a finely ground slurry; the fineness of the finely ground slurry is tested by a scraper fineness meter, and the fineness of the finely ground slurry is less than 20 μm;

[0016] (3) The finely ground slurry is filtered through a 325-400 mesh screen to obtain a silver conductor slurry.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] Glass powder is mixed into the silver powder to adjust the thermal expansion coefficient of the silver layer after sintering. At the same time, LTCC dielectric powder is added to the silver powder to achieve good sintering bonding with the LTCC substrate, further enhancing the matching performance with the high thermal expansion coefficient LTCC substrate. Description of the drawings:

[0019] Figure 1 This is a thermal expansion coefficient curve of a high thermal expansion coefficient LTCC substrate in the range of 25°C-350°C;

[0020] Figure 2 This is a thermal expansion coefficient curve in the range of 25°C-350°C for the high thermal expansion coefficient LTCC green tape co-fired silver conductor paste using glass frits 4# and 6# of the present invention. Specific implementation method:

[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0022] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0023] A silver conductor paste for co-fired LTCC green tape with a high thermal expansion coefficient is provided, comprising: 70-90 parts of inorganic and metal powders and 10-30 parts of an organic vehicle; wherein the inorganic and metal powders include 45-72 parts of silver powder, 8-22 parts of glass powder, and 3-10 parts of LTCC dielectric powder; the organic vehicle includes 8-24 parts of an organic solvent, 1.6-6 parts of an organic resin, and 0-2 parts of a thixotropic agent; the silver powder is selected from at least one of silver powders having a D50 particle size of 0.6-0.8, 0.7-2, 3-5, and 0.2-0.5; and the glass powder comprises: 10-30 parts of SiO2, 5-25 parts of B2O3, 5-10 parts of BaO, 40-65 parts of MgO, 0.5-5 parts of ZrO2, 0.2-3 parts of P2O5, 0.2-5 parts of M2O, wherein M represents an alkali metal; the organic solvent is selected from at least one of diethylene glycol monobutyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, α-terpineol, β-terpineol, and γ-terpineol; the organic resin is selected from at least one of ethyl cellulose and acrylic resin; the thixotropic agent is selected from castor oil or a castor oil derivative.

[0024] Prepare glass powder: Prepare glass powder 1#-6# respectively, and the composition is shown in Table 1.

[0025] Table 1 Composition of glass powder 1#-6#

[0026] Ex# 1 2 3 4 5 6 <![CDATA[SiO2]]> 15 22.2 13.5 13.5 13.5 15 <![CDATA[B2O3]]> 17 11.7 17 17 22 17 BaO 6 6.7 6 6 5.4 6 MgO 57 52.5 62 59 51.2 57 <![CDATA[ZrO2]]> 2.5 2.0 0.6 1.6 2.3 2.5 <![CDATA[P2O5]]> 2 0.4 0.4 2.4 1.8 2.0 <![CDATA[Li2O]]> 0.5 0.5 0.5 0.5 3.8 <![CDATA[Na2O]]> 0.5

[0027] The thermal expansion coefficients of glass powder 1#-6# and high thermal expansion coefficient LTCC substrate were tested in the range of 25℃-350℃. The test results are as follows: Figure 1-2 and as shown in Table 2.

[0028] Table 2 Thermal expansion coefficients of glass powders 4#, 6# and high thermal expansion coefficient LTCC substrates in the range of 25℃-350℃

[0029] sample <![CDATA[Coefficient of thermal expansion (×10 -6 )]]> substrate 11.6@300℃ Glass powder 4# 12.8@300℃ Glass powder 6# 12.4@300℃

[0030] Depend on Figure 1-2 As shown in Table 2, glass powders 4# and 6# have similar thermal expansion coefficients to the LTCC substrate in the range of 25°C-350°C, and can be used when configuring silver conductor paste.

[0031] Preparation of organic carriers: Prepare organic carriers 1# and 2# respectively. The configuration components are shown in Table 3.

[0032] Table 3 Composition of carriers 1# and 2#

[0033] Ex# 1 2 Diethylene glycol monobutyl ether 10.4 11 2,2,4-Trimethyl-1,3-pentanediol monoisobutyrate 39 33 α-Terpineol 30 30 β-Terpineol 10 γ-Terpineol 5 Ethyl cellulose 19 9 acrylic resin 1.6 castor oil Castor oil derivatives 2

[0034] Example 1

[0035] A silver conductor paste for co-fired LTCC green tape with a high thermal expansion coefficient comprises: 12.6 parts of silver powder with a D50 particle size of 0.6-0.8, 40.8 parts of silver powder with a D50 particle size of 0.7-2, 12.6 parts of silver powder with a D50 particle size of 3-5, 8.3 parts of 6# glass powder, 3.2 parts of LTCC dielectric powder, and 22.5 parts of 1# organic vehicle.

[0036] A method for preparing a high thermal expansion coefficient LTCC green tape co-fired silver conductor paste, comprising the following steps: (1) placing 12.6 parts of silver powder with a D50 particle size of 0.6-0.8, 40.8 parts of silver powder with a D50 particle size of 0.7-2, 12.6 parts of silver powder with a D50 particle size of 3-5, 8.3 parts of glass powder 6#, 3.2 parts of LTCC dielectric powder, and 22.5 parts of organic vehicle 1# into a ball mill, and mixing at a rotation speed of 100-400 rpm for 20-30 minutes to obtain a mixed paste;

[0037] (2) taking out the mixed slurry and placing it in a three-roll mill for dispersion grinding to obtain a finely ground slurry; the fineness of the finely ground slurry is tested by a scraper fineness meter, and the fineness of the finely ground slurry is less than 20 μm;

[0038] (3) The finely ground slurry is filtered through a 325-400 mesh screen to obtain a silver conductor slurry.

[0039] Example 2

[0040] A silver conductor paste for co-fired LTCC green tape with a high thermal expansion coefficient comprises: 12.4 parts of silver powder with a D50 particle size of 0.6-0.8, 41.2 parts of silver powder with a D50 particle size of 0.7-2, 12.4 parts of silver powder with a D50 particle size of 3-5, 8.5 parts of 4# glass powder, 3.5 parts of LTCC dielectric powder, and 22 parts of 1# organic vehicle.

[0041] A method for preparing a high thermal expansion coefficient LTCC green tape co-fired silver conductor paste, comprising the following steps: (1) placing 12.4 parts of silver powder with a D50 particle size of 0.6-0.8, 41.2 parts of silver powder with a D50 particle size of 0.7-2, 12.4 parts of silver powder with a D50 particle size of 3-5, 8.5 parts of glass powder 4#, 3.5 parts of LTCC dielectric powder, and 22 parts of organic vehicle 1# into a ball mill, and mixing the above raw materials at a rotation speed of 100-400 rpm for 20-30 minutes to obtain a mixed paste;

[0042] (2) taking out the mixed slurry and placing it in a three-roll mill for dispersion grinding to obtain a finely ground slurry; the fineness of the finely ground slurry is tested by a scraper fineness meter, and the fineness of the finely ground slurry is less than 20 μm;

[0043] (3) The finely ground slurry is filtered through a 325-400 mesh screen to obtain a silver conductor slurry.

[0044] Example 3

[0045] A silver conductor paste for co-fired LTCC green tape with a high thermal expansion coefficient comprises the following components: 24.2 parts of silver powder with a D50 particle size of 0.2-0.5, 40.5 parts of silver powder with a D50 particle size of 0.7-2, 9.4 parts of 6# glass powder, 3.8 parts of LTCC dielectric powder, and 22.1 parts of 2# organic vehicle.

[0046] A method for preparing a high thermal expansion coefficient LTCC green tape co-fired silver conductor paste, comprising the following steps: (1) placing 24.2 parts of silver powder with a D50 particle size of 0.2-0.5, 40.5 parts of silver powder with a D50 particle size of 0.7-2, 9.4 parts of glass powder 6#, 3.8 parts of LTCC dielectric powder, and 22.1 parts of organic vehicle 2# in a ball mill, and mixing the above materials at a rotation speed of 100-400 rpm for 20-30 minutes to obtain a mixed paste;

[0047] (2) taking out the mixed slurry and placing it in a three-roll mill for dispersion grinding to obtain a finely ground slurry; the fineness of the finely ground slurry is tested by a scraper fineness meter, and the fineness of the finely ground slurry is less than 20 μm;

[0048] (3) The finely ground slurry is filtered through a 325-400 mesh screen to obtain a silver conductor slurry.

[0049] Slurry performance verification

[0050] The silver conductor pastes prepared in Examples 1-3 and the conventional silver conductor pastes of the comparative example were prepared into samples 1-4 according to the following process:

[0051] Printing: The slurry was screen-printed onto a ceramic green tape at a printing pressure of 200 kPa, a printing speed of 50 mm / s, and a spacing of 2 mm. The screen used was a 250-mesh stainless steel screen.

[0052] Drying: 80℃ for 15 minutes;

[0053] Lamination: After lamination, use water isostatic pressing method, pressing pressure 2000psi, time 20 minutes;

[0054] Sintering: sintering in air at 850-900℃ for 30 minutes.

[0055] The physical parameters of the silver conductor layers of samples 1 and 3 were tested, and the test results are shown in Table 4.

[0056] Table 4 Physical parameters of the silver conductor layer of samples 1 and 3

[0057] Silver paste name Sample 1 Sample 3 Sintered thickness (um) 5-10 5-10 Resistivity (mΩ / sq@25um) 0.8 1.2 Viscosity (Pa.S) 180 130 Solid content (%) 73.5 73.8

[0058] It can be seen from Table 4 that the physical parameters of the silver conductor layers of samples 1 and 3 meet the design requirements.

[0059] Samples 1, 2, and 4 were subjected to a scratch resistance test. The silver conductor layer was repeatedly scratched with a blade to test the adhesion of the silver conductor layer. The test results are shown in Table 5.

[0060] Table 5 Scratch resistance test table of samples 1, 2, and 4

[0061]

[0062]

[0063] As can be seen from Table 5, compared with the samples produced by ordinary silver conductor paste, the samples produced by the silver conductor paste configured by the patent solution have good sintering bonding with the LTCC substrate, good adhesion performance, and are not easily scratched.

[0064] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient, characterized by: Its components include 70-90 parts of inorganic and metal powders and 10-30 parts of organic carriers; the inorganic and metal powders include 45-72 parts of silver powder, 8-22 parts of glass powder, and 3-10 parts of LTCC medium powder; the organic carrier includes 8-24 parts of organic solvent, 1.6-6 parts of organic resin, and 0-2 parts of thixotropic agent.

2. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 1, characterized in that: The silver powder is selected from at least one of silver powders having a D50 particle size of 0.6-0.8, 0.7-2, 3-5, and 0.2-0.

5.

3. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 2, characterized in that: Silver powder is selected from silver powders with D50 particle sizes of 0.6-0.8, 0.7-2, and 3-5, among which silver powder with D50 particle size of 0.6-0.8 is 11.5-15 parts, silver powder with D50 particle size of 0.7-2 is 15-49 parts, and silver powder with D50 particle size of 3-5 is 11.5-15 parts.

4. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 2, characterized in that: Silver powder is silver powder with a D50 particle size of 0.6-0.8 and 0.2-0.5, wherein the silver powder with a D50 particle size of 0.6-0.8 is 40-50 parts, and the silver powder with a D50 particle size of 0.2-0.5 is 5-32 parts.

5. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 2, characterized in that: The components of the glass powder are: 10-30 parts of SiO2, 5-25 parts of B2O3, 5-10 parts of BaO, 40-65 parts of MgO, 0.5-5 parts of ZrO2, 0.2-3 parts of P2O5, and 0.2-5 parts of M2O, wherein M represents an alkali metal.

6. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 2, characterized in that: The organic solvent is selected from at least one of diethylene glycol monobutyl ether, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, α-terpineol, β-terpineol, and γ-terpineol.

7. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 2, characterized in that: The organic resin is selected from at least one of ethyl cellulose and acrylic resin.

8. The silver conductor paste for co-fired LTCC green tape with high thermal expansion coefficient according to claim 2, characterized in that: The thixotropic agent is castor oil or a castor oil derivative.

9. A method for preparing a high thermal expansion coefficient LTCC green tape co-fired silver conductor paste according to any one of claims 1 to 8, comprising the steps of: (1) weighing 45-72 parts of silver powder, 8-22 parts of glass powder, 3-10 parts of LTCC dielectric powder, 8-24 parts of organic solvent, 1.6-6 parts of organic resin, and 0-2 parts of thixotropic agent, placing the raw materials in a ball mill, and mixing at a rotation speed of 100-400 rpm for 20-30 minutes to obtain a mixed paste; (2) taking out the mixed slurry and placing it in a three-roll mill for dispersion grinding to obtain a finely ground slurry; the fineness of the finely ground slurry is tested by a scraper fineness meter, and the fineness of the finely ground slurry is less than 20 μm; (3) The finely ground slurry is filtered through a 325-400 mesh screen to obtain a silver conductor slurry.

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