Printing tungsten paste for HTCC ceramic matrix and preparation method of printing tungsten paste

Abstract

The invention discloses a printing tungsten paste for an HTCC ceramic matrix. The printing tungsten paste comprises the following basic materials in percentage by mass: 78-82% of tungsten powder, 4-8% of aluminum oxide ceramic powder and 14-18% of an organic carrier; the mass of the iron-nickel powder accounts for 0.5-5% of the mass of the base material, and the mass of the hydrogenated castor oil accounts for 0.3-0.6% of the mass of the base material. The invention also discloses a preparation method of the printing tungsten paste for the HTCC ceramic matrix. The method is characterized in that the iron-nickel powder is introduced into the tungsten slurry, iron and nickel belong to transition metal and construct a d10 configuration with tungsten metal, sintering activation energy among tungsten particles can be reduced, activated sintering occurs, iron and nickel serve as a'bridge 'for tungsten atom transmission, and therefore the sintering temperature and sheet resistance of a film layer can be reduced at the same time; and meanwhile, energy loss and conductor loss are reduced.

Description

Technical Field

[0001] The present invention relates to the field of printed tungsten paste, and particularly to a printed tungsten paste for an HTCC ceramic substrate and a preparation method thereof. Background Art

[0002] Based on modern semiconductor process technology, millions of interconnected electronic components such as resistors and transistors are integrated on a tiny silicon chip. To make full use of and protect this high-integration-density chip, it is necessary to package it into a ceramic base to make it a compact, reliable and independent unit that can be connected to an external circuit. On the other hand, according to Moore's law, the physical size between transistors on a silicon chip is gradually approaching the theoretical limit. To cope with this limit, chips responsible for different functions can be packaged into a ceramic base in a horizontal arrangement and vertical stacking manner to make it a three-dimensional high-density integrated unit. A ceramic base is a three-dimensional interconnection structure formed by sequentially laminating green ceramic sheets with printed conductive patterns and conductive vias according to the designed process and then undergoing sintering processing under atmosphere protection. The conductive patterns and conductive vias meet the electrical interconnection requirements between chips, and the ceramic sheets meet the heat dissipation and mechanical support requirements of the chips. At present, the ceramic base preparation technology based on high-temperature co-fired ceramics (HTCC) has been widely used.

[0003] HTCC can be generally described as based on the screen printing process, using conductor paste to complete circuit patterning printing and via filling on each layer of the green body, then laminating, pressing, cutting and high-temperature sintering the green body, and finally obtaining a multi-layer ceramic structure with electrical connection and tight combination between layers, realizing the mutual connection between ceramics and metals. Tungsten paste is an important part of HTCC materials. Since tungsten has the highest melting point among all metals and the conductivity of tungsten is lower than that of high-conductivity materials such as gold, silver and copper, the printed tungsten film layer needs to be sintered at a high temperature and the sheet resistance of the film layer is relatively high after sintering. This not only causes high energy consumption but also brings relatively high conductor loss to the electrical signal transmission of the chip. Therefore, reducing the sintering temperature and sheet resistance of the film layer simultaneously is beneficial to reducing energy loss and conductor loss. Summary of the Invention

[0004] The object of the present invention is to provide a printed tungsten paste for an HTCC ceramic substrate.

[0005] The present invention also provides a preparation method of a printed tungsten paste for an HTCC ceramic substrate.

[0006] The innovation point of the present invention is to introduce iron-nickel powder into the tungsten paste. Since iron and nickel belong to transition metals, the two construct a d10 configuration with tungsten metal, which can reduce the sintering activation energy between tungsten particles and initiate activated sintering, making iron and nickel act as the "bridge" for tungsten atom transmission, thereby being able to reduce the sintering temperature and sheet resistance of the film layer simultaneously, and reducing energy loss and conductor loss simultaneously.

[0007] To achieve the above-mentioned invention object, the technical solution of the present invention is as follows:

[0008] A printing tungsten paste for HTCC ceramic substrate, comprising base materials in the following mass percentages: 78-82% of tungsten powder, 4-8% of alumina ceramic powder, and 14-18% of organic carrier; it also includes iron-nickel powder and hydrogenated castor oil, the mass of the iron-nickel powder is 0.5-5% of the mass of the base materials, and the mass of the hydrogenated castor oil is 0.3-0.6% of the mass of the base materials.

[0009] Furthermore, the particle size of the tungsten powder conforms to a normal distribution, D50 is 7.92 μm, D90 is 16.00 μm, and the tapped density is 8.26 g / cm3.

[0010] Furthermore, the particle size of the iron-nickel powder conforms to a normal distribution, D50 is 1-2 μm, and the mass ratio of iron to nickel in the iron-nickel powder is 1:1.

[0011] Furthermore, the bulk density of the alumina ceramic powder is 1.8-2.3 g / cm3.

[0012] Furthermore, the organic carrier is composed of resin ethyl cellulose and organic solvent terpineol in a mass ratio of 10-15:85-90, and the molecular weight of ethyl cellulose is 380,000-430,000.

[0013] A preparation method of a printing tungsten paste for HTCC ceramic substrate, comprising the following steps:

[0014] (1) Preparation of the organic carrier: According to the organic carrier formula, stir and directly dissolve it completely in a water bath at 65-70 °C, and cool it to room temperature to obtain the organic carrier;

[0015] (2) Preparation of the tungsten paste precursor: Take the organic carrier, tungsten powder, iron-nickel powder, alumina ceramic powder and hydrogenated castor oil according to the formula, and stir until it becomes a paste state without powder falling off to obtain the tungsten paste precursor;

[0016] (3) Roll rolling treatment: Use a three-roll mill to roll the tungsten paste precursor in step (2). First, pre-roll for 2 min under the conditions that the feed port gap is 170-180 μm, the discharge port gap is 170-180 μm, and the rotation speed is 170-180 r / min; then adjust the feed port gap to 85-90 μm, the discharge port gap to 42-45 μm, and roll 3 times at a rotation speed of 170-180

[0017] r / min; then adjust the feed port gap to 42-45 μm, the discharge port gap to 21-23 μm, and roll 3 times at a rotation speed of 170-180 r / min; finally, adjust the feed port gap to 21-23 μm, the discharge port gap to 10-12 μm, and roll 3 times at a rotation speed of 170-180 r / min to obtain the finished product.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. Due to the physical properties of tungsten metal with a high melting point and low electrical conductivity in the present invention, the sintering temperature of the printed tungsten film layer is relatively high and the sheet resistance of the film layer after sintering is relatively high. In the present invention, iron-nickel powder is introduced into the tungsten paste. Since iron and nickel belong to transition metals, the two construct a d10 configuration with tungsten metal, which can reduce the sintering activation energy between tungsten particles, initiate activated sintering, and enable iron and nickel to act as the "bridge" for tungsten atom transmission. Thus, it can simultaneously reduce the sintering temperature and sheet resistance of the film layer, and reduce energy loss and conductor loss at the same time.

[0020] 2. In the present invention, tungsten powder with a D50 of 7.92 μm is used. Compared with the tungsten powder

[0021] commonly used in tungsten paste with a D50 lower than 2 μm, this large-particle-size tungsten powder can reduce the shrinkage rate of the printed film layer

[0022] and reduce the warpage degree of the ceramic base. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Figure 20 shows the side view of the laminated structure after printing in Example 9 and sintering at 1500 °C.

[0024] Figure 2 Figure 24 shows the cross-sectional view of the laminated structure after printing in Example 9 and sintering at 1500 °C. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0026] Example 1: A printed tungsten paste for HTCC ceramic substrate, comprising the following basic materials in mass percentage: 78% tungsten powder, 4% alumina ceramic powder, 18% organic carrier; it also includes iron-nickel powder and hydrogenated castor oil. The mass of the iron-nickel powder is 0.5% of the mass of the basic materials, and the mass of the hydrogenated castor oil is 0.3% of the mass of the basic materials.

[0027] The particle size of the tungsten powder conforms to a normal distribution, with D50 being 7.92 μm, D90 being 16.00 μm, and the tapped density being 8.26 g / cm 3 . The particle size of the iron-nickel powder conforms to a normal distribution, with D50 being 1 μm, and the mass ratio of iron to nickel in the iron-nickel powder being 1:1. The bulk density of the alumina ceramic powder is 1.8 g / cm 3 . The organic carrier is composed of resin ethyl cellulose and organic solvent terpineol in a mass ratio of 10:85, and the molecular weight of ethyl cellulose is 380,000 - 430,000.

[0028] Example 2: A printed tungsten paste for HTCC ceramic substrate, comprising base materials in the following mass percentages: 78% tungsten powder, 8% alumina ceramic powder, 14% organic carrier; also including iron-nickel powder and hydrogenated castor oil, where the mass of the iron-nickel powder is 1% of the mass of the base materials, and the mass of the hydrogenated castor oil is 0.4% of the mass of the base materials.

[0029] The particle size of the tungsten powder conforms to a normal distribution, with D50 being 7.92 μm, D90 being 16.00 μm, and the tapped density being 8.26 g / cm 3 . The particle size of the iron-nickel powder conforms to a normal distribution, with D50 being 1.2 μm, and the mass ratio of iron to nickel in the iron-nickel powder being 1:1. The bulk density of the alumina ceramic powder is 1.9 g / cm 3 . The organic carrier is composed of resin ethyl cellulose and organic solvent terpineol in a mass ratio of 11:86, and the molecular weight of the ethyl cellulose is 380,000 - 430,000.

[0030] Example 3: A printed tungsten paste for HTCC ceramic substrate, comprising base materials in the following mass percentages: 82% tungsten powder, 4% alumina ceramic powder, 14% organic carrier; also including iron-nickel powder and hydrogenated castor oil, where the mass of the iron-nickel powder is 3% of the mass of the base materials, and the mass of the hydrogenated castor oil is 0.5% of the mass of the base materials.

[0031] The particle size of the tungsten powder conforms to a normal distribution, with D50 being 7.92 μm, D90 being 16.00 μm, and the tapped density being 8.26 g / cm 3 . The particle size of the iron-nickel powder conforms to a normal distribution, with D50 being 1.5 μm, and the mass ratio of iron to nickel in the iron-nickel powder being 1:1. The bulk density of the alumina ceramic powder is 2.0 g / cm 3 . The organic carrier is composed of resin ethyl cellulose and organic solvent terpineol in a mass ratio of 13:87, and the molecular weight of the ethyl cellulose is 380,000 - 430,000.

[0032] Example 4: A printed tungsten paste for HTCC ceramic substrate, comprising base materials in the following mass percentages: 80% tungsten powder, 6% alumina ceramic powder, 14% organic carrier; also including iron-nickel powder and hydrogenated castor oil, where the mass of the iron-nickel powder is 5% of the mass of the base materials, and the mass of the hydrogenated castor oil is 0.6% of the mass of the base materials.

[0033] The particle size of the tungsten powder conforms to a normal distribution, with D50 being 7.92 μm, D90 being 16.00 μm, and the tapped density being 8.26 g / cm 3 . The particle size of the iron-nickel powder conforms to a normal distribution, with D50 being 1.8 μm, and the mass ratio of iron to nickel in the iron-nickel powder being 1:1. The bulk density of the alumina ceramic powder is 2.2 g / cm 3The organic carrier is composed of resin ethyl cellulose and organic solvent terpineol in a mass ratio of 14:89, and the molecular weight of ethyl cellulose is 380,000 - 430,000.

[0034] Example 5: A printed tungsten paste for HTCC ceramic substrate, comprising the following basic materials in mass percentages: 79% tungsten powder, 4% alumina ceramic powder, 17% organic carrier; also including iron-nickel powder and hydrogenated castor oil. The mass of iron-nickel powder is 0.5% of the mass of the basic materials, and the mass of hydrogenated castor oil is 0.3% of the mass of the basic materials.

[0035] The particle size of the tungsten powder conforms to a normal distribution, with D50 being 7.92 μm, D90 being 16.00 μm, and the tapped density being 8.26 g / cm 3 The particle size of the iron-nickel powder conforms to a normal distribution, with D50 being 2 μm, and the mass ratio of iron to nickel in the iron-nickel powder being 1:1. The bulk density of the alumina ceramic powder is 2.3 g / cm 3 The organic carrier is composed of resin ethyl cellulose and organic solvent terpineol in a mass ratio of 15:90, and the molecular weight of ethyl cellulose is 380,000 - 430,000.

[0036] Example 6: A preparation method of a printed tungsten paste for HTCC ceramic substrate, comprising the following steps: Preparation of the organic carrier: According to the organic carrier formula in Example 1, stir and completely dissolve it directly in a 65°C water bath, and cool to room temperature to obtain the organic carrier;

[0037] Preparation of the tungsten paste precursor: Take the organic carrier, tungsten powder, iron-nickel powder, alumina ceramic powder and hydrogenated castor oil according to the formula in Example 1, and stir until it becomes a paste state without powder dropping to obtain the tungsten paste precursor;

[0038] Rolling treatment: Use a three-roll mill to roll the tungsten paste precursor. First, pre-roll for 2 minutes under the conditions of a feed port gap of 170 μm, a discharge port gap of 170 μm and a rotation speed of 170 r / min; then adjust the feed port gap to 85 μm, the discharge port gap to 42 μm and roll 3 times at a rotation speed of 170 r / min; then adjust the feed port gap to 42 μm, the discharge port gap to 21 μm and roll 3 times at a rotation speed of 170 r / min; finally, adjust the feed port gap to 21 μm, the discharge port gap to 10 μm and roll 3 times at a rotation speed of 170 r / min to obtain the finished product.

[0039] Example 7: A preparation method of a printed tungsten paste for HTCC ceramic substrate, comprising the following steps: Preparation of the organic carrier: According to the organic carrier formula in Example 3, stir and completely dissolve it directly in a 68°C water bath, and cool to room temperature to obtain the organic carrier;

[0040] Preparation of tungsten paste precursor: Take the organic carrier, tungsten powder, iron-nickel powder, alumina ceramic powder and hydrogenated castor oil according to the formula of Example 3, and stir until it becomes a paste state without powder dropping to obtain the tungsten paste precursor;

[0041] Rolling treatment: Use a three-roll mill to roll the tungsten paste precursor. First, pre-roll for 2 minutes under the conditions of a feed port gap of 175 μm, a discharge port gap of 175 μm and a rotation speed of 175 r / min; then adjust the feed port gap to 88 μm, the discharge port gap to 43 μm and roll 3 times at a rotation speed of 175 r / min; then adjust the feed port gap to 43 μm, the discharge port gap to 22 μm and roll 3 times at a rotation speed of 175 r / min; finally, adjust the feed port gap to 22 μm, the discharge port gap to 11 μm and roll 3 times at a rotation speed of 175 r / min to obtain the finished product.

[0042] Example 8: A preparation method of printed tungsten paste for HTCC ceramic substrate, comprising the following steps: Preparation of organic carrier: According to the organic carrier formula of Example 5, stir and completely dissolve it directly in a 70 °C water bath, and cool to room temperature to obtain the organic carrier;

[0043] Preparation of tungsten paste precursor: Take the organic carrier, tungsten powder, iron-nickel powder, alumina ceramic powder and hydrogenated castor oil according to the formula of Example 5, and stir until it becomes a paste state without powder dropping to obtain the tungsten paste precursor;

[0044] Rolling treatment: Use a three-roll mill to roll the tungsten paste precursor. First, pre-roll for 2 minutes under the conditions of a feed port gap of 180 μm, a discharge port gap of 180 μm and a rotation speed of 180 r / min; then adjust the feed port gap to 90 μm, the discharge port gap to 45 μm and roll 3 times at a rotation speed of 180 r / min; then adjust the feed port gap to 45 μm, the discharge port gap to 23 μm and roll 3 times at a rotation speed of 180 r / min; finally, adjust the feed port gap to 23 μm, the discharge port gap to 12 μm and roll 3 times at a rotation speed of 180 r / min to obtain the finished product.

[0045] Example 9: Refer to Example 8 and adjust the mass of iron-nickel powder to 3% of the mass of the base material.

[0046] Example 10: Refer to Example 8 and adjust the mass of iron-nickel powder to 5% of the mass of the base material. Comparative Example 1: Refer to Example 8 and do not add iron-nickel powder.

[0047] The slurries of Examples 8 - 10 and Comparative Example 1 were respectively printed on 96% alumina green ceramic chips and sintered. The holding temperatures were 1500°C, 1525°C, 1550°C, and 1575°C respectively, and the holding time was 90 min. The sheet resistance of the film layer was measured using a four-probe method. The sheet resistances of the film layers after co-firing the slurries of Examples 8 - 10 and Comparative Example 1 with the ceramic substrate are shown in Table 2. It shows that when the sintering temperature is fixed, the addition of iron-nickel powder can effectively reduce the sheet resistance of the film layer. In addition, the sheet resistance of the film layer of Example 8 after sintering at 1500°C is 11.4% lower than that of Comparative Example 1 after sintering at 1575°C. This is attributed to the fact that the addition of iron-nickel powder reduces the activation energy of tungsten sintering, resulting in a lower sheet resistance of the tungsten film layer at a lower sintering temperature. On the other hand, when the addition amount of iron-nickel powder exceeds a certain value, although the sintering temperature and the sheet resistance of the film layer can also be reduced, the improvement effect becomes weaker. This is because the conductivity of the iron-nickel material is lower than that of tungsten, and excessive addition will hinder the formation of the sintering neck of tungsten particles, weakening the effect of activated sintering and resulting in a weaker improvement effect. The slurry of Example 9 was first printed on the alumina green ceramic chip, and then 6 printed green ceramic chips were taken and laminated. Finally, it was sintered at 1500°C. Its side view is as shown in Figure 1 , after multi-layer lamination and co-firing, the ceramic did not show obvious warping; its cross-section is as shown in Figure 2 . The alumina substrate and the tungsten conductive layer are closely and alternately distributed, and each layer is flat without breakage and deformation, and the tungsten grains are in close contact, which can ensure the conductivity of the internal electrode.

[0048] Table 1 Sheet resistances of the film layers after co-firing the slurries of Examples 8 - 10 and Comparative Example 1 with the ceramic substrate

[0049]

[0050] The slurries of Examples 6 and 7 were respectively printed on 96% alumina green ceramic chips and sintered. The holding temperature was 1500°C and the holding time was 90 min. The sheet resistance of the film layer was measured using a four-probe method. The sintering properties of the slurries of Examples 6 and 7 after co-firing with the ceramic substrate are shown in Table 2.

[0051] Table 2 Sintering properties of the co-fired ceramics of Examples 6 and 7

[0052]

[0053] The described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

Claims

1. A printing tungsten paste for HTCC ceramic substrate, characterized in that: It includes the following basic materials in percentage by mass: 78-82% of tungsten powder, 4-8% of alumina ceramic powder, and 14-18% of organic carrier; it also includes iron-nickel powder and hydrogenated castor oil, the mass of the iron-nickel powder is 0.5-5% of the mass of the basic material, and the mass of the hydrogenated castor oil is 0.3-0.6% of the mass of the basic material.

2. The printing tungsten paste for HTCC ceramic substrate according to claim 1, characterized in that: The particle size of the tungsten powder conforms to the normal distribution, with D50 of 7.92 μm, D90 of 16.00 μm, and tap density of 8.26 g / cm 3 .

3. The printing tungsten paste for HTCC ceramic substrate according to claim 1, characterized in that: The particle size of the iron-nickel powder conforms to the normal distribution, D50 is 1-2 μm, and the mass ratio of iron to nickel in the iron-nickel powder is 1:

1.

4. The printing tungsten paste for HTCC ceramic substrate according to claim 1, characterized in that: The volume density of the alumina ceramic powder is 1.8-2.3 g / cm 3 .

5. The printing tungsten paste for HTCC ceramic substrate according to claim 1, characterized in that: The organic carrier is composed of resin ethyl cellulose and organic solvent pinene alcohol in a mass ratio of 10-15:85-90, and the molecular weight of the ethyl cellulose is 380,000-430,000.

6. A method for preparing a printed tungsten paste for a HTCC ceramic substrate as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparation of organic carrier: According to the organic carrier formula, stir and completely dissolve in a water bath at 65-70°C, and cool to room temperature to obtain an organic carrier; (2) Preparation of tungsten slurry precursor: Take organic carrier, tungsten powder, iron-nickel powder, alumina ceramic powder and hydrogenated castor oil according to the formula, stir until it becomes a paste state without falling powder, and obtain tungsten slurry precursor; (3) Rolling treatment: The tungsten slurry precursor of step (2) is rolled using a three-roll rolling mill. First, the feed inlet gap is 170-180 μm, the discharge outlet gap is 170-180 μm and the rotation speed is 170-180 r / min, and pre-rolling is performed for 2 min; then the feed inlet gap is adjusted to 85-90 μm, the discharge outlet gap is 42-45 μm, and the rotation speed is 170-180 r / min for 3 times; then the feed inlet gap is adjusted to 42-45 μm, the discharge outlet gap is 21-23 μm, and the rotation speed is 170-180 r / min for 3 times; finally, the feed inlet gap is adjusted to 21-23 μm, the discharge outlet gap is 10-12 μm, and the rotation speed is 170-180 r / min for 3 times to obtain a finished product.

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