A ceramic package base

Abstract

The present invention discloses a ceramic packaging base, which relates to the technical field of electronic component packaging. The present invention provides a ceramic packaging base, comprising a ceramic substrate and an electrode layer; the electrode layer includes a gold layer, a Ni-Co alloy layer, and a tungsten layer or a molybdenum layer; the Ni-Co alloy layer is located between the gold layer and the tungsten layer or the molybdenum layer; the tungsten layer or the molybdenum layer is adjacent to the ceramic substrate; wherein, in the Ni-Co alloy layer, the proportion of grain boundaries with an angle of 2°-15° in all grain boundaries is 25%-35%. By using a Ni-Co alloy layer to replace the single nickel layer in the electrode layer of the current packaging base and controlling the proportion of grain boundaries with an angle of 2°-15° in the alloy layer within 25%-35%, the present invention can inhibit the precipitation of nickel elements on the surface of the gold layer and effectively improve the lead performance between the gold wire and the electrode layer.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic component packaging, and in particular to a ceramic packaging base. Background Art

[0002] In recent years, with the rapid development of fields such as big data, artificial intelligence, Internet of Things, and 5G, electronic components such as quartz crystals for resonators, tuning forks, and TOF components for 3D depth camera modules have been widely used in various electronic devices. In order to ensure that the electronic components are not affected by the external environment, a ceramic packaging base is required for packaging. During the packaging process, gold wires need to be led out from the electronic components and the gold wires are pressure-welded to the electrode layer of the packaging base, so as to realize the electrical connection between the electronic components and the packaging base.

[0003] Currently, the electrode layer usually consists of multiple metal layers, including a tungsten layer or a molybdenum layer, a nickel layer, and a gold layer from bottom to top; however, on the existing packaging base electrode layer, nickel precipitates too much on the surface of the gold layer, resulting in frequent poor lead connection between the gold wire and the electrode layer, affecting the normal use of electronic devices. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a ceramic packaging base. The ceramic packaging base provided by the present invention can inhibit the precipitation of nickel elements on the surface of the gold layer and effectively improve the lead performance between the gold wire and the electrode layer.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a ceramic packaging base, including a ceramic substrate and an electrode layer; the electrode layer includes a gold layer, a Ni-Co alloy layer, and a tungsten layer or a molybdenum layer; the Ni-Co alloy layer is located between the gold layer and the tungsten layer or the molybdenum layer; the tungsten layer or the molybdenum layer is adjacent to the ceramic substrate; wherein, in the Ni-Co alloy layer, the proportion of grain boundaries with an angle of 2°-15° in all grain boundaries is 25%-35%.

[0006] In the present invention, a Ni-Co alloy layer is adopted to replace the single nickel layer in the electrode layer of the current encapsulation base, and the proportion of grain boundaries with an angle of 2° - 15° in the alloy layer is controlled within 25% - 35%, thereby inhibiting the precipitation of nickel elements on the surface of the gold layer and effectively improving the lead performance between the gold wire and the electrode layer. During co-deposition, since the atomic radius of cobalt is larger than that of nickel, lattice distortion will occur, resulting in the cumulative generation of small-angle grain boundaries. By controlling the proportion of grain boundaries with an angle of 2° - 15° in all grain boundaries to be 25% - 35%, the grains of the Ni-Co alloy layer can be refined, thereby improving the compactness of the Ni-Co alloy layer and inhibiting the precipitation of nickel from the surface of the gold layer. The higher the purity of the gold layer, the better its bonding effect with the gold wire, and the lead performance between the gold wire and the electrode layer can be greatly improved. When the proportion of grain boundaries with an angle of 2° - 15° in all grain boundaries < 25%, the precipitation of nickel from the surface of the gold layer cannot be effectively inhibited, and the improvement of the lead performance between the gold wire and the electrode layer is not obvious. When the proportion of grain boundaries with an angle of 2° - 15° in all grain boundaries > 35%, it means that the proportion of sub-grain boundaries in the coating is relatively high. At this time, the dislocation density in the coating is large, resulting in an increase in the resistance to dislocation movement, which will further improve the strength of the coating, but at the same time, the plasticity and toughness of the coating become poor, and stress concentration is likely to occur inside the coating, thereby reducing the corrosion resistance of the coating and ultimately decreasing the service life of the encapsulation base.

[0007] The method adopted by the present invention to obtain the grain boundary angle is as follows: Use the EBSD (Electron Backscatter Diffraction Analysis) method to test the grain boundary angle information: metallographic sample preparation → sample polishing → place the sample in a scanning electron microscope for scanning and taking pictures → calibrate the Kikuchi pattern of the pictures → start EBSD testing when the target calibration rate (above 90) is reached → obtain the test data and perform software analysis to obtain the grain boundary angle information.

[0008] Preferably, in the Ni-Co alloy layer, the proportion of grain boundaries with an angle of 2° ≤ angle < 7° in all grain boundaries is 8% - 15%, and the proportion of grain boundaries with an angle of 7° ≤ angle ≤ 15° in all grain boundaries is 15% - 20%.

[0009] After a large number of experimental explorations, the inventor found that when the small-angle grain boundaries in the refinement range are not within the specified range, that is, when the proportion of grain boundaries with an angle of 2° ≤ angle < 7° in all grain boundaries is not 8% - 15% and the proportion of grain boundaries with an angle of 7° ≤ angle ≤ 15° in all grain boundaries is not 15% - 20%, the lead performance will decrease.

[0010] Preferably, in the Ni-Co alloy layer, the average diameter D50 of the grain boundaries with an angle of 2° - 15° ≤ 4.5 μm.

[0011] Preferably, in the Ni-Co alloy layer, the mass percentage of Ni element is 70wt%-80wt%, and the mass percentage of Co element is 20wt%-30wt%. The Ni-Co alloy layer is composed of Ni element and Co element.

[0012] Preferably, the surface roughness of the Ni-Co alloy layer is ≥0.5μm, the surface roughness of the gold layer is ≥0.5μm, and the precipitation amount of nickel element on the surface of the gold layer is ≤1.5wt%.

[0013] After a large number of experimental explorations, the inventors found that due to the presence of cobalt element, the surface of the Ni-Co alloy layer is microscopically an uneven structure with approximate spherical shape and macroscopically flat. When the surface roughness of the Ni-Co alloy layer is ≥0.5μm, the physical and mechanical biting effect between the gold wire and the electrode layer is enhanced, and the lead performance is improved. Since the thickness of the gold layer is very thin, the overall morphology of the gold layer still presents that of the Ni-Co alloy layer, so that the surface roughness of the gold layer is ≥0.5μm.

[0014] Preferably, the thickness of the tungsten layer or molybdenum layer is 5μm-50μm, the thickness of the Ni-Co alloy layer is 2-5μm, and the thickness of the gold layer is 0.5-0.8μm.

[0015] Furthermore, the ceramic packaging base further includes a frame disposed on the upper surface of the ceramic substrate. The frame and the ceramic substrate form a receiving cavity for receiving electronic components; an inner electrode layer is provided in the receiving cavity, and the electronic components are electrically connected to the inner electrode layer through gold wires; an outer electrode layer for electrically connecting to external devices is formed on the lower surface of the ceramic substrate.

[0016] Furthermore, the present invention provides a preparation method of the ceramic packaging base, including the following steps:

[0017] (1) Processing the ceramic slurry into a ceramic green body;

[0018] (2) Processing the ceramic green body into the required structure according to the structural requirements of different layers of the ceramic substrate and the pattern requirements of the electrode layer, and printing the tungsten layer or molybdenum layer;

[0019] (3) Stacking the ceramic green bodies obtained in multiple steps (2) to form a ceramic packaging base green body, and then degumming and sintering the ceramic packaging base green body to obtain a semi-finished ceramic packaging base;

[0020] (4) Electroplating the Ni-Co alloy layer and the gold layer on the tungsten layer or molybdenum layer of the semi-finished ceramic packaging base in sequence to obtain the ceramic packaging base.

[0021] Preferably, in the step (4), the Ni-Co alloy layer is prepared by an electroplating process, and the electroplating process includes: cleaning of the semi-finished ceramic package base → activation → electroplating of Ni-Co alloy → cleaning → drying. The electroplating conditions for the Ni-Co alloy layer are as follows: the pH value is 3-6, the current density is 2-3 A / dm 2 , and the electroplating temperature is 30-60 °C.

[0022] The inventors found that the properties of the Ni-Co alloy layer are affected by the electroplating solution formulation and electroplating process conditions. Under the above conditions, the performance of the Ni-Co alloy layer is better.

[0023] Preferably, in the step (4), the Ni-Co alloy electroplating solution used for electroplating the Ni-Co alloy layer includes the following components: nickel source, cobalt source, conductive salt, buffer; wherein, the concentration of the nickel source is 80 g / L - 100 g / L, the concentration of the cobalt source is 15 g / L - 60 g / L, the concentration of the conductive salt is 10 g / L - 20 g / L, and the concentration of the buffer is 20 g / L - 40 g / L.

[0024] Preferably, the nickel source is at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel sulfamate, the cobalt source is at least one of cobalt sulfamate, cobalt sulfate, cobalt chloride, the conductive salt is at least one of nickel chloride, sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, and the buffer is at least one of boric acid, disodium hydrogen phosphate, sodium citrate.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention replaces the single nickel layer in the electrode layer of the current package base with a Ni-Co alloy layer, and controls the proportion of grain boundaries with an angle of 2° - 15° in the alloy layer within 25% - 35%, thereby inhibiting the precipitation of nickel elements on the surface of the gold layer and effectively improving the lead performance between the gold wire and the electrode layer. Detailed Embodiments

[0026] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. In the embodiments, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0027] Examples 1-9 and Comparative Examples 1-3

[0028] Example 1

[0029] A preparation method of a ceramic package base according to an embodiment of the present invention includes the following steps:

[0030] (1) Processing alumina ceramic slurry into a ceramic green body;

[0031] (2) Print a tungsten electrode layer on the green ceramic body to form an electrode layer pattern with pads of 0.8 mm * 0.9 mm.

[0032] (3) Stack, debind, and sinter the green ceramic body printed with the electrode layer pattern to obtain a semi-finished sample.

[0033] (4) Electroplate a Ni-Co alloy layer and a gold layer on the tungsten layer of the semi-finished sample in sequence to obtain the ceramic package base.

[0034] During the preparation process of the ceramic package base provided by the embodiments and comparative examples of the present invention, other aspects such as the structure of the package base do not affect the performance of the present invention and will not be explored in detail in the present invention. During the preparation process of the ceramic package base provided by the embodiments and comparative examples of the present invention, the thickness of the tungsten layer or molybdenum layer is 40 μm; the thickness of the Ni-Co alloy layer is 3 μm; the thickness of the gold layer is 0.7 μm. The preparation method of the ceramic package base provided by the embodiments and comparative examples of the present invention is the same as that of Example 1, except that the electroplating conditions, electroplating solution formula, Co element proportion, grain boundary proportion, average diameter of grains with 2° - 15° grain boundaries, surface roughness, and nickel element precipitation amount on the gold layer of the electroplated Ni-Co alloy layer in step (4) are different. The specific parameters are shown in Table 1-2.

[0035] Testing process: Lead performance, the passing requirement is that the lead failure rate ≤ 0.01%, and the testing method is to perform lead soldering under an ultrasonic power of 30 W and a pressure of 80 g; Corrosion resistance, the passing requirement is that no corrosion points are generated on the coating within 48 hours, and the testing method is to expose the product to a salt spray environment of 5% neutral sodium chloride solution for testing. The test results are shown in Table 3.

[0036] In the present invention, the proportion information and grain diameter information of grain boundaries at different angles in the Ni-Co alloy layer are obtained by EBSD; the content proportion of Ni element and Co element in the present invention is obtained by EDS; the roughness of the Ni-Co alloy layer and the gold layer in the present invention is obtained by a 3D laser microscope; the testing method for the precipitation amount of Ni element is: characterized by using AES (Auger electron spectroscopy), where the electron beam voltage is 5 kV and the electron beam current is 10 nA; detections are carried out before sputtering and after sputtering 5.5 nm respectively.

[0037] Table 1

[0038]

[0039]

[0040]

[0041] Table 2

[0042]

[0043]

[0044]

[0045] Table 3

[0046]

[0047] As can be seen from the above table, when Examples 1-5 explore that all parameters are within the scope defined by the claims of the present invention, the performance changes corresponding to different proportions of angular grain boundaries are studied. As the proportion of Co element increases, the proportion of 2°-15° grain boundaries increases, and the proportion of refined grain boundaries meets the defined range; the average diameter of the grains of the 2°-15° grain boundaries decreases, and the grain size continuously decreases; the surface roughness continuously increases; the Ni precipitation continuously decreases; the lead wire failure rates all meet the standards; the corrosion resistance all meets the standards.

[0048] Examples 6-7 explore that when the small-angle grain boundaries in the refinement range are not within the specified range, the lead wire performance will decrease, and the lead wire failure rate is 0.008, and the corrosion resistance all meets the standards.

[0049] Example 9 explores the changes in the lead wire performance and corrosion resistance when the average diameter of the grains of the small-angle grain boundaries is not within the scope defined by the claims of the present invention. The average diameter of the grains of the small-angle grain boundaries is not within the specified range, resulting in a lead wire failure rate of 0.01 for Example 9 (with too large average grains), and the surface roughness is 0.48, while the corrosion resistance meets the standards.

[0050] In Comparative Example 1, when the proportion of small-angle grain boundaries < the lower limit value, the grains are large, the surface roughness becomes smaller, the Ni precipitation in the gold layer exceeds the standard, the lead wire failure rate does not meet the standard, and the corrosion resistance meets the standard. In Comparative Example 2, when the proportion of small-angle grain boundaries > the upper limit value, the grains are small, the surface roughness becomes larger, the Ni precipitation in the gold layer meets the standard, the lead wire failure rate is 0, and the corrosion resistance does not meet the standard. In Comparative Example 3, for the pure Ni coating, the proportion of small-angle grain boundaries is only 19%, the average grain diameter is 5 μm, the roughness of the Ni layer is 0.41 μm, the Ni precipitation amount in the gold layer reaches 2.8 wt%, the lead wire failure rate reaches 0.3%, and the corrosion resistance meets the standard.

[0051] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A ceramic packaging base, characterized in that, It includes a ceramic substrate and an electrode layer; the electrode layer includes a gold layer, a Ni-Co alloy layer, and a tungsten layer or a molybdenum layer; the Ni-Co alloy layer is located between the gold layer and the tungsten layer or the molybdenum layer; the tungsten layer or the molybdenum layer is adjacent to the ceramic substrate; wherein, in the Ni-Co alloy layer, the proportion of grain boundaries with an angle of 2°-15° in all grain boundaries is 25%-35%.

2. The ceramic package base according to claim 1, wherein, In the Ni-Co alloy layer, the proportion of grain boundaries with an angle of 2°≤angle<7° in all grain boundaries is 8%-15%, and the proportion of grain boundaries with an angle of 7°≤angle≤15° in all grain boundaries is 15%-20%.

3. The ceramic package base according to claim 1, characterized in that, In the Ni-Co alloy layer, the average diameter D50 of grain boundaries with an angle of 2°-15°≤4.5μm.

4. The ceramic package base according to claim 1, characterized in that, In the Ni-Co alloy layer, the mass percentage of Ni element is 70wt%-80wt%, and the mass percentage of Co element is 20wt%-30wt%.

5. The ceramic package base according to claim 1, wherein The surface roughness of the Ni-Co alloy layer≥0.5μm, the surface roughness of the gold layer≥0.5μm, and the precipitation amount of nickel element on the surface of the gold layer≤1.5wt%.

6. The ceramic package base according to claim 1, wherein The thickness of the tungsten layer or the molybdenum layer is 5μm-50μm, the thickness of the Ni-Co alloy layer is 2-5μm, and the thickness of the gold layer is 0.5-0.8μm.

7. A method for preparing a ceramic package base according to any one of claims 1-6, characterized in that, It includes the following steps: (1) Process the ceramic slurry into a ceramic green body; (2) According to the structural requirements of different-layer ceramic substrates and the pattern requirements of the electrode layer, process the ceramic green body into the required structure and print the tungsten layer or the molybdenum layer; (3) Stack the ceramic green bodies obtained in multiple steps (2) to form a ceramic package base green body, and then degrease and sinter the ceramic package base green body to obtain a semi-finished ceramic package base; (4) Electroplate the Ni-Co alloy layer and the gold layer on the tungsten layer or the molybdenum layer of the semi-finished ceramic package base in sequence to obtain the ceramic package base.

8. The preparation method of the ceramic packaging base according to claim 7, characterized in that, In the step (4), the electroplating conditions for the Ni-Co alloy layer are as follows: the pH value is 3 - 6, the current density is 2 - 3 A / dm 2 , and the electroplating temperature is 30 - 60 °C.

9. The preparation method of the ceramic package base according to claim 7, characterized in that, In the step (4), the Ni-Co alloy electroplating solution used for electroplating the Ni-Co alloy layer includes the following components: nickel source, cobalt source, conductive salt, buffer; wherein, the concentration of the nickel source is 80g / L-100g / L, the concentration of the cobalt source is 15g / L-60g / L, the concentration of the conductive salt is 10g / L-20g / L, and the concentration of the buffer is 20g / L-40g / L.

10. The preparation method of the ceramic package base according to claim 9, characterized in that, The nickel source is at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel sulfamate, the cobalt source is at least one of cobalt sulfamate, cobalt sulfate, cobalt chloride, the conductive salt is at least one of nickel chloride, sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, and the buffer is at least one of boric acid, disodium hydrogen phosphate, sodium citrate.

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