Method for improving color difference of appearance of electroplated Kovar metal packaging shell

Abstract

The invention discloses a method for improving the appearance color difference of a kovar metal packaging shell after electroplating, and belongs to the technical field of metal packaging shell manufacturing. The method comprises the following steps: inspecting supplied materials of the kovar alloy lead and the chassis, and performing sand blasting pretreatment on the supplied materials under optimized sand blasting pressure, angle, distance and belt speed by adopting an abrasive medium with a specific particle size; then carrying out post-treatment such as soaking, oil removal, water washing and drying; and sequentially carrying out conventional decarburization, oxidation, matched sealing and electroplating procedures. According to the method, by cooperatively controlling the sand blasting parameters, a uniform and appropriate microscopic rough structure is formed on the surfaces of the lead and the chassis, the electroplating defect caused by abnormal growth of crystal grains in subsequent high-temperature treatment is effectively prevented, and meanwhile, the reliability of a sealing interface is guaranteed. According to the method, the appearance uniformity and the qualification rate of the product are remarkably improved, the process is simple, compatibility with an existing production line is good, and application and popularization are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of metal packaging shell technology, and particularly relates to a method for improving the appearance color difference of Kovar metal packaging shell after electroplating. Background Technology

[0002] Metal enclosures provide mechanical support, sealing protection, and electromagnetic shielding for electronic components, and their appearance quality directly affects product image and customer evaluation. Kovar alloy (iron-nickel-cobalt alloy) is widely used in the manufacture of high-end metal enclosures because its coefficient of thermal expansion matches that of ceramics and glass.

[0003] Traditional Kovar metal package manufacturing processes typically include: pretreatment of leads and chassis (cleaning, decarburization, oxidation), followed by mating and sealing, and finally electroplating (such as nickel or gold plating). However, in production practice, it has been found that Kovar metal packages manufactured using this traditional process are prone to an appearance defect on the lead and shell surfaces after electroplating, known as "ice flower" or "snowflake-like bright spots." This defect manifests microscopically as uneven bright spots, significantly different from normal areas, such as... Figure 2 As shown, this seriously affects the consistency and aesthetics of the product's appearance, becoming a bottleneck restricting the improvement of the quality of high-end products.

[0004] In the packaging industry, Kovar materials are traditionally processed by avoiding sandblasting of incoming materials. This is because improper sandblasting processes can introduce problems such as micro-stress, excessive surface roughness, or abrasive residue, which may negatively impact key reliability indicators such as seal strength and hermeticity. Therefore, the industry urgently needs an innovative method that can fundamentally improve the surface condition of Kovar substrates and solve the aforementioned electroplating appearance defects without compromising product reliability. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for improving the color difference in the appearance of Kovar metal packaging shells after electroplating. This invention involves targeted sandblasting of the leads and chassis upon arrival, disrupting the original interface and improving the surface condition of the material. This results in no "snowflake"-like bright spots appearing after electroplating, without affecting other product performance characteristics.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for improving the appearance color difference of Kovar metal packaging shell after electroplating, comprising the following steps: S1. Incoming material inspection: Visually inspect the incoming lead wires and chassis made of Kovar alloy material; S2. Sandblasting: Fix the lead wire and the chassis separately, and perform sandblasting on each. The medium used for sandblasting is an abrasive medium with a particle size range of 120-320 mesh. The sandblasting pressure is 0.08-0.5MPa, the sandblasting angle is 60-80°, the sandblasting distance between the spray gun and the workpiece is 80-160mm, and the conveyor belt speed of the sandblasting machine is 500-2000 mm / min. S3. Post-sandblasting treatment: Soak, degrease, wash and dry the sandblasted lead wires and chassis. S4. Pre-treatment and sealing: The lead wire and chassis after step S3 are decarburized, oxidized and matched for sealing treatment to obtain a sealed semi-finished product. S5. Electroplating: Electroplating is performed on the sealed semi-finished product. S6. Finished product inspection.

[0008] Furthermore, in step S2, the abrasive medium used for lead wire sandblasting is a mixed sand composed of 320-mesh glass microspheres and 180-mesh quartz sand in a mass ratio of 2:1; the abrasive medium used for chassis sandblasting is a mixed sand composed of 120-mesh quartz sand and 150-mesh quartz sand in a mass ratio of 1:1.

[0009] Furthermore, in step S2, the sandblasting pressure of the lead wire is 0.08-0.12 MPa, the sandblasting angle is 60-80°, and the belt speed is 800-1500 mm / min; the sandblasting pressure of the chassis is 0.3-0.5 MPa, the sandblasting angle is 60-80°, and the belt speed is 850-1600 mm / min.

[0010] Furthermore, in step S2, the sandblasting process is carried out using an automatic sandblasting device.

[0011] Furthermore, in step S2, the automatic sandblasting equipment is a conveyor-type automatic sandblasting machine.

[0012] Furthermore, in step S3, the degreasing is performed by ultrasonic degreasing, and the cleaning time is 15-30 minutes.

[0013] Furthermore, in step S4, the temperature of the matching and sealing is 900-1000℃, and the heat preservation time is 20-40 minutes.

[0014] Furthermore, in step S5, the electroplating process includes nickel plating and gold plating.

[0015] Secondly, the present invention provides a Kovar metal encapsulation shell, which is prepared using the processing method described in the present invention.

[0016] Furthermore, the surface plating of the Kovar metal package shell consists of a nickel layer and a gold layer from the inside out, with the nickel layer having a thickness of 4–15 μm and the gold layer having a thickness of 1.3–5.7 μm.

[0017] The Kovar metal package obtained by this invention meets the visual inspection requirements for metal packages in Appendix A of GJB2440B-2024 "General Specification for Hybrid Integrated Circuit Packages", and the airtightness test results are all ≤1×10 -3 Pa•cm 3 / s (A4 He), the metal layers are nickel and gold layers from the inside out; the thickness of each metal layer can be selected according to the actual situation. Specifically, the thickness of the nickel layer is 4 to 15 μm and the thickness of the gold layer is 1.3 to 5.7 μm.

[0018] In the sandblasting process described in this invention, the setting of each process parameter is based on the differentiated structural characteristics and functional requirements of the lead wire and the chassis: the lead wire structure is small and needs to maintain geometric accuracy; to avoid deformation or damage caused by sandblasting, its sandblasting pressure should be controlled in a low range, preferably 0.08-0.12 MPa; the chassis structure is thick and heavy with a large surface area, requiring the effectiveness and uniformity of the sandblasting process to be ensured, therefore a higher pressure can be used, preferably 0.3-0.5 MPa. The setting of the sandblasting distance is also based on similar considerations: too close a distance (e.g., <80 mm) can easily lead to excessive surface roughness or even damage; too far a distance (e.g., >160 mm) will result in insufficient sandblasting impact force, failing to effectively homogenize the surface microstructure. The preferred distance is 100-120 mm, within which the surface treatment effect can be guaranteed while avoiding workpiece damage.

[0019] This invention utilizes a specially formulated mixed abrasive medium and coordinates the sandblasting pressure, angle, distance, and conveyor belt speed to create a uniform and appropriately rough microstructure on the surface of the Kovar alloy leads and chassis. This surface condition, on the one hand, disrupts the defective structures at the original material interface that could induce abnormal grain growth during subsequent high-temperature processing, fundamentally preventing the formation of "snowflake-like bright spots." On the other hand, the resulting uniform roughness provides an optimized mechanical meshing basis for the subsequent sealing interface, while the appropriate roughness and controlled sandblasting process effectively avoid reliability issues such as decreased sealing strength and microleakage caused by surface damage, residual stress concentration, or abrasive embedding. Therefore, the sandblasting pretreatment process of this invention effectively eliminates appearance defects while ensuring the long-term reliability and sealing quality of the encapsulation shell.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are: 1. This invention introduces a sandblasting pretreatment step for incoming Kovar leads and chassis. Unlike conventional sandblasting in the packaging industry, which only removes burrs or surface contaminants, this invention uses a specific ratio of mixed sand and optimized combinations of sandblasting pressure, angle, belt speed, and distance parameters to break the original surface grain boundary state of the Kovar material, forming a uniform and controllable micro-rough structure. This treatment not only effectively prevents the "snowflake-like bright spot" defect caused by abnormal grain growth during subsequent high-temperature processing, but also improves the mechanical interlocking and metallurgical bonding effect of the sealing interface by forming a suitable sealing interface roughness. This significantly improves the appearance pass rate to over 99% while ensuring key reliability indicators such as sealing strength and airtightness.

[0021] 2. In this invention, both the lead wires and the chassis are sandblasted using mixed sand, which can balance sandblasting efficiency and surface quality. Coarse sand can effectively remove surface dirt, while fine sand acts as a buffer and repairs surface defects such as scratches and pits, so that the surface after sandblasting meets the appearance and cleanliness requirements of Kovar metal packaging shell.

[0022] 3. By sandblasting the incoming lead wires and chassis, this invention can effectively solve common processing defects such as burrs and dirt, significantly reduce subsequent production costs, and ensure that the surface condition of the packaged shell is relatively stable, thus guaranteeing the consistency of batch packaging.

[0023] 4. The technical solution of the present invention can be adapted to the existing Kovar metal packaging shell production line in the advanced packaging field without the need to improve the existing sealing and electroplating processes. The technical solution has strong scalability and can cover all Kovar metal packaging shells, thereby improving the appearance quality of products. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of a method for improving the color difference in the appearance of Kovar metal packaging shells after electroplating, according to the present invention.

[0025] Figure 2 This is a comparison image (100x magnification) of the surface microstructure of Kovar metal packaging shells after electroplating using the traditional process (with ice-like patterns) and the method of this invention (qualified).

[0026] Figure 3 The images show the microstructure of the Kovar metal packaging shell after electroplating, obtained using the method of Example 1 of this invention (100x, 500x, and 1000x magnification from left to right).

[0027] Figure 4 The microscopic morphology of the Kovar metal packaging shell after electroplating is shown in Comparative Example 3 (unsandblasted) (100x, 500x, and 1000x magnification from left to right). Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0031] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] This invention provides a method for improving the color difference in the appearance of Kovar metal packaging shells after electroplating. The core of this method lies in introducing sandblasting pretreatment of the leads and chassis at the very beginning of the traditional process flow. By optimizing the sandblasting medium and process parameters, the surface condition of the substrate is fundamentally improved to prevent subsequent electroplating defects. The overall process of this method can be referred to... Figure 1 The process flow diagram shown is shown.

[0033] Example 1 A method for improving the color difference in the appearance of Kovar metal packaging shells after electroplating, the specific steps of which are as follows: S1. Incoming material inspection: Visually inspect Kovar alloy leads and chassis to ensure that the surface is free of obvious dirt, oil stains and serious scratches or other abnormalities.

[0034] S2, Sandblasting treatment: Lead wire blasting: A mixed sand medium of 320-mesh glass microspheres and 180-mesh quartz sand at a mass ratio of 2:1 is used. The lead wire is fixed on a special fixture and placed in a conveyor-type automatic sandblasting machine. The sandblasting pressure is set to 0.08 MPa, the sandblasting angle to 70°, the belt speed of the automatic sandblasting machine to 1000 mm / min, and the sandblasting distance to approximately 100 mm.

[0035] Chassis sandblasting: Use a mixture of 120-mesh and 150-mesh quartz sand in a 1:1 mass ratio as the medium. Fix the chassis, set the sandblasting pressure to 0.35MPa, the sandblasting angle to 70°, the conveyor belt speed to 1200 mm / min, and the sandblasting distance to approximately 120mm.

[0036] S3. Post-sandblasting treatment: After sandblasting, the lead wire and chassis are first soaked in chemical degreasing solution (alkaline solution) for 2 hours to initially remove the abrasive dust and oil stains attached to the surface. Then, ultrasonic degreasing is performed for 30 minutes, followed by ultrasonic water washing and pure water rinsing. Finally, they are dried in a 100℃ oven for 35 minutes.

[0037] Analysis suggests that after this sandblasting process, the original rolling texture, micro-defects, and uneven oxide film on the Kovar alloy surface are effectively homogenized, forming a uniform and controllable micro-roughness morphology. The sandblasted surface consists of uniform micro-pits, and the surface energy distribution tends to be consistent; while the unblasted surface shows obvious original grain boundaries and micro-inhomogeneous regions. This homogenized surface state destroys the preferential nucleation sites for abnormal grain growth, which is considered the fundamental reason for preventing the "snowflake-like bright spot" defect during subsequent high-temperature sealing and electroplating processes.

[0038] S4. Pretreatment and Sealing: The dried leads and chassis undergo routine decarburization and oxidation treatment. Subsequently, a conventional matching sealing process is used, and the leads and chassis are held at 950°C for 30 minutes in a nitrogen atmosphere to seal them together with glass solder, forming a semi-finished package shell.

[0039] S5. Electroplating process: The sealed semi-finished product is subjected to conventional electroplating. After chemical degreasing, electrolytic degreasing, pickling, and activation, a nickel layer is first electroplated to a thickness of about 8μm, followed by a gold layer electroplated to a thickness of about 2.5μm. Finally, post-plating cleaning and drying are performed.

[0040] S6. Finished product inspection: Visual inspection shall be carried out in accordance with the requirements of Appendix A of GJB2440B-2024 "General Specification for Hybrid Integrated Circuit Housing" and the airtightness shall be tested.

[0041] Examples 2-7 and Comparative Examples 1-3 Examples 2 to 7 follow essentially the same steps as Example 1, with only minor adjustments to individual parameters such as blasting pressure, blasting distance, or blasting angle. Specific parameters are shown in Table 1.

[0042] Comparative Examples 1 and 2 were also sandblasted, but with sandblasting pressures significantly lower than those of the present invention.

[0043] Comparative Example 3 does not undergo any sandblasting treatment and is produced directly according to the traditional process (S4, S5, and S6 are performed directly after S1).

[0044] All other unlisted process parameters in all embodiments and comparative examples are set according to Example 1 or as is customary in the art.

[0045] Table 1: Process parameters and performance test results of the examples and comparative examples

[0046] Note: The yield rate is calculated as the percentage of qualified products without snowflake-like bright spots out of the total number of products. The airtightness standard is ≤1×10⁻⁶. - ³ Pa·cm³ / s (A₄He).

[0047] Results Analysis As shown in Table 1, all Kovar metal packaging shells prepared using the method of this invention (Examples 1-7) exhibited airtightness superior to the standard requirements, and their appearance was visually uniform and consistent, completely free of "snowflake-like bright spots" defects, with a yield rate exceeding 99%. For example, in Example 1, out of 100 products produced, 99 passed inspection, resulting in a yield rate of 99%. Although Comparative Examples 1 and 2 underwent sandblasting, the sandblasting pressure was significantly lower than the effective range required by this invention, insufficient to create a uniform and effective microstructural change on the substrate surface. Therefore, the defects could not be completely eliminated, and the yield rate remained very low (10%-20%). This underscores the importance of the process parameter range of this invention. Comparative Example 3 (conventional process) had the lowest yield rate (approximately 5%), with 95% of the products exhibiting "snowflake-like bright spots," highlighting the prevalence and severity of this defect in conventional processes, and the necessity and significant effect of introducing sandblasting pretreatment in this invention.

[0048] The typical morphology of the "snowflake-like bright spot" defect can be found in [reference needed]. Figure 2 The microstructure (100x magnification) of the product using traditional technology (Comparative Example 3) shown on the left shows obvious, irregularly distributed bright spots on its surface; while Figure 2 The right side shows the appearance of a qualified product after using the method of this invention; the surface is uniform and consistent. Figure 3 The microstructure of the product prepared by the method of Example 1 of this invention is further demonstrated at 100x, 500x, and 1000x magnification. The surface is uniform and dense, without abnormal protrusions or bright spots. For comparison, Figure 4 The microstructure of the unblasted product (Comparative Example 3) at different magnifications is shown, and the uneven microstructure that leads to the bright spots can be observed.

[0049] This invention effectively solves the color difference problem of Kovar products after plating by introducing a sandblasting process for the lead wires and chassis into the production process of Kovar metal packaging shells. It can increase the pass rate of products with post-plating ice flower (snowflake-like bright spots) from about 10% to over 99%, significantly improving the product's appearance quality and pass rate. Furthermore, the process is simple and easy to integrate into existing production lines, possessing high practical value and promising prospects for promotion. In addition, comparative tests show that the average tensile strength of the lead wire sealing points of the shells prepared using the method of this invention is comparable to that of conventional qualified products, indicating that this sandblasting pretreatment not only eliminates appearance defects but also ensures the mechanical reliability of the product.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for improving the color difference in the appearance of Kovar metal packaging shells after electroplating, characterized in that, Includes the following steps: S1. Incoming material inspection: Visually inspect the incoming lead wires and chassis made of Kovar alloy material; S2. Sandblasting: Fix the lead wire and the chassis separately, and perform sandblasting on each. The medium used for sandblasting is an abrasive medium with a particle size range of 120-320 mesh. The sandblasting pressure is 0.08-0.5MPa, the sandblasting angle is 60-80°, the sandblasting distance between the spray gun and the workpiece is 80-160mm, and the conveyor belt speed of the sandblasting machine is 500-2000 mm / min. S3. Post-sandblasting treatment: Soak, degrease, wash and dry the sandblasted lead wires and chassis. S4. Pre-treatment and sealing: The lead wire and chassis after step S3 are decarburized, oxidized and matched for sealing treatment to obtain a sealed semi-finished product. S5. Electroplating: Electroplating is performed on the sealed semi-finished product. S6. Finished product inspection.

2. The processing method according to claim 1, characterized in that, In step S2, the abrasive medium used for lead wire sandblasting is a mixed sand composed of 320-mesh glass microspheres and 180-mesh quartz sand in a mass ratio of 2:1; the abrasive medium used for chassis sandblasting is a mixed sand composed of 120-mesh quartz sand and 150-mesh quartz sand in a mass ratio of 1:

1.

3. The processing method according to claim 2, characterized in that, In step S2, the sandblasting pressure of the lead wire is 0.08-0.12 MPa, the sandblasting angle is 60-80°, and the belt speed is 800-1500 mm / min; the sandblasting pressure of the chassis is 0.3-0.5 MPa, the sandblasting angle is 60-80°, and the belt speed is 850-1600 mm / min.

4. The processing method according to claim 1, characterized in that, In step S2, the sandblasting process is carried out using an automatic sandblasting device.

5. The processing method according to claim 1, characterized in that, In step S2, the automatic sandblasting equipment is a conveyor-type automatic sandblasting machine.

6. The processing method according to claim 1, characterized in that, In step S3, the degreasing is performed by ultrasonic degreasing, and the cleaning time is 15-30 minutes.

7. The processing method according to claim 1, characterized in that, In step S4, the temperature of the matching and sealing is 900-1000℃, and the heat preservation time is 20-40min.

8. The processing method according to claim 1, characterized in that, In step S5, the electroplating process includes nickel plating and gold plating.

9. A Kovar metal encapsulation housing, characterized in that, It is prepared by the processing method according to any one of claims 1 to 8.

10. The Kovar metal encapsulation housing according to claim 9, characterized in that, The surface plating of the Kovar metal package shell consists of a nickel layer and a gold layer from the inside out. The thickness of the nickel layer is 4 to 15 μm, and the thickness of the gold layer is 1.3 to 5.7 μm.

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