Cold-pressed welding metal packaging shell and its manufacturing process

Abstract

The present invention discloses a cold-weldable metal packaging shell and its manufacturing process. The cold-weldable metal packaging shell includes a chassis, the chassis being a composite material of oxygen-free copper and Kovar; a transition ring disposed on the surface of the chassis' inner cavity; a glass insulator made of borosilicate glass; leads inserted into the glass insulator; and a cap made of oxygen-free copper and sealed to the chassis via a cold-weld process. By using the Kovar / oxygen-free copper composite material for the chassis of the cold-weldable metal packaging shell, wherein the chassis, transition ring, leads, and glass insulator are sealed, and the oxygen-free copper surface is cold-welded to the cap, also made of oxygen-free copper, the airtightness of the seal and the reliability of the product are ensured, thereby increasing the product's service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal packaging, and in particular relates to a cold-pressed welding type metal packaging shell and a manufacturing process thereof. Background Art

[0002] With the development of various electronics industries, metal packaging enclosures are widely used in military and civilian fields such as aerospace, aviation, radar, communications, and weapons. Currently, with the increasing application and demand for microelectronics products, products are moving towards miniaturization, multi-functionality, stability, and high performance. As a key component of integrated circuits, metal packaging enclosures primarily serve the functions of circuit support, signal transmission, heat dissipation, sealing, and chemical protection. They play a significant role in both their impact on circuit reliability and their contribution to circuit costs.

[0003] Among metal packaging shells, cold-pressed welded metal packaging shells have the characteristics of frequency stability and low noise. As a key component of 5G communication base stations and smart cars, they are of great significance in reducing signal delay and improving long-term stability.

[0004] Metal energy storage welding (hot pressure welding) generates stress and contamination in the internal wafer due to the high temperature during sealing. Stress release during welding causes frequency drift in the crystal oscillator, and there are also airtightness issues. Cold pressure welding can overcome the problems of contamination and thermal shock. However, traditional cold pressure welding metal package shells use a Kovar base with a sintered glass insulator. The Kovar base is then soldered to a copper base or copper-plated on the Kovar base. This can lead to problems such as loose solder joints between the Kovar and copper bases, uneven thickness of the electroplated copper layer due to Kovar base shape variations, and a loose and porous surface. Summary of the Invention

[0005] In view of this, it is necessary for the present invention to provide a cold-welded metal packaging shell, the chassis of which adopts Kovar / oxygen-free copper composite material, wherein the chassis, transition ring, lead and glass insulator are sealed, and the oxygen-free copper surface is cold-welded to the cap made of the same oxygen-free copper material, thereby ensuring the airtightness of the seal and the reliability of the product.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention first provides a cold-pressed welded metal packaging shell, which comprises:

[0008] A chassis, wherein the chassis is formed with an inner cavity, the chassis is a composite material of oxygen-free copper and Kovar, the outer surface of the chassis is oxygen-free copper, and the inner cavity is Kovar;

[0009] a transition ring, the transition ring being arranged on the surface of the inner cavity;

[0010] a glass insulator, the glass insulator being arranged on a surface of the transition ring away from the inner cavity, wherein the glass insulator is made of borosilicate glass;

[0011] A lead wire, the lead wire being inserted into the glass insulator;

[0012] and a cap, which is made of oxygen-free copper and is packaged with the chassis through a cold pressure welding process.

[0013] In a further embodiment, the transition ring has a cap edge, a gap between the cap edge of the transition ring and the chassis is 0.05-0.10 mm, and a gap between the outer diameter of the transition ring and the inner diameter of the chassis is 0.30-0.50 mm.

[0014] In a further embodiment, the thickness of the chassis is 0.30±0.1 mm, wherein the thickness of the oxygen-free copper accounts for 25%-45% of the composite material.

[0015] In a further embodiment, the transition ring and the inner cavity are made of the same calcifiable material, and the calcifiable material is selected from 4J29 or 4J42.

[0016] In a further embodiment, the thermal expansion coefficient of the borosilicate glass is 4.5-6.4×10 -6 / ℃.

[0017] In a further embodiment, an oxide layer is formed on the surfaces of the chassis, transition ring and lead, and the thickness of the oxide layer is 1-4 μm.

[0018] The present invention further provides a process for manufacturing a cold-welded metal packaging shell as described in any of the preceding items, comprising the following steps:

[0019] Processing to form the chassis and transition ring;

[0020] The chassis, transition ring and lead are subjected to surface cleaning, decarburization and pre-oxidation treatments in sequence;

[0021] After pre-assembling the chassis, transition ring, glass insulator and lead wire, they are sealed by fusion to form a semi-finished metal shell;

[0022] After the surface of the semi-finished metal shell is plated with a metal layer, it is cold-welded with a cap to obtain a cold-welded metal shell.

[0023] In a further embodiment, the cap is subjected to multi-step stretching during the forming process.

[0024] According to a further solution, the multi-step stretching process is as follows: the stretching coefficient of the first step is 0.45-0.55, and the material is fixed and pressed with a stripper plate; the radius of the punch corner is 2.0-2.5mm, and the radius of the die corner is 1.0-1.5mm; the stretching gap is above 1.2T; the stretching coefficient of the latter step is larger than that of the previous step, and the stretching coefficient of the last step is above 0.9.

[0025] In a further embodiment, the cold pressure welding is performed at room temperature without the action of an external heat source or electric current, and a pressure of 30-45 Pa is applied to the workpiece to achieve solid-state welding.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The chassis of this invention utilizes a Kovar / oxygen-free copper composite material, with a layer of oxygen-free copper laminated onto a Kovar alloy substrate. The Kovar surface serves as the inner surface of the chassis, while the oxygen-free copper surface serves as the outer surface. High-temperature sealing of the Kovar surface with the transition ring, lead wire, and glass insulator ensures airtightness. While maintaining the electrical and thermal conductivity advantages of copper, the oxygen-free copper layer on the chassis' outer surface is sealed to the cap, also made of oxygen-free copper, via cold welding, ensuring an airtight seal. The metal packaging housing of this invention exhibits excellent airtightness and reliability, extending the product's service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an exploded view of the main body 100 of the metal packaging shell in a preferred embodiment of the present invention;

[0029] Figure 2 for Figure 1 Schematic diagram of the assembly structure of the middle body 100;

[0030] Figure 3 It is a structural diagram of a metal packaging shell;

[0031] Figure 4 FIG. 1 is a flow chart of a process for manufacturing a metal packaging shell in a preferred embodiment of the present invention.

[0032] In the figure: 100-body, 10-chassis, 20-glass insulator, 30-transition ring, 40-lead, 50-bracket;

[0033] 200-blocked shots. DETAILED DESCRIPTION

[0034] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0036] In a preferred embodiment of the present invention, a metal packaging shell is disclosed. The metal packaging shell includes a body 100 and a cap 200. The structure of the body 100 is as follows: Figure 1 and Figure 2 As shown in FIG, it includes a chassis 10, a transition ring 20, a glass insulator 30 and a lead 40, and further includes a bracket 50. The chassis 10, the transition ring 20, the glass insulator 30 and the lead 40 are sealed by fusion to form a body 100, and the bracket 50 is welded to the side of the chassis 10 away from the lead 40. The body 100 and the cap 200 are sealed by cold pressure welding to form a metal packaging shell, as shown in FIG. Figure 3 As shown in .

[0037] See also Figure 1 In this embodiment, the chassis 10 is an annular structure and is formed with a flange, which is used to cooperate with the cap edge of the cap 200 to achieve a seal between the body 100 and the cap 200. The chassis 10 is formed with an inner cavity and is made of a Kovar / oxygen-free copper composite material. The Kovar / oxygen-free copper composite material can be obtained by plating oxygen-free copper on the surface of the Kovar material, which will not be described in detail here. In this embodiment, the thickness of the chassis is 0.30±0.1mm, and the thermal expansion coefficient is 8.0-9.0×10 -6 / °C, wherein the thickness of oxygen-free copper accounts for 25%-45% of the composite material. Furthermore, the outer surface of the chassis 10 is oxygen-free copper, and the inner cavity is Kovar material, so that the outer surface is sealed with the cap 200 and the inner cavity is welded with the glass insulator 30.

[0038] Furthermore, the transition ring 20 is assembled within the inner cavity of the chassis 10 and has a cap edge that matches the inner cavity of the chassis 10. In this embodiment, the gap between the cap edge of the transition ring 20 and the chassis 10 is controlled to be 0.05-0.10 mm, while the gap between the inner cavity of the chassis 10 and the outer diameter of the transition ring 20 is controlled to be 0.30-0.50 mm. By properly controlling the gap range, stress deformation caused by extrusion due to force on the Y-axis direction of the shell edge during the cold pressure welding of the cap 200 and the chassis 10 is avoided, thereby effectively reducing the impact of extrusion on the glass sealing area. Furthermore, the transition ring 20 is made of the same kovar material as the chassis 10. Specific examples of the kovar material include, but are not limited to, 4J29 or 4J42.

[0039] Furthermore, the glass insulator 30 is mounted on the surface of the transition ring 20 away from the inner cavity of the chassis 10, and is used to perform high-temperature sealing on the chassis 10, the transition ring 20, and the lead 40. In this embodiment, the glass insulator 30 is made of borosilicate glass, which has a thermal expansion coefficient of 4.5-6.4×10 -6 Because the thermal expansion coefficients of borosilicate glass and the Kovar material of the inner cavity of the chassis 10 and the transition ring 20 are similar, a good sealing connection can be achieved after high-temperature sealing, thereby ensuring the airtightness of the glass sealing area.

[0040] Furthermore, the lead wire 40 is assembled into the glass insulator 30 via a mold and subsequently sealed at high temperature. In this embodiment, the lead wire 40 is pre-fabricated with solder, which effectively controls the solder flow area and prevents the solder flow from affecting the subsequent pre-oxidation layer on the chassis 10. In this embodiment, the solder is silver-copper non-eutectic, and the brazing temperature T satisfies t+20°C ≤ T ≤ t+50°C, where t is the solder flow point. The holding time is 4-10 minutes, and the atmosphere is pure hydrogen.

[0041] Furthermore, in this embodiment, an oxide layer is formed on the surfaces of the chassis 10, the transition ring 20 and the lead 40, which can be formed by a conventional pre-oxidation process in the art. In this embodiment, the thickness of the oxide layer is 1-4 μm.

[0042] It is understandable that the main body 100 may further include a bracket 50 as needed. In this embodiment, the bracket 50 may be made of stainless steel or Kovar.

[0043] See also Figure 3 The cap 200 is assembled with the body 100 to form a metal enclosure. The cap edge of the cap 200 is butted against the flange of the chassis 10 to form a sealed edge. In this embodiment, the cap 200 is made of oxygen-free copper and is sealed to the chassis 10 via a cold pressure welding process. This ensures an airtight seal and avoids the thermal shock to the wafer or chip caused by traditional sealing methods such as energy storage welding, thus ensuring product reliability and effectively preventing the generation of contaminants.

[0044] The present invention further discloses a process for manufacturing a metal packaging shell, the main process flow of which is as follows: Figure 4 As shown in , it mainly includes the following steps:

[0045] Processing to form the chassis 10 and the transition ring 20

[0046] The chassis 10 and the transition ring 20 are obtained by processing using a processing and forming process commonly used in this field, wherein the gap between the chassis 10 and the cap edge of the transition ring 20 is controlled to be in the range of 0.05-0.10mm, and the gap between the inner cavity of the chassis 10 and the outer diameter of the transition ring 20 is in the range of 0.30-0.50mm.

[0047] Parts pretreatment

[0048] Specifically, the chassis 10, transition ring 20, and lead 40 are sequentially subjected to surface cleaning, decarburization, and pre-oxidation. The cleaning and decarburization processes are conventional in the art and are not further elaborated here. According to an embodiment of the present invention, the pre-oxidation process specifically involves pre-oxidation of the chassis 10, transition ring 20, and lead 40 in a mixed atmosphere of gas A and reducing gas B, where gas A is a rare gas or nitrogen and reducing gas B is hydrogen or water vapor.

[0049] Lead 40 preform solder

[0050] Pre-prepare solder on the lead 40 of the Kovar nail head, wherein the solder is silver-copper non-eutectic, the brazing temperature T satisfies t+20°C≤T≤t+50°C, where t is the solder flow point; the holding time is 4-10 minutes, and the atmosphere is pure hydrogen;

[0051] The inner cavity of the processed chassis 10 is brazed with the prefabricated lead 40 of solder, and the brazing temperature T satisfies t+20°C≤T≤t+50°C, where t is the solder flow point; the holding time is 4-10 minutes, and the atmosphere is pure hydrogen.

[0052] High temperature sealing

[0053] The transition ring 20, the glass insulator 30 and the chassis 10 are assembled, the lead wire 40 is inserted into the hole of the glass insulator 30 and pre-assembled into a whole through positioning by a mold, and then sealed at high temperature to form a semi-finished metal shell. The sealing temperature is 900-940°C, the holding time is 15±5 minutes, and the atmosphere is pure nitrogen.

[0054] Plated metal layer

[0055] A nickel layer and a gold layer are plated on the surface of the semi-finished metal shell in sequence, wherein the thickness of the nickel layer and the gold layer can be adjusted according to the actual situation in the field. Preferably, the nickel plating thickness is 1.27μm-8.90μm, and the gold plating thickness is 1.30μm-5.70μm.

[0056] Welding bracket 50

[0057] The semi-finished metal shell is resistance welded to the bracket 50 through a mold. Specifically, the bracket 50 and the lead 40 are fixed by a fixture, and the resistance welding current is 60-120A.

[0058] Cold pressure welding

[0059] The formed body 100 and the cap 200 are cold-welded to form a cold-welded metal packaging shell. The cap 200 is subjected to multi-step stretching during the forming process. Specifically, in some specific embodiments of the present invention, the first stretching coefficient is 0.45-0.55, and the material is fixed and pressed with a stripper plate; the radius of the punch corner is 2.0-2.5mm, and the radius of the die corner is 1.0-1.5mm; the stretching gap is greater than 1.2T; the stretching coefficient of the latter step is greater than that of the previous step, and the stretching coefficient of the last stretching process is greater than 0.9; more preferably, the stretching coefficient of the first step is 0.40-0.50, the stretching coefficient of the second step is 0.51-0.60, the stretching coefficient of the third step is 0.61-0.70, and the stretching coefficient of the fourth step is 0.71-0.80, and the stretching coefficient of the last stretching process is greater than 0.90. By employing a multi-step stretching process to form the cap 200, wrinkling, cracking, and material thinning during processing are avoided, which could compromise the airtightness and product reliability of the metal package. Furthermore, the cold pressure welding is performed at room temperature without an external heat source or current, and a pressure of 30-45 Pa is applied to the workpiece to achieve solid-state welding. Pressure is applied to the workpiece through a mold, causing plastic deformation of the metal and forming intergranular bonds between the copper, thus achieving solid-state welding.

[0060] The metal packaging shells made by this process were tested for airtightness according to the method of GJB 923A "General Specification for Semiconductor Discrete Device Shells". The airtightness test results were all ≤1×10 -4 Pa·cm 3 / s(A4 He).

[0061] In conjunction with specific embodiments, Figure 1-3 The cold-pressed metal packaging shell shown in FIG is taken as an example to describe the manufacturing process in detail. It is understood that the methods not specifically described below are all conventional processes or methods in the art and will not be described in detail.

[0062] Table 1 Main parameters of the cold-pressed metal packaging shell in Examples 1-3

[0063]

[0064] Example 1

[0065] S1, processing to form the chassis 10 (thermal expansion coefficient is 8.0-9.0×10 -6 / ° C) and the transition ring 30, so that the chassis 10 forms an inner cavity that matches the cap edge of the transition ring 30;

[0066] S2. After the surfaces of the chassis 10, transition ring 30, and lead 40 processed and formed in S1 are cleaned and decarburized, the chassis 10, transition ring 30, and lead 40 are pre-oxidized in a mixed atmosphere of nitrogen and hydrogen to form a pre-oxidation layer with a thickness of 2 μm.

[0067] S3. Prefabricate solder on the lead 40 of the Kovar nail head, wherein the solder is silver-copper non-eutectic, the brazing temperature is 920° C., the holding time is 6 minutes, and the atmosphere is pure hydrogen;

[0068] S4, brazing the inner cavity of the chassis 10 pre-oxidized in step S2 with the lead 40 prefabricated with solder, at a brazing temperature of 920° C., a holding time of 6 minutes, and a pure hydrogen atmosphere;

[0069] S6, borosilicate glass material (thermal expansion coefficient 4.5-6.4×10 -6 / °C) glass insulator 30 is assembled with chassis 10 and transition ring 30, and the lead wire is inserted into the hole of borosilicate glass and pre-assembled into a whole through positioning by a mold, and then sealed at high temperature in a pure nitrogen atmosphere;

[0070] S7, the surface of the metal shell sealed in step S6 is plated with nickel to a thickness of 6 μm and a nickel-gold layer to a thickness of 2 μm;

[0071] S8, resistance welding the metal shell after nickel and gold plating in step S7 to the bracket 50 through a mold, with a resistance welding current of 80A;

[0072] S9. Cold-press the plated metal shell in S8 to the cap 200. The cap 200 is formed by multiple stretching steps. The first stretching coefficient is 0.40, and the material is fixed and pressed with a stripper plate. The radius of the punch corner is 2.0mm, and the radius of the die corner is 1.0mm. The stretching gap is greater than 1.2T. The second stretching coefficient is 0.51, the third stretching coefficient is 0.61, and the fourth stretching coefficient is 0.71. The stretching coefficient of the last stretching process is 0.90. Cold-press welding is performed at room temperature without external heat source or current. A pressure of 30MPa is applied to the workpiece to achieve solid-state welding.

[0073] Example 2

[0074] This embodiment adopts the same implementation method as that of Example 1, except that the parameters in Table 1 are followed and other processes are the same as those of Example 1.

[0075] Example 3

[0076] This embodiment adopts the same implementation method as that of Example 1, except that the parameters in Table 1 are followed and other processes are the same as those of Example 1.

[0077] Comparative Example 1

[0078] This comparative example adopts the same implementation as Example 3, except that the chassis 10 is not made of composite material, but of kovar material.

[0079] Comparative Example 2

[0080] This comparative example adopts the same implementation as that of Example 3, except that the chassis 10 is not made of composite material, but is made of oxygen-free copper.

[0081] Comparative Example 3

[0082] This comparative example adopts the same implementation method as Example 3, except that: the cap 200 is formed by a one-step stretching process, the specific process is a stretching coefficient of 0.9, and the material is fixed and pressed with a stripper plate; the radius of the punch corner is 2.0mm; the radius of the die corner is 1.0mm; the stretching gap is above 1.2T.

[0083] The metal packaging shells prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to airtightness test according to the method of GJB 923A "General Specification for Semiconductor Discrete Device Shells". The results are shown in Table 2.

[0084] Table 2 Metal package airtightness test results

[0085] Airtightness Example 1 <![CDATA[2.4×10 -5 Pa·cm 3 / s]]> Example 2 <![CDATA[1.8×10 -5 Pa·cm 3 / s]]> Example 3 <![CDATA[1.5×10 -5 Pa·cm 3 / s]]> Comparative Example 1 <![CDATA[2.5×10 -2 Pa·cm 3 / s]]> Comparative Example 2 <![CDATA[1.6×10 -1 Pa·cm 3 / s]]> Comparative Example 3 <![CDATA[1.2×10 -0 Pa·cm 3 / s]]>

[0086] It can be seen from the test results in Table 2 that, compared with Comparative Examples 1-3, the metal packaging shells obtained in Examples 1-3 have stronger airtightness and reliability, and the service life of the products is also longer.

[0087] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0088] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A cold-pressed metal packaging shell, characterized in that: include: A chassis, wherein the chassis is formed with an inner cavity, the chassis is a composite material of oxygen-free copper and Kovar, the outer surface of the chassis is oxygen-free copper, and the inner cavity is Kovar; a transition ring, the transition ring being arranged on the surface of the inner cavity; a glass insulator, the glass insulator being arranged on a surface of the transition ring away from the inner cavity, wherein the glass insulator is made of borosilicate glass; A lead wire, the lead wire being inserted into the glass insulator; And a cap, the cap is made of oxygen-free copper, the cap edge of the cap is butted and sealed with the flange of the chassis, and is packaged with the chassis through a cold pressure welding process.

2. The cold-welded metal packaging shell according to claim 1, wherein: The transition ring has a cap edge, the gap between the cap edge of the transition ring and the chassis is 0.05-0.10 mm, and the gap between the outer diameter of the transition ring and the inner diameter of the chassis is 0.30-0.50 mm.

3. The cold-welded metal packaging shell according to claim 1, wherein: The thickness of the chassis is 0.30±0.1 mm, wherein the thickness of the oxygen-free copper accounts for 25%-45% of the composite material.

4. The cold-welded metal packaging shell according to claim 1, wherein: The transition ring and the inner cavity are made of the same calcifiable material, and the calcifiable material is selected from 4J29 or 4J42.

5. The cold-welded metal packaging shell according to claim 1, wherein: The thermal expansion coefficient of borosilicate glass is 4.5-6.4×10 -6 / ℃.

6. The cold-welded metal packaging shell according to claim 1, wherein: An oxide layer is formed on the surfaces of the chassis, the transition ring and the lead, and the thickness of the oxide layer is 1-4 μm.

7. A process for manufacturing a cold-welded metal packaging shell according to any one of claims 1 to 6, characterized in that: The following steps are involved: Processing to form the chassis and transition ring; The chassis, transition ring and lead are subjected to surface cleaning, decarburization and pre-oxidation treatments in sequence; After pre-assembling the chassis, transition ring, glass insulator and lead wire, they are sealed by fusion to form a semi-finished metal shell; After the surface of the semi-finished metal shell is plated with a metal layer, it is cold-welded with a cap to obtain a cold-welded metal shell.

8. The manufacturing process according to claim 7, characterized in that: The cap is stretched in multiple steps during the forming process.

9. The manufacturing process according to claim 8, characterized in that: The multi-step stretching process is specifically as follows: the stretching coefficient of the first step is 0.45-0.55, and the material is fixed and pressed with a stripper plate; the radius of the punch corner is 2.0-2.5mm, and the radius of the die corner is 1.0-1.5mm; the stretching gap is above 1.2T; the stretching coefficient of the latter step is larger than that of the previous step, and the stretching coefficient of the last step is above 0.

9.

10. The manufacturing process according to claim 7, characterized in that: The cold pressure welding is performed at room temperature without the action of an external heat source or electric current, and a pressure of 30-45 Pa is applied to the workpiece to achieve solid-state welding.

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