A method for reducing deformation of large-size parallel seam welded cover plates

Abstract

The present invention relates to a method for reducing deformation of large-sized parallel seam welded cover plates, comprising the following steps: providing a packaging shell, determining the length and width of a step cover plate sample, determining the height of a cover plate boss on a step cover plate, making a welding frame, processing a welding frame step on the welding frame, welding the welding frame to the packaging shell, plating a bottom coating and a surface coating, making a step cover plate, forming a step cover plate surface coating, chip mounting, and welding the step cover plate to the welding frame after wire bonding. The welding frame of the present invention allows the cover plate boss portion of the large-sized parallel seam welded step cover plate to be supported at the welding frame step, giving full play to the advantages of the cover plate boss. Since the thickness of the step cover plate at the cover plate boss position is increased, the maximum depression amount of the step cover plate in the sealing test, the constant acceleration test, and the mechanical impact test will be significantly reduced; the present invention can reduce the deformation of the parallel seam welded cover plate without changing the overall packaging structure, and is a packaging solution with a lower cost.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuit manufacturing, and specifically discloses a method for reducing deformation of a large-size parallel seam welded cover plate. Background Art

[0002] Parallel seam welding is the main process for achieving hermetic packaging of high-performance flip-chip chips and hybrid integrated circuits. The packaging shell of such devices usually adopts ceramic shell.

[0003] With the advancement of chip manufacturing technology and the enhancement of device functions, the size of the package shell is getting larger and larger, and the corresponding size of the parallel seam welded cover plate is also increasing. Due to the increase in the size of the cover plate, the device will have obvious cover plate deformation problems in the sealing test, constant acceleration test, and mechanical impact test, which is mainly manifested as the inward concave phenomenon of the cover plate. In severe cases, the cover plate will undergo plastic deformation and the insulation distance between the cover plate and the internal components will be reduced, or even cause a short circuit problem. The usual circumvention method in the industry is to use a step cover plate instead of a conventional flat cover plate. The thickness of the welding area of ​​this step cover plate is the same as that of the conventional flat cover plate, while the middle part is thickened, and the thickness is about 3 times the thickness of the welding area. When the step cover plate is welded, the thicker area of ​​the cover plate is all located on the inside of the welding frame. Compared with the flat cover plate, the overall deformation of the cover plate will be improved. Nevertheless, since the overall support part of the cover plate (i.e., the welding area of ​​the cover plate) is still the thinnest part, the advantage of thickening the cover plate cannot be fully reflected. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for reducing the deformation of large-sized parallel seam welded cover plates.

[0005] According to the technical solution provided by the present invention, the method for reducing the deformation of large-sized parallel seam welded cover plates comprises the following steps:

[0006] S1. Determine a packaging shell according to the size of the chip to be packaged and the packaging shape requirements, wherein the packaging shell includes a packaging shell body and a metallization layer fixed on the upper surface of the outer side of the packaging area of ​​the packaging shell body;

[0007] S2. Determine the length and width of the step cover plate sample according to the length and width of the package shell body. The step cover plate sample includes the cover plate body sample and the cover plate boss sample fixed to the middle of the lower surface of the cover plate body sample. Calculate the maximum depression h2 of the step cover plate sample in the sealing test, constant acceleration test and mechanical impact test under different thickness conditions;

[0008] S3. Compare the difference between the initial gap h between the lower surface of the step cover plate sample and the upper surface of the chip before the test and the maximum depression h2 of the step cover plate sample during the test, and compare the difference with the minimum allowable gap h1 between the upper surface of the chip and the lower surface of the step cover plate sample. If h-h2≥h1, the height of the cover plate boss sample is the minimum height of the cover plate boss on the step cover plate to be manufactured. The step cover plate includes a cover plate body and a cover plate boss fixed to the middle of the lower surface of the cover plate body. The height of the cover plate boss on the step cover plate is ≥ the minimum height of the cover plate boss sample.

[0009] S4, using a parallel seam welding frame process to produce a welding frame that matches the packaging shell;

[0010] S5. A welding frame step is machined on one side of the parallel seam welding surface of the welding frame close to the inner cavity by a mechanical processing technology, and the depth of the welding frame step is equal to the height of the cover plate boss on the step cover plate to be manufactured;

[0011] S6, using a brazing process to braze the welding frame onto the metallization layer of the package shell through silver-copper solder to form a bonding layer;

[0012] S7, using an electroplating process to first plate a bottom coating on the side and top surface of the welding frame after brazing and the side and bottom surface of the welding frame step, and then plate a surface coating (62) on the bottom coating to form a composite coating;

[0013] S8. According to the requirements of S3, a step cover plate is manufactured by etching process, wherein the width of the seam welding area of ​​the step cover plate is adapted according to the width of the sealing area of ​​the welding frame, and the height of the cover plate boss of the manufactured step cover plate is ≥ the minimum height of the cover plate boss sample described in S3;

[0014] S9, forming a step cover plate surface coating on the step cover plate surface;

[0015] S10, after chip mounting and wire bonding, the step cover plate is welded to the welding frame step of the welding frame by a parallel seam welding process, and the lower surface edge of the cover plate boss is supported on the bottom surface of the welding frame step;

[0016] S11. After the parallel seam welding is completed, a packaging structure is completed that can reduce the deformation of the large-size parallel seam welding cover.

[0017] Preferably, in S5, the bottom width W1 of the welding frame step is 1 / 4 to 1 / 3 of the original width W of the welding frame.

[0018] Preferably, in S7, the bottom plating layer is a nickel plating layer, and the plating thickness of the bottom plating layer is 1.3-8.9 μm.

[0019] Preferably, in S7, the surface coating is a gold coating, and the thickness of the surface coating is 1.3-5.7 μm.

[0020] Preferably, in S9, a chemical nickel plating process is used to form a step cover plate surface coating on the step cover plate surface, and the step cover plate surface coating is a chemical nickel plating layer.

[0021] Preferably, in S9, an electroplating process is used to form a step cover plate surface coating on the step cover plate surface, and the step cover plate surface coating is an electroplated nickel-gold composite coating.

[0022] Preferably, in S10, the lower surface edge of the cover plate boss is supported on the bottom surface of the welding frame step, and the supporting width is not less than 1 / 3 of the bottom surface width W1 of the welding frame step.

[0023] The advantages of the present invention are:

[0024] 1. Compared with the conventional large-size parallel sealing welding frame of ceramic housing, the welding frame of the present invention enables the cover plate boss part of the large-size parallel seam welding step cover plate to be supported at the step of the welding frame, giving full play to the advantages of the cover plate boss. Since the thickness of the step cover plate at the cover plate boss position is increased, the maximum concavity of the step cover plate in the sealing test, constant acceleration test, and mechanical impact test will be significantly reduced;

[0025] 2. The present invention can reduce the deformation of the parallel seam welded cover plate without changing the overall structure of the package (such as adding a support structure in the inner cavity of the package), and is a lower-cost packaging solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural diagram of the package shell.

[0027] Figure 2 It is the structural diagram of the welding frame.

[0028] Figure 3 This is a structural diagram of the welding frame after the welding frame steps are processed.

[0029] Figure 4 yes Figure 3 Welding frame and Figure 1 Structural diagram of the package shell welded together.

[0030] Figure 5 is Figure 4 Structural diagram of the base coating and surface coating on the welding frame.

[0031] Figure 6 It is a structural diagram of the step cover.

[0032] Figure 7 This is a structural diagram of a step cover plate formed with a chemical nickel plating layer.

[0033] Figure 8 3 is a structural diagram of the packaging structure obtained in Example 1.

[0034] Fig. 9 yes Figure 8 Enlarged view of part A.

[0035] Fig.10 It is a structural diagram of a step cover plate formed with an electroplated nickel-gold composite coating.

[0036] Fig.11 It is a structural diagram of the packaging structure obtained in Example 2.

[0037] Fig.12 yes Fig.11 Enlarged view of part B. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for reducing deformation of a large-size parallel seam welded cover plate, the method comprising the following steps:

[0041] S1, determining a packaging shell 1 according to the size of the chip 2 to be packaged and the packaging shape requirements, wherein the packaging shell 1 includes a packaging shell body 11 and a metallization layer 12 fixed on the upper surface of the outer side of the packaging area of ​​the packaging shell body 11; Figure 1 As shown;

[0042] S2. Determine the length and width of the step cover plate sample according to the length and width of the package shell body 11. The step cover plate sample includes the cover plate body sample and the cover plate boss sample fixed to the middle of the lower surface of the cover plate body sample. Calculate the maximum depression h2 of the step cover plate sample in the sealing test, constant acceleration test and mechanical impact test under different thickness conditions;

[0043] S3. Compare the difference between the initial gap h between the lower surface of the step cover plate sample and the upper surface of the chip 2 before the test and the maximum depression h2 of the step cover plate sample during the test, and compare the difference with the minimum allowable gap h1 between the upper surface of the chip and the lower surface of the step cover plate sample. If h-h2≥h1, the height of the cover plate boss sample is the minimum height of the cover plate boss 32 on the step cover plate 3 to be manufactured. The step cover plate 3 includes a cover plate body 31 and a cover plate boss 32 fixed to the middle of the lower surface of the cover plate body 31. The height of the cover plate boss 32 on the step cover plate 3 is ≥ the minimum height of the cover plate boss sample.

[0044] S4, using parallel seam welding welding frame process to manufacture a welding frame 4 that matches the packaging shell 1, such as Figure 2 As shown;

[0045] S5, using mechanical processing technology to process a welding frame step 41 on one side of the parallel seam welding surface of the welding frame 4 close to the inner cavity direction, such as Figure 3 As shown, the bottom width W1 of the welding frame step 41 is 1 / 4 of the original width W of the welding frame 4, and the depth of the welding frame step 41 is equal to the height of the cover plate boss 32 on the step cover plate 3 to be manufactured;

[0046] S6, using a brazing process to braze the welding frame 4 on the metallization layer 12 of the package shell 1 through silver-copper solder to form a bonding layer 5, such as Figure 4 As shown;

[0047] S7, using electroplating process to plate the bottom coating 61 on the side and top surface of the welding frame 4 after brazing and the side and bottom surface of the welding frame step 41, and then plate the surface coating 62 on the bottom coating 61 to form a composite coating, such as Figure 5 As shown; the bottom plating layer 61 is a nickel plating layer, the thickness of the bottom plating layer 61 is 1.3 μm, the surface plating layer 62 is a gold plating layer, the thickness of the surface plating layer 62 is 5.7 μm;

[0048] S8, according to the requirements of S3 and using etching process to manufacture the step cover plate 3, such as Figure 6 As shown, the width of the seam welding area of ​​the step cover plate 3 is adapted according to the width of the sealing area of ​​the welding frame 4, and the support width of the cover plate body 31 on the bottom surface of the welding frame step 41 when the step cover plate 3 is installed is at least 1 / 3 of the width W1 of the bottom surface of the welding frame step 41, and the height of the cover plate boss 32 of the manufactured step cover plate 3 is ≥ the minimum height of the cover plate boss sample described in S3;

[0049] S9, using a chemical nickel plating process to form a step cover plate surface coating 7 on the surface of the step cover plate 3, such as Figure 7 As shown, the surface coating 7 of the step cover plate is a chemical nickel plating layer;

[0050] S10, after the chip 2 is mounted and wire-bonded, the step cover plate 3 is welded to the welding frame step 41 of the welding frame 4 by a parallel seam welding process, and the lower surface edge of the cover plate boss 32 is supported on the bottom surface of the welding frame step 41, and the supporting width is not less than 1 / 3 of the bottom surface width W1 of the welding frame step 41;

[0051] S11. After the parallel seam welding is completed, a packaging structure is completed that can reduce the deformation of the large-size parallel seam welding cover plate, such as Figure 8 and Fig. 9 shown.

[0052] Example 2

[0053] A method for reducing deformation of a large-size parallel seam welded cover plate, the method comprising the following steps:

[0054] S1, providing a package shell 1 with a chip 2 pre-flipped, the package shell 1 comprising a package shell body 11 and a metallization layer 12 fixed on the upper surface of the outer side of the package area of ​​the package shell body 11, such as Figure 1 As shown;

[0055] S2. Determine the length and width of the step cover plate sample according to the length and width of the package shell body 11. The step cover plate sample includes the cover plate body sample and the cover plate boss sample fixed to the middle of the lower surface of the cover plate body sample. Calculate the maximum depression h2 of the step cover plate sample in the sealing test, constant acceleration test and mechanical impact test under different thickness conditions;

[0056] S3. Compare the difference between the initial gap h between the lower surface of the step cover plate sample and the upper surface of the chip 2 before the test and the maximum depression h2 of the step cover plate sample during the test, and compare the difference with the minimum allowable gap h1 between the upper surface of the chip and the lower surface of the step cover plate sample. If h-h2≥h1, the height of the cover plate boss sample is the minimum height of the cover plate boss 32 on the step cover plate 3 to be manufactured. The step cover plate 3 includes a cover plate body 31 and a cover plate boss 32 fixed to the middle of the lower surface of the cover plate body 31. The height of the cover plate boss 32 on the step cover plate 3 is ≥ the minimum height of the cover plate boss sample.

[0057] S4, using parallel seam welding welding frame process to manufacture a welding frame 4 that matches the packaging shell 1, such as Figure 2 As shown;

[0058] S5, using mechanical processing technology to process a welding frame step 41 on one side of the parallel seam welding surface of the welding frame 4 close to the inner cavity direction, such as Figure 3 As shown, the bottom width W1 of the welding frame step 41 is 1 / 3 of the original width W of the welding frame 4, and the depth of the welding frame step 41 is equal to the height of the cover plate boss 32 on the step cover plate 3 to be manufactured;

[0059] S6, using a brazing process to braze the welding frame 4 on the metallization layer 12 of the package shell 1 through silver-copper solder to form a bonding layer 5, such as Figure 4 As shown;

[0060] S7, using electroplating process to plate the bottom coating 61 on the side and top surface of the welding frame 4 after brazing and the side and bottom surface of the welding frame step 41, and then plate the surface coating 62 on the bottom coating 61 to form a composite coating, such as Figure 5 As shown; the bottom plating layer 61 is a nickel plating layer, the thickness of the bottom plating layer 61 is 8.9 μm, the surface plating layer 62 is a gold plating layer, the thickness of the surface plating layer 62 is 1.3 μm;

[0061] S8, according to the requirements of S3 and using etching process to manufacture the step cover plate 3, such as Figure 6 As shown, the width of the seam welding area of ​​the step cover plate 3 is adapted according to the width of the sealing area of ​​the welding frame 4, and the support width of the cover plate body 31 on the bottom surface of the welding frame step 41 when the step cover plate 3 is installed is at least 1 / 3 of the width W1 of the bottom surface of the welding frame step 41, and the height of the cover plate boss 32 of the manufactured step cover plate 3 is ≥ the minimum height of the cover plate boss sample described in S3;

[0062] S9, using electroplating process to form a step cover plate surface coating 7 on the surface of the step cover plate 3, such as Fig.10 As shown, the surface coating 7 of the step cover plate is an electroplated nickel-gold composite coating;

[0063] S10, after the chip 2 is mounted and wire-bonded, the step cover plate 3 is welded to the welding frame step 41 of the welding frame 4 by a parallel seam welding process, and the lower surface edge of the cover plate boss 32 is supported on the bottom surface of the welding frame step 41, and the supporting width is not less than 1 / 3 of the bottom surface width W1 of the welding frame step 41;

[0064] S11. After the parallel seam welding is completed, a packaging structure is completed that can reduce the deformation of the large-size parallel seam welding cover plate, such as Fig.11 and Fig.12 shown.

[0065] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for reducing deformation of large-size parallel seam welded cover plates, characterized in that The method comprises the following steps: S1. Determining a packaging shell (1) according to the size of the chip (2) to be packaged and the packaging shape requirements, wherein the packaging shell (1) comprises a packaging shell body (11) and a metallization layer (12) fixed on the upper surface of the outer side of the packaging area of ​​the packaging shell body (11); S2. Determine the length and width of the step cover plate sample according to the length and width of the package shell body (11), the step cover plate sample comprising a cover plate body sample and a cover plate boss sample fixed to the middle of the lower surface of the cover plate body sample, and calculate the maximum indentation h2 of the step cover plate sample in a sealing test, a constant acceleration test, and a mechanical impact test under different thickness conditions; S3. Compare the difference between the initial gap h between the lower surface of the step cover plate sample and the upper surface of the chip (2) before the test and the maximum depression h2 of the step cover plate sample during the test, and compare the difference with the minimum allowable gap h1 between the upper surface of the chip and the lower surface of the step cover plate sample. If h-h2≥h1, the height of the cover plate boss sample is the minimum height of the cover plate boss (32) on the step cover plate (3) to be manufactured. The step cover plate (3) includes a cover plate body (31) and a cover plate boss (32) fixed to the middle of the lower surface of the cover plate body (31). The height of the cover plate boss (32) on the step cover plate (3) is ≥ the minimum height of the cover plate boss sample. S4, using a parallel seam welding frame process to produce a welding frame (4) that matches the packaging shell (1); S5. A welding frame step (41) is machined on one side of the parallel seam welding surface of the welding frame (4) close to the inner cavity by a mechanical processing process, wherein the bottom surface width W1 of the welding frame step (41) is 1 / 4 to 1 / 3 of the original width W of the welding frame (4), and the depth of the welding frame step (41) is equal to the height of the cover plate boss (32) on the step cover plate (3) to be manufactured; S6, using a brazing process to braze the welding frame (4) onto the metallization layer (12) of the package shell (1) using silver-copper solder to form a bonding layer (5); S7, using an electroplating process to first plate a bottom coating (61) on the side and top surface of the soldering frame (4) and the side and bottom surface of the soldering frame step (41) after soldering, wherein the bottom coating (61) is a nickel coating, and the coating thickness of the bottom coating (61) is 1.3-8.9 μm, and then plate a surface coating (62) on the bottom coating (61), wherein the surface coating (62) is a gold coating, and the thickness of the surface coating (62) is 1.3-5.7 μm, to form a composite coating; S8. According to the requirements of S3 and using an etching process, a step cover plate (3) is manufactured, wherein the width of the seam welding area of ​​the step cover plate (3) is adapted according to the width of the sealing area of ​​the welding frame (4), and the height of the cover plate boss (32) of the manufactured step cover plate (3) is ≥ the minimum height of the cover plate boss sample described in S3; S9, forming a step cover plate surface coating (7) on the surface of the step cover plate (3); S10, after the chip (2) is mounted and wire bonded, the step cover plate (3) is welded to the welding frame step (41) of the welding frame (4) using a parallel seam welding process, and the lower surface edge of the cover plate boss (32) is supported on the bottom surface of the welding frame step (41); S11. After the parallel seam welding is completed, a packaging structure is completed that can reduce the deformation of the large-size parallel seam welding cover.

2. The method for reducing deformation of large-size parallel seam welded cover plates as claimed in claim 1, characterized in that: In S9, a chemical nickel plating process is used to form a step cover plate surface coating (7) on the surface of the step cover plate (3), and the step cover plate surface coating (7) is a chemical nickel plating layer.

3. The method for reducing deformation of large-size parallel seam welded cover plates as claimed in claim 1, characterized in that: In S9, an electroplating process is used to form a step cover plate surface coating (7) on the surface of the step cover plate (3), and the step cover plate surface coating (7) is an electroplated nickel-gold composite coating.

4. The method for reducing deformation of large-size parallel seam welded cover plates as claimed in claim 1, characterized in that: In S10, the lower surface edge of the cover plate boss (32) is supported on the bottom surface of the welding frame step (41), and the supporting width is not less than 1 / 3 of the bottom surface width W1 of the welding frame step (41).

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