Method for presetting gold-tin solder on ceramic tube shell

Abstract

The invention discloses a method for presetting gold-tin solder on a ceramic tube shell, and belongs to the technical field of semiconductor devices. Comprising the following steps: metalizing a welding area of a ceramic tube shell, and forming a metalized layer on the surface of the welding area; a solder height control board is provided, the solder height control board is provided with a plurality of limiting grooves used for containing solder and a metallization layer, the positions of the limiting grooves correspond to the positions of the welding areas of the ceramic tube shell in a one-to-one mode, and the solder is placed in the limiting grooves of the solder height control board; and the ceramic tube shell is attached to the solder height control plate, the metallization layer is made to make contact with the solder in the corresponding limiting groove, the ceramic tube shell and the solder height control plate which are attached are heated at the same time, the solder is melted, the solder is cooled, and the gold-tin solder is preset on the ceramic tube shell. The height of the preset gold-tin solder on the ceramic tube shell can be kept consistent, and the assembly stability and the contact stability during packaging of the ceramic tube shell can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor devices, and more particularly to a method for pre-setting gold-tin solder on a ceramic tube shell. Background Art

[0002] Packaging is a form of protection for chips in the electronics field. According to the type of packaging materials, there are mainly metal packaging, plastic packaging, ceramic packaging, etc.

[0003] Ceramic shell, also known as ceramic package shell, refers to a package shell made of ceramic as raw material. Ceramic shell can provide airtight sealing protection for chips. Ceramic shell has excellent mechanical properties, thermal stability, insulation performance, airtightness, moisture resistance, light-proof performance, etc. It is one of the commonly used electronic packaging materials and can be widely used as the shell of electric vacuum tube switches, high-frequency high-power electron tubes, and large-scale integrated circuits. Terminal application fields include 5G communications, aerospace, etc.

[0004] With the advancement of microelectronic packaging technology, components are developing towards miniaturization, high performance and high reliability. Ceramic tube shells use HTCC (high temperature co-fired multilayer ceramics) ceramics as circuit substrates, contain a variety of microwave transmission structures, and use metal parts to achieve isolation, airtightness and heat dissipation functions. They are used in microwave multi-chip modules, components and subsystems. They are the current trend of miniaturization and integration of electronic equipment. The integrated technology of substrate integration and three-dimensional packaging structure can meet the system and subsystem packaging requirements of electronic equipment, with compact structure and high integration.

[0005] Ceramic tube shells usually have various shapes such as cylindrical and square, and usually have cavities and leads inside to meet different packaging requirements. However, due to the difficulty of three-dimensional processing such as grooving, cavitation, and drilling of ceramic materials, the processing defect rate and cost are high, and the current ceramic packaging tube shells mostly use a composite structure combining metal and ceramic materials.

[0006] In order to meet the requirements of heat dissipation, electrical interconnection, overall airtightness, and internal contaminant control, the single package of the ceramic tube shell needs to be welded at multiple locations at the same time to ensure that the internal circuit works in a stable environment, thereby improving the reliability of electronic components. The welding area of ​​the ceramic tube shell has the characteristics of scattered positions, different shapes, different sizes, and isolated islands of internal solder. It is required that the solder height of each part of the ceramic tube shell after welding is consistent to meet the assembly requirements, which is extremely difficult.

[0007] Moreover, in order to fix the solder on the ceramic shell, it is usually necessary to metallize the welding area of ​​the ceramic shell. The metallization treatment is to sinter the metal slurry on the ceramic surface. The metal slurry shrinks after sintering and curing on the ceramic shell. Therefore, due to the composition of the metal slurry and the sintering process, the metal slurry will appear on the surface of the ceramic shell. The surface is uneven due to the different shrinkage of the slurry, such as slurry pits or curved surfaces. Due to the existence of pits or curved surfaces, when the solder is fixed on the welding area of ​​the ceramic shell, the solder height will be inconsistent.

[0008] There is an existing technology that uses gold-tin solder paste to encapsulate ceramic tube shells. By taking advantage of the principle that solder does not wet in non-metallized areas, the uneven surface of the metallized area of ​​the ceramic tube shell can be ignored. However, since the solder paste generally contains flux, the inside of the ceramic cavity cannot be cleaned after encapsulation, and there will be pollution sources such as organic residues, affecting product reliability.

[0009] There is also an existing technology that first makes the solder into a solder sheet, and then mechanically punches and shears it into the required solder sheet shape to obtain a preformed solder sheet. After the welding area of ​​the ceramic tube shell is metallized, the preformed solder sheet is positioned, and a laser device is used to position and spot weld the preformed solder sheet on the metallized welding area of ​​the ceramic tube shell, and then it is packaged. However, due to the differences in processing and assembly, it is difficult to completely match the position of the preformed solder sheet with the position of the welding area of ​​the ceramic tube shell, and because the welding area is uneven, the preset coplanarity is affected, resulting in unstable solder bonding strength and position consistency of the welding area, and solder is prone to falling off. After the solder is preset, the solder height of the welding areas of the ceramic tube shell cannot be consistent, and the assembly requirements cannot be met. In severe cases, the amount of solder on one side becomes more and exceeds the welding edge, which may cause poor solder edge climbing and affect device performance. Summary of the invention

[0010] In order to overcome the existing deficiencies, the present invention provides a method for pre-setting gold-tin solder on a ceramic tube shell. When the ceramic tube shell is packaged and welded, the height of the gold-tin solder in various welding areas of the ceramic tube shell can be kept consistent.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions: A method for pre-placing gold-tin solder on a ceramic tube shell comprises the following steps: S1. The welding area of ​​the ceramic shell is metallized to form a metallization layer on the surface of the welding area; S2. Providing a solder height control board, the solder height control board is provided with a plurality of limit grooves for accommodating gold-tin solder and the metallization layer, the position of the limit groove corresponds to the welding area position of the ceramic shell, and the gold-tin solder is placed in the limit groove of the solder height control board; S3. The ceramic shell and the solder height control plate are bonded together so that the metallization layer contacts the corresponding limit groove of the gold-tin solder, and the bonded ceramic shell and the solder height control plate are heated at the same time to melt the gold-tin solder, and the gold-tin solder is cooled to achieve the pre-set gold-tin solder on the ceramic shell; The material of the solder height control plate is a gold-tin non-wetting material; The depths of the limiting grooves are the same.

[0012] During the actual operation, the solder height control board is placed on a plane with the limiting groove facing upwards, the gold-tin solder is placed in the limiting groove, the ceramic tube shell is bonded to the solder height control board, and then the ceramic tube shell and the solder height control board are flipped 180° as a whole to make the metallization layer contact the gold-tin solder in the corresponding limiting groove, and then heat treated.

[0013] Preferably, the solder height control plate is made of graphite, ceramic or aluminum alloy.

[0014] More preferably, the solder height control plate is made of graphite.

[0015] Preferably, the shape of the cavity of the limiting groove matches the shape of the gold-tin solder.

[0016] The shape of gold-tin solder is generally flake or cylindrical.

[0017] The gold-tin solder is frame-shaped, the limiting groove is frame-shaped, the ratio of the outer dimension of the limiting groove to the outer dimension of the gold-tin solder is (1~1.5):1, and the ratio of the inner dimension of the limiting groove to the inner dimension of the gold-tin solder is 1:(1~1.5).

[0018] In practical applications, the ratio of the outer dimensions of the limiting groove to the outer dimensions of the gold-tin solder is 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, and 1.5:1.

[0019] In practical applications, the ratio of the inner dimension of the limiting groove to the inner dimension of the gold-tin solder is 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.5.

[0020] The gold-tin solder is a cylinder, the limiting groove is a cylinder, and the ratio of the diameter of the limiting groove to the diameter of the gold-tin solder is (1~1.5):1.

[0021] In practical applications, the ratio of the diameter of the limiting groove to the diameter of the gold-tin solder is 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, and 1.5:1.

[0022] The shape of the limiting groove is frame-shaped, cylindrical or rectangular, which is convenient for processing on the one hand, and can control the shape of one end of the gold-tin solder away from the welding area to be a plane on the other hand.

[0023] The gold-tin solder may be a binary alloy composed of Au and Sn, and preferably, the mass fraction of gold is 70%-80%.

[0024] The composition of the gold-tin solder is: Au mass fraction 70%-80%. By designing the composition deviation of the gold-tin solder, melting at different temperatures is achieved without affecting the subsequent packaging temperature.

[0025] Preferably, in step S3, the heating temperature is 300° C. to 350° C. After heating, a heat preservation treatment is also included, and the heat preservation time is 30 seconds to 90 seconds.

[0026] The heating temperature may be 300°C, 310°C, 320°C, 330°C, 340°C, or 350°C.

[0027] The insulation time can be 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, or 90 seconds.

[0028] Preferably, in step S3, the heating atmosphere is a vacuum atmosphere, an inert gas atmosphere or a reducing gas atmosphere.

[0029] The inert gas atmosphere may be nitrogen, argon or the like.

[0030] The reducing gas atmosphere is an atmosphere of formic acid or the like.

[0031] The heating atmosphere is a vacuum atmosphere or an inert gas atmosphere, which can prevent the molten gold-tin solder from being oxidized and is beneficial to improving the bonding strength between the gold-tin solder and the ceramic tube shell.

[0032] Preferably, the material of the welding area is one or more of a metal slurry layer, a copper frame, a copper column, a molybdenum frame, a molybdenum column or a kovar frame.

[0033] Preferably, the thickness of the gold-tin solder is 0.02-0.1 mm.

[0034] Preferably, the step of metallization treatment is: covering the surface of the welding area with at least one nickel layer and at least one gold layer.

[0035] The purpose of metallization treatment is to enable the gold-tin solder to be firmly bonded to the ceramic tube shell.

[0036] In practical applications, the nickel layer and the gold layer may be repeated in multiple layers in sequence, for example, nickel layer-gold layer, or nickel layer-gold layer-nickel layer-gold layer.

[0037] Preferably, the thickness of the metallization layer is 2.1-17.13 μm.

[0038] The total thickness of the nickel layer in the metallization layer may be 1.3-11.43 μm.

[0039] The total thickness of the gold layer in the metallization layer may be 0.8-5.7 μm.

[0040] In practical applications, the ratio of the depth of the limiting groove to the thickness of the gold-tin solder is (1~1.5):1.

[0041] In practical applications, the ratio of the depth of the limiting groove to the thickness of the gold-tin solder can be 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, or 1.5:1.

[0042] More preferably, the ratio of the depth of the limiting groove to the thickness of the gold-tin solder is (1~1.1):1.

[0043] Compared with the prior art, the present invention has the following beneficial effects: The method for pre-setting gold-tin solder on a ceramic tube shell of the present invention comprises the following steps: providing a solder height control plate, placing the gold-tin solder in a limiting groove of the solder height control plate, and then heating and heat-insulating the bonded solder height control plate and the ceramic tube shell. Since the material of the solder height control plate is a gold-tin non-wetting material, the molten gold-tin solder only wets the metallization layer area obtained after the metallization treatment of the ceramic tube shell. The molten gold-tin solder can be limited in the limiting groove of the solder height control plate. Since the depths of several limiting grooves are the same and the height of the gold-tin solder is limited, after the molten gold-tin solder is cooled, the height of the gold-tin solder pre-set on the ceramic tube shell can be kept consistent, and in particular, the surface of the gold-tin solder can be made almost flat.

[0044] During the welding of the ceramic shell package, the height of the gold-tin solder in each welding area of ​​the ceramic shell can be kept consistent, which is beneficial to improving the assembly stability and contact stability during the ceramic shell packaging. It is not easy to produce a lack of solder after the ceramic shell is packaged, thereby ensuring the electrical interconnection of the electronic devices.

[0045] Moreover, even if the ceramic slurry used to prepare the ceramic tube shell is prone to depressions or arcs on the surface of the ceramic tube shell after sintering, the present invention can ensure that the height of the gold-tin solder in various welding areas of the ceramic tube shell remains consistent, and can also balance the negative impact of the unevenness after sintering the ceramic slurry.

[0046] In addition, the present invention heats the ceramic tube shell and the gold-tin solder together, performs heat preservation treatment to melt the gold-tin solder, and can firmly combine the gold-tin solder on the welding area of ​​the ceramic tube shell. Compared with the gold-tin solder paste packaging ceramic tube shell method in the prior art, the present invention does not need to use flux, and does not need to clean the flux later, and can also achieve the gold-tin solder firmly combined with the welding area of ​​the ceramic tube shell.

[0047] Finally, the method of pre-setting gold-tin solder on the ceramic tube shell of the present invention facilitates mass production and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a top view of the solder height control board in Example 1.

[0049] Figure 2 This is a cross-sectional view of the solder height control board in Example 1.

[0050] Figure 3 This is a top view of the gold-tin solder in Example 1.

[0051] Figure 4 Schematic diagram of the method for pre-disposing gold-tin solder on a ceramic tube shell in Example 1.

[0052] Figure 5 This is a schematic diagram of the structure of pre-setting gold-tin solder on the ceramic tube shell in comparative example 1.

[0053] In the figure, 1-ceramic tube shell, 11-metallization layer, 2-solder height control board, 21-limiting groove, 3-gold-tin solder. DETAILED DESCRIPTION

[0054] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0055] Example 1 like Figures 1 to 4 As shown, a method for pre-setting gold-tin solder on a ceramic tube shell comprises the following steps: S1. The metallization treatment is performed in the welding area of ​​the ceramic shell 1 to form a metallization layer 11 on the surface of the welding area; S2. A solder height control board 2 is provided, on which a plurality of limit grooves 21 for accommodating the gold-tin solder 3 and the metallization layer 11 are provided, and the position of the limit groove 21 corresponds to the position of the welding area of ​​the ceramic shell 1, and the gold-tin solder 3 is placed in the limit groove 21 of the solder height control board 2; S3. The ceramic tube shell 1 is bonded to the solder height control board 2, so that the metallization layer 11 contacts the gold-tin solder 3 in the corresponding limiting groove 21, and the bonded ceramic tube shell 1 and the solder height control board 2 are heated at the same time to melt the gold-tin solder 3, and the gold-tin solder 3 is cooled to achieve pre-setting the gold-tin solder 3 on the ceramic tube shell 1; The depths of the limiting grooves 21 are the same.

[0056] in, In step S1, the welding area of ​​the ceramic tube shell 1 is a metal slurry layer. The welding area is a frame-shaped welding area, and the outer size of the frame is 15×15 mm, and the inner size of the frame is 14×14 mm.

[0057] The metallization treatment steps are as follows: a nickel layer and a gold layer are covered on the surface of the welding area, wherein the thickness of the nickel layer is 5 μm and the thickness of the gold layer is 3 μm.

[0058] The material of the solder height control plate 2 is graphite.

[0059] The size of the solder height control plate 2 is the same as the outer size of the ceramic tube shell 1. The shape of the limiting groove 21 is a frame shape with an outer size of 15.5×15.5 mm and an inner size of 13.5×13.5 mm. The depth of the limiting groove 21 is 0.055 mm.

[0060] In step S2, The gold-tin solder 3 is a frame-shaped solder, the thickness of the frame-shaped solder is 0.05 mm, the outer size of the frame-shaped solder is 15×15 mm, the inner size of the frame-shaped solder is 14×14 mm, and the thickness of the gold-tin solder is 0.05 mm.

[0061] The gold-tin solder 3 is a gold-tin alloy solder Au78Sn22, in which the mass fraction of gold is 78% and the mass fraction of tin is 22%.

[0062] In step S3, The heating temperature was 300° C., the holding time was 90 seconds, and the heating atmosphere was a nitrogen atmosphere.

[0063] Example 2 A method for pre-placing gold-tin solder on a ceramic tube shell, which is different from Example 1 in that: In step S1, the welding area of ​​the ceramic tube shell is a metal slurry layer, and the welding area is 10 circular welding areas with a diameter of φ0.4 mm.

[0064] The shape of the limiting groove is a cylinder, the diameter of the cylinder is φ0.4mm, and the depth is c=0.055mm.

[0065] In step S2, The gold-tin solder is 10 cylindrical solders, the diameter of the cylinder is φ0.3mm, and the height of the cylinder, i.e. the thickness of the gold-tin solder, is 0.05mm; The rest is the same as Example 1 and will not be described again here.

[0066] Example 3 A method for pre-setting gold-tin solder on a ceramic tube shell, The difference from Example 2 is that the material of the solder height control plate is aluminum alloy.

[0067] Example 4 A method for pre-setting gold-tin solder on a ceramic tube shell, The difference from Example 2 is: The shape of the limiting groove is a cylinder, the diameter of the cylinder is φ0.4mm, and the depth is c=0.07mm.

[0068] Example 5 A method for pre-setting gold-tin solder on a ceramic tube shell, The difference from Example 2 is that: The limiting groove is in the shape of a cylinder, with a diameter of φ0.45 mm and a depth of c=0.055 mm.

[0069] The gold-tin solder is in the form of 10 cylindrical solders, the diameter of the cylinder is φ0.4 mm, and the height of the cylinder, i.e., the thickness of the gold-tin solder, is 0.05 mm.

[0070] Comparative Example 1 A method for pre-placing gold-tin solder on a ceramic tube shell comprises the following steps: The gold-tin solder is the same as the solder in Example 2.

[0071] Place the gold-tin solder directly on the welding area of ​​the ceramic tube shell and heat it to melt in a nitrogen environment. The heating temperature is 300°C and the heating time is 90 seconds. After the gold-tin solder is cooled, a ceramic tube shell with gold-tin solder pre-placed is obtained. Figure 5 shown.

[0072] The difference from the first embodiment is that the solder height control plate 2 is not used.

[0073] Comparative Example 2 A method for pre-setting gold-tin solder on a ceramic tube shell, wherein the gold-tin solder is the same as the gold-tin solder in embodiment 2.

[0074] The gold-tin solder is placed directly on the welding area of ​​the ceramic tube shell for packaging, and a laser welding device is used to perform a positioning spot welding process on the gold-tin solder.

[0075] Results The gold-tin solder position, gold-tin solder height and gold-tin solder firmness of the ceramic tube shell pre-set with gold-tin solder in each embodiment and comparative example were tested.

[0076] The method for detecting the position of the gold-tin solder is as follows: visually observe the degree of deviation of the center of the gold-tin solder relative to the center of the welding area, and measure the deviation distance with a two-dimensional image measuring instrument.

[0077] The method for detecting the height of gold-tin solder is: detecting by a height gauge.

[0078] The method for the firmness test is: the ceramic tube shell pre-filled with gold-tin solder is dropped onto a rubber plate in a free-fall manner, the drop height is 50 cm, and the number of drops is 4 times.

[0079] The test results of each embodiment are shown in Table 1. The test results of each comparative example are shown in Table 2.

[0080] Table 1: Test results of various embodiments

[0081] Table 2: Test results of various comparative examples

[0082] It can be seen from Table 1 and Table 2 that, compared with the comparative example, the standard deviation of the height of the gold-tin solder is smaller when the method of pre-setting the gold-tin solder on the ceramic tube shell of the present invention is adopted, indicating that the height consistency of the gold-tin solder is excellent, and the center of the gold-tin solder is not offset relative to the center position of the welding area, and the gold-tin solder has excellent firmness.

[0083] It can be seen from the embodiment and comparative example 1 that since no solder height control plate is used, the upper space of the molten gold-tin solder is not restricted, the gold-tin solder will bulge in a hemispherical shape, and the standard deviation of the gold-tin solder height is too large, indicating that the gold-tin solder height consistency is very poor.

[0084] It can be seen from the embodiment and comparative example 2 that, since the solder height control plate is not used, the gold-tin solder is directly placed on the welding area of ​​the ceramic shell and spot-welded by laser welding. Although the gold-tin solder has excellent height consistency, the center of the gold-tin solder is greatly offset relative to the center of the welding area, and the firmness of the gold-tin solder is too poor.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for pre-placing gold-tin solder on a ceramic tube shell, characterized in that: The steps include: S1. The welding area of ​​the ceramic shell is metallized to form a metallization layer on the surface of the welding area; S2. Providing a solder height control board, the solder height control board is provided with a plurality of limit grooves for accommodating gold-tin solder and the metallization layer, the position of the limit groove corresponds to the welding area position of the ceramic shell, and the gold-tin solder is placed in the limit groove of the solder height control board; S3. The ceramic shell and the solder height control plate are bonded together so that the metallization layer contacts the corresponding limit groove of the gold-tin solder, and the bonded ceramic shell and the solder height control plate are heated at the same time to melt the gold-tin solder, and the gold-tin solder is cooled to achieve the pre-set gold-tin solder on the ceramic shell; The material of the solder height control plate is a gold-tin non-wetting material; The depths of the limiting grooves are the same.

2. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: The material of the solder height control plate is graphite, ceramic or aluminum alloy.

3. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: The shape of the cavity of the limiting groove matches the shape of the gold-tin solder.

4. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: In the gold-tin solder, the mass fraction of gold is 70%-80%.

5. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 4, characterized in that: In step S3, the heating temperature is 300°C to 350°C.

6. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 4, characterized in that: In step S3, the heating atmosphere is a vacuum atmosphere, an inert gas atmosphere or a reducing gas atmosphere.

7. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: The material of the welding area is one or more of a metal slurry layer, a copper frame, a copper column, a molybdenum frame, a molybdenum column or a kovar frame.

8. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: The thickness of the gold-tin solder is 0.02-0.1 mm.

9. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: The step of the metallization treatment is: covering the surface of the welding area with at least one nickel layer and at least one gold layer.

10. The method for pre-placing gold-tin solder on a ceramic tube shell as claimed in claim 1, characterized in that: The thickness of the metallization layer is 2.1-17.13 μm.

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