A weldment with a pre-formed gold-tin bonding layer, its preparation method and application

Abstract

This invention discloses a pre-formed gold-tin bonding layer for a welded component, its preparation method, and its application, belonging to the field of soft soldering technology. The preparation method of the welded component uses a specially set mask as a template to perform special deposition of gold and tin layers. The resulting composite deposition layer has good diffusion effect of gold and tin layers after annealing treatment, and the gold-tin bonding layer has high component uniformity. The composition ratio of gold and tin matches the expected result highly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soldering, in particular to a welding piece with pre-placed gold-tin connecting layer and a preparation method and application thereof. BACKGROUND

[0002] Gold-based Au80Sn20 material has the characteristics of high yield strength, good fatigue resistance, good wettability, strong corrosion resistance, good electrical / thermal conductivity, and moderate brazing temperature, and is widely used in aerospace, automotive, communication and other fields as a solder connecting layer material.

[0003] At present, the forming method of pre-placed Au80Sn20 material connecting layer mainly includes the following two methods: the first method is to directly calender the ready-made Au80Sn20 material into a foil, and then solder it on the welding piece. This method is simple to operate, but since the Au80Sn20 material has high brittleness, the foil calendering can only be maintained at more than 10 μm, and it is impossible to prepare a thinner gold-tin connecting layer, the processing cost is high, the material utilization rate is low, and the foil obtained by calendering is easily oxidized in the subsequent hot rolling process, affecting the product quality. The second method is to alternately electroplate gold layer and tin layer on the entire welding surface until the desired thickness. Compared with the first method, the size controllability is high and the material utilization rate is high, but the composite coating obtained by this process has low uniformity of mutual diffusion of gold and tin during soldering, and it is difficult to obtain a gold-tin connecting layer with uniform composition and accurate element ratio. In addition, there is also prior art to electroplate gold and tin at the same time to obtain a gold-tin connecting layer in one step, but the composition uniformity and composition ratio accuracy of the product are still difficult to meet the expectations, and the process has too many interference factors, making it difficult to mass produce in factories. SUMMARY

[0004] Based on the defects of the prior art, the purpose of the present application is to provide a preparation method of a welding piece with pre-placed gold-tin connecting layer. The method uses a specially set mask as a template for the special deposition of gold layer and tin layer. The composite deposition layer obtained has good diffusion effect of gold layer and tin layer after annealing treatment, and the gold-tin connecting layer formed has high composition uniformity, and the composition ratio of gold and tin matches the expected results well.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A preparation method of a welding piece with pre-placed gold-tin connecting layer, comprising the following steps:

[0007] (1) depositing a first gold layer on the welding surface substrate; the thickness of the first gold layer is ≤0.2 μm;

[0008] (2) covering the first gold layer with a first mask, the first mask being provided with a plurality of hollow circular holes distributed in a grid pattern, the area ratio of the hollow circular holes on the first mask being 48-52%, and the area of a single hollow circular hole in the first mask being ≤0.05mm 2 ;

[0009] (3) depositing a first tin layer on the hollow circular hole area of the first mask, the thickness ratio of the first tin layer to the first gold layer being (3.8-4.2):1;

[0010] (4) removing the first mask, then covering the first tin layer with a second mask and depositing a second gold layer on the area not covered by the second mask, the thickness of the second gold layer being the same as that of the first tin layer;

[0011] (5) removing the second mask, then depositing a third gold layer on the plane of the first tin layer and the second gold layer; the thickness of the third gold layer being the same as that of the first gold layer;

[0012] (6) covering the third gold layer with a first mask and depositing a fourth gold layer on the hollow circular hole area of the first mask, the thickness of the fourth gold layer being the same as that of the first tin layer;

[0013] (7) removing the first mask, then covering the fourth gold layer with a second mask and depositing a second tin layer on the area not covered by the second mask, the thickness of the second tin layer being the same as that of the fourth gold layer;

[0014] (8) removing the second mask, then repeating steps (1)-(7) until the resulting composite deposition layer reaches a predetermined thickness, and after annealing treatment, the soldering piece of the preset gold-tin connecting layer is obtained; the temperature during the annealing treatment being 200-220℃.

[0015] The existing pre-plated gold-tin connecting layer is generally obtained by directly calendering the existing gold-tin material Au80Sn20 into a foil and then soldering, or by using an alternating deposition method to form a composite gold-tin layer, and then annealing to make the layers diffuse with each other to obtain a gold-tin connecting layer. However, the former is limited by the brittleness of the Au80Sn20 material and cannot obtain a product with a relatively thin size, and the utilization rate of the material is low during the process, and the foil after calendering needs to be further hot-rolled, which is easy to be oxidized and affects the product quality. The latter can prepare products with various thicknesses, but the composition of the products is not uniform, and the element ratio is difficult to accurately control. Therefore, in the technical scheme of the present application, the inventor has developed a soldering piece with a pre-plated gold-tin connecting layer. During the preparation of the product, a first gold layer is first set as a bottom layer, then a first mask with a grid-distributed hollow circular hole is used as a deposition template to cover the first gold layer, a first tin layer with a specific thickness is deposited in the exposed area corresponding to the hollow circular hole, after the tin layer is deposited, the second mask is used to cover the cylindrical tin layer completely, and then the second gold layer is deposited on the first gold layer without the mask, and the thickness of the second gold layer is limited to be the same as that of the first tin layer. The second gold layer can uniformly wrap the tin layer and form a flat composite layer. Then, similar to the above steps, after depositing a gold layer on the composite layer, another composite layer with the same structure but with the positions of the gold layer and the tin layer interchanged is constructed using the first and second masks, and finally a complete composite deposition layer is formed. The composite deposition layer can be repeatedly set according to actual needs to adjust the thickness of the final soldering piece, overcoming the defect that the product thickness cannot be adjusted in a large range due to the limitation of the process or material during the preparation of the product by the traditional process. The composite deposition layer obtained by the present application can diffuse between the first gold layer and the tin layer in the multiple composite layers during annealing, and at the same time, mutual diffusion will also occur between the tin layer and the second gold layer in the same composite layer plane. Therefore, the overall soldering piece has high composition uniformity after the formation of the gold-tin connecting layer. Based on the specific limitations of the thickness of the layers and the area ratio of the mask hollow circular hole, the gold-tin connecting layer formed can achieve a relatively accurate Au80Sn20 composition ratio, and the product has excellent use effect.

[0016] In addition, the inventor has found through experiments that, in terms of diffusion efficiency and diffusion uniformity, if the hollow structure in the first mask used during the deposition process of the tin layer is not a limited circular hole, the tin layer or the gold layer formed may not be able to diffuse uniformly during annealing, and the composition uniformity of the gold-tin connecting layer is not as expected.

[0017] Preferably, the area of a single hollow circular hole in the first mask is 0.01-0.05mm 2 .

[0018] More preferably, the area of a single hollow circular hole in the first mask is 0.01mm 2 , 0.015mm 20.02mm 2 0.03mm 2 0.04mm 2 0.05mm 2 0.06mm

[0019] The area size of the hollow circular hole determines the size of the deposited cylindrical tin layer, if the area is too large, the size of the prepared tin layer is too large, which will cause the distance of mutual diffusion of the gold layer and the tin layer in the same plane to be too far, and the in-plane diffusion effect is poor; but the area of the hollow circular hole is too small, which will increase the processing difficulty of the mask and increase the production cost, therefore, when the area of the hollow circular hole is preferably within the above range, the preparation difficulty of the overall product is low, the cost is low, and the quality of the prepared product is better.

[0020] Preferably, the thickness of the first gold layer and the third gold layer is 0.15-0.2 μm.

[0021] More preferably, the thickness of the first gold layer and the third gold layer is one or a range value of any two of 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm.

[0022] The thickness of the first gold layer and the third gold layer is related to the thickness of the tin layer and the formed composite layer, if the thickness of the first gold layer and the third gold layer increases, the thickness of the composite layer also increases, the diffusion distance between the upper and lower layers of the gold layer and the tin layer increases, and the diffusion uniformity between the layers decreases, but if the thickness of the first gold layer and the third gold layer is too thin, it may cause that the formed composite layer is too thin, and multiple deposition steps are needed to reach the expected thickness, the processing steps are increased, and the production cost is increased, and when the thickness of the first gold layer and the third gold layer is preferably within the above range, the production difficulty, production cost and product quality of the product can be considered, and the product production cost performance is higher.

[0023] Preferably, the first mask and the second mask are PET masks.

[0024] PET has good air tightness and mechanical properties, and has high adhesion to metal layers. It will not be penetrated during metal deposition, and has higher toughness and tensile strength than other polymer materials, and has good dimensional stability, and is therefore more suitable for the production process of the welding piece described in the application.

[0025] Preferably, in step (1), the welding surface substrate is also subjected to cleaning treatment before the deposition of the first gold layer, and the cleaning agent used in the cleaning treatment includes at least one of acetone and isopropyl alcohol.

[0026] Preferably, the deposition of the gold layer and / or the tin layer is carried out by electroplating.

[0027] Preferably, the vacuum degree during the annealing treatment is less than or equal to 200 Pa.

[0028] Preferably, the time during the annealing treatment is 3-4 hours.

[0029] The soldering piece with the preset gold-tin connecting layer has the special interlayer structure design, and after the annealing treatment of the composite deposition layer, the gold-tin component ratio of Au80Sn20 material can be accurately achieved, and the component uniformity of the formed gold-tin connecting layer is excellent, so that the soldering piece has excellent use effect.

[0030] During the annealing treatment, the preferred annealing conditions can effectively control the oxidation degree of the metal layer to a low level, and can guarantee the gold-tin diffusion effect of each layer at a low energy consumption, and the component uniformity of the product is more excellent.

[0031] Another purpose of the present application is to provide a soldering piece prepared by the preparation method of the soldering piece with the preset gold-tin connecting layer, which comprises a soldering surface substrate and a gold-tin connecting layer.

[0032] Preferably, the mass ratio of gold element and tin element in the gold-tin connecting layer formed after the annealing treatment of the composite deposition layer is (78:22)-(82:18).

[0033] Another purpose of the present application is to provide the application of the soldering piece with the preset gold-tin connecting layer in soft soldering.

[0034] The present application has the advantages that the present application provides a preparation method of a soldering piece with a preset gold-tin connecting layer, which performs special deposition of a gold layer and a tin layer by using a mask with a specific setting as a template, and the diffusion effect of the gold layer and the tin layer is good after the annealing treatment of the obtained composite deposition layer, the component uniformity of the formed gold-tin connecting layer is high, and the component ratio of gold and tin is highly matched with the expected result. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic view of the soldering piece with the preset gold-tin connecting layer of the present application when the first mask covers the first gold layer during preparation.

[0036] Figure 2 It is a schematic view of the soldering piece with the preset gold-tin connecting layer of the present application when the second mask covers the first tin layer during preparation.

[0037] Figure 3 It is a schematic view of the structure of the soldering piece with the preset gold-tin connecting layer of the present application before the annealing treatment.

[0038] Figure 4 It is a schematic view of the structure of the soldering piece with the preset gold-tin connecting layer of the present application after the annealing treatment. Detailed Implementation

[0039] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0040] Example 1

[0041] An embodiment of the pre-formed gold-tin bonding layer welded component, its preparation method, and its application according to the present invention, wherein the preparation method of the welded component includes the following steps:

[0042] (1) A first gold layer was deposited on the iron-cobalt-nickel alloy welding surface substrate after it was cleaned with acetone and isopropanol using an electroplating method; the diameter of the welding surface substrate was 8 mm; the thickness of the first gold layer was 0.15 μm; the electroplating process parameters were: plating bath temperature 55℃, current density 0.4 A / dm³. 2 Electroplating time: 3.5 min;

[0043] (2) Cover the first gold layer with a first mask, the first mask being a PET film, such as... Figure 1 As shown, the film has a grid-distributed array of perforated circular holes, each with an area of ​​0.01 mm². 2 The area of ​​the hollowed-out circular hole on the first mask accounts for 50%;

[0044] (3) Several cylindrical first tin layers are deposited in the hollow circular hole area of ​​the first mask using electroplating. The thickness of the first tin layer is 0.6 μm. The electroplating process parameters are: plating bath temperature 50℃, current density 1.5 A / dm³. 2 Electroplating time: 12 minutes;

[0045] (4) Remove the first mask, then cover the first tin layer with a second mask and deposit a second gold layer in the area where the second mask is not covered, such as... Figure 2 As shown, the thickness of the second gold layer is the same as the thickness of the first tin layer; the second mask is a PET film;

[0046] (5) Remove the second mask, and then deposit a third gold layer on the plane of the first tin layer and the second gold layer; the thickness of the third gold layer is the same as the thickness of the first gold layer.

[0047] (6) Cover the third gold layer with the first mask, and deposit the fourth gold layer in the hollow circular hole area of ​​the first mask, the thickness of the fourth gold layer being the same as the thickness of the first tin layer.

[0048] (7) Remove the first mask, then cover the second mask on the fourth gold layer and deposit a second tin layer in the area where the second mask is not covered, the thickness of the second tin layer being the same as the thickness of the fourth gold layer;

[0049] (8) Remove the second mask, and then repeat steps (1) to (7) until the resulting composite deposition layer reaches the predetermined thickness, approximately 10 μm. Figure 3 As shown; after annealing, the welded part with the pre-placed gold-tin bonding layer is obtained, such as... Figure 4 As shown;

[0050] The annealing process is performed under a vacuum of 200 Pa, at a temperature of 220 °C, and for 3.5 hours.

[0051] Example 2

[0052] The embodiment of the pre-placed gold-tin bonding layer of the present invention, its preparation method and application differs from Embodiment 1 only in that the thickness of the first gold layer is 0.2 μm and the thickness of the first tin layer is 0.8 μm.

[0053] Example 3

[0054] The embodiment of the pre-placed gold-tin bonding layer of the present invention, its preparation method and application differs from Embodiment 1 only in that the thickness of the first gold layer is 0.18 μm and the thickness of the first tin layer is 0.72 μm.

[0055] Example 4

[0056] The embodiment of the pre-formed gold-tin bonding layer weldment, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the area of ​​a single perforated circular hole on the first mask is 0.05 mm². 2 .

[0057] Example 5

[0058] The embodiment of the pre-formed gold-tin bonding layer welded component, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the area of ​​a single perforated circular hole on the first mask is 0.03 mm². 2 .

[0059] Example 6

[0060] The embodiment of the pre-placed gold-tin bonding layer welded component, its preparation method and application described in this invention differs from Embodiment 1 only in that the annealing temperature is 210°C.

[0061] Example 7

[0062] The embodiment of the pre-placed gold-tin bonding layer welded component, its preparation method and application described in this invention differs from Embodiment 1 only in that the annealing temperature is 200°C.

[0063] Comparative Example 1

[0064] A weldment with a pre-placed gold-tin bonding layer, its preparation method and application, differs from Example 1 only in that the thickness of the first gold layer is 0.3 μm and the thickness of the first tin layer is 1.2 μm.

[0065] Comparative Example 2

[0066] A weldment with a pre-placed gold-tin bonding layer, its preparation method, and its application differ from Example 1 only in that the area of ​​a single perforated circular hole on the first mask is 0.1 mm. 2 .

[0067] Comparative Example 3

[0068] A welding component with a pre-placed gold-tin bonding layer, its preparation method and application, differs from Example 1 only in that the hollow circular hole on the first mask is replaced with a hollow square hole of 0.1mm×0.1mm.

[0069] Comparative Example 4

[0070] A weldment with a pre-placed gold-tin bonding layer, its preparation method and application, differs from Example 1 only in that the annealing temperature is 150°C.

[0071] Comparative Example 5

[0072] A weldment with a pre-placed gold-tin bonding layer, its preparation method, and its application differ from Example 1 only in that the preparation method includes the following steps:

[0073] (1) A gold layer is deposited on the welding surface substrate of the iron-cobalt-nickel alloy material after cleaning with acetone and isopropanol by electroplating; the thickness of the gold layer is 0.15 μm.

[0074] (2) A tin layer is deposited on the gold layer by electroplating, the thickness of the tin layer being the same as that of the gold layer; the electroplating time is 3 min.

[0075] (3) Repeat steps (1) to (2) until the obtained composite deposition layer reaches the predetermined thickness, about 10 μm. After annealing, the welded part with the pre-placed gold-tin connection layer is obtained.

[0076] The annealing process is performed under a vacuum of 200 Pa, at a temperature of 220 °C, and for 3.5 hours.

[0077] Effect example

[0078] In order to verify the composition and composition uniformity of the welded parts of the present invention, the following steps are used to test the products of each example and comparative example:

[0079] The gold-tin connection layers of the products of each example and comparative example are divided into four equal parts in a "field" shape, and the EDS energy spectrometer is used to detect the composition of the center position of the gold-tin connection layer and the center position in each of the four equal parts (that is, the composition of 5 points is detected in total). Since the connection layer only contains two elements, gold and tin, it is only necessary to detect the mass content of tin element. Then, the average value and standard deviation of the mass content of tin element at 5 points are taken. The closer the average value of the mass content of tin element is to 20%, and the smaller the standard deviation, the closer the composition of the gold-tin connection layer is to the target value, and the smaller the composition fluctuation, that is, the better the quality of the gold-tin connection layer.

[0080] The test results are shown in Table 1.

[0081] Table 1 Test results

[0082] Item Average value of tin content (mass fraction, %) Standard deviation Example 1 20.18 0.271 Example 2 20.28 0.529 Example 3 20.26 0.493 Example 4 20.39 0.618 Example 5 20.32 0.575 Example 6 20.48 0.632 Example 7 20.53 0.658 Comparative Example 1 20.73 1.029 Comparative Example 2 20.66 0.710 Comparative Example 3 20.52 0.677 Comparative Example 4 20.86 1.039 Comparative Example 5 20.98 1.869

[0083] It can be seen from the test results that in the welded parts with the pre-set gold-tin connection layer of the present invention, the gold and tin components of the gold-tin connection layer are close to the ratio of 80:20, which fully meets the expected design of the Au80Sn20 material. At the same time, the product has high composition uniformity, and the test standard deviation is basically maintained within 0.66, and the lowest is only 0.271.

[0084] In contrast, in the preparation process of the products of Comparative Examples 1 to 3, the appropriate interlayer thickness and the size and shape of the hollow structure of the mask grid distribution were not selected, resulting in the inability to achieve uniform interlayer diffusion during the annealing process of the deposited composite deposition layer, and the product has poor composition uniformity; the annealing temperature of the product of Comparative Example 4 is insufficient, and the diffusion degree of the gold layer and the tin layer is insufficient, and the same effect cannot be achieved. Comparative Example 5 belongs to the existing formation process of the gold-tin connection layer. It forms a composite deposition layer by alternately depositing gold layers and tin layers with no special structure on the plane. The final product not only has poor composition uniformity, but also the composition ratio is difficult to achieve the expected result.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing a soldered piece of a pre-positioned gold-tin bonding layer, characterized in that The method comprises the following steps: (1) depositing a first gold layer on a solder surface substrate; the thickness of the first gold layer is ≤0.2 μm; (2) covering the first gold layer with a first mask, the first mask being provided with a plurality of hollow circular holes distributed in a grid, the area proportion of the hollow circular holes on the first mask being 48-52%; the area of a single hollow circular hole in the first mask being ≤0.05mm 2 ; (3) depositing a first tin layer on the hollow circular hole area of the first mask, the thickness ratio of the first tin layer to the first gold layer is (3.8-4.2):1; (4) removing the first mask, then covering a second mask on the first tin layer and depositing a second gold layer on the area not covered by the second mask, the thickness of the second gold layer is the same as that of the first tin layer; (5) removing the second mask, then depositing a third gold layer on the plane of the first tin layer and the second gold layer; the thickness of the third gold layer is the same as that of the first gold layer; (6) covering the first mask on the third gold layer, depositing a fourth gold layer on the hollow circular hole area of the first mask, the thickness of the fourth gold layer is the same as that of the first tin layer; (7) removing the first mask, then covering a second mask on the fourth gold layer and depositing a second tin layer on the area not covered by the second mask, the thickness of the second tin layer is the same as that of the fourth gold layer; (8) removing the second mask, then repeating steps (1)-(7) until the obtained composite deposition layer reaches a predetermined thickness, after annealing treatment, the soldering piece of the preset gold-tin connecting layer is obtained; the temperature during the annealing treatment is 200-220 ℃.

2. The method of claim 1, wherein the soldered member is a soldered member of a gold-tin interconnect layer. The area of the single hollowed-out circular hole in the first mask is 0.01-0.05 mm 2 .

3. The method of claim 1, wherein the soldered member is a soldered member of a gold-tin interconnect layer. The thickness of the first gold layer and the third gold layer is 0.15-0.2 μm.

4. The method of claim 1, wherein the soldered member is a soldered member of a gold-tin interconnect layer. The first mask and the second mask are PET masks.

5. The method of claim 1, wherein the soldered member is a soldered member of a gold-tin interconnect layer. In step (1), the solder surface substrate is further subjected to cleaning treatment before depositing the first gold layer; the cleaning agent used in the cleaning treatment comprises at least one of acetone and isopropyl alcohol.

6. The method of claim 1, wherein the soldered article is a soldered joint. The vacuum degree during the annealing treatment is ≤200 Pa.

7. The soldering piece prepared by the method for preparing the soldering piece of the preset gold-tin connecting layer according to any one of claims 1-6.

8. The weldment of claim 7, wherein, The soldering piece comprises a solder surface substrate and a gold-tin connecting layer.

9. The weldment of claim 8, wherein, The mass ratio of gold element to tin element in the gold-tin connecting layer is (78:22)-(82:18).

10. The application of the soldering piece according to any one of claims 7-9 in soft soldering.

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