Interface alloy eutectic etching solution, etching method and sample preparation method

Abstract

The present application relates to a kind of interface alloy intermetallic compound etching solution, etching method and sample preparation method.Interface alloy intermetallic compound etching solution includes the following volume fraction of raw materials: ammonia 45%~55% and hydrogen peroxide 45%~55%;Wherein, the mass fraction of the ammonia is 25%~28%, and the mass fraction of the hydrogen peroxide is 30%~50%.The etching solution can etch tin, copper, silver, lead, gold, nickel and other multiple metals in interface alloy intermetallic compound at the same time by etching only once, and make each metal interface expose clear internal texture, which is beneficial to subsequent reliability analysis of circuit board.The raw materials of the interface alloy intermetallic compound etching solution are simple, low in cost, easy to prepare, short in etching time, and suitable for large-scale rapid experiment of interface alloy intermetallic compound.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intermetallic compound, and particularly to an intermetallic compound etching solution, an etching method and a sample preparation method. BACKGROUND

[0002] In the preparation process of various electronic devices, tin paste is usually printed on a circuit board, electronic components are placed on the tin paste by a chip mounter, and the tin paste, the plating layer on the surface of the circuit board and the plating layer on the surface of the electronic components are heated by reflow soldering to tightly contact with each other and transform into intermetallic compounds (IMC) to realize the functions of fixing electronic components and forming electrical connection. The formation of these intermetallic compounds is crucial for the reliability analysis and evaluation of whether the electronic components will fall off, whether the electrical connection is good, and whether the solder joints will crack during the use of the circuit assembly.

[0003] Metallographic analysis technology is one of important analysis means of the microstructure of metal materials, which needs to etch the surface of a section by using an etching solution and observe the internal organization morphology of the section under a scanning electron microscope (SEM). However, the traditional etching solution cannot etch multiple metals at the same time, which is not conducive to the metallographic analysis of intermetallic compounds. SUMMARY

[0004] Therefore, it is necessary to provide an intermetallic compound etching solution, an etching method and a sample preparation method to solve the problem that the traditional etching solution cannot etch multiple metals at the same time, which is not conducive to the metallographic analysis of intermetallic compounds.

[0005] The above-mentioned object of the present application is achieved by the following technical solutions:

[0006] In a first aspect, the present application provides an intermetallic compound etching solution, which comprises the following raw materials by volume fraction: ammonia water 45% to 55% and hydrogen peroxide 45% to 55%; wherein the mass fraction of the ammonia water is 25% to 28%, and the mass fraction of the hydrogen peroxide is 30% to 50%.

[0007] In one of the embodiments, the intermetallic compound etching solution comprises the following raw materials by volume fraction: ammonia water 48% to 52% and hydrogen peroxide 48% to 52%.

[0008] In one of the embodiments, the intermetallic compound etching solution comprises the following raw materials by volume fraction: ammonia water 49% to 51% and hydrogen peroxide 49% to 51%.

[0009] In a second aspect, the present application provides an etching method of intermetallic compounds, which comprises the following steps:

[0010] The interface alloy eutectic compound is etched by the interface alloy eutectic etching solution.

[0011] The components of the interface alloy eutectic compound include at least two of tin, silver, copper, lead, nickel and gold.

[0012] In one embodiment, the components of the interface alloy eutectic compound include tin, silver, copper and lead.

[0013] In a third aspect, the present application provides a sample preparation method, which comprises the following steps: providing a sample, and etching a surface to be detected of the sample by using the interface alloy eutectic etching solution.

[0014] In one embodiment, the etching time is 1-5 seconds.

[0015] In one embodiment, the sample is a circuit board sample, and the circuit board sample includes an interface alloy eutectic compound.

[0016] The components of the interface alloy eutectic compound include at least two of tin, silver, copper, lead, nickel and gold.

[0017] In one embodiment, the components of the interface alloy eutectic compound include tin, silver, copper and lead.

[0018] In one embodiment, the sample preparation method comprises the following steps:

[0019] The circuit board to be detected is cut, glued, ground and polished respectively.

[0020] The present application can etch tin, copper, silver, lead, gold and nickel in the interface alloy eutectic compound by using the interface alloy eutectic etching solution prepared by mixing ammonia and hydrogen peroxide in a suitable ratio, and the microstructure features of the metals are exposed clearly, which is beneficial to the subsequent reliability analysis of the circuit board. The etching solution has simple raw materials, low cost, convenient preparation and short etching time, and is suitable for large-scale rapid experiments of the interface alloy eutectic compound. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The metallographic images of the circuit board sample with tin-copper plating layer before and after etching in the prior art;

[0022] Figure 2 The metallographic image of the circuit board sample in Example 1 before etching;

[0023] Figure 3 The SEM image of the circuit board sample in Example 1 before etching;

[0024] Figure 4 SEM image of the etched circuit board sample in Example 1;

[0025] Figure 5 SEM image of the etched circuit board sample in Example 2;

[0026] Figure 6 SEM image of the etched circuit board sample in Example 3;

[0027] Figure 7 SEM image of the etched circuit board sample in Example 4;

[0028] Figure 8 SEM image of the etched circuit board sample in Comparative Example 1;

[0029] Figure 9 SEM image of the etched circuit board sample in Comparative Example 2.

[0030] Reference numerals: circuit board substrate 11, tin plating layer 12, copper plating layer 13; circuit board substrate 21, copper plating layer 22, silver plating layer 23, tin-silver plating layer 24, tin-lead solder layer 25; copper plating layer 31, tin-lead solder layer 32, tin-gold plating layer 33, gold plating layer 34, stainless steel layer 35. DETAILED DESCRIPTION

[0031] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application can be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present application. The purpose of the above summary is to enable the patent applicant to better and more effectively convey the nature of the application to the patent examiner.

[0032] In addition, the terms "first", "second", and the like, are used merely as a label to distinguish one component from another, and do not necessarily indicate any relative importance or any modification to the indicated technical features. Therefore, a component defined with "first", "second", etc. can include at least one of the component. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically defined.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0034] Interfacial intermetallic compound refers to a compound formed by atomic diffusion and migration between different metals in close contact. In the preparation of printed circuit boards, the surface plating of the circuit board usually includes chemical tin, chemical gold, chemical copper, electroplated nickel gold, and organic solderability preservative (OSP), etc.; the surface of the terminal of the electronic component has tin, nickel, silver, etc. plating; the solder used for welding includes lead-tin paste and lead-free tin paste, etc. Different combinations of different plating and different solder will form various interfacial intermetallic compounds. In the printed circuit board, the interfacial intermetallic compound usually refers to the intermetallic compound between tin, copper, gold, nickel, and silver.

[0035] Metallographic analysis technology is an important means to observe the formation of interfacial intermetallic compounds, which includes sampling, cutting, glue filling, grinding, polishing, etching, and observation, etc. The morphology of the section is observed and analyzed by using a metallographic microscope or SEM with appropriate magnification, and the corresponding image is output; as the plating layer on the surface of the circuit board and the electronic component becomes thinner and thinner, even reaching the nanometer level, the metallographic microscope cannot meet the observation requirements, and SEM is usually used for observation to avoid misjudgment. However, when the section is not etched, different plating layers can be observed in the section under the metallographic microscope by visible light imaging, but it is difficult to observe different plating layers and their internal microstructure characteristics by SEM through secondary electron imaging. Therefore, it is necessary to etch the section with a suitable etching solution to expose the internal structure morphology, so as to facilitate subsequent observation and detection.

[0036] Please refer to Figure 1 which are the metallographic images of the circuit board sample containing tin-copper plating layer in the prior art before and after etching. Among them, Figure 1 (a) ~ Figure 1 (d) are all observed and photographed by using a metallographic microscope with a magnification of 200 times, and the black part is the circuit board substrate 11, the dark gray part is the tin plating layer 12, and the light gray part is the copper plating layer 13. Figure 1 (a) is the metallographic image of the circuit board sample before etching, Figure 1 (b) is the metallographic image of the circuit board sample after etching with etching solution A, Figure 1 (c) is the metallographic image of the circuit board sample after etching with etching solution B, Figure 1 (d) is the metallographic image of the circuit board sample after etching with etching solution A and etching solution B, respectively. Etching solution A is an alcoholic solution of hydrochloric acid, which is mixed by mixing hydrochloric acid with a mass fraction of 36% to 38% and alcohol or isopropyl alcohol at a volume ratio of 1:19; etching solution B is an acidic solution of hydrogen peroxide, which is mixed by mixing hydrogen peroxide with a mass fraction of 30% and hydrochloric acid or nitric acid with a mass fraction of 36% to 38%.

[0037] FromFigure 1 (a) and Figure 1 From the comparison of (a) and (b), after etching the circuit board sample containing tin copper plating layer by using etching liquid A, the tin plating layer 12 shows obvious microstructure characteristics, but the copper plating layer 13 does not change, which indicates that the etching liquid A can only etch the tin plating layer 12. Figure 1 (a) and Figure 1 From the comparison of (a) and (c), after etching the circuit board sample by using etching liquid B, the copper plating layer 13 shows obvious microstructure characteristics, that is, a number of horizontal lines appear in the copper plating layer 13, which are the boundary lines formed during chemical copper deposition, but the tin plating layer 12 does not change, which indicates that the etching liquid B can only etch the copper plating layer 13. Figure 1 (a) and Example 1 From the comparison of (a) and (d), after etching by using etching liquid A and etching liquid B respectively, the tin plating layer 12 and the copper plating layer 13 both show obvious microstructure characteristics.

[0038] It can be seen that the commonly used etching liquid can only etch one kind of metal, in order to observe the microstructure morphology of all metal plating layers in the interface alloy intermetallic compound, at least two kinds of etching liquid need to be used. With the increase of the types of metal elements contained in the interface alloy intermetallic compound, the types of etching liquid used in etching also increase, which leads to the need of preparing multiple etching liquids and performing multiple etching during metallographic analysis, which is complicated and low in efficiency, and is very unfavorable for the large-batch and rapid sample preparation and analysis of the interface alloy intermetallic compound.

[0039] Based on this, the first aspect of the present application provides an interface alloy intermetallic compound etching liquid, which comprises the following raw materials by volume fraction: ammonia water 45% to 55% and hydrogen peroxide water 45% to 55%; wherein the mass fraction of the ammonia water is 25% to 28%, and the mass fraction of the hydrogen peroxide water is 30% to 50%.

[0040] After the ammonia water and the hydrogen peroxide water are prepared into the interface alloy intermetallic compound etching liquid in a suitable ratio, multiple metals such as tin, copper, silver, lead, gold and nickel in the interface alloy intermetallic compound can be etched at the same time by only one etching, and the interfaces of each metal are exposed to clear and distinct microstructure characteristics, which is beneficial to subsequent reliability analysis of the circuit board. The raw materials of the etching liquid are simple, the cost is low, the preparation is convenient, the etching time is short, and the etching liquid is suitable for large-batch and rapid experiments of the interface alloy intermetallic compound.

[0041] Understandably, the ammonia water is an aqueous solution of ammonia gas, and the mass fraction of the ammonia water refers to the mass fraction of ammonia gas in the aqueous solution thereof; the hydrogen peroxide water is an aqueous solution of hydrogen peroxide (H2O2), and the mass fraction of the hydrogen peroxide water refers to the mass fraction of H2O2 in the aqueous solution thereof.

[0042] In some embodiments, the interfacial alloy eutectic etching solution comprises the following volume fractions of raw materials: 48-52% ammonia water and 48-52% hydrogen peroxide.

[0043] In some embodiments, the interfacial alloy eutectic etching solution comprises the following volume fractions of raw materials: 49-51% ammonia water and 49-51% hydrogen peroxide.

[0044] In some embodiments, the water in the interfacial alloy eutectic etching solution is selected from one or more of tap water, pure water, deionized water, distilled water, and ultrapure water.

[0045] Adding a small amount of pure water, deionized water, distilled water, or ultrapure water to the interfacial alloy eutectic etching solution can make the etching effect of the interfacial alloy eutectic better and cleaner.

[0046] In some preferred embodiments, the volume fraction of pure water in the interfacial alloy eutectic etching solution is 1-5%.

[0047] In some more preferred embodiments, the volume fraction of pure water in the interfacial alloy eutectic etching solution is 1-3%.

[0048] In a second aspect, the present application provides an etching method of an interfacial alloy eutectic, comprising the following steps:

[0049] Etching the interfacial alloy eutectic with the interfacial alloy eutectic etching solution described above;

[0050] The components of the interfacial alloy eutectic include at least two of tin, silver, copper, lead, nickel, and gold.

[0051] The interfacial alloy eutectic etching solution can simultaneously etch metal elements such as tin, silver, copper, lead, nickel, and gold in a short time, and is very suitable for metallographic analysis of interfacial alloy eutectics.

[0052] In some embodiments, the components of the interfacial alloy eutectic include tin, silver, copper, and lead.

[0053] In a third aspect, the present application provides a sample preparation method, comprising the following steps: providing a test sample and etching the surface to be detected of the test sample with the interfacial alloy eutectic etching solution described above.

[0054] In some embodiments, the etching time is 1-5 seconds.

[0055] The interfacial alloy eutectic etching solution has a short etching time, which is beneficial for rapid analysis experiments on a large number of test samples containing interfacial alloy eutectics.

[0056] In some preferred embodiments, the etching time is 1s-3s.

[0057] In some embodiments, the sample is a circuit board sample, and the circuit board sample comprises an interfacial alloy eutectic.

[0058] In some embodiments, the components of the interfacial alloy eutectic comprise at least two of tin, silver, copper, lead, nickel, and gold.

[0059] In some embodiments, the components of the interfacial alloy eutectic comprise tin, silver, copper, and lead.

[0060] In some embodiments, the method for preparing the sample comprises the following steps:

[0061] A circuit board to be tested is taken, and is subjected to cutting, glue filling, grinding, and polishing, respectively.

[0062] It can be understood that the method for preparing the sample is a slicing method. Slicing (Cross-section, X-section) also known as metallographic slicing is a sample preparation method in which a sample is wrapped and sealed by a glue liquid prepared from a liquid resin and a curing agent in a certain proportion, and is subjected to grinding and polishing. Through slicing, a certain cross-section or profile of the sample can be obtained, and information about the composition and structure of the sample can be observed and analyzed through the cross-section or profile.

[0063] In some preferred embodiments, the method for preparing the sample comprises the following steps:

[0064] A circuit board to be tested is taken, and a part containing an interfacial alloy eutectic in the circuit board to be tested is cut off by a cutting machine to obtain a slice;

[0065] The slice is placed in a mold, and a surface to be tested of the slice faces the bottom surface of the mold; a glue liquid is injected into the mold, and the glue liquid comprises a liquid resin and a curing agent in a volume ratio of 3:1; after the glue liquid is completely cured, the mold is removed to obtain a glue body containing the slice;

[0066] The surface to be tested of the slice in the glue body is subjected to grinding and polishing to obtain a circuit board sample.

[0067] In some more preferred embodiments, the liquid resin is selected from one or more of an epoxy resin, a polyester, a phenolic resin, and an acrylic resin.

[0068] In some specific embodiments, the liquid resin is an epoxy resin.

[0069] The application will be further described in detail below with reference to specific examples. In the following examples, the raw materials used are commercially available products, unless otherwise specified.

[0070] Figure 2

[0071] The circuit board sample of the present embodiment comprises an interfacial alloy eutectic containing copper, silver, lead and tin.

[0072] (1) A circuit board to be tested is taken, and a part containing the interfacial alloy eutectic in the circuit board to be tested is cut off, ultrasonically cleaned, dried, and then sliced.

[0073] (2) The slice is placed in a mold with the surface to be tested facing the bottom surface of the mold, and adhesive liquid is injected into the mold, the adhesive liquid comprising liquid epoxy resin and curing agent in a volume ratio of 3:1. After the adhesive liquid is completely cured, the mold is removed, and a gel containing the slice is obtained.

[0074] (3) The surface to be tested of the slice in the gel is ground with sandpaper, and carefully polished with polishing cloth and polishing agent, and a circuit board sample is obtained. The surface to be tested of the circuit board sample is observed and photographed under a metallurgical microscope with a magnification of 200 times, and the result is shown in Figure 3 . The surface to be tested of the circuit board sample is observed and photographed under a SEM with a magnification of 1000 times, and the result is shown in Figure 2 .

[0075] In Figure 3 , the surface to be tested of the circuit board sample is sequentially the circuit board substrate 21, the copper plating layer 22, the silver plating layer 23, the tin-silver plating layer 24, the tin-lead solder layer 25, the tin-silver plating layer 24, the silver plating layer 23, the copper plating layer 22 and the circuit board substrate 21 from top to bottom, indicating that the interfacial alloy eutectic containing copper, silver, lead and tin is indeed formed in the circuit board. However, in a SEM image with a higher magnification, the boundary line of the circuit board sample is not very clear, especially the boundary line indicated by the arrow in Figure 4 , which is not clear and it is difficult to distinguish the silver plating layer 23, the tin-silver plating layer 24 and the tin-lead solder layer 25, and the crystal morphology inside each layer is also not etched out, so it is not possible to accurately determine the thickness and crystal condition of each layer in the interfacial alloy eutectic.

[0076] (3) Ammonia water with a mass fraction of 25%, hydrogen peroxide with a mass fraction of 30% and pure water are prepared into an interfacial alloy eutectic etching liquid in a volume ratio of 50:49:1, and the surface to be tested of the circuit board sample is etched for 2s using the interfacial alloy eutectic etching liquid. The surface to be tested of the circuit board sample is observed and photographed under a scanning electron microscope with a magnification of 1800 times, and the result is shown in Figure 4 .

[0077] In Figure 2In the circuit board sample, the surfaces to be tested, from top to bottom, are: circuit board substrate 21, copper plating layer 22, silver plating layer 23, tin-silver plating layer 24, tin-lead solder layer 25, tin-silver plating layer 24, silver plating layer 23, copper plating layer 22, and circuit board substrate 21. Example 2 Each layer corresponds to a specific layer, and the boundaries and internal textures of each layer are clearly defined. This allows for direct analysis of the thickness and crystallization of each plating and solder layer, facilitating subsequent reliability analysis and evaluation of the circuit board.

[0078] Figure 5

[0079] The metallographic analysis method in this embodiment is basically the same as that in Embodiment 1, except that the etching solution for the interface alloy compound is prepared by mixing 25% ammonia, 30% hydrogen peroxide, and pure water in a volume ratio of 45:50:5. The specific steps are as follows:

[0080] (1) Take the circuit board to be tested, cut off the part of the circuit board containing the interface alloy compound, clean it with ultrasonication, dry it, and obtain a slice.

[0081] (2) Place the slice in the mold with the test surface of the slice facing the bottom of the mold; inject adhesive into the mold, the adhesive comprising liquid epoxy resin and curing agent in a volume ratio of 3:1; remove the mold after the adhesive has completely cured to obtain a colloid containing the slice.

[0082] (3) Use sandpaper to grind the surface of the slice in the colloid to be tested, and use polishing cloth and polishing agent to carefully polish it to obtain the circuit board sample.

[0083] (4) An interface alloy chelate etching solution was prepared by mixing 25% ammonia, 30% hydrogen peroxide, and pure water in a volume ratio of 45:50:5. This etching solution was used to etch the surface of the circuit board sample to be inspected for 5 seconds. The surface was then observed and photographed using a scanning electron microscope with a magnification of 2000x. The results are as follows: Figure 5 As shown.

[0084] exist Example 3 In the circuit board sample, the test surfaces are arranged from top to bottom as follows: circuit board substrate 21, copper plating layer 22, silver plating layer 23, tin-silver plating layer 24, tin-lead solder layer 25, tin-silver plating layer 24, silver plating layer 23, copper plating layer 22 and circuit board substrate 21, and the boundaries and internal textures of each layer are clear and distinct.

[0085] Figure 6

[0086] The metallographic analysis method of this embodiment is basically the same as that of Embodiment 1, except that the interface alloy eutectic etching solution is prepared by mixing 25% ammonia water, 30% hydrogen peroxide and pure water in a volume ratio of 50:45:5. The specific steps are as follows:

[0087] (1) Take the circuit board to be tested, cut the part containing the interface alloy eutectic in the circuit board to be tested, ultrasonic clean, dry, and get the section.

[0088] (2) Place the section in the mold, and the detection surface of the section faces the bottom surface of the mold; inject the adhesive liquid into the mold, the adhesive liquid includes liquid epoxy resin and curing agent in a volume ratio of 3:1, remove the mold after the adhesive liquid is completely cured, and get the adhesive containing the section.

[0089] (3) Grind the detection surface of the section in the adhesive with sandpaper, and polish carefully with polishing cloth and polishing agent, and get the circuit board sample.

[0090] (4) Prepare the interface alloy eutectic etching solution by mixing 25% ammonia water, 30% hydrogen peroxide and pure water in a volume ratio of 50:45:5, etch the detection surface of the circuit board sample with the interface alloy eutectic etching solution for 5s, and observe and take pictures of the detection surface of the circuit board sample under a scanning electron microscope with a magnification of 1000 times, as shown in Figure 6 .

[0091] In Example 4 , the detection surface of the circuit board sample is composed of circuit board substrate 21, copper plating layer 22, silver plating layer 23, tin-silver plating layer 24, tin-lead solder layer 25, tin-silver plating layer 24, silver plating layer 23, copper plating layer 22 and circuit board substrate 21 from top to bottom, and the boundary lines and internal textures of each layer are clear.

[0092] Figure 7

[0093] The metallographic analysis method of this embodiment is basically the same as that of Embodiment 1, except that the circuit board sample includes interface alloy eutectic containing copper, gold, lead and tin. The specific steps are as follows:

[0094] (1) Take the circuit board to be tested, cut the part containing the interface alloy eutectic in the circuit board to be tested, ultrasonic clean, dry, and get the section.

[0095] (2) Place the section in the mold, and the detection surface of the section faces the bottom surface of the mold; inject the adhesive liquid into the mold, the adhesive liquid includes liquid epoxy resin and curing agent in a volume ratio of 3:1, remove the mold after the adhesive liquid is completely cured, and get the adhesive containing the section.

[0096] (3) Use sandpaper to grind the surface of the slice in the colloid to be tested, and use polishing cloth and polishing agent to carefully polish it to obtain the circuit board sample.

[0097] (4) An interface alloy chelate etching solution was prepared by mixing 25% ammonia, 30% hydrogen peroxide, and pure water in a volume ratio of 50:49:1. This etching solution was used to etch the surface of the circuit board sample to be inspected for 5 seconds. The surface was then observed and photographed using a scanning electron microscope with a magnification of 2500x. The results are as follows: Figure 7 As shown.

[0098] exist Comparative Example 1 In the circuit board sample, the test surfaces are arranged from top to bottom as follows: copper plating layer 31, tin-lead solder layer 32, tin-gold plating layer 33, gold plating layer 34, and stainless steel layer 35. The boundaries and internal textures of each layer are clearly defined.

[0099] Figure 8

[0100] The metallographic analysis method of this comparative example is basically the same as that of Example 1, except that the etching solution in step (3) is an alcoholic solution of hydrochloric acid.

[0101] An etching solution was prepared by mixing isopropanol and hydrochloric acid (36%–38% by mass) at a volume ratio of 95:5. This etching solution was used to etch the first cross-section of the sliced ​​sample obtained in step (2) of Example 1 for 5 seconds, exposing the third cross-section. The sliced ​​sample was then observed and photographed using a scanning electron microscope with a magnification of 1500x. The results are as follows: Figure 8 As shown.

[0102] exist Comparative Example 2 In the third section of the sliced ​​sample, only the copper plating layer 22 in the interfacial alloy complex could be observed. Most of the area in the middle of the copper plating layer 22 showed only slight etching marks. There were no clear boundaries between other plating layers or solder layers, and the internal microstructure of each layer could not be observed. This demonstrates that using only an alcoholic solution of hydrochloric acid as the etching solution for the interfacial alloy complex cannot produce a clear and distinct microstructure in SEM.

[0103] Figure 9

[0104] The metallographic analysis method in this comparative example is basically the same as that in Example 1, except that the etching solution for the interface alloy compound is prepared by mixing 25% ammonia, 30% hydrogen peroxide, and pure water in a volume ratio of 50:9:41. The specific steps are as follows:

[0105] (1) Take the circuit board to be tested, cut off the part of the circuit board containing the interface alloy compound, clean it with ultrasonication, dry it, and obtain a slice.

[0106] (2) Put the slice into a mold, and the surface to be detected of the slice faces the bottom surface of the mold; inject adhesive liquid into the mold, the adhesive liquid comprises liquid epoxy resin and curing agent in a volume ratio of 3:1, and the mold is removed after the adhesive liquid is completely solidified, to obtain an adhesive containing the slice.

[0107] (3) Grind the surface to be detected of the slice in the adhesive by using sandpaper, and carefully polish by using polishing cloth and polishing agent, to obtain a circuit board sample.

[0108] (4) Prepare an interfacial alloy eutectic etching solution by mixing ammonia water with a mass fraction of 25%, hydrogen peroxide with a mass fraction of 30% and pure water in a volume ratio of 50:9:41, etch the surface to be detected of the circuit board sample by using the interfacial alloy eutectic etching solution for 5s, and observe and take a photo of the surface to be detected of the circuit board sample in a scanning electron microscope with a magnification of 2000 times, and the result is shown in Figure 9 .

[0109] In ​ , the boundary line between the tin-silver plating layer 24 and the tin-lead solder layer 25 is completely invisible, and the crystal morphology inside each layer is also unclear, which indicates that when the amount of hydrogen peroxide in the etching solution is too small, the interfacial alloy eutectic etching cannot obtain obvious boundary line and clear crystal morphology.

[0110] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0111] The above-described embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. An interfacial alloy co-compound etching solution, characterized by, The raw materials include the following volume fractions: ammonia water 45-50%, hydrogen peroxide 45-50%, and 1-5% pure water; wherein the mass fraction of the ammonia water is 25-28%, and the mass fraction of the hydrogen peroxide is 30-50%; the composition of the interfacial alloy compound includes at least two of tin, silver, copper, lead, nickel, and gold.

2. The interfacial alloying compound etching solution of claim 1, wherein, The mass fraction of the ammonia water is 25%, and the mass fraction of the hydrogen peroxide is 30%.

3. An etching method of an interfacial alloying compound, characterized by, The method comprises the following steps: The interfacial alloy compound is etched by using the interfacial alloy compound etching solution according to any one of claims 1-2.

4. The etching method for interface alloy compounds as described in claim 3, characterized in that, The composition of the interfacial alloy compound includes tin, silver, copper, and lead.

5. A method of sample preparation, characterized by, The method comprises the following steps: A sample is provided, and the surface to be detected of the sample is etched by using the interfacial alloy compound etching solution according to any one of claims 1-2.

6. The sample preparation method of claim 5, wherein The etching time is 1-5 seconds.

7. The sample preparation method of claim 5, wherein The sample is a circuit board sample, and the circuit board sample includes an interfacial alloy compound.

8. The sample preparation method of claim 7, wherein, The composition of the interfacial alloy compound includes tin, silver, copper, and lead.

9. The sample preparation method of claim 7, wherein The preparation method of the sample comprises the following steps: The circuit board to be detected is cut, filled with glue, ground, and polished, respectively.

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