Flexible copper-clad plate cross section EBSD sample preparation method

Abstract

The invention relates to the technical field of detection sample preparation, in particular to a flexible copper-clad plate cross section EBSD sample preparation method which comprises the following steps: cutting at least two samples to be detected on a flexible copper-clad plate; stacking and gluing the at least two cut samples to be detected; carrying out conductive inlaying on the stacked sections of the stacked and glued samples; carrying out mechanical grinding and polishing treatment on the embedded sample; and after the mechanical polishing is completed, washing the surface of the sample to be detected until no polishing residual liquid exists on the surface, and finally, carrying out argon ion polishing treatment to obtain the flexible copper-clad plate section EBSD sample. According to the method, the cross section of the copper layer in the flexible copper-clad plate is completely preserved, and the limitation of high cost and small view of the EBSD sample of the cross section of the flexible copper-clad plate prepared by an ion thinning technology is broken through. The method has the advantages that good conductivity of the sample is guaranteed, image drifting in the detection process is avoided, the test efficiency is high, and the EBSD calibration rate can be stably kept to be 90% or above.

Description

Technical Field

[0001] The invention relates to the technical field of test sample preparation, and in particular to an EBSD sample preparation method for a cross section of a flexible copper-clad laminate. Background Art

[0002] As a special basic material for electronic interconnection, flexible copper clad laminates (FCCLs) are used to make flexible printed circuits with high wiring density, thinness, bendability, and three-dimensional assembly, which has promoted the development of thin, light, short, and small electronic products. The performance of the copper layer in the FCL is a key factor in determining the performance and life of the FCL. Therefore, studying the organizational structure of the copper layer in the FCL under different processes and parameters is of great significance for improving the process and developing FCLs with better performance. In addition to the organizational structure characteristics of the material surface, the organizational structure characteristics of the material cross section are equally important for evaluating the performance and structure of the material.

[0003] The backscattered electron diffraction (EBSD) analysis and characterization technology can provide key information such as the thickness, uniformity, internal quality, crystal structure and morphology of the material cross section, and is an important means of in-depth analysis of flexible copper clad laminates. The specimens used for EBSD testing require that the surface to be tested is smooth and flat, free of oxide film and residual processing strain layer. Therefore, sample preparation is the premise and key to EBSD analysis technology. Flexible copper clad laminates are mainly composed of flexible polyimide insulating base film and metal copper foil. They are thin, light and flexible, and their cross-section sample preparation is difficult.

[0004] The main method for preparing cross-sectional EBSD samples of flexible copper-clad laminates is currently ion thinning technology. However, ion thinning technology requires the sample to be made into a 60-100μm thin slice, which takes a long time to prepare, and it is impossible to take an EBSD image with a large field of view at one time. It requires multiple thinning and preparation, and then the EBSD image with a large field of view is obtained by splicing, which is extremely costly. Mechanical grinding and polishing technology is a traditional sample preparation method with low cost, but it may cause deformation of the cross section of the flexible copper-clad laminate due to the influence of material properties (such as Figure 1 Therefore, it is urgent to propose an improved mechanical grinding and polishing method to reduce cross-sectional deformation and obtain a large field of view EBSD image at one time, thereby reducing the sample preparation cost. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for preparing cross-section EBSD samples of flexible copper-clad laminates. The method can capture EBSD images with a large field of view at one time and has the advantages of simple sample preparation and low cost.

[0006] To achieve the above object, the present invention provides a method for preparing cross-section EBSD samples of a flexible copper-clad laminate, the steps of which include:

[0007] Step (1): cutting at least two samples to be tested on the flexible copper clad laminate;

[0008] Step (2): stacking and gluing at least two pieces of the samples to be tested cut in step (1);

[0009] Step (3): Conductively inlaying the stacked cross-section of the stacked and glued samples;

[0010] Step (4): mechanically grinding and polishing the mounted samples;

[0011] Step (5): After mechanical polishing is completed, the surface of the sample to be tested is rinsed until there is no polishing residue on the surface, and finally argon ion polishing is performed to obtain the EBSD sample of the cross section of the flexible copper clad laminate.

[0012] In step (2) of the present invention, the method of stacking more than two layers of flexible copper-clad laminates increases the area of ​​mechanical grinding and polishing, thereby improving the continuity of the copper layer.

[0013] Preferably, in step (1), the cut sample is ultrasonically cleaned.

[0014] Preferably, in step (2), the flexible copper-clad laminates are stacked in a manner of laminating copper surfaces to each other.

[0015] Preferably, in step (2), the adhesive used is a mixture of epoxy resin AB glue and copper powder. The preparation of the adhesive comprises the following steps: placing the epoxy resin AB glue in a container, adding 400-1000 mesh copper powder, and stirring and mixing well for use.

[0016] The method of using epoxy resin to bond the copper surface of the flexible copper clad laminate can resist the damage of the copper layer to the external force during mechanical grinding and polishing, improve the continuity of the copper layer, and reduce the bending deformation of the copper layer; adding appropriate copper powder to the epoxy resin can improve the conductivity of the flexible copper clad laminate, reduce image drift, and increase the EBSD calibration rate.

[0017] Preferably, in step (3), the conductive mounting is performed by cold mounting.

[0018] Preferably, the hot-pressed mounting material is graphite-type, and the cold-mounted mounting material is epoxy resin-type.

[0019] Preferably, in step (4), the pressure value of the mechanical grinding and polishing treatment is set to 1-3N, the speed of the grinding and polishing head is set to 50-80r / min, and the speed of the grinding and polishing disc is set to 150-240r / min.

[0020] Preferably, in step (4), the mechanical grinding and polishing process comprises the following steps:

[0021] The conductive embedded EBSD sample to be tested was ground on silica sandpaper, and the sandpaper grinding was from 400 mesh, 600 mesh, 800 mesh, 1000 mesh, 1200 mesh, 1500 mesh, 2000 mesh to 2500 mesh; the polishing agent used was 1.5μm diamond polishing agent and 0.02μm silica suspension, and the polishing time was 5min and 20min respectively.

[0022] Preferably, in step (5), the argon ion polishing time is 15-30 minutes.

[0023] Preferably, in the step (3), before the conductive embedding, the following step is also included: using metal blocks to fix the opposite sides of the stacked sample, and after fixation, the stacked cross section is exposed to the outside.

[0024] Preferably, the metal block is a conductive metal.

[0025] The method of fixing the stacked cross-section of the flexible copper clad laminate using a metal block can play a role in fixing the flexible copper clad laminate during the process of inlaying and mechanical grinding and polishing, thereby reducing the bending deformation of the flexible copper clad laminate.

[0026] Preferably, the method further comprises the following steps: after rinsing the surface of the sample to be detected by EBSD until there is no polishing residue on the surface, the sample to be detected by EBSD is subjected to argon ion polishing and EBSD testing to obtain a cross-sectional grain feature image and an EBSD calibration rate.

[0027] The method of the present invention has the following significant effects:

[0028] In the sample preparation method of the present invention, at least two layers of flexible copper-clad laminates are stacked and glued to increase the area of ​​mechanical grinding and polishing, improve the continuity of the copper layer, and completely preserve the cross section of the copper layer in the flexible copper-clad laminate, breaking through the high cost and small field of view of preparing cross-sectional EBSD samples of flexible copper-clad laminates by ion thinning technology. While meeting the requirements of high surface flatness, low stress value, and retaining the original surface stress distribution law of the sample to be tested, the sample ensures good conductivity of the sample, avoids image drift during the detection process, has high test efficiency, and enables the EBSD calibration rate to be stably maintained at more than 90%, greatly reducing the cost of EBSD sample preparation for the cross section of the flexible copper-clad laminate, and has high practical and promotion value in practical engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a cross-sectional micrograph of a flexible copper-clad laminate prepared by an unimproved mechanical grinding and polishing method.

[0030] Figure 2 It is a flow chart of preparing cross-section EBSD samples of flexible copper-clad laminates according to the present invention.

[0031] Figure 3 This is a sample diagram of the present invention in which a stainless steel clamp is used to clamp the copper metal block after the copper metal block is fixedly stacked and glued to the flexible copper clad laminate.

[0032] Figure 4 This is an EBSD test sample image after conductive cold mounting of the present invention.

[0033] Figure 5 It is a cross-sectional microscope image of the stacked and bonded multi-layer flexible copper clad laminate prepared by the present invention.

[0034] Figure 6 It is a SEM picture of the cross section of the flexible copper clad laminate prepared by the present invention.

[0035] Figure 7 It is an EBSD calibration rate diagram of the cross section of the flexible copper clad laminate prepared by the present invention.

[0036] Figure 8 This is an EBSD analysis diagram of the cross section of the flexible copper clad laminate prepared by the present invention. DETAILED DESCRIPTION

[0037] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0038] Example

[0039] A method for preparing cross-section EBSD samples of flexible copper-clad laminates, the flow chart is as follows: Figure 2 As shown, the following steps are included:

[0040] First, cut at least two samples of suitable size for EBSD testing from the flexible copper-clad laminate.

[0041] Put epoxy resin AB glue in a container, add an appropriate amount of 800 mesh copper powder, stir and mix thoroughly, and evenly apply it on the copper surface of the obtained flexible copper clad laminate, and then bond the copper surfaces of two flexible copper clad laminates coated with the mixed glue to each other.

[0042] Then use copper metal blocks to fix the stacked and glued flexible copper clad laminates, and clamp the copper metal blocks with stainless steel clips, such as Figure 3 shown.

[0043] Then, the sample stack sections fixed with copper metal blocks were cold mounted using epoxy conductive mounting material, such as Figure 4 shown.

[0044] The mounted EBSD samples to be tested are mechanically ground and polished. The main purpose of this step is to perform mechanical grinding and polishing to obtain a flat surface to be tested. Mechanical grinding and polishing uses a Huayin MP-3S-2 automatic grinding and polishing machine, with the pressure value set to 2N, the grinding and polishing head speed set to 50r / min, and the grinding and polishing disc speed set to 150r / min. The specific operation steps are: Grind the conductive mounted EBSD samples to be tested on silica sandpaper, and the sandpaper grinding is from 400 mesh, 600 mesh, 800 mesh, 1000 mesh, 1200 mesh, 1500 mesh, 2000 mesh to 2500 mesh; the polishing agent uses 1.5μm diamond polishing agent and 0.02μm silica suspension, and the polishing time is 5min and 20min respectively.

[0045] After mechanical polishing, rinse the surface of the sample until there is no polishing liquid residue on the surface.

[0046] The mechanically polished EBSD sample to be tested is subjected to argon ion polishing. The main purpose of this step is to remove the residual stress caused by the mechanical polishing process by argon ion polishing. The argon ion polishing time is 25 minutes. If the polishing time is too short, the residual stress caused by mechanical polishing cannot be eliminated. If the polishing time is too long, pits will form on the sample surface, affecting the subsequent EBSD analysis.

[0047] The cross-sectional EBSD sample of the flexible copper-clad laminate prepared by the present invention completely preserves the cross-sectional view of the copper layer in the flexible copper-clad laminate, and has a good cross-sectional protection effect. Figure 5 and 6 As shown; at the same time, it ensures good conductivity of the sample, avoids image drift during the detection process, and has high calibration accuracy, such as Figure 7 As shown in the figure, the red area is the EBSD calibration area, and the final calibration rate reaches more than 90%; the EBSD detection and analysis effect is good, such as Figure 8 shown.

[0048] The above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principle of the present invention, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A method for preparing cross-section EBSD samples of a flexible copper-clad laminate, characterized in that: The following steps are involved: Step (1): cutting at least two samples to be tested on the flexible copper clad laminate; Step (2): stacking and gluing at least two pieces of the samples to be tested cut in step (1); Step (3): Conductively inlaying the stacked cross-section of the stacked and glued samples; Step (4): mechanically grinding and polishing the mounted samples; Step (5): After mechanical polishing is completed, the surface of the sample to be tested is rinsed until there is no polishing residue on the surface, and finally argon ion polishing is performed to obtain the EBSD sample of the cross section of the flexible copper clad laminate.

2. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: In the step (2), the samples to be tested are stacked in such a way that the copper surfaces are attached to each other.

3. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: In the step (2), the adhesive used is a mixture of epoxy resin AB glue and copper powder.

4. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: In the step (3), the inlay is performed by conductive hot pressing or cold inlay.

5. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 4, wherein: The hot-pressed mounting material is graphite-type, and the cold-mounted mounting material is epoxy resin-type.

6. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: In the step (4), the pressure value of the mechanical grinding and polishing treatment is set to 1-3N, the speed of the grinding and polishing head is set to 50-80r / min, and the speed of the grinding and polishing disc is set to 150-240r / min.

7. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: In the step (4), the mechanical grinding and polishing process comprises the following steps: The conductive embedded EBSD sample to be tested was ground on silica sandpaper, and the sandpaper grinding was from 400 mesh, 600 mesh, 800 mesh, 1000 mesh, 1200 mesh, 1500 mesh, 2000 mesh to 2500 mesh; the polishing agent used was 1.5μm diamond polishing agent and 0.02μm silica suspension, and the polishing time was 5min and 20min respectively.

8. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: In the step (3), before the conductive embedding, the following step is also included: using metal blocks to fix the opposite sides of the stacked sample, and after fixing, the stacked cross section is exposed to the outside.

9. The EBSD sample preparation method for a cross section of a flexible copper-clad laminate according to claim 1, wherein: The metal block is a conductive metal.

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