A method for preparing a partial cross-section of a flip chip solder joint

Abstract

The application provides a preparation method of a local cross section of a rotating chip welding point, and comprises the following steps: S1, positioning the rotating chip; S2, sticking the positioned rotating chip on the inner wall of a disposable mold according to the angle of the chip inclination through an adhesive; S3, configuring a sample embedding adhesive, pouring the sample embedding adhesive into the inclined disposable mold to obtain a sample through rotating chip sample embedding and solidification; S4, sequentially polishing, polishing and cleaning the sample to obtain a local cross section of a rotating chip welding point; and S5, photographing the local cross section of the rotating chip welding point to confirm the quality, and if the quality does not meet the requirements, repeating steps S1-S5 until the quality of the local cross section of the rotating chip welding point meets the requirements. The method is simple to operate, solves the technical problems that the rotating chip welding point is not easy to position and polish when the mold is cut obliquely, improves the quality of the local cross section of the rotating chip welding point, improves the conductive performance, and ensures the timeliness of product photography.

Description

Technical Field

[0001] This invention relates to the field of partial cross-section technology of semiconductor components, and specifically to a method for preparing a partial cross-section of a rotating chip solder joint. Background Technology

[0002] During the chip packaging process, when the chip is mounted according to the design requirements, there is a certain angle between the chip corners and the frame, and it is not parallel. After WB, the solder joint quality needs to be checked. The chip is tilted and glued to the waste product or vertically embedded in the mold, which makes it impossible to position during the dicing process. The phenomenon of slanted or overcut products often occurs, and each chip can only be polished manually, which is time-consuming.

[0003] During the SEM photo confirmation process, the product must be fixed horizontally on the base. It is difficult to fix the product if it is tilted, and it is easy to tip over. If the spacing between samples is too large, the conductivity will be poor, which will affect the timeliness and quality of product photography.

[0004] Existing methods for preparing local cross-sections of rotating chip solder joints have the following problems:

[0005] 1) The chip mounting position is irregular, and the chip and the frame have a certain angle. Conventional mounting is not easy to position, and the mold is cut at an angle, making it difficult to polish.

[0006] 2) When the mold is tilted, it is difficult to fix the product when it is tilted during SEM photography to confirm the sample. It is easy for the product to tip over, which affects the timeliness of product photography.

[0007] Therefore, how to avoid the difficulty in positioning and polishing the solder joints of rotating chips is a problem that urgently needs to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for preparing a local cross-section of a rotating chip solder joint. This method is simple to operate and solves the technical problems of difficulty in positioning and polishing rotating chip solder joints when the mold is cut at an angle. It improves the quality of the local cross-section of the rotating chip solder joint, enhances its conductivity, and ensures timely product photography.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] This invention provides a method for preparing a local cross-section of a rotating chip solder joint, comprising the following steps:

[0011] S1 positions the rotating chip;

[0012] S2 attaches the positioned rotating chip to the inner wall of the disposable mold using adhesive according to the tilt angle of the rotating chip;

[0013] S3 is configured with a mounting adhesive. The mounting adhesive is poured into an inclined disposable mold and the chip is rotated for mounting and curing to obtain the sample.

[0014] S4 sequentially grinds, polishes, and cleans the sample to obtain a local cross-section of the rotating chip solder joint;

[0015] S5 takes a photo of the cross-section of the local cross-section of the rotating chip solder joint to confirm its quality. If it does not meet the quality requirements, repeat steps S4-S5 until the cross-section of the local cross-section of the rotating chip solder joint is photographed to confirm that its quality meets the requirements.

[0016] The present invention provides a method for preparing a local cross-section of a rotating chip solder joint. It is simple to operate and solves the technical problems of difficult positioning and polishing of the rotating chip solder joint when the mold is cut at an angle. It improves the quality of the local cross-section of the rotating chip solder joint, improves the conductivity, and ensures the timeliness of product photography.

[0017] As a preferred technical solution, the adhesive in step S2 is either an acrylic adhesive or CH2=C(CN)-COO-C2H5.

[0018] As a preferred technical solution, the mounting adhesive in step S3 includes epoxy resin and curing agent, and the mounting adhesive is prepared by mixing the powder and liquid with an epoxy resin:curing agent weight ratio of 1.4:1.

[0019] As a preferred technical solution, the sample polishing in step S4 includes the following steps: first, use P400 mesh grit sandpaper to coarsely polish to a distance of 5μm to 10μm from the observation point for photo confirmation; then, use P2000 mesh grit sandpaper to finely polish the sample to the edge of the observation point for photo confirmation; and finally, use P4000 mesh grit sandpaper to finely polish to the observation point for photo confirmation.

[0020] As a preferred technical solution, step S4 involves polishing the sample after grinding, including the following steps: using 0.05μm Al2O3 polishing liquid for automatic polishing for 3 to 5 minutes to achieve mirror finish, with a polishing force of 9 to 11 N.

[0021] As a preferred technical solution, the cleaning of the polished sample in step S4 includes the following steps: performing multiple ultrasonic cleanings on the polished sample, blowing away water stains and foreign matter from the surface of the cleaned sample after cleaning, wiping the product cut surface on a polishing pad and observing whether it is cleaned under a low-power or high-power microscope, and obtaining a local cross-section of the rotating chip solder joint after cleaning.

[0022] As a preferred technical solution, when the rotating chip product is 3*3mm or larger, step S1 positions the rotating chip, including the following steps: extending the edge position extension line of the rotating chip to be ground to both sides of the pin, positioning according to the intersection of the pins on both sides and the extension line, and determining the tilt angle of the rotating chip.

[0023] As a preferred technical solution, when the rotating chip product is smaller than 3*3mm, step S1 positions the rotating chip, including the following steps:

[0024] S101 extends an auxiliary line parallel to the edge of the rotating chip to the frame;

[0025] S102 uses adhesive and liquid molding compound to apply the encapsulation material vertically above the chip.

[0026] Bake in S103, then trim, keeping the guide lines on the frame;

[0027] S104 positions the angle of the frame extension line to determine the tilt angle of the frame rotating chip.

[0028] As a preferred technical solution, the baking temperature in step S103 is 120-130℃; the baking time in step S103 is 25-35 minutes. Attached Figure Description

[0029] Figure 1 A flowchart of a method for partial cross-section of solder joints in a rotating chip product with a size of 3*3mm or larger, provided by the present invention;

[0030] Figure 2 A flowchart of a method for partial cross-section of solder joints in a rotating chip product with a size of 3*3mm or less, provided by the present invention;

[0031] Figure 3 SEM image of a partial cross-section of the rotating chip solder joint provided by the present invention;

[0032] Figure 4 for Figure 3 A partially enlarged SEM image of a local cross-section of the solder joint of the provided rotating chip. Detailed Implementation

[0033] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] It is understood that the present invention achieves its purpose through some embodiments. The method for preparing a partial cross-section of a rotating chip solder joint provided by the present invention includes the following steps:

[0035] S1 positions the rotating chip;

[0036] S2 attaches the positioned rotating chip to the inner wall of the disposable mold using adhesive according to the tilt angle of the rotating chip;

[0037] S3 is configured with a mounting adhesive. The mounting adhesive is poured into an inclined disposable mold and the chip is rotated for mounting and curing to obtain the sample.

[0038] S4 sequentially grinds, polishes, and cleans the sample to obtain a local cross-section of the rotating chip solder joint;

[0039] S5 takes SEM photos of the cross-section of the local cross-section of the rotating chip solder joint to confirm the quality. If the quality does not meet the requirements, repeat steps S4-S5 until the cross-section of the local cross-section of the rotating chip solder joint is photographed to confirm that the quality meets the requirements.

[0040] In step S2, the adhesive is either an acrylic adhesive or CH2=C(CN)-COO-C2H5.

[0041] The mounting adhesive in step S3 includes epoxy resin and curing agent. The epoxy resin and curing agent are mixed in a fume hood with a weight ratio of 1.4:1. The mixture is tilted at 15° to 25° and stirred at a constant speed in the same direction for 4 to 5 minutes to make the mounting adhesive completely mixed.

[0042] Among them, the rotating chip mounting curing in step S3 includes the following steps: placing it on a heating plate at 45-55°C to complete the curing;

[0043] The sample polishing process in step S4 includes the following steps: If the starting point of the sample polishing is far from the observation point for photo confirmation, a cutting machine can be used to cut the sample to a position closer to the observation point for photo confirmation before polishing. First, use P400 grit sandpaper to coarsely polish the sample to a position 5μm to 10μm away from the observation point for photo confirmation. Then, use P2000 grit sandpaper to finely polish the sample to the edge of the observation point for photo confirmation. Finally, use P4000 grit sandpaper to finely polish the sample to the observation point for photo confirmation.

[0044] In step S4, the sample after grinding is polished, which includes the following steps: using 0.05μm Al2O3 polishing liquid for automatic polishing for 3min to 5min to achieve mirror finish, with a polishing force of 9 to 11N.

[0045] The cleaning of the polished sample in step S4 includes the following steps: the polished sample is ultrasonically cleaned multiple times, and after cleaning, water stains and foreign objects on the surface of the cleaned sample are blown away. The product cut surface is wiped on the polishing pad and then placed under a low-power microscope or a high-power microscope to observe whether it is clean. After cleaning, a local cross-section of the rotating chip solder joint is obtained. If the polishing pad peels off or has holes during use, it should be replaced in time and should not be used anymore.

[0046] When the rotating chip product is larger than 3*3mm, step S1 positions the rotating chip, including the following steps: extending the edge position extension line of the rotating chip to be ground to both sides of the pin, positioning according to the intersection of the pins on both sides and the extension line, and determining the tilt angle of the rotating chip.

[0047] When the rotating chip product is smaller than 3*3mm, step S1 positions the rotating chip, including the following steps:

[0048] S101 extends an auxiliary line parallel to the edge of the rotating chip to the frame;

[0049] S102 uses adhesive and liquid molding compound to apply the encapsulation material vertically above the chip.

[0050] Bake in S103, then trim, keeping the guide lines on the frame;

[0051] S104 positions the angle of the frame extension line to determine the tilt angle of the frame rotating chip;

[0052] In step S103, the baking temperature is 120-130℃ and the baking time is 25-35 minutes.

[0053] The method for preparing a local cross-section of a rotating chip solder joint provided by this invention is simple to operate, solves the technical problems of difficult positioning and polishing of the rotating chip solder joint when the mold is cut at an angle, improves the quality of the local cross-section of the rotating chip solder joint, enhances the conductivity, and ensures the timeliness of product photography.

[0054] Example 1

[0055] like Figure 1 As shown, the method for preparing a partial cross-section of a rotating chip solder joint provided by the present invention includes the following steps:

[0056] S1 When the size of the rotating chip product is 3*3mm or larger, the rotating chip is positioned, including the following steps: extend the edge position extension line of the rotating chip to be ground to both sides of the pin, and position it according to the intersection of the pins on both sides and the extension line to determine the tilt angle of the rotating chip.

[0057] S2 attaches the positioned rotating chip to the inner wall of a disposable mold using acrylic adhesive according to the chip's tilt angle;

[0058] S3 is prepared by mixing epoxy resin and curing agent in a fume hood at a weight ratio of 1.4:1 (1.4:1). The mixture is tilted at 15° and stirred at a constant speed in the same direction for 4 minutes to ensure complete mixing of epoxy resin and curing agent. The mixture is then poured into a tilted disposable mold and the chip is rotated and placed on a 50°C heating plate to cure and obtain the sample.

[0059] S4 sequentially grinds, polishes, and cleans the sample to obtain a local cross-section of the rotating chip solder joint;

[0060] The sample molding process includes the following steps: first, use P400 mesh grit sandpaper to coarsely grind the sample to 5μm away from the observation point for photo confirmation; then, use P2000 mesh grit sandpaper to finely grind the sample to the edge of the observation point for photo confirmation; and finally, use P4000 mesh grit sandpaper to finely grind the sample to the observation point for photo confirmation.

[0061] The polishing of the sample after grinding includes the following steps: automatic polishing with 0.05μm Al2O3 polishing liquid for 4 minutes to achieve mirror finish, with a polishing force of 10N.

[0062] The polished sample was subjected to multiple ultrasonic cleanings. After cleaning, water stains and foreign matter on the surface of the cleaned sample were blown away. The product cut surface was wiped on the polishing pad and then placed under a low-power or high-power microscope to observe whether it was clean. After cleaning, a local cross-section of the rotating chip solder joint was obtained.

[0063] S5 takes SEM photos of the cross-section of the local cross-section of the rotating chip solder joint to confirm the quality. If the quality does not meet the requirements, repeat steps S4-S5 until the cross-section of the local cross-section of the rotating chip solder joint is photographed to confirm that the quality meets the requirements.

[0064] The method for preparing a local cross-section of a rotating chip solder joint provided by this invention is simple to operate, solves the technical problems of difficult positioning and polishing of the rotating chip solder joint when the mold is cut at an angle, improves the quality of the local cross-section of the rotating chip solder joint, enhances the conductivity, and ensures the timeliness of product photography.

[0065] Example 2

[0066] like Figure 2 As shown, the method for preparing a partial cross-section of a rotating chip solder joint provided by the present invention includes the following steps:

[0067] When the rotating chip product is smaller than 3*3mm, step S1 positions the rotating chip, including the following steps:

[0068] S101 extends an auxiliary line parallel to the edge of the rotating chip to the frame;

[0069] S102 uses adhesive and liquid molding compound to apply the encapsulation material vertically above the chip.

[0070] S103 is baked at 125℃ for 30 minutes, then trimmed, keeping the auxiliary lines on the frame.

[0071] S104 positions the angle of the frame extension line to determine the tilt angle of the frame rotating chip;

[0072] S2 attaches the positioned rotating chip to the inner wall of the disposable mold according to the tilt angle of the rotating chip using CH2=C(CN)-COO-C2H5;

[0073] In a fume hood, S3 is prepared by mixing epoxy resin and curing agent in a weight ratio of 1.4:1 (1.4:1). The mixture is tilted at 20° and stirred at a constant speed in the same direction for 5 minutes to ensure complete mixing of the epoxy resin and curing agent. The mounting adhesive is then poured into an inclined disposable mold and the chip is rotated and mounted on a 55°C heating plate for curing. During mounting, the guide lines should be kept basically parallel to the edge of the disposable mold to obtain the sample.

[0074] S4 sequentially grinds, polishes, and cleans the sample to obtain a local cross-section of the rotating chip solder joint;

[0075] The sample polishing process includes the following steps: first, use P400 mesh grit sandpaper to coarsely polish the sample to 10μm away from the observation point for photo confirmation; then, use P2000 mesh grit sandpaper to finely polish the sample to the edge of the observation point for photo confirmation; and finally, use P4000 mesh grit sandpaper to finely polish the sample to the observation point for photo confirmation.

[0076] The polishing of the sample after grinding includes the following steps: using 0.05μm Al2O3 polishing liquid for automatic polishing for 5 minutes to achieve mirror finish, with a polishing force of 9N;

[0077] The cleaning of the polished sample includes the following steps: the polished sample is ultrasonically cleaned multiple times, and after cleaning, water stains and foreign matter on the surface of the cleaned sample are blown away. The product cut surface is wiped on the polishing pad and then placed under a low-power microscope or a high-power microscope to observe whether it is clean. After cleaning, a local cross-section of the rotating chip solder joint is obtained.

[0078] S5 performs SEM photography on the cross-section of the local cross-section of the rotating chip solder joint to confirm the quality. If the quality does not meet the requirements, repeat steps S4-S5 until the cross-section of the local cross-section of the rotating chip solder joint is photographed to confirm that the quality meets the requirements.

[0079] The method for preparing a local cross-section of a rotating chip solder joint provided by this invention is simple to operate, solves the technical problems of difficult positioning and polishing of the rotating chip solder joint when the mold is cut at an angle, improves the quality of the local cross-section of the rotating chip solder joint, enhances the conductivity, and ensures the timeliness of product photography.

[0080] like Figure 3-4 As shown in the figure, we can observe that the spacing between the local cross-sections of the rotating chip solder joints obtained by the method of preparing the local cross-section of the rotating chip solder joint in Example 1 is small, the edges of the local cross-sections of the rotating chip solder joints are clear, the conductivity is improved, and the timeliness and quality of the cross-section of the local cross-section of the rotating chip solder joints are guaranteed.

[0081] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of this invention.

Claims

1. A method for preparing a local cross-section of a rotating chip solder joint, characterized in that, Includes the following steps: S1 positions the rotating chip; For rotating chip products with dimensions of 3*3mm or less, step S1 involves positioning the rotating chip, including the following steps: S101 extends an auxiliary line parallel to the edge of the rotating chip to the frame; S102 uses adhesive and liquid molding compound to apply the encapsulation material vertically above the chip. Bake in S103, then trim, keeping the guide lines on the frame; S104 positions the angle of the frame extension line to determine the tilt angle of the rotating chip; S2 attaches the positioned rotating chip to the inner wall of the disposable mold using adhesive according to the tilt angle of the rotating chip; S3 is used to prepare the mounting adhesive. The mounting adhesive is poured into the tilted disposable mold and the chip is rotated to mount and solidify to obtain the sample. During mounting, the auxiliary lines are kept parallel to the edge of the disposable mold. S4 sequentially grinds, polishes, and cleans the sample to obtain a local cross-section of the rotating chip solder joint; S5 takes a photo of the cross-section of the local cross-section of the rotating chip solder joint to confirm its quality. If it does not meet the quality requirements, repeat steps S4-S5 until the cross-section of the local cross-section of the rotating chip solder joint is photographed to confirm that its quality meets the requirements.

2. The method for preparing a local cross-section of a rotating chip solder joint according to claim 1, characterized in that, The adhesive used in step S2 is an acrylic adhesive.

3. The method for preparing a local cross-section of a rotating chip solder joint according to claim 1, characterized in that, The mounting adhesive in step S3 includes epoxy resin and curing agent, and is prepared by mixing the powder and liquid with an epoxy resin:curing agent weight ratio of 1.4:

1.

4. The method for preparing a local cross-section of a rotating chip solder joint according to claim 1, characterized in that, Step S4 involves polishing the sample, which includes the following steps: First, use P400 mesh grit paper to coarsely grind the sample to a distance of 5μm to 10μm from the observation point for photo confirmation. Then, use P2000 mesh grit paper to finely grind the sample to the edge of the observation point for photo confirmation. Finally, use P4000 mesh grit paper to finely grind the sample to the observation point for photo confirmation.

5. The method for preparing a partial cross-section of a rotating chip solder joint according to claim 1, characterized in that, Step S4 involves polishing the sample after grinding, including the following steps: using 0.05μm Al2O3 polishing liquid for automatic polishing for 3 to 5 minutes to achieve a mirror finish, with a polishing force of 9 to 11 N.

6. The method for preparing a partial cross-section of a rotating chip solder joint according to claim 1, characterized in that, Step S4 involves cleaning the polished sample, which includes the following steps: performing multiple ultrasonic cleanings on the polished sample, blowing away water stains and foreign matter from the surface of the cleaned sample after cleaning, wiping the product cut surface on a polishing pad and observing whether it is clean under a low-power or high-power microscope, and obtaining a local cross-section of the rotating chip solder joint after cleaning.

7. The method for preparing a partial cross-section of a rotating chip solder joint according to claim 1, characterized in that, The baking temperature in step S103 is 120-130℃; the baking time in step S103 is 25-35 minutes.

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