A method for unsealing a plastic-sealed copper-bonded lead semiconductor device

Abstract

The present invention belongs to the technical field of electronic component unsealing, and discloses a method for unsealing a plastic-sealed copper-bonded lead semiconductor device. The method comprises the following steps: locating the position of the device chip and identifying the type of bonding wire under X-ray, determining the unsealing plan and etching area; thinning the device's plastic encapsulation material using a laser; preparing a mixed solution of concentrated sulfuric acid, concentrated nitric acid, and benzotriazole and allowing it to stand; wrapping the device with tin foil and peeling it off until the area to be unsealed is exposed; heating the prepared solution in a preheated heating furnace; dripping the heated mixed solution with a dropper onto the area to be unsealed of the device; if the chip and the bonding wire of the device are not completely exposed, continuing to drip the heated mixed solution onto the area to be unsealed of the device until the chip and the bonding wire of the device are completely exposed; and ultrasonically cleaning the unsealed device. The method is simple to operate, requires low equipment requirements, and has high test efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic component unsealing, and in particular relates to an unsealing method for a plastic-sealed copper-bonded lead semiconductor device. Background Art

[0002] Copper has excellent electrical conductivity, exceeding that of gold and aluminum, and its heat dissipation is significantly superior to that of gold and aluminum. Furthermore, copper is stable and less susceptible to reaction with other metal compounds during the soldering process. Its high elongation and tensile strength facilitate bonding, enhancing device reliability. With the development of the integrated circuit packaging industry, copper bonding wire is increasingly used in plastic-encapsulated integrated circuits due to its unique advantages. During destructive physical analysis and failure analysis, chemical reagents are used to remove the plastic encapsulation compound from the chip surface, exposing the device's internal framework and chip. This is essential for internal visual inspection and subsequent white box analysis. Currently, the primary encapsulation compound used in plastic-encapsulated integrated circuits is a thermosetting polymer based on an epoxy resin system. Traditional decapsulation methods involve etching away the encapsulation compound using the strong oxidizing properties of fuming nitric acid or concentrated sulfuric acid. However, for plastic-encapsulated devices bonded with copper wire, the copper wire undergoes a chemical reaction and corrodes upon contact with concentrated acid. To preserve the device's bonding structure, an effective decapsulation method must be developed that removes the plastic encapsulation compound while maintaining the copper wire's intact bond shape. This facilitates subsequent internal packaging process inspections, power-on testing, and bond strength testing. Existing decapsulation methods utilize the strong oxidizing properties of fuming nitric acid or concentrated sulfuric acid to corrode the plastic encapsulation compound, exposing the chip. This approach is suitable for packaging structures with gold bond wires. However, copper is more chemically active than gold and reacts with heated concentrated sulfuric acid or nitric acid, corroding the copper bond wires and making subsequent testing impossible.

[0003] In order to solve the above technical problems, the existing related technologies are as follows:

[0004] (1) Add CuSO4·5H2O crystals to concentrated acid and use Cu 2+ The saturation effect can be opened, but the overall operation time of this method is relatively long and it is not suitable for large-scale production.

[0005] (2) Chemical electrolytic immersion and chemical low-temperature spray etching are used for unsealing. However, the chemical electrolytic immersion method requires special equipment and is relatively complicated to operate. The chemical low-temperature spray etching method allows the acid to fully contact the bonding wire, which is conducive to the reaction between the copper bonding wire and the acid. In addition, the unsealing time is long, which is less efficient for production.

[0006] (3) Low-temperature wet etching in a pure nitrogen environment. The disadvantage of this method is that it is too expensive and has very high requirements for equipment.

[0007] (4) Prepare a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:4 at a temperature of 300±10°C, soak the device, and heat the back of the device to open the seal.

[0008] Through the above analysis, the problems and defects of the existing technology are as follows:

[0009] (1) The existing technology adds CuSO4·5H2O crystals to concentrated acid for opening, and the overall operation time is relatively long, which is not suitable for large-scale production.

[0010] (2) The chemical electrolytic immersion method used in the prior art for opening the package requires special equipment and is relatively complicated to operate; the chemical low-temperature spray etching method used in the prior art for opening the package takes a long time to open the package and is less efficient in production.

[0011] (3) The low-temperature wet etching in a pure nitrogen environment in the prior art is too expensive and has very high requirements on equipment.

[0012] (4) The unsealing temperature is 300±10℃. If the temperature is too high, the acid activity will be too strong, and the rate cannot be accurately controlled. It is very easy to cause corrosion of the internal copper bonding wires, and the unsealing effect is not good. Summary of the Invention

[0013] In view of the problems existing in the prior art, the present invention provides a method for unsealing a plastic-sealed copper-bonded lead semiconductor device.

[0014] The present invention is achieved by providing a method for unsealing a plastic-sealed copper-bonded lead semiconductor device, the method comprising:

[0015] Step 1: Locate the device chip under X-ray and identify the type of bonding wire, determine the decapsulation plan and etching area; and use laser to thin the device's plastic packaging material.

[0016] Step 2: Prepare a mixed solution of concentrated sulfuric acid, concentrated nitric acid, and benzotriazole and allow it to stand; wrap the device with tin foil and peel it off until the area to be opened is exposed;

[0017] Step 3: Preheat the heating furnace and use the preheated heating furnace to heat the prepared solution; drip the heated mixed solution through a dropper and drop it onto the area of ​​the device to be unsealed;

[0018] Step 4: When the bonding wires of the chip and device are not completely exposed, continue to drip the heated mixed solution onto the area of ​​the device to be unsealed until the bonding wires of the chip and device are completely exposed; at the same time, perform ultrasonic cleaning on the unsealed device.

[0019] Furthermore, in step 1, the specific process of thinning the plastic packaging material of the device by laser is as follows:

[0020] The device's plastic packaging material is thinned by laser until the thickness is such that the chip's bonding wires can be seen. The height of the bonding wires is higher than the chip to avoid damage to the chip.

[0021] Furthermore, in the step 2, a mixed solution of concentrated sulfuric acid, concentrated nitric acid and benzotriazole is prepared and allowed to stand. The specific process is as follows:

[0022] Prepare a mixed solution of concentrated sulfuric acid, concentrated nitric acid and benzotriazole and let it stand. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:3.5, the concentration of benzotriazole is 1.7 mg / L, and the standing time is 5 to 6 minutes to fully dissolve.

[0023] The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:3.5, the concentration of benzotriazole is 1.7 mg / L, and the unsealing temperature is 115±5° C., so as to achieve chemical unsealing of the copper bonding wire.

[0024] Furthermore, in step 2, the device is wrapped with tin foil and peeled off to expose the area to be unsealed. The specific process is as follows:

[0025] Wrap the device with tin foil, and use a knife to peel off the tin foil in the area thinned by the laser to expose the area to be unsealed for subsequent acid drop test.

[0026] Furthermore, in step 3, the specific process of preheating the heating furnace is as follows:

[0027] Turn on the heating furnace and set the temperature of the heating furnace to 115±5℃ for preheating.

[0028] Furthermore, in step 3, the prepared solution is heated in a preheated furnace. The specific process is as follows:

[0029] The prepared solution is placed on a preheated heating furnace and heated for more than 5 minutes.

[0030] Furthermore, in step 3, the heated mixed solution is dripped through a dropper onto the area of ​​the device to be unsealed. The specific process is as follows:

[0031] The device wrapped in tin foil is placed on the operating table. The heated mixed solution is dripped into the area of ​​the device to be unsealed using a dropper. After reacting for 10-15 seconds, the device is removed with tweezers for observation.

[0032] Furthermore, in step 4, the specific process of ultrasonic cleaning the unsealed device is as follows:

[0033] Determine the ultrasonic cleaning solution, which includes acetone, alcohol and deionized water solution;

[0034] Clean with acetone or alcohol, then rinse with deionized water;

[0035] Finally, wash again with acetone or alcohol and place on filter paper to dry.

[0036] Another object of the present invention is to provide an application of the unsealing method of the plastic-sealed copper-bonded lead semiconductor device in reliability analysis of electronic components.

[0037] Another object of the present invention is to provide an application of the unsealing method of the plastic-sealed copper-bonded lead semiconductor device in unsealing a plastic-sealed copper-bonded lead integrated circuit.

[0038] In combination with the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solutions to be protected by the present invention from the following aspects:

[0039] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving these problems, this paper closely combines the technical solutions to be protected by the present invention and the results and data during the research and development process, and analyzes in detail and in depth how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about by solving the problems. The specific description is as follows:

[0040] The mixed solution configured in the present invention has an opening temperature, a volume ratio of concentrated sulfuric acid to concentrated nitric acid of 1:3.5, a benzotriazole concentration of 1.7 mg / L, and an opening temperature of 115±5°C, which together achieve chemical opening of the copper bonding wire. The ultrasonic cleaning sequence in the present invention is that the CuSO4 generated by the reaction is insoluble in organic solvents such as acetone and alcohol; the purpose of using acetone or alcohol for cleaning first is to remove acid residues on the bonding wire and the chip surface, and to prevent the concentrated acid from being diluted into a low-concentration acid when using deionized water for cleaning and reacting with the bonding wire; the purpose of using deionized water for cleaning is to remove the CuSO4 generated by the reaction; and the purpose of using acetone or alcohol for cleaning last is to remove residual water and other stains on the bonding wire and the chip surface. The present invention can retain the bonding structure of the device, and while the plastic encapsulation material is completely removed, it can also maintain the complete bonding shape of the copper wire, which is beneficial for subsequent internal packaging process inspection, power-on testing, bonding strength testing, and other tests.

[0041] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0042] The invention combines manual acid dripping with laser unsealing, has simple operation, low requirements on equipment, high test efficiency, and is suitable for unsealing plastic-sealed copper-bonded lead integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1This is a flow chart of a method for unsealing a plastic-encapsulated copper-bonded lead semiconductor device provided by an embodiment of the present invention;

[0044] Figure 2 Schematic diagram of the unsealing process of the plastic-sealed copper bond wire semiconductor device provided by an embodiment of the present invention;

[0045] Figure 3 The present invention provides a method for ultrasonically cleaning an unsealed device. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] like Figure 1 As shown, the unsealing method of the plastic-sealed copper bond wire semiconductor device provided by the embodiment of the present invention includes:

[0048] S101: Locate the chip position of the device under X-ray and identify the type of bonding wire, determine the decapsulation plan and etching area; thin the plastic packaging material of the device through laser.

[0049] S102: Prepare a mixed solution of concentrated sulfuric acid, concentrated nitric acid, and benzotriazole, and let it stand; wrap the device with tin foil and peel it off until the area to be unsealed is exposed.

[0050] S103: The heating furnace is preheated, and the prepared solution is heated by using the preheated heating furnace; the heated mixed solution is dripped through a dropper and dropped onto the area of ​​the device to be unsealed.

[0051] S104: When the bonding wires of the chip and the device are not completely exposed, continue to drip the heated mixed solution onto the area of ​​the device to be unsealed until the bonding wires of the chip and the device are completely exposed; at the same time, perform ultrasonic cleaning on the unsealed device.

[0052] In S101 provided in the embodiment of the present invention, the specific process of thinning the plastic packaging material of the device by laser is as follows:

[0053] The laser is used to thin the plastic packaging material of the device until the thickness is such that the bonding wires of the chip can be observed. The height of the bonding wires is generally higher than the chip to avoid damaging the chip.

[0054] In S102 provided in the embodiment of the present invention, a mixed solution of concentrated sulfuric acid, concentrated nitric acid and benzotriazole is prepared and allowed to stand for a specific process as follows:

[0055] Prepare a mixed solution of concentrated sulfuric acid, concentrated nitric acid and benzotriazole (C6H5N3) and let it stand. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:3.5, the concentration of benzotriazole is 1.7 mg / L, and the standing time is 5 to 6 minutes to allow it to fully dissolve.

[0056] The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:3.5, the concentration of benzotriazole is 1.7 mg / L, and the unsealing temperature is 115±5° C., so as to achieve chemical unsealing of the copper bonding wire.

[0057] In S102 provided in the embodiment of the present invention, the device is wrapped with tin foil and peeled off to expose the area to be unsealed. The specific process is as follows:

[0058] Wrap the device with tin foil, and use a knife to peel off the tin foil in the area thinned by the laser to expose the area to be unsealed for subsequent acid drop test.

[0059] In S103 provided by the embodiment of the present invention, the specific process of preheating the heating furnace is: the heating furnace is turned on, and the temperature of the heating furnace is set to 115±5° C. for preheating.

[0060] In S103 provided by the embodiment of the present invention, the specific process of heating the prepared solution by using the preheated heating furnace is as follows: the prepared solution is placed on the preheated heating furnace and heated for more than 5 minutes.

[0061] In S103 provided by the embodiment of the present invention, the heated mixed solution is dripped through a dropper onto the area of ​​the device to be unsealed. The specific process is as follows:

[0062] The device wrapped in tin foil is placed on the operating table. The heated mixed solution is dripped into the area of ​​the device to be unsealed using a dropper. After reacting for 10-15 seconds, the device is removed with tweezers for observation.

[0063] like Figure 3 As shown, in S104 provided in the embodiment of the present invention, the specific process of ultrasonic cleaning the unsealed device is as follows:

[0064] S201: Determine an ultrasonic cleaning solution, where the ultrasonic cleaning solution includes acetone, alcohol, and a deionized water solution.

[0065] S202: Clean with acetone or alcohol, then rinse with deionized water.

[0066] S203: Finally, wash again with acetone or alcohol and place on filter paper to dry.

[0067] In the above-mentioned order of ultrasonic cleaning of the device after unsealing S201 to S203, the CuSO4 generated by the reaction is insoluble in organic solvents such as acetone and alcohol. The purpose of using acetone or alcohol for cleaning first is to remove the acid residue on the bonding wire and the chip surface, and to avoid the concentrated acid being diluted into a low-concentration acid when using deionized water for cleaning and reacting with the bonding wire; the purpose of using deionized water for cleaning is to remove the CuSO4 generated by the reaction; and the purpose of using acetone or alcohol for cleaning finally is to remove the residual water and other stains on the bonding wire and the chip surface.

[0068] A method for unsealing a plastic-sealed copper-bonded lead semiconductor device provided by an embodiment of the present invention is applied to the reliability analysis industry of electronic components.

[0069] The present invention provides a method for unsealing a plastic-encapsulated semiconductor device with copper bond wires, suitable for unsealing plastic-encapsulated integrated circuits with copper bond wires. This method preserves the device's bonding structure, allowing for clean removal of the plastic encapsulation compound while maintaining the intact bonding shape of the copper wires. This facilitates subsequent internal packaging process inspections, power-on testing, and bond strength testing.

[0070] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for unsealing a plastic-sealed copper-bonded lead semiconductor device, characterized in that: The unsealing method of the plastic-sealed copper-bonded lead semiconductor device comprises: Step 1: Locate the device chip under X-ray and identify the type of bonding wire, determine the decapsulation plan and etching area; and use laser to thin the device's plastic packaging material. Step 2: Prepare a mixed solution of concentrated sulfuric acid, concentrated nitric acid, and benzotriazole and allow it to stand; wrap the device with tin foil and peel it off until the area to be opened is exposed; Step 3: Preheat the heating furnace and use the preheated heating furnace to heat the prepared solution; drip the heated mixed solution through a dropper and drop it onto the area of ​​the device to be unsealed; Step 4: If the bonding wires of the chip and device are not completely exposed, continue to drip the heated mixed solution onto the area of ​​the device to be unsealed until the bonding wires of the chip and device are completely exposed; at the same time, ultrasonically clean the unsealed device; In step 1, the specific process of thinning the plastic packaging material of the device by laser is as follows: The device's plastic packaging material is thinned by laser until the thickness is enough to see the chip's bonding wires. The height of the bonding wires is higher than the chip to avoid damage to the chip. In the step 2, a mixed solution of concentrated sulfuric acid, concentrated nitric acid and benzotriazole is prepared and allowed to stand. The specific process is as follows: Prepare a mixed solution of concentrated sulfuric acid, concentrated nitric acid and benzotriazole and let it stand. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:3.5, the concentration of benzotriazole is 1.7 mg / L, and the standing time is 5 to 6 minutes to fully dissolve. The volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:3.5, the concentration of benzotriazole is 1.7 mg / L, and the unsealing temperature is 115±5° C., so as to achieve chemical unsealing of the copper bonding wire.

2. The method for unsealing a plastic-sealed copper-bonded lead semiconductor device according to claim 1, wherein: In step 2, the device is wrapped with tin foil and peeled off to expose the area to be unsealed. The specific process is as follows: Wrap the device with tin foil, and use a knife to peel off the tin foil in the area thinned by the laser to expose the area to be unsealed for subsequent acid drop test.

3. The method for unsealing a plastic-sealed copper-bonded lead semiconductor device according to claim 1, wherein: In step 3, the specific process of preheating the heating furnace is as follows: Turn on the heating furnace and set the temperature of the heating furnace to 115±5℃ for preheating.

4. The method for unsealing a plastic-sealed copper-bonded lead semiconductor device according to claim 1, wherein: In step 3, the prepared solution is heated in a preheated furnace. The specific process is as follows: The prepared solution is placed on a preheated heating furnace and heated for more than 5 minutes.

5. The method for unsealing a plastic-sealed copper-bonded lead semiconductor device according to claim 1, wherein: In step 3, the heated mixed solution is dripped through a dropper onto the area of ​​the device to be unsealed. The specific process is as follows: The device wrapped in tin foil is placed on the operating table. The heated mixed solution is dripped into the area of ​​the device to be unsealed using a dropper. After reacting for 10-15 seconds, the device is removed with tweezers for observation.

6. The method for unsealing a plastic-sealed copper-bonded lead semiconductor device according to claim 1, wherein: In step 4, the specific process of ultrasonic cleaning the unsealed device is as follows: Determine the ultrasonic cleaning solution, which includes acetone, alcohol and deionized water solution; Clean with acetone or alcohol, then rinse with deionized water; Finally, wash again with acetone or alcohol and place on filter paper to dry.

7. Use of the unsealing method of a plastic-sealed copper-bonded lead semiconductor device according to any one of claims 1 to 6 in reliability analysis of electronic components.

8. Use of the unsealing method of a plastic-encapsulated copper-bonded lead semiconductor device according to any one of claims 1 to 6 in unsealing a plastic-encapsulated copper-bonded lead integrated circuit.

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