A Cell Rework Process

Abstract

The present invention belongs to the technical field of semiconductor production, and specifically relates to a cell rework process. The present invention comprises the following steps: S1, soaking the cell in acetone stock solution for 9 to 11 minutes; S2, soaking the cell in a nitric acid solution with a volume ratio of 5% to 15% for 19 to 21 minutes; S3, soaking the cell in a sulfuric acid solution for 110 to 130 minutes; S4, soaking the cell in a first mixed acid; S5, washing the cell in an overflow tank with overflow water for 30 seconds; S6, soaking the cell in a hot water tank with a temperature of 40 to 60°C for 30 seconds; S7, soaking the cell in a second mixed acid for 50 to 70 seconds. S8, washing the cell in an overflow tank with overflow water for 30 seconds; S9, soaking the cell in a nitric acid solution with a volume ratio of 5% to 10% for 50 to 70 seconds; S10, electroplating tin on the surface of the copper particles of the cell for 10 to 20 minutes. The present invention is used to solve the technical problem that too many defective cells are produced in the prior art, which greatly reduces the yield rate of cell production.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor production, and in particular relates to a Cell rework process. Background Art

[0002] Cell is a semiconductor component in the semiconductor industry. Its basic structure is a crystal grain used as a chip inside, with welded copper grains or copper sheets outside the crystal grains, and white glue for packaging outside. There is also a tinned layer on the copper grains exposed outside the white glue, and the tinned layer is printed with ink fonts indicating the positive and negative poles. Cells generally fail in two ways after tinning: 1. Part of the cell is scrapped due to poor electrical properties during the final electrical test; 2. During storage, the tinned layer reacts with oxygen in the air to generate tin oxide, which can easily lead to poor assembly welding and scrapping. In actual production and use, the above reasons lead to too many scrapped cells, greatly reducing the production yield.

[0003] Therefore, how to improve the yield rate of Cell production has become a problem that needs to be solved urgently in this field. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a Cell rework process to solve the technical problem that too many defective Cells are produced by the prior art and the yield rate of Cell production is greatly reduced.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: A Cell rework process comprises the following steps:

[0006] S1, soaking the Cell in acetone solution for 9 to 11 minutes to remove the ink fonts on the surface of the Cell;

[0007] S2, soaking the cell obtained in the previous step in a nitric acid solution with a volume ratio of 5% to 15% for 19 to 21 minutes to remove the tin-plated layer on the surface of the cell;

[0008] S3, soaking the Cell obtained in the previous step in a sulfuric acid solution for 110-130 minutes to remove the white glue used for packaging the Cell, wherein the sulfuric acid solution is a mixture of sulfuric acid and water in a volume ratio of 7-9:1, and the mass fraction of the sulfuric acid is 98%;

[0009] S4, immersing the cell obtained in the previous step into a first mixed acid to remove the residual white glue in the previous step and to corrode the edges and burrs of the crystal grains in the cell;

[0010] S5, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the first mixed acid;

[0011] S6, placing the cell obtained in the previous step in a hot water pool at a temperature of 40-60° C. for 30 seconds to increase the temperature of the cell;

[0012] S7, soaking the Cell obtained in the previous step in a second mixed acid for 50 to 70 seconds to generate silicon dioxide on the surface of the Cell grains;

[0013] S8, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the second mixed acid;

[0014] S9, soaking the Cell obtained in the previous step in a nitric acid solution with a volume ratio of 5% to 10% for 50 to 70 seconds to remove the oxide layer on the surface of the copper particles of the Cell;

[0015] S10, electroplating tin on the surface of the copper particles of the Cell obtained in the previous step for 10 to 20 minutes to form a tin-plated layer.

[0016] The present invention mainly deals with two reasons for cell failure. The first is poor electrical properties of the chip in the cell. The poor electrical properties are caused by the edges and burrs of the grains in the cell during the manufacturing process. The first mixed acid can corrode the burrs and make the edges round, thereby changing the poor electrical properties. The second is the oxidation of the zinc plating layer. The electrical connectivity is restored by removing the tin and re-electroplating the tin.

[0017] Further: after step S10, the following steps are also provided:

[0018] S11, soaking the Cell obtained in the previous step in a second mixed acid for 50 to 70 seconds to remove metal ions;

[0019] S12, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the second mixed acid;

[0020] S13, soaking the Cell obtained in the previous step in an ammonia solution for 50 to 70 seconds to neutralize the metal ions generated in step S12, wherein the ammonia solution is a mixture of ammonia water: pure water in a volume ratio of 1: (2 to 4), and the mass fraction of the ammonia water is 26%;

[0021] S14, washing the Cell obtained in the previous step in pure water at a temperature of 60-80° C. for 30 seconds to remove the residual ammonia solution in the previous step;

[0022] S15, placing the Cell obtained in the previous step in an ultrasonic washing device for ultrasonic washing for 18 minutes to remove residual ammonia solution and metal ions;

[0023] S16, washing the Cell obtained in the previous step in pure water at a temperature of 70-90° C. for 30 seconds to remove residual impurities from the previous step.

[0024] The beneficial effect of adopting this step: through the above steps, the metal ions remaining after the electroplating tin are removed, and the conductive effect of the electroplating tin is ensured.

[0025] Further: a step S4' is added between step S4 and S5, and S4' is to immerse the obtained Cell in the first mixed acid again to further remove the residual white glue in the previous step, wherein the first mixed acid used in S4' is reused after being used in S4.

[0026] The beneficial effect of adopting this step: ensure that all residual white glue can be removed.

[0027] Further: after steps S9 and S10, the obtained Cell is placed in an isopropyl ketone stock solution.

[0028] The beneficial effect of adopting this step is that during the transfer process, the Cell is placed in the isopropyl ketone solution to prevent the Cell from contacting with air and causing oxidation.

[0029] Further: after steps S9, S10 and S16, the obtained Cell is placed in an isopropyl ketone stock solution.

[0030] The beneficial effect of this step is that during the transfer process and storage after completion, the Cell is placed in isopropyl ketone solution to prevent the Cell from contacting with air and causing oxidation.

[0031] Further: the first mixed acid is a mixture of nitric acid, hydrofluoric acid, glacial acetic acid and sulfuric acid in a volume ratio of 9:9:12-16:4, the mass fraction of the nitric acid is 70%, the mass fraction of the hydrofluoric acid is 49%, the mass fraction of the glacial acetic acid is 99.7%, and the mass fraction of the sulfuric acid is 98%;

[0032] The second mixed acid is a mixture of phosphoric acid, hydrogen peroxide and pure water in a volume ratio of 1:1:2-4, the mass fraction of the phosphoric acid is 85%, and the mass fraction of the hydrogen peroxide is 35%.

[0033] The beneficial effects of this step are as follows: the first mixed acid is used to remove residual white glue and to corrode the edges and burrs on the grains, and the second mixed acid is mainly used to generate a passivation layer and remove residual metal ions after tin electroplating.

[0034] The beneficial effects of the present invention are:

[0035] 1. The rework process of the present application can rework cells with poor electrical properties and cells with oxidized tin plating layers into qualified cells with good electrical properties;

[0036] 2. This rework process is a chemical immersion method, which is low-cost and highly operable. It can save cells with poor electrical properties, reduce production scrap rate, and increase yield by about 10%~15%. DETAILED DESCRIPTION

[0037] The following embodiments of the technical solution of the present invention are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0038] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0039] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0040] Example

[0041] A Cell rework process provided by the present invention comprises the following steps:

[0042] S1, soaking the Cell in acetone solution for 9 to 11 minutes to remove the ink fonts on the surface of the Cell;

[0043] S2, soaking the cell obtained in the previous step in a nitric acid solution with a volume ratio of 5% to 15% for 19 to 21 minutes to remove the tin-plated layer on the surface of the cell;

[0044] S3, soaking the Cell obtained in the previous step in a sulfuric acid solution for 110-130 minutes, removing the white glue used for encapsulation on the Cell, the sulfuric acid solution can be a mixture of sulfuric acid and water in a volume ratio of 7:1, or a mixture of sulfuric acid and water in a volume ratio of 9:1, and the mass fraction of the sulfuric acid is 98%;

[0045] S4, immersing the cell obtained in the previous step into a first mixed acid to remove the residual white glue in the previous step and to corrode the edges and burrs of the crystal grains in the cell;

[0046] S5, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the first mixed acid;

[0047] S6, placing the cell obtained in the previous step in a hot water pool at a temperature of 40-60° C. for 30 seconds to increase the temperature of the cell;

[0048] S7, soaking the Cell obtained in the previous step in a second mixed acid for 50 to 70 seconds to generate silicon dioxide on the surface of the Cell grains;

[0049] S8, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the second mixed acid;

[0050] S9, soaking the Cell obtained in the previous step in a nitric acid solution with a volume ratio of 5% to 10% for 50 to 70 seconds to remove the oxide layer on the surface of the copper particles of the Cell;

[0051] S10, electroplating tin on the surface of the copper particles of the Cell obtained in the previous step for 10 to 20 minutes to form a tin-plated layer.

[0052] The present invention mainly deals with two reasons for cell failure. The first is poor electrical properties of the chip in the cell. The poor electrical properties are caused by the edges and burrs of the grains in the cell during the manufacturing process. The first mixed acid can corrode the burrs and make the edges round, thereby changing the poor electrical properties. The second is the oxidation of the zinc plating layer. The electrical connectivity is restored by removing the tin and re-electroplating the tin.

[0053] After step S10, the following steps are further performed:

[0054] S11, soaking the Cell obtained in the previous step in a second mixed acid for 50 to 70 seconds to remove metal ions;

[0055] S12, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the second mixed acid;

[0056] S13, soaking the Cell obtained in the previous step in an ammonia solution for 50 to 70 seconds to neutralize the metal ions generated in step S12, wherein the ammonia solution is a mixture of ammonia water: pure water in a volume ratio of 1: (2 to 4), and the mass fraction of the ammonia water is 26%;

[0057] S14, washing the Cell obtained in the previous step in pure water at a temperature of 60-80° C. for 30 seconds to remove the residual ammonia solution in the previous step;

[0058] S15, placing the Cell obtained in the previous step in an ultrasonic washing device for ultrasonic washing for 18 minutes to remove residual ammonia solution and metal ions;

[0059] S16, washing the Cell obtained in the previous step in pure water at a temperature of 70-90° C. for 30 seconds to remove residual impurities from the previous step.

[0060] Through the above steps, the ammonia solution is used to remove the metal ions remaining after the electrotin plating, and the metal ions and the residual ammonia solution are completely removed through multiple water washings to ensure the conductive effect of the electrotin plating.

[0061] Wherein, step S4' is added between step S4 and step S5, and step S4' is to immerse the obtained Cell in the first mixed acid again to further remove the residual white glue in the previous step, wherein the first mixed acid used in S4' is reused after being used in S4.

[0062] Make sure that all the residual white glue is removed and remove the edges and burrs of the grains, making the grains more rounded and thus having good electrical properties.

[0063] Wherein, after steps S9 and S10, the obtained Cell is placed in an isopropyl ketone stock solution.

[0064] During the transfer process, the Cell is placed in an isopropyl ketone solution to prevent the Cell from coming into contact with air and causing oxidation.

[0065] Wherein, after steps S9, S10 and S16, the obtained Cell is placed in an isopropyl ketone stock solution.

[0066] During the transfer process and storage after completion, place the Cell in isopropyl ketone solution to prevent the Cell from contacting with air and causing oxidation.

[0067] The first mixed acid may be a mixture of nitric acid, hydrofluoric acid, glacial acetic acid and sulfuric acid in a volume ratio of 9:9:12:4, or a mixture of nitric acid, hydrofluoric acid, glacial acetic acid and sulfuric acid in a volume ratio of 9:9:16:4, wherein the mass fraction of the nitric acid is 70%, the mass fraction of the hydrofluoric acid is 49%, the mass fraction of the glacial acetic acid is 99.7%, and the mass fraction of the sulfuric acid is 98%;

[0068] The second mixed acid may be a mixture of phosphoric acid, hydrogen peroxide and pure water in a volume ratio of 1:1:2, or a mixture of phosphoric acid, hydrogen peroxide and pure water in a volume ratio of 1:1:4, wherein the mass fraction of the phosphoric acid is 85% and the mass fraction of the hydrogen peroxide is 35%.

[0069] The first mixed acid is used to remove residual white glue and corrode the edges and burrs on the grains, and the second mixed acid is mainly used to form a passivation layer on the grains and remove the metal ions remaining after tin electroplating.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Cell rework process, characterized in that: The following steps are involved: S1, soaking the Cell in acetone solution for 9 to 11 minutes to remove the ink fonts on the surface of the Cell; S2, soaking the cell obtained in the previous step in a nitric acid solution with a volume ratio of 5% to 15% for 19 to 21 minutes to remove the tin-plated layer on the surface of the cell; S3, soaking the Cell obtained in the previous step in a sulfuric acid solution for 110-130 minutes to remove the white glue used for packaging the Cell, wherein the sulfuric acid solution is a mixture of sulfuric acid and water in a volume ratio of 7-9:1, and the mass fraction of the sulfuric acid is 98%; S4, immersing the cell obtained in the previous step into a first mixed acid to remove the residual white glue in the previous step and to corrode the edges and burrs of the crystal grains in the cell; S5, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the first mixed acid; S6, placing the cell obtained in the previous step in a hot water pool at a temperature of 40-60° C. for 30 seconds to increase the temperature of the cell; S7, soaking the Cell obtained in the previous step in a second mixed acid for 50 to 70 seconds to generate silicon dioxide on the surface of the Cell grains; S8, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the second mixed acid; S9, soaking the Cell obtained in the previous step in a nitric acid solution with a volume ratio of 5% to 10% for 50 to 70 seconds to remove the oxide layer on the surface of the copper particles of the Cell; S10, electroplating tin on the surface of the copper particles of the Cell obtained in the previous step for 10 to 20 minutes to form a tin-plated layer; The first mixed acid is a mixture of nitric acid, hydrofluoric acid, glacial acetic acid and sulfuric acid in a volume ratio of 9:9:12-16:4, the mass fraction of the nitric acid is 70%, the mass fraction of the hydrofluoric acid is 49%, the mass fraction of the glacial acetic acid is 99.7%, and the mass fraction of the sulfuric acid is 98%; The second mixed acid is a mixture of phosphoric acid, hydrogen peroxide and pure water in a volume ratio of 1:1:2-4, the mass fraction of the phosphoric acid is 85%, and the mass fraction of the hydrogen peroxide is 35%.

2. The Cell rework process according to claim 1, characterized in that: After step S10, the following steps are further provided: S11, soaking the Cell obtained in the previous step in a second mixed acid for 50 to 70 seconds to remove metal ions; S12, placing the Cell obtained in the previous step in an overflow tank and washing with overflow water for 30 seconds to remove the second mixed acid; S13, soaking the Cell obtained in the previous step in an ammonia solution for 50 to 70 seconds to neutralize the metal ions generated in step S12, wherein the ammonia solution is a mixture of ammonia water: pure water in a volume ratio of 1: (2 to 4), and the mass fraction of the ammonia water is 26%; S14, washing the Cell obtained in the previous step in pure water at a temperature of 60-80° C. for 30 seconds to remove the residual ammonia solution in the previous step; S15, placing the Cell obtained in the previous step in an ultrasonic washing device for ultrasonic washing for 18 minutes to remove residual ammonia solution and metal ions; S16, washing the Cell obtained in the previous step in pure water at a temperature of 70-90° C. for 30 seconds to remove residual impurities from the previous step.

3. The Cell rework process according to claim 1 or 2, characterized in that: A step S4' is added between step S4 and step S5, wherein step S4' is to immerse the obtained Cell in the first mixed acid again to further remove the residual white glue in the previous step, wherein the first mixed acid used in S4' is reused after being used in S4.

4. The Cell rework process according to claim 1, characterized in that: After steps S9 and S10, the obtained Cell is placed in an isopropyl ketone stock solution.

5. The Cell rework process according to claim 2, characterized in that: After steps S9, S10 and S16, the obtained Cell is placed in an isopropyl ketone stock solution.