Method for removing brazing material on copper-clad ceramic substrate step by step

Abstract

The invention discloses a method for removing a brazing material on a copper-clad ceramic substrate step by step in the technical field of solder removal, and the method is used for removing the brazing material on the surface of the copper-clad ceramic substrate step by step and comprises the following steps: firstly, soaking the copper-clad ceramic substrate in a soaking pool to obtain a pretreated substrate; secondly, the pretreated substrate is placed in deionized water to be cleaned and dried, the upper surface and the lower surface of the dried pretreated substrate are evenly printed with a layer of thermosetting ink, curing is conducted, and a secondarily-treated substrate is obtained; finally, the secondary treatment substrate is placed in a hydrofluoric acid solution to be soaked and dried, the corrosion amount of liquid medicine to the copper layer can be effectively controlled in the solder removing process through the step-by-step method, and dotted copper pits appearing on the surface of the copper layer are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of solder removal, in particular to a method for removing solder from a copper-clad ceramic substrate in steps. Background Art

[0002] Common substrate materials used in power device packaging include metal, organic, and ceramic substrates. Ceramic substrates offer comparable mechanical strength and sealing properties to metal substrates, while also possessing similar insulation properties to organic substrates. Their thermal expansion coefficients are more closely aligned with chip materials, and their thermal conductivity is significantly higher than that of organic substrates, offering broad application and development prospects. Copper, due to its low price, excellent electrical and thermal conductivity, and ease of etching circuit patterns, is often fabricated by connecting Cu foil to ceramic and etching the Cu foil to form circuit patterns.

[0003] Copper-clad ceramic substrates are made by metallizing ceramics. The main components of the brazing material in the AMB process are silver and other active metals. However, in the solder removal process, silver is the main component removed. However, the existing solder removal method is a one-step etching method, which cannot effectively control the amount of etching on the copper layer during the solder removal process. In addition, the presence of acidic solutions (hydrofluoric acid solution) in the solder etching process will cause significant etching on the copper foil surface of the copper-clad substrate, thereby resulting in poor substrate performance. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for removing solder from a copper-clad ceramic substrate in steps.

[0005] The object of the present invention is achieved as follows: A method for removing solder from a copper-clad ceramic substrate in steps, comprising the following steps: Step 1: placing the copper-clad ceramic substrate in an immersion tank to obtain a pre-treated substrate; the immersion tank contains a removal solution, which is a mixed solution of KMnO4, NaOH, NH3·H2O and deionized water; Step 2: The pre-treated substrate is washed and dried in deionized water, and then a layer of thermosetting ink is evenly printed on the upper and lower surfaces of the dried pre-treated substrate and cured to obtain a secondary treated substrate; Step 3: Soak the secondary processed substrate in a hydrofluoric acid solution and dry it.

[0006] Furthermore, the removal solution in the first step is prepared by mixing 8-12 g KMnO4, 10-30 g NaOH and 12.5-13.5 mL 70%-99% NH3·H2O in 500 mL deionized water, stirring uniformly and then diluting to 1 L per 1 L; Furthermore, the pH of the removal solution is 12-14; Furthermore, in the first step, the soaking time is 30-70 minutes and the soaking temperature is 35-43°C; Furthermore, the reaction equations of the components in the removal solution and the elemental silver in the solder are as follows: 2KMnO4+2NaOH+4NH3·H2O+2Ag=K2MnO4+Na2MnO4+2Ag(NH3)2OH+4H2O.

[0007] A removal solution with a pH of 12-14 facilitates the reduction of the electrode potential of the silver surface by NH3·H2O, making the reaction easier to proceed, thereby improving the efficiency of silver removal from the solder. An immersion temperature of 35-43°C can promote the conversion of elemental silver in the removal solution provided by the present invention into soluble Ag+, while also preventing the decomposition of the active ingredients of the removal solution due to excessively high reaction temperatures.

[0008] Furthermore, the curing temperature of the thermosetting ink in the second step is 90-100° C., and the curing time is 2-4 minutes. The printing of the thermosetting ink can protect the copper surface. Furthermore, the thermosetting ink in the second step is prepared by the following steps: Weigh the raw materials by weight, and mix and stir evenly 30-40 parts of epoxy-terminated hyperbranched polyester resin, 15-20 parts of reactive diluent, 3-6 parts of calcium carbonate, 2-5 parts of aluminum hydroxide, 3-10 parts of pigment, 6-12 parts of acetone, 1.5-2.5 parts of curing agent and 0.1-0.3 parts of leveling agent; Furthermore, the active diluent is polypropylene glycol diglycidyl ether; Furthermore, the curing agent is one of triethylamine, ethylenediamine or diethylenetriamine; Furthermore, the leveling agent is BYK-333; Furthermore, the pigment is one of azo pigments, phthalocyanine pigments, lead chrome yellow, lithopone or carbon black.

[0009] Furthermore, in the third step, the concentration of the hydrofluoric acid solution is 10%-15%, the immersion time is 5-15 minutes, and the immersion temperature is 20-35°C.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The method for removing solder from a copper-clad ceramic substrate in steps of the present invention is different from the existing one-step etching method of solder and can effectively control the amount of etching of the copper layer by the solution during the solder removal process, thereby reducing the occurrence of point-like copper pits on the surface of the copper layer.

[0011] The step-by-step solder removal method employed by the present invention effectively controls the amount of copper erosion by the removal solution during the solder removal process, thereby preventing the formation of fine, dot-like copper pits on the copper surface. A pH of 12-14 in the removal solution facilitates the use of NH3·H2O in the solution to reduce the electrode potential of the silver surface, facilitating the reaction and improving the efficiency of silver removal from the solder. Furthermore, a solder immersion temperature of 35-43°C in the removal solution promotes the conversion of elemental silver into soluble Ag+ in the removal solution provided by the present invention, while also preventing decomposition of the active ingredients of the removal solution due to excessively high reaction temperatures. DETAILED DESCRIPTION

[0012] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0013] Example 1: The removal solution was prepared by the following steps: 8 g KMnO4, 10 g NaOH and 12.5 mL 70% NH3·H2O were mixed and stirred in 500 mL deionized water, and the volume was adjusted to 1 L, and the pH was adjusted to 12.

[0014] Thermosetting inks are prepared by the following steps: 30 parts of epoxy-terminated hyperbranched polyester resin, 15 parts of polypropylene glycol diglycidyl ether, 3 parts of calcium carbonate, 2 parts of aluminum hydroxide, 3 parts of azo pigment, 6 parts of acetone, 1.5 parts of triethylamine and 0.1 part of leveling agent BYK-333; The raw materials are weighed in parts by weight, and the epoxy-terminated hyperbranched polyester resin, polypropylene glycol diglycidyl ether, calcium carbonate, aluminum hydroxide, azo pigment, acetone, triethylamine and BYK-333 are mixed and stirred evenly to obtain the product.

[0015] Example 2: The removal solution was prepared by the following steps: The solution was prepared by mixing 10 g KMnO4, 20 g NaOH and 13 mL 80% NH3·H2O in 500 mL deionized water, stirring the mixture and then adjusting the volume to 1 L. The pH was adjusted to 13.

[0016] Thermosetting inks are prepared by the following steps: 35 parts of epoxy-terminated hyperbranched polyester resin, 17 parts of polypropylene glycol diglycidyl ether, 4.5 parts of calcium carbonate, 3 parts of aluminum hydroxide, 5 parts of phthalocyanine pigment, 8 parts of acetone, 2 parts of ethylenediamine and 0.2 parts of leveling agent BYK-333; The raw materials are weighed in parts by weight, and the epoxy-terminated hyperbranched polyester resin, polypropylene glycol diglycidyl ether, calcium carbonate, aluminum hydroxide, phthalocyanine pigment, acetone, triethylamine and BYK-333 are mixed and stirred evenly to obtain the product.

[0017] Example 3: The removal solution is prepared by the following steps: The solution was prepared by mixing 11 g KMnO4, 25 g NaOH and 13 mL 95% NH3·H2O in 500 mL deionized water, stirring the mixture and then adjusting the volume to 1 L. The pH was adjusted to 13.5.

[0018] Thermosetting inks are prepared by the following steps: 35 parts of epoxy-terminated hyperbranched polyester resin, 18 parts of polypropylene glycol diglycidyl ether, 5 parts of calcium carbonate, 4 parts of aluminum hydroxide, 7 parts of lead chrome yellow, 10 parts of acetone, 2 parts of diethylenetriamine and 0.3 parts of leveling agent BYK-333; The raw materials are weighed in parts by weight, and the epoxy-terminated hyperbranched polyester resin, polypropylene glycol diglycidyl ether, calcium carbonate, aluminum hydroxide, lead chrome yellow, acetone, diethylenetriamine and BYK-333 are mixed and stirred evenly to obtain the product.

[0019] Example 4: The removal solution is prepared by the following steps: The solution was prepared by mixing 12 g KMnO4, 30 g NaOH, and 13.5 mL 99% NH3·H2O in 500 mL deionized water, stirring the mixture until the volume was 1 L, and adjusting the pH to 14.

[0020] Thermosetting inks are prepared by the following steps: 40 parts of epoxy-terminated hyperbranched polyester resin, 20 parts of polypropylene glycol diglycidyl ether, 6 parts of calcium carbonate, 5 parts of aluminum hydroxide, 10 parts of lithopone, 12 parts of acetone, 2.5 parts of diethylenetriamine and 0.3 parts of leveling agent BYK-333; The raw materials are weighed in parts by weight, and the epoxy-terminated hyperbranched polyester resin, polypropylene glycol diglycidyl ether, calcium carbonate, aluminum hydroxide, lithopone, acetone, diethylenetriamine and BYK-333 are mixed and stirred evenly to obtain the product.

[0021] Example 5: A method for removing solder from a copper-clad ceramic substrate in steps, comprising the following steps: Step 1: placing the copper-clad ceramic substrate in a soaking tank containing the removal solution prepared in Example 1 and soaking for 30 minutes at a soaking temperature of 35° C. to obtain a pretreated substrate; Step 2: The pretreated substrate was washed and dried in deionized water, and a layer of the thermosetting ink prepared in Example 1 was evenly printed on the upper and lower surfaces of the dried pretreated substrate, followed by curing to obtain a secondary treated substrate; wherein the curing temperature was 90° C. and the curing time was 2 minutes; Step 3: Soak the secondary treated substrate in a 10% hydrofluoric acid solution for 5 minutes at a temperature of 20°C and then dry.

[0022] Example 6: A method for removing solder from a copper-clad ceramic substrate in steps, comprising the following steps: Step 1: placing the copper-clad ceramic substrate in a soaking tank containing the removal solution prepared in Example 2 for 40 minutes at a soaking temperature of 38° C. to obtain a pretreated substrate; Step 2: The pretreated substrate was washed and dried in deionized water, and a layer of the thermosetting ink prepared in Example 2 was evenly printed on the upper and lower surfaces of the dried pretreated substrate, followed by curing to obtain a secondary treated substrate; wherein the curing temperature was 95° C. and the curing time was 3 minutes; Step 3: Soak the secondary processed substrate in a 12% hydrofluoric acid solution for 8 minutes at a temperature of 25°C and then dry it.

[0023] Example 7: A method for removing solder from a copper-clad ceramic substrate in steps, comprising the following steps: Step 1: Place the copper-clad ceramic substrate in a soaking tank containing the removal solution prepared in Example 3 and soak for 50 minutes at a soaking temperature of 40° C. to obtain a pretreated substrate; Step 2: The pretreated substrate was washed and dried in deionized water, and a layer of the thermosetting ink prepared in Example 3 was evenly printed on the upper and lower surfaces of the dried pretreated substrate, followed by curing to obtain a secondary treated substrate; wherein the curing temperature was 95° C. and the curing time was 3 minutes; Step 3: Soak the secondary processed substrate in a 13% hydrofluoric acid solution for 10 minutes at a temperature of 30°C and then dry it.

[0024] Example 8: A method for removing solder from a copper-clad ceramic substrate in steps, comprising the following steps: Step 1: placing the copper-clad ceramic substrate in a soaking tank containing the removal solution prepared in Example 4 for 70 minutes at a soaking temperature of 43° C. to obtain a pretreated substrate; Step 2: The pretreated substrate was washed and dried in deionized water, and then a layer of the thermosetting ink prepared in Example 4 was evenly printed on the upper and lower surfaces of the dried pretreated substrate, and then cured to obtain a secondary treated substrate; wherein the curing temperature was 100° C. and the curing time was 4 minutes; Step 3: Soak the secondary processed substrate in a 15% hydrofluoric acid solution for 15 minutes at a temperature of 35°C and then dry it.

[0025] Comparative Example 1: This comparative example uses a traditional one-step etching method to remove the brazing material of the copper-clad ceramic substrate.

[0026] The copper pits on the surface of the copper-clad ceramic substrate after etching in Examples 5-8 and Comparative Example 1 were observed, and the test results are shown in Table 1: Table 1: Performance test results As can be seen from Table 1, the step-by-step removal of the brazing material of the copper-clad ceramic substrate by the present invention can effectively control the amount of corrosion of the copper layer by the solution and reduce the occurrence of point-like copper pits on the surface of the copper layer.

[0027] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for removing solder from a copper-clad ceramic substrate in steps, characterized in that: The following steps are involved: Step 1: placing the copper-clad ceramic substrate in an immersion tank to obtain a pre-treated substrate; the immersion tank contains a removal solution, which is a mixed solution of KMnO4, NaOH, NH3·H2O and deionized water; Step 2: The pre-treated substrate is placed in deionized water for cleaning and drying, and then a layer of thermosetting ink is evenly printed on the upper and lower surfaces of the dried pre-treated substrate and cured to obtain a secondary treated substrate; Step 3: Soak the secondary processed substrate in a hydrofluoric acid solution and dry it.

2. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 1, wherein: Each 1 L of the removal solution contains 8-12 g of KMnO4, 10-30 g of NaOH and 12.5-13.5 mL of 70%-99% NH3·H2O, and the pH value of the removal solution is 12-14.

3. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 1, wherein: The soaking time in the first step is 30-70 minutes, and the soaking temperature is 35-43°C.

4. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 1, wherein: The thermosetting ink in the second step is prepared by the following steps: The raw materials are weighed in parts by weight, and 30-40 parts of epoxy-terminated hyperbranched polyester resin, 15-20 parts of reactive diluent, 3-6 parts of calcium carbonate, 2-5 parts of aluminum hydroxide, 3-10 parts of pigment, 6-12 parts of acetone, 1.5-2.5 parts of curing agent and 0.1-0.3 parts of leveling agent are mixed and stirred evenly to obtain the product.

5. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 1, wherein: In the second step, the curing temperature of the thermosetting ink is 90-100° C., and the curing time is 2-4 minutes.

6. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 4, wherein: The active diluent is polypropylene glycol diglycidyl ether.

7. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 4, wherein: The curing agent is one of triethylamine, ethylenediamine or diethylenetriamine.

8. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 4, characterized in that: The leveling agent is BYK-333.

9. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 4, wherein: The pigment is one of azo pigments, phthalocyanine pigments, lead chrome yellow, lithopone or carbon black.

10. The method for removing solder from a copper-clad ceramic substrate in steps according to claim 1, characterized in that: In the third step, the concentration of the hydrofluoric acid solution is 10%-15%, the soaking time is 5-15 minutes, and the soaking temperature is 20-35°C.

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