阅读说明：本技术 一种回收再利用导电浆料的方法 (Method for recycling conductive paste ) 是由 杨诤溢 于 2021-09-29 设计创作，主要内容包括：本发明提出了一种回收再利用导电浆料的方法,涉及化工生产技术领域。该回收再利用导电浆料的方法包括如下步骤：将导电浆料初次加热,得到热料,向热料中加入酸液酸化,得到混合物,将混合物离心后过滤,得到沉淀和上清液,将上清液二次加热至有晶体析出并收集晶体,将晶体三次加热后与碳粉反应,得到第一粉末,向沉淀加入碱液碱化后四次加热,得到第二粉末,即完成导电浆料的回收；该方法通过使环氧树脂的粘度降低,从而使导电浆料中的金属元素分离出来,以便于后续分离操作,而后续通过酸液对金属离子进行分离和纯化,以使金属离子从环氧树脂中分离,后续通过碱液等加热处理以使金属离子反应为金属单质,从而实现导电浆料的回收以及再利用。(The invention provides a method for recycling conductive paste, and relates to the technical field of chemical production. The method for recycling the conductive paste comprises the following steps: heating the conductive slurry for the first time to obtain a hot material, adding acid liquor into the hot material for acidification to obtain a mixture, centrifuging the mixture, filtering to obtain a precipitate and a supernatant, heating the supernatant for the second time until crystals are separated out, collecting the crystals, heating the crystals for the third time, reacting with carbon powder to obtain first powder, adding alkali liquor into the precipitate for alkalization, and heating for the fourth time to obtain second powder, namely completing the recovery of the conductive slurry; according to the method, the viscosity of the epoxy resin is reduced, so that metal elements in the conductive slurry are separated, the subsequent separation operation is facilitated, metal ions are separated and purified through acid liquor, the metal ions are separated from the epoxy resin, the metal ions are reacted into metal simple substances through heating treatment of alkali liquor and the like, and the recovery and the reutilization of the conductive slurry are realized.)

1. A method for recycling and reusing conductive paste is characterized by comprising the following steps of heating the conductive paste for the first time to obtain a hot material, adding acid liquor into the hot material for acidification to obtain a mixture, centrifuging the mixture, filtering to obtain a precipitate and a supernatant, heating the supernatant for the second time until crystals are separated out, collecting the crystals, heating the crystals for the third time, reacting the crystals with carbon powder to obtain first powder, adding alkali liquor into the precipitate for alkalization, and heating for the fourth time to obtain second powder, so that the recycling of the conductive paste is completed.

2. The method for recycling conductive paste according to claim 1, wherein the acid solution is concentrated sulfuric acid, and the mass concentration of the concentrated sulfuric acid is 80-98%.

3. The method for recycling conductive paste according to claim 1, wherein the acidification is stopped after adding the acid solution to acidify to a pH of 3 to 5.

4. The method for recycling conductive paste according to claim 1, wherein the alkali solution is ammonia or sodium hydroxide solution.

5. The method for recycling conductive paste according to claim 1, wherein the alkalization is stopped after adding the alkali solution to alkalize to pH 7-9.

6. The method for recycling conductive paste as claimed in claim 1, wherein the temperature of the primary heating is 150 ℃ to 200 ℃, and the time of the primary heating is 3-8 h.

7. The method as claimed in claim 1, wherein the temperature of the second heating is 200 ℃ to 500 ℃, and the second heating is stopped after no crystal is precipitated.

8. The method as claimed in claim 1, wherein the temperature of the third heating is 650-700 ℃, and the time of the third heating is 4-10 h.

9. The method as claimed in claim 1, wherein the temperature of the fourth heating is 300-400 ℃, and the time of the fourth heating is 3-9 h.

10. The method as claimed in claim 1, wherein the rotation speed of the centrifugation is 1500-8000 rpm.

Technical Field

The invention relates to the technical field of chemical production, in particular to a method for recycling conductive paste.

Background

The conductive paste is also called conductive adhesive, and is a mixture of noble metal powder, base metal powder, glass powder and synthetic resin. Wherein the solvent is added to make the material or graphite-like material. The metal powder has a particle size of about 1 to 2 μm, and a slurry of ultrafine powder having a particle size of several tens of nanometers is being developed. Commonly used pastes comprise Ag (30-85% of Ag, the balance being epoxy resin and glass powder), Au (60-85% of Au, the balance being epoxy resin and glass powder), Au-Pd (50-70% of Au, 10-20% of Pd, the balance being epoxy resin and glass powder), Cu (70-80% of Cu, the balance being epoxy resin and glass powder), Ni (80-90% of Ni, the balance being epoxy resin and glass powder) and the like. These pastes are screen printed or otherwise applied to the desired areas of the substrate and then fired to form the conductor at temperatures of 400-1000 c. The method is mainly used for wiring of thick film integrated circuits, electrodes of ceramic capacitors and the like, and leads of hybrid integrated circuits. Since the conductive paste contains a large amount of precious metals, heavy metals, and the like, in order to protect the environment and save raw materials, the metal substances in the conductive paste need to be recovered before the used conductive paste is discarded.

Therefore, it is urgently needed to provide a method capable of efficiently recovering metal substances in conductive paste.

Disclosure of Invention

The invention aims to provide a method for recycling conductive paste, which can effectively recycle heavy metal ions such as silver ions, copper ions and the like in the conductive paste, thereby not only increasing the utilization rate of raw materials, but also avoiding the pollution of the heavy metal ions to the environment.

The technical problem to be solved by the invention is realized by adopting the following technical scheme.

The embodiment of the application provides a method for recycling conductive paste, which comprises the following steps that the conductive paste comprises silver and copper, the conductive paste is heated for the first time to obtain a hot material, acid liquor is added into the hot material for acidification to obtain a mixture, the mixture is centrifuged and filtered to obtain a precipitate and a supernatant, the supernatant is heated for the second time until crystals are separated out and the crystals are collected, the crystals are heated for the third time and then react with carbon powder to obtain first powder, and the precipitate is heated for the fourth time after being added with alkali liquor for alkalization to obtain second powder, so that the recycling of the conductive paste is completed. Since the conductive paste is rich in metal elements such as silver, copper and the like, which are mainly stored in the epoxy resin of the conductive paste, the viscosity of the epoxy resin is reduced by primary heating, so that the epoxy resin reduces the adsorption of metal ions and other substances in the epoxy resin, and the metal ions are separated out of the epoxy resin for subsequent reaction; then adding acid liquor for acidification so as to acidify metal ions and generate metal salt, so that the metal ions are completely separated from the epoxy resin, the environment of the whole conductive paste is changed, and all substances in the conductive paste are in an acid environment, so that the subsequent reaction is facilitated; separating the metal salt in the conductive paste by centrifugation to settle the metal salt suspended in the conductive paste to the bottom of the conductive paste, thereby facilitating the separation, wherein part of the metal salt is precipitated after centrifugation and is therefore settled to the bottom of the conductive paste, and part of the metal salt can be dissolved in the acid solution and is therefore present in the supernatant; the supernatant is heated for the second time to separate out the metal salt crystals in the supernatant so as to realize the purpose of purifying the metal salt crystals, and then the metal salt crystals are decomposed into metal oxides by heating for the third time so as to facilitate the subsequent reaction to prepare pure metal simple substances so as to realize the complete recovery and reutilization of metal elements; wherein, carbon powder is added as a reducing agent in the process of three times of heating to reduce metal oxides into metal simple substances, thereby realizing the recovery and the reutilization of metal substances; the method comprises the following steps of adding alkali liquor to enable metal salt to react with the alkali liquor so as to generate metal hydroxide, wherein the noble metal hydroxide is extremely unstable in property, so that the noble metal hydroxide is easy to decompose under heating conditions so as to generate water and metal oxide, the metal oxide can decompose under high temperature of four times of heating so as to generate metal simple substance, and second powder is obtained, wherein the second powder and the first powder are both metal simple substance, the first powder is mainly copper and other noble metals, and the second powder is mainly silver and other noble metals, so that the purposes of protecting environment and saving raw materials are achieved, and the sustainable development principle is met.

Compared with the prior art, the embodiment of the invention has at least the following advantages or beneficial effects:

the embodiment of the invention provides a method for recycling conductive paste, which is characterized in that the viscosity of epoxy resin is reduced by heating, so that metal elements in the conductive paste can be separated, and subsequent separation operation is facilitated.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to specific examples.

The embodiment of the invention provides a method for recycling conductive paste, which comprises the following steps of heating the conductive paste for the first time to obtain a hot material, adding acid liquor into the hot material for acidification to obtain a mixture, centrifuging the mixture, filtering to obtain a precipitate and a supernatant, heating the supernatant for the second time until crystals are separated out, collecting the crystals, heating the crystals for the third time, reacting the crystals with carbon powder to obtain first powder, adding alkali liquor into the precipitate for alkalization, and heating for the fourth time to obtain second powder, so that the recycling of the conductive paste is completed. Since the conductive paste is rich in metal elements such as silver, copper and the like, which are mainly stored in the epoxy resin of the conductive paste, the viscosity of the epoxy resin is reduced by primary heating, so that the epoxy resin reduces the adsorption of metal ions and other substances in the epoxy resin, and the metal ions are separated out of the epoxy resin for subsequent reaction; then adding acid liquor for acidification so as to acidify metal ions and generate metal salt, so that the metal ions are completely separated from the epoxy resin, the environment of the whole conductive paste is changed, and all substances in the conductive paste are in an acid environment, so that the subsequent reaction is facilitated; separating the metal salt in the conductive paste by centrifugation to settle the metal salt suspended in the conductive paste to the bottom of the conductive paste, thereby facilitating the separation, wherein part of the metal salt is precipitated after centrifugation and is therefore settled to the bottom of the conductive paste, and part of the metal salt can be dissolved in the acid solution and is therefore present in the supernatant; the supernatant is heated for the second time to separate out the metal salt crystals in the supernatant so as to realize the purpose of purifying the metal salt crystals, and then the metal salt crystals are decomposed into metal oxides by heating for the third time so as to facilitate the subsequent reaction to prepare pure metal simple substances so as to realize the complete recovery and reutilization of metal elements; wherein, carbon powder is added as a reducing agent in the process of three times of heating to reduce metal oxides into metal simple substances, thereby realizing the recovery and the reutilization of metal substances; the method comprises the following steps of adding alkali liquor to enable metal salt to react with the alkali liquor so as to generate metal hydroxide, wherein the noble metal hydroxide is extremely unstable in property, so that the noble metal hydroxide is easy to decompose under heating conditions so as to generate water and metal oxide, the metal oxide can decompose under high temperature of four times of heating so as to generate metal simple substance, and second powder is obtained, wherein the second powder and the first powder are both metal simple substance, the first powder is mainly copper and other noble metals, and the second powder is mainly silver and other noble metals, so that the purposes of protecting environment and saving raw materials are achieved, and the sustainable development principle is met.

In some embodiments of the present invention, the acid solution is concentrated sulfuric acid, and the mass concentration of the concentrated sulfuric acid is 80-98%. Concentrated sulfuric acid is sulfuric acid aqueous solution with mass fraction of more than or equal to 70 percent, commonly called bad water. Concentrated sulfuric acid mainly reacts with noble metals and the like, common dilute sulfuric acid cannot sufficiently react with the noble metals due to the fact that the oxidizing property of the common dilute sulfuric acid is not strong enough than that of the concentrated sulfuric acid, and then the noble metals cannot be sufficiently separated from the conductive slurry, and therefore waste of raw materials is caused.

In some embodiments of the invention, acidification is stopped after adding the acid solution to acidify to a pH of 3 to 5. The pH interval can ensure that the metal salt stably exists in the conductive paste, and the metal salt is prevented from reacting with other impurities in the conductive paste, or reacting with hydroxyl ions due to overhigh pH, or generating other reactions due to instability of the conductive paste due to overlow pH, so that other weak acids are generated.

In some embodiments of the present invention, the alkali solution is ammonia or sodium hydroxide solution. The metal salt is precipitated through ammonia water or sodium hydroxide solution to react to form unstable metal base, so that the metal base is decomposed to form metal oxide, and the subsequent preparation of the metal simple substance is facilitated.

In some embodiments of the invention, the alkalization is stopped after adding the above lye to a pH of 7-9. The pH range can enable the metal alkali to tend to be stable in the alkali liquor, and the phenomenon that the metal alkali is unstable and further reacts to generate weak alkali due to overhigh pH is avoided, so that the content of the metal alkali is reduced; and can also avoid the situation that the metal alkali is extremely unstable and is hydrolyzed into free metal ions again due to the over low pH value, thereby further reducing the content of the metal simple substance prepared subsequently.

In some embodiments of the present invention, the temperature of the primary heating is 150-. The physical property of the epoxy resin is changed by primary heating, so that the surface tension of the epoxy resin is increased, the viscosity of the epoxy resin is reduced, metal ions are better separated from the epoxy resin, and the subsequent reaction is facilitated.

In some embodiments of the present invention, the temperature of the second heating is 200-. The solubility of the conductive paste is reduced through secondary heating, so that the metal salt is separated out from the conductive paste, and further the subsequent preparation of the metal salt into a metal simple substance is facilitated, and the recovery and the reutilization of the conductive paste are facilitated.

In some embodiments of the present invention, the temperature of the three times of heating is 650-. The precipitated metal salt crystals are decomposed into metal oxides at high temperature through three times of heating, so that the subsequent reduction reaction is facilitated, the purity of the metal simple substance reduced from the oxides is higher, other impurities are not easily carried, and the metal simple substance separated and purified is conveniently subjected to subsequent utilization.

In some embodiments of the present invention, the temperature of the four times of heating is 300-. The unstable metal base is decomposed by four times of heating, so that metal oxide is generated, and the metal oxide can be reduced into a simple metal substance by a reduction reaction when the generation of the metal oxide is completed.

In some embodiments of the present invention, the rotation speed of the centrifugation is 1500-. The rotating speed interval can effectively settle the metal alkali precipitate and separate the precipitate from the supernatant, thereby facilitating the subsequent preparation of metal alkali into metal simple substances.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

The embodiment provides a method for recycling conductive paste, which comprises the following steps of heating the conductive paste for the first time at 150 ℃ for 3h to obtain a hot material, adding 80% concentrated sulfuric acid into the hot material to acidify the hot material to pH 3 to obtain a mixture, centrifuging the mixture at 1500rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant at 200 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals for the third time at 650 ℃ for 4h, reacting with carbon powder to obtain first powder, adding ammonia water into the precipitate to alkalify the crystals to pH 7, and heating for the fourth time at 300 ℃ for 3h to obtain second powder, so that the recycling of the conductive paste is completed.

Example 2

The embodiment provides a method for recycling conductive paste, which comprises the following steps of heating the conductive paste for 8 hours at 200 ℃ for the first time to obtain a hot material, adding 98% concentrated sulfuric acid into the hot material to acidify the hot material to pH 5 to obtain a mixture, centrifuging the mixture at 8000rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant for the second time at 500 ℃ until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals for the third time at 700 ℃ for 10 hours, reacting with carbon powder to obtain first powder, adding a sodium hydroxide solution into the precipitate to alkalify the crystals to pH 9, and heating for the fourth time at 400 ℃ for 9 hours to obtain second powder, namely completing the recycling of the conductive paste.

Example 3

The embodiment provides a method for recycling and reusing a conductive paste, which comprises the following steps of heating the conductive paste for the first time at 175 ℃ for 5 hours to obtain a hot material, adding 89% concentrated sulfuric acid into the hot material to acidify the hot material to pH 4 to obtain a mixture, centrifuging the mixture at 4500rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant for the second time at 350 ℃ until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals for the third time at 675 ℃ for 7 hours, reacting with carbon powder to obtain first powder, adding ammonia water into the precipitate to alkalify the crystals to pH 8, and heating for the fourth time at 350 ℃ for 6 hours to obtain second powder, so that the recycling of the conductive paste is completed.

Example 4

The embodiment provides a method for recycling and reusing conductive paste, which comprises the following steps of heating the conductive paste for the first time at 170 ℃ for 4.5 hours to obtain a hot material, adding 88% concentrated sulfuric acid into the hot material to acidify to pH 3.5 to obtain a mixture, centrifuging the mixture at 4400rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant at 360 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals at 680 ℃ for the third time for 6 hours, reacting with carbon powder to obtain first powder, adding ammonia water into the precipitate to alkalify to pH 7.5, and heating at 360 ℃ for the fourth time for 6.5 hours to obtain second powder, so that the recycling of the conductive paste is completed.

Example 5

The embodiment provides a method for recycling and reusing conductive paste, which comprises the following steps of heating the conductive paste for the first time at 181 ℃ for 5.5 hours to obtain a hot material, adding 89% concentrated sulfuric acid into the hot material to acidify the hot material to pH 4.5 to obtain a mixture, centrifuging the mixture at 4700rpm, filtering the mixture to obtain a precipitate and a supernatant, heating the supernatant at 360 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals for three times at 670 ℃ for 8 hours to react with carbon powder to obtain first powder, adding ammonia water into the precipitate to alkalify the crystals to pH 8.5, and heating the crystals for four times at 340 ℃ for 5.5 hours to obtain second powder, so that the recycling of the conductive paste is completed.

Example 6

The embodiment provides a method for recycling and reusing conductive paste, which comprises the following steps of heating the conductive paste for the first time at 191 ℃ for 5.2 hours to obtain a hot material, adding 85% concentrated sulfuric acid into the hot material to acidify to the pH value of 3.8 to obtain a mixture, centrifuging the mixture at 4800rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant at 346 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals for the third time at 677 ℃ for 7.2 hours, reacting with carbon powder to obtain first powder, adding ammonia water into the precipitate to alkalize to the pH value of 8.1, and heating for the fourth time at 342 ℃ for 5.4 hours to obtain second powder, so that the recycling of the conductive paste is completed.

Example 7

The embodiment provides a method for recycling and reusing conductive paste, which comprises the following steps of heating the conductive paste for the first time at 184 ℃ for 3.8h to obtain a hot material, adding 82% concentrated sulfuric acid into the hot material to acidify to pH 4.4 to obtain a mixture, centrifuging the mixture at 4700rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant at 356 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals at 641 ℃ for the third time for 6.4h, reacting with carbon powder to obtain a first powder, adding ammonia water into the precipitate to alkalize to pH 7.2, and heating at 309 ℃ for the fourth time for 4.8h to obtain a second powder, so that the recycling of the conductive paste is completed.

Example 8

The embodiment provides a method for recycling and reusing conductive paste, which comprises the following steps of heating the conductive paste for the first time at 177 ℃ for 5.2 hours to obtain a hot material, adding 89% concentrated sulfuric acid into the hot material to acidify the hot material to the pH value of 3.9 to obtain a mixture, centrifuging the mixture at 4222rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant at 333 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals at 683 ℃ for the third time for 7.2 hours, reacting with carbon powder to obtain first powder, adding ammonia water into the precipitate to alkalize the precipitates to the pH value of 7.2, and heating the precipitates at 350 ℃ for the fourth time for 4.4 hours to obtain second powder, so that the recycling of the conductive paste is completed.

Example 9

The embodiment provides a method for recycling and reusing conductive paste, which comprises the following steps of heating the conductive paste for the first time at 197 ℃ for 3.9h to obtain a hot material, adding 96% concentrated sulfuric acid into the hot material to acidify to pH 4.2 to obtain a mixture, centrifuging the mixture at 4555rpm, filtering to obtain a precipitate and a supernatant, heating the supernatant at 349 ℃ for the second time until crystals are separated out and no more crystals are separated out, collecting the crystals, heating the crystals for three times at 694 ℃ for 7.1h, reacting with carbon powder to obtain a first powder, adding ammonia water into the precipitate to alkalize to pH 8.3, and heating for four times at 397 ℃ for 5.7h to obtain a second powder, so that the recycling of the conductive paste is completed.

Test example 1

The method for recycling conductive paste provided in examples 1 to 9 was used to recycle 50g of conductive paste containing silver and copper, and during the recycling process, the crystals, the first powder, the precipitate, and the second powder were weighed (g) in sequence, and the first recovery rate and the second recovery rate were calculated according to the data obtained by weighing, and the calculation of the crystal recovery rate was performed according to the following formula: the crystal mass/conductive slurry mass x 100%, the precipitation recovery was calculated as follows: the precipitation mass/the conductive paste mass is multiplied by 100%; the first powder recovery was calculated as follows: first powder mass/crystal mass x 100%; the second powder recovery was calculated as follows: the second powder mass/precipitate mass x 100%, the results are shown in table 1.

TABLE 1 silver and copper recovery test Table

As shown in the results in table 1, the method for recycling conductive paste provided in this embodiment can effectively recycle precious metals such as copper and silver in conductive paste, thereby realizing recycling of raw materials and meeting the principle of sustainable development.

Test example 2

The residual solution of the recovered conductive paste in test example 1 and the common conductive paste were used as a control group, and the heavy metal ions (ng/ml) were detected according to the national standard GB/T9735-.

TABLE 2 heavy metal content detection table

According to the results shown in table 2, the amount of the heavy metal ions remaining in the recycled conductive paste in test example 1 is significantly lower than that in the comparative example, so that it can be seen that the method for recycling conductive paste provided by the embodiment of the present invention can remove the heavy metal ions therein, so that the conductive paste has reduced harm to the environment, and further conforms to the principle of environmental development.

In summary, embodiments of the present invention provide a method for recycling conductive paste, in which the viscosity of epoxy resin is reduced by heating, so that metal elements in the conductive paste can be separated, and thus subsequent separation operations can be performed, and then metal ions are separated and purified by an acid solution, so that metal ions, metal impurities, and the like in the conductive paste generate metal salts, so that the metal ions can be separated from the epoxy resin, and then the metal ions react and are converted into metal simple substances by alkali solution and multiple heating treatments, so as to achieve recycling and reusing of the conductive paste.

The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.