A protective wax for industrial electronic circuit boards and its preparation method and application

Abstract

The invention discloses a protective wax for industrial electronic circuit boards, a preparation method and an application thereof. The protective wax comprises microcrystalline wax, a low-temperature toughening agent, cerium dodecyl stearate, 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt and ethylene propylene diene rubber. The protective wax is melted at 95-105°C and directly applied to the PCB slot of the electronic circuit board. After natural cooling and solidification, the protective wax has the characteristics of not cracking at a low temperature of 60°C, not flowing at 90°C, and being resistant to corrosion by hydrogen sulfide and sulfur dioxide.

Description

Technical Field

[0001] The invention relates to the field of protective wax, and in particular to a protective wax for industrial electronic circuit boards and a preparation method and application thereof. Background Art

[0002] Industrial electronic circuit boards (PCBs) are widely used. The use environment of some instruments and meters is relatively harsh compared to that of civilian products, especially in some cold northern regions, coastal high-salinity regions, and high-temperature workshops. Strict requirements are placed on the waterproof and anti-corrosion of electronic circuit boards (PCBs). Traditional civilian electronic circuit boards (PCBs) can be protected in mild environments with coating products such as three-proof paints, but for industrial electronic circuit boards (PCBs), three-proof paints are insufficient: easy to leak; poor sealing; and inability to achieve long-term waterproof and anti-corrosion.

[0003] In the prior art, the problem with using microcrystalline wax to prepare protective wax materials is that if only microcrystalline wax materials are used, high melting point wax is prone to cracking in low temperature environments, and low melting point wax is prone to leakage in high temperature environments, so it is impossible to meet the use requirements of industrial electronic circuit boards. Summary of the invention

[0004] In order to solve the above-mentioned technical problems, the present invention provides a protective wax for industrial electronic circuit boards, which can be used in high and low temperature environments and has an anti-corrosion effect on various metals.

[0005] The technical scheme adopted by the present invention is as follows: a protective wax for industrial electronic circuit boards, comprising microcrystalline wax, a low-temperature toughening agent, cerium dodecyl stearate, 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt and ethylene propylene diene rubber.

[0006] Furthermore, the above-mentioned protective wax for industrial electronic circuit boards includes, by weight, 60-75 parts of microcrystalline wax, 10-15 parts of low-temperature toughening agent, 6-8 parts of cerium dodecyl stearate, 5-7 parts of 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt and 1-3 parts of ethylene propylene diene rubber.

[0007] Furthermore, in the above-mentioned protective wax for industrial electronic circuit boards, the microcrystalline wax is No. 80 microcrystalline wax.

[0008] Furthermore, in the above-mentioned protective wax for industrial electronic circuit boards, the low-temperature toughening agent is diisooctyl sebacate and / or dioctyl phthalate.

[0009] Furthermore, the above-mentioned protective wax for industrial electronic circuit boards, the cerium dodecyl stearate, has a preparation method comprising the following steps: taking an appropriate amount of dodecyl stearic acid and adding it to deionized water, heating it to 50°C, stirring it evenly, and then dripping a sodium hydroxide aqueous solution. After the dripping is completed, slowly heating the system to 90°C, and continuing to stir for 2 hours to obtain a sodium dodecyl stearate salt water dispersion; then adding an appropriate amount of cerium nitrate, continuing to stir at 90°C for 6 hours, cooling to 5-10°C, standing, filtering, washing the resulting precipitate with water until it is neutral, and vacuum drying to obtain cerium dodecyl stearate.

[0010] Furthermore, the above-mentioned protective wax for industrial electronic circuit boards has a mass ratio of dodecyl hydroxystearic acid: deionized water: sodium hydroxide aqueous solution: cerium nitrate = 10:10:5-7:14-17.

[0011] Furthermore, the above-mentioned protective wax for industrial electronic circuit boards, the 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt, has a preparation method comprising the following steps: adding a small amount of 40-50°C deionized water to hydrogenated tallow amine, and dispersing at 2000 rpm for 10-20 min to obtain a hydrogenated tallow amine aqueous dispersion; then slowly adding concentrated hydrochloric acid to obtain a hydrogenated tallow amine hydrochloride dispersion; adding an appropriate amount of ethanol and 2,5-dimercapto-1,3,4-thiadiazole to an aqueous sodium hydroxide solution to obtain a mixed solution; adding the hydrogenated tallow amine hydrochloride dispersion to the obtained mixed solution, stirring at 80°C for 4h, cooling to room temperature, filtering, and washing the obtained precipitate with water and ethanol in turn, and drying to obtain 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt.

[0012] Furthermore, the above-mentioned protective wax for industrial electronic circuit boards has a mass ratio of hydrogenated tallow amine: deionized water: concentrated hydrochloric acid: sodium hydroxide aqueous solution: ethanol: 2,5-dimercapto-1,3,4-thiadiazole = 10:10:3-5:10:2:4-6.

[0013] A method for preparing protective wax for industrial electronic circuit boards comprises the following steps: cutting EPDM into small pieces, soaking the pieces in a low-temperature toughening agent for 24 hours, heating the pieces to 70°C and stirring the pieces for 3 hours; adding 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt and stirring the pieces for 30 minutes; adding cerium dodecyl stearate and stirring the pieces for 30 minutes; heating the pieces to 100°C and adding microcrystalline wax and stirring the pieces for 1 hour to obtain an oily liquid, cooling the pieces and granulating the pieces to obtain the protective wax for industrial electronic circuit boards.

[0014] The invention discloses an application of the protective wax in industrial electronic circuit boards.

[0015] The beneficial effects of the present invention are:

[0016] 1. The protective wax provided by the present invention adopts the rare earth metal salt cerium dodecyl hydroxystearate, which solves the corrosion resistance and high temperature resistance problems of various metals on electronic circuit boards in industrial environments. Metal salts of dodecyl hydroxystearate can improve the high temperature resistance of lubricating greases, but their anti-corrosion ability is limited. For example, calcium salts and lithium salts of dodecyl hydroxystearic acid cannot form a stable passivation film on the metal surface, especially in the protection of non-ferrous metals. The present invention adopts cerium salts of dodecyl hydroxy fatty acids containing rare earth metals, which effectively improves the dropping point of microcrystalline wax. At the same time, the cerium salts of dodecyl hydroxystearate used can form a good passivation film on the metal surface, forming good passivation and protection for various metals on electronic circuit boards.

[0017] 2. The protective wax provided by the present invention adopts 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt, which solves the corrosion protection problem of various metals on electronic circuit boards in industrial environments. 2,5-dimercapto-1,3,4-thiadiazole is a good copper corrosion inhibitor and can effectively adsorb active sulfur, but its structure is not easy to disperse in microcrystalline wax, and the use of 2,5-dimercapto-1,3,4-thiadiazole alone is prone to precipitation. The present invention introduces fatty amines into its structure, increases its stability in microcrystalline wax, and uses the fatty amine salt of 2,5-dimercapto-1,3,4-thiadiazole to enhance protection, avoid active sulfur corrosion in industrial environments, and solve the dissolution and dispersion problem of 2,5-dimercapto-1,3,4-thiadiazole in microcrystalline wax.

[0018] 3. In wax products, when the temperature drops to a certain point, the wax begins to crystallize. The natural crystal state is mostly needle-shaped or plate-shaped. The crystals gather inward, causing the internal stress to increase. When the crystallization tendency reaches a certain degree, cracks begin to appear inside, and the anti-corrosion barrier film fails. The low-temperature toughening agent used in the present invention has an extremely low freezing point, can work at a lower temperature, can take into account the dissolution of hydrocarbons and fat structures, and is easier to penetrate into the wax structure, improving the crystal structure of the wax to a cubic structure, thereby alleviating the problem of crystal cracking of the wax and achieving low-temperature protection on the surface of the electronic circuit board.

[0019] 4. In terms of high temperature resistance, the melting point of microcrystalline wax material is low, and generally it will form a fluid state with low viscosity below 90°C, which will cause leakage of wax on the surface of industrial electronic circuit boards, affecting their use. The present invention improves the viscosity of microcrystalline wax at high temperature by using cerium salt of dodecyl hydroxystearate, and effectively increases its dropping point. EPDM can also hinder the fluidity of the alkane molecular structure in the wax at high temperature, and at the same time, effectively improve the low-temperature toughness of the wax at low temperature, avoiding the wax in the container due to volume changes under different temperature states, and the loss of adhesion at the connection position with the container to form a gap.

[0020] 5. For the problem of using protective wax for electronic circuit boards in high and low temperature environments, the present invention uses EPDM and cerium salt of dodecahydroxy fatty acid to improve the high temperature performance of protective wax. The low temperature toughening agent can improve the crystal structure of wax in low temperature state, avoid or alleviate the generation of wax crystal structure such as needle-shaped structure that increases internal stress, and solve the problem of low temperature cracking. It avoids the problem of low melting point microcrystalline wax flowing at high temperature and high melting point microcrystalline wax cracking at low temperature.

[0021] 6. The low-temperature toughening agent used in the present invention, as a good fat structure dissolving solvent, can effectively help the fatty amine salt of dodecahydroxy fatty acid cerium salt and 2,5-dimercapto-1,3,4-thiadiazole to directly act on the metal surface and play a penetration role.

[0022] 7. The protective wax provided by the present invention is quantitatively hot-melted into liquid according to the volume of the industrial electronic circuit board PCB module slot when used. After cooling and molding, a 20-30 mm wax seal layer is formed. It can be used for a long time under conditions of -60°C to 90°C, and effectively protects non-ferrous metals from corrosion.

[0023] 8. The protective wax provided by the present invention is mainly used for electronic circuit boards (PCBs) in industrial instruments, meters, and equipment, and has the effects of high and low temperature resistance, water resistance, acid and alkali resistance, anti-fouling, and anti-corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a mechanism diagram of protective wax for industrial electronic circuit boards. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the embodiments.

[0026] Example 1

[0027] (I) A protective wax for industrial electronic circuit boards, the preparation method is as follows:

[0028] 1. Preparation of cerium dodecyl stearate:

[0029] 100g of dodecyl hydroxystearic acid was added to 100g of deionized water, heated to 50°C, stirred evenly, and then 66g of a 20% sodium hydroxide aqueous solution was added dropwise. After the addition was complete, the system was slowly heated to 90°C and stirred for 2h to obtain a sodium dodecyl hydroxystearate salt water dispersion. Then 145g of cerium nitrate was added, and after stirring at 90°C for 6h, the temperature was lowered to 5-10°C, allowed to stand for 24h, filtered, and the precipitate was washed with water until neutral, and vacuum dried to obtain cerium dodecyl hydroxystearate.

[0030] 2. Preparation of 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt:

[0031] Add 100g of hydrogenated tallow amine to 100g of deionized water (40-50℃), disperse at 2000 rpm for 10-20min to obtain a hydrogenated tallow amine aqueous dispersion. Then slowly add 36g of concentrated hydrochloric acid, control the reaction temperature to 40-50℃, and obtain a hydrogenated tallow amine hydrochloride dispersion. Take 100g of a 1% sodium hydroxide aqueous solution, add 20g of ethanol and 55.5g of 2,5-dimercapto-1,3,4-thiadiazole to prepare a yellow transparent solution. Add the hydrogenated tallow amine hydrochloride dispersion to the obtained yellow transparent solution, stir at 80℃ for 4h, cool to room temperature, filter, wash the obtained precipitate with water and ethanol in turn, and dry to obtain 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt.

[0032] 3. Preparation of protective wax:

[0033] 2g of EPDM rubber (Jilin Chemical J-0010 EPDM rubber) was cut into small pieces, soaked in 15g of diisooctyl sebacate for 24h, heated to 70°C and stirred for 3h, added with 5g of 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt, stirred for 30min, added with 8g of cerium dodecyl stearate, stirred for 30min, heated to 100°C, added with 70g of microcrystalline wax (No. 80 microcrystalline wax, trade name Sasol wax 3971), stirred and dissolved for 1h to obtain a slightly yellow transparent oily liquid, cooled and granulated to obtain a protective wax for industrial electronic circuit boards.

[0034] (II) Comparative Example 1

[0035] The preparation process of this comparative example is the same as (I), except that 8 g of cerium dodecyl hydroxystearate is replaced by a mixture of calcium dodecyl hydroxystearate and dodecyl hydroxystearic acid in a weight ratio of 1:1.

[0036] (III) Comparative Example 2

[0037] The preparation process of this comparative example is the same as that of (I), except that 5 g of 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt is replaced by 5 g of 2,5-dimercapto-1,3,4-thiadiazole.

[0038] (IV) Comparative Example 3

[0039] The protective wax is only a single microcrystalline wax (No. 80 microcrystalline wax, trade name Sasol wax 3971).

[0040] (V) Technical indicators

[0041] The protective waxes prepared in the present invention and comparative examples 1-3 were tested according to the test method. The results are shown in Table 1.

[0042] Table 1

[0043]

[0044]

[0045] As can be seen from Table 1, the protective wax prepared by the present invention has a dropping point of ≥95°C, a salt spray resistance of ≥1200h for metals (steel, copper, aluminum) covered with a 200-micron wax film, a 3-cm wax film does not crack at -60°C for 24h, and does not flow at 90°C, and the metal silver covered with a 200-micron wax film passes the hydrogen sulfide corrosion test, and the metal copper passes the sulfur dioxide corrosion test.

Claims

1. A protective wax for industrial electronic circuit boards, characterized in that: The protective wax for industrial electronic circuit boards comprises, by weight, 60-75 parts of microcrystalline wax, 10-15 parts of low-temperature toughening agent, 6-8 parts of cerium dodecyl stearate, 5-7 parts of 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt and 1-3 parts of ethylene propylene diene rubber; The preparation method of the cerium dodecyl stearate comprises the following steps: adding an appropriate amount of cerium dodecyl stearate to deionized water, heating to 50°C, stirring evenly, dripping a sodium hydroxide aqueous solution, and after the dripping is completed, slowly heating the system to 90°C, and continuing to stir for 2 hours to obtain a sodium dodecyl stearate salt water dispersion; then adding an appropriate amount of cerium nitrate, continuing to stir at 90°C for 6 hours, cooling to 5-10°C, filtering, washing the obtained precipitate with water until it is neutral, and vacuum drying to obtain cerium dodecyl stearate; The preparation method of the 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt comprises the following steps: adding a small amount of 40-50°C deionized water to hydrogenated tallow amine, dispersing at 2000 rpm for 10-20 minutes to obtain a hydrogenated tallow amine aqueous dispersion; then slowly adding concentrated hydrochloric acid dropwise to obtain a hydrogenated tallow amine hydrochloride dispersion; adding an appropriate amount of ethanol and 2,5-dimercapto-1,3,4-thiadiazole to a sodium hydroxide aqueous solution to obtain a mixed solution; adding the hydrogenated tallow amine hydrochloride dispersion to the obtained mixed solution, stirring at 80°C for 4 hours, cooling to room temperature, filtering, washing the obtained precipitate with water and ethanol in turn, and drying to obtain the 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt.

2. A protective wax for industrial electronic circuit boards according to claim 1, characterized in that: The microcrystalline wax is No. 80 microcrystalline wax.

3. The protective wax for industrial electronic circuit boards according to claim 1, characterized in that: The low temperature toughening agent is dioctyl sebacate and / or dioctyl phthalate.

4. The protective wax for industrial electronic circuit boards according to claim 1, characterized in that: In terms of mass ratio, dodecaned stearic acid: deionized water: sodium hydroxide aqueous solution: cerium nitrate = 10:10:5-7:14-17.

5. The protective wax for industrial electronic circuit boards according to claim 1, characterized in that: In terms of mass ratio, hydrogenated tallow amine: deionized water: concentrated hydrochloric acid: sodium hydroxide aqueous solution: ethanol: 2,5-dimercapto-1,3,4-thiadiazole = 10:10:3-5:10:2:4-6.

6. The method for preparing a protective wax for industrial electronic circuit boards according to claim 1, characterized in that: The preparation method comprises the following steps: cutting EPDM into small pieces, soaking the pieces in a low-temperature toughening agent for 24 hours, heating the pieces to 70°C and stirring the pieces for 3 hours; adding 2,5-dimercapto-1,3,4-thiadiazole fatty amine salt and stirring the pieces for 30 minutes; adding cerium dodecyl stearate and stirring the pieces for 30 minutes; heating the pieces to 100°C and adding microcrystalline wax and stirring the pieces for 1 hour to obtain an oily liquid, cooling the pieces and granulating the pieces to obtain protective wax for industrial electronic circuit boards.

7. Use of the protective wax according to claim 1 in industrial electronic circuit boards.

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