Waterproof electronic circuit board three-proofing glue and preparation method thereof
By preparing a waterproof conformal coating for electronic circuit boards, the problem of insufficient waterproof performance in existing technologies has been solved, achieving effective waterproofing in extreme environments, reducing failure rates and maintenance costs, and improving production efficiency and equipment reliability.
Patent Information
- Application Number
- CN202511417585.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2025-12-19
AI Technical Summary
Existing technologies have not solved the problem of waterproof performance in outdoor lighting driver boards, especially since the waterproof performance of outdoor lighting driver boards has not been optimized for extreme humid scenarios such as long-term immersion and alternating high humidity, which leads to problems such as short circuits caused by moisture on the circuit board and corrosion of solder joints.
A waterproof conformal adhesive for electronic circuit boards is prepared by using specific processes and raw materials, including polycarbodiimide, epichlorohydrin, Pd(CH3CN)2Cl2 catalyst, silane coupling agent, etc., to form a stable adhesive layer, improve interfacial adhesion and thermal stability, and block moisture penetration.
It significantly reduces the failure rate of circuit boards, enhances the interfacial adhesion between the adhesive layer and the substrate, extends the service life of equipment, reduces maintenance costs, and improves production efficiency and product reliability.
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Figure SMS_1
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of waterproof coating, in particular to a waterproof electronic circuit board three-proofing glue and a preparation method thereof. BACKGROUND
[0002] The electronic circuit board three-proofing glue, also known as electronic coating glue, is a functional protective material specially used on the surface of electronic circuit boards and components. Its core function is to form a continuous and dense protective film on the surface of the circuit board substrate, solder joints and electronic components, effectively isolating moisture, dust, salt spray, chemical corrosive gases (such as hydrogen sulfide, ammonia, etc.) and slight mechanical friction in the external environment, thereby inhibiting the occurrence of circuit board faults such as electrical leakage, short circuit, solder joint oxidation, component corrosion, etc., ultimately extending the service life of electronic equipment and improving its working reliability in complex environments. With the development of electronic equipment towards miniaturization and high integration, and the gradual expansion of application scenarios to outdoor, bathroom, industrial humid workshop and other harsh environments, three-proofing glue has become one of the key materials indispensable to protect the core performance of the circuit board.
[0003] At present, the mainstream electronic coating glue on the market can be divided into UV (ultraviolet light) curing type, heat curing type and room temperature curing type according to the curing method. Among them, UV curing electronic coating glue has the advantages of fast curing speed, no need for high temperature heating (avoiding damage to heat-sensitive components), low VOC (volatile organic compound) content, etc., and is widely used in consumer electronics, smart home and other fields. However, the existing UV curing electronic coating glue focuses on the basic corrosion prevention needs in the conventional environment, and its waterproof performance is not optimized for long-term immersion, high humidity alternation and other extreme humid scenarios, resulting in obvious performance short board in specific applications.
[0004] Specifically, in scenarios such as the interior of bathroom equipment (such as the control panel of a smart toilet, the circuit board of a bathroom thermostatic valve), outdoor electronic equipment (such as outdoor lighting drive boards, meteorological monitoring instruments), etc., the circuit board needs to be in a high humidity environment for a long time, and may face the challenge of continuous condensation of water, short-term immersion in cleaning water (such as water splashing or short-term immersion during cleaning of bathroom equipment), outdoor rainy days-sunlight alternation (recurrent thermal expansion and cold contraction of the glue layer caused by high humidity after rain and high temperature in sunlight), etc. In this kind of scenario, although the existing UV curing coating glue can initially block the rapid intrusion of water, the water in the environment gradually penetrates into the glue layer through micro cracks, and eventually contacts the copper foil circuit and solder joints of the circuit board, causing problems such as circuit board dampness, short circuit, solder joint corrosion failure, etc., which seriously affects the stability and safety of electronic equipment.
[0005] Based on this, the present application designs a waterproof electronic circuit board three-proofing glue and a preparation method thereof to solve the above problems. SUMMARY
[0006] In view of the above-mentioned defects of the prior art, the present application provides a preparation method of waterproof electronic circuit board three-proofing glue, comprising the following steps: S1: preparation of waterproof agent, 35-45 parts of epichlorohydrin are added dropwise into 100 parts of polycarbodiimide, 0.5-1 parts of Pd(CH3CN)2Cl2 is added as a catalyst, and reaction is carried out; after the reaction is completed, the temperature is raised, and the treatment is carried out under vacuum conditions for 30-60 min, and the temperature is naturally cooled; and the waterproof agent is obtained; S2. Preparation of waterproof additive, 10-15 parts of deionized water and 20-32 parts of anhydrous ethanol are mixed and stirred, acetic acid is added dropwise to adjust the pH, and the silane coupling agent is added at a uniform speed; after the dropwise addition is completed, the temperature is raised, the stirring is continued, and then the temperature is naturally lowered to obtain the waterproof additive; S3. The raw materials are weighed, including 30-50 parts of polyurethane resin, 15-23 parts of UV monomer, 1.5-2.4 parts of leveling agent, 1.3-2.6 parts of defoaming agent, 1-4 parts of waterproof agent, 0.3-0.8 parts of waterproof additive, 2-5 parts of photoinitiator, and 0.05-0.2 parts of polymerization inhibitor; S4. Compounding; 4.1 The waterproof agent and the waterproof additive are premixed to obtain a waterproof agent-additive composite; 4.2 The polyurethane resin is added to the reaction kettle, the UV monomer is added in two portions, the temperature is raised to 40-45 DEG C after the second addition, the mixing is continued, the leveling agent is added and stirred, the defoaming agent is added and continues to be stirred, the premixed waterproof agent-additive composite is added in three equal portions, the temperature is raised to 50-60 DEG C after all the addition, and the stirring is continued; 4.3 The temperature is reduced to 30-35 DEG C, the polymerization inhibitor is added and stirred, the photoinitiator is added and mixed, filtration is carried out, and the product is obtained after standing and defoaming to obtain the waterproof electronic circuit board three-proofing glue.
[0007] Further, S1 specifically comprises: in a conventional reaction kettle equipped with a stirrer, a temperature control device and nitrogen protection, 100 parts of polycarbodiimide is added, nitrogen is introduced to replace air, and the temperature is raised to 60-80 DEG C; 35-45 parts of epichlorohydrin are added dropwise at a speed of 1-2 parts / min, 0.5-1 parts of Pd(CH3CN)2Cl2 is added as a catalyst, the stirring speed is kept at 500-800 r / min, and constant temperature reaction is carried out for 1-2 hours; After the reaction is completed, the temperature is raised to 100-110 DEG C, the treatment is carried out under the condition of vacuum degree-0.08 to-0.099 MPa for 30-60 min, the temperature is naturally cooled to below 40 DEG C, and the waterproof agent is obtained.
[0008] Further, S2 is specifically: adding deionized water 10-15 parts and anhydrous ethanol 20-32 parts into a dispersion kettle, stirring at 300-400 r / min for 3-5 min, adding acetic acid to adjust pH to 3.5-4.5, keeping the speed unchanged, adding silane coupling agent KH-560 at a speed of 5-10 parts / min, after dropwise adding, increasing the temperature to 30-35 DEG C, adjusting the speed to 500-600 r / min, continuing to stir for 30-45 min, after stirring, naturally cooling to 25-30 DEG C, to obtain a waterproof additive.
[0009] Further, S4.1 is specifically: premixing the waterproof agent and the waterproof additive at 25-30 DEG C and 600-800 r / min for 15-20 min to obtain a waterproof agent-additive compound.
[0010] Further, S4.2 is specifically: adding polyurethane resin into a reaction kettle, at an initial temperature of 30-35 DEG C and a speed of 500-600 r / min, adding UV monomer in two times with an interval of 3-5 min, after the second time, adjusting the speed to 700-800 r / min, increasing the temperature to 40-45 DEG C at a rate of 1-2 DEG C / min, continuing to mix for 30-40 min, keeping the temperature at 40-45 DEG C and adjusting the speed to 600-700 r / min, adding a leveling agent and stirring for 8-10 min, then adding a defoaming agent and continuing to stir for 10-15 min, adding the premixed waterproof agent-additive compound in three equal portions with an interval of 5-8 min, after all the addition, increasing the temperature to 50-60 DEG C at a rate of 0.5-1 DEG C / min, continuing to stir at 900-1000 r / min for 10-15 min.
[0011] Further, S4.3 is specifically: decreasing the temperature to 30-35 DEG C at a rate of 2-5 DEG C / min, adding a polymerization inhibitor and stirring for 15-18 min, adding a photoinitiator, mixing at 400-500 r / min for 25-30 min, filtering through a 100-200 mesh filter under a pressure of 0.1-0.2 MPa, standing for 15-20 min under the conditions of 30-35 DEG C and a vacuum degree of -0.09 to -0.095 MPa to remove bubbles, to obtain a waterproof electronic circuit board three-proofing glue.
[0012] A three-proofing glue prepared according to the preparation method of the waterproof electronic circuit board three-proofing glue.
[0013] Compared with the prior art, the present application has the following beneficial effects: 1. The three-proofing glue prepared by the present application can effectively block water penetration, avoid short circuit, solder corrosion and other faults caused by water contact with copper foil circuit or solder joints on the circuit board, thereby significantly reducing the failure rate of terminal products in extreme environments, reducing the cost of human and material maintenance after sale, improving product market reputation and enhancing competitiveness.
[0014] 2、The waterproof additive prepared by the specific process can significantly improve the interfacial adhesion of the adhesive layer and the substrate, and remains stable in long-term harsh environment. In actual production process of the circuit board, the stable adhesion can avoid delamination of the adhesive layer during assembly, transportation or use, reduce the rework and glue supplement process after spraying of the circuit board, reduce the production failure rate, and improve the overall efficiency of the production line.
[0015] 3、The waterproof additive prepared by the specific process can significantly improve the interfacial adhesion of the adhesive layer and the substrate, and remains stable in long-term harsh environment. In actual production process of the circuit board, the stable adhesion can avoid delamination of the adhesive layer during assembly, transportation or use, reduce the rework and glue supplement process after spraying of the circuit board, reduce the production failure rate, and improve the overall efficiency of the production line. DETAILED DESCRIPTION
[0016] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.
[0017] Embodiment 1: The present embodiment provides a preparation method of a waterproof electronic circuit board three-proofing adhesive, comprising the following steps: S1: Preparation of waterproof agent; In a conventional reaction kettle equipped with a stirrer, a temperature control device and nitrogen protection, 100 parts of polycarbodiimide were added, nitrogen was introduced (flow rate 0.5 L / min) to replace air, and then the temperature was raised to 60℃; 35 parts of epoxy chloropropane were added at a rate of 1 part / min, and 0.5 parts of Pd(CH3CN)2Cl2 as a catalyst (CAS No. 14592-56-4) were added at the same time, the stirring speed was kept at 500 r / min, and the constant temperature reaction was carried out for 1 hour; After the reaction was completed, the temperature was raised to 100℃, and the vacuum degree was-0.08 MPa for 30 min, and then the temperature was naturally cooled to below 40℃, to obtain the waterproof agent; S2. Preparation of waterproof additive; Into a dispersion kettle, 10 parts of deionized water and 20 parts of anhydrous ethanol were added, stirred at 300 r / min for 3 min, acetic acid was added dropwise to adjust the pH to 3.5-4.5, the stirring speed was kept unchanged, the silane coupling agent KH-560 was added at a speed of 5 parts / min, after the dropwise addition was completed, the temperature was raised to 30℃, the stirring speed was adjusted to 500 r / min, and the stirring was continued for 30 min, after the stirring was completed, the temperature was naturally lowered to 25℃, and a waterproof additive was obtained; The prepared waterproof additive needs to be added into the "waterproof agent-additive composite" premixing process (i.e. step S4.1) within 1 hour; S3. Weigh the raw materials; Polyurethane resin (AH-1704B-2) 30 parts, UV monomer (ethoxylated trimethylolpropane triacrylate, CAS number 28961-43-5) 15 parts, leveling agent (ZY-1603) 1.5 parts, defoaming agent (PX-130) 1.3 parts, waterproof agent 1 part, waterproof additive 0.3 part, photoinitiator (1-hydroxycyclohexyl phenyl ketone) 2 parts, polymerization inhibitor (p-methoxyphenol) 0.05 parts; S4. Compound; 4.1 The waterproof agent and the waterproof additive were premixed at 25℃ and 600 r / min for 15 min to obtain a waterproof agent-additive composite; 4.2 Into the reaction kettle, polyurethane resin was added, at the initial temperature of 30℃ and the stirring speed of 500 r / min, UV monomer was added in two times (the mass ratio of the two times was 4:5) with an interval of 3 min, after the second addition, the stirring speed was adjusted to 700 r / min, the temperature was raised to 40℃ at a rate of 1℃ / min, and the mixing was continued for 30 min, the temperature was kept at 40℃, the stirring speed was adjusted to 600 r / min, the leveling agent was added and stirred for 8 min, the defoaming agent was added and continued to stir for 10 min, the premixed waterproof agent-additive composite was added in three equal portions with an interval of 5 min, after all the addition, the temperature was raised to 50℃ at a rate of 0.5℃ / min, and the stirring was continued at 900 r / min for 10 min; 4.3 The temperature was lowered to 30℃ at a rate of 2℃ / min, the polymerization inhibitor was added and stirred for 15 min, the photoinitiator was added, and the mixing was continued at 400 r / min for 25 min, the filter screen of 100 mesh was used to filter under the pressure of 0.1 MPa, and the defoaming was carried out at 30℃ and the vacuum degree of-0.09 MPa for 15 min, and a waterproof electronic circuit board three-proofing glue was obtained.
[0018] Example 2: A preparation method of a waterproof electronic circuit board three-proofing glue is provided, which comprises the following steps: S1: Preparation of waterproof agent; In a conventional reaction kettle equipped with a stirrer, a temperature control device and nitrogen protection, 100 parts of polycarbodiimide was added, nitrogen was introduced (flow rate 1 L / min) to replace the air, and then heated to 80°C; Epoxy chloropropane was added at a rate of 45 parts / min, and 1 part of Pd(CH3CN)2Cl2 was added as a catalyst, the stirring speed was kept at 800 r / min, and the reaction was kept at a constant temperature for 2 hours; After the reaction was completed, the temperature was raised to 110°C, and the vacuum degree was-0.099 MPa for 60 min, and then the temperature was naturally cooled to below 40°C to obtain the waterproof agent; S2. Preparation of waterproofing aid; Deionized water 15 parts and anhydrous ethanol 32 parts were added to a dispersion kettle, stirred at 400 r / min for 5 min, acetic acid was added to adjust the pH to 3.5-4.5, the stirring speed was kept unchanged, and the silane coupling agent KH-560 was added at a uniform speed of 10 parts / min. After the dropwise addition was completed, the temperature was raised to 35°C, the stirring speed was adjusted to 600 r / min, and the stirring was continued for 45 min. After the stirring was completed, the temperature was naturally cooled to 30°C to obtain the waterproofing aid; The prepared waterproofing aid needs to be added into the "waterproofing agent-aid compound" premixing process (i.e. step S4.1) within 1 hour; S3. Weigh the raw materials; Polyurethane resin 50 parts, UV monomer (ethoxylated trimethylolpropane triacrylate) 23 parts, leveling agent (ZY-1603) 2.4 parts, defoaming agent (PX-130) 2.6 parts, waterproofing agent 4 parts, waterproofing aid 0.8 parts, photoinitiator (1-hydroxycyclohexyl phenyl ketone) 5 parts, polymerization inhibitor (p-methoxyphenol) 0.2 parts; S4. Compound; 4.1 The waterproofing agent and waterproofing aid were premixed at 30°C and 800 r / min for 20 min to obtain a waterproofing agent-aid compound; 4.2 The polyurethane resin was added to the reaction kettle, the UV monomer was added in two portions (mass ratio of 7:9) at an initial temperature of 35°C and a stirring speed of 600 r / min, with an interval of 5 min, the stirring speed was adjusted to 800 r / min after the second addition, the temperature was raised to 45°C at a rate of 2°C / min, and the mixing was continued for 40 min. Keep the temperature at 45°C and adjust the stirring speed to 700 r / min, add the leveling agent and stir for 10 min, then add the defoaming agent and continue stirring for 15 min, divide the premixed waterproofing agent-aid compound into three equal portions, add with an interval of 8 min, and after all the addition, raise the temperature to 60°C at a rate of 1°C / min, continue stirring at 1000 r / min for 15 min; 4.3 The temperature was decreased to 35℃ at a rate of 5℃ / min, the polymerization inhibitor was added, stirred for 18 min, the photoinitiator was added, mixed at 500 r / min for 30 min, filtered using a 200 mesh filter at a pressure of 0.2 MPa, deaerated at 35℃, a vacuum degree of -0.095 MPa for 20 min, to obtain the waterproof electronic circuit board three-proofing glue.
[0019] Example 3: The present embodiment provides a preparation method of a waterproof electronic circuit board three-proofing glue, comprising the following steps: S1: Preparation of waterproof agent; In a conventional reaction kettle equipped with a stirrer, temperature control device and nitrogen protection, 100 parts of polycarbodiimide was added, nitrogen was introduced (flow rate 0.6 L / min) to replace air, and then heated to 65℃; 37 parts of epoxy chloropropane were added at a rate of 2 parts / min, 0.9 parts of Pd(CH3CN)2Cl2 was added as catalyst, the stirring speed was kept at 600 r / min, and the temperature was kept constant for 2 hours; After the reaction was completed, the temperature was increased to 102℃, treated at a vacuum degree of -0.09 MPa for 50 min, and naturally cooled to below 40℃, to obtain the waterproof agent; S2. Preparation of waterproof additive; Deionized water 12 parts and anhydrous ethanol 24 parts were added to a dispersion kettle, stirred at 320 r / min for 4 min, acetic acid was added to adjust the pH to 3.5-4.5, the stirring speed was kept constant, and the silane coupling agent KH-560 was added at a rate of 6 parts / min, after the addition was completed, the temperature was increased to 32℃, the stirring speed was adjusted to 580 r / min, and the stirring was continued for 35 min, after the stirring was completed, the temperature was naturally cooled to 25℃, to obtain the waterproof additive; The prepared waterproof additive needs to be added within 1 hour in the "waterproof agent-additive compound" premixing process (i.e. step S4.1); S3. Weigh the raw materials; Polyurethane resin 45 parts, UV monomer (ethoxylated trimethylolpropane triacrylate) 18 parts, leveling agent (ZY-1603) 1.9 parts, defoaming agent (PX-130) 2.1 parts, waterproof agent 1.2 parts, waterproof additive 0.5 parts, photoinitiator (1-hydroxycyclohexyl phenyl ketone) 4 parts, polymerization inhibitor (p-methoxyphenol) 0.11 parts; S4. Compound; 4.1 The waterproof agent and waterproof additive were premixed at 28℃, 650 r / min for 18 min to obtain the waterproof agent-additive compound; 4.2 Add polyurethane resin into the reaction kettle, at initial temperature 33℃, rotation speed 560r / min, add UV monomer in 2 times (mass ratio of 2 times is 6:7), interval 4min, after the second time, adjust the rotation speed to 720r / min, heat to 44℃ at the rate of 2℃ / min, continue mixing for 32min, keep the temperature at 42℃, adjust the rotation speed to 660r / min, add leveling agent and stir for 9min, then add defoaming agent and continue stirring for 12min, add the premixed waterproof agent-aid composite in 3 equal parts, interval 5min, after all added, heat to 58℃ at the rate of 0.8℃ / min, continue stirring at 900r / min for 10min; 4.3 Reduce the temperature to 33℃ at the rate of 3℃ / min, add polymerization inhibitor and stir for 16min, add photoinitiator, mix for 27min at 400r / min, filter using 200 mesh filter screen under the pressure of 0.1MPa, stand for 15min under the condition of 33℃, vacuum degree-0.09MPa to remove bubbles, obtain waterproof electronic circuit board three-proofing glue.
[0020] Comparative Example 1: The difference between this comparative example and Example 3 is that the Pd(CH3CN)2Cl2 catalyst is replaced by Ni(CH3CN)2Cl2 catalyst.
[0021] Comparative Example 2: The difference between this comparative example and Example 3 is that in S1, the number of parts of epichlorohydrin is increased to 55 parts.
[0022] Comparative Example 3: The difference between this comparative example and Example 3 is that the silane coupling agent KH-560 is directly selected as the waterproof aid.
[0023] Comparative Example 4: The difference between this comparative example and Example 3 is that the Pd(CH3CN)2Cl2 catalyst is replaced by Ni(CH3CN)2Cl2 catalyst; the number of parts of epichlorohydrin is increased to 55 parts; and the silane coupling agent KH-560 is directly selected as the waterproof aid.
[0024] Curing method: Use anhydrous ethanol to wipe the surface of the circuit board (take the double-sided IC open pcb circuit board produced by Huizhou Jiehao Circuit Technology Co., Ltd. as an example) with a dust-free cloth, focusing on removing oil stains, residual flux, dust and other impurities at the solder joints, copper foil lines and component pins; if the circuit board has stubborn stains, it can be soaked in anhydrous ethanol for 15s and then taken out, then cleaned with a dust-free cloth, and then placed in a clean environment at 30℃ and relative humidity ≤50% for 15min to ensure that the surface of the circuit board is completely dry without residual water or cleaning agent; The conformal coatings prepared in each embodiment and comparative example were applied using a pneumatic spray gun with a nozzle diameter of 0.3 mm, a spraying pressure of 0.3 MPa, and a distance of 20 cm from the surface of the circuit board. The coating was applied at a uniform speed (5 cm / s) in the horizontal direction for 3 coats (with a 30-second interval between each coat). Turn on the UV curing machine, select a UV light source with a wavelength of 300-365nm, and adjust the UV light intensity to 100mW / cm². 2 Curing time is 30-40 seconds.
[0025] Experimental example: The insulation resistivity was determined according to the method of GB / T 1692-2008 "Determination of Insulation Resistivity of Vulcanized Rubber".
[0026] The peel strength was determined according to the method of GB / T 7122-1996 "Determination of peel strength of high strength adhesives - floating roller method".
[0027] The coefficient of thermal expansion was determined according to the method in GB / T 36800.2-2018 "Determination of linear thermal expansion coefficient and glass transition temperature".
[0028] Each group of cured conformal adhesives was soaked in bathroom cleaning water (deionized water + 0.1% nonionic surfactant) for 168 hours. After soaking, the insulation resistivity, peel strength and coefficient of thermal expansion were measured again using the above method.
[0029] The cured conformal coatings were subjected to various conditions, referencing the alternating acid rain and sun exposure characteristics of a subtropical monsoon climate. One cycle was designed to consist of one acid rain spray and one sun exposure cycle, for a total of 20 cycles. During the acid rain phase, the temperature was controlled at 15±2℃, relative humidity at 95±2%, duration at 4 hours, and water pressure at 0.2MPa, with the spray direction perpendicular to the sample surface. During the sun exposure phase, the UV intensity was adjusted to 25±3mW / cm². 2 The temperature was increased to 65±2℃, and the relative humidity was reduced to 30±5% for 4 hours. After the alternating cycle, the insulation resistivity, peel strength, and coefficient of thermal expansion were measured again using the above method.
[0030] The results are shown in the table below:
[0031] The insulation resistivity directly reflects the barrier ability of the adhesive layer to moisture penetration, the less the insulation resistivity decreases, the less the moisture penetration amount is, and the more stable the waterproof insulation effect of the adhesive layer is. As shown in the above table, the insulation resistivity of the embodiment only slightly decreases after immersion and alternating circulation, without large fluctuations, while the insulation resistivity of Comparative Examples 3 and 4 greatly decreases after immersion, which means that the adhesive layer of the embodiment can effectively block the moisture from entering and avoid short circuit caused by the moisture contacting the copper foil / welding point of the circuit board. The adhesive layer of Comparative Examples is prone to micro cracks due to improper formulation or process, resulting in moisture penetration and damage to insulation performance. The peel strength reflects the interfacial adhesion between the adhesive layer and the circuit board substrate, the less the peel strength decreases, the more stable the adhesive force of the adhesive layer is, and the less likely the adhesive layer separates from the substrate to form a gap. The peel strength of the embodiment decreases very little after the two harsh conditions, and always maintains strong interfacial adhesion. The peel strength of Comparative Examples 3 and 4 significantly decreases after immersion. This shows that the preparation process of the waterproof additive in the present application is crucial, and direct use of silane coupling agent cannot form stable interfacial adhesion, which is prone to separation of the adhesive layer from the substrate to provide a channel for moisture penetration under long-term harsh environment. The waterproof additive of the embodiment can strengthen the bonding between the adhesive layer and the substrate to avoid interfacial failure. The thermal expansion coefficient determines the dimensional change of the adhesive layer under temperature alternation, the smaller the change of the thermal expansion coefficient is, the better the thermal matching between the adhesive layer and the circuit board substrate is, and the less likely the adhesive layer produces micro cracks due to thermal expansion and contraction. The thermal expansion coefficient of the embodiment only slightly fluctuates after alternating circulation, and the dimensional stability is excellent. The thermal expansion coefficient of Comparative Example 4 sharply increases after alternating circulation, which is much higher than that of the embodiment. This shows that the catalyst in the original formulation is more beneficial to improving the thermal stability of the adhesive layer than the replaced catalyst; the amount of epoxy chloropropane needs to be controlled within the range of 35-45 parts, and excessive amount will damage the thermal structural stability of the adhesive layer; at the same time, the absence of the preparation process of the waterproof additive (Comparative Examples 3 and 4) will also lead to the decrease of the thermal matching of the adhesive layer, and finally produce cracks due to the large difference in thermal expansion coefficient under temperature and humidity alternation.
[0032] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for preparing a waterproof electronic circuit board three-proofing glue, characterized in that, Comprising the following steps: S1: Preparation of waterproofing agent, 35-45 parts of epichlorohydrin are added dropwise to 100 parts of polycarbodiimide, and 0.5-1 parts of Pd(CH3CN)2Cl2 is added as a catalyst, and the reaction is carried out; After the reaction is completed, the temperature is raised, and the treatment is carried out under vacuum conditions for 30-60 min, and the natural cooling is carried out to reduce the temperature, and the waterproofing agent is obtained. S2. Preparation of waterproofing aid, deionized water 10-15 parts and anhydrous ethanol 20-32 parts are mixed and stirred, acetic acid is added dropwise to adjust the pH, and silane coupling agent is added at a uniform speed, after the dropwise addition is completed, the temperature is raised, and the natural cooling is carried out after the continuous stirring, and the waterproofing aid is obtained. S3. The raw materials are weighed, polyurethane resin 30-50 parts, UV monomer 15-23 parts, leveling agent 1.5-2.4 parts, defoaming agent 1.3-2.6 parts, waterproofing agent 1-4 parts, waterproofing aid 0.3-0.8 parts, photoinitiator 2-5 parts, and polymerization inhibitor 0.05-0.2 parts. S4. Compound; 4.1 The waterproofing agent and the waterproofing aid are premixed to obtain a waterproofing agent-aid composite; 4.2 The polyurethane resin is added to the reaction kettle, the UV monomer is added in two portions, the temperature is raised to 40-45℃ after the second addition, the mixing is continued, the leveling agent is added and stirred, the defoaming agent is added and continues to be stirred, the premixed waterproofing agent-aid composite is added in three equal portions, the temperature is raised to 50-60℃ after all the addition, and the stirring is continued; 4.3 The temperature is reduced to 30-35℃, the polymerization inhibitor is added and stirred, the photoinitiator is added and mixed, filtered, and deaerated to obtain a waterproof electronic circuit board three-proofing glue.
2. The preparation method of the waterproof electronic circuit board three-proofing glue according to claim 1, characterized in that, S1 is specifically: in a conventional reaction kettle equipped with a stirrer, a temperature control device and nitrogen protection, 100 parts of polycarbodiimide is added, nitrogen is introduced to replace air, and the temperature is raised to 60-80℃; 35-45 parts of epichlorohydrin are added dropwise at a speed of 1-2 parts / min, and 0.5-1 parts of Pd(CH3CN)2Cl2 is added as a catalyst, the stirring speed is kept at 500-800 r / min, and the constant temperature reaction is carried out for 1-2 hours; After the reaction is completed, the temperature is raised to 100-110℃, and the treatment is carried out under the vacuum degree of -0.08 to -0.099 MPa for 30-60 min, and the natural cooling is carried out to reduce the temperature to below 40℃, and the waterproofing agent is obtained.
3. The method for preparing the waterproof electronic circuit board conformal adhesive according to claim 1, characterized in that, S2 is specifically: deionized water 10-15 parts and anhydrous ethanol 20-32 parts are added to a dispersion kettle, stirred at 300-400 r / min for 3-5 min, acetic acid is added dropwise to adjust the pH to 3.5-4.5, the stirring speed is kept unchanged, silane coupling agent KH-560 is added at a speed of 5-10 parts / min, the temperature is raised to 30-35℃ after the dropwise addition is completed, the stirring speed is adjusted to 500-600 r / min, the stirring is continued for 30-45 min, and the natural cooling is carried out to reduce the temperature to 25-30℃ after the stirring is completed, and the waterproofing aid is obtained.
4. The method of claim 1, wherein the waterproof electronic circuit board three-proofing glue is prepared by mixing the waterproof electronic circuit board three-proofing glue composition with a solvent. S4.1 is specifically: the waterproofing agent and the waterproofing aid are premixed at 25-30℃ and 600-800 r / min for 15-20 min to obtain a waterproofing agent-aid composite.
5. The method of claim 1, wherein the waterproof electronic circuit board three-proofing glue is prepared by mixing the waterproof electronic circuit board three-proofing glue composition with a solvent. S4.2 is specifically: polyurethane resin is added to the reaction kettle, at an initial temperature of 30-35℃, a rotation speed of 500-600r / min, UV monomer is added in two times with an interval of 3-5min, the rotation speed is adjusted to 700-800r / min after the second addition, the temperature is increased to 40-45℃ at a rate of 1-2℃ / min, the mixing is continued for 30-40min, the temperature is maintained at 40-45℃, the rotation speed is adjusted to 600-700r / min, the leveling agent is added and stirred for 8-10min, the defoaming agent is added and stirred for 10-15min, the premixed waterproof agent-additive compound is added in three equal portions with an interval of 5-8min, the temperature is increased to 50-60℃ at a rate of 0.5-1℃ / min after all the addition, the stirring is continued at 900-1000r / min for 10-15min.
6. The method for preparing the waterproof electronic circuit board conformal adhesive according to claim 1, characterized in that, S4.3 is specifically: the temperature is decreased to 30-35℃ at a rate of 2-5℃ / min, the polymerization inhibitor is added and stirred for 15-18min, the photoinitiator is added, the mixing is continued at 400-500r / min for 25-30min, the filter screen of 100-200 meshes is used to filter under a pressure of 0.1-0.2MPa, the defoaming is carried out at 30-35℃ under a vacuum degree of -0.09 to -0.095MPa for 15-20min, and the waterproof electronic circuit board three-proofing glue is obtained.
7. A three-proofing glue prepared by the preparation method of the waterproof electronic circuit board three-proofing glue according to any one of claims 1-6.