阅读说明：本技术 一种用于电子器件的有机防护镀层及其制备方法 (Organic protective coating for electronic device and preparation method thereof ) 是由 夏天益 曲永鹏 苏翠翠 于 2021-08-06 设计创作，主要内容包括：本发明涉及有机镀层技术领域,具体是一种用于电子器件的有机防护镀层及其制备方法。该有机防护镀层通过包括单体A和单体B的单体组合物在电子器件表面聚合反应得到；单体A为含有乙烯性双键和异氰酸酯基的烯烃类单体中的一种或多种；单体B的主链为饱和碳链主链、饱和杂链主链或含苯环的主链中的一种；单体B的端基为两个及两个以上的氨基,或两个及两个以上的羟基。该制备方法绿色环保,得到的镀层表面平滑,可与基底实现共形覆盖,透光性能好不会对光感元器件造成遮挡从而对使用性能产生影响；镀层的水氧阻隔性能好,氧气渗透性能低,对电化学腐蚀的抑制率高,可有效防止由于水接触到电路板造成的短路或者水氧共同作用下对电路板造成腐蚀。(The invention relates to the technical field of organic coatings, in particular to an organic protective coating for an electronic device and a preparation method thereof. The organic protective coating is obtained by the polymerization reaction of a monomer composition comprising a monomer A and a monomer B on the surface of an electronic device; the monomer A is one or more of olefin monomers containing ethylenic double bonds and isocyanate groups; the main chain of the monomer B is one of a saturated carbon chain main chain, a saturated hetero-chain main chain or a main chain containing benzene rings; the end group of the monomer B is two or more amino groups or two or more hydroxyl groups. The preparation method is green and environment-friendly, the obtained coating has smooth surface, can realize conformal coverage with a substrate, has good light transmittance, and cannot shield light-sensitive components so as to influence the use performance; the water and oxygen barrier property of the plating layer is good, the oxygen permeability is low, the inhibition rate to electrochemical corrosion is high, and the corrosion to the circuit board under the combined action of water and oxygen or the short circuit caused by the contact of water with the circuit board can be effectively prevented.)

1. An organic protective coating for an electronic device, comprising: the organic protective coating is obtained by polymerizing a monomer composition comprising a monomer A and a monomer B on the surface of an electronic device; wherein the content of the first and second substances,

the monomer A is one or more of olefin monomers containing ethylenic double bonds and isocyanate groups;

the main chain of the monomer B is one of a saturated carbon chain main chain, a saturated hetero-chain main chain or a main chain containing benzene rings;

the end group of the monomer B is two or more amino groups or two or more hydroxyl groups.

2. The organic protective coating for electronic devices of claim 1, wherein: the molar ratio of the monomer A to the monomer B is 5: 1-1: 5.

3. The organic protective coating for electronic devices of claim 2, wherein: the molar ratio of the monomer A to the monomer B is 1: 1.5-1.5: 1.

4. The organic protective coating for electronic devices of claim 1, wherein: the monomer A is isocyano ethyl methacrylate, methacrylic acid polyisocyanate or p-isocyanatostyrene.

5. The organic protective coating for electronic devices of claim 1, wherein: with respect to the monomer B, as the monomer,

when the main chain of the monomer B is a saturated carbon chain main chain, the main chain is hexamethylene diamine, hexanediol, diethanolamine, trihexylamine or resorcinol;

when the main chain of the monomer B is a saturated heterochain main chain, diethylene glycol di (3-aminopropyl) ether, 2,3, 3-tetrafluoro-1, 4-butanediol or 2- (butylamino) ethylamine;

when the main chain of the monomer B is the monomer B containing the main chain of a benzene ring, the main chain is p-phenylenediamine, 2,3,5, 6-tetramethyl-1, 4-phenylenediamine, resorcinol or 2, 3-dihydroxy methyl benzoate.

6. A method of preparing an organic protective coating for electronic devices according to any of the preceding claims, wherein: the method comprises the following steps: firstly, respectively heating and gasifying the monomer A, the monomer B and the initiator, respectively introducing the monomers into a vacuum cavity through different pipelines, and uniformly mixing the monomers after entering the cavity.

7. The method of claim 6, wherein: and introducing the monomer, and then introducing an initiator gasified at room temperature, heating the nickel-chromium alloy wire in the cavity to the temperature of 180 ℃ and 250 ℃ in the cavity, and growing a film on the substrate at the temperature of 10-50 ℃ to obtain the organic protective coating.

8. The method of claim 7, wherein: the substrate is metal, polymer material or inorganic material.

9. The method of claim 7, wherein: the saturated vapor pressure of the monomer A and the monomer B is 0.01 mmHg to 4 mmHg at 25 ℃.

Technical Field

The invention relates to the technical field of organic coatings, in particular to an organic protective coating for an electronic device and a preparation method thereof.

Background

In recent years, electronic devices such as smart wearable devices, smart phones, outdoor electronic facilities, and the like have been developed rapidly due to their excellent convenience and practicality. Such devices are usually exposed to the external environment for a long time, and are easily subjected to water immersion and environmental corrosion during use, and if the waterproof performance is not good, the electronic devices are easily damaged. For an apparatus which is partially exposed to the outdoor and is easily affected by the natural environment, the requirement for the waterproof performance is higher.

Therefore, the protection with high performance can protect the electronic equipment from the product damage caused by rain environment or electrochemical corrosion, thereby ensuring the quality of the product and prolonging the service life of the equipment.

With the development of the current electronic products gradually tending to flexibility and lightness, the conventional barrier films adopted conventionally at present cannot adapt. The traditional inorganic barrier film has excellent effects in the aspects of water resistance, water vapor resistance and gas barrier, but the poor flexibility of the inorganic film enables stress bending to easily cause damage, the damage limits the application of the inorganic barrier film in the period of electronic equipment, and the inorganic barrier film cannot effectively play a long-time protection effect on the electronic equipment.

Therefore, a polymer-based plating layer with high flexibility and high light transmittance is also an ideal means for protecting electronic devices and related devices, and particularly, a good light transmittance is required for use in devices having photosensitive elements. This requires that the barrier protective coating have excellent water and oxygen barrier properties and be capable of withstanding electrochemical corrosion in the event of electrochemical corrosion. However, not all polymer-based coatings are used for the protection of electronic products. Common polymer-based materials are not favorable for application in the field of electronic device protection due to high molecular chain flexibility and steric hindrance effect, which are often accompanied with high gas permeability.

In response to the problems associated with conventional inorganic barrier films and the existing less than ideal polymer-based coatings, improvements are needed to address these problems.

Disclosure of Invention

The invention aims to solve the problems and provides an organic protective coating for an electronic device, which has good light transmission performance, good water-oxygen barrier performance and excellent electrochemical corrosion resistance, and a corresponding preparation method.

The preparation method provided is that a compact organic cross-linked network protective layer is constructed through in-situ polymerization, and the cross-linking degree and compactness of the protective layer are improved under the combined action of free radical polymerization and condensation polymerization, so that the protective effect on electronic devices is improved.

The technical scheme adopted by the invention for solving the technical problems is as follows:

an organic protective coating for an electronic device, the organic protective coating being obtained by polymerizing a monomer composition comprising a monomer A and a monomer B on the surface of the electronic device; wherein the content of the first and second substances,

the monomer A is one or more of olefin monomers containing ethylenic double bonds and isocyanate groups;

the main chain of the monomer B is one of a saturated carbon chain main chain, a saturated hetero-chain main chain or a main chain containing benzene rings;

the end group of the monomer B is two or more amino groups or two or more hydroxyl groups.

Unlike the common free radical polymerization in polymer preparation, in the component system, besides the free radical polymerization of the monomer A, the isocyanate group in the monomer A and the amino or hydroxyl group in the monomer B can perform a condensation polymerization reaction with strong reactivity, which is beneficial to forming a higher crosslinking degree of the polymer. With the simultaneous free radical polymerization of the monomer A and the polycondensation of the monomer A and the monomer B on the surface of the circuit board, the plating layer has excellent rigidity, and water and oxygen are prevented from penetrating through the polymer to reach the surface of the substrate and are corroded and damaged by the redox reaction of the substrate material.

Further, when the monomer A and the monomer B are polymerized, the molar ratio of the monomer A to the monomer B is 5: 1-1: 5.

From the viewpoint of improving the crosslinking degree and the monomer utilization rate, the molar ratio of the monomer A to the monomer B is preferably 1: 1.5-1.5: 1, more preferably 1.25:1, and the molar ratio of the monomer A to the monomer B is in the range, so that the stable and compact crosslinked network barrier layer is constructed.

Further, the monomer A is isocyanoethyl methacrylate, polyisocyanate methacrylate or p-isocyanatostyrene.

Further, with respect to the monomer B,

when the main chain of the monomer B is a saturated carbon chain main chain, the main chain is hexamethylene diamine, hexanediol, diethanolamine, trihexylamine or resorcinol;

when the main chain of the monomer B is a saturated heterochain main chain, diethylene glycol di (3-aminopropyl) ether, 2,3, 3-tetrafluoro-1, 4-butanediol or 2- (butylamino) ethylamine;

when the main chain of the monomer B is the monomer B containing the main chain of a benzene ring, the main chain is p-phenylenediamine, 2,3,5, 6-tetramethyl-1, 4-phenylenediamine, resorcinol or 2, 3-dihydroxy methyl benzoate.

From the viewpoint of water oxygen barrier property and electrochemical corrosion resistance of the coating, high reactivity and chain segment rigidity are required to improve the chemical stability of the polymer coating, and a monomer B is preferred, wherein the main chain of the monomer B is one of a saturated carbon chain main chain or a benzene ring-containing main chain, and the end group of the monomer B is two or more amino groups.

Considering that the cross-linking between molecular chains is more beneficial to the improvement of the water oxygen barrier property and the electrochemical corrosion resistance of the coating, and during the cross-linking process, the chain segment length influences the cross-linking degree due to the steric hindrance effect, the monomer B is further preferably selected, wherein the main chain of the monomer B is a saturated carbon chain, and the carbon chain length is more than 4.

Based on the aspects of environmental protection and improvement of the uniformity of the coating, the invention also provides a technical route for preparing the protective coating of the electronic device in a full-dry mode, which comprises the following steps: the initiating chemical vapor deposition method is the combination and improvement of hot filament chemical vapor deposition and free radical polymerization, and is one new kind of green vacuum coating method. The free radical reaction in the gas phase environment to form polymer film on the substrate is a green and mild high molecular coating technology, so the copolymerization mode of the monomer composition is preferably initiated chemical vapor deposition. Particularly, different from the prior method of mixing the gases and then introducing the gases into the cavity, the monomers have self-crosslinking activity, so that the component gases are particularly required to be introduced separately and then mixed in the cavity.

The preparation method of the organic protective coating comprises the following steps: firstly, respectively heating and gasifying the monomer A, the monomer B and the initiator, respectively introducing the monomers into a vacuum cavity through different pipelines, and uniformly mixing the monomers after entering the cavity.

The gasified monomer A, monomer B and initiator are respectively introduced from different air inlets and are uniformly mixed in the cavity, and the vacuum degree in the reaction cavity is adjusted to be 200-800 mtorr.

Further, introducing the monomer, and then introducing an initiator gasified at room temperature, heating the nichrome wire in the cavity to the temperature of 180 ℃ in the cavity and 250 ℃, and growing a film on the substrate at the temperature of 10-50 ℃, so as to obtain the organic protective coating. The temperature of the substrate is controlled to be 10-50 ℃, and a 500-1000nm thin film is grown.

Further, the substrate is a metal, a polymer material or an inorganic material.

Further, the saturated vapor pressure of the monomer A and the monomer B is 0.01 mmHg to 4 mmHg at 25 ℃.

The base material of the barrier layer is not particularly limited since the production environment is mild and no solvent is introduced, and may be a metal, a polymer material, an electronic device, or the like.

Aiming at the method, the following steps are selected for facilitating the monomer to be input into the cavity after being gasified: the saturated vapor pressure of the monomer A and the monomer B is 0.01 mmHg to 4 mmHg at 25 ℃.

The invention has the beneficial effects that:

(1) the preparation method is green and environment-friendly, the surface of the coating is smooth, conformal coverage can be realized with the substrate, the light-sensitive element is not shielded due to good light transmittance, and the use performance is not influenced;

(2) good water and oxygen barrier property and oxygen permeability as low as 5.8 x 10^-13 cm³ cm/cm²s cmHg, the inhibition rate of electrochemical corrosion reaches 99.3%. Can effectively prevent the circuit board from short circuit caused by water contacting the circuit board or under the combined action of water and oxygenCausing corrosion.

Drawings

FIG. 1 is an infrared spectrum of the protective coating obtained in example 2.

FIG. 2 is a light transmittance test chart of the protective plating layer obtained in example 2.

FIG. 3 is a test chart of electrochemical corrosion resistance of the protective coating obtained in example 2.

Fig. 4 is a water resistance test chart of the protective plating obtained in example 2.

Detailed Description

The representative embodiments based on the figures will now be further refined. The following description is not intended to limit the embodiments to one preferred embodiment, but to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the described embodiments as defined by the appended claims.

The invention provides an organic protective coating for an electronic device, which is obtained by polymerization reaction of an organic composition comprising a monomer A and a monomer B on the surface of a substrate.

Example 1:

the monomer A is ethyl isocyanate methacrylate (IEM), the monomer B is 1, 6-hexamethylene diamine (HEA), di-tert-butyl peroxide is used as an initiator, and polished copper sheets and integrated circuit boards are used as base materials.

In the coating process, the integrated circuit board and the copper sheet are taken as base materials and put on a sample table in the cavity, and the temperature of the sample table is controlled to be 10-50 ℃. And starting a vacuum pump to vacuumize the cavity, heating the monomers IEM and HEA to 65 ℃ and 50 ℃ respectively to vaporize, regulating the flow through a needle valve, and introducing into the cavity. Wherein the IEM flow is controlled to be 0.4 sccm; HEA flow rate of 0.8 sccm; the di-tert-butyl peroxide is gasified and introduced into the cavity at room temperature, the flow is controlled to be 0.7 sccm, the vacuum degree of the reaction cavity is kept to be 300-500 mtorr, a heating wire in the reaction cavity is controlled to be 180-250 ℃, the substrate temperature is 42 ℃, the deposition time is about 40min, and the coating thickness is about 800 nm.

Tests show that the electrochemical corrosion inhibition rate of the organic protective coating of the electronic device obtained in example 1 on metal in 3.5% NaCl solution reaches 78%. The metal corrosion-resistant coating has a certain metal corrosion-resistant effect, and the observation of the surface through an electron scanning microscope shows that the coating has larger particles, and the judgment is that the surface is too rough due to too rapid self-crosslinking reaction of HEA and IEM caused by excessive HEA, so that partial void channels are generated.

Example 2:

the monomer A is IEM, the monomer B is HEA, di-tert-butyl peroxide is used as an initiator, and the polished copper sheet and the integrated circuit board are used as base materials.

Controlling the IEM flow to be 0.4 sccm; HEA flow rate of 0.3 sccm; the other preparation processes are the same as above.

As shown in the attached FIG. 1, the high crosslinking polymer coating prepared in example 2 was characterized by IR spectroscopy, and p (IEM-co-HEA) was 275cm^-1The characteristic peak belongs to an asymmetric stretching vibration peak of an isocyanate group (-N = C = O) which is specific to IEM, and after normalization treatment, the peak area is greatly reduced compared with that of the isocyanate group (-N = C = O) in pIEM which is also prepared by an initiated chemical vapor deposition method. Meanwhile, p (IEM-co-HEA) is at 1550cm^-1And 1667cm^-1The flexural vibration absorption peaks of-NH and-CO-appeared, indicating that the ureido functional group (-NHCO-) was formed. And the peak area is large, which represents that the urea-based resin has a large urea-based content and has a large crosslinking density.

Tests show that the electrochemical corrosion inhibition rate of the organic protective coating of the electronic device obtained in the example 2 on metal in 3.5% NaCl solution reaches 99.3%. The permeability to oxygen is as low as 5.8 x 10^-13 cm³ cm/cm²s cmHg, indicating that the sample has oxygen barrier effect. The photoresponse integrated circuit board after being coated with the film as shown in fig. 4 is put into water after being electrified, and can still continuously keep normal work after 72 hours in water environment.

The theoretical degree of crosslinking in example 2 was calculated to be 89%.

And the surface of the sample is flat and smooth and is tightly combined with the substrate material through SEM representation. And the samples deposited on the transparent substrate showed excellent light transmission performance, as shown in fig. 2, the transparent substrate was plated with a protective layerAfter plating, the icons behind the substrate can still be clearly seen through the plating. The samples plated on the copper sheets were electrochemically characterized as shown in fig. 3, with corrosion current from original I0=1.619 x 10-4A/cm²Reduction to I =1.17 x 10^-6 A/cm²From the formula:

inhibition% = (I0-I)/I0 = 100%,

the calculation shows that the protective coating prepared by the scheme has 99.3 percent of protective effect.

Example 3: the monomer A in the monomer composition in the example 1 is unchanged, the monomer B is propane diamine, and the monomer flow rates used in the film plating are respectively IEM 0.4 sccm, propane diamine 0.3 sccm and di-tert-butyl peroxide 0.7 sccm; the hot wire of the reaction cavity is heated to 210 ℃, the pressure of the cavity is 300 mtorr, the temperature of the substrate is 43 ℃, the deposition time is 40min, and the thickness of the coating is about 800 nm. The thickness of the coating was about 800 nm, as above, for other deposition conditions. Through tests, the prepared film has the characteristics of good light transmission and tight combination with the substrate material. The permeability to oxygen is as low as 7.5 x 10^-12 cm³ cm/cm²s cmHg. Electrochemical characterization of corrosion current from the original I on samples plated on copper sheets₀=1.619*10^-4 A/cm²Decrease to I =1.3 x 10^-5A/cm²At this time, the corrosion inhibition rate reached 92%.

Example 4: the monomer A in the monomer composition in the example 3 is unchanged, the monomer B is p-phenylenediamine, and the monomer flow rates used in the film plating are respectively IEM 0.4 sccm, p-phenylenediamine 0.3 sccm and di-tert-butyl peroxide 0.7 sccm; the preparation conditions were the same as in example 3. Through the above tests, the prepared film has the characteristics of good light transmittance and tight combination with the substrate material as in example 3 due to the superiority of the initiated chemical vapor deposition technique. The permeability to oxygen is as low as 1.2X 10^-12 cm³cm/cm²s cmHg. Electrochemical characterization of corrosion current from the original I on samples plated on copper sheets₀=1.619*10^-4 A/cm²Reduction to I =3.2 x 10^-6 A/cm²At this time, the corrosion inhibition ratio reached 98%, which is due to the benzene ring junction in the monomer B usedThe structure increases the rigidity of the molecular chain and reduces the movement of the molecular chain.

Comparative example 1:

the monomer A in example 2 was replaced with Ethylene Glycol Diacrylate (EGDA), the monomer B was still HEA, and the monomer A, the monomer B and the initiator were used for deposition at flow rates of 0.4 sccm, 0.3 sccm and 0.7 sccm, respectively; the process is the same as above, the gasified monomer is introduced into the vacuumized cavity, the hot wire is heated to 210 ℃, the cavity pressure is adjusted to 300 mtorr, the substrate temperature is 38 ℃, and the coating with the thickness of 800 nm is prepared. Compared with the film prepared in example 2, the electrochemical corrosion inhibition rate of the metal in 3.5% NaCl solution is 65%, and the transmission rate of the metal to oxygen is as low as 7.1X 10^-10 cm³ cm/cm²s cmHg. This comparative example shows the necessity of reacting the isocyanate group in ethyl isocyanate acrylate with the amino group in 1, 6-hexanediamine for the densification of the polymer film and the improvement of the protective effect.

Comparative example 2:

if only the monomer A in example 1 is used, the flow rates of the monomer A and the initiator used in the deposition are respectively 0.4 sccm and 0.4 sccm; the process is the same as above, the gasified monomer is introduced into the vacuumized cavity, the hot wire is heated to 210 ℃, the cavity pressure is adjusted to 150 mtorr, the substrate temperature is 42 ℃, and the coating with the thickness of 800 nm is prepared. Then, the prepared plating layer is subjected to vacuum moisture annealing treatment, the annealing environment temperature is 80 ℃, the vacuum degree is less than 0.1MPa, the annealing time is 24h, and other preparation conditions are the same as those of comparative example 1. The electrochemical corrosion inhibition of a metal with a degree of crosslinking of 70% in a 3.5% NaCl solution was 75%, as compared to the film prepared in example 1. The permeability to oxygen is as low as 5.8 x 10^-10 cm³ cm/cm² s cmHg。

Comparative example 3:

the monomer A in example 2 is IEM, the monomer B is 4-aminostyrene, and the monomer A, the monomer B and the initiator are used for deposition at flow rates of 0.4 sccm, 0.3 sccm and 0.7 sccm, respectively; the process is the same as above, the gasified monomer is introduced into the vacuumized cavity, the hot wire is heated to 210 ℃, the cavity pressure is adjusted to 300 mtorr, the substrate temperature is 38 ℃, and the coating with the thickness of 800 nm is prepared. Gold (Au)The electrochemical corrosion inhibition rate in 3.5% NaCl solution is 85%, and the transmission rate to oxygen is as low as 2.1X 10^-10 cm³ cm/cm² s cmHg。

In comparative example 1, the necessity of containing an isocyanate group was further confirmed by embodying the monomer A of the present invention by replacing the monomer A with ethylene glycol diacrylate.

In comparative example 2, only the monomer IEM containing isocyanate groups was used, and the degree of crosslinking was significantly lower than in example 1.

By comparison, it can be found that: since the monomer A contains an ethylenic double bond and an isocyanate group and the diamine group in the monomer B forms a urea group, it is necessary to increase the degree of crosslinking of the polymer.

In comparative example 3, 4-aminostyrene containing an ethylenic double bond is used, the double bond having chain-forming properties and entering into the main chain in the polymer. In the embodiment, the monomer with the end group of amino is used for carrying out polycondensation reaction by utilizing the high reactivity of aminoisocyanate group, and does not enter the main chain of the polymer, thereby achieving higher crosslinking degree and fixing the chain segment of the polymer.

The test method comprises the following steps:

the oxygen transmission rate is tested, and the oxygen transmission rate is tested,

oxygen transmission test using a differential pressure gas permeameter (VAC-V2): the sample plated on the PS film was placed tightly between the upper and lower test chambers. Firstly, vacuumizing a low-pressure cavity (lower cavity), closing the testing lower cavity when the pressure is pumped to 10 mTorr, and filling oxygen with certain pressure into a high-pressure cavity (upper cavity) to ensure that a constant pressure difference is formed on two sides of a sample; and (3) permeating the gas from the high-pressure side to the low-pressure side under the action of the pressure difference gradient, and monitoring the internal pressure of the low-pressure side, so that parameters such as the permeation quantity, the permeation coefficient and the like of the gas are obtained.

Because dense polymer and coating composite layers are used, diffusive gas transport on the structure depends on the coating and the substrate.

，

Wherein the content of the first and second substances,

p is the total apparent permeability of the structure,

l is the total thickness ls + lc,

p s is the permeability in the substrate(s),

pc is the permeability in the coating (c).

Electrochemical testing:

electrochemical corrosion testing was performed using a three-electrode (CHI 660E) electrochemical workstation consisting of a working electrode (brass, length by width =1cm by 2 cm), a Saturated Calomel Electrode (SCE) reference electrode and a Pt plate counter electrode. Potentiodynamic polarization curves (Tafel) start from an open circuit potential, with a potential of-250 mV to + 250 mV, and samples are measured at a scan rate of 0.5 mV/s.

For purposes of explanation, specific nomenclature is used in the above description to provide a thorough understanding of the described embodiments. It will be apparent to those skilled in the art that certain modifications, combinations, and variations can be made in light of the above teachings.