A packaging material and a preparation method and application thereof

Abstract

The application discloses a packaging material and a preparation method and application thereof. The packaging material comprises the following components in parts by mass: 40-85 parts of a base resin, 5-30 parts of phase change PCM particles, 3-20 parts of self-repairing microcapsules, 1-8 parts of an interfacial compatibilizer, and 10-20 parts of a heat conduction network reinforcing material. The melting point of the phase change PCM particles is less than or equal to 80 DEG C. The core layer of the self-repairing microcapsules comprises dicyclopentadiene and a ruthenium-based catalyst, and the shell layer comprises polyurea or polyurethane. The application combines low-melting-point phase change PCM particles with a self-repairing microcapsule system to form a PCBA packaging material with an intelligent response function. When the temperature of the PCBA is too high, the low-melting-point phase change PCM particles melt, melt heat absorption is used to inhibit the temperature from rising too fast, and volume expansion is used to trigger the rupture of adjacent microcapsules, release DCPD monomers and in-situ polymerization under the action of a catalyst, rapidly repair microcracks caused by thermal stress, and significantly improve the heat dissipation stability and electrical insulation reliability of the material in long-term thermal cycling.

Description

Technical Field

[0001] This invention relates to the field of PCBA packaging technology, and in particular to a packaging material, its preparation method, and its application. Background Technology

[0002] With the rapid development of high-power-density electronic devices, the localized heat generated by PCBA chips during operation has increased dramatically. Traditional polymer packaging materials, due to their poor thermal conductivity and mismatched coefficients of thermal expansion, are prone to developing microcracks during thermal cycling. These cracks not only compromise the mechanical integrity of the package but also significantly increase thermal resistance, leading to decreased heat dissipation efficiency and further exacerbating chip temperature rise. This creates a vicious cycle of "overheating, cracking, and even more severe overheating," severely impacting device reliability and lifespan.

[0003] To alleviate the above problems, existing technologies attempt to improve the overall thermal conductivity by introducing high thermal conductivity fillers (such as boron nitride, carbon nanotubes, etc.) into the encapsulation material. However, simply enhancing thermal conductivity can only slow down the rate of temperature rise and cannot fundamentally eliminate microcracks caused by thermal stress. Moreover, once the material cracks due to temperature rise, the heat dissipation performance will irreversibly degrade.

[0004] Therefore, a technical solution is needed to address the reliability degradation problem caused by the synergistic deterioration of local overheating and microcracks during long-term PCBA operation. Summary of the Invention

[0005] In view of this, this application provides a packaging material, its preparation method and application, to solve the problem of reliability decline caused by the synergistic deterioration of local overheating and microcracks during long-term operation of PCBA.

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides an encapsulation material comprising the following components in parts by weight: 40-85 parts matrix resin, 5-30 parts phase change PCM particles, 3-20 parts self-healing microcapsules, 1-8 parts interface compatibilizer, and 10-20 parts thermally conductive network reinforcing material; the phase change PCM particles have a melting point ≤80°C; the core layer of the self-healing microcapsules comprises dicyclopentadiene and a ruthenium-based catalyst, and the shell layer comprises polyurea or polyurethane.

[0008] Preferably, the phase change PCM particles have a core-shell structure, with the core being a mixture of n-eicosane and expanded graphite in a mass ratio of 5-12:1, and the shell being porous SiO2.

[0009] Preferably, the surface of the self-healing microcapsules is modified with hexadecyltrimethylammonium bromide, and the SiO2 shell of the PCM particles is loaded with sulfonic acid groups.

[0010] Preferably, the interface compatibilizer includes silane coupling agent KH-560, the thermally conductive network reinforcement material includes boron nitride nanosheets, the ruthenium-based catalyst includes triphenylphosphine ruthenium chloride, and the matrix resin is ALSR.

[0011] Secondly, this application provides a method for preparing an encapsulation material, comprising the following steps: mixing a matrix resin, PCM particles, self-healing microcapsules, an interface compatibilizer, and a thermally conductive network reinforcing material, shearing and dispersing them, then degassing them under vacuum, coating them onto a PCBA chip, and curing them to obtain the encapsulation material.

[0012] Preferably, the mixing temperature is less than or equal to 35°C.

[0013] Preferably, the preparation method of phase change PCM particles includes: mixing molten n-eicosane with expanded graphite, ultrasonically dispersing and then cooling and solidifying, then coating the core surface with a porous SiO2 shell by the sol-gel method, and then sulfonating to obtain phase change PCM particles.

[0014] Preferably, the preparation method of self-healing microcapsules includes: using dicyclopentadiene and ruthenium-based catalyst as core materials, forming a polyurea shell through interfacial polymerization, and then immersing it in CTAB aqueous solution, heating and stirring to obtain self-healing microcapsules.

[0015] Preferably, the shearing and dispersion method is a three-roll milling process.

[0016] Thirdly, this application provides an application of a packaging material in PCBA packaging.

[0017] The beneficial effects of this application are as follows:

[0018] This application combines low-melting-point phase change PCM particles with a self-healing microcapsule system to form a PCBA packaging material with intelligent response function. When the PCBA temperature is too high, the low-melting-point phase change PCM particles melt, suppressing the junction temperature surge through melting and heat absorption. At the same time, the volume expansion triggers the rupture of adjacent microcapsules, releasing DCPD monomers, which then polymerize in situ under the action of a catalyst, quickly repairing microcracks caused by thermal stress. Without external intervention, this significantly improves the heat dissipation stability and electrical insulation reliability of the material during long-term thermal cycling, providing a smart packaging foundation for high-power-density electronic devices that combines high reliability and long life. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] This application provides an encapsulation material comprising the following components in parts by weight: 40-85 parts matrix resin, 5-30 parts phase change PCM particles, 3-20 parts self-healing microcapsules, 1-8 parts interface compatibilizer, and 10-20 parts thermally conductive network reinforcing material; the phase change PCM particles have a melting point ≤80℃; the core layer of the self-healing microcapsules comprises dicyclopentadiene and a ruthenium-based catalyst, and the shell layer comprises polyurea or polyurethane.

[0021] This application addresses the technical problem of decreased reliability in PCBAs due to the synergistic deterioration of localized overheating and microcracks during long-term operation by combining phase change PCM particles with self-healing microcapsules. The mechanism is as follows:

[0022] When the PCBA operating temperature exceeds 80°C, the PCM particles melt and expand in volume, directionally compressing the shell of the adjacent microcapsules and triggering their rupture. The dicyclopentadiene released by the ruptured microcapsules undergoes ring-opening metathesis polymerization under the action of a ruthenium catalyst, instantly repairing the cracks in the encapsulation layer and preventing the PCBA from overheating. However, this leads to cracks, heat dissipation failure, and a vicious cycle of more severe overheating.

[0023] The interface compatibilizer in this application enhances the interfacial bonding force between PCM particles, microcapsules and matrix resin, and prevents interface debonding caused by phase transformation stress; the thermally conductive network reinforcing material constructs a three-dimensional thermally conductive pathway, improves the basic heat dissipation capacity, and makes up for the thermal management shortcomings when the PCM is not activated.

[0024] In some embodiments, the phase change PCM particles have a core-shell structure, with the core being a mixture of n-eicosane and expanded graphite in a mass ratio of 5-12:1, and the shell being porous SiO2.

[0025] In this embodiment, the melting temperature of the phase change PCM particles can be maintained at 36-40°C because the inherent melting point of n-eicosane is 36.7°C. Expanded graphite only acts as a volume expansion enhancer without changing the phase change temperature. It is worth noting that although the melting point of PCM is 36-40°C, due to thermal hysteresis and local hot spots within the package, volume expansion and the triggering of the repair mechanism actually occur only when the chip operating temperature is >80°C. At the same time, due to the addition of expanded graphite, its expansion rate is increased, which is beneficial to enhance the mechanical compressive stress on the microcapsule shell, realize the release of dicyclopentadiene, and thus perform self-repair of cracks.

[0026] In some embodiments, the surface of the self-healing microcapsules is modified with hexadecyltrimethylammonium bromide, and the SiO2 shell of the PCM particles is loaded with sulfonic acid groups.

[0027] In this embodiment, by modifying the surfaces of the self-healing microcapsules and PCM particles respectively, electrostatic adsorption between the two is achieved, CTAB + With -SO3H -Ionic bonds are formed between them, which enhances their compatibility and dispersibility, and helps to shorten the average distance between PCM and microcapsules, thereby ensuring that stress is transferred to microcapsules when PCM melts and expands.

[0028] In some embodiments, the interface compatibilizer includes silane coupling agent KH-560, the thermally conductive network reinforcement material includes boron nitride nanosheets, the ruthenium-based catalyst includes triphenylphosphine ruthenium chloride, and the matrix resin is ALSR.

[0029] In this embodiment, the matrix resin is ALSR, which has the advantage of high elongation at break, allowing it to accommodate the volume expansion of PCM phase change without cracking; the role of the ruthenium-based catalyst is to catalyze the ring-opening polymerization of dicyclopentadiene, thereby achieving self-healing.

[0030] This application provides a method for preparing an encapsulation material, comprising the following steps: mixing a matrix resin, PCM particles, self-healing microcapsules, an interface compatibilizer, and a thermally conductive network reinforcing material, shearing and dispersing the mixture, then vacuum degassing, coating the mixture onto a PCBA chip, and curing it to obtain the encapsulation material.

[0031] In some embodiments, the mixing temperature is less than or equal to 35°C.

[0032] In this embodiment, if the mixing temperature is too high, the PCM will melt and agglomerate prematurely, damaging the integrity of the core-shell structure; at the same time, it will trigger the pre-activation of the ruthenium-based catalyst, reducing the activity of the repair reaction.

[0033] In some embodiments, the preparation method of phase change PCM particles includes: mixing molten n-eicosane with expanded graphite, ultrasonically dispersing and then cooling and solidifying, then coating the core surface with a porous SiO2 shell by a sol-gel method, and then sulfonating to obtain phase change PCM particles.

[0034] In this embodiment, the preparation method of phase change PCM particles is as follows:

[0035] 50g of n-eicosane was heated to 60℃ to melt, and 5g of expanded graphite was added and ultrasonically dispersed. The mixture was then cooled and pulverized to a particle size of 30μm, dispersed in an ethanol / water solution (4:1), and 20g of tetraethyl orthosilicate and 40mL of ammonia were added dropwise. The mixture was reacted at 40℃ for 6h to form a porous SiO2 coating layer. Finally, concentrated sulfuric acid was used for sulfonation at 60℃ for 2h to introduce -SO3H groups. This method successfully yielded phase change PCM particles with high volume expansion and surface sulfonation activity through a sol-gel hydrolysis-condensation reaction mechanism.

[0036] In some embodiments, the preparation method of self-healing microcapsules includes: using dicyclopentadiene and a ruthenium-based catalyst as core materials, forming a polyurea shell through interfacial polymerization, and then immersing it in a CTAB aqueous solution, heating and stirring to obtain self-healing microcapsules.

[0037] In this embodiment, the preparation method of the self-healing microcapsules is as follows:

[0038] 10g MDI and 15g DCPD were mixed, and 0.5g triphenylphosphine ruthenium chloride catalyst was added and dissolved in 20g xylene as the oil phase. 2g polyetheramine D230 was dissolved in 100mL deionized water as the aqueous phase. Under stirring, the oil phase was slowly added dropwise to the aqueous phase, followed by emulsification at 2000 rpm for 10 minutes to form a stable emulsion. The temperature was raised to 60℃, and the reaction was continuously stirred for 2 hours to induce a polycondensation reaction between MDI and D230 at the oil-water interface, forming a polyurea shell. After the reaction, the microcapsules were collected by centrifugation, washed, and dispersed in a 5% CTAB solution. The surface was modified by stirring at 60℃ for 2 hours, followed by washing and drying to obtain self-healing microcapsules. Through the reaction mechanism of interfacial polymerization, self-healing microcapsules with directional electrostatic adsorption capacity and low fracture strength were successfully obtained. The polyurea shell, formed by copolymerization of MDI and polyetheramine D230, has a low glass transition temperature and high flexibility, and is easily broken under external force to release the core material.

[0039] In some embodiments, the shearing dispersion is performed using a three-roll milling process.

[0040] In this embodiment, the parameters of the three-roll milling process are a roller spacing of 0.3 mm and a roller speed ratio of 1:3:9 (20 / 60 / 180 rpm). Under these conditions, it is advantageous to apply a shear force of 12 MPa, which is higher than the PCM agglomerate breakage threshold (5 MPa) but lower than the rupture strength of the microcapsules prepared above (20 MPa), thus achieving the effect of further dispersing PCM and low microcapsule breakage rate.

[0041] This application provides an application of a packaging material in PCBA packaging.

[0042] The encapsulation material of this application is used in high-power chips and stress concentration areas of solder joints in PCBA. When the operating temperature is >80°C, the PCM near the chip melts and expands first. The microcapsules connected by electrostatic bridging rupture, and the released DCPD quickly completes the polymerization reaction, repairs the cracks, and restores the insulation and heat dissipation function of the encapsulation layer.

[0043] The following specific embodiments further illustrate this solution.

[0044] Raw material source:

[0045] ALSR, Shin-Etsu KE-2090, viscosity 3500 mPa·s;

[0046] n-Eicosane, Aladdin, melting point 36.7℃;

[0047] Expanded graphite, Mindray Chemical EG-290, expansion rate 300mL / g;

[0048] Dicyclopentadiene (DCPD), Aladdin;

[0049] Triphenylphosphine ruthenium chloride, Energi;

[0050] Diphenylmethane diisocyanate (MDI), Wanhua Chemical;

[0051] KH-560 silane coupling agent, Nanjing Nengde;

[0052] Boron nitride nanosheets, Mindray MR-DS306, aspect ratio > 120;

[0053] Hexadecyltrimethylammonium bromide (CTAB), Sinopharm Group.

[0054] PCM Particle 1: 50g of n-eicosane was heated to 60℃ to melt, 5g of expanded graphite was added, and the mixture was ultrasonically dispersed at 500W for 30 minutes. After cooling to 25℃ to solidify, the particles were pulverized and sieved. The sieved particles were dispersed in 200mL of ethanol / water mixture (volume ratio 4:1), 20g of TEOS and 40mL of 25wt% ammonia were added dropwise, and the mixture was magnetically stirred at 40℃ for 6 hours. After centrifugation and washing at 8000 rpm, the particles were dried at 80℃ for 12 hours. Then, the dried particles were immersed in 100mL of 98wt% concentrated sulfuric acid, stirred at 60℃ for 2 hours, and then neutralized and washed until pH=7 to obtain PCM Particle 1.

[0055] PCM Particles 2: The rest is the same as PCM Particles 1, except that it does not include the step of immersing the dried particles in 100 mL of 98 wt% concentrated sulfuric acid, stirring at 60°C for 2 hours, and then neutralizing and washing until pH=7.

[0056] PCM Particle 3: The rest is the same as PCM Particle 1, except that it does not include the addition of expanded graphite.

[0057] PCM Particle 4: The rest is the same as PCM Particle 1, except that n-eicosane is replaced with n-tetradecane.

[0058] Self-healing microcapsules 1: 10g MDI and 15g DCPD were mixed, and 0.5g triphenylphosphine ruthenium chloride catalyst was added and dissolved in 20g xylene as the oil phase; 2g polyetheramine D230 was dissolved in 100mL deionized water as the aqueous phase; under stirring conditions, the oil phase was slowly added dropwise to the aqueous phase, and then emulsified at 2000 rpm for 10 minutes to form a stable emulsion; the temperature was raised to 60℃ and the reaction was continuously stirred for 2 hours to allow MDI and D230 to undergo a condensation reaction at the oil-water interface to form a polyurea shell; after the reaction was completed, the microcapsules were collected by centrifugation, washed, and dispersed in 5% CTAB solution, stirred at 60℃ for 2 hours for surface modification, and then washed and dried to obtain self-healing microcapsules 1.

[0059] Self-healing microcapsules 2: The rest of the contents are the same as those of self-healing microcapsules 1, except that the steps of immersing the microcapsules in a 5% CTAB aqueous solution, stirring at 60°C for 2 hours, and drying for later use are not included.

[0060] Self-healing microcapsules 3: The rest of the contents are the same as self-healing microcapsules 1, except that DCPD is replaced with paraffin oil.

[0061] Self-healing microcapsules 4: The rest of the contents are the same as those of self-healing microcapsules 1. The difference is that 2g of polyetheramine D230 is dissolved in 100mL of 37wt% formaldehyde aqueous solution with a pH of 8.5 to obtain microcapsules 4 with a high hardness melamine-formaldehyde shell. Example 1

[0062] An encapsulation material comprising the following components in parts by weight: 70 parts ALSR matrix resin, 10 parts phase change PCM particles, 8 parts self-healing microcapsules, 5 parts KH-560 silane coupling agent, and 15 parts boron nitride nanosheets.

[0063] The preparation method of the encapsulation material includes the following steps: ALSR, KH-560, and boron nitride are stirred at 35°C and 500 rpm for 10 min. PCM particles 1 are added and subjected to three-roll milling with a roller gap of 0.3 mm and roller speeds of 20 / 60 / 180 rpm for 3 cycles. Then, self-healing microcapsules 1 are added and stirred at 100 rpm for 5 min. After degassing under -0.1 MPa vacuum for 10 min, the material is applied to the PCBA chip and cured at 80°C for 2 h to obtain the encapsulation material. Example 2

[0064] An encapsulation material, otherwise identical to that in Example 1, except that phase change PCM particles 1 are replaced with phase change PCM particles 2. Example 3

[0065] An encapsulation material, otherwise identical to that in Example 1, except that phase change PCM particles 1 are replaced with phase change PCM particles 3. Example 4

[0066] An encapsulation material, otherwise identical to that in Example 1, except that self-healing microcapsule 1 is replaced with self-healing microcapsule 2. Example 5

[0067] An encapsulation material, otherwise identical to that in Example 1, except that the ALSR matrix resin is replaced with epoxy resin. Example 6

[0068] An encapsulation material, otherwise identical to that in Example 1, except that it does not include the three-roll milling step.

[0069] Comparative Example 1

[0070] An encapsulation material, otherwise identical to that in Example 1, except that phase change PCM particles 1 are replaced with phase change PCM particles 4.

[0071] Comparative Example 2

[0072] An encapsulation material, otherwise identical to that in Example 1, except that self-healing microcapsules 1 are replaced with self-healing microcapsules 3.

[0073] Comparative Example 3

[0074] An encapsulation material, otherwise identical to that in Example 1, except that self-healing microcapsules 1 are replaced with self-healing microcapsules 4.

[0075] Comparative Example 4

[0076] An encapsulation material, otherwise identical to that in Example 1, except that it does not include the self-healing microcapsule 1.

[0077] Comparative Example 5

[0078] An encapsulation material, otherwise identical to that in Example 1, except that phase change PCM particles 1 are replaced with expanded graphite.

[0079] Testing and Evaluation

[0080] 1. Repair efficiency

[0081] Artificial cracks were pre-formed on the surface of the encapsulation materials obtained in different embodiments and comparative examples. The crack width was 50 μm and the depth was 200 μm. The samples were placed in an 85°C oven for 1 hour and cooled to 25°C. The change in crack width was measured and the repair rate was calculated: Repair rate = (1 - crack width after repair / initial crack width) × 100%. The test results are shown in Table 1.

[0082] 2. Thermal conductivity

[0083] The temperature distribution of the packaging materials (PCBA chip power of 10W) ​​obtained in different embodiments and comparative examples was recorded using an infrared thermal imager. The ambient temperature was increased from 25°C to 100°C, and the chip junction temperature was recorded. The results are shown in Table 1.

[0084] 3. Thermal circulation effect

[0085] The encapsulation materials obtained from different embodiments and comparative examples were subjected to thermal cycling from -40℃ to 125℃ according to JESD22-A104 standard, with each cycle lasting 30 minutes. Insulation resistance was measured after every 100 cycles, and records were kept for functional failures (insulation resistance < 10 ohms). 8 The number of cycles for Ω) is shown in Table 1.

[0086] Table 1 Test Results

[0087]

[0088] This application combines low-melting-point phase change PCM particles with a self-healing microcapsule system to form a PCBA packaging material with intelligent response function. When the PCBA temperature is too high, the low-melting-point phase change PCM particles melt, suppressing the junction temperature surge through melting and heat absorption. At the same time, the volume expansion triggers the rupture of adjacent microcapsules, releasing DCPD monomers, which then polymerize in situ under the action of a catalyst, quickly repairing microcracks caused by thermal stress. Without external intervention, this significantly improves the heat dissipation stability and electrical insulation reliability of the material during long-term thermal cycling, providing a smart packaging foundation for high-power-density electronic devices that combines high reliability and long life.

[0089] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An encapsulation material, characterized in that, The product comprises the following components in parts by weight: 40-85 parts matrix resin, 5-30 parts phase change PCM particles, 3-20 parts self-healing microcapsules, 1-8 parts interface compatibilizer, and 10-20 parts thermally conductive network reinforcing material; the phase change PCM particles have a melting point ≤80℃; the core layer of the self-healing microcapsules comprises dicyclopentadiene and a ruthenium-based catalyst, and the shell layer comprises polyurea or polyurethane; the preparation method of the phase change PCM particles includes: mixing molten n-eicosane with expanded graphite, ultrasonically dispersing and cooling to solidify, then coating the core surface with a porous SiO2 shell using a sol-gel method, followed by sulfonation treatment to obtain the phase change PCM particles; the preparation method of the self-healing microcapsules includes: using dicyclopentadiene and a ruthenium-based catalyst as the core material, forming a polyurea shell through interfacial polymerization, then immersing in a CTAB aqueous solution, heating and stirring to obtain the self-healing microcapsules; the thermally conductive network reinforcing material includes boron nitride nanosheets.

2. The encapsulation material according to claim 1, characterized in that, The phase change PCM particles have a core-shell structure, with the core being a mixture of n-eicosane and expanded graphite in a mass ratio of 5-12:1, and the shell being porous SiO2.

3. The encapsulation material according to claim 1, characterized in that, The surface of the self-healing microcapsule is modified with hexadecyltrimethylammonium bromide, and the SiO2 shell of the PCM particles is loaded with sulfonic acid groups.

4. The encapsulation material according to claim 1, characterized in that, The interface compatibilizer includes silane coupling agent KH-560; the ruthenium-based catalyst includes triphenylphosphine ruthenium chloride; and the matrix resin is ALSR.

5. A method for preparing an encapsulation material as described in any one of claims 1-4, characterized in that, Includes the following steps: The matrix resin, PCM particles, self-healing microcapsules, interface compatibilizer, and thermally conductive network reinforcement material are mixed, sheared and dispersed, then vacuum degassed, and finally coated onto a PCBA chip and cured to obtain the encapsulation material.

6. The preparation method according to claim 5, characterized in that, The mixing temperature is less than or equal to 35°C.

7. The preparation method according to claim 5, characterized in that, The shearing and dispersion method is a three-roll milling process.

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