【作者】 潘科学；

【导师】 曾幸荣；

【作者基本信息】 华南理工大学 ， 材料学， 2014， 博士

【摘要】 在电子工业领域，为了提高电子元器件的稳定性，经常需要对电子组装部件进行灌封。加成型有机硅灌封胶由于具有优异的电绝缘性能、耐高温性能和耐老化性能，良好的化学稳定性，加工工艺简便等优点，因而发展前景广泛。但普通的有机硅灌封胶存在热导率低、阻燃性能和粘接性能差等缺点，严重影响了其应用范围。通过大量添加导热填料、阻燃剂和粘接促进剂虽然可以改善灌封胶的这些性能，但又会对灌封胶的力学性能、加工性能等产生不利影响。本论文合成了具有增粘作用的新型交联剂和粘接促进剂，并对它们的结构进行了表征。通过选用合适的基础聚合物、导热填料和阻燃剂等，制备了具有良好导热性能、阻燃性能以及粘接性能的加成型有机硅灌封胶。主要研究内容和结果包括：第一，以不同粘度端乙烯基硅油复配，含氢硅油为交联剂，氧化铝（Al2O3）、硅微粉（SP）和碳化硅（SiC）为导热填料，制备了绝缘导热加成型有机硅灌封胶，研究了不同粘度端乙烯基硅油的质量比、含氢硅油的活性氢含量、硅氢基（SiH）与硅乙烯基（SiVi）的摩尔比、导热填料的种类和用量等对有机硅灌封胶性能的影响。当选用粘度为300mPa·s和1000mPa·s的端乙烯基硅油以质量比40:60复配，活性氢含量为0.50wt%的含氢硅油且SiH与SiVi的摩尔比为1.2时，有机硅灌封胶的力学性能较佳。填充SP和SiC有机硅灌封胶的力学性能较好，但填充Al2O3体系的粘度较低，更适合灌封工艺。当Al2O3的用量为150phr时，有机硅灌封胶具有良好的综合性能。第二，通过3-甲基丙烯酰氧基丙基甲基二甲氧基硅烷（MPMS）的水解反应与八甲基环四硅氧烷（D4）和四甲基环四硅氧烷（DH4）的开环聚合反应合成了一种具有增粘作用的新型含丙烯酸酯基的聚甲基氢硅氧烷（MPMS-PHMS）交联剂，采用傅立叶变换红外光谱（FT-IR）、核磁共振氢谱（1H-NMR）、核磁共振硅谱（29Si-NMR）和凝胶渗透色谱（GPC）对其化学结构进行了表征。研究了MPMS-PHMS的用量以及固化条件对有机硅灌封胶性能的影响。发现以MPMS-PHMS为交联剂的有机硅灌封胶具有较高的交联密度。与普通的含氢硅油（PHMS）交联剂相比，MPMS-PHMS能更有效的改善灌封胶的粘接性能和力学性能。升高固化温度和延长固化时间可以提高灌封胶的剪切强度。MPMS-PHMS的合适用量为10phr，适宜的固化温度和固化时间分别为130~150°C和2h。第三，通过醚交换反应合成了(3-环氧丙氧基丙基)烯丙氧基二甲氧基硅烷（GAMS）、[2,2-双(烯丙氧基甲基)丁氧基](3-环氧丙氧基丙基)二甲氧基硅烷（AGMS）和[3-烯丙氧基-2,2-双(烯丙氧基甲基)丙氧基](3-环氧丙氧基丙基)二甲氧基硅烷（AAGMS）三种含乙烯基和环氧基的硅烷化合物粘接促进剂，采用FT-IR和1H-NMR对它们的结构进行了表征。详细研究了粘接促进剂对有机硅灌封胶性能的影响，考察了灌封胶的耐热老化和耐水性能，并探讨了灌封胶的粘接机理。发现GAMS、AGMS和AAGMS不但可以显著改善灌封胶的粘接强度，还可以有效提高灌封胶的力学性能。其中，含有较多C=C双键和醚键的AAGMS效果最好。粘接促进剂改善了填料粒子在硅橡胶基体中的分散性以及填料和基体的结合。X-射线光电子能谱（XPS）分析结果表明AAGMS可以迁移到粘接界面起增粘作用。当AAGMS的用量为1.5phr时，有机硅灌封胶的综合性能较好，剪切强度和拉伸强度分别为1.14MPa和3.27MPa，比未加粘接促进剂时分别提高了235%和47%，而且具有良好的耐热老化性能和耐水性能。第四，通过三羟甲基丙烷单烯丙基醚（TMPME）分别与3-环氧丙氧基丙基甲基二甲氧基硅烷（GPMMS）和3-环氧丙氧基丙基甲基二乙氧基硅烷（GPMES）反应合成了两种含乙烯基和环氧基的硅烷低聚物（PTGM和PTGE）粘接促进剂，采用FT-IR、1H-NMR和GPC对PTGM和PTGE的结构进行了表征。研究了PTGM和PTGE对灌封胶粘接性能、力学性能和粘度的影响，考察了灌封胶的耐热老化和耐水性能。结果表明PTGM和PTGE均可以提高灌封胶的粘接性能和力学性能。与PTGE相比，加入PTGM灌封胶的综合性能更好。第五，在以Al2O3为导热填料的有机硅灌封胶中加入AAGMS和阻燃剂氢氧化铝（Al(OH)3），制备了自粘性无卤阻燃导热加成型有机硅灌封胶，研究了Al(OH)3的粒径和用量以及AAGMS的用量对灌封胶阻燃性能、粘接性能、导热性能、力学性能和粘度的影响。发现AAGMS可以提高灌封胶的粘接性能、导热性能和力学性能，但会增加灌封胶的粘度。扫描电镜（SEM）结果表明AAGMS改善了Al2O3和Al(OH)3在硅橡胶基体中的分散性以及填料和基体的结合。与小粒径Al(OH)3相比，用大粒径Al(OH)3制备灌封胶的流动性较好，更有利于灌封。当AAGMS用量为1.5phr，Al(OH)3的粒径为20μm以及用量为60phr时，灌封胶具有较好的综合性能，热导率为0.583W·m-1·K-1，剪切强度为1.31MPa，拉伸强度为3.43MPa，断裂伸长率为52%，粘度为7200mPa·s，垂直燃烧级别为UL-94V-0级。更多还原

【Abstract】 In electronics industry, in order to improve the stability of the electronic devices, it isoften necessary to encapsulate the electronic assembly components. Addition-cure siliconeencapsulant has broad development prospects due to its excellent electrical insulationproperty, resistance to high temperature and aging resistant performance, good chemicalstability, easy processing, etc. However, common silicone encapsulant had somedisadvantages such as low thermal conductivity, poor flame retardancy and adhesionproperties, which seriously limited its application. To improve these properties of encapsulant,a large amount of thermally conductive fillers, flame retardants and adhesion promoters wereadded, which has a negative effect on the mechanical properties and processability, etc. Inthis dissertation, a novel adhesion-enhancing cross-linker and several types of adhesionpromoters were synthesized, and their structures were characterized. Addition-cure siliconeencapsulant with good thermal conductivity, flame retardancy and adhesion properties wasprepared through selecting appropriate base polymer, thermally conductive filler and flameretardant, etc. The main research contents and results are listed as following:Firstly, electrical insulating and thermal conductive addition-cure silicone encapsulantwas prepared using complex of vinyl end silicone oils with different viscosities, hydrogensilicone oil as cross-linker, alumina (Al2O3), silica power (SP) and silicon carbide (SiC) asthermally conductive fillers. The effect of mass ratio of vinyl end silicone oils, hydridecontent of hydrogen silicone oil, molar ratio of hydrosilyl (SiH) and vinylsilyl (SiVi), typeand content of thermally conductive fillers on the properties of silicone encapsulant wereinvestigated. When mass ratio of vinyl end silicone oil with viscosity of300mPa·s and1000mPa·s was40:60, hydride content of hydrogen silicone oil was0.50wt%and molar ratioof SiH and SiVi was1.2, silicone encapsulant had good mechanical properties. Theencapsulant filled with SP and SiC had better mechanical properties, but the encapsulant withAl2O3had lower viscosity so that it was more suitable for encapsulating process. When thecontent of Al2O3was150phr, silicone encapsulant had good comprehensive performance.Secondly, a novel adhesion-enhancing polyhydrosiloxane containing acrylate groups (MPMS-PHMS) as cross-linker was synthesized by the hydrolysis ofmethacryloyloxypropylmethyldimethoxysilane (MPMS) and the ring opening polymerizationof octamethylcyclotetrasiloxane (D4) and tetramethylcyclotetrasiloxane (DH4). Fouriertransform infrared (FT-IR) spectroscopy,1H nuclear magnetic resonance (1H-NMR)spectroscopy,29Si nuclear magnetic resonance (29Si-NMR) spectroscopy and gel permeationchromatography (GPC) were used to characterize its chemical structure. The effect ofMPMS-PHMS content and cure conditions on the properties of silicone encapsulant wereinvestigated. It was found that silicone encapsulant had higher cross-linking density whenusing MPMS-PHMS as cross-linker. Compared with commercial hydrogen silicone oil(PHMS) cross-linker, MPMS-PHMS could markedly improve both the adhesion strength andmechanical properties of the encapsulant. Appropriately increasing cure temperature andprolonging cure time were favorable to enhance the shear strength of the encapsulant. Theoptimal content of MPMS-PHMS was10phr, and the suitable cure temperature and time were130~150°C and2h, respectively.Thirdly, three types of silanes containing vinyl and epoxy group,(3-glycidoxypropyl)allyloxydimethoxysilane (GAMS),[2,2-bis (allyloxymethyl) butoxy](3-glycidoxypropyl)dimethoxysilane (AGMS) and [3-allyloxy-2,2-bis (allyloxymethyl) propoxy](3-glycidoxypropyl) dimethoxysilane (AAGMS), were synthesized by the transetherificationand used as adhesion promoters. The chemical structures were characterized by FT-IR and1H-NMR. The influence of adhesion promoters on the properties of silicone encapsulant wasinvestigated in detail, heat aging resistance and water resistance of the encapsulant werestudied, and the adhesion mechanism of the encapsulant was explored. It was found thatGAMS, AGMS and AAGMS could not only greatly improve the adhesion strength of theencapsulant but also significantly enhance the mechanical properties of the encapsulant.Among them, AAGMS with more C=C bonds and ether bonds gave the best adhesionstrength and mechanical properties of the encapsulant. The adhesion promoter improved thedispersibility of filler particles in silicone rubber matrix and enhance the bond between fillerand matrix. X-ray photoelectron spectroscopy (XPS) result showed that AAGMS couldmigrate to the bonding interface and produce the adhesion-enhancing effect. When thecontent of AAGMS was1.5phr, silicone encapsulant had good comprehensive performance. The shear strength and tensile strength of the encapsulant were1.14MPa and3.27MPa, whichwas about235%and47%higher than that of the encapsulant without adhesion promoter,respectively. The encapsulant with AAGMS had good heat aging resistance and waterresistance.Fourthly, two types of silane oligomers containing vinyl and epoxy group (PTGM andPTGE) as adhesion promoters were synthesized by the reaction of trimethylolpropanemonoallyl ether (TMPME) with3-glycidoxypropylmethyldimethoxysilane (GPMMS) and3-glycidoxypropylmethyldiethoxysilane (GPMES), respectively. FT-IR,1H-NMR and GPCwere used to characterize their chemical structures. The effect of PTGM and PTGE on theadhesion properties, mechanical properties and viscosity of the encapsulant were investigated,and heat aging resistance and water resistance of the encapsulant were studied. The resultsshowed that PTGM and PTGE could enhance both the adhesion strength and mechanicalproperties of the encapsulant. Compared with PTGE, the encapsulant with PTGM had bettercomprehensive performance.Finally, self-adhesive, halogen-free flame retardant and thermal conductiveaddition-cure silicone encapsulant was prepared by adding AAGMS and aluminiumhydroxide (Al(OH)3) to silicone encapsulant with Al2O3as thermal conductive filler. Theeffect of particle size and content of Al(OH)3and AAGMS content on the flame retardancy,adhesion properties, thermal conductivity, mechanical properties and viscosity of theencapsulant were investigated. It was found that AAGMS could enhance adhesion properties,thermal conductivity and mechanical properties of the encapsulant, but its viscosity increased.Scanning electron microscopy (SEM) showed that AAGMS could improve the dispersibilityof Al2O3and Al(OH)3particles in silicone rubber matrix and enhance the bond between fillerand matrix. Compared with small particle size of Al(OH)3, the encapsulant filled with largeparticle size of Al(OH)3had good flowability, which was beneficial for encapsulating process.When the content of AAGMS was1.5phr, and the particle size and content of Al(OH)3were20μm and60phr, the encapsulant possessed good comprehensive performance. The thermalconductivity was0.583W·m-1·K-1, the shear strength was1.31MPa, the tensile strength was3.43MPa, the elongation at break was52%, the viscosity was7200mPa·s, and the verticalburning test achieved a UL-94V-0rating.更多还原