Effects of the complexed moisture in metal acetylacetonate on the properties of the no‐flow underfill materials

A potential no‐flow (compression filling of encapsulant) underfill encapsulant for simultaneous solder joint reflow and underfill cure has been reported by the authors. The encapsulant is based on a cycloaliphatic epoxy/organic anhydride/Co(II) acetylacetonate system. The key of this no‐flow encapsulant is the use of a latent metal acetylacetonate catalyst that provides the solder reflow prior to the epoxy gellation and fast cure shortly after the solder reflow. However, most of the metal acetylacetonates can easily absorp moisture as their ligand. Therefore, it is of practical importance to understand the effect of the complexed water on the properties of the no‐flow material before and after cure. In this paper, differential scanning calorimetry, thermal gravimetric analysis, thermal mechanical analysis, dynamic mechanical analysis, and Fourier transform infrared spectrometry were used to validate the existence of complexed moisture in the Co(II) acetylacetonate. The effects of the complexed water on the curing profile, glass transition temperature, and storage modulus of the cured no‐flow underfill material were studied. A possible catalytic mechanism of the metal acetylacetonate in the cycloaliphatic epoxy/anhydride system was subsequently discussed and proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 103–111, 1999     

Carbon nanotube bumps for the flip chip packaging system

ABSTRACT: Carbon nanotube [CNT] interconnection bump joining methodology has been successfully demonstrated using flip chip test structures with bump pitches smaller than 150 μm. In this study, plasma-enhanced chemical vapor deposition approach is used to grow the CNT bumps onto the Au metallization lines. The CNT bumps on the die substrate are then 'inserted' into the CNT bumps on the carrier substrate to form the electrical connections (interconnection bumps) between each other. The mechanical strength and the concept of reworkable capabilities of the CNT interconnection bumps are investigated. Preliminary electrical characteristics show a linear relationship between current and voltage, suggesting that ohmic contacts are attained.     

Epoxy nanocomposites with reduced coefficient of thermal expansion

Control of the coefficient of thermal expansion (CTE) of polymeric materials is critical in many applications, particularly the electronics industry where CTE mismatches have caused failures. In theory, adding exfoliated nanoplatelets with high aspect ratios would offer an effective solution for reducing CTE, but reported results have not been compelling due to poor dispersion. In this study, α-zirconium phosphate (ZrP) nanoplatelets, along with organic surfactants, were added to epoxy thermosets. The CTE reduction and glass-transition temperature (T_g) were measured while the molecular weight of the surfactant was varied. High-molecular-weight surfactants are effective for ZrP exfoliation and dispersion, but they can also lead to a reduction in T_g and hinder the drop in CTE. A combination of two low-molecular-weight tetrabutylammonium hydroxide and 2-methoxyethylamine surfactants for exfoliation of ZrP were found to give a CTE reduction of 40% with just 3.5 vol % of ZrP added. This CTE reduction correlates well with theory. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47703.     

Influences of nanoparticle content on electrical and thermal performances of micro-nano hybrid composites for packaging materials

This paper presents electrical and thermal properties of a novel type of micro-nano hybrid composites to be potential for packaging. The micro-nano hybrid composites contain 20 wt% of micro-aluminium nitride (AlN) with 1, 3, and 5 wt% of nano-AlN, respectively. Electrical measurement and thermal analysis are used to analyze the performances. The results show that the nano-AlN in the hybrid composites can suppress the space charge accumulation near the cathode and facilitate the conversion of hetero charge into the homo-charge accumulations near the anode. No apparent electric field distortion can be observed in the M20N3 sample, whereas it exhibits a minimum electrical conductivity and highest thermal conductivity amongst all samples. Furthermore, the nano-filler addition can enhance the DC breakdown strength and the thermal stability of the hybrid composites. The thermal and electrical conduction mechanism of the micro and nano fillers in the hybrid composites is also elucidated.     

3D interconnected high aspect ratio tellurium nanowires in epoxy nanocomposites: serving as thermal conductive expressway

Heat removal via thermal management materials is attracting more and more attention in the electronic industry. Conventional particle/polymer thermal conductive composites require a high filler loading ratio (>30 vol %), which cause severe thermal interfacial resistance and mechanical issue. In this work, we fabricate tellurium nanowires (NWs)/epoxy nanocomposites via a facile bar coating method. According to Agari model and Maxwell–Eucken model, the as-synthesized ultra-long NWs with high aspect ratio (>100) construct the 3D interconnected thermal conductive network better in resin matrix to facilitate the heat transfer process. The results show that at a low loading ratio of 2.4 vol %, this nanocomposite exhibits the out-of-plane and in-plane thermal conductivity of 0.378 and 1.63 W m⁻¹ K⁻¹, respectively, which is 189 and 715% higher than that of pure epoxy resin. Importantly, good stability, and flexibility of nanocomposites are well maintained. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47054.     

Property and reliability of liquid underfill material for IC packaging

Thermoplastic nylon powder was added to naphthalene epoxy to serve as a stress release agent to reduce the stress resulting from the shrinkage during the cure of naphthalene epoxy. The purpose of this study was to explore the physical impact and effect on the forming object after adding nylon powder onto naphthalene epoxy. Mechanical properties were explored through the Izod impact test, the three‐point bending test, tensile test, and lap shear adhesion test. Thermal mechanical analysis (TMA) and dynamic mechanical analysis (DMA) were conducted to identify the coefficient of thermal expansion (CTE) and the glass transition temperature (T_g). The rate of water absorption was measured via a test of pressure cook test (PCT), and insulation resistance was assessed through the breakdown voltage experiment. The results indicate that the addition of nylon powder increases the fracture energy of the cured epoxy; however, mechanical properties (lap shear strength, flexural strength, tensile strength) decreased slightly. The TMA and DMA results showed that the CTE (α₁) decreased when nylon was added and the heat resistance decreased a little. The water absorption rate test and PCT showed that the rate of water absorption increased to a small extent, whereas the breakdown voltage decreased slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3504–3509, 2006     

耐高温高导热环氧树脂／玻纤／BN复合材料的制备

以4,4-二氨基二苯砜（DDS）和内亚甲基四氢邻苯二甲酸酐（NA）为复配固化剂,采用高温模压成型法制备耐高温高导热环氧树脂／玻纤／氮化硼（BN）复合材料。探讨了BN用量和偶联剂处理对复合材料冲击强度、导热性能和电阻率的影响。结果表明：当nDDS：nNA=3：1时,复合材料的耐热性能最佳。当BN质量分数为8％时,复合材料的冲击强度最高;导热性能随BN用量的增加而增加,当BN用量为15％时,热导率为0．7560W／（mk）,此时复合材料仍保持较高的体积、表面电阻率;当BN填充量为一定值时,偶联剂处理使冲击强度和导热性能得到进一步提高。     

Vacuum-based picking-up of thin chip from adhesive tape

The reliable picking-up of thin chip using the vacuum sorption determines the success rate of flip chip assemblies from donor tape to receptor substrate. An analytical solution to model the chip–adhesive–tape structure with vacuum loads is introduced to understand the fracture mechanism of chip picking-up. The critical process parameters (the length of bonded region, vacuum strength, and pick-up displacement, etc.) are investigated. Theoretical predictions are used in combination with virtual crack-closure-based finite-element technique to reveal the detaching behavior between the chip and the adhesive tape. The results show that the length of the bonded region should be controlled less than 40% of chip length to eliminate the effects of chip thickness, and the higher vacuum strength acting on the adhesive tape is able to accelerate the detachment of the chip from the adhesive tape. In particular, a process window is proposed to enhance the reliability and efficiency of picking-up for a thin chip.     

CA-SA分子合金的制备及储热性能研究

用差示扫描量热仪(DSC)分析研究了癸酸(CA)/硬脂酸(SA)二元混合物的热性能,结果表明,CA-SA合金没有一个确定的低共熔点,只有一个配比范围,并用IR和DSC对81%CA-SA二元混合物经180次加速冷热循环前后的分子结构和热性能进行对比研究,分析表明,此共熔物的分子结构没有发生变化,相变温度和相变焓变化较小,热性能稳定,适合作为相变储能材料。     

Thermal insulation and structural reliability of modified epoxy resin-based ablation thermal protection coatings in aerothermal-vibration coupling environment

Novel hybrid ablation thermal protection coatings (FHMP-ATPCs), employing iron trioxide (Fe₂O₃) powder, hollow glass microspheres, and mica powder as the fillers in hydroxyl-terminated silicone oligomer-bridged epoxy resins (PSG) copolymer, is investigated using an aerothermal-vibration coupling test system. The ablation behavior and structural reliability of FHMP-ATPCs with varying coating thickness were studied. During the test, the total enthalpy of airflow and dynamic pressures are 23 MJ/kg and 300 Pa, accompanied by the random vibration with a frequency of 20–2000 Hz and a total root-mean-square acceleration of 14.9g. The maximum surface and back-face temperatures of the coating with the thickness of 2 mm reached 836.2°C and 156.4°C, respectively. Results also showed that the reduction of thickness obviously suppressed the surface temperature and increase in back-face temperature yet maintaining high structural reliability. Compared with DGEBA-based coatings, the PSG-based coatings showed excellent structural reliability during the test. The study provides a solution for obtaining high performance ATPCs, which are highly desired for supersonic vehicles.     

Curing behavior and residual stresses in polymeric resins used for encapsulanting electronic packages

Polymeric encapsulants are applied in electronic packages to improve the mechanical/thermal performance and the reliability of packaged devices. During the curing process of encapsulating resin, large residual stresses are generated due to the shrinkage of polymer and the mismatches in the coefficient of thermal expansion (CTE) between various package components. In addition, the rheological properties and curing kinetics of the resin also affect the nature and distribution of residual stresses. In this work, the rheological and curing behavior of encapsulating resins are characterized using an oscillatory rheometer. The resin viscosity is closely monitored against curing temperature excursion, which is correlated to exothermic reaction and weight loss as measured from the DSC and TGA analyses. The evolution of residual stresses in encapsulating resin is evaluated in a bimaterial strip bending experiment (BMSB) in situ within a DMA chamber. The CTE values are then calculated based on the thermomechanical analysis, which are well compared with those determined from other sources. A transition temperature, apart from the glass transition temperature, is identified from the study of the changes in resin flexural modulus and residual stress profiles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 175–182, 2005     

New triepoxy monomer and composites for thermal and corrosion management

The denser and faster componented next-generation electronic devices produce an increased amount of heat during operations. Thermal dissipation is critical to the performance, lifetime, and reliability of electronic devices. With emerging of new applications such as three-dimensional chip stack architectures, flexible electronics, and light-emitting diodes, thermal dissipation becomes a challenging problem. In this study, a new resole-based epoxy monomer is designed. The novelty of the monomer is triepoxy functional soth upon curing (polymerization) the crosslink density is more. Composites of this epoxy with graphene functionalized with amine have been synthesized and characterized by thermal and mechanical methods. The thermal conductivity is increased to 0.6 W/mK by using graphene amine (12 wt%), which suggests that the composites can be useful for encapsulations. The composites are also useful as a coating material for corrosion protection on mild steel (MS). The electrochemical polarization studies on coated specimens showed that the composites are excellent coatings, which exhibited a very low corrosion rate of the order of 10⁻³–10⁻⁴ mm/year.     

Simultaneous improvement of thermal conductivity and mechanical properties for mechanically mixed ABS/h-BN composites by using small amounts of hyperbranched polymer additives

Recently, thermal interface materials (TIMs) are in great demands for modern electronics. For mechanically mixed polymer composite TIMs, the thermal conductivity and the mechanical properties are generally lower than expected values due to the sharply increased viscosity and poor filler dispersion. This work shows that addition of a small amount of polyester-based hyperbranched polymer (HBP) avoided the trade-off in mechanically mixed ABS/hexagonal boron nitride (h-BN) composites. After adding 0.5 wt% HBP, the maximum h-BN content in the composites increased from 50 to 60 wt%. The out-of-plane, in-plane thermal conductivity, and tensile strength of ABS/h-BN with 50 wt% h-BN were 0.408, 0.517 W/mK, and 18 MPa, respectively, and were increased to 0.729, 0.847 W/mK, and 32 MPa by adding 0.5 wt% HBP, while 0.972, 1.12 W/mK, and 29.5 MPa were achieved for ABS/h-BN/HBP with 60 wt% h-BN. The morphological and rheological results proved that these enhancements are due to the improved h-BN dispersion by decreasing viscosity of composites during mixing. Theoretical modeling based on the modified effective medium theory confirmed such results and showed that the interfacial thermal resistance also decreased slightly. Thus, this work demonstrates a facile and scalable method for simultaneously improving the thermal conductivity and mechanical properties of thermoplastic-based TIMs.     

环氧树脂基导热复合材料的研究进展

介绍了环氧树脂基导热复合材料的导热机理和导热模型,概述了国内外近年来在环氧树脂复合材料导热方面的研究开发和应用情况。     

Preparation,intermolecular motion,and thermal properties of thiodiphenyl epoxy

The thiodiphenyl epoxy (THEP) was prepared by the 4,4′‐thiodiphenol (THDOL) and the epichlorohydrin (ECH) without using any NaOH or KOH catalysts. The THEP possessed weak hydrogen bonding in the cured THEP/DGEBA system. The intermolecular motion parameters k and q were 0.26 and ?168.5, respectively, which determined by the Gordon‐Taylor and Kwei equations. The soft sulfide linkage (? S? ) of the THEP degraded at lower temperature than cured DGEBA material, and further to form various thermal stable sulfate derivative chars. The char yields increased from 11.43 to 25.94 wt % and from 0.65 to 1.04 wt % in the nitrogen and air, respectively. Introduction of the THEP into the DGEBA could provide the antioxidation thermal property and improve the thermal stability of the DGEBA epoxy in the air. In the air atmosphere, the activation energies of the second thermal degradation were increased from 66.67 to 103.42 kJ/mol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Aerogel/epoxy thermal coatings for carbon fibre reinforced plastic substrates

The present work studies an aerogel/epoxy composite that was dip coated onto a carbon fibre substrate by adding the aerogel at the 1?h and the 1.5 mark of the epoxy cure. Both coatings show decrease in thermal conductivity values (39% and 47% respectively) when compared to a pure epoxy coating. The coatings’ reflectance spectra also provided further evidence for the existence of the nano-pores within the aerogel particles. The aerogel coating was modelled using material properties from literature and solved using finite element methods. The model, which validated using experimental data, was then used to predict the coating’s performance in cyclic thermal loads. Additionally, coatings on a single surface- top and bottom; were also modelled and compared with the double coating system wherein it was seen that the double coating system had the lowest rate of temperature change and fluctuations at steady-state in contrast to the bottom coating which, showed the fastest drop in temperature as well as the highest fluctuations at steady state conditions. The performance of the top coating was in the middle.     

一种新型H级少胶粉云母带的研制

该H级少胶粉云母带采用改性环氧树脂为胶粘剂,无碱玻璃布浸渍树脂后先后分别复合粉云母纸和聚酰亚胺薄膜(耐电晕处理或不耐电晕处理),经烘焙、收卷、分切、包装而成的一种电机主绝缘材料。探讨了该材料的常规电气性能及与不同类型的浸渍树脂配套绝缘性。     

Comparison of the thermal stabilities of some resin matrices for composites

The thermal stabilities of eleven different epoxy resin formulations, ten different polyimide resin formulations, a triazine resin formulation and two aromatic thermoplastic matrices have been compared by isothermal gravimetry in air. The overall activation energies for degradation as a function of percentage weight loss have been determined by regression analysis of the isothermal data. The values obtained indicate a very complex breakdown mechanism in the majority of cases.     

The effect of the ring opening polymerization and chain spacing on the coefficient of thermal expansion and modulus of polyimide

The features of norbornene (NE) cross‐linked polyimide (PI) were investigated as the ratio of the norbornene monomer was varied. The coefficient of thermal expansion and modulus are important parameters of materials used in the microelectronic industry. Therefore, in this study, 5‐norbornene‐2, 3‐dicarboxylic acid (NE) was introduced as a crosslinking agent to increase the thermal stability at elevated temperatures. 4,4′‐Benzophenonetetracarboxylic dianhydride was utilized as a dianhydride and 4,4′‐diaminodiphenyl ether was introduced as a diamine monomer. By changing the ratio of each monomer, we were able to control the spacing of the chain and ring opening polymerization, which resulted in improved properties. Each sample was thermally cured which led to a ring opening mechanism of the norbornene through the reverse Diels‐Alder reaction. Thermal mechanical analysis was utilized to determine the coefficient of thermal expansion and dynamic mechanical analysis was used to determine the storage modulus (ε′) and loss modulus (ε″) of the PI film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42607.     

New investigation of 1‐substituted imidazole derivatives as thermal latent catalysts for epoxy‐phenolic resins

Novel 1‐substituted imidazole derivatives ( 4 – 10 ) were synthesized by imidazole and the corresponding substituted reagents (chloromethylpivalate, diphenylphosphinicchloride, di‐tert‐butyldicarbonate, 1,1′‐oxalylchloride, pyrazine, phneylisocyanat, and p‐toluensulfonylchloride). Polymerization of diglycidyl ether of bisphenol A (DGEBA) with 1‐substituted imidazole derivatives, two commercial available catalysts (imidazole and 1‐cyanoethyl‐2‐ethyl‐4‐methylimidazole) and N‐benzylpyrazinium hexafluoroantimonate were investigated as model reactions of epoxy resin systems with respect to the thermal latency and storage stability of the catalysts. The catalytic activity of 1‐substituted imidazole derivatives 4 – 10 depended on the steric and withdrawing electronic effect of the substitution groups. To characterize the cure activation energy and the viscosity‐storage time, the order of thermally latent activity is 1‐tosylimidazole ( 6 ) > 1,1′‐oxalyldiimidazole ( 8 ) > N‐benzylpyrazinium hexafluoroantimonate (BPH, 3 ) > 1‐tritylimidazole ( 9 ) > N‐phenyl‐imidazole‐1‐carboxamide ( 5 ) > 3‐(diphenylphosphinoyl)imidazole ( 7 ) > tert‐butyl‐1H‐imidazole‐1‐carboxylate ( 4 ) > 1‐cyanoethyl‐2‐ethyl‐4‐methylimidazole (2E4MZ, 2 ) > 1‐[(pivalyloxy)methyl]imidazol ( 10 ) > imidazole ( 1 ). In comparison with commercially available catalysts imidazole ( 1 ) and 1‐cyanoethyl‐2‐ethyl‐4‐methylimidazole ( 2 ) and a cationic latent catalyst N‐benzylpyrazinium hexafluoroantimonate (BPH, 3 ) as the standard compounds, in addition to 1‐[(pivalyloxy)methyl]imidazole ( 10 ), the 1‐substituted imidazole derivatives ( 4 – 9 ) revealed better thermal latency. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007