Properties Of Epoxy Molding Compound Research Articles

Investigation of Warpage for Multi-Die Fan-Out Wafer-Level Packaging Process.

This paper focuses on characterizing the evolution of warpage, effects of epoxy molding compound (EMC), and effects of carrier 2 (the second carrier in the process) of 12 inch RDL-first multi-die fan-out wafer-level packaging (FOWLP) during the manufacturing process. The linear viscoelasticity properties of EMC and polyimide (PI) were characterized using dynamic mechanical analysis (DMA) in the frequency domain at different temperatures., The elastic and viscoelastic model were used for PI and EMC, the finite element analyses (FEA) of the cured structure were carried out and the results were compared with the test results. The viscoelastic properties of the EMC in the FEA could predict the wafer warpage more accurately. The FEA and experiments were used to investigate the evolution of warpage. The molding had a great influence on the warpage. The effects of the EMC and carrier 2 were also investigated with FEA. The wafer warpage could be reduced by lowering the thickness of the EMC, increasing the thickness of carrier 2, and selecting EMC and carrier 2 with a matched coefficient of thermal expansion (CTE).

Effect of critical properties of epoxy molding compound on warpage prediction: A critical review

For the past couple of decades, a considerable amount of time and effort has been spent to enhance the predictability of warpage of semiconductor packages encapsulated by epoxy molding compound (EMC). With advanced computational mechanics techniques and computing hardware, one can simulate almost any kind of packages. Thermo-mechanical properties required for numerical predictions, including the coefficient of thermal expansion (CTE), the glass transition temperature (Tg), and the temperature and time-dependent viscoelastic properties, are routinely measured by commercial tools such as thermo-mechanical analyzer (TMA) and dynamic mechanical analyzer (DMA). In addition, temperature-dependent warpage can be measured readily using commercial tools based on shadow moiré and digital image correlation (DIC). In spite of this considerable effort, accurate prediction remains a challenging task. EMC typically occupies a large portion of package volume, and thus plays a major role in package warpage behavior. This review paper examines the effect of critical EMC properties on warpage behavior. Based on the data and the analyses reported in the literature, the paper addresses three potential causes that make the prediction still difficult, and discusses what should be done to bring the prediction capability to a desired level.

Numerical and Experimental Studies of Fabrication-Induced Thermal Residual Stresses in Microelectronic Packages

Microelectronic packages are typically composed of different layers of materials with un-similar thermo-mechanical properties. Fabrication-induced residual stresses, resulting from the mismatch of layers' thermo-mechanical properties, may lead to adverse effects such as warpage and delamination at the interface of layers. In this study, the fabrication process of the ball grid array (BGA) package was simulated to predict the thermal residual stresses through the thickness of the package. A finite-element model incorporating realistic material behavior of the BGA package layers was developed. To this end, the epoxy molding compound (EMC) was modeled as a viscoelastic material, while the silicon chip, the die-attach, and the composite substrate were simulated using an elastic model during cooling. Since Young's modulus of EMC is time and temperature-dependent, three different process temperatures were simulated to investigate the impact of viscoelastic properties of EMC, defined using Prony coefficients, on numerical residual stresses. To verify the simulation results, the incremental hole-drilling method was used to experimentally measure the residual stress components. It includes drilling a small hole at the center of a rosette strain gauge bonded on the BGA package surface and measuring the released strains on the surface. The relaxed strains were then converted to the residual stresses using a calibration matrix whose coefficients are determined from a finite-element model. The reasonable agreement of numerical and experimental components of the residual stress throughout the thickness of the BGA package confirms the reliability of the proposed simulation approach in estimating residual stresses in microelectronics packages.

Effect of Boron Nitride Nanosheets on Properties of a Commercial Epoxy Molding Compound Used in Fan-Out Wafer-Level Packaging

In this article, the effect of incorporating boron nitride nanosheets (represented as BNNSs in this article) in a commercial epoxy molding compound (EMC) that has been used in the fan-out wafer-level packaging (FOWLP) is investigated. The BNNSs were produced by exfoliating hexagonal boron nitride (h-BN) in water and were incorporated in EMC without any surface modification. BNNS-reinforced EMCs were prepared by adding various concentrations of BNNSs in the pristine EMC, followed by thermal curing. The characterization of nanocomposite samples implies that the epoxy-hardener reaction is not significantly affected by the presence of BNNSs. Surprisingly, EMCs containing low concentrations of BNNSs showed better thermal stability and thermomechanical properties when compared to the pristine EMC. Meanwhile, a sample with the highest concentration of BNNSs performed poorly, which could be due to the BNNS agglomeration and filler/polymer phase separation. This method is a simple and inexpensive way to alter the mechanical properties of commercial EMCs. The tunability of material properties is foreseen to broaden the materials of choice for FOWLP, support product customization, and tackle the warpage issue in FOWLP from the material engineering perspective.

Effect of Organosilane Coupling Agents on Thermal, Rheological and Mechanical Properties of Silicate-Filled Epoxy Molding Compound.

Global industries strive towards the production of materials with superior mechanical characteristics, and their development remains a big challenges. One of the more interesting materials that exhibit these properties are silicate-filled epoxy molding compounds (EMCs). A good interaction between silicate filler and epoxy matrix is generally needed to achieve advantageous mechanical properties, as well as the desirable rheological behavior of EMCs. Understanding the influence of different organosilane coupling agents on the rheological and mechanical properties of EMCs is essential in the development and optimization of the manufacturing process. For this matter, a mixture of calcium silicate and aluminosilicate was treated by using organosilane coupling agents with different chemical structures and thus treated silicates were applied as fillers in the EMCs. The thermal behavior of the organosilane-modified, silicate-filled EMCs was studied by using differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). Flow-curing behavior (torque rheometer) and spiral flow length measurement (EMMI) were used to monitor the rheological properties and reactivity of the EMCs. The results showed that 3-glycidyloxypropyltrimethoxysilane- and 3-aminopropyltriethoxysilane-treated filler had a greater influence on the tensile strength of hot-pressed test samples, while 3-aminopropyltriethoxysilane and a blend of primary and secondary aminosilanes had a more significant impact on the rheological behavior of the material.

The Effects of Silica-Based Fillers on the Properties of Epoxy Molding Compounds.

Global design and manufacturing of the materials with superb properties remain one of the greatest challenges on the market. The future progress is orientated towards researches into the material development for the production of composites of better mechanical properties to the existing materials. In the field of advanced composites, epoxy molding compounds (EMCs) have attained dominance among the common materials due to their excellent properties that can be altered by adding different fillers. One of the main fillers is often based on silicon dioxide (SiO2). The concept of this study was to evaluate the effects of the selected silica-based fillers on the thermal, rheological, and mechanical properties of EMCs. Various types of fillers with SiO2, including crystalline silica and fused silica, were experimentally studied to clarify the impact of filler on final product. Fillers with different shape (scanning electron microscope, SEM), along with different specific surface area (specific surface area analyzer, BET method) and different chemical structure, were tested to explore their modifications on the EMCs. The influence of the fillers on the compound materials was determined with the spiral flow length (spiral flow test, EMMI), glass transition temperature (differential scanning calorimetry, DSC), and the viscosity (Torque Rheometer) of the composites.

Effecting aging time of epoxy molding compound to molding process for integrated circuit packaging

This research studied about effecting aging time of epoxy molding compound (EMC) that effect to reliability performance of integrated circuit (IC) package in molding process. Molding process is so important of IC packaging process for protecting IC chip (or die) from temperature and humidity environment using encapsulated EMC. For general molding process, EMC are stored in the frozen at 5°C and left at room temperature at 25 °C for aging time on self before molding of die onto lead frame is 24 hours. The aging time effect to reliability performance of IC package due to different temperature and humidity inside the package. In experiment, aging time of EMC were varied from 0 to 24 hours for molding process of SOIC-8L packages. For analysis, these packages were tested by x-ray and scanning acoustic microscope to analyze properties of EMC with an aging time and also analyzed delamination, internal void, and wire sweep inside the packages with different aging time. The results revealed that different aging time of EMC effect to properties and reliability performance of molding process.

Measurement of Elastic Properties of Epoxy Molding Compound by Single Cylindrical Configuration with Embedded Fiber Bragg Grating Sensor

We propose a novel experimental method, based on a fiber Bragg grating (FBG) sensor, to measure the elastic properties of epoxy molding compound (EMC) from a single specimen configuration. The FBG sensor is embedded in the center of a cylindrical EMC specimen, and deforms together with the EMC. The Bragg wavelength (BW) shifts are documented during compressive and hydrostatic loadings. Young’s modulus and bulk modulus are determined from the BW shifts using the relationships between the elastic constants and the BW shift. Two major developments to accommodate the unique requirements of EMC testing include: (1) a large mechanical pressure to be applied during curing; and (2) a very high gas pressure required for hydrostatic testing. The shear modulus and Poisson’s ratio are calculated from the two measured constants to provide a complete set of elastic properties of EMC.

Comprehensive Moisture Diffusion Characteristics of Epoxy Molding Compounds Over Solder Reflow Process Temperature

We address moisture diffusion in epoxy molding compounds (EMCs) at temperatures higher than 100 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. The objectives of this paper are thus: 1) to obtain diffusion properties of EMCs in both absorption and desorption modes at a wide range of temperatures; 2) to establish a non-Fickian correlation for diffusivity; and 3) to assess moisture diffusion behaviors during a solder reflow process, described by two different Fickian diffusivities of absorption and desorption and the non-Fickian diffusivity. An experimental procedure is established to measure the diffusivity and solubility of selected EMC materials. The results are utilized in a numerical simulation to analyze the effect of the non-Fickian diffusion characteristics on the moisture distribution during the reflow process.

Plasma Surface Modification of Silica and its Application in Epoxy Molding Compounds for Large-Scale Integrated Circuits Packaging

The surface modification of silica for epoxy molding compounds (EMC) was conducted by plasma polymerization using RF plasma (13.56MPa), and the modification factors such as plasma power, gas pressure and treatment time were investigated systematically in this paper. The monomers utilized for the plasma polymer coatings were pyrrole, 1,3-diaminopropane, acrylic acid and urea. The plasma polymerization coating of silica was characterized by FTIR, contact angle. Using the silica treated by plasma as filler, ortho-cresol novolac epoxy as main resin, novolac phenolic-formaldehyde resin as cross-linking agent and 2-methylmizole as curing accelerating agent, the EMCs used for the packaging of large-scale integrated circuits were prepared by high-speed pre-mixture and twin roller mixing technology. The results have shown that the surface of silica can be coated by plasma polymerization of pyrrole, 1,3-diaminopropane, acrylic acid and urea, and the comprehensive properties of EMC were improved.

Properties of epoxy molding compound according to the pretreatment method of an amino-silane coupling agent on epoxy or phenol resin

An amino-functional silane coupling agent, which is an important component for epoxy molding compound (EMC), has been used by diverse methods, such as integral addition into a mixed powder and pretreatment on silica or on resin. However, the homogeneous dispersion of the amino-functional silane coupling agent in mixed powder is limited with integral addition, and the possibility of white gel formation, sometimes causing gate blocking during the transfer-molding process, due to the aggregation of silica with the coupling agent cannot be completely removed by it. The pretreatment of the amino-functional silane coupling agent on silica has been adopted as an alternative process, but the process is expensive and limited in mass production. Although the pretreatment of the coupling agent on resin as another method has also been used by some EMC manufacturing companies, it has hardly been known in which resin phase, the epoxy or hardener, the silane coupling agent should be pretreated for better mechanical properties of EMC. In this study, the pretreatment of the amino-functional silane coupling agent on epoxy or phenol resin, essential components of EMC, has been investigated with respect to the reaction during the pretreatment and the properties of EMC according to the different pretreatment methods. In the case of the pretreatment on epoxy, the amino-functional silane coupling agent rapidly forms an adduct with epoxy via a ring-opening reaction, whereas its alkoxy groups are well preserved. The glass-transition temperature and flexural strength of the EMC by the application of the pretreatment method on epoxy are lower than those by the pretreatment on phenol. It is thought that the degree of linkage between the resin matrix and silica becomes lower because of the confinement of aminopropyltriethoxy silane (APTS) within the epoxy matrix through an irreversible reaction with epoxy in advance. In the case of the pretreatment on phenol, most of the alkoxy groups in the coupling agent are assumed to be replaced with protonic nucleophiles such as phenol, generating an equivalent amount of alcohol. Because the adduct between the phenol and amino-functional silane coupling agent can be easily regenerated during the manufacturing process, it is thought that the pretreatment method of APTS on phenol helps APTS disperse well within EMC. Actually, the glass-transition temperature and flexural strength of EMC by the application of the pretreatment method on phenol are higher than those by the integral addition method and the pretreatment on epoxy. However, they become lower as the degree of reaction of silane with phenol increases. The pretreatment of the amino-functional silane coupling agent on phenol shows lots of advantages over the previous methods. From the viewpoint of the process, the homogeneous dispersion of the coupling agent can be obtained with consistency, and the possibility of white gel formation can also be completely removed by it. From the perspective of properties, through a controlled pretreatment on phenol resin, better mechanical properties of EMC can be obtained than those through the pretreatment on epoxy. In addition, the pretreatment process on phenol is simple and feasible for mass production. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2171–2179, 2006

The effect of hygro-mechanical and thermo-mechanical stress on delamination of gold bump

The reliability of the FC–CSP (flip chip–chip scaled package) package with gold bump at the MRT (moisture resistance test) reflow temperature, was evaluated by using the finite element method. The moisture properties of EMC (epoxy molding compound) obtained from the test described in JEDEC standard, were used to characterize the local moisture concentration analysis by transient moisture diffusion, the hygro-mechanical analysis by CME, the vapor pressure analysis and the thermo-mechanical analysis by CTE mismatch. Also, after precondition, the package reliability under the reflow process was predicted, by comparing and integrating each factors, package swelling and stress due to by vapor pressure, as well as thermo-mechanical stress. Consequently, the result showed that the effects on hygro-mechanical stress and vapor pressure in a package could not be negligible, when it is compared with that of the thermo-mechanical stress by CTE mismatch, which is recognized as the main effect on the package crack under reflow temperature. The stress was concentrated at interface between gold bump and die, where most of delamination occurred.

Physical properties of epoxy molding compound for semiconductor encapsulation according to the coupling treatment process change of silica

The change of physical properties of an epoxy-molding compound (EMC) for semiconductor encapsulation according to the coupling treatment process change was investigated. Three different coupling treatment processes were applied in this study: the pretreatment method (PM), the internal pretreatment method (IPM), and the integral addition method (IAM). Especially, we suggested a simple and economic process, the IPM process, in which the drying and powdering process is excluded compared with the PM process. The optimum content range of the coupling agent is 1.0–2.0 wt % based on the weight of the filler, which is about a 1.3–2.5 coating layer. The flexural strength and internal stress of EMC made by the IPM process is almost equivalent to that made by the PM. We applied the model of complex layers of a silane coupling agent at the filler/matrix interface in interpretating the mechanical and thermal properties of EMC and obtaining the relationships between physical properties and the coupling process. It can be concluded that the IPM process is an effective and economic process to be able to obtain a good reliable EMC with strong mechanical strength and low internal stress. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1975–1982, 1997

Effects of curing accelerators on physical properties of epoxy molding compound (EMC)

AbstractThe effects of various curing accelerators on the physical properties of epoxy molding compounds (EMCs) were investigated. Such properties as elasticities in rubbery and glassy regions, glass transition temperature, thermal expansion coefficient, and water absorption at 60°C of neat epoxy resins using various curing accelerators were found to be directly reflected in the properties of the EMCs that were prepared by using each resin system. However, volume resistivity and saturated water absorption at 120°C were not reflected. This was attributed to differences in the catalytic reactivity of accelerators causing different melt viscosity for the EMC, which resulted in different densities (packing degrees) and affected physical properties of molded EMC. On the other hand, it was found that the density of molded EMC was also affected by the molding conditions. To improve the physical properties of the molded EMC, in addition to proper selection of accelerators, it was very important to set the melt viscosity of the EMC as high as possible within the moldable range and to select suitable molding conditions.