Miho Yamaguchi

Effect of particle size on fracture toughness of epoxy resin filled with angular-shaped silica

Abstract The effect of particle size on the fracture behaviour of cured epoxy resin filled with angular-shaped silica was studied. Angular-shaped silica particles were prepared by crushing fused natural raw silica and were classified into six groups with different mean sizes ranging from 2 to 47 μm. Critical stress intensity factor ( K c ) and critical strain energy release rate ( G c ) of the cured epoxy resin filled with these silica particles were measured. Both K c and G c values increased with an increase in particle size of the silica. Scanning electron microscopic observations of crack tips and fractured surfaces showed that the damage zone was formed at the crack tip by particle fracture and by crack diverging. This phenomenon became more pronounced with increase in the particle size. The higher K c and G c values appear to be derived from the dispersion of the stress concentrated at the crack tip due to the crack diverging and from energy absorption due to the formation of a damage zone.

Effect of particle size on the fracture toughness of epoxy resin filled with spherical silica

Abstract The effect of particle size on the fracture behaviour of cured epoxy resin filled with spherical silica particles was studied. Five kinds of spherical silica particles prepared by hydrolysis of silicon tetrachloride having different mean sizes, ranging from 6 to 42 μm, were used. The critical stress intensity factor (Kc) and the critical strain energy release rate (Gc) of the cured epoxy resins filled with the silica particles were measured. Both Kc and Gc values increased with particle size. Scanning electron microscope observation shows that the main crack propagation was hampered by large particles and a damage zone was formed at the main crack tip region in the large particle filled resin due to crack diversion and debonding of particle/matrix interfaces. The higher Kc and Gc values seem to be derived from these phenomena.

Effect of particle size on impact properties of epoxy resin filled with angular shaped silica particles

Abstract The effect of particle size on the impact properties of cured epoxy resin has been studied. This resin is filled with angular shaped silica particles that were prepared by crushing fused natural raw quartz. These particles were sorted into six groups having different mean sizes ranging from 2 to 47 μm. Specimens having a U-shaped blunt notch were prepared. The impact properties were measured by an instrumented Charpy type impact tester which can record a load-displacement curve at impact fracture. The impact absorbed energy increased with a decrease in silica particle size. The fractured surfaces were studied using a scanning electron microscope to clarify the initiation point of fracture.

Thermal shock test of integrated circuit packages sealed with epoxy moulding compounds filled with spherical silica particles

Abstract The effect of filler silica particle size on the properties of integrated circuit (IC) packages sealed with epoxy moulding compound was studied. For this purpose, four epoxy moulding compounds filled with spherical silica particles having mean sizes in the range 6 ∼ 31 μm were prepared. Critical stress intensity factor (Kc) and flexural strength (σ) of the cured epoxy moulding compounds were measured. As the particle size increased, the Kc value increased and the σ value decreased. The thermal shock test was carried out: IC packages were repeatedly dipped alternately in liquids at −65°C and 150°C and the occurrence of package cracking was observed. The cracking took place at an earlier stage of the thermal shock test when the particle size was smaller. There was a good relationship between the thermal shock test result and the Kc value.

Development of novel anisotropic conductive film (ACF)

Developments on flip chip connections are ongoing for high density packaging in the electronics industry. Anisotropic conducting adhesive is an interconnecting material for one of the flip chip packaging methods. Electronic Industries Association of Japan (EIAJ) forecasts, in the roadmap of Semiconductor Packaging Technology, that such an adhesive material will be used for connecting bump-less chips and printed circuit boards in a pitch of 0.040 mm in the year 2000. The development on the novel structure of anisotropic conductive film (ACF), started to achieve the ultimate IC-packaging system, in which bump-less chips can be electrically connected and encapsulated on circuit boards through this ACF. Optimizing the structure and material can improve a variety of operational conditions, such as bonding time, pressure and temperature. These improvements can contribute to better throughput, when the ACF connects chips and circuit boards in the assembly process, and allow one to remove the defective chips from the board after connecting chips and boards with the ACF. This development is extended to wafer level packaging from the die level, for more effective IC-packaging. The enlarged ACF successfully and reliably bonds to wafers. This paper is an overview of the novel ACF in the packaging application, including its wafer level handling.

Internal stress of epoxy resin modified with acrylic polymers containing functional groups produced by in situ u.v. radiation polymerization

Abstract To reduce the internal stress generated in cured epoxy resin by shrinkage in the cooling process from cure temperature to room temperature, three kinds of acrylic polymer were introduced by in situ ultraviolet radiation polymerization before the curing. They were polybutyl acrylate (A), butyl acrylate-glycidyl methacrylate copolymer ( 95 5 , mole ratio) (B) and butyl acrylate-monoethylene glycol dimethacrylate copolymer ( 95 5 , mole ratio) (C). In the A and B modified resins, a heterogeneous structure with spherical shaped submicrometre domains consisting of acrylic polymers was formed. In the C modified resin, a heterogeneous structure with irregularly shaped submicrometre domains was formed. Further, in the B and C modified resins, microphase separation was observed in the domains. These results suggest that the interaction between acrylic polymer domains and the epoxy matrix increased in the order C>B>A modified resin. As a result of the modifications, the modulus and the internal stress of cured epoxy resin decreased effectively in the same order.

Non halogen/antimony flame retardant system for high end IC package

All industries have started to conduct research in environmentally safe materials. In the electronics industry also environmental issue is one of the most important concerns being addressed with rapid technical improvement. Flame retardant agents like halogen and antimony oxide are used in plastic molding compounds to provide flame retardant characteristics to all plastic encapsulated packages. However these materials have concerns as they are considered environmental hazards. This paper deals with the study of a new environmentally safe flame retardant system for plastic encapsulants. We studied the application of a new non halogen and non antimony oxide flame retardant system for the molding compound of Ball Grid Arrays (BGA) as the next generation conventional standard package.

Internal stress of epoxy resin modified with acrylic polymers having crosslinks produced byin situ UV radiation polymerization

In order to reduce the internal stress of cured epoxy resin generated by shrinkage in the cooling process from cure temperature to room temperature, two kinds of acrylic polymers were introduced byin situ UV radiation polymerization prior to curing. Polybutyl acrylate (A) and butyl acrylate-monoethylene glycol dimethacrylate copolymer (molar ratio 95∶5) (B) were used as the acrylic polymer. In the A-modified resin, a heterogeneous structure with spherical submicrometre domains were formed. In the B-modified resin, irregularly shaped submicrometre domains in which the microphase separation occurred were observed. The modulus of cured epoxy resin decreased as a result of the modifications, and was lower in the B-modified resin than in the A-modified resin. Therefore the internal stress decreased more effectively in the B-modified resin.

Bare die probing with novel anisotropic conductive film (ACF)

Flip chip interconnection technology has been considered the best solution for high-density packaging of a variety of electronic devices. However, there still remain several technical obstacles. The infrastructures are not perfectly ready for die handling/assembling, die-quality assurance, and so on. Especially, an effective bare die testing/screening method is necessary for the electronics industry. The novel Anisotropic Conductive Film (ACF), described in this paper, is composed of high density pillars (linear metal material) which form sequential conductive paths in the direction of the thickness of the thermoplastic film. Developments are ongoing for creating the ultimate IC packaging system for connecting bump-less dice on printed circuit boards, under appropriate thermal pressure conditions. The material and structure of this ACF are optimized for bare die testing/screening applications. The fine pitch terminals, with Au bumps on a bare die, can be probed with reasonable pressure by using this ACF. The electrical contact performance of the ACF was improved in the structure with lower modulus resin, less thickness and optimized pillar pitch. This ACF will hopefully be utilized as an effective interconnecting material for semiconductor device testing/screening systems.