Optics: measuring and testing – By polarized light examination
Reexamination Certificate
2000-12-27
2004-06-08
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By polarized light examination
C356S366000, C436S164000, C436S171000, C422S068100, C422S082050, C073S866000
Reexamination Certificate
active
06747739
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and equipment for measuring the internal structure of a composite material filled with ceramic particles having an irregular matrix. In more particularly, it relates to a method in which the internal structure (packing structure or dispersion condition of the particles) of a composite material filled with ceramic particles obtained by mixing raw ceramic particles into a liquid material is measured by making this visible and observing it by utilizing the photoelasticity based on local rearrangement of liquid material molecules, or the difference of refractive index of the particles and liquid material, and to an evaluation device used therein.
2. Description of the Related Art
Composite materials filled with ceramic particles are employed as insulating materials, electrode/conductive materials, electroviscous fluids, chemical/mechanical grinding slurries, and raw materials for ceramic molding processes such as injection molding and/or cast molding, and also, in recent years, have come to be widely used in sealing materials intended for protecting and insulating semiconductor elements. With progress in VLSI, in order to achieve increased element fineness, low viscosity/high forming ability of composite material filled with ceramic particles in order to achieve the ability to produce any required shape and/or to enable pouring between minute electrodes is indispensable.
However, scientific study of the field of such materials is still in its infancy and studies relating to the viscosity and moldability of composite material filled with ceramic particles are based merely on experience. For example, it means that lower viscosity of the composite is sought to be achieved by making the particle size distribution of the particles to be filled larger or by making the particle size of the particles larger. It has been pointed out that there are limits to the extent to which it is possible to achieve the accuracy required in for example semiconductor sealing materials simply using such conventional discoveries (for example, Shinsuke Hagiwara “The present state of development of semiconductor sealing materials”, Plastics, Vol. 49, p. 58, 1998 and Takeshi Kitano “Rheological properties of molten polymer solution filled with filler”, Filler, Vol. 3, p. 96, 1998).
A typical method of “directly” evaluating the distribution condition of a particular material filled/dispersed in a composite material is the method in which some of the dispersed material is collected and its surface is polished and the reflected image thereof is observed by using an optical microscope or scanning electron microscope (SEM). For example, Laid-open Japanese Patent Publication Number 10-292055 (1998) discloses the former method using an SEM and in Laid-open Japanese Patent Publication Number 9-302210 (1997) an optical microscope method is applied to evaluation of uniformity of particle dispersion. However, with such methods, there is the risk of altering the distribution condition of the particles by the surface processing and, in addition, the information obtained is restricted to that from the reflection surface of the light from the light source i.e. to 2-dimensional information, so the distribution condition of the particulate material could not be evaluated directly over a wide region.
As a method of direct evaluation similar to the above, there is the method of observing the transmitted image by producing a thin strip of thickness capable of transmitting light from the light source. For example, Laid-open Japanese Patent Publication Number 61-122543 (1986) and Laid-open Japanese Patent Publication Number 5-232010 (1993) disclose methods using the transmitted image obtained by an optical microscope. With these methods, the problem of adverse effects due to processing and 2-dimensional observation is solved. In fact, by means of these methods, it is possible to recognize the packed particulate material itself. However, by using these on their own it is not possible to evaluate the bonding condition at the interface between the particles and the resin or the coagulation condition that is secondarily constituted within the interior of the dispersion system by the particles. The dominant factors in regard to rheological properties of a resin polymer composite filled with particles, which are currently becoming even more vital, are considered to be interactions at the particle/resin interface and the resin constituents within coagulations thereof. Evaluation of these is indispensable but, with previous methods, as will be described in detail with reference to the examples below, it has not been possible to achieve this.
As a method of evaluating a composite filled with particles in comparatively large volume that supplemented the defects of the reflection observation method, there was the method of indirectly deducing the distribution condition of the particulate material by measuring for example the coefficient of viscosity, electrical resistance or tensile strength of the dispersion system. For example, Laid-open Japanese Patent Publication Number 6-229984 (1994) and Laid-open Japanese Patent Publication Number 11-64260 (1999) are examples of a method of measuring electrical resistance and Laid-open Japanese Patent Publication Number 10-311783 (1998) is an example of a method of measuring tensile strength. Even such methods were insufficient to obtain local information such as the interactions at the particle/resin interface or the particle coagulation structure.
One cause of the above problem is considered to be that no method has been established for observing the internal structure of a dispersed system and correlating this with mechanical properties/rheological properties/electrical properties etc. of the dispersion system in cases where the liquid material is a matrix or dispersion medium. For example, one problem is considered to be that no methodology has been established for the application of methods of measurement using an optical microscope or scanning electron microscope (SEM), which are universal in regard to dispersion systems where the dispersion medium of the particulate material is solid (for example ceramic material systems) to composite material filled with particles having an irregular matrix. Even where the matrix is a solid dispersion system, studies based on such a viewpoint have only just been commenced.
Conventionally, in addition to the risk of altering the distribution condition of the particles by surface processing methods using an SEM, the information obtained was restricted to the reflection surface of the light from the light source i.e. was only 2-dimensional information and so could not be used to evaluate the distribution condition of the particulate material directly in a region. In this regard, a method has been proposed for performing evaluation using transmission images utilizing the difference of refractive index etc. at the interface between particulate material and gas bubbles contained within the dispersion system (K. Uematsu, “Immersion microscopy for detailed characterization of defects in ceramic powders and green bodies”, Powder Technology, Vol. 88, p. 291, 1996). With this method, the problems of adverse effects due to processing and 2-dimensional observation are solved. Establishment of a similar method for evaluation in regard to liquid materials filled with particles is indispensable.
The case when the liquid material in a liquid material filled with particles.dispersion system is a resin-based material can be regarded as one type of polymer material. In polymeric material systems, typically use is made of polarized light observation for evaluation of the photoelasticity characteristic with applied stress, measurement of the birefringence of a plastic lens, or evaluation of molecular alignment characteristics in liquid crystal materials. However, previously, no attempts have been made to employ this for evaluation of the characteristics of particles, rather than resin,
Naito Makio
Sando Mutsuo
Takao Yasumasa
Uematsu Keizo
Agency of Industrial Science and Technology
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pham Hoa Q.
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