Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With provision for cooling the housing or its contents
Reexamination Certificate
2002-06-17
2004-07-13
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With provision for cooling the housing or its contents
C257S715000, C257S676000, C257S678000, C257S778000, C438S113000, C438S124000, C438S127000
Reexamination Certificate
active
06762492
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device in which a parasitic capacitance can be prevented, and to an image scanning unit utilizing the same and an image forming apparatus utilizing the same.
2. Description of the Prior Art
It is generally well known that an adhesive material (sealing material) is used in a space between a semiconductor chip and a substrate to reduce a physical stress by a thermal expansion on a circuit in order to prevent an electrical breakage at contacting point in an electrical circuit which is caused by a difference between the coefficient of thermal expansions of them when a semiconductor chip is bonded on a substrate by means of a face down bonding technology.
In the past when a semiconductor chip is utilized as an optical device, in order to prevent an occurrence of problem that an electrical performance of the device can not be carried out because the adhesive materials for the semiconductor chip happens to inundate to the accepting surface (or the light emitting surface) of the device and block off the light path, a method is employed in that a protruding portion is arranged for the adhesive material not to wraparound the accepting surface as disclosed in Japanese Laid Open Patent Hei 06-204442.
However in the above described method, there were problems that a manufacturing cost of the device was got higher to form the protruding portion, and the production process for it was made complicated because there was a need that the protruding portion had to be made at the entire circumference of the semiconductor chip and the need had to be satisfied in the process.
The above described wraparound problem is viewed with suspicion not only in the optical devices but also in a device for high frequency circuit. In the high frequency circuit, there may be a fear that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance. It is very difficult to estimate the parasitic capacitance with preliminary survey especially when it is made in a large scale production, and it is impossible to make an amount of the wraparound constantly without fluctuation. In a recent movement of a realization of high speed driving of semiconductor, the problem of parasitic capacitance comes out to fore and it causes an unable problem to disregard in the whole business world of semiconductor mounting.
SUMMARY OF THE INVENTION
Because of these situation an object of the present invention is to provide a semiconductor device, an image scanning unit and an image forming apparatus in that there are no need to arrange the protruding portion and in that the parasitic capacitance is prevented.
To attain the above described object by the present invention a semiconductor device including: a substrate which has a wiring portion; and a semiconductor chip which has a functional surface in a front surface thereof and which is bonded by flip chip bonding onto the substrate; wherein an adhesive material which is used to adhere and fix the semiconductor chip and the substrate, adheres the substrate on at least one surface other than both of the front surface and an opposing surface thereof, and wherein the adhesive material does not enter into a space between the substrate and the semiconductor chip, is provided.
By this arrangement the adhesive material does not contact with a functional surface of the semiconductor chip and the above described problems are solved that the adhesive material becomes an invisible electrical circuit and it can not perform its desired function because it works as a capacitor with a harmful parasitic capacitance and that adhesive material block off the light path because it wraparound the light accepting surface (or the light emitting surface). At the same time the semiconductor chip can give the heat generated in the semiconductor chip away to environment because the adhesive material does not cover an opposite surface of the semiconductor functional surface.
In the semiconductor device according to the present invention the adhesive material is covered with adhesive material which has been cured. By this arrangement the adhesive material is prevented to flow out (prevention of flowing out) thereby the adhesive material would not enter between the functional surface of the semiconductor chip and the substrate because of flowing out of the adhesive material And at the same time a layout of the adhesive material becomes easier because an initial structure of the adhesive material is maintained.
In the semiconductor device according to the present invention a cross section of the adhesive material is a circular. By this arrangement in addition to the above described action for prevention of flowing out, the adhesive material has enough strength against internal and external pressure even before it is hardened. Also the production is easily performed.
In the semiconductor device according to the present invention a cross section of the adhesive material is a polygonal. By this arrangement in addition to the above described action for prevention of flowing out, the adhesive strength can be made higher because an adhering area between the adhesive material and the semiconductor chip and the substrate can be took wider.
In the semiconductor device according to the present invention the adhesive material is held by an adhesive material holding means. In this arrangement in addition to the above described actions that the adhesive material is prevented to contact with the functional surface of semiconductor chip and so on, the adhesive material would not wraparound between the functional surface of semiconductor and the substrate because the flowing out of adhesive material can be prevented effectively even when the adhesive material with low viscosity is utilized. According to this fact the adhesive material with low viscosity can be used as the adhesive material.
In the semiconductor device according to the present invention the adhesive material holding means is made of a sponge like material. By this arrangement the adhesive material in the supporting body can be operated with a negative pressure and by this negative pressure the adhesive material can be supported in the body.
In the semiconductor device according to the present invention the adhesive material holding means is made of an aggregated body of fibers. By this arrangement the adhesive material holding member can hold the adhesive material by means of the aggregated body of fibers.
In the semiconductor device according to the present invention the adhesive material holding means has a light transparent property. By this arrangement a photo curing type adhesive material can be used because whole surface of the held adhesive material is irradiated by a hardening light through the adhesive material supporting body.
In the semiconductor device according to the present invention the adhesive material adheres the substrate at entire circumference of surfaces other than both of the front surface and the opposing surface. By this arrangement in addition to the above described actions the problem would not occur that performance of the device can not be carried out because the adhesive material is not disposed on a light incident area and the light path of the incident light to (or outgoing light from) the semiconductor device would not block off by the adhesive material.
In the semiconductor device according to the present invention the adhesive material is a photo curing type adhesive material. By this arrangement the semiconductor chip and the substrate can be adhered to fix without any discrepancy of holding position due to thermal expansion because a rise in temperature would not almost occur when the adhesive material is cured by a light. Also it does never happen that a residual stress influenced by a temperature change in the adhering process.
In the semiconductor device according to the present invention the adhesive material is
Nakajima Mitsuru
Takemoto Hiroshi
Nguyen Dao H.
Ricoh & Company, Ltd.
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