Image reading apparatus and circuit board unit used therefor

An image reading apparatus (X) includes a light source, a case (2) for accommodating the light source, and a substrate (8) mounted to the case (8). A plurality of sensor IC chips (7) for detecting the light traveling from an image reading region are mounted on the substrate (8). The sensor IC chips (7) are arranged at positions closer to a second side edge (8b) than to a first side edge (8a) of the substrate. A predetermined wiring pattern is formed on the substrate (8). The sensor IC chips (7) are electrically connected to the wiring pattern via wires (W). The wires (W) are connected to the wiring pattern by extending from the upper surface of the sensor IC chips (7) toward the first side edge (8a) of the substrate.

TECHNICAL FIELD

The present invention relates to an image reading apparatus used for reading an image printed on a document, for example. The present invention also relates to a circuit board unit used for manufacturing an image reading apparatus.

BACKGROUND ART

FIG. 6of the present application shows an example of prior-art image reading apparatus. The illustrated image reading apparatus includes a substrate100, and a case200to which the substrate is mounted. The substrate has a rectangular configuration elongated in a direction perpendicular to the sheet surface of the figure. The substrate100has an upper surface on which a plurality of light sources101and a plurality of sensor IC chips102are mounted. The light sources101are aligned along a first side edge100aof the substrate100with predetermined intervals. The sensor IC chips102aligned along a second side edge100bof the substrate100. Each of the sensor IC chips102has an upper surface formed with a light receiving portion102a.

The case200is formed with a light path201for guiding the light emitted from the light sources101to an image reading region S. A lens array comprising a plurality of lenses105is disposed below the image reading region S. The light reflected by the image reading region S is converged by the lenses105and received by the light receiving portion102aof each sensor IC chip102.

Each sensor IC chip102has the photoelectric conversion function and outputs an image signal of the level corresponding to the received amount of light. To obtain an image signal faithful to the object to be read, the light emitted from the light sources101need be prevented from directly reaching the light receiving portion102a. For this purpose, a partition wall202is provided between the light sources101and the sensor IC chips102. The partition wall202engages the upper surface of the substrate100and extends in the longitudinal direction of the substrate100.

As indicated by double-dashed lines inFIG. 6, a connector103for external connection is attached to the substrate100. The connector103is connected to a wiring pattern (not shown) formed on the upper surface of the substrate100. The wiring pattern is connected to the light sources101and the sensor IC chips102. Such an image reading apparatus is disclosed in JP-A 2001-339574, for example.

In the image reading apparatus ofFIG. 6, the wiring pattern is connected to each IC chip102via a wire W. Specifically, the upper end of the wire W is connected to the IC chip102, whereas the lower end of the wire is connected to the wiring pattern.

The prior-art structure has the following drawbacks. As shown inFIG. 6, the lower end of the wire W is connected to the wiring pattern on the right side of the chip102(adjacent the second side edge100b). With such an arrangement, in mounting the substrate100to the case200, the operator's hand or the case200is likely to come into contact with the wire W. When such contact occurs, the wire W may be broken or the connection between the wire W and the chip102or the wiring pattern may fail.

DISCLOSURE OF THE INVENTION

The present invention is conceived under such circumstances. It is, therefore, an object of the present invention to provide an image reading apparatus in which improper external force is not exerted to the wires connecting the wiring pattern and the sensor IC chips on the substrate to each other. Another object of the present invention is to provide a circuit board unit used for manufacturing such an image reading apparatus.

According to a first aspect of the present invention, there is provided an image reading apparatus comprising: a light source for illuminating an image reading region extending in a primary scanning direction; a case for accommodating the light source; a substrate including a first side edge and a second side edge spaced from each other in a secondary scanning direction which is perpendicular to the primary scanning direction, the substrate being mounted to the case; a plurality of sensor IC chips for detecting light traveling from the image reading region, the sensor IC chips being mounted on a principal surface of the substrate at positions closer to the second side edge than to the first side edge; a wiring pattern formed on the substrate; and a plurality of wires electrically connecting the sensor IC chips and the wiring pattern to each other. Each of the wires is connected to the wiring pattern by extending from a corresponding one of the sensor IC chips toward the first side edge of the substrate.

Preferably, the image reading apparatus of the present invention further comprises a light guide for guiding the light emitted from the light source to the image reading region. The case is provided with a partition wall for separating the light guide and the sensor IC chips, and the partition wall is spaced from the substrate.

Preferably, the light guide is made of transparent resin.

Preferably, the partition wall includes a flat surface extending parallel to the principal surface of the substrate, and the wires enter between the flat surface and the principal surface of the substrate at least partially.

Preferably, the image reading apparatus of the present invention further comprises a reflector held in contact with the light guide to prevent light from leaking from the light guide. The reflector is provided on the partition wall.

Preferably, the plurality of sensor IC chips are arranged in a straight row. The wiring pattern includes a conductive path which extends across the row of the sensor IC chips and a conductive path which does not extend across the row of the sensor IC chips.

Preferably, each of the sensor IC chips is provided with a plurality of connection pads, and a plurality of light receiving portions arranged in a straight row. The connection pads are arranged at positions offset toward the first side edge of the substrate with respect to the light receiving portions.

Preferably, the image reading apparatus of the present invention further comprises a connector for external connection attached to the first side edge of the substrate. The connector is electrically connected to the wiring pattern.

According to a second aspect of the present invention, there is provided a circuit board unit comprising: a substrate including a first side edge and a second side edge spaced from each other; a plurality of sensor IC chips mounted on the substrate at positions closer to the second edge than to the first edge; a wiring pattern formed on the substrate; and a plurality of wires electrically connecting the sensor IC chips and the wiring pattern to each other. Each of the wires is connected to the wiring pattern by extending from a corresponding one of the sensor IC chips toward the first side edge of the substrate.

Preferably, each of the sensor IC chips is provided with a plurality of connection pads, and a plurality of light receiving portions arranged in a straight row. The connection pads are arranged at positions offset toward the first side edge of the substrate with respect to the light receiving portions.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 through 4show an example of image reading apparatus according to the present invention. As will be understood fromFIG. 1, the image reading apparatus X includes a case2, a light guide3, a reflector4, a transparent plate5, a lens array6and a circuit board unit U. The unit U includes a rectangular substrate8elongated in the primary scanning direction (See the arrow A inFIG. 1), and various elements (which will be described later) provided on the substrate.

The substrate8has a principal surface (upper surface)81on which a light source unit1and a plurality of sensor IC chips7are mounted. The substrate8includes two side edges extending in the primary scanning direction, i.e., a first side edge8aand a second side edge8b.

The light source unit1serves to illuminate an image reading region S (SeeFIG. 3). In the illustrated example, the light source unit1comprises three kinds of light emitting diodes, i.e., a red diode, a green diode and a blue diode (SeeFIG. 4). As shown inFIG. 1, the light source unit1is provided at an end of the substrate8. Further, as shown inFIG. 4, the light source unit4is close to the first side edge8athan to the second side edge8b.

The case2is made of a synthetic resin and has a lower surface on which the substrate8is mounted. As shown inFIG. 2, the case2includes a first space21for accommodating the light source unit1. As shown inFIGS. 2-4, the case2further includes a second space22for accommodating the sensor IC chips7, and a third space23for accommodating the light guide3and the reflector4. The first space21and the second space22are separated by a first partition wall24of the case2(SeeFIG. 2). The second space22and the third space23are separated by a second partition wall25(SeeFIGS. 2 and 3). The second partition wall25is spaced from the substrate8and provided above the substrate. The first and the second partition walls24and25are provided to block the light directly traveling toward the sensor IC chips7from the light source unit1. As shown inFIG. 3, the second partition wall25has a flat surface25aextending parallel to the principal surface81of the substrate8. The wire W enters between the flat surface25aand the principal surface81of the substrate8at least partially.

The light guide3is transparent and may be made of polymethyl methacrylate (PMMA), for example. As shown inFIG. 2, the light guide3extends in the longitudinal direction of the case2and includes an auxiliary portion31and a main portion32. The auxiliary portion31has a light incident surface31afacing the light source unit1. The light impinging on the light incident surface31atravels through the auxiliary portion31to enter the main portion32. As shown in the figure, the light traveling through the main portion32is totally reflected by the surfaces of the main portion32. The lower surface of the main portion32is formed with a plurality of recesses (not shown) arranged with predetermined intervals. The light traveling through the main portion21is scattered and reflected by the recesses and partially emitted toward the image reading region S through a light emission surface32a(SeeFIG. 3). The image reading region S is irradiated with the emitted light.

The reflector4is made of a synthetic resin and is made white to increase the light reflectance. The reflector4includes an accommodation portion41for accommodating the light guide3. The reflector4covers the light guide3except the light incident surface31aand the light emission surface32ato prevent the waste of light due to leaking from the light guide3. As shown inFIGS. 2 and 3, the reflector4is disposed on the second partition wall25.

The transparent plate5is made of a synthetic resin or glass and mounted on the upper surface of the case2. The transparent plate5comes into contact with the document D which slides thereon by the transfer by the platen roller P in the secondary scanning direction (the direction indicated by the arrow B inFIGS. 3 and 4). The secondary scanning direction is perpendicular to the primary scanning direction.

As shown inFIGS. 3 and 4, the lens array6is arranged between the second space22and the third space23of the case2. The lens array6includes a holder61made of a synthetic resin and extending in the primary scanning direction, and a plurality of lenses62held by the holder. The above-described image reading region S is located directly above the lenses62and on the upper surface of the transparent plate5.

As shown inFIG. 5, each of the sensor IC chips7comprises an elongated rectangular semiconductor device. The plurality of sensor IC chips7are aligned in the longitudinal direction of the substrate8. The sensor IC chips7are located closer to the second side edge8bthan to the first side edge8a. Therefore, with the sensor IC chips7serving as the boundary, the upper surface81of the substrate8is partitioned into two regions of different widths, i.e., a first region81aand a second region81b. As will be understood from the figure, the first region81ais located on the side of the first side edge8aof the substrate and is larger in area (width) than the second region81b(located on the side of the second side edge8b).

Each of the sensor IC chips7has a plurality of light receiving portions71. The light receiving portions receive light passed through the lens array6. The sensor IC chip7has the photoelectric conversion function and outputs an image signal of an output level corresponding to the received amount of light.

As shown inFIG. 5, a plurality of conductive pads72are provided on the upper surface of the sensor IC chip7. The pads72are arranged at positions offset toward the first side edge8awith respect to the center of the sensor IC chip7in the width direction (vertical direction inFIG. 5). These pads72include pads72(Vcc, VREF) for voltage application, a pad72(GND) for ground connection and pads72(CLK, SI, SP, AO, SO) for inputting or outputting various kinds of signals. In the sensor IC chip7, when a serial-in-signal is inputted into the pad72(SI), the charge stored in the light receiving portions71is discharged. The discharged charge is serially outputted from the pad72(AO).

The substrate8is made of e.g. a ceramic material, and a connector10for external connection is attached to the first side edge8a(SeeFIG. 1). The connector10is electrically connected to the light source unit1and the sensor IC chips7through a wiring pattern9. The wiring pattern9comprises a plurality of conductive paths corresponding to the pads72. Each of the conductive paths is connected to the corresponding pad72via a wire W. The upper end of each wire W is connected to the corresponding pad, whereas the lower end of the wire is connected to the corresponding conductive path. The connection point between the lower end of the wire W and the conductive path is located in the first region81a. Thus, all the wires S are connected to the wiring pattern9by extending from the corresponding pads72toward the first side edge8a. The conductive paths for the pads72(GND, AO, VREF) extend in both of the first region81aand the second region81b. Therefore, the conductive paths for the pads GND, AO and VREF extend across the chip7below the sensor IC chip7. The conductive paths for other pads72(Vcc, CLK, SI, SP, SO) are provided in the first region81aand do not extend into the second region81b. (Although these conductive paths are partially located below the chip7, the paths do not extend into the second region81b.)

As described above, in the image reading apparatus X of the present invention, the wires W extend from the sensor IC chip7toward the first side edge8a. Therefore, in mounting the substrate8to the case2, the operator's hand does not come into contact with the wires W. Further, as shown inFIG. 3, the second partition wall25of the case2is spaced from the substrate1and provided above the substrate, so that the contact between the wires W and the case2can be avoided. With such a structure, the prior-art problems such as the breakage of wires W or the connection failure can be solved. Moreover, in the example shown inFIG. 3, the case2includes an inclined wall surface2afacing the sensor IC chips7. The wall surface2aextends in a direction perpendicular to the sheet surface of the figure. With such an arrangement, the contact between the case2and the chips7can be avoided.

Further, in the image reading apparatus X, the wires W extend from the sensor IC chip7to the side of the first side edge8aand connected to the wiring pattern9in the first region81a. With such a structure, at least part of the conductive paths connected to the sensor IC chip7is only required to be formed at the first region81a. As a result, the structure of the wiring pattern9can be made simpler than the prior-art wiring pattern, whereby the manufacturing cost can be reduced.

The present invention being thus described, it is apparent that the same may be varied in many ways. Such variations should not be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to those skilled in the art are intended to be included within the scope of the following claims.