Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
1996-03-20
2001-09-04
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S433000, C257S443000, C250S208100
Reexamination Certificate
active
06285047
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a linear image sensor IC for receiving light reflected from an irradiated original to convert it into electrical signals or an IC for thermal transfer printing. The IC may be applied to an image reader of a facsimile and the like. The present invention also relates to an IC assembling substrate on which the linear image sensor IC or the IC for thermal transfer printing is mounted and to a method for assembling the same.
DESCRIPTION OF THE RELATED ART
FIG. 2
is a block diagram of a contact type linear image sensor IC
2
used in a reader of a conventional facsimile. As shown in
FIG. 2
, a phototransistor array
21
in which a plurality of phototransistors are arrayed linearly so that the size of the array corresponds with an original in a relationship of one-to-one in the scanning direction, a switch transistor array
22
and a scanning circuit array
3
composed of a plurality of shift registers for sequentially switching each of the switch transistors are placed in strips in parallel from each other in the scanning direction. Driving circuits
4
for driving the scanning circuits are placed among pads
5
which are terminals for taking out electricity externally.
The contact type phototransistor linear image sensor described above is disclosed in Japanese Patent Laid-Open No. 61-124171.
There is also a contact type image sensor head as an IC assembling substrate in which such ICs are mounted linearly.
FIG. 38
c
is a perspective view showing such image sensor head. A plurality of image sensor ICs
2
are provided linearly on the surface of an assembling substrate
6
. Signals are supplied to the image sensor ICs by electrically connecting them with wires on the substrate by means of wire bonds
23
. The image sensor head is assembled by the following method.
As shown in
FIG. 38
a
, the image sensor ICs
2
are formed in a matrix on the surface of a silicon wafer
11
. After that, electrical characteristics of the ICs are measured by using a tester and defective chips are marked with fail marks
12
. Then, the silicon wafer
11
is cut along scribe lines to separate each of the ICs. Next, only good chips are selected and are placed on a tray
13
as shown in
FIG. 38
b
. Then, they are placed sequentially on the surface of the assembling substrate
6
from the tray
13
and are wire-bonded as shown in
FIG. 38
c
, thus completing the head.
FIG. 40
is a plan view of the IC to be mounted on the IC assembling substrate. Formed on the IC
2
are four or more pads
5
which are power supply, signal supply and output terminals. Further, a plurality of light receiving elements
32
each having the identical shape and composed of a phototransistor or a photodiode are placed periodically along the longitudinal direction of the chip. The light receiving elements
32
are provided linearly along the scanning direction with the period of reading pitch. Charge accumulated in the light receiving elements is output from the output terminal sequentially from the leftmost light receiving element. As it is apparent from
FIG. 40
, the array of the light receiving elements
32
and that of the pads
5
are placed separately.
FIG. 70
a
is a plan view of a multi-chip type image sensor in an image reader of a facsimile and
FIG. 70
b
is a section view thereof. A plurality of image sensor ICs
2
having about 8 mm of length are placed in a line side by side on the surface of a substrate
14
on which wires are printed. To read an original of A4 size paper by the contact type image sensor, it is necessary to place the plurality of ICs
2
by a length equal to a width of the paper. The substrate
14
is electrically connected with each of the image sensor ICs
2
by a bonding lead wire
23
as shown in
FIG. 70
b
. The image sensor IC
2
is so thin as to have only about 0.6 mm of width. Photosensors are formed on the image sensor IC
2
along the longitudinal direction thereof with a reading period.
A thermal head of an output section of the facsimile is also constructed in the same manner. In the case of the thermal head, thermal head driver ICs are placed in a line in the same manner with the image sensor IC
2
. While each of the IC are placed having almost no gap therebetween in the case of the image sensor, each of the ICs are placed in a line at certain intervals in the case of the thermal head. Thermal resistors are provided on the surface of the substrate
14
and current is flown to each resistor via wires and a bonding lead line on the substrate
14
. The resistors are provided linearly with a density of about 64 pieces/8 mm and a thermosensible paper is printed and output by changing color thereof by Joule heat. Accordingly, 64 driver transistors are provided in each driver IC along the longitudinal direction of the IC. Each driver transistor is provided with an output pad electrically connected. Accordingly, 64 output pads are placed in a line and bonding-connected along the longitudinal direction of the IC of about 8 mm in length at intervals of about 10 &mgr;m.
However, it has been difficult to lower the cost of such linear image sensor because the chip size cannot be reduced simply like a normal memory IC. That is, the length of the chips in the scanning direction cannot be reduced because the length has to be equal to a width of an original. Further, the width of the chip in the direction vertical to the scanning direction could be reduced only around to 0.7 mm because the sensors, switches, scanning circuits and driving circuits are all placed in parallel.
It has been also difficult to lower the cost of such IC assembling substrate because the length of the ICs cannot be shortened in principle. There arises another problem if the width of the IC is thinned that good chips are marked with a fail mark because a size of the fail mark is large and the positioning accuracy is low. Still more, because the ICs are flat in general, they could not be assembled on a cylindrical assembling substrate.
Further, those chips could not be measured by two chips each in the same time. If it could, it would contribute in lowering the IC assembling cost in testing electrical characteristics of the ICs in manufacturing such IC assembling substrate. That is, if the ICs adjoining in the direction vertical to the direction in which IC pixels are arrayed are tested by probing by two chips each in the same time, light receiving elements of either one of those two chips are shaded by a probing needle and homogeneous light cannot be irradiated to the light receiving element array because all the ICs are placed in the same orientation. Accordingly, because the quality of the chips cannot be accurately determined, it has been difficult to test two chips in the same time.
The image sensor IC has had another problem that sensitivity of the light receiving elements fluctuates within the silicon wafer. It is considered to be caused by an uneven heat distribution within the wafer surface in the IC manufacturing process or by an uneven thickness of various insulating films and the sensitivity tends to change continuously within the wafer. Accordingly, a difference of the sensitivity of the light receiving elements may become small if they are close from each other on the wafer and may become large if they are distant from each other. For instance, if the light receiving elements on the right hand side in
FIG. 40
have higher sensitivity and when ICs are mounted sequentially on the assembling substrate
6
so as to adjoin each other in the direction vertical to the direction in which the light receiving elements of the IC
2
are placed in a line, an output of the assembling substrate
6
when uniform light is irradiated thereon turns out as shown in FIG.
44
.
FIG. 44
shows an output waveform of the prior art image sensor head having six IC chips. As shown in the figure, the inclination of the output is always right-up because the orientation of the adjoining IC chips has been the same on the wafer. Accordingly, there is a difference of level of th
Ando Noritoshi
Kawahara Yukito
Kojima Yoshikazu
Machida Satoshi
Yokomichi Masahiro
Crane Sara
Hogan & Hartson LLP
Seiko Instruments Inc.
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