U.S. patent application number 11/537951 was filed with the patent office on 2007-04-19 for component of a radiation detector comprising a substrate with positioning structure for a photoelectric element array.
This patent application is currently assigned to NIHON KESSHO KOGAKU CO., LTD.. Invention is credited to Shigenori SEKINE, Toshikazu Yanada.
Application Number | 20070085088 11/537951 |
Document ID | / |
Family ID | 27346515 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070085088 |
Kind Code |
A1 |
SEKINE; Shigenori ; et
al. |
April 19, 2007 |
COMPONENT OF A RADIATION DETECTOR COMPRISING A SUBSTRATE WITH
POSITIONING STRUCTURE FOR A PHOTOELECTRIC ELEMENT ARRAY
Abstract
In the component of a radiation detector, an upper end face of a
pad formation protrusion provided on an upper surface of an MID
substrate is equal in height to an upper surface of a photodiode
array, first pads are provided on upper surfaces of photodiodes
arranged in the photodiode array, respectively, second pads are
provided on the upper end face of the pad formation protrusion, a
bonding wire is provided between one of the first pads and
corresponding one of the second pads, a wiring pattern is provided
on the upper surface of the MID substrate, first terminals as many
as the second pads and one second terminal are provided on a lower
surface of the MID substrate, the second pads and the first
terminals are electrically connected to one another in a one-to-one
correspondence, and the wiring pattern is electrically connected to
the second terminal.
Inventors: |
SEKINE; Shigenori; (Gunma,
JP) ; Yanada; Toshikazu; (Gunma, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
NIHON KESSHO KOGAKU CO.,
LTD.
GUNMA
JP
|
Family ID: |
27346515 |
Appl. No.: |
11/537951 |
Filed: |
October 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10893906 |
Jul 20, 2004 |
|
|
|
11537951 |
Oct 2, 2006 |
|
|
|
10109871 |
Apr 1, 2002 |
6844570 |
|
|
10893906 |
Jul 20, 2004 |
|
|
|
Current U.S.
Class: |
257/80 |
Current CPC
Class: |
H01L 2924/12032
20130101; H01L 2224/48227 20130101; H01L 2924/09701 20130101; H01L
2924/01079 20130101; H01L 27/14661 20130101; H01L 27/14663
20130101; H01L 2924/01078 20130101; G01T 1/2018 20130101; H01L
2924/12032 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/080 |
International
Class: |
H01L 33/00 20060101
H01L033/00; H01L 31/12 20060101 H01L031/12; H01L 27/15 20060101
H01L027/15; H01L 29/26 20060101 H01L029/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 11, 2001 |
JP |
2001-112715 |
Jun 28, 2001 |
JP |
2001-196596 |
Jan 25, 2002 |
JP |
2002-016677 |
Claims
1. A radiation detector comprising: a component of a radiation
detector including a scintillator array; a photodiode array
arranged on one side surface of the scintillator array in an array
aligned direction; and wirings electrically connected to
photodiodes of the photodiode array, respectively, and arranged on
a surface of the photodiode array, wherein a terminal end of each
of the wirings is present downstream of a contact section with the
scintillator array in a light receiving direction; and a substrate
supporting the component of a radiation detector; and a wiring
provided on the substrate, wherein the wiring on the substrate is
electrically connected to a terminal end of each of wirings
arranged on a surface of the photodiode array.
2. A radiation detector comprising: a component of a radiation
detector including a scintillator array; a photodiode array
arranged on one side surface of the scintillator array in an array
aligned direction; and wirings electrically connected to
photodiodes of the photodiode array, respectively, and arranged on
a surface of the photodiode array, wherein each of the wirings
extends toward downstream of a contact section with the
scintillator array in a light receiving direction and then extends
in the array aligned direction of the scintillator array; and a
terminal end of each of the wirings is present on a lateral
position exceeding the contact section with the scintillator array;
and a substrate supporting the component.
3. A component of a radiation detector comprising: a scintillator
array; a photodiode array arranged on one side surface of the
scintillator array in an array aligned direction; and wirings
electrically connected to photodiodes of the photodiode array,
respectively, and arranged on a surface of the photodiode array,
wherein each of the wirings extends toward downstream of a contact
section with the scintillator array in a light receiving direction
and then extends in the array aligned direction of the scintillator
array; and a terminal end of each of the wirings is present on a
lateral position exceeding the contact section with the
scintillator array.
Description
[0001] This application is a divisional application of U.S.
application Ser. No. 10/893,906 filed Jul. 20, 2004, which is a
divisional of application of U.S. application Ser No. 10/109,871
filed Apr. 1, 2002, which claims benefit of and priority to
Japanese Patent Application Nos. 2001-112715 filed Apr. 11, 2001,
2001-196596 file Jun. 28, 2001 and 2002-016677 filed Jan. 25, 2002,
which are incorporated herein by reference in their entireties for
all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a component of a radiation
detector, a radiation detector, and radiation detection
apparatus.
BACKGROUND OF THE INVENTION
[0003] An X-ray CT system used in a medical institution or the like
photographs the internal structure of a subject by applying an
X-ray to the subject. Specifically, the x-ray CT system includes an
X-ray irradiation source and a radiation detector which is arranged
to be opposed to the X-ray irradiation source through a subject and
which has an X-ray detection section arranged in a one-dimensional
array. The detection section functions to convert a received X-ray
into an electrical signal and includes a scintillator which
converts the X-ray into a visible light beam and a photodiode which
converts the visible light beam into an electrical signal. This
radiation detector receives the X-ray which passes through the
subject and records the electrical signal obtained based on the
received X-ray. While maintaining the positional relationship
between the X-ray irradiation source and the radiation detector,
the X-ray CT system variously changes an X-ray irradiation angle
and repeatedly receives X-rays. The X-ray CT system then conducts
processings such as convolution and back-projection to the
electrical signals thus obtained, thereby reconstructs the images
of the cross-sections (which will be referred to as "slices"
hereinafter) of the subject through which the X-rays pass.
[0004] Recently, in particular, the development of a multi-slice
X-ray CT system which can simultaneously photograph a plurality of
slices by one X-ray irradiation is actively underway. The
multi-slice X-ray CT system has a plurality of X-ray detection
sections, each of which is in the form of an array, which are
arranged to correspond to a plurality of slices, respectively,
collects X-rays which pass through the respective slices and
reconstructs slice images. The multi-slice X-ray CT system is,
therefore, required to include a radiation detection apparatus in
which each detection section is arranged not in a one-dimensional
array but in a two-dimensional array. Photodiodes which constitute
each detection section should be arranged two-dimensionally,
accordingly.
[0005] A conventional radiation detector shown in FIG. 24A
("conventional art 1") is formed by arranging a plurality of
single-slice one-dimensional photodiode arrays 102 in parallel on a
substrate 101, arranging photodiodes 103 two-dimensionally, and
mounting two-dimensional scintillator arrays each having
scintillator elements corresponding to the photodiodes on the
photodiodes 103, respectively. The first pad 104 of each photodiode
103 is electrically connected to the second pad 105 which is
provided on the substrate 101 by a bonding wire 106. An electrical
signal output from each photodiode 103 is propagated on-a wiring
provided on the substrate 101 and output to the outside of the
substrate 101.
[0006] There is also known a structure in which a plurality of
photodiodes distributed in a matrix and wirings corresponding to
the photodiodes are integrally formed on a single semiconductor
substrate (which structure will be referred to as "conventional art
2" hereinafter). A radiation detector is formed by mounting a
two-dimensional scintillator array which includes scintillators
corresponding to the respective photodiodes, on the semiconductor
substrate on which the photodiodes are thus incorporated.
[0007] The conventional art 1 has the following disadvantages.
First, according to the conventional art 1, the one-dimensional
photodiode arrays 102 are arranged on the plane substrate 101. A
difference in height is, therefore, disadvantageously generated
between second pads 105 provided on the substrate 101 and the
photodiodes 103 by as much as the thickness of each photodiode
array 102. If the bonding wires 106 are provided in a state in
which such difference is generated, it is necessary to separate the
position of each second pad 105 from each photodiode 103 by a
predetermined distance in horizontal direction as shown in FIG.
24B. If the position of the second pad 105 is thus separated from
the photodiode 103, however, the distance between the photodiode
arrays 102 widens. As a result, an area occupied by the photodiodes
relative to the entire radiation detector becomes small and the
X-ray receiving sensitivity of the detector disadvantageously
deteriorates.
[0008] In addition, It is necessary to accurately locate the
one-dimensional photodiode arrays 102 on the substrate 101. To
manufacture such a radiation detector as the conventional art 1,
therefore, it is disadvantageously necessary to newly provide a
mounting device which fixes the one-dimensional photodiode arrays
onto the substrate 101 or to use a special positioning tool.
[0009] Moreover, since the conventional art 1 has a structure in
which the two-dimensional scintillator arrays are directly arranged
on the plural one-dimensional photodiode arrays 102, the
conventional art 1 has disadvantages of a small contact area and
lowered mechanical strength.
[0010] The conventional art 2 has disadvantages, as well. All the
photodiodes are mounted on the single semiconductor substrate. For
that reason, if even one defective photodiode exists among the
photodiodes which constitute the two-dimensional photodiode array,
the radiation detector cannot be formed, with the result that the
other photodiodes mounted on the semiconductor substrate must be
abandoned. The individual photodiodes which constitute the
two-dimensional photodiode array are required to be arranged
two-dimensionally. A redundant circuit as employed in a DRAM cannot
be, therefore, used and yield is disadvantageously quite low with
the structure of the conventional art 2.
[0011] Further, the conventional art 2 has a structure in which
necessary wirings are also mounted on the semiconductor substrate.
These wirings are provided to correspond to the photodiodes,
respectively. Therefore, as the number of the photodiodes
increases, that of the wirings increases. If the number of slices
increases, in particular, the number of wirings necessary to output
electrical signals to the outside of the substrate increases. To
suppress a decrease in an area occupied by the photodiodes on the
semiconductor substrate, it is necessary to narrow the width of
each wiring. However, if the wirings are narrower, electrical
resistance disadvantageously increases and the probability of
breaking the wirings disadvantageously increases.
[0012] It is noted that some of these disadvantages explained above
are not limited to the multi-slice radiation detector but seen in a
single-slice radiation detector. If one-dimensional photodiode
arrays are arranged on a substrate, for example, the difference in
height between pads and photodiodes is disadvantageously
generated.
[0013] Moreover, these disadvantages occur not only to the
radiation detector but also ordinary photo-detectors. Normally, a
photo-detector has a structure of the radiation detector from which
scintillators are excluded and the same as the radiation detector
in that the two-dimensional photodiodes are arranged. To improve
the light receiving sensitivity of the photo-detector, it is
preferable that an area occupied by the photodiodes on the
substrate is large. However, because of the same disadvantages as
those explained above, there is no avoiding narrowing the light
receiving area.
SUMMARY OF THE INVENTION
[0014] It is an object of the present invention to provide a
component of a radiation detector, a radiation detector and a
radiation detection apparatus which can maintain the percentage of
an area occupied by photodiodes high on a plane on which the
photodiodes are arranged and which can be easily manufactured.
[0015] The component of a radiation detector according to one
aspect of the present invention comprises a substrate, a
photoelectric element arranged on a portion on an upper surface of
the substrate and having a first pad on a light receiving surface,
the photoelectric element generating an electrical signal based on
an intensity of received light, a pad formation section arranged on
a portion on the upper surface of the substrate and different from
the portion on which the photoelectric element is arranged, and a
second pad formed on the pad formation section, arranged to form a
same plane as a plane of the first pad arranged on the light
receiving surface of the photoelectric element, and electrically
connected to the first pad.
[0016] The component of a radiation detector according to another
aspect of the present invention comprises an MID substrate and a
photodiode array provided to contact with the MID substrate, a pad
formation protrusion provided on an upper surface of the MID
substrate on a side contacting with a lower surface of the
photodiode array, an upper end face of the pad formation protrusion
being equal in height to an upper surface of the photodiode array,
first pads provided on upper surfaces of photodiodes of the
photodiode array, respectively in a section adjacent the pad
formation protrusion, second pads provided on the upper end face of
the pad formation protrusion in a section adjacent the first pad, a
boding wire provided between one of the first pads and
corresponding one of the second pads, a wiring pattern provided on
the upper surface of the MID substrate contacting with the
photodiode array, first terminals as many as the second pads and
one second terminal provided on a lower surface of the MID
substrate, wherein the second pads and the first terminals are
electrically connected to one another in a one-to-one
correspondence, and the wiring pattern is electrically connected to
the second terminal.
[0017] The component of a radiation detector according to still
another aspect of the present invention comprises an MID substrate
and a plurality of photodiodes provided to contact with the MID
substrate, a positioning groove or protrusion which is provided on
an upper surface or the MID substrate on a side contacting with
lower surfaces of the photodiodes, and which positions the
photodiodes, a pad formation protrusion provided on the upper
surface of the MID substrate, an upper end face of the pad
formation protrusion being equal in height to upper surfaces of the
photodiodes, first pads provided on the upper surfaces of the
photodiodes, respectively in sections adjacent the pad formation
protrusion, second pads provided on the upper end face of the pad
formation protrusion in sections adjacent the first pads,
respectively, a boding wire provided between one of the first pads
and corresponding one of the second pads, a wiring pattern provided
on the upper surface of the MID substrate contacting with the
photodiodes, first terminals as many as the second pads and one
second terminal provided on a lower surface of the MID substrate,
wherein the second pads and the first terminals are electrically
connected to one another in a one-to-one correspondence, and the
wiring pattern is electrically connected to the second
terminal.
[0018] The component of a radiation detector according to still
another aspect of the present invention comprises a scintillator
array, a photodiode array arranged on one side surface of the
scintillator array in an array aligned direction, and wirings
electrically connected to photodiodes of the photodiode array,
respectively, and arranged on a surface of the photodiode array. A
terminal end of each of the wirings is present downstream of a
contact section with the scintillator array in a light receiving
direction.
[0019] The component of a radiation detector according to still
another aspect of the present invention comprises a scintillator
array, a photodiode array arranged on one side surface of the
scintillator array in an array aligned direction, and wirings
electrically connected to photodiodes of the photodiode array,
respectively, and arranged on a surface of the photodiode array.
Each of the wirings extends toward downstream of a contact section
with the scintillator array in a light receiving direction and then
extends in the array aligned direction of the scintillator array;
and a terminal end of each of the wirings is present on a lateral
position exceeding the contact section with the scintillator
array.
[0020] The component of a radiation detector according to still
another aspect of the present invention comprises an embedding
groove section provided on a part of a substrate; a photoelectric
element array which includes a plurality of photoelectric elements
arranged in a one-dimensional array, and which is embedded into the
embedding groove section, a first pad arranged on each of light
receiving surfaces of the photoelectric elements, and a second pad
provided on the substrate to correspond to the first pad, and
electrically connected to the first pad.
[0021] The radiation detector according to still another aspect of
the present invention comprises the above mentioned component, and
a converter arranged on a light receiving surface of the
photoelectric element, and converting a received radiation ray into
a light beam in a wavelength band which the photoelectric element
can convert into an electrical signals
[0022] The radiation detector according to still another aspect of
the present invention comprises the above mentioned component, and
a scintillator array which is provided on an upper surface of a
photodiode array of the component, and which has scintillators
provided to correspond to photodiodes of the photodiode array,
respectively.
[0023] The radiation detector according to still another aspect of
the present invention comprises the above mentioned component, and
scintillators which are provided on upper surfaces of photodiodes
of the component to correspond to the photodiodes,
respectively.
[0024] The radiation detector according to still another aspect of
the present invention comprises the above mentioned component, and
a wiring provided on the substrate, wherein the wiring on the
substrate is electrically connected to a terminal end of each of
wirings arranged on a surface of the photodiode array.
[0025] The radiation detector according to still another aspect of
the present invention comprises the above mentioned component, and
a substrate supporting the component.
[0026] The radiation detection apparatus according to still another
aspect of the present invention comprises the above mentioned a
predetermined number of above-mentioned radiation detectors
arranged crosswise.
[0027] Other objects and features of this invention will become
apparent from the following description with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a schematic perspective view of a component of a
radiation detector in a first embodiment in a state in which an MID
substrate is separated from a photodiode array,
[0029] FIG. 2 is a cross-sectional view taken along line I-I shown
in FIG. 1,
[0030] FIG. 3A is a schematic perspective view of the component of
a radiation detector in the first embodiment in a state in which
the MID substrate and the photodiode array are assembled together,
and FIG. 3B is a cross-sectional view which shows the manner of the
electrical connection of the photodiode array in the assembled
state,
[0031] FIG. 4 is a schematic perspective view of a radiation
detector in a second embodiment in a state in which a component of
a radiation detector is separated from a scintillator array,
[0032] FIG. 5 is a schematic perspective view of the radiation
detector in the second embodiment in a state in which the component
of a radiation detector and the scintillator array are assembled
together,
[0033] FIG. 6 is a schematic perspective view which shows the
structure of a radiation detection apparatus in a third
embodiment,
[0034] FIG. 7 is a schematic perspective view of the radiation
detection apparatus in the third embodiment in which collimators
are additionally arranged,
[0035] FIG. 8A is a schematic perspective view of a component of a
radiation detector in a fourth embodiment in a state in which a
photodiode array is separated from a scintillator array, and FIG.
8B is a schematic perspective view which shows a state in which the
component of a radiation detector is assembled,
[0036] FIG. 9 is a schematic cross-sectional view which shows the
structure of a radiation detector in a fifth embodiment,
[0037] FIG. 10 is a schematic cross-sectional view which shows the
structure of a modification of the radiation detector in the fifth
embodiment,
[0038] FIG. 11 is a schematic perspective view which shows the
structure of a radiation detection apparatus in the fifth
embodiment,
[0039] FIG. 12 is a schematic perspective view of a radiation
detector in a sixth embodiment in a state in which a photodiode
array is separated from a scintillator array,
[0040] FIG. 13 is a schematic perspective view which shows the
structure of the radiation detector in the sixth embodiment,
[0041] FIG. 14 is a schematic perspective view which shows the
structure of a radiation detection apparatus which employs the
radiation detectors in the sixth embodiment,
[0042] FIG. 15A and FIG. 15B are schematic cross-sectional views of
the radiation detection apparatus obtained in the embodiments,
[0043] FIG. 16 is a schematic perspective view of a radiation
detection apparatus in the seventh embodiment in a state in which a
two-dimensional scintillator array is separated,
[0044] FIG. 17 is a schematic cross-sectional view which shows the
schematic of electrical connection in the radiation detection
apparatus in a seventh embodiment,
[0045] FIG. 18 is a schematic top view which shows the structure of
a substrate in the radiation detection apparatus in the seventh
embodiment,
[0046] FIG. 19 is a schematic cross-sectional view which shows the
operation of the radiation detection apparatus in the seventh
embodiment,
[0047] FIG. 20 is a schematic cross-sectional view which shows the
structure of a radiation detection apparatus in a eighth
embodiment,
[0048] FIG. 21 is a schematic perspective view which shows the
structure of a radiation detection apparatus in a ninth
embodiment,
[0049] FIG. 22 is a schematic cross-sectional view which shows the
operation of the radiation detection apparatus in the ninth
embodiment,
[0050] FIG. 23 is a schematic top view which shows the structure of
a radiation detection apparatus in a modification of the ninth
embodiment, and
[0051] FIG. 24A is a schematic perspective view which shows the
structure of a radiation detection apparatus according to
conventional art, and FIG. 24B is a schematic cross-sectional view
which shows the manner of the electrical connection of the
radiation detection apparatus according to the conventional
art.
DETAILED DESCRIPTIONS
[0052] The present invention relates to a technique of outputting
an electrical signal based on the intensity of a light beam
received by each photoelectric element arranged on a partial region
on an upper surface of a substrate and having the first pad on a
light receiving surface thereof and each of which. More
specifically, this invention relates to a component of a radiation
detector, a radiation detector and a radiation detection apparatus
which can maintain a percentage of an area occupied by
photoelectric elements on a plane, on which the photoelectric
elements are arranged, to be high and which can be easily
manufactured.
[0053] Embodiments of the present invention will be explained
hereinafter with reference to the drawings. Same or similar
sections are detected by the same or similar reference symbols
throughout the drawings. It should be noted, however, that the
drawings are only typical ones and that the relationship between
the thickness and the width of each section, the proportions of
thickness of each section and the like differ from actual ones.
Needless to say, some sections differ in the relationship of
dimensions and rates among the drawings.
[0054] A component of a radiation detector in a first embodiment
will first be explained. FIG. 1 is a schematic perspective view of
a component of a radiation detector in the first embodiment in a
state in which an MID (Molded Interconnected Device) substrate 1
and a photodiode array are separated from each other. FIG. 2 is a
cross-sectional view taken along line I-I shown in FIG. 1. FIG. 3A
is a schematic perspective view of the component of a radiation
detector in the first embodiment in a state in which the MID
substrate 1 and the photodiode array 2 are assembled together. FIG.
3B is a cross-sectional view which explains the electrical
connection of the photodiode array 2 in the assembled state.
[0055] As shown in FIGS. 1 to 3, the component of a radiation
detector in the first embodiment includes the MID substrate 1 which
is three-dimensionally formed and on which three-dimensional
wirings are provided, and the photodiode array 2 which is provided
in contact with the MID substrate 1. A pad formation protrusion 3
is provided on the upper surface of the MID substrate 1 which
surface contacts with the lower surface of the photodiode array 2.
The upper end surface of this pad formation protrusion 3 is set to
be equal or substantially equal in height to the upper surface of
the photodiode array 2. Although not shown in FIGS. 1 to 3, a
groove or a protrusion used to position the photodiode array 2 may
be provided on the upper surface of the MID substrate 1. If such a
positioning groove or protrusion is provided, it is unnecessary to
employ a special positioning tool which arranges the photodiode
array 2 on the MID substrate 1 in the manufacturing of the
component of a radiation detector. In addition, such a positioning
groove or protrusion facilitates positioning the photodiode array
2, thereby making it possible to simplify manufacturing steps.
[0056] First pads 4 are provided in sections on the upper surfaces
of photodiodes of the photodiode array 2 adjacent the pad formation
protrusion 3, respectively. In addition, first pads 4 are provided
on the upper end face of the pad formation protrusion 3, and second
pads 5 are provided in sections on the upper end face of the pad
formation protrusion 3 adjacent the first pads 4, respectively. A
bonding wire 6 is provided between each first pad 4 and the
corresponding second pad 5.
[0057] The electrical connection between the first pad 4 and the
second pad 5 will be explained with reference to FIG. 3B. As
explained above, the first pad 4 and the corresponding second pad 5
are electrically connected to each other by the bonding wire 6. As
shown in FIG. 3B, the upper end face of the pad formation
protrusion 3 is equal or substantially equal in height to the upper
surface of the photodiode array 2. It is, therefore, unnecessary to
set the horizontal distance between the first pad 4 and the
corresponding second pad 5 wide when the bonding wire 6 is
provided, making it possible to narrow the width of the pad
formation protrusion 3. To narrow the horizontal distance between
the first pad 4 and the second pad S, it suffices that the first
pad 4 and the second pad 5 are equal or substantially equal in
height, If this conditions are met, therefore, it is not necessary
that the upper surface of the photodiode array 2 is equal or
substantially equal in height to the upper end face of the pad
formation protrusion 3.
[0058] As can be seen from FIG. 3A (1), a wiring pattern 7, e.g., a
cathode wiring pattern 7 is provided on the upper surface of the
MID substrate 1 which surface contacts with the photodiode array 2.
First terminals 8 in the form of, for example, pins, e.g., anode
terminals 8 as many as the second pads S and one second terminal 9
in the form of, for example, a pin, e.g., a cathode terminal 9 are
provided on the lower surface of the MID substrate 1. In addition,
the second pads 5 are electrically connected to the first terminals
8, e.g., anode terminals 8 by wirings 10 formed on the MID
substrate 1 in a one-to-one correspondence. The wiring pattern 7,
e.g. , cathode wiring pattern 7 is electrically connected to the
second terminal 9, e.g., cathode terminal 9 by, for example, a
wiring arranged in a hole formed in the MID substrate 1. As a
result, the first pads 4 of the individual photodiodes which
constitute the photodiode array 2 are electrically connected to the
second pads 5 through the bonding wires 6, respectively. Further,
since the second pads 5 are electrically connected to the first
terminals 8 through the wirings 10, respectively as shown in FIG.
2, the first pad 4 of each photodiode is electrically connected to
the first terminals. On the other hand, each photodiode has a
cathode electrode on a bottom thereof and the cathode electrode is
electrically connected to the second terminal 9 through the wiring
pattern 7, While the cathode electrodes of the individual
photodiodes are connected to the second terminal 9 in common with
the electrodes short-circuited to one another, the first pads 4 of
the individual photodiodes are connected to the first terminals 8,
respectively, without being short-circuited to one another.
Therefore, electrical signals output from the photodiodes can be
individually fetched through the corresponding first terminals 8,
respectively. This exactly applies to an instance in which the
terminals 8 are cathode terminals and the terminal 9 is an anode
terminal.
[0059] If a radiation detection apparatus is realized according to
the above configuration, an area necessary for the wirings used to
detect electrical signals generated from the individual photodiodes
which constitute the photodiode array 2 may be advantageously
small. That is, by providing a three-dimensional wiring structure
in which the electrical signals output from the second pads 5 are
fetched from the first terminals S provided on the lower surface of
the MID substrate 1, respectively, it is possible to narrow a gap
region between the photodiode arrays compared with a conventional
instance in which two-dimensional wirings are provided on the
surface of the substrate. If the two-dimensional wirings are
provided on the substrate surface as seen in the conventional art,
a radiation detection apparatus has a structure in which all the
necessary wirings are flatly arranged in the gap regions between
the photodiode arrays. It is, therefore, necessary to set the gap
regions wide so as to secure necessary wirings. The radiation
detection apparatus in the first embodiment can secure a relatively
large area occupied by the photodiodes to the conventional area,
whereby the effective X-ray receiving surface of the apparatus can
be maximized and the detection efficiency thereof can be
improved.
[0060] FIGS. 1 to 3 show that the number of the photodiodes on the
upper surface of the component of a radiation detector, therefore,
the number of the second pads 5 is eight and that of the pin-like
terminals provided on the rear surface of the component of a
radiation detector is nine by way of example. Therefore, the
interval of the second pads 5 is not consistent to that of the
pin-like terminals and that of the holes. Quite naturally, the
number of the photodiodes, that of the second pads 5 and that of
the first terminals 8 shown in FIGS. 1 to 3 are given only by way
of example. Even if the number of photodiodes is more than or less
than eight, the structure shown in FIGS. 1 to 3 can be realized, as
well.
[0061] The three-dimensional wiring of the component of a radiation
detector in the first embodiment is realized by providing the
wirings 10 on the MID substrate 1. Alternatively, the
three-dimensional wiring maybe realized by providing through holes
which penetrate the MID substrate 1 and the pad formation
protrusion 3. If the through holes are used, it is possible to
employ a substrate other than the MID substrate.
[0062] A modification of the component of a radiation detector in
the first embodiment will be explained now. In this modification, a
component of a radiation detector has a structure in which the
photodiode array 2 is not used but individual photodiodes separate
from one another are arranged on an MID substrate 1.
[0063] Namely, the component of a radiation detector in the
modification is modified from that in the first embodiment as
follows. The photodiode array 2 used in the component of a
radiation detector in the first embodiment shown in FIGS. 1 to 3 is
changed to a plurality of photodiodes and a groove or a protrusion
which positions the respective photodiodes is provided on the upper
surface of the MID substrate 1. This positioning groove or
protrusion is in the form of a bank which functions as a partition
between adjacent channels, whereby optical cross talk caused by a
transparent adhesive layer used between the photodiode and the
scintillator can be advantageously reduced.
[0064] In addition, by providing the positioning groove or
protrusion, it is advantageously unnecessary to use a special
positioning tool when the individual photodiodes are arranged on
the MID substrate 1. Further, such a positioning groove or
protrusion can facilitate positioning the photodiodes, thereby
advantageously, swiftly manufacture the component of a radiation
detector at low cost.
[0065] A radiation detector in a second embodiment will next be
described. FIG. 4 is a schematic perspective view of the radiation
detector in the second embodiment in a state in which the component
of a radiation detector in the first embodiment and a scintillator
array are separated from each other. FIG. 5 is a schematic
perspective view of the radiation detector in the second embodiment
in a state in which the component of a radiation detector in the
first embodiment and the scintillator are assembled together.
[0066] As shown in FIGS. 4 and 5, the radiation detector in the
second embodiment includes the component of a radiation detector in
the first embodiment shown in FIG. 3 and the scintillator array 11
which is provided on the upper surface of the photodiode array 2 of
the component of a radiation detector so that scintillators
correspond to the photodiodes, respectively. This scintillator
array 11 consists of scintillators 12 and separators 13. In
addition, the component of a radiation detector and the
scintillator array 11 are fixed to each other by optical
adhesive.
[0067] A modification of the radiation detector according to the
second embodiment includes the component of a radiation detector in
the modification of the first embodiment and scintillators arranged
on the upper surface of the photodiodes of the component of a
radiation detectors to correspond to the photodiodes, respectively.
As explained above, the component of a radiation detector in the
modification of the first embodiment is modified such that the
photodiode array 2 used in the component of a radiation detector in
the first embodiment shown in FIGS. 1 to 3 is changed to a
plurality of photodiodes and that a groove or protrusion which
positions the photodiodes is provided on the upper surface of the
MID substrate 1. The remaining configuration of the radiation
detector in this modification is the same as that of the radiation
detector in the second embodiment shown in FIGS. 4 and 5. According
to the radiation detector in the modification, the positioning
protrusion is in the form of a bank and functions as a partition
between adjacent channels, whereby optical cross talk caused by a
transparent adhesive layer used between the photodiode and the
scintillator can be advantageously reduced.
[0068] A radiation detection apparatus in a third embodiment will
be explained now. FIG. 6 is a schematic perspective view of the
radiation detection apparatus in the third embodiment which
apparatus is obtained by arranging a predetermined number of
radiation detectors shown in FIG. 5 in a matrix. FIG. 7 is a
schematic perspective view of the radiation detection apparatus
into which a collimator 14 is incorporated. As shown in FIGS. 6 and
7, the radiation detection apparatus has a structure in which a
radiation detection section consisting of photodiodes and
scintillators is arranged two-dimensionally. This structure enables
the radiation detection apparatus to be used not only in a
single-slice X-ray CT system but also in a multi-slice X-ray CT
system.
[0069] As explained above, in the first to third embodiments, the
difference in height between the upper surface of each photodiode
and the surface of the primary substrate is eliminated to minimize
space necessary for a wire bonding, the output terminals are
arranged below the primary substrate and the output terminals are
connected to wire bonding pads by three-dimensional wirings,
thereby making the radiation detector small in size. As shown in
FIG.6 or 7, it is possible to arrange the radiation detectors
without gaps formed therebetween and, therefore, maximize the
effective X-ray receiving area of, for example, the X-ray CT system
per unit area and improve the detection efficiency thereof.
[0070] Concrete examples of the third embodiment will be explained
below. As each photodiode 2 shown in FIG. 1, a PIN type silicon
photodiode having a length of 13.6 mm, a width of 1.35 mm and a
thickness of 0.3 mm is used. The MID substrate 1 shown in FIG. 1 is
made of liquid crystal polymer manufactured by Polyplastics Co.,
Ltd. The MID substrate 1 has an entire length of 13.6 mm, a
thickness of 1.5 mm and a width of is 1.5 mm. The protrusion has a
length of 13.6 mm, a height of 0.3 mm and a width of 0.14 mm. Each
pin-like output terminal has a diameter of 0.46 mm. The wirings in
a wire bonding pad section, a vertical wiring section and a through
hole section are all copper-plated, nickel-plated or gold-plated.
As each scintillator shown in FIG. 4, a scintillator made of
CdWO.sub.4 and having a length of 13.6 mm, a width of 1.5 mm and a
thickness of 2 mm are used.
[0071] The photodiodes and the MID substrate 1 are assembled
together to thereby manufacture the component of a radiation
detector according to the present invention. In addition, the
scintillators are incorporated into the radiator detector component
to thereby manufacture the radiation detector according to the
present invention. Further, a predetermined number of the radiation
detectors are assembled together to thereby manufacture the
two-dimensional radiation detection apparatus.
[0072] According to the present invention, arbitrary resin which
enables the MID substrate 1 to be formed three-dimensionally can be
replaced by liquid polymer manufactured by Polyplastics Co., Ltd.,
the wirings on the MID substrate 1 can be formed by printing a
conductive material on the MID substrate 1 or transferring a copper
foil thereon instead of plating. The pin-like output terminals may
be replaced by through holes or solder bumps. The material of the
scintillators is typically exemplified by CsI, NaI,
Bi.sub.4Ge.sub.3O.sub.12, Ba3F.sub.2, Gd.sub.2SiO.sub.5,
Lu.sub.2SiO.sub.5 or various type of ceramics. Basically, any
material which can convert an incident radiation ray into a light
beam is available as the material of the scintillators.
[0073] A component of a radiation detector in a fourth embodiment
will be explained now. FIG. 8A is a schematic perspective view
which shows the structure of the component of a radiation detector
in the fourth embodiment in a state in which a photodiode array 22
and a scintillator array 21 are separated from each other. FIG. 8B
is a schematic perspective view of the component of a radiation
detector in a state in which the photodiode array 22 contacts with
the scintillator array 21. As shown in FIG. 8B, in the component of
a radiation detector in the fourth embodiment, the photodiode array
22 is arranged on one side surface of the scintillator array 21 in
the array aligned direction of the scintillator array 21. The
scintillator array 21 and the photodiode array 22 are bonded to
each other by optical adhesive. The scintillator array 21 consists
of a plurality of scintillators 23 and separators 24. As shown in
FIG. 8A, a plurality of photodiodes 22a are formed on the
photodiode array 22 in sections facing the scintillators 23,
respectively, In addition, wirings 25 are electrically connected to
the respective photodiodes 22a. The wirings 25 are arranged on the
surface of the photodiode array 22 and the terminal ends thereof
are located downstream of the section in which the photodiode array
22 contacts with the scintillator array 21 in a light receiving
direction, i.e., a lower side in FIG. 8A and FIG. 8B. Terminals 26
are formed at the wirings 25, respectively.
[0074] In the fourth embodiment, the photodiode array 22 is not
located downstream of the scintillator array 21 in the light
receiving direction but arranged on one side surface of the
scintillator array 21 in the array aligned direction of the
scintillator array 21. However, each photodiode 22a included in the
photodiode array 22 does not directly converts an X-ray into an
electrical signal. Specifically, each photodiode 22a receives a
visible light beam dispersed radially from an atom constituting
each scintillator 23 due to the incidence of X-rays on the
scintillator array 21. Therefore, even if the photodiode 22a is not
located on the downstream side in the light receiving direction
with respect to X-ray, the photodiode 22a can surely receive the
visible light beam.
[0075] As can be seen, by arranging the photodiode array 22 on one
side surface of the scintillator array 21 in the array aligned
direction, the following advantages are obtained. The thickness of
the photodiode array 22 is at most about several hundred
micrometers. If the component in the fourth embodiment is viewed
from the light receiving direction, therefore, an area occupied by
the photodiode array 22 can be made far smaller than that occupied
by the scintillator array 21. As a result, if a plurality of
components are arranged to constitute a radiation detector, these
components can be arranged without generating gaps therebetween.
Therefore, if the radiation detector is used in, for example, an
X-ray CT system, the effective X-ray receiving area of the X-ray CT
system per unit area can be advantageously increased and the
detection efficiency thereof can be advantageously improved.
[0076] A radiation detector in a fifth embodiment will be explained
now. FIG. 9 is a schematic cross-sectional view which shows a state
in which the radiation detector includes a plurality of components
explained in connection to the fourth embodiment. As shown in FIG.
9, in the radiation detector in the fifth embodiment, components 27
as shown in FIG. 8A are fixed onto and thereby supported by
substrates 28, respectively. Each substrate 28 is almost equal in
length to a scintillator array 21 in the array aligned direction of
the scintillator array 21 and almost equal in width to the
scintillator array 21 in a direction at right angle to the array
aligned direction. The height of the substrate 28 is not limited to
a specific value. Wirings 29 are provided on the substrates 28 to
correspond to respective photodiodes.
[0077] An assembly method of the radiation detector shown in FIG. 9
will be explained. If the radiation detector is assembled into the
structure shown in FIG. 9, in order to facilitate the operation of
bonding wire, the wirings 29 provided on the substrates 28 are
electrically connected to the terminals 26 of wirings arranged on
the surfaces of the photodiode arrays 22 of the adjacent components
27 by bonding wires 30, respectively. Recesses are formed in the
substrates 28 in sections corresponding to the positions of the
bonding wires 30, respectively.
[0078] To assemble the components into the state shown in FIG. 9,
the components are sequentially assembled together not in a
horizontal direction but in a vertical direction while placing the
left side of FIG. 9 down. That is, a component (to be denoted by
reference symbols 27A for the convenience of explanation) is
fixedly overlapped with a substrate (to be denoted by reference
symbols 28A for the convenience of explanation). The terminal 26 of
the component 27A thus overlapped with the substrate 28A is
electrically connected to the wiring 29 provided on the substrate
28A by the bonding wire 30. A substrate 28B is fixedly overlapped
with a substrate 28A. Thereafter, a component 27B is fixedly
overlapped with a component 27A substrate 28C and the terminal 26
of the component 27B is electrically connected to the wiring 29 of
the substrate 28B by bonding wires 30. This operation is repeated
to thereby form a two-dimensional radiation detection apparatus
which employs a predetermined number of components.
[0079] If necessary, two or more two-dimensional radiation
detection apparatuses thus assembled can be arranged in the array
aligned direction of the scintillator arrays 21 to thereby form a
two-dimensional radiation detection apparatus which has a wider
effective area.
[0080] The substrates 28 can be glass epoxy substrates, ceramic
substrates, liquid crystal polymer substrates, substrates
consisting of epoxy resin molded matters, the other plastic
substrates or the like.
[0081] The radiation detector shown in FIG. 9 consists of a
plurality of components 27 and a corresponding number of substrates
28. As shown in FIG. 10, substrates 31 continuously provided by the
length of a predetermined number of radiation detectors in a
direction at right angle to the array aligned direction of the
scintillator arrays 22. In this instance, grooves which contain the
sections of the photodiode arrays 22 extending below the contact
sections between the photodiode arrays 22 and the scintillator
arrays 21 of the respective components 27, are provided in the
upper surface of the substrates 31. In addition, conductive pins 32
are embedded into the substrates 31 so that the conductive pins 32
can be electrically connected to the terminals 26 of the wirings
arranged on the surfaces of the photodiode arrays 22,
respectively.
[0082] FIG. 11 is a schematic perspective view of a two-dimensional
radiation detection apparatus obtained by arranging and coupling a
predetermined number of radiation detectors shown in FIG. 9 or 10
from which the sections of the substrates 28 are excluded.
[0083] As explained above, in the component 27 and the radiation
detector, each wiring 25 which is electrically connected to each
photodiode of the photodiode array 22 is pulled out on the
downstream side of the radiation detector in the light receiving
direction, i.e., on the lower side of the radiation detector.
Therefore, as shown in FIG. 11, it is possible to arrange the
radiation detectors without gaps formed therebetween. This
arrangement, therefore, enables the effective X-ray receiving area
of, for example, an X-ray CT system per unit area to be maximized
and the detection efficiency thereof to be improved.
[0084] FIGS. 12 and 13 are schematic perspective views which
explain a component of a radiation detector and a radiation
detector in a sixth embodiment according to the present invention.
FIG. 12 is a schematic perspective view which shows a state in
which a photodiode array 33 and a scintillator array 34 are
separated from each other. FIG. 13 is a perspective view which
shows a state in which the photodiode array 33 and the scintillator
array 34 are assembled together.
[0085] As is obvious from FIGS. 12 and 13, in an instance of the
component and the radiation detector in the sixth embodiment, the
photodiode array 33 is arranged on one side surface of the
scintillator array 34 in the array aligned direction of the
scintillator array 34 and fixed to the scintillator array 34 by
optical adhesive. Wirings 35 are electrically connected to the
photodiodes of this photodiode array 33, respectively. The wirings
35 are extended downstream of the contact sections between the
photodiode array 33 and the scintillator array 34 in the light
receiving direction and consequently extended in the array aligned
direction of the scintillator array 34. The terminal ends of the
respective wirings 35 are present at lateral positions exceeding
the contact sections between the photodiode array 33 and the
scintillator array 34 to thereby form terminals 36, respectively. A
part of a substrate 37 is fixedly attached to the rear surface of
the photodiode array 33 and wirings 38 are provided on the other
section of the substrate 37. The wirings 38 are electrically
connected to the terminals 36 by bonding wires, respectively.
[0086] The component according to the sixth embodiment has
following advantages are obtained with respect to the wirings 35
and the terminals 36 pulled out from the respective photodiodes
included in the photodiode array 33. Since the photodiode array 33
is arranged on the side surface of the scintillator array 34, only
the thickness of the photodiode array 33 influences an effective
X-ray receiving area. It is, therefore, possible to make the area
of the surface of the photodiode array 33 on which the photodiodes
are arranged, large. This makes it possible to greatly extend the
photodiode array 33 toward the downstream side in the light
receiving direction. On the photodiode array 33, the wirings 35 can
be arranged in the region other than the region in which the
respective photodiodes are arranged. As a result, by setting the
area of the photodiode array 33 large, the region in which the
wirings 35 and the terminals 36 are arranged can be set large.
Accordingly, it is not necessary to provide microscopic wirings as
seen in the conventional art and it is thereby possible to prevent
disadvantages such as the breaking of the wirings and the increase
of resistance.
[0087] If a radiation detector is manufactured using the components
in the sixth embodiment, each substrate 37 can be provided on the
section of the photodiode array 33 which does not contact with the
scintillator array 34 as shown in FIGS. 12 and 13. As the other
manufacturing method, a substrate which supports the component may
be provided below the component. In this instance, it is not
necessary to electrically connect the terminals 26 on the
photodiode array 33 to the wirings 29 of the substrate or the
conductive pins 32 as shown in FIGS. 9 and 10.
[0088] If a two-dimensional radiation detection apparatus is
manufactured using these radiation detectors, an arbitrary number
of radiation detectors can be coupled to one another in a direction
at right angle to the array aligned direction of the scintillator
arrays .34 as shown in the schematic perspective view of FIG. 14.
In addition, by pulling out the terminals 36 to the both sides of
the apparatus, it is possible to arrange two radiation detection
apparatuses in the array aligned direction of the scintillator
arrays 34, thereby making it possible to further increase the
effective X-ray area of the apparatus.
[0089] Concrete example of the sixth embodiment will be explained
below. FIG. 15A is a schematic cross-sectional view of a
two-dimensional radiation detection apparatus in a state in which
the apparatus is cut out in the array aligned direction of the
scintillator arrays of radiation detectors. FIG. 15B is a schematic
cross-sectional view of the two-dimensional radiation detection
apparatus in a state in which the apparatus is cut out in a
direction perpendicular to FIG. 15A. As shown in FIGS. 15A and 158,
as each photodiode array 39, a 24-channel photodiode array (a
length of 38.05 mm, a width of 6.0 mm, a thickness of 0.3 mm, a
light receiving section size of 1.18 mm.times.3.8 mm, a channel
pitch of 1.5875 mm) consisting of PIN type silicon photodiodes are
used. As each scintillator array 40, an array made of CdWO.sub.4
having a length of 38.05 mm, a width of 5.0 mm and a thickness of
2.19 mm (a channel size of 1.33 mm.times.4.0 mm.times.2.0 mm) is
used. As each substrate 41, a glass epoxy substrate having a
thickness of 0.2 mm is used. The wirings of each photodiode array
are connected to those of the substrate 41 by bonding wires 42,
respectively. As output terminals from the substrate wirings, a
25-channel connector 43 having a pitch of 1.27 mm is used. Among 25
channels, 24 channels are anode pins 44 and one channel is a
cathode pin 45. Five 24-channel detector substrates are stacked,
epoxy resin 46 is filled into the space sections thereof and
protection cover plates 47 are provided on the sides on which no
substrates are provided, respectively, thereby manufacturing a
prototype 120-channel two-dimensional X-ray detector.
[0090] According to the seventh embodiment, BGA bumps or through
hole terminals may be employed in place of the pins. In addition,
the material of the scintillators may be CsI, NaI or LSO instead of
CdWO.sub.4 or scintillators of various ceramics may be used, as
well.
[0091] A component of a radiation detector in a seventh embodiment
will be explained now. FIG. 16 is a schematic perspective view of a
radiation detection apparatus in the seven the embodiment, As shown
in FIG. 16, the component of a radiation detector in the seventh
embodiment includes a substrate 51 which has a groove section 52
extended in a slice direction and a photodiode array 53 which is
embedded into the groove section 52. A two-dimensional scintillator
array 54 is arranged on the substrate 51 and the photodiode array
53 embedded into the groove section 52 of the substrate 51. In FIG.
16, the two-dimensional scintillator array 54 is arranged to be
spatially separated from the substrate 51. This is intended to
facilitate understanding the structure of the radiation detection
apparatus in the seventh embodiment. Actually, however, the
two-dimensional scintillator array 54 is fixedly attached to the
substrate 51 by transparent adhesive. In addition, a circuit board
64 is arranged under the substrate 51. An electrical circuit
mounted on the circuit board 64 is electrically conductive to
individual photodiodes 55 which constitute the photodiode arrays
53.
[0092] The photodiode array 53 has a plurality of photodiodes 55
which are arranged in a one-dimensional array on the photodiode
array 53. In the seventh embodiment, the photodiode array 53 is
arranged so that the large length direction of the array 53 is the
slice direction. The radiation detection apparatus has, therefore,
a structure in which four photodiodes 55 are arranged in a channel
direction (at right angle to the slice direction) and three
photodiodes 55 are arranged in the slice direction.
[0093] The two-dimensional scintillator array 54 has a plurality of
scintillators 59 and separators 60. A plurality of scintillators 59
are arranged two-dimensionally to correspond to the photodiodes 55,
respectively. The separators 60 are put between the scintillators
59, respectively.
[0094] Each of the scintillators 59 converts an incident X-ray into
a visible light beam. The scintillator 59 is made of CdWO.sub.4,
CsI, NaI or the like and functions to output a visible light beam
in accordance with the intensity of the incident X-ray to the
corresponding photodiode 55. In addition, a white paint is applied
to the outer surface of each scintillator 59 so as to prevent the
visible light beam converted from the X-ray within the scintillator
59 from leaking to the outside of the scintillator 59. The material
of the scintillator 59 may be other than that mentioned above.
Typically, Bi.sub.4Ge.sub.3O.sub.12, BaF.sub.2, Gd.sub.2SiO.sub.5,
Lu.sub.2SiO.sub.5 or various ceramics are available. Basically, any
material which can convert an incident radiation ray into a light
beam is available.
[0095] The separators 60 prevent the transmission of X-rays and
visible light beams. Each separator 60 contains lead (Pb) and the
like and functions to reflect or absorb an X-ray and a visible
light beam. By putting the separators 60 between the scintillators
59, respectively, it is possible to prevent cross talk from being
occurring if X-rays are diagonally incident on the surfaces of the
scintillators 59 and the same X-ray is incident on a plurality of
scintillators 59. This is true for visible light beams converted f
ram X-rays. Namely, by arranging the separators 60, it is possible
to prevent optical cross talk from being occurring if a visible
light beam generated in a certain scintillator 59 is incident on
the other scintillator(s) adjacent the certain scintillator 59.
[0096] Each photodiode 55 receives the visible light beam converted
from the X-ray within the corresponding scintillator 59, converts
the received visible light beam into an electrical signal and
outputs the electrical signal to the outside. The photodiode 55
consists of a PIN type photodiode which has an n-type layer on a
bottom section and which has a p-type layer formed on the surface
section of the photodiode array 53. Further, the photodiode 55 has
an anode electrode 56 connected to the p-type layer on an upper
peripheral edge section and a cathode electrode in contact with the
n-type layer on a bottom section.
[0097] The manner in which the photodiodes 55 and the circuit board
64 are electrically connected will be explained with reference to
FIG. 17. FIG. 17 shows a part of the cross-sectional structure of
the radiation detection apparatus in the seventh embodiment. In
FIG. 17, the two-dimensional scintillator array 54 and the circuit
board 64 are not shown to facilitate understanding.
[0098] As shown in FIGS. 16 and 17, the photodiodes 55 are embedded
into the groove section 52 provided in the substrate 51. As is
obvious from FIG. 17, the groove section 52 has an equal depth to
the thickness of each photodiode 55. For that reason, the anode
electrode 56 arranged on the upper surface of each photodiode 55
and each pad 57 arranged on the upper surface of the substrate 51
form the same plane in a state in which the photodiodes 55 are
embedded into the groove section 52. In addition, the anode
electrode 56 arranged on the upper surface of each photodiode 55 is
connected to each pad 57 arranged on the upper surface of the
substrate 51 by a bonding wire 61. Further, in each broken-line
region in FIG. 17, a through hole 58 is provided and the through
hole 58 is electrically connected to the pad 57.
[0099] Furthermore, the through hole 58 penetrates through the rear
surface of the substrate 51 and is electrically connected to each
pad 63 arranged on the rear surface of the substrate 51. Therefore,
an electrical signal output from the anode electrode 56 is
transmitted to the pad 63 arranged on the rear surface of the
substrate 51 through bonding wire 61, the pad 57 and the through
hole 58. As shown in FIG. 16, the circuit board 64 is arranged on
the rear surface of the substrate 51. Each pad 63 is electrically
connected to the electrical circuit provided on the circuit board
64. A solder ball 62 is arranged under the pad 63, so that the pad
63 is electrically connected to the electrical circuit provided on
the circuit board 64 by the solder ball 62. Specifically, heat is
applied while the substrate 51 is tentatively fixed onto the
circuit board 64 to melt the solder ball 62, thereby ensuring the
pad 63 conductive to the electrical circuit. By providing the
structure explained above, the radiation detection apparatus in the
seventh embodiment can output an electrical signal from each
photodiode 55 to the outside of the apparatus from the
corresponding pad 63 on the circuit board 64.
[0100] The manner of holding the cathode electrode provided on the
rear surface of each photodiode 55 conductive to the circuit board
64 will be explained now. FIG. 18 is a top view which shows the end
section of the substrate 51 which constitutes the radiation
detection apparatus 51 in the seventh embodiment. It is noted that
FIG. 18 shows a state before the photodiode array 53 is embedded
into the groove section 52.
[0101] Cathode pads 65 are arranged on the bottom of the grove
section 52 provided in the substrate 51. The cathode pads 65 are
arranged on the entire bottom of the groove section 52 so as to
electrically connect the cathode electrodes provided on the bottoms
of the photodiodes 55 arranged on the photodiode array 531
respectively. Therefore, the individual photodiodes 55 are
short-circuited in respect of the cathode electrodes. However,
since the anode electrodes are separated for the respective
photodiodes 55, electrical signals are not synthesized at the time
of outputting the electrical signals.
[0102] In addition, a cathode through hole 66 is arranged on a
partial region of each cathode pad 65. The cathode through hole 66
is provided to electrically connect the bottom of the groove
section 52 to the rear surface of the substrate 51. As in the
instance of the connection between the anode electrode-and the
electrical circuit on the circuit substrate 64 shown in FIG. 17,
the cathode through hole 66 is electrically connected to each pad
63 provided on the rear surface of the substrate 51. Further, each
pad 63 provided on the rear surface of the substrate 51 is
connected to the electrical circuit on the circuit board 64 through
the solder ball 62. As a result, the radiation detection apparatus
in the seventh embodiment has a structure in which an electrical
signal output from each photodiode 55 is output to the outside of
the apparatus.
[0103] The operation of the radiation detection apparatus in the
seventh embodiment will be explained now. FIG. 19 is a typical view
which shows a manner in which X-rays are incident on the radiation
detection apparatus in the seventh embodiment.
[0104] An X-ray incident on the upper surface of each scintillator
59 is converted in to a visible light beam within the scintillator
59. Efficiency of converting the X-ray into the visible light beam
is proportional to the energy of the X-ray. The X-rays incident on
the upper surfaces of the scintillators 59 at angles other than the
right angle are all converted into visible light beams before
reaching the side surfaces of the scintillators 59 or, even if
reaching the side surfaces thereof as the X-rays, most of the
X-rays are absorbed or reflected by the separators 60. The X-rays
are hardly incident on the adjacent other scintillators 59. The
same thing is true for the visible light beams converted from the
X-rays, i.e., the visible light beams are not incident on the other
scintillators 59.
[0105] The visible light beam converted from the X-ray is incident
on the photodiode 55. The photodiode 55 converts the received
visible light beam into an electrical signal. Specifically, an
electrical signal is generated based on the generation of a pair of
an electron and a hole in the photodiode 5$ by the incident light.
The intensity of the electrical signal is proportional to energy
held by the visible light beam received by the photodiode 55. As
already explained above, since the energy of the visible light beam
is proportional to the intensity of the X-ray incident on each
scintillator 59, the intensity of the electrical signal output from
the photodiode 55 is obviously proportional to the intensity of the
X-ray incident on the corresponding scintillator 59 The electrical
signal output from each photodiode 55 is transmitted to the rear
surface of the substrate 51 through the through hole 58 and the
cathode through hole 66 and output to the outside through the
circuit board 64. While FIG. 19 shows a manner in which currents I
are output as an example of the electrical signals, the electrical
signals are not limited thereto but may be output in the form of
voltage changes.
[0106] As explained so far, by providing the structure in which the
electrical signal in accordance with the intensity of the X-ray
incident on each scintillator 59 is output, the radiation detection
apparatus in the seventh embodiment can obtain an X-ray intensity
distribution in relation to incident positions.
[0107] The radiation detection apparatus in the seventh embodiment
has a structure in which a plurality of photodiode arrays 53 on
which the photodiodes 55 are arranged in columns, are arranged. The
radiation detection apparatus in the seventh embodiment has an
advantage of improving product yield. In other words, if a
plurality of two-dimensional photodiode arrays shown in FIG. 16 are
formed on the same substrate and only one defective photodiode
exists among the twelve photodiodes, then the remaining eleven
photodiodes cannot be used for the radiation detection
apparatus.
[0108] On the otherhand, according to the radiation detection
apparatus in the seventh embodiment, even if one photodiode 55 is
defective, it suffices to replace the photodiode array 53 including
the defective photodiode 55 by another one and the remaining nine
photodiodes can be, therefore, effectively utilized. As for the
radiation detection apparatuses employed in recent X-ray CT scan
systems, in particular, the number of channels increases and the
number of slices increases. The number of photodiodes arranged
tends to increase, accordingly. Therefore, it can be expected that
the radiation detection apparatus in the seventh embodiment in
which a plurality of one-dimensional photodiode arrays 53 are
arranged exhibits further improved yield.
[0109] In addition, the radiation detection apparatus in the
seventh embodiment adopts a structure in which the photodiode
arrays 53 each having one-dimensional photodiodes arranged
one-dimensionally are embedded into the groove section 52. By doing
so, the following advantages can be obtained. Since the width of
the groove section 52 is equal to the width of each photodiode
array 53, it is easy to position the photodiode arrays 53 relative
to the groove section 52. As a result, to arrange the photodiode
arrays 53 on the substrate 51, it suffices to position the
photodiode arrays 53 only in respect of the slice direction.
Besides, it a protrusion or a groove section is additionally
provided for the positioning in the slice direction, the photodiode
arrays 53 can be easily arranged without the need to execute a step
such as a position adjustment step. Consequently, the radiation
detection apparatus in the seventh embodiment can be manufacture
easily and swiftly.
[0110] Moreover, according to the seventh embodiment, the thickness
of each photodiode array 53 is almost equal to the depth of the
groove section 52. As a result, the radiation detection apparatus
in this embodiment has an advantage in that a region necessary for
the bonding wires 61 can be made small.
[0111] To output the electrical signals from the respective
photodiodes 55 arranged on each photodiode array 53 to the outside
of the apparatus, it is necessary to electrically connect the anode
electrode 56 and the cathode electrode of each photodiode 55 to
each electrode provided on the substrate, If the photodiode arrays
are arranged on a flat plate, there is no avoiding generating a
difference in height between each anode electrode and each pad
arranged on the substrate. If such a difference in height exists,
it is necessary to set the horizontal distance necessary for a wire
bonding to be large. In the seventh embodiment, by contrast, no
difference in height is generated between each anode electrode 56
and the corresponding pad 57 at all or even if the difference in
height is generated, it is quite a slight difference, so that it is
not necessary to secure a large horizontal distance as seen in the
conventional art.
[0112] Moreover, in the seventh embodiment, the radiation detection
apparatus has a structure in which the anode electrodes 56 are
pulled out arranged on the upper surface of the photodiodes 55 by
using the through hole 58. Therefore, the width of the bank section
of the substrate 51 located between the adjacent photodiode arrays
53 can be narrowed. Conventionally, since necessary wirings are
provided on the upper surface of the substrate, it is necessary to
narrow the width of wirings or widen a distance between the
photodiode arrays 53.
[0113] Moreover, in the seventh embodiment, the structure of
pulling out the anode electrodes 56 three-dimensionally is adopted
and there is no need to provide wirings on the upper surfaces of
the substrates 51. Therefore, even if the radiation detection
apparatus has a structure in which the number of photodiodes 55
increases as the number of channels and that of slices increase, it
is unnecessary to secure a wide distance between the photodiode
array 53., making it possible to maintain a fixed distance
therebetween. Specifically, the width of the bank section of the
substrate 51 located between the photodiode arrays 53 can be
arbitrarily narrowed as long as the width necessary for the bonding
wire and the through hole can be secured. It is, therefore,
possible to set an area occupied by the photodiodes 55 wide on the
surface of the radiation detection apparatus perpendicular to the
incident direction of the X-rays and to thereby realize a radiation
detection apparatus having high sensitivity.
[0114] Furthermore, in the seventh embodiment, the radiation
detection apparatus has a structure in which electrical signals are
output to the outside of the apparatus by the electrical circuit on
the circuit substrate 64 it the anode electrode 56 is pulled out
from each substrate 51 in the perpendicular direction thereof and
connected to the circuit substrate 64. In this instance, it is
possible to constitute a circuit even in are region of the circuit
substrate 64 located below the photodiode arrays 53, an area used
for the circuit can be advantageously made large compared with an
instance in which an electrical circuit is arranged on each
substrate 51. As a result, it is unnecessary to provide microscopic
wirings and it is thereby possible to avoid the risk of increasing
resistance and breaking wirings.
[0115] Additionally, in the seventh embodiment, the groove section
52 can be easily provided on the substrates 51. For example, if the
surface of each substrate 51 is scraped using a dicing saw which is
employed to isolate semiconductor chips, the groove section 52 can
be formed. The seventh embodiment has, therefore, an advantage in
that the radiation detection apparatus can be easily manufactured.
Besides, since the photodiode arrays 53 can be positioned with a
simple structure, the radiation detection apparatus can be easily
manufactured in this respect, as well.
[0116] In addition, in the seventh embodiment, the pad 63 provided
on the rear surface of each substrate 51 is electrically connected
to the circuit board 64 through the solder ball 62. It is,
therefore, possible to easily fix the substrate 51 to the circuit
board 64 and to thereby easily manufacture the radiation detection
apparatus.
[0117] While the structure in which there are three slices and four
channels are provided per slice is adopted in the seventh
embodiment, a structure in which a plurality of photodiodes are
employed per channel of a predetermined slice in the slice
direction may be adopted.
[0118] While the large length direction of the photodiode arrays 53
is the slice direction and the small length direction thereof is
the channel direction in the seventh embodiment, these directions
may be reversed. That is, it is possible to constitute the
radiation detection apparatus in the seventh embodiment even if the
photodiode arrays 53 are arranged so that the large length
direction thereof is parallel to the channel direction.
[0119] Furthermore, while the bonding wire 61 connecting each anode
electrode 56 to each pad 57 is arched in FIGS. 16 and 17, the
linear bonding wire 61 maybe employed. As explained above, there is
no difference in height between the upper surface of the substrate
51 and that of the photodiode 55. For that reason, even if the
anode electrode 56 is connected to the pad 57 by the linear bonding
wire, there is no fear of the breaking of the bonding wire or the
like.
[0120] Moreover, the horizontal sectional shape of each through
hole 58 and each cathode through hole 66 is not necessarily
circular. If the horizontal section shape thereof is a shape of an
ellipse which has a long axis in the large length direction of the
photodiode arrays 53, the length of the outer periphery of the
ellipse can be set large. Compared with a circular shape, it is
possible to effectively suppress electrical resistance generated
when an electrical signal passes through each through hole.
[0121] In the seventh embodiment, the structure in which the PIN
type photodiodes are arranged so that the p-type layer of each
photodiode is put on the upper surface of the photodiode and the
anode electrode 56 is exposed to the upper surface of the
photodiode, is adopted. Alternatively, a structure in which the
n-type layer is arranged on the upper surface of the photodiode and
the cathode electrode is exposed to the upper surface thereof may
be adopted. Even with the latter structure, the radiation detection
apparatus can obtain the same advantage.
[0122] While the PIN type photodiodes are used as the photodiodes
55 included in each photodiode array 53 in the seventh embodiment,
the photodiodes are not limited thereto but PN junction
photodiodes, Schottky photodiodes, heterojunction photodiodes or
avalanche photodiodes may be employed instead of the PIN
photodiodes. Alternatively, circuits other than the photodiodes may
be used as long as they can perform photoelectric conversion. For
example, photoresistors each having an electrical resistance
changing according to the intensity of light applied thereto may be
employed in place of the photodiodes.
[0123] Furthermore, while the circuit board 64 is arranged under
the substrate 51 in the seventh embodiment, the circuit substrate
64 can be omitted. For example, a circuit pattern may be formed on
the rear surface of each substrate 51 in advance and a pad used to
output an electrical signal to the outside of the apparatus may be
arranged on the side surface of the substrate 51. In this instance,
it is possible to dispense with the circuit substrate 64 and the
solder balls 62.
[0124] A radiation detection apparatus in an eighth embodiment will
be explained now. FIG. 20 is a schematic cross-sectional view which
shows the structure of the radiation detection apparatus in the
eighth embodiment. In FIG. 20, two-dimensional scintillator arrays
arranged on substrates 79 and a circuit board arranged under the
substrate 79 are not shown to facilitate understanding.
[0125] In the radiation detection apparatus in the eighth
embodiment, a groove section 80 which is provided on the upper
surface of the substrate 79 is formed to be deeper than that in the
seventh embodiment. The remaining respects are the same in
structure as those in the seventh embodiment and exhibit the same
advantages as those of the seventh embodiment unless otherwise
specified.
[0126] In the eighth embodiment, the depth of the groove section 80
is get larger than the thickness of a photodiode array 69 embedded
into the groove section 80. As a result, the following advantages
are obtained.
[0127] Since photodiode arrays 69 which are manufactured on the
same conditions are embedded into the groove section 80, it is
normally assumed that the difference in thickness does not occur
among the photodiode arrays 69. Actually, however, the photodiode
arrays 69 sometimes differ in s thickness. If photodiodes are
formed by epitaxial growth on a semiconductor substrate, in
particular, it is difficult to perfectly perform epitaxial growth,
with the result that the difference in thickness often occurs.
[0128] If the photodiodes 69 differ in thickness, an upper surface
formed by the substrates 79 and the photodiode arrays 69 embedded
into the groove section 80 cannot be made smoothly flat. If
two-dimensional scintillator arrays are arranged on such an upper
surface, there is a probability of deteriorating the stability of
the two-dimensional scintillator arrays. To prevent this, it is
possible to provide a structure in which gaps generated between the
substrates 79 and the two-dimensional scintillator arrays are
filled with transparent adhesive layers, respectively. In that
instance, however, optical cross talk caused by the leakage of
light from the gap sections filled with the transparent adhesive
layers disadvantageously occurs.
[0129] In the eighth embodiment, therefore, the depth of the groove
section 80 is set larger than the thickness of each photodiode
array 69. In addition, the upper surface of the substrate 79 is
fixedly attached to the two-dimensional scintillator array through
transparent adhesive. It is noted that the upper surface of each
photodiode array 69 does not contact with the two-dimensional
scintillator array. Since the upper surfaces of the substrates 79
form the same flat surface except for the groove section 80, it is
possible to advantageously solve the problem that the flat surface
cannot be formed, In addition, since no gaps are generated between
the upper surfaces of the substrates 79 and the two-dimensional
scintillator arrays, it is also possible to avoid the problem of
optical cross talk.
[0130] It is preferable that the distance between the depth of the
groove section 80 and the thickness of each photodiode array 69 is
not less than 1 .mu.m and not more than 100 .mu.m. The reason of
setting the difference to be not less than 1 .mu.m is as follows.
If the difference is too small, the difference in thickness among
the individual photodiode arrays 69 cannot be absorbed. The reason
of setting the difference to be not more than 100 .mu.m is as
follows If the difference is larger than 100 .mu.m, the difference
in height between the anode electrode 56 of each photodiodes
included in the photodiode array 69 and each pad 68 arranged on the
upper surface of the substrate 79 cannot be ignored, with the
result that it is necessary to set the distance between the
photodiode arrays 69 wide for wire bonding by the boding wires
67.
[0131] A ninth embodiment will be explained now. FIG. 21 is a
schematic perspective view which shows a substrate 70 and
photodiode arrays 73 embedded into the substrate 70 which
constitute a radiation detection apparatus in the ninth embodiment.
In the radiation detection apparatus in the ninth embodiment, the
second groove section 72 is provided on the upper section of the
first groove section 71 which is provided to embed the photodiode
arrays 73 into the substrate 70. As shown in FIG. 21, the second
groove section 72 has a structure in which an opening section wide
in a channel direction is formed in the upper section thereof and a
width thereof is narrower in a light receiving downstream
direction. Since the first groove section 71 is formed to embed the
photodiode arrays 73 into the substrate 70, the cross section of
the first groove section 71 is rectangular. It is noted that the
respects which will not be explained in this embodiment are the
same as those of the radiation detection apparatus in the seventh
embodiment and equal in function. For example, in the ninth
embodiment, a circuit board is arranged under the substrate 70, and
the circuit board is electrically connected to each pad 63 provided
on the rear surface of the substrate through as older ball 62 so
that an electrical signal is output to the outside of the
apparatus.
[0132] FIG. 22 is a schematic cross-sectional view which shows the
structure of the radiation detection apparatus in the ninth
embodiment. The photodiode arrays 73 are embedded into the first
groove section 71 formed in the substrate 70, An anode electrode 74
of each of photodiodes arranged on each photodiode array 73, is
electrically connected to a pad 75 provided on an inclined surface
constituting the second groove section 72 through a bonding wire.
In addition, a through hole 76 which penetrates from the second
groove section 72 to the substrate 70 in a vertical direction is
arranged for each photodiode and electrically connected to the pad
75. Further, pads 63 are provided on the rear surfaces of the
substrates 70 and electrically connected to the through holes 76,
respectively. An electrical signal which is output from each
photodiode arranged on each photodiode array 73 is, therefore,
output to the rear surface of the substrate 70 through the pad 75,
the through hole 76 and the pad 63.
[0133] The second groove section 72 functions as a waveguide path
which collects visible light beams converted from X-rays in
respective scintillators 59 to the photodiode arrays 73. That is,
by providing the second groove section 72, the visible light beam
converted from the X-ray in each scintillator 59 is appropriately
reflected on the inclined surface which constitutes the second
groove section 72, reaches the corresponding photodiode included in
the photodiode array 73 and is received by the photodiode. To
improve the visible light beam reflectance of the second groove
section 72 or to efficiently irradiate visible light beams into the
photodiodes, a multilayer structure which consists of a plurality
of films having different refraction indexes may be provided in the
second groove section 72.
[0134] An advantage of providing the second groove section 72 will
be explained. The radiation detection apparatus in the ninth
embodiment has a structure of collecting visible light beams by the
second groove section 72. Compared with an X-ray receiving area on
the upper surface of each scintillator 59, the area of the light
receiving section of each photodiode can be made small As a result,
it is possible to make the photodiodes which constitute the
radiation detection apparatus small in size and to thereby reduce
manufacturing cost. This is because each photodiode is made small
in size and the number of photodiodes which can be manufactured
from a single wafer can thereby increase.
[0135] A modification of the radiation detection apparatus in the
ninth embodiment will be explained now. FIG. 23 is a schematic top
view which shows a substrate 77 and photodiodes 78 arranged on the
substrate 77 which constitute the radiation detection apparatus in
the modification. This modification is the same as the ninth
embodiment in that two-dimensional scintillator array is arranged
on the substrate 77 and a circuit board is arranged under the
substrate 77. In the modification, not the photodiode array but
individually separated photodiodes 78 are arranged on the substrate
77. The photodiodes 78 are embedded into the first groove section
which is provided in the substrate 77 as in the instance of the
ninth embodiment. In addition, the second groove section which
functions as a waveguide path is formed on the upper section of the
first grove section into which the photodiodes 78 are embedded.
[0136] In the modification the second groove section has inclined
surfaces not only in a slice direction but also in a channel
direction and functions as a waveguide path which converges
incident visible light beams on the photodiodes 78. It is,
therefore, possible to further efficiently collect the visible
light beams in the photodiodes 78 and to thereby make each
photodiode 78 further smaller in size.
[0137] The present invention has been explained so far while
referring to the first to ninth embodiments thereof. The present
invention is not limited to these embodiments and those skilled in
the art could contrive various modifications from these
embodiments. For example, in the first to third embodiments and the
seventh to ninth embodiments, a photo-detector can be obtained by
excluding the scintillators or the scintillator arrays. According
to the present invention, it is possible to increase an area
occupied by the photodiodes. Therefore, by applying the structure
of the present invention to the photo-detector, it is possible to
provide a photo-detector having a large light receiving area and
high sensitivity.
[0138] In the first to ninth embodiments, the pad provided on the
upper surface of each photodiode is electrically connected to the
substrate by the bonding wire. However, the electrical connection
between the pad and the substrate is not limited to the wire
bonding. For example, the electrical connection may be established
by means of a flip-chip method or a TAB (Tape Automated Bonding)
method. In the first to ninth embodiments, the pad provided on the
upper surface of each photodiode and the substrate form the same
plane, so that they can be easily electrically connected by these
methods,
[0139] Further, in the seventh to ninth embodiments, each
photodiode converts a visible light beam into an electrical signal.
Alternatively, a light beam having a wavelength other than that of
the visible light may be applied to the photodiode. Specifically,
by employing Schottky photodiodes, it is possible to convert light
beams in a shorter wavelength band than a visible light range into
electrical signals. If photodiodes are formed out of InSb, for
example, it is possible to obtain a photoelectric element having
sensitivity up to an infrared range by decreasing the temperature
of the photodiodes to nitrogen temperature. If such photodiodes are
combined with scintillators each of which converts an X-ray into a
light beam having the wavelength band explained above, it is
possible to constitute the component of a radiation detector, the
radiation detector and the radiation detection apparatus.
[0140] Moreover, in the seventh to ninth embodiments, one
photodiode array is embedded into one groove section.
Alternatively, a plurality of photodiode arrays aligned in a slice
direction may be embedded into one groove section. Alternatively,
not one photodiode array but individual photodiodes may be embedded
into one groove section. In that instance, it is preferable that a
protrusion or a groove which positions the individual photodiodes
is provided in the groove section.
[0141] According to the component of a radiation detector and the
radiation detector of the present invention, the MID substrate is
employed, the difference in height between the upper surface of
each photodiode and the surface of the primary substrate is
eliminated to thereby minimize space necessary for a wire bonding,
the output terminals are arranged below the primary substrate and
the output terminals are connected to the wiring bonding pads by
three-dimensional wirings, respectively to thereby make the
radiation detector small in size. It is, therefore, possible to
arrange the radiation detectors without gaps formed therebetween.
Consequently, it is possible to maximize the effective X-ray
receiving area of, for example, the X-ray CT system per unit area
and to improve the detection efficiency thereof In addition,
according to the component of a radiation detector and the
radiation detector of the present invention, each wiring
electrically connected to each photodiode of the photodiode array
is pulled out from the downstream side of the radiation detector in
the light receiving direction i.e., from the lower side thereof. It
is, therefore, easy to make a unit radiation detector small in size
and to manufacture the unit radiation detector. Consequently, it is
possible to arrange the radiation detectors without gaps formed
therebetween, to maximize the effective X-ray receiving area of,
for example, the X-ray CT system per unit area and to improve the
detection efficiency thereof.
[0142] Moreover, according to the radiation detection apparatus of
the present invention, the groove section is formed in the upper
surface of the substrate and the photodiode array is embedded into
the groove section, thereby making it possible to easily position
the photodiode array. Further, the first pads arranged on the
photodiode array and the second pads arranged on the substrate are
arranged to constitute the same plane. It is, therefore, possible
to minimize space necessary for a wire bonding, to maximize the
effective X-ray receiving area of, for example, the X-ray CT system
per unit area and to improve the detection efficiency thereof.
Besides, since each second pad is electrically connected to each
third pad provided on the rear surface of the substrate by the
three-dimensional wiring such as a through hole and an electrical
signal is output from the third pad. It is, therefore, possible to
maximize the effective X-ray receiving area and to secure a wide
region for wirings.
[0143] Although the invention has been described with respect to a
specific embodiment for a complete and clear disclosure, the
appended claims are not to be thus limited but are to be construed
as embodying all modifications and alternative constructions that
may occur to one skilled in the art which fairly fall within the
basic teaching herein set forth.
* * * * *