Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2001-01-18
2003-03-25
Le, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S658000, C324S688000
Reexamination Certificate
active
06538457
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capacitance type displacement detection apparatus and a method of manufacturing the same, in particular, relates to the structure of a detection portion and a signal processing portion thereof.
2. Description of the Related Art
The capacitance type displacement detection apparatus (hereinafter called a capacitance, type sensor) is arranged in a manner that a transmission electrode and a reception electrode are formed on each of two scales provided so as to be able to move relatively to each other. The detection electrode detects that a magnitude of capacitive coupling between the transmission electrode and the reception electrode changes in accordance with the movement of the scale.
FIG. 4
shows the arrangement of the electrode portions of the capacitance type sensor. A transmission electrode
101
a
and detection electrodes
101
b
are formed on a scale
101
of two scales, while a reception electrode is formed on the other scale
102
. The scale
102
on which the reception electrode is formed moves in the directions shown by arrows in the figure and the displacement of this scale is detected by the scale
101
. The transmission electrode
101
a
is formed by arranging a plurality of electrodes. Every predetermined numbers of the plurality of electrodes are coupled commonly. At least three kinds, preferably, eight or more kinds of alternating signals which phases differ by a predetermined phase angle from one another are supplied to the respective commonly coupled portions. When the scale
102
displaces with respect to the scale
101
, the reception electrode generates a composite signal in accordance with the displacement and the detection electrode
101
b
detects the composite signal. The two detection electrodes
101
b
are provided so as to sandwich the transmission electrode
101
a
and output two detection signals which phases differ by 180 degrees to each other. Noise contained in the detection signals can be removed by calculating and using a difference between these detection signals. The detections signals of the two detection electrodes
101
b
are in a differential relationship, so that an amount and the direction of the displacement of the scale
102
relative to the scale
101
can be detected by processing the detection signals in a signal processing portion.
FIG. 5
shows the entire configuration of the capacitance type sensor. The aforesaid scale
101
is provided within a senor portion (detection portion)
110
. The sensor portion
110
is formed by the patterning process on a glass or ceramic board. On the other hand, the signal processing portion is configured as a peripheral circuit board
112
. The signal processing portion supplies, for example, the eight kinds of alternating signals to the transmission electrode
101
a
and receives and processes the detection signal from the detection electrodes
101
b
. The peripheral circuit board
112
includes a detection IC
112
a
and a peripheral circuit
112
b
including a capacitor and a resistor etc. on a plastic board made of epoxy resin etc. The sensor portion
110
and the peripheral circuit board
112
(the signal processing portion) are connected through a flexible printed circuit (FPC)
114
.
In this manner, in the capacitance type sensor of related art, the sensor portion
110
is configured separately from the peripheral circuit board
112
, and the wirings (for example, eight wirings for the transmission side and four wirings for the reception side) are drawn so as to transmit and receive the signals there between. Thus, the longer the drawing distance of the wirings is from the sensor portion to the detection IC
112
a
, the more likely noise mixes into the detection signal, so that there arises a problem that the detection error arises. In particular, since the signal intensity decreases in accordance with the miniaturization of the sensor portion
110
, the influence of the noise on the detection signal becomes larger relatively in accordance with the miniaturization. Accordingly, there arises a problem that the detection accuracy is degraded.
Further, in the related art technique, since the peripheral circuit board
112
serving as the signal processing portion was configured by a resin board made of epoxy resin etc., there arises a problem that it is difficult to further miniaturize the peripheral circuit board due to the restriction of the design rule.
SUMMARY OF THE INVENTION
Accordingly, the invention has been made in view of the aforesaid problems of the related art technique. An object of the invention is to provide a capacitance type displacement detection apparatus and a method of manufacturing thereof which can suppress the mixing of noise by shortening the drawing length of wirings between a detection portion and a signal processing portion and miniaturize the entire size of a sensor.
The object can be achieved by a capacitance type displacement detection apparatus, according to the present invention, comprising:
a detection portion having a transmission electrode and a detection electrode formed thereon which are capacitance-coupled to a reception electrode formed on an opposite scale; and
a signal processing portion which supplies a driving signal to the transmission electrode of the detection portion and receives a detection signal from the detection electrode.
In the apparatus, both the detection portion and the signal processing portion are formed on a board made of silica glass, glass, quartz, ceramic or alumina.
It is preferable that the detection portion is formed on one surface of the board and the signal processing portion is formed on the other surface of the board. Incidentally, the board may be made of composite material of silica glass, glass, quartz, ceramic and alumina.
The object can be also achieved by a method of manufacturing a capacitance type displacement detection apparatus, which includes
a detection portion having a transmission electrode and a detection electrode formed thereon which are capacitance-coupled to a reception electrode formed on an opposite scale; and
a signal processing portion which supplies a driving signal to the transmission electrode of the detection portion and receives a detection signal from the detection electrode. The method comprises the steps of:
sequentially forming a conductive layer and a coupling layer on a board made of silica glass, glass, quartz, ceramic or alumina; and
forming the detection portion on the conductive layer and forming the signal processing portion on the coupling layer to thereby form both the detection portion and the signal processing portion on the board.
Further, the object can be achieved by a method of manufacturing a capacitance type displacement detection apparatus, which includes
a detection portion having a plurality of transmission electrodes and a plurality of detection electrodes formed thereon which are capacitance-coupled to a reception electrode formed on an opposite scale; and
a signal processing portion which supplies a driving signal to the transmission electrodes of the detection portion and receives a detection signal from the detection electrodes. The method comprises the steps of:
forming a conductive layer on each of both surfaces of a board made of silica glass, glass, quartz, ceramic or alumina;
forming a coupling layer on at least one of the both surfaces of the board; and
forming the detection portion on one of the both surfaces of the board and forming the signal processing portion on the coupling layer on other of the both surfaces of the board. In this respect, it is preferable that the coupling layer is made of palladium, solder or nickel. Further, it is preferable that at least part of the signal processing portion is formed on the coupling layer by flip chip, BGA (Ball Grid Array) or CSP (Chip Size Package).
According to the invention, unlike the related art technique, the detection portion and the signal processing portion are not formed on the different boards but commonly formed on
Adachi Satoshi
Nakayama Ken-ichi
Benson Walter
Le N.
Mitutoyo Corporation
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