Sensor and method of producing the same

Details Sensor and method of producing the same Sensor and method of producing the same

1999-11-11

2002-05-07

Kwok, Helen (Department: 2856)

Measuring and testing

Fluid pressure gauge

Diaphragm

Reexamination Certificate

active

06382030

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a sensor such as an electrostatic capacitance type pressure sensor for detecting the pressure of a medium to be measured or acceleration sensor for measuring an acceleration, and a method of manufacturing the same and, more particularly, to an improvement of electrode extraction structures arranged to face each other.
BACKGROUND ART
In an electrostatic capacitance type pressure sensor, a plate-like stationary electrode and movable electrode are arranged parallel and close to each other so as to face each other within the cavity of a sensor main body. A change in capacitance between the two electrodes along with displacement of a diaphragm is detected to measure the pressure of a medium to be measured. Various pressure sensors have conventionally been proposed, as disclosed in Japanese Patent Laid-Open No. 6-265428 (to be referred to as a prior art). The electrode extraction structure in such pressure sensor is generally constituted by bonding a connection pin inserted through a cavity from an electrode extraction hole to an electrode with a bonding agent such as solder or paste (prepared by kneading a metal powder with a binder)
FIG. 12
is a sectional view showing an electrostatic capacitance type pressure sensor described in the prior art.
FIG. 13
is a sectional view taken along the line D-D′ in FIG.
12
.
FIG. 14
is a sectional view taken along the line E-E′ in FIG.
12
.
As shown in
FIG. 12
, a sensor main body
202
is formed by first and second sapphire substrates
202
A and
202
B directly bonded to each other. A stationary electrode
201
and movable electrode
203
are arranged parallel to face each other in the sensor main body
202
. This structure constitutes the electrostatic capacitance type sensor.
The first substrate
202
A is thicker than the second substrate
202
B. Three electrode extraction holes
204
and one atmospheric pressure inlet hole
205
are formed through the first substrate
202
A in the direction of thickness. These holes
204
and
205
allow a cavity
207
formed in the sensor main body
202
to communicate with the outside.
A recess
208
is formed at the center of the inner surface of the second substrate
202
B that faces the first substrate
202
A. A space defined by the recess
208
and the inner surface of the first substrate
202
A forms the cavity
207
. The central portion of the second substrate
202
B is made thin by the recess
208
to form a diaphragm
209
.
The second substrate
202
B is directly bonded to the first substrate
202
A through a thick outer peripheral portion
210
. The first and second substrates
202
A and
202
B are made of the same material, do not sandwich any interposition on their bonded surface, and thus are almost free from any residual stress of bonding. The first and second substrates
202
A and
202
B can be used without causing any change over time which deforms the diaphragm
209
, and can provide stable sensor characteristics.
The movable electrode
203
is made up of a sensing electrode
203
A having pressure sensitivity, and reference electrode
203
B having almost no pressure sensitivity. An output difference between the two electrodes
203
A and
202
B can be detected to cancel the influence of a temperature change and environmental change.
The three electrode extraction holes
204
formed in the first substrate
202
A, i.e., holes
204
a,
204
b,
and
204
c
shown in
FIG. 14
correspond to the stationary electrode
201
, sensing electrode
203
A, and reference electrode
203
B, respectively. The electrode extraction hole
204
a
is formed at a position where the hole
204
a
extends through an electrode extraction portion
214
formed on the stationary electrode
201
. The electrode extraction holes
204
b
and
204
c
are respectively formed at positions corresponding to electrode extraction portions
215
A and
215
B formed on the sensing electrode
203
A and reference electrode
203
B.
Electrode extraction will be described.
FIG. 15
is an enlarged sectional view taken along the line F-F′ in FIG.
13
.
FIG. 16
is an enlarged sectional view taken along the line G-G′ in FIG.
13
.
After the first substrate
202
A is directly bonded to a wafer serving as a substrate material of the second substrate
202
B, the wafer is divided into chips by dicing. Connection pins
211
each having a lower end coated with a solder portion (or conductive paste)
212
are sequentially inserted (in practice, press-inserted) into the electrode extraction holes
204
b
and
204
c
for the movable electrode
203
, and brought into contact with the electrode extraction portions
215
A and
215
B of the sensing electrode
203
A and reference electrode
203
B, respectively. The structure is heated in this state to temporarily fuse the solder portions
212
, and then the solder portions
212
are cooled and solidify. This electrically connects the sensing electrode
203
A and reference electrode
203
B to the connection pins
211
, as shown in FIG.
15
.
Further, as shown in
FIG. 16
, a connection pin
211
having a lower end coated with a conductive paste
213
(or solder portion) is press-inserted into the electrode extraction hole
204
a
for the stationary electrode
201
. The stationary electrode
201
and connection pin
211
are electrically connected through the conductive paste
213
.
DISCLOSURE OF INVENTION
[Problem to be Solved by the Invention]
As described above, in the conventional electrostatic capacitance type pressure sensor, the electrode
201
or
203
is mechanically, electrically connected to the connection pin
211
using the solder portion
212
or conductive paste
213
. This poses the following problems.
More specifically, when the movable electrode
203
is connected to the connection pin
211
using the solder portion
212
as a bonding agent, a sufficient bonding strength cannot be obtained with low wettability of the movable electrode
203
. With high wettability, the solder portion
212
flows from the electrode extraction portion
215
A or
215
B to short-circuit the stationary electrode
201
and movable electrode
203
.
When the conductive paste
213
is used as a bonding agent, a decrease in bonding strength and connection errors occur in an excessively small amount of conductive paste
213
, similar to the solder portion
212
. In an excessively large amount of conductive paste
213
, the conductive paste
213
contacts the stationary electrode
201
to short-circuit the stationary electrode
201
and movable electrode
203
.
On the other hand, when the stationary electrode
201
is connected to the connection pin
211
, the stationary electrode
201
is not formed on the abutment surface of the connection pin
211
, as shown in FIG.
16
. In other words, the stationary electrode
201
is formed on the inner surface of the sensor main body
202
in which the electrode extraction hole
204
a
is formed. For this reason, the solder portion is difficult to electrically connect the stationary electrode
201
.
The stationary electrode
201
may be somehow electrically connected using the conductive paste
213
. However, similar to the movable electrode
203
, the stationary electrode
201
may short-circuit with the movable electrode
203
or fail in connection depending on the amount of conductive paste
213
.
[Means of Solution to the Problem]
The present invention has been made to overcome the conventional drawbacks, and has as its object to realize a sensor having a high bonding strength between an electrode and a connection member such as a connection pin.
It is another object of the present invention to realize a sensor capable of preventing electrodes from short-circuiting with each other.
It is still another object of the present invention to realize a sensor capable of reliably electrically connecting the connection member and electrode.
It is still another object of the present invention to realize a sensor high in yield and excellent in mass production.
To achieve the above obje

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