Measuring and testing – Fluid pressure gauge – With protective separator
Reexamination Certificate
2002-08-23
2003-11-04
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
With protective separator
Reexamination Certificate
active
06640639
ABSTRACT:
PRIORITY CLAIM
The present application claims priority under 35 U.S.C. §119 based upon Japan Patent Application No. JP2001-254920, filed on Aug. 24, 2001.
FIELD OF THE INVENTION
The present invention relates to a pressure sensor for measuring the pressure of a fluid, and particularly relates to a pressure sensor preferably used for measuring the pressure of a corrosive solution, organic solvent, pure water and another liquids, and gases which are used for wet treatments of semiconductors.
BACKGROUND OF THE INVENTION
Conventionally, in the manufacture of semiconductors such as in very large-scale integration, a large number of wet treatments are performed in processes such as washing and etching of surfaces of wafers and the like. In these treatments, corrosive solutions, organic solvents, and pure water and other liquids such as IPA have purity or detergency higher than those which are used for the treatment of ordinary semiconductors. In addition, some gases are sometimes used for in treatments.
In order to measure the pressure of such fluids, a pressure sensor
20
as shown in
FIG. 3
is connected with a tube
22
in which the fluid flows therein by a joint
21
. The pressure sensor
20
is, as shown in
FIG. 4
, composed of a duct
23
in which the fluid from the tube
22
is drawn therein, a sensor element
24
which is provided on the end portion of the duct
23
, and a housing
25
which holds the sensor element. A pressure measuring portion
26
which receives pressure of the fluid is provided on the surface of the sensor element
24
which opposes the duct
23
. Furthermore, an outside of the sensor element
24
is covered by a cap
28
, and the sensor element
24
is held in the housing
25
so as to contact with the pressure measuring portion
26
by the cap
28
.
When the fluid is a corrosive solution, the housing
25
and pressure measuring portion
26
are mainly made of a fluororesin which has a high chemical resistance, and when the fluid is pure water or IPA, the housing
25
is mainly made of metal.
The sensor element
24
has a circuit for converting the stress toward the pressure measuring portion
26
into electrical signals. This circuit includes a Wheatstone bridge circuit composed of four resistors R
1
-R
4
as shown in
FIG. 5
, and an output voltage V
out
is changed to comply with the change of resistors R
1
-R
4
. When no pressure is applied on the sensor element
24
, this output voltage V
out
is zero; however, when pressure is applied on the sensor element
24
and resistance of the resistors R
1
-R
4
changes, the output voltage V
out
also changes, and this value of the output voltage V
out
is converted to the pressure value of the fluid.
As shown in
FIG. 6
, in these resistors R
1
-R
4
, the resistors R
2
and R
4
are provided at a central portion of the sensor element
24
, and the resistors R
1
and R
3
are provided at edge portions of the sensor element
24
. When pressure is applied to the sensor element
24
from the fluid through the pressure measuring portion
26
, the resistors R
2
and R
4
which are provided at the central portion of the sensor element
24
are extended and their resistances increase, and the resistors R
1
and R
3
which are provided at the edge portions of the sensor element
24
are pressed from both sides and their resistances decrease. As a result, the output voltage V
out
also changes to comply with the change of the pressure on the sensor element
24
, and the pressure of the fluid which flows in the tube
22
can be measured from the value of the output voltage V
out
.
When the housing
25
is made of a resin which has high chemical resistance, since the resin is easily electrified, friction occurs between the inner surface of the tube
22
and the fluid which flows in the tube
22
, and static electricity generated by this friction is accumulated in the part in the vicinity of the duct
23
of the housing
25
and the pressure measuring portion
26
. The static electricity accumulated in the pressure measuring portion
26
is discharged to the sensor element
24
in proportion to the operating time of the pressure sensor
20
. As a result, noise is caused in circuits in the sensor element
24
or the circuit is damaged by electrical discharge, and a measurement of the pressure is inadequately performed or cannot be performed. When the housing
25
is made of metal, although the static electricity does not accumulate in the housing
25
, the static electricity still accumulates in the pressure measuring portion
26
and is discharged to the sensor element
24
.
To solve this problem, the structure having a lead wire
29
which connects the cap
28
and a ground is proposed. According to this structure, the static electricity can be released from the pressure measuring portion
26
through the lead wire
29
when a fluid such as the high purity corrosive solution or pure water, or gases, flows in the tube
22
.
However, when the housing
25
is made of a resin which is easily electrified and a fluid which easily generates static electricity such as IPA or other alcohol, or gases, flows in the tube
22
, since static electricity which is higher than the normal level is generated, the static electricity cannot be entirely released through the lead wire
29
since the lead wire
29
is not directly connect with the pressure measuring portion
26
. As a result, the possibility of the discharge of the static electricity still remains.
SUMMARY OF THE INVENTION
The present invention is prepared in consideration of the above circumstances, and a purpose of the present invention is to provide a pressure sensor which has high chemical resistance and high discharge capacity of static electricity.
In order to achieve the above purpose, the pressure sensor of the first aspect of the present invention comprises a pressure measuring portion which is composed of a resin and contacts fluid, and a sensor element which measures pressure imposed on the pressure measuring portion; wherein a conductive layer which is composed of a foil having electric conductivity is provided between the pressure measuring portion and sensor element, and the conductive layer is connected to a ground.
The pressure sensor of the second aspect of the present invention comprises a pressure measuring portion which is composed of a resin and contacts fluid, and a sensor element which measures pressure imposed on the pressure measuring portion; wherein a conductive layer which is composed of meshes having electric conductivity is provided between the pressure measuring portion and sensor element, and the conductive layer is connected to a ground.
According to the pressure sensors having the above structures, the static electricity accumulated in the pressure measuring portion is released from the pressure measuring portion through the conductive layer. Therefore, discharge of the static electricity accumulated in the pressure measuring portion to the sensor element and harmful effect caused by this discharge are prevented.
In the pressure sensors having the above structures, it is preferable that the sensor element be held in a housing of the pressure sensor via a cap which is composed of a material having electric conductivity and is connected to a ground, and that the conductive layer contact the cap.
According to the pressure sensor having the above structure, the sensor element is reliably held in the housing via the cap. Furthermore, the conductive layer provided between the pressure measuring portion and sensor element is easily connected to a ground by contacting the conductive layer with the cap and connecting the cap to a ground. Therefore, the manufacturing and assembly of the pressure sensor are simplified.
REFERENCES:
patent: 6409225 (2002-06-01), Ito
Krebs Robert E.
Oen William
Surpass Industry Co. Ltd.
Thelen Reid & Priest LLP
LandOfFree
Pressure sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pressure sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pressure sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3169956