JPH07101960B2 - Ultrasonic transducer mounting housing and mounting method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic transducer, and more particularly to a mounting housing and a mounting method for an electrostatic airborne ultrasonic transducer used as a proximity sensor for a robot or the like. .

(Prior Art) A phased array ultrasonic transducer does not require mechanical scanning, and can quickly detect the shape of an adjacent object only by electronic scanning. Therefore, it is considered to be optimal as a control device for accurately controlling the robot hand under the invisible environment such as smoke and the collision prevention during movement. At present, an acoustic image technology using an ultrasonic transducer is widely used as a sonar, a CT scanner, etc. in the underwater and medical fields.

However, ultrasonic transducers using piezoelectric ceramic technology, which has been widely used in the past, have problems in impedance matching with air, high-speed response, and the like, and it is difficult to directly apply this technology in the air. It was Further, since this type of ultrasonic transducer is a resonance type, it is difficult to make the characteristics of individual elements uniform.

The cell type transducer is a kind of condenser microphone and condenser speaker, and has been developed from the beginning for use in the air. The cell type transducer is composed of an organic vibrating film having a back electrode having many grooves on the surface and an electrode facing the back electrode. This electrostatic transducer enables good impedance matching with air and high-speed response.

FIG. 3 and FIG. 4 are a sectional view and a configuration diagram showing an example of the configuration of a conventional ultrasonic transducer based on the principle of this cell. In these figures, 1 is a circular aluminum alloy plate, and a plurality of holes having a depth of several to several tens of μm are formed on the surface by machining. On the upper surface of this hole, a polyester film 2 having a thickness of 6 to 20 μm is fixed by being sandwiched between a housing (metal case) 3 and a middle cylinder (plastic case) 4. On the surface of the polyester film 2, an electrode (not shown) made of gold or the like is vapor-deposited on the surface opposite to the surface in contact with the aluminum alloy plate 1. On the other hand, a leaf spring 5 made of metal is attached to the back surface of the aluminum alloy plate 1, and the aluminum alloy plate 1 is pressed against the polyester film 2. The leaf spring 5 is fixed to the middle cylinder 4. Reference numerals 6 and 7 are electrode terminals, 6 is integrated with the leaf spring 5, and 7 is integrated with the housing 3. Therefore, the potential of the electrode terminal 6 is equal to that of the aluminum alloy plate 1 through the leaf spring 5, while the potential of the electrode terminal 7 is equal to that of the electrode deposited on the polyester film 2 through the housing 3. As a result, when a voltage is applied between the electrode terminals 6 and 7, a voltage equal to this applied voltage is generated between the aluminum alloy plate 1 and the electrodes vapor-deposited on the polyester film 2, and the electrostatic force causes the polyester film 2 to form. Displace.
Therefore, when the voltage applied between the electrode terminals 6 and 7 is an AC signal, the electrostatic force acting on the polyester film 2 is also changed by the AC, and the polyester film 2 is vibrated.
Ultrasonic waves are emitted to the front.

FIG. 5 is a diagram showing the operating principle of the electrostatic ultrasonic transducer described in FIG. 3 and FIG.
It is composed of 11 and electrical elements 12. Mechanical elements 11
Is composed of a vibrating plate 11a and a fixed plate 11b, and has, for example, the structure shown in FIG. In FIGS. 3 and 4, the polyester film 2 constitutes the diaphragm 11a, and the aluminum alloy plate 1 constitutes the fixed plate 11b. On the other hand, in the case of ultrasonic wave transmission, the electrical element 12 has a DC bias voltage 1
3, high resistance 14, coupling capacitance 15 and oscillator circuit 16. When the oscillator circuit 16 has no signal, the diaphragm 11a is attracted to the fixed plate 11b by the DC bias voltage 13.
Next, when the oscillation circuit 16 generates an AC voltage having a smaller amplitude than the DC bias voltage 13, the deflection of the diaphragm 11a is
It changes as follows depending on the polarity of the signal voltage generated at both ends of the oscillator circuit 16. That is, when the polarity of the voltage generated across the oscillation circuit 16 is the same as the DC bias voltage 13, a voltage equal to the sum of these voltages is applied between the diaphragm 11a and the fixed plate 11b, so that the diaphragm 11a is not bent. It will be bigger than the signal. On the other hand, when the polarity of the voltage of the oscillation circuit 16 is opposite to that of the DC bias voltage 13, the voltage obtained by subtracting the signal voltage from the DC bias voltage is applied between the diaphragm 11a and the fixed plate 11b, so that the deflection of the diaphragm 11a Is smaller than when there is no signal. Therefore, when the signal voltage of the oscillation circuit 16 is periodically changed, the diaphragm 11a vibrates and ultrasonic waves are radiated to the front surface. The case of transmitting ultrasonic waves has been described above.
In the case of receiving waves, 16 in FIG. 5 may be used as a receiving circuit that performs impedance conversion, amplification, band limitation for noise removal, and the like. At this time, due to the ultrasonic waves incident from the outside,
Since the diaphragm 11a vibrates and the capacitance value between the diaphragm 11a and the fixed plate 11b changes, the charging current from the DC bias voltage 13 changes. This change in the charging current is acoustically-electrically converted as a change in the voltage between the terminals of the high resistance 14, so that the reception circuit can receive the ultrasonic waves by impedance conversion, amplification, and band limitation.

Heretofore, an example of the conventional electrostatic ultrasonic transducer has been described. However, in the ultrasonic transducers shown in FIG. 3 and FIG. 4, since machining was used when machining the holes on the surface of the aluminum alloy plate 1,
It was impossible to avoid variations in the dimensions and shapes of the holes. The hole on the surface of the aluminum alloy plate 1 corresponds to the gap between the vibrating plate 11a and the fixed plate 11b shown in FIG. 5, and if the size or shape varies, the driving force of the vibrating plate 11a varies. However, when a phased array ultrasonic transducer is constructed, there is a drawback that the ultrasonic transmission / reception characteristics between the array elements are not constant. Also, FIG. 3 and FIG.
If the above-described conventional structure shown in the figure is used to realize the above-mentioned phased array ultrasonic transducer, there is a problem that the size of the device is inevitable. For example,
The wiring that connects the electrodes of the arrayed transducer is
It will be quite large.

FIG. 6 is a structural schematic cross-sectional view showing an example of an electrostatic silicon ultrasonic transducer element utilizing the silicon micromachining technology proposed under such a background. In this silicon ultrasonic transducer, a fixed electrode 24 is formed on a minute etching hole 22 formed by etching on the surface of a silicon substrate 21 via an oxide film 23, and an organic thin film 26 is further formed thereon via an oxide film 25. A vibrating electrode (27) made of a metal foil vapor-deposited on is attached to the structure, and air is confined in minute etching holes (22).

Since this silicon ultrasonic transducer uses a silicon substrate, it is possible to accurately form micro holes on the silicon substrate by using silicon micromachining technology, and reduce the variation in characteristics between each element of the arrayed transducer. can do. Also, if a silicon substrate is used, the electrical element 12 shown in FIG.
Since it can be integrated using a manufacturing process, it is expected that the phased array ultrasonic transducer will be smaller and lighter.

Next, an example of a conventional method of manufacturing this silicon ultrasonic transducer will be described with reference to FIGS. 7 (a) to 7 (d).
First, for example, on the surface of a silicon substrate 21 having a plane orientation (100), by using anisotropic etching using hydrazine or the like with the oxide film 28 as a mask, one side of the opening has a square shape of a few tens of μm square. Etching holes 22 are formed (FIG. 7 (a)). Next, the oxide film 28 is completely removed, and the oxide film 23 is newly grown by thermal oxidation, and then fixed electrodes 24 of aluminum are formed in an array on the oxide film 23 (FIG. 7B). After that, an oxide film 25 is further deposited by the CVD method to form an interlayer insulating film (FIG. 7 (c)). After the silicon substrate 21 is separated into chips, it is die-bonded to the ceramic package 20 and each fixed electrode is connected to the lead by wire bonding. Finally, the organic thin film 26 made of a polyester film having a thickness of several to several tens of μm, on which the aluminum vibrating electrode 27 is vapor-deposited, is stretched and fixed (bonded) to the aluminum frame 29. In this state, the aluminum frame 29 is fixed (screwed) to the ceramic package 20 with the screw 30 (FIG. 7 (d)).

(Problems to be Solved by the Invention) The conventional silicon ultrasonic transducer has been described above with reference to specific examples. However, in the element mounting using the conventional ceramic package 20, one side is fixed in the process of stretching and stretching the organic thin film 26 on the chip, and one of the organic thin film 26 is stretched with a jig such as a weight or a spring to form an aluminum frame. After bonding 29, the film was cut along the frame 29, and the frame 29 was screwed to the ceramic package 20. Therefore, workability in the mounting process was poor. Further, when screwed, a force parallel to the film surface is applied to the organic thin film 26, which may cause wrinkles on the thin film 26, resulting in poor reproducibility. In addition, the organic thin film 26 and the bonding wire (not shown) are exposed, and there is a drawback that no protective measures are taken against them.

The method of mounting the ultrasonic transducer shown in FIGS. 3 and 4 is effective for solving the above-mentioned drawbacks. With this mounting method, the polyester film 2 is automatically attached without any adhesive when the middle cylinder 4 is fitted into the housing 3.
The stretching of the film can be realized by pushing the aluminum alloy plate 1 with the leaf spring 5.

However, in the array type silicon ultrasonic transducer described with reference to FIGS. 6 and 7, the fixed electrode 24 is not the circular aluminum alloy plate 1 but the aluminum electrode patterned on the silicon substrate 21, and the array structure. Therefore, it is necessary to take out the lead from each electrode independently,
Further, there are restrictions such as the need to avoid the bonding wires and form a film, and it was impossible to directly adopt the mounting technique of the ultrasonic transducer shown in FIGS. 3 and 4.

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional silicon ultrasonic transducer, improve workability and reproducibility in the mounting process, and protect the organic thin film and the bonding wire, which is flexible. An object of the present invention is to provide an ultrasonic transducer mounting housing and mounting method.

(Means for Solving the Problem) An ultrasonic transducer mounting housing of the present invention includes an organic thin film having a first electrode on one surface and a second organic thin film arranged on the surface of a semiconductor substrate having a plurality of holes. And a groove formed in the housing for inserting both ends of the organic thin film, and the organic thin film arranged in the groove. An elastic rod placed on top, a pressing plate for fixing the organic thin film by pressing the organic thin film and the elastic rod by being screwed to the housing, and the semiconductor substrate are mounted. And a mechanism for supporting the printed circuit board and pressing it against the organic thin film.

The print support portion for accommodating and fixing the printed board on which the semiconductor substrate is mounted in the housing is, for example, a convex portion formed in the housing.

A mechanism for supporting the printed circuit board and pressing it against the organic thin film is, for example, a leaf spring longer than the printed circuit board, and a leaf spring insertion guide for inserting the plate springs provided on both side surfaces of the housing. In this configuration, the leaf spring is inserted into the leaf spring insertion guide to bend the leaf spring, thereby supporting the printed circuit board and pressing the organic thin film.

An ultrasonic transducer mounting method of the present invention is a method of mounting an ultrasonic transducer having a second electrode arranged on a surface of a semiconductor substrate having a plurality of holes in the mounting housing, wherein Put both ends of the thin film in the groove of the housing and press it from above with the elastic rod to press the rod with the pressing plate and screw the pressing plate, and then mount the printed circuit board with the semiconductor substrate. The side is applied to the organic thin film, the leaf spring is inserted into the guide, and the opposite surface of the printed board is pressed.

(Function) In the present invention, unlike the prior art, the part (protective cover) that protects the front surface of the chip, the part (the printed board to which the chip is bonded), and the part that supports and fixes the organic thin film are integrated. There is. Therefore, the step of adhering the organic thin film to the frame becomes unnecessary, and the organic thin film can be housed in the housing and the workability is remarkably improved. Further, when the organic thin film is stretched, the thin film is sandwiched in the groove and pressed by an elastic rod from above, instead of holding it by a frame whose flat surface is in contact with the thin film as in the conventional case. Therefore, when screwing, the force in the direction parallel to the film surface is less likely to be applied to the thin film, the waviness of the thin film is greatly reduced, and the reproducibility of the work is improved. Further, when the thin film is stretched and fixed and the printed circuit board is mounted, the bonding wire and the organic thin film have already been protected. Further, in the present invention, since the organic thin film is fixed to the housing and then the printed circuit board is mounted, it is easy to mount the printed circuit board while avoiding the bonding pad and the bonding wire of the semiconductor substrate, and the work is flexible.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1A and 1B are drawings showing an embodiment of a housing for mounting an ultrasonic transducer of the present invention. FIG. 1A is a front view of the housing of this embodiment, and FIG. -A sectional view taken along arrow A,
(C) is the figure which looked at this housing from the back surface, (d) is a side view of this housing. In FIG. 1, a protective cover 31 for protecting the front surface, a stopper region 32, a printed circuit board supporting portion 33, a groove having a V-shaped cross section (hereinafter abbreviated as V groove) 34, screw holes 35 provided on both sides thereof, and a plate. The spring insertion guide 36 is integrally formed. The case is made of aluminum. The protective cover 31 is provided to protect the organic thin film and the silicon substrate of the silicon ultrasonic transducer mounted in the casing, and is processed into a thin shape in order to pass radiated and incident ultrasonic waves without attenuation. At the same time, a large number of through holes 37 are formed. In order to avoid complication of the drawings, the minute holes 37 are partially omitted in FIGS. 1 and 2. Also, the V groove 34 and the screw hole provided in the stopper area 32
The numeral 35 is provided to fix the rectangular organic thin film forming the ultrasonic transducer at both ends of the mounting housing, and a rubber round bar and a pressing plate are used for fixing, as described later. The printed circuit board supporting portion 33 is a convex portion formed at the four corners of the back surface of the housing, and the printed circuit board to which the silicon substrate forming the ultrasonic transducer is die-bonded is surrounded by the printed circuit board supporting portion 33. Both ends of the surface on the side where there is are accommodated in the housing in a state of contacting the stopper region 32.

Next, an example of the mounting method of the ultrasonic transducer of the present invention when the case shown in FIG. 1 is used will be described with reference to FIG.

In the figure, (a) is a front view of the housing after mounting,
(B) is the AA arrow sectional view, (c) is the figure seen from the back surface, (d) is CC sectional view. In the figure, 41
Is a rectangular organic thin film, 42 is a chip-separated silicon substrate, 43 is a printed circuit board, 44 is a rubber round bar, 45 is a holding plate, 46 is a set screw, and 47 is a plate screw. Further, the components denoted by the same reference numerals as those in FIG.
The same components as in the figure are shown.

In this embodiment, in the mounting method, first, the organic thin film 41 is put in the V groove 34, a rubber round bar 44 is placed on the organic thin film 41, and a pressing plate 45 is pressed from above and fixed by a set screw 46. Next, the printed board 43 is housed in the housing in such a manner that the printed board 43 is surrounded by the printed board supporting portions 33 formed at the four corners of the back surface of the housing and both ends of the surface on the side where the silicon substrate is present are in contact with the stopper regions 32. The front side of the printed circuit board 43 is a silicon substrate after chip separation.
42 is die-bonded and wire-bonded. Finally, the leaf springs 47 are inserted into the leaf spring insertion guides 36 provided on both sides of the casing to fix the printed circuit board 43 to the casing body.

In this embodiment, the organic thin film 41 is sandwiched between the rubber round bar 44 and the pressing plate 45 placed in the V groove 34 and fixed by the set screw 46. There is no need to stretch the machine body thin film and adhere the organic thin film to the aluminum frame, and the workability and reproducibility of the mounting process are improved. Further, the organic thin film 41, the silicon substrate 42, and the bonding wires (not shown) that form the device are protected by the protective cover 31 that is integrally formed with the housing. Furthermore, since the organic thin film 41 is fixed at both ends, there is flexibility in the work process, and by adjusting the mutual positional relationship between the silicon substrate 42 mounted on the printed board 43 and the organic thin film 41, It is possible to stretch the organic thin film while avoiding the bonding pad and the bonding wire area of the silicon substrate.

Therefore, according to the present embodiment, all the drawbacks of the prior art are solved, workability, reproducibility and flexibility in the mounting process are excellent, and the organic thin film, the silicon substrate and the bonding line which form the device are A protected silicon ultrasonic transducer is realized.

In this embodiment, a rubber round bar is used as the elastic rod, but elastic plastic may be used instead of rubber.
Polygonal rods may be used instead of round rods.

As described above, according to the present invention, workability in the mounting process
A semiconductor ultrasonic transducer having excellent reproducibility and flexibility, in which the organic thin film, the semiconductor substrate and the bonding line are protected is realized, and the effect of reducing the size and weight of the phased array aerial ultrasonic transducer is great.

[Brief description of drawings]

1 (a) to 1 (d) are views showing an embodiment of an ultrasonic transducer mounting housing according to the present invention, and FIGS. 2 (a) to 2 (d).
(D) is a diagram showing an embodiment of the ultrasonic transducer mounting method according to the present invention, FIGS. 3 and 4 are sectional views and configuration diagrams of a conventional ultrasonic transducer, and FIG. 5 is a conventional electrostatic type ultrasonic transducer. FIGS. 6 and 7 (a) to 7 (d) are diagrams showing the structure and manufacturing method of a conventional silicon ultrasonic transducer. 1 ... Aluminum alloy plate, 2 ... Polyester film, 3 ...
Housing, 4 ... Middle cylinder, 5 ... Leaf spring, 6,7 ... Electrode terminal, 11 ... Mechanical element, 11a ... Vibration plate, 11b ... Fixed plate, 12 ... Electrical element, 13 ... … DC bias voltage, 14…
… High resistance, 15 …… Coupling capacitance, 16 …… Oscillation circuit, 20 …… Ceramic package, 21 …… Silicon substrate, 22 …… Etching hole, 23 …… Oxide film, 24 …… Fixed electrode, 25 …… Interlayer Insulating film, 26 …… Organic thin film, 27 …… Vibrating electrode, 28 …… Mask oxide film, 29 …… Aluminum frame, 30 …… Screw, 31
...... Protective cover, 32 ...... Stopper area, 33 ...... Printed circuit board support, 34 ...... V groove, 35 ...... Screw hole, 36 ...... Leaf spring insertion guide, 37 ...... Micro hole, 41 ...... Organic material Thin film, 42 ……
Silicon substrate, 43 ... Printed circuit board, 44 ... Rubber round bar, 45 ... Holding plate, 46 ... Set screw, 47 ... Leaf spring.

Claims (4)

[Claims] 1. An organic thin film having a first electrode on one surface, and a second thin film arranged on the surface of a semiconductor substrate having a plurality of holes.
And a groove formed in the housing for inserting both ends of the organic thin film, and the organic thin film arranged in the groove. A rod of an elastic body placed on, a pressing plate for fixing the organic thin film by pressing the organic thin film and the elastic rod by being screwed to the housing,
An ultrasonic transducer mounting, comprising: a print supporting unit that accommodates and fixes a printed circuit board on which the semiconductor substrate is mounted in the housing; and a mechanism that supports the printed circuit board and presses it against the organic thin film. Case. 2. The ultrasonic transducer mounting casing according to claim 1, wherein the print supporting portion for accommodating and fixing the printed substrate on which the semiconductor substrate is mounted in the casing is a convex portion formed in the casing. 3. A mechanism for supporting the printed circuit board and pressing it against the organic thin film, a leaf spring longer than the printed circuit board, and a leaf spring for inserting the leaf springs provided on both side surfaces of the housing. 3. An insertion guide, wherein the leaf spring is inserted into the leaf guide to bend the leaf spring to support the printed circuit board and press the organic thin film. Ultrasonic transducer mounting housing. 4. A method for mounting an ultrasonic transducer having a second electrode disposed on a surface of a semiconductor substrate having a plurality of holes in a mounting housing according to claim 3, wherein the organic thin film is formed of: Put both sides in the groove of the housing and press from above with the rod of the elastic body, press the rod with the pressing plate and screw the pressing plate, then place the printed board on the side on which the semiconductor substrate is mounted. A method for mounting an ultrasonic transducer, wherein the leaf spring is applied to the organic thin film and the leaf spring is inserted into the guide to press and fix the opposite surface of the printed board.