JPH04209579A - Mounting method for piezoelectric transformer - Google Patents

Abstract

PURPOSE:To mount without reducing a Q value of a piezoelectric vibration by connecting one of two insular electrodes formed in a gap of one surface of a piezoelectric board to an input electrode, the other to an output electrode, and connecting the insular electrodes to a member for wirings by conductively securing means. CONSTITUTION:Gaps 6 to become a node of a vibration remains on front and rear surfaces of a piezoelectric board 1a, insular electrodes 7a and 7c, 7b and 7d are formed in the gaps 6, and the electrodes 7b, 7d are respectively connected to an input electrode 2d, an output electrode 3d. Simultaneously, these electrodes 7a, 7c are connected to members 12 for wirings of supporting/wiring members 9 through conductively securing means 8. Leads 10 are connected through the electrodes 7a, 7c, a board 1a is supported and secured by the electrodes 7b, 7d to eliminate influence of vibration to the supporting, securing, and the leads are connected to the electrodes 7a, 7c to provide a mounting method for a piezoelectric transformer having a small decrease in a Q value of a piezoelectric vibration.

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a piezoelectric transformer in a device such as an electronic device or a special package. [0002] Piezoelectric transformers are suitable for use in high voltage generating parts of devices that require high voltage but consume little power. For example, it can be used for the following purposes: [0003] ■High voltage power supply for CRT of TV receiver. ■Power supply for toner charging of electronic copying machines. ■High voltage power supply for electrostatic printing. ■Power supply for piezoelectric actuators.
**■High voltage generator of electron microscopes and X-ray equipment. [0004] By the way, piezoelectric transformers can be made smaller and lighter, and since there is no leakage flux, they do not generate electromagnetic noise. [0005] For this reason, research into practical application is being actively conducted with a view to use and installation in electronic equipment, where demands for lightness, thinness, and miniaturization are increasing. [0006] - In boat fishing, the step-up ratio of a piezoelectric transformer is proportional to the electromechanical coupling coefficient of the piezoelectric effect and the magnitude of the mechanical Q. [0007] The magnitude of L and mechanical Q is influenced and reduced by the mounting method for supporting and fixing the piezoelectric transformer being ultrasonically excited. [0008] Therefore, in order to obtain a highly efficient piezoelectric transformer, there is a need for a mounting method that reduces the decrease in the magnitude of mechanical Q. [0009]

[Prior Art] FIG. 5 is a diagram illustrating a piezoelectric transformer.
(a) is a perspective view of a piezoelectric transformer, and (b) is a view of (a) seen from the front side of the figure. [00101 The piezoelectric transformer shown in Fig. 5 is a piezoelectric transformer that utilizes the transverse effect longitudinal vibration mode, and the piezoelectric transformer is
It was invented by Atsushi Nakamura of Tohoku University and the present inventors, and a patent application has already been filed by the present applicant and others. By the way, the piezoelectric transformer shown in the same figure uses transverse effects on both the input electrode side and the output electrode side, so the transverse
Corresponds to a transverse effect type transformer. [00111 A piezoelectric transformer using a transverse effect longitudinal vibration mode uses a piezoelectric substrate l polarized in a negative direction, so it can withstand large amplitude excitation, operates with high efficiency, and has high reliability. [0012] Incidentally, the piezoelectric transformer shown in FIG. 5 is a piezoelectric transformer that operates in a half-wavelength resonance mode, and the piezoelectric substrate 1
On both sides of the input electrodes 2a, centered around the vibration node 15,
2b and output electrodes 3a and 3b. [0013] Note that the standing wave 5 is generated as shown by the broken line in FIG. 5(b). Further, the step-up ratio of this piezoelectric transformer is calculated by the following formula (1
) can be shown. [0014] However, KI, K. is the electromechanical coupling coefficient of the piezoelectric effect of the input section and the output section, Q is the mechanical vibration Q of the piezoelectric transformer, L, , L+ is the distance between the electrodes at the input section and the output section. [0015] Therefore, KI, K. ,L. ,L+
If is a constant value, the boost ratio is proportional to the value of Q. [0016] By the way, the value of Q is about 2000 to 3000 for piezoelectric ceramics, and 1 for piezoelectric single crystals.
It is about 0000. [0017] By the way, in order to actually use the piezoelectric transformer, the piezoelectric substrate 1 on which the input/output electrodes 2a, 2b, 3a, and 3b are formed is supported and fixed, and the input/output electrodes 2a
, 2b, 3a, and 3b for wiring. [0018] In the piezoelectric transformer of FIG. 5, the support part 4 is bonded and fixed to the end of the input electrode 2b closest to the vibration node 15, and the input/output electrodes 2a, 2 closest to the vibration node 15 are attached.
Node wires are drawn out from nodes b, 3a, and 3b so that the support portion 4 and the lead wires do not affect the vibration of the piezoelectric substrate 1. [0019]

[Problem to be Solved by the Invention] However, the Q of mechanical vibration of a piezoelectric transformer is greatly influenced by how the piezoelectric transformer (piezoelectric substrate 1) is supported and fixed, and how it is wired. and decrease. [0020] The decrease in Q was hardly a problem while piezoelectric ceramic was used as the material for the piezoelectric substrate 1, but it has emerged as an important problem since piezoelectric single crystals have been used. [0021] That is, in a piezoelectric ceramic having a Q value of about 2000 to 3000, the rate of decrease in Q due to support and fixation of the piezoelectric substrate 1 was small and negligible. However, in a piezoelectric single crystal with a Q value of about 10,000, the rate of decrease in Q is large and cannot be ignored. [0022] Also, a decrease in Q occurs when the lead wires are drawn out from the input electrodes 2a, 2b and the output electrodes 3a, 3b, and the larger the value of Q, the greater the rate of decrease.
This cannot be ignored [0023] In other words, the excellent property of the piezoelectric single crystal, which has a large Q value, cannot be fully utilized. [0024] Therefore, for a piezoelectric transformer with a Q value of 10,000 or more, there is no known example of a supporting/fixing method and a method of drawing out lead wires, that is, a mounting method that takes advantage of the characteristics of the piezoelectric transformer. [0025] The technical problem of the present invention is to solve the above-mentioned problems in piezoelectric transformers and to establish a mounting method with less Q drop, thereby realizing a piezoelectric transformer with a large step-up ratio and high efficiency. be. [0026]

[Means for Solving the Problems] Fig. 1 is a diagram explaining the basic principle of the present invention, in which (a) is a view of a piezoelectric transformer seen from one side, and (b) is a view of the piezoelectric transformer seen from one side. View from the side, (
C) is a side view of (a), and (d) is a diagram illustrating a state in which a piezoelectric transformer is mounted. [0027] The mounting method of the present invention is characterized in that the electrode for wiring and the member for support are used as both. [0028] (1) Mounting method that uses both a support member and a wiring member This mounting method utilizes only transverse effect longitudinal vibration and is a method of mounting a piezoelectric transformer that operates in a half-wavelength resonance mode, which reduces vibration. Input electrodes 2c, 2d and output electrodes 3c, 3d are formed on both sides of the piezoelectric substrate 1a, leaving a gap 6 at the position of the node 15.
It is assumed that a piezoelectric transformer is formed. [0029] Then, two island-like electrodes 7b and 7d are formed in the gap 6 on one surface of the piezoelectric substrate 1a, and one of the island-like electrodes 7b and 7d is connected to the input @t? on the same surface. M2d, and the other of the island-shaped molds 17b and 7d is connected to the output electrode 3d on the same surface.
Connect to. [00301] On the other hand, a support/wiring member 9 having a wiring member 12 at a position facing the two island-like electrodes 7b and 7d is prepared. [00311 And the island shape of the piezoelectric transformer @1I7
This is a mounting method in which the wiring member 12 of the support/wiring member 9 is connected to the wiring member 12 of the support/wiring member 9 using conductive fixing means 8. [0032] (2) Mounting method for connecting lead wires In the mounting method of (1) above, two island-shaped molds 1i7a and 7c are also formed in the gap 6 on the other surface of the piezoelectric substrate 1a,
One of the island electrodes 7a and 7c is connected to the input @frM2 on the same plane.
c, and the other of the island electrodes 7a, 7c is connected to the output electrode 3c on the same surface. [0033] And, there is a method of mounting a piezoelectric transformer in which lead wires 10 are connected to the island-shaped electrodes 7a and 7c. [0034] (3) Mounting method to prevent island-shaped electrodes from facing each other In the mounting method of (2) above, the arrangement positions of island-shaped electrodes 7b and 7d formed on one surface of piezoelectric substrate 1a and the other This is a piezoelectric transformer mounting method in which the island-like electrodes 7a and 7c formed on the surface are arranged at positions that do not face each other with the piezoelectric substrate 1a in between. [0035]

[Function] (1) Mounting method that serves both as a support member and a wiring member The gap 6 serves as a vibration node 15 of the piezoelectric substrate 1a. That is, no vibration occurs at the center position of the gap 6. [0036] Therefore, the island-shaped electrode 7 provided in the gap 6
By supporting and fixing the piezoelectric substrate 1a with points b and 7d, the support and fixation do not affect vibration. Therefore, the amount of decrease in Q of the piezoelectric transformer (piezoelectric substrate 1a) is small. [0037] By the way, from the center position of the gap 6,
Longitudinal vibration appears as it moves away from the left or right side in the upward direction of the figure, and the magnitude of the vibration amplitude gradually increases as it moves away from the figure. Note that the phase of vibration differs by 1800 between the left and right positions. [0038] That is, actually the island-shaped electrodes 7b, 7d
Since it has a finite area, it will be affected by the longitudinal vibration. [0039] In the L-shaped electrodes 7b and 7d, the phase of the longitudinal vibration distributed in the left-right direction is 180°.
Since they are different, the combined value of the vibrations within the island electrodes 7b and 7d is O (zero), and there is no fear that the island electrodes 7b and 7d will peel off from the piezoelectric substrate 1a. [00401 Again. A conductive fixing means 8 is used to connect the island-like electrodes 7b, 7d to a support/wiring member 9 having a wiring member 12. [00411 Therefore, via the conductive fixing means 8 and the wiring member 12 of the support/wiring member 9, the input @'rTA2
Wiring between d and the output electrode 3d can also be performed at the same time. [0042] The gap portion 6 is provided in order to ensure electrical isolation between the input electrodes 2c, 2d and the output electrodes 3c, 3d. [0043] (2) Mounting method for connecting lead wires This method is a mounting method for connecting lead wires, and its basic principle and operation are the same as in (1) above. [0044] That is, the island-shaped ti7 provided in the gap 6
By connecting the lead wire 10 via a and 7c, the amount of decrease in Q of the piezoelectric transformer (piezoelectric substrate 1a) can be minimized. [0045] In addition, input/output electrodes 2c, 2d, 3c,
3d is provided on both sides of the piezoelectric substrate 1a, the above (1)
) and this mounting method, the mounting of one piezoelectric transformer is completed. [0046] (3) Mounting method to prevent island-shaped electrodes from facing each other The island-shaped electrodes ti7b, 7d on one side provided in the gap 6 and the island-shaped electrodes 7a, 7c on the other side are connected to the piezoelectric substrate 1a. When the piezoelectric substrates 1a are opposed to each other, an electric field due to the input voltage or the output voltage is also applied to the piezoelectric substrate 1a of the opposing portion. [0047] Therefore, vibrations due to the piezoelectric effect also occur in the piezoelectric substrate 1a of the opposing portion, and the vibrations become spurious vibrations that reduce the efficiency of the piezoelectric transformer. [0048] That is, as in this mounting method, the island-shaped electrode 7
By arranging the elements a, 7b, 7c, and 7d so that they do not face each other, it is possible to suppress the generation of spurious vibrations. [0049]

[Example] Next, how the mounting method according to the present invention can be practically implemented will be explained using an example. [00501 FIG. 2 is a diagram for explaining Example-1, and shows the configuration of a piezoelectric transformer. (a) is a view of the piezoelectric transformer viewed from one side, (b) is a view of the piezoelectric transformer viewed from the opposite side of (a), (c) is a view of (a) viewed from the side, (d) ) is a diagram explaining the land shape. [00511 In addition, FIG. 3 is also a diagram for explaining Example-1,
This shows the mounting state of the piezoelectric transformer. In addition, (a) is a view seen from the long side side of the piezoelectric transformer, (b) is a view seen from the short side side of the piezoelectric transformer, and (c) is a view of the land on the printed circuit board side and the side view on the piezoelectric transformer side. FIG. 3 is a diagram illustrating the positional relationship with the land. [0052] (1) Structure of piezoelectric transformer (FIG. 2) A 1400 rotation Y plate of LiNbO3 single crystal was used as the piezoelectric substrate 1b. And its dimensions are length Ll = 3
0mm, width L2 is 7mm, thickness L3 is 0.5mm
It was designed to. Incidentally, the target half-wavelength resonance frequency in the design value is 100 KHz. [0053] In addition, the input electrodes 2e, 2f and the output electrode 3
The width of the gap 6a separated by e and 3f is 1 mm, and the gap 6a is provided at the center position in the length L1 direction. [0054] On the other hand, input electrodes 2e, 2f and output electrode 3e
, 3f, and each input/output electrode 2e, 2f, 3e,
Lands 7e and 7f connect to 3f. 7g and 7h are formed simultaneously by vacuum evaporation. [0055] Note that the distance L4 between the land 7e connected to the input electrode 2e and the land 7g connected to the output electrode 3e is 3 mm, and the distance L4 between the land 7e connected to the input electrode 2e and the land 7g connected to the output electrode 3e is 3 mm.
The distance between the land 7h and the land 7h connected to the land 7h is 1 mm. Further, each of the lands 7e, 7f, 7g, and 7h had a square shape, and the length L of each side was 30071 m. [0056] And each of the input/output electrodes 2e, 2f,
3e, 3f and lands 7e, 7f, 7g,
In the 7h formation step, first, NiCr is formed to a thickness of 30 nm, and then Au is formed to a thickness of 1 on the NiCr layer.
00 nm to complete the formation. [0057] (2) Mounting a piezoelectric transformer on a printed circuit board (FIG. 3) In this example, the piezoelectric transformer shown in (1) above is mounted by soldering onto a printed circuit board 11 on which patterns 12a and 12b are formed. Then, the piezoelectric transformer is also wired, supported, and fixed. [0058] Note that lands 13a and 13b are provided on the printed circuit board 11, and are formed to match the pitch L5 of the lands 7f and 7h of the piezoelectric transformer.
Patterns 12a and 12b are extracted from 3a and L3b. [0059] That is, the land 7r of the piezoelectric transformer and the land 13a of the printed circuit board 11 are soldered using the solder 8a, and the land 7h of the piezoelectric transformer and the land 13b of the printed circuit board 11 are soldered using the solder 8a. [00601 As a result, the piezoelectric transformer is connected to the printed circuit board 1
At the same time, the pattern 12a, 1
Wiring between the input electrode 2f and the output electrode 3f is completed via the input electrode 2b. [00611] On the other hand, the wiring between the input electrode 2e and the output electrode 3e is performed using Au wires 10a and 10b. That is, the Au wire 10a is bonded to the land 7e of the piezoelectric transformer, and the Au wire 10b is bonded to the land 7g of the piezoelectric transformer. Note that the bonding may be done by soldering. [0062] In place of the solder 8a, it is also possible to use the conductive paste 8b or conductive adhesive 8C shown in FIG. [0063] (3) Mounting result As a result of mounting the piezoelectric transformer of (1) above according to (2) above, a voltage doubler rectifier circuit was provided on the output side of the piezoelectric transformer, the load resistance was 100 MΩ, and the load capacity was 4700 P F
In this case, the boost ratio was approximately 800. In addition, the Q of the piezoelectric transformer achieved over 10,000. [00641 The above measurement value is an extremely excellent value as a measurement value obtained by mounting a piezoelectric transformer using a piezoelectric single crystal in accordance with actual usage conditions. [0065] (4) Other Examples FIG. 4 is a diagram for explaining Example-2, (a) is a diagram for explaining the case of soldering in Example-1, and (b) is a diagram for explaining Example-2. A diagram explaining the case where it is supported and fixed with an insulating adhesive,
It is. Note that (a) is illustrated for comparison with Example-2 in (b). [0066] This Example-2 is based on the solder 8a of Example-1.
Instead, an insulating adhesive 14 is used. [0067] That is, in Example-1, the land 7f (7h) of the piezoelectric transformer and the land 13a of the printed circuit board
The connection with (13b) is made by the resistive molecule of the solder 8a in an equisimplified manner, and substantially rn≠0. [0068] On the other hand, in this Example-2, the insulating adhesive 14
Therefore, the connection between the land 7f (7h) of the piezoelectric transformer and the land 13a (13b) of the printed circuit board is simply made by the capacitance (capacitor) Cs using the insulating adhesive 14 as the dielectric. Connected. [0069] Therefore, with respect to the impedance Zd that drives the piezoelectric transformer and the load impedance ZL of the piezoelectric transformer, the reactance value Xc of Cs at the driving frequency of the piezoelectric transformer, that is, the resonant frequency of the piezoelectric transformer, should be set to a value of 1710 or less. A sufficient electrical connection can be made. [00701 This Example-2 does not use conductive fixing means, but by satisfying the above conditions, it is possible to obtain the same effect as the conductive fixing means. [0071] By the way, the drive frequency of the piezoelectric transformer is 3
When the values of MHz, Zd, and Zt are designed to be 50Ω, the value of Cs may be set to 104 PF. [0072]

As described above, according to the mounting method of the present invention, it is possible to reduce the decrease in Q when mounting a piezoelectric transformer. In particular, remarkable effects can be obtained when a piezoelectric single crystal is used as a piezoelectric substrate. [0073] As a result, a piezoelectric transformer with a large step-up ratio and high efficiency can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the basic principle of the present invention, (a) is a view of a piezoelectric transformer seen from one side, (b) is a view seen from the opposite side of (a), (C) (a) is a side view of (a), (d) is a diagram explaining the state in which the piezoelectric transformer is mounted,
It is.

FIG. 2 is a diagram for explaining Example-1, showing the configuration of a piezoelectric transformer. In addition, (a) is a diagram of the piezoelectric transformer seen from one side, (b) is a diagram of the piezoelectric transformer seen from the opposite side of (a), (
C) is a side view of (a), and (d) is a diagram illustrating the land shape.

FIG. 3 is a diagram for explaining Example-1, showing a mounting state of a piezoelectric transformer. In addition, (a) is a view seen from the side of the long side of the piezoelectric transformer, (b) is a view seen from the side of the short side of the piezoelectric transformer, and (C) is a view of the land on the printed circuit board side and the side view of the piezoelectric transformer side. FIG. 3 is a diagram illustrating the positional relationship with the land.

4A and 4B are diagrams for explaining Example-2, (a) is a diagram for explaining the soldering of Example-1 explained in FIG. 3, and (b) is a diagram for explaining Example-2. FIG. 3 is a diagram illustrating a case where the device is supported and fixed with an insulating adhesive.

FIG. 5 is a diagram illustrating a piezoelectric transformer, in which (a) is a perspective view of the piezoelectric transformer, and (b) is a view of (a) seen from the front side of the figure.

[Explanation of symbols]

1, la, 1b 2a, 2b, 2c, 2d, 2e, 2f3a,
3b, 3c, 3d, 3e, 3f7a, 7b
, 7c, 7d 7e, 7f, 7g, 7h a b C 12a, 12b 13a, 13b Piezoelectric board Input electrode Output electrode Island electrode Land solder Conductive paste Conductive adhesive Printed circuit board wiring member pattern Land Vibration node

[Figure 1]

[Figure 5]

Claims (3)

[Claims] Claim 1: A method of mounting a piezoelectric transformer that utilizes only transverse effect longitudinal vibration and operates in a half-wavelength resonance mode, leaving a gap (6) at a position where a vibration node (15) is to be formed. , input electrodes (2c, 2d) on both sides of the piezoelectric substrate (1a)
In the piezoelectric transformer in which output electrodes (3c, 3d) are formed, the gap (6) on one surface of the piezoelectric substrate (1a)
), one of the island electrodes (7b, 7d) is connected to the input electrode (2d) on the same surface, and the island electrode (7b, 7d) is connected to the input electrode (2d) on the same surface. The other one is connected to the output electrode (3d) on the same surface, and the other one is connected to the output electrode (3d) on the same surface, and
, 7d) is prepared, and a supporting/wiring member (9) having a wiring member (12) is provided at a position opposite to the piezoelectric transformer's island electrodes (7b, 7d) and the supporting/wiring member (9). A method for mounting a piezoelectric transformer, comprising: connecting a wiring member (12) with a conductive fixing means (8). 2. The piezoelectric transformer mounting method according to claim 1, further comprising: a gap (6) on the other surface of the piezoelectric substrate (1a);
Two island electrodes (7a, 7c) are formed on the same surface, one of the island electrodes (7a, 7c) is connected to the input electrode (2c) on the same surface, and the island electrode (7a, 7c) is connected to the input electrode (2c) on the same surface. A piezoelectric transformer mounting method characterized in that the other of the piezoelectric transformers is connected to an output electrode (3c) on the same surface, and a lead wire (10) is connected to the island-like electrodes (7a, 7c). 3. In the piezoelectric transformer mounting method according to claim 2, the location of the island electrodes (7b, 7d) formed on one surface of the piezoelectric substrate (1a) and the island formed on the other surface are determined. The placement positions of the shaped electrodes (7a, 7c) are set to the piezoelectric substrate (1).
A method for mounting a piezoelectric transformer, characterized in that: (a) the piezoelectric transformer is disposed at positions that do not face each other across the piezoelectric transformer.