JP4060895B2 - Piezoelectric diaphragm - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric diaphragm used as a sounding body of a handset of a mobile phone.
[0002]
[Prior art]
Conventionally, a general structure of a piezoelectric diaphragm is obtained by bonding a thin piezoelectric ceramic plate slightly smaller than the metal plate to a thin metal plate. In the piezoelectric ceramic plate, silver electrodes as power feeding means are uniformly provided on one surface in advance on the front and back surfaces. The lead wires are soldered to the surface electrodes of the metal plate and the piezoelectric ceramic plate, respectively. Moreover, as what uses a nonmetallic board | substrate instead of the said metal plate, there exist some which are disclosed by Unexamined-Japanese-Patent No. 2-214300 etc. In this piezoelectric diaphragm, a metal foil is bonded to a polymer film material larger than the piezoelectric ceramic plate, and a piezoelectric ceramic plate slightly smaller than the metal foil is attached to the metal foil side. A lead wire is soldered to the electrode on the surface of the piezoelectric ceramic plate and the surface of the metal foil.
[0003]
[Problems to be solved by the invention]
2. Description of the Related Art In recent years, piezoelectric diaphragms used in mobile phone receivers have been used in extremely small and thin piezoelectric ceramic plates and metal substrates in response to demands for miniaturization and thinning. When soldering to such an extremely thin object, cracks occur in the piezoelectric ceramic due to thermal strain and stress when the solder solidifies unless the soldering operation is strictly managed because the heat capacity is small. There was a risk of deterioration of insulation resistance or loss of reliability. Further, when the solder is solidified, the piezoelectric ceramic plate or the like is locally deformed, causing a problem that the tensile strength of the lead wire is lowered.
[0004]
The piezoelectric diaphragm is increasingly required to be thin. However, in the case of the conventional technology, the thickness of the lead wire and the solder is added on the piezoelectric ceramic plate, so that there is a limit to the thinning. In addition, in order to keep the thickness to a certain level, the soldering operation must be precisely controlled, and the soldering operation cannot be automated.
[0005]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a piezoelectric diaphragm that has good productivity and can be easily reduced in size and thickness.
[0006]
[Means for Solving the Problems]
According to the present invention, an electrode pattern made of a metal foil is formed on the surface of a flexible substrate such as a resin film, and a piezoelectric ceramic plate having electrodes formed on both sides is adhered to the electrode pattern of the metal foil with an adhesive, A pair of lead wire attachment portions to which external lead wires are connected are provided on the flexible substrate at a portion away from the plate, and the metal foil of the electrode pattern extends laterally from the piezoelectric ceramic plate and the lead wire One of the mounting portions is formed, the other of the lead wire mounting portions is formed of the metal foil separately from the electrode pattern, and the electrode on the upper surface of the piezoelectric ceramic plate is electrically connected to the other lead wire mounting portion. Piezoelectric diaphragms connected via a jumper wire made of paste. The adhesive may be an ultraviolet curable adhesive .
[0007]
According to the piezoelectric diaphragm of the present invention, since the lead wire is soldered at the lead wire mounting portion located away from the piezoelectric ceramic plate, the heat of the solder is not easily transmitted to the piezoelectric ceramic plate.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a piezoelectric diaphragm 10 of this embodiment. The flexible substrate 12 is a circular sheet formed of a synthetic resin film such as polyethylene, polyester, polyimide, vinyl chloride, PET, or PBT.
[0009]
An electrode pattern 14 made of copper foil is provided on the surface of the flexible substrate 12. The electrode pattern 14 is formed by etching a copper foil into a predetermined pattern from a sheet in which the copper foil is uniformly formed on a synthetic resin film to be the flexible substrate 12. The shape of the electrode pattern 14 is formed in a circular shape slightly smaller than the flexible substrate 12 at the center of the flexible substrate 12, and one lead wire extending from a part on the circumference of the circular shape to the edge of the flexible substrate 12. A mounting portion 14a is provided. Further, in the vicinity of the lead wire attachment portion 14a, the other lead formed on the edge portion of the flexible substrate 12 is separated from the electrode pattern 14 and the lead wire attachment portion 14a and insulated, and has the same width as the lead wire attachment portion 14a. The wire attaching part 14b is similarly provided with copper foil.
[0010]
On the circular electrode pattern 14 in the center of the flexible substrate 12, a thin and thin piezoelectric ceramic plate 16 slightly smaller than the circular electrode pattern 14 is bonded with an anaerobic ultraviolet curable adhesive 18. Note that electrodes 19 are formed on both surfaces of the piezoelectric ceramic plate 16 in which a conductive paste made of silver or the like is uniformly applied to one surface in advance.
[0011]
On the surface of the lead wire attachment portion 14b, a jumper wire 20 that connects the lead wire attachment portion 14b and the vicinity of the edge portion of the electrode 19 on the surface side of the piezoelectric ceramic plate 16 is printed with a conductive paste. An insulating coating agent 22 is printed in advance on the surface of the electrode pattern 14 below the jumper wire 20. One end of each lead wire 24 is soldered to the lead wire attaching portion 14a and the lead wire attaching portion 14b with solder 25, respectively.
[0012]
As shown in FIG. 3, the piezoelectric diaphragm 10 according to this embodiment is used by placing the piezoelectric diaphragm 10 in a resin case 26 and locking the peripheral portion of the flexible substrate 12 to a step portion 26 a on the inner wall of the resin case 26. . And the cover part 27 is covered, and the peripheral part of the flexible 12 is clamped and fixed by the step part 26a. Thereafter, it is attached to a predetermined receiver or the like, and a signal voltage is applied to the lead wire 24 to oscillate.
[0013]
In the piezoelectric diaphragm 10 of this embodiment, the lead wire 24 can be soldered by the pair of lead wire mounting portions 14a and 14b separated from the piezoelectric ceramic plate 16, and the piezoelectric ceramic plate 16 is affected by the solder heat. Therefore, defects due to heat can be avoided. This improves the product yield and makes it possible to automate the soldering operation. Further, the thickness of the piezoelectric ceramic plate 16 is not added to the thickness of the solder and the lead wire 24, which contributes to a reduction in thickness. Furthermore, the management for thinning the solder during the soldering work is not necessary, and from this point, the soldering work can be automated, which contributes to the reduction of man-hours.
[0014]
Further, when a resin film such as PET or PBT is used for the flexible substrate 12, it can be bonded to a resin case made of PET, PBT or the like by ultrasonic welding, and the number of processes and time can be reduced.
[0015]
The piezoelectric diaphragm of the present invention is not limited to the above embodiment. For example, the electrode pattern 14 may be formed by means other than etching, and is formed by directly printing a conductive paste of silver or the like on the surface of the flexible substrate 12 and directly stacking a piezoelectric ceramic plate thereon. Alternatively, the lead wire attachment portion may be printed by a conductive paste. Furthermore, the shape and position of each member and the material can be changed as appropriate.
[0016]
【The invention's effect】
The piezoelectric diaphragm of the present invention eliminates soldering on the surface of the piezoelectric ceramic plate, does not cause defects due to the heat of the solder, can be made very thin, and is manufactured by a simple manufacturing process. Can do.
[Brief description of the drawings]
FIG. 1 is a front view of a piezoelectric diaphragm according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a cross-sectional view showing a usage state of the piezoelectric diaphragm of the first embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Piezoelectric diaphragm 12 Flexible board 14 Electrode pattern 14a, 14b Lead wire attaching part 16 Piezoelectric ceramic board 19 Electrode 20 Jumper wire

Claims (2)

An electrode pattern made of a metal foil is formed on the surface of the flexible substrate, and a piezoelectric ceramic plate having electrodes formed on both sides is adhered to the electrode pattern of the metal foil by an adhesive, and the flexible portion in a portion away from the piezoelectric ceramic plate A pair of lead wire attachment portions to which external lead wires are connected are provided on the substrate, and the metal foil of the electrode pattern extends sideways from the piezoelectric ceramic plate to form one of the lead wire attachment portions, The other of the lead wire mounting portions is formed of the metal foil separated from the electrode pattern, and the electrode on the upper surface of the piezoelectric ceramic plate is connected to the other lead wire mounting portion via a jumper wire made of conductive paste. the piezoelectric vibration plate that is. The piezoelectric diaphragm according to claim 1, wherein the adhesive is an ultraviolet curable adhesive .

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