CN101614520A - Piezoelectric sensor and method for detecting static displacement - Google Patents

Abstract

The present invention relates to the piezoelectric sensor field, specifically refer to a kind of piezoelectric sensor and method thereof that detects static displacement.Detect the piezoelectric sensor of static displacement, comprise organic film, two sides at organic film are provided with piezoelectric ceramic piece, pcb board to be measured is sticked on the piezoelectric ceramic piece, utilize the inverse piezoelectric effect of piezoelectric ceramic piece, produce driving force, make the piezoelectric ceramic piece electric signal output certain of the other side of organic film owing to piezoelectric effect produces, apply a lasting external force to pcb board simultaneously, when pcb board has miniature deformation, can produce different electric signal output, can be detected by oscillograph.Piezoelectric sensor of the present invention is simple and reliable for structure, and is with low cost, and detection method is simple and practical, can apply in the commercial production widely.

Description

Piezoelectric sensor and method for detecting static displacement

【Technical field】

The invention relates to the field of piezoelectric sensors, in particular to a piezoelectric sensor for detecting static displacement and a method thereof.

【Background technique】

At present, the development of electronic technology is quite rapid, and PCB boards carrying electronic components are widely used in various electronic products due to their many advantages. In order to improve the reliability of the PCB board, it is often necessary to perform a pressure test on the PCB board, and the PCB will be deformed and bent. However, it is not possible to determine how much pressure the PCB will be subjected to. The device is used to detect the deformation of the PCB and adjust the pressure applied during the test to prevent damage to the PCB board, so that the PCB board can be designed to meet the external pressure range to enhance reliability; in addition, the PCB board will be deformed if the external force is too large. It may cause potential failure of the connection of electronic components at the solder joints. However, how much deformation of the PCB board will cause reduced reliability is difficult to distinguish based on experience alone.

【Content of invention】

The technical problem to be solved by the present invention is to quickly detect the degree of deformation of the PCB board and the pressure it can withstand, and provide a piezoelectric sensor for detecting static displacement and a method thereof.

A piezoelectric sensor for detecting static displacement of the present invention comprises an organic thin film, piezoelectric ceramic sheets are respectively arranged on both sides of the organic thin film, and lead wires for input and output signals are connected to the piezoelectric ceramic sheets.

Preferably, the piezoelectric ceramic sheet is provided with an electrode sheet, which is electrically connected to the wire.

A pair of strip-shaped electrode sheets are arranged between the organic thin film and the piezoelectric ceramic sheet, and the electrode sheets are symmetrically arranged on both sides of the piezoelectric ceramic sheet facing the organic thin film, and are connected to wires through silver glue.

A kind of method for detecting static displacement of the present invention, its steps are as follows:

Provide a PCB board to be tested;

Paste the PCB board to the test surface of the piezoelectric sensor;

Apply a continuous external force to the PCB;

Input a sinusoidal signal of a certain frequency through the signal input wire of the piezoelectric sensor;

Connect the signal output wire of the piezoelectric sensor to the oscilloscope, and capture the output signal through the oscilloscope to display the waveform to obtain the bending degree of the PCB board.

The piezoelectric sensor for detecting static displacement of the present invention is provided with piezoelectric ceramic sheets on both sides of the organic film, and the PCB board to be tested is pasted on a piezoelectric ceramic sheet, and the inverse piezoelectric effect of the piezoelectric ceramic sheet is used to generate The driving force makes the piezoelectric ceramic sheet on the other side of the organic film produce a certain electrical signal output due to the piezoelectric effect, and at the same time applies a continuous external force to the PCB board. When the PCB board is slightly deformed, different electrical signal outputs will be generated. , can be detected by an oscilloscope. The piezoelectric sensor of the invention has simple and reliable structure, low cost, simple and practical detection method, and can be widely used in industrial production.

【Description of drawings】

Fig. 1 is the three-dimensional schematic diagram of piezoelectric sensor of the present invention;

Fig. 2 is the sectional structure schematic diagram of piezoelectric sensor of the present invention;

Fig. 3 is a cross-sectional view of the exploded structure of the piezoelectric sensor of the present invention.

【Detailed ways】

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, it is a piezoelectric sensor 100 for detecting static displacement according to the first embodiment of the present invention. There is a piezoelectric ceramic sheet 300 , and a lead 500 for input and output signals is connected to the piezoelectric ceramic sheet 300 through silver glue 510 .

As shown in FIG. 2 , it is a schematic cross-sectional structure diagram of the piezoelectric sensor of the present invention. The two sides of the organic film 200 are respectively provided with piezoelectric ceramic sheets 400a, 400b, and the two sides of the organic film 200 are respectively provided with symmetrically distributed electrode sheets 400a, 400b, and some of the electrode sheets 400a, 400b are pressed by corresponding The electric ceramic sheets 300a, 300b are covered and pasted on the organic film 200; the exposed ends of the electrode sheets 400a, 400b are connected with wires 500a, 500b for input and output signals, which are connected by dotting silver glue 510a, 510b respectively. As shown in Figure 3 again, the electrode sheets 400a, 400b are a pair and are strip-shaped, and the electrode sheets 400a, 400b are symmetrically connected to the two sides of the piezoelectric ceramic sheet 400a, 400b to the side of the organic film, so that the performance of the piezoelectric sensor of the present invention Stable and reliable, uniform driving force, the electrode sheets 400a, 400b are connected to the wires 500a, 500b through silver glue 510a, 510b. During use, the PCB board 600 to be tested is pasted on the test surface of the piezoelectric ceramic sheet 300b of the piezoelectric sensor 100 by glue, and then a continuous external force is applied to the PCB board. The most convenient way is to place a weight of a certain quality on a horizontal On the surface of the PCB board 600, gravity is applied to the PCB board 600. Of course, a more precise instrument can also be used to apply a continuous external force to the PCB board; and then a sinusoidal signal of a certain frequency is input to one of the piezoelectric ceramic sheets 300b through the signal input wire 500 , due to the deformation of the PCB board 600 by the gravity of the weight, the piezoelectric ceramic sheet 300b generates a driving force due to the inverse piezoelectric effect, that is to say, an electric field with the same polarization direction is given to the piezoelectric ceramic sheet 300b, because the direction of the electric field is the same as The direction of the polarization is the same, so the action of the electric field increases the polarization. At this time, the distance between the positive and negative bound charges in the piezoelectric ceramic sheet 300b attached to the PCB board 600 also increases, and the piezoelectric ceramic sheet 300b produces elongation deformation along the polarization direction. The piezoelectric ceramic sheet 300a on one side is closely pasted together, and a certain degree of deformation of the piezoelectric ceramic sheet 300b will force the piezoelectric ceramic sheet 300a to deform, and the positive piezoelectric effect of the piezoelectric ceramic sheet 300a will be used to generate a certain electrical signal output That is to say, since the piezoelectric ceramic sheet 300a is forced to bend and apply a pressure parallel to the polarization direction, the piezoelectric ceramic sheet 300a will undergo compression deformation, and the distance between the positive and negative bound charges in the sheet will become smaller, The polarization intensity also becomes smaller. Therefore, part of the free charge originally adsorbed on the electrode is released and a discharge phenomenon occurs; since the charge generated by the external force acting on the piezoelectric element can only be preserved under the condition of no leakage, a sinusoidal signal of a certain frequency is introduced. Affected by the released charge, the signal will change when it is output. When an electrical signal different from the input signal is output to the oscilloscope, the output signal can be captured by the oscilloscope to display the waveform. The degree of bending of the PCB board 600 can be obtained, which can withstand What a stress. Of course, in this process, the applied external force may not be enough to deform the PCB board, and since the piezoelectric ceramic sheet 300a will not be deformed by the external force, the input and output sinusoidal signals are basically the same, and the PCB at this moment is obtained. The board 600 will not be deformed, and the external force applied to the PCB board can be gradually increased in the next moment, so as to test the pressure that the PCB board 600 can bear, meet the test requirements, and be used in the production process.

What has been described above is only a preferred embodiment of the present invention. It should be pointed out that, for those of ordinary skill in the art, improvements can be made without departing from the inventive concept of the present invention, but these all belong to protection scope of the present invention.

Claims (4)

1. A piezoelectric sensor for detecting static displacement, comprising an organic film, characterized in that: the two sides of the organic film are respectively provided with piezoelectric ceramic sheets, and the piezoelectric ceramic sheets are connected with wires for input and output signals. 2. The piezoelectric sensor for detecting static displacement according to claim 1, characterized in that: said piezoelectric ceramic sheet is provided with an electrode sheet, which is electrically connected to said wire. 3. The piezoelectric sensor for detecting static displacement according to claim 1, characterized in that: a pair of strip-shaped electrode sheets are arranged between the organic film and the piezoelectric ceramic sheet, and the electrode sheets are symmetrically arranged on the piezoelectric ceramic sheet. The sheets face to both sides of the side of the organic film, and are connected with wires through silver glue. 4. A method for detecting static displacement, characterized in that: comprising the following steps: Provide a PCB board to be tested; Paste the PCB board to the test surface of the piezoelectric sensor; Apply a continuous external force to the PCB; Input a sinusoidal signal of a certain frequency through the signal input wire of the piezoelectric sensor; Connect the signal output wire of the piezoelectric sensor to the oscilloscope, and capture the output signal through the oscilloscope to display the waveform to obtain the bending degree of the PCB board.

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