JP2008235770A - Method of fixing piezoelectric transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of fixing a piezoelectric transformer not only preventing a failure in mounting the piezoelectric transformer by efficiently fixing a piezoelectric transformer of a piezoelectric inverter at a predetermined height from a circuit board but also sufficiently satisfying an opening output voltage standard for the piezoelectric inverter to control the opening output voltage by detecting the output voltage using the antenna electrode. <P>SOLUTION: Silicon resins as materials 4a, 4b for fixing the piezoelectric transformer 1 are coated on the circuit board 2. The silicon resins are dried to be hardened while the piezoelectric transformer 1 is maintained at the predetermined height from the circuit board 2, and then the piezoelectric transformer 1 is fixed at the predetermined height from the circuit board 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to component mounting of a piezoelectric inverter, and more particularly to a method for fixing a piezoelectric transformer to a circuit board on which circuit components for driving the piezoelectric transformer are mounted.

  In recent years, piezoelectric transformers using piezoelectric materials have been widely used in backlight inverters for liquid crystal displays because they have higher efficiency and higher step-up ratio and are suitable for lowering the height compared to electromagnetic transformers. Yes.

  The piezoelectric inverter is composed of a piezoelectric transformer, a drive circuit component, and a circuit board. Examples of drive circuit components include control ICs, FETs, transistors, diodes, resistors, capacitors, input / output connectors, and choke coils. These components can be surface mounted on a circuit board.

  As a component mounting method of the piezoelectric inverter, first, a surface mounting component other than the piezoelectric transformer is soldered in a reflow furnace, and then the piezoelectric transformer is manually fixed to the circuit board and soldered.

  Since the voltage is converted by the piezoelectric ceramic mechanical vibration, the piezoelectric transformer must be mounted so as not to interfere with the mechanical vibration by contacting the circuit board or the drive circuit component. In particular, for a piezoelectric transformer having a single plate structure, electrodes are provided on the front and back surfaces of substantially half of a rectangular piezoelectric transformer, and lead wires are soldered. In order to mount on a circuit board without hindering mechanical vibration, the piezoelectric transformer must be soldered to the circuit board by holding both ends of the piezoelectric transformer so as to be horizontal to the circuit board.

  Therefore, as a conventional method of mounting a piezoelectric transformer on a circuit board, there is a method disclosed in Patent Document 1. First, a silicone resin is applied to the mounting position of the piezoelectric transformer on the circuit board and dried and fixed to form a spacer. Next, a resin for fixing the piezoelectric transformer is applied to the circuit board, and the piezoelectric transformer is placed on the spacer and dried and fixed. Then, the lead wire soldered to the piezoelectric transformer is soldered to a predetermined electrode of the circuit board.

  5A and 5B are explanatory views showing a state in which a piezoelectric transformer is fixed to a circuit board according to a conventional method. FIG. 5A is a plan view and FIG. 5B is a side view. 1 is a piezoelectric transformer, 52 is a circuit board, 58a, 58b and 58c are spacers, and 59a and 59b are fixing members.

  A conventional method for fixing a piezoelectric transformer to a circuit board will be described in accordance with a procedure. Silicone resin is applied as a spacer resin to the circuit board 52 and dried and fixed to form spacers 58a, 58b, and 58c. Then, a silicone resin is applied as the fixing members 59a and 59b, and the piezoelectric transformer 1 is placed on the spacers 58a, 58b and 58c, and the silicone resin is dried and fixed, and the piezoelectric transformer 1 is fixed to the circuit board 52. It was.

JP 11-354854 A

  However, in the conventional method of fixing the piezoelectric transformer to the circuit board disclosed in Patent Document 1, the height of the piezoelectric transformer 1 from the circuit board 52 is secured by the spacers 58a, 58b, and 58c in FIG. However, when the spacer resin is dried and fixed, the height of the spacer is about 0.3 to 0.4 mm. Further, since the lead wire soldered to the electrode of the piezoelectric transformer having a single plate structure has a diameter of 0.5 mm, the piezoelectric transformer is fixed without being horizontal with the circuit board.

  Also, in the step of mounting the piezoelectric transformer after applying silicone resin as a fixing member to the circuit board, the operator mounts the piezoelectric transformer by looking at the mounting position of the piezoelectric transformer and the position of the spacer shown on the circuit board. It was. However, since there is no stopper for fixing the piezoelectric transformer, the piezoelectric transformer is displaced, and in the worst case, the lead wire of the piezoelectric transformer cannot be soldered to the circuit board, resulting in poor mounting. It was.

  Furthermore, because of the formation of the spacer, it takes 30 minutes to dry the spacer resin at room temperature, and then it takes another 30 minutes to dry and fix the piezoelectric transformer in the same manner, which is very inefficient. It was.

  By the way, as a required characteristic for a piezoelectric inverter, when an input voltage is applied to the piezoelectric inverter in a no-load state, the circuit must be cut off without causing a failure due to heat generation, and the output voltage must be set to zero. The drive circuit is designed to satisfy this condition.

  As a standard for this required characteristic, there is an open output voltage. This is the maximum voltage until the output voltage is cut off when the input voltage is applied to the piezoelectric inverter in a no-load state.

  The control circuit for cutting off the output voltage divides the output voltage with a resistor, and cuts off the output voltage when the voltage applied to the detection resistor exceeds a certain voltage. About six expensive high voltage resistances are required for the detection resistor. However, demands for miniaturization and cost reduction have increased, and control circuits that do not use detection resistors have been studied.

  A method of controlling the open output voltage without using a detection resistor is a method in which an antenna electrode is provided in the vicinity of the output voltage terminal, the leakage voltage is measured, and the output voltage is cut off. Since the detection resistor is not used, the cost can be reduced, the area of the drive circuit board can be reduced, and an inexpensive and small piezoelectric inverter can be provided.

  However, if a method of measuring leakage voltage, cutting off the output voltage and controlling the open output voltage is applied to a conventional piezoelectric inverter by a method of fixing the piezoelectric transformer to the circuit board, there is a problem that the standard of the open output voltage cannot be satisfied. there were. This is because the piezoelectric transformer is as low as 0.3 to 0.4 mm in height from the circuit board, so that the measured value of the leakage voltage is not accurate and the open output voltage cannot be controlled.

  Therefore, according to the present invention, in the manufacture of a piezoelectric inverter, the piezoelectric transformer is efficiently fixed at a predetermined height from the circuit board to prevent the mounting failure of the piezoelectric transformer, and the output voltage is detected using the antenna electrode. Another object of the present invention is to provide a piezoelectric transformer fixing method that can sufficiently satisfy the open output voltage standard for a piezoelectric inverter that controls the open output voltage.

  The present invention has been made as a result of studying a method of fixing a piezoelectric transformer to a circuit board in order to solve the above problems.

  That is, in a method of fixing the piezoelectric transformer to a circuit board on which circuit components for driving the piezoelectric transformer are mounted via a jig having a plurality of pins, a plurality of through holes provided in the circuit board are provided. After being inserted into the plurality of pins provided with steps and applying a fixing resin to the circuit board, the piezoelectric transformer is placed on the plurality of pins and held at a predetermined height from the circuit board. A method of fixing a piezoelectric transformer, comprising fixing the piezoelectric transformer to the circuit board by drying and fixing the fixing resin.

  The piezoelectric transformer fixing method according to the above, wherein a height of the piezoelectric transformer from the circuit board is 0.9 mm or more.

  As described above, according to the method for fixing a piezoelectric transformer to a circuit board according to the present invention, a piezoelectric transformer having a single plate structure can be efficiently fixed to a predetermined height in parallel with the circuit board. This prevents the occurrence of mounting defects due to contact with the drive circuit components or the displacement of the piezoelectric transformer, and is useful for manufacturing a piezoelectric inverter.

  In addition, by fixing the piezoelectric transformer at a predetermined height from the circuit board, it is sufficient to use a method for measuring and controlling the output voltage using the antenna electrode in the circuit for controlling the open output voltage of the piezoelectric inverter. Since the open output voltage standard can be satisfied, it is useful for manufacturing an inexpensive and small piezoelectric inverter.

  Next, an embodiment of a method for fixing a piezoelectric transformer to a circuit board according to the present invention will be described with a specific example.

  FIG. 1 is an explanatory view showing a state in which a piezoelectric transformer is fixed to a circuit board according to the present invention. 1A is a plan view, and FIG. 1B is a side view. The piezoelectric transformer 1 is fixed to a predetermined height on the circuit board 2 by fixing members 4a and 4b. The three through holes 3a, 3b, and 3c of the circuit board 2 are through holes for inserting pins of a fixing jig for holding and fixing the piezoelectric transformer at a predetermined height.

  FIG. 2 is an explanatory view showing a fixing jig of the piezoelectric transformer of the present invention. FIG. 2A is a plan view of the pressing jig, and FIG. 2B is a side view of the pressing jig. FIG. 2C is a plan view of the fixing jig, and FIG. 2D is a side view of the fixing jig.

  2 (c) and 2 (d), the fixing jig 5a has fixing pins 6a, 6b, 6c and holding pins 7a, 7b, 7c. Each pin is provided in accordance with the position of the through holes 3a, 3b, 3c provided in the circuit board 2 shown in FIG.

  2A and 2B, the pressing jig 5b has fixing grooves 8a, 8b, and 8c, and is provided at positions corresponding to the fixing pins 6a, 6b, and 6c, respectively. Here, it is desirable that a sheet 5c made of a flexible urethane sponge or the like is attached to the surface of the pressing jig 5b that contacts the piezoelectric transformer. This is to protect the surface of the piezoelectric transformer and to absorb thickness variations due to the lead wires soldered to the electrodes of the piezoelectric transformer.

  Further, when the piezoelectric transformer is fixed by the holding jig 5b, the variation in the height of the piezoelectric transformer from the circuit board due to the variation in the application amount of the fixing member is absorbed, and the variation in the height of the piezoelectric transformer from the circuit board is absorbed. Can be small.

  FIG. 3 is an explanatory view showing a state in which the piezoelectric transformer is held on the circuit board by a fixing jig. 3A is a plan view of a state in which the circuit board is placed on the fixing jig and the piezoelectric transformer is held. FIG. 3B is a plan view of the circuit board that is placed on the fixing jig and the piezoelectric transformer is held. It is a side view of the state put on and hold | maintained with the pressing jig.

  Hereinafter, a method for fixing a piezoelectric transformer to a circuit board according to the present invention will be described with reference to FIG. 3A, the through hole 3a of the circuit board 2 is fixed to the fixing pin 6a and the holding pin 7a, the through hole 3b is fixed to the fixing pin 6b, the holding pin 7b, and the through hole 3c is fixed to the fixing pin. The circuit board 2 is placed on the fixing jig 5a through the holding pin 7c.

  Next, a silicone resin is applied to the circuit board 2 as the fixing members 4a and 4b using a dispenser or the like. Then, the piezoelectric transformer 1 is placed on the holding pins 7a, 7b, and 7c. Here, the fixing pins 6a, 6b, and 6c serve as stoppers by abutting the piezoelectric transformer 1, and also play a role of preventing displacement.

  3B, the fixing grooves 8a, 8b and 8c of the pressing jig 5b are placed on the piezoelectric transformer 1 together with the fixing pins 6a, 6b and 6c, and are used as fixing members 4a and 4b. The applied silicone resin is dried and fixed.

  Then, the holding jig 5b is removed, the circuit board 2 is removed from the fixing jig 5a, and the fixing of the piezoelectric transformer 1 to the circuit board 2 is completed. Then, the lead wire (not shown) is soldered to a predetermined electrode of the circuit board, and the mounting of the piezoelectric transformer is completed.

  In FIG. 3, a jig for supporting and fixing a piezoelectric transformer using two pins having different lengths is used. However, for example, a step may be provided on one pin to hold and fix the piezoelectric transformer. .

  Next, a specific example is given and the method for fixing the piezoelectric transformer to the circuit board according to the present invention will be described in more detail.

  The height of the holding pins 7a, 7b, 7c of the fixing jig 5a shown in FIGS. 2 (c) and 2 (d) from the board installation surface is 0.8 mm from the circuit board of the piezoelectric transformer. The height was set to 0.9 mm and 1.7 mm. Here, the height of the piezoelectric transformer from the circuit board is 0.1 mm for soldering and 0 for resin because the lead wire connected to the piezoelectric transformer is φ0.5 mm and is fixed by soldering resin. .3mm was added to a height of 0.9mm.

  The height of the fixing pins 6a, 6b, 6c of the fixing jig 5a from the board installation surface is 1.7 mm of the above-mentioned holding pins, 2 mm of the thickness of the piezoelectric transformer, and soldered to the upper surface. The height of the lead wire is 0.9 mm and the depth of the fixing groove of the holding jig is 1 mm, so that the total is 5.6 mm. The outer diameter of both the holding pin and the fixing pin was φ1.0 mm.

  The through holes 3a, 3b, and 3c of the circuit board 2 shown in FIG. The fixing pin 6a and the holding pin 7a shown in the fixing jig 5a in FIGS. 2 (c) and 2 (d) are passed through the through hole 3a of the circuit board 2, and similarly fixed to the through hole 3b. The circuit board 2 was placed on the fixing jig 5a through the pin 6b and the holding pin 7b, and similarly through the fixing hole 6c and the holding pin 7c through the through hole 3c.

  Then, as shown in FIG. 3A, a silicone resin is applied as a fixing member 4a, 4b to the circuit board 2 by a dispenser, and the piezoelectric transformer is immediately placed on the holding pins 7a, 7b, 7c. Next, as shown in FIG. 3B, the fixing grooves 8a, 8b and 8c of the holding jig 5b are placed on the piezoelectric transformer 1 so as to be aligned with the fixing pins 6a, 6b and 6c, respectively. The silicone resin was dried and fixed at room temperature for 30 minutes.

  After the fixing members 4a and 4b are dried and fixed, the piezoelectric transformer 1 is fixed to the circuit board 2 by removing the pressing jig 5b. Therefore, the circuit board 2 to which the piezoelectric transformer 1 is fixed is removed from the fixing jig 5a, and lead wires (not shown) of the piezoelectric transformer 1 are soldered (not shown) to predetermined electrodes of the circuit board 2, A piezoelectric inverter was fabricated. The manufactured piezoelectric inverter has a circuit configuration in which an output voltage is measured using an antenna electrode to control an open output voltage.

  For comparison, a piezoelectric inverter of the same specification was manufactured by fixing it to a circuit board by a conventional method of fixing a piezoelectric transformer. First, a spacer resin was applied to a circuit board 52 as shown in FIG. 5 with a dispenser, and fixed and dried at room temperature for 30 minutes to form spacers 58a, 58b, and 58c.

  Next, a silicone resin was applied as the fixing members 59a and 59b, the piezoelectric transformer 1 was placed on the spacers 58a, 58b, and 58c, and the silicone resin was dried and fixed at room temperature for 30 minutes. Then, a lead wire (not shown) of the piezoelectric transformer 1 was soldered (not shown) to a predetermined electrode of the circuit board 2 to produce a piezoelectric inverter.

  FIG. 4 is a frequency distribution graph of the open output voltage of the piezoelectric inverter. FIG. 4A is a frequency distribution graph of the open output voltage of the piezoelectric inverter by the method of fixing the piezoelectric transformer to the circuit board according to the present invention, and FIG. 4B is the piezoelectric by the method of fixing the conventional piezoelectric transformer to the circuit board. It is a frequency distribution graph of the open circuit output voltage of an inverter, and each is 50 measurement data. The standard of the open output voltage of this piezoelectric inverter was 1700 Vrms or more.

  In the piezoelectric inverter according to the conventional mounting method, the average value of the open output voltage is 1749 Vrms, and there are six below 1700 V. σ was 75.

  In the piezoelectric inverter of the piezoelectric transformer mounting method according to the present invention, the average value of the open output voltage was 1797 Vrms and was not less than 1700 V. σ was 56.

  With the method of mounting a piezoelectric transformer according to the present invention, the measured value of the open output voltage is increased by about 50 Vrms on average, the variation is reduced, and there is no defective open output voltage.

Explanatory drawing which shows the state which fixed the piezoelectric transformer to the circuit board by this invention. FIG. 1A is a plan view. FIG. 1B is a side view. Explanatory drawing which shows the fixing jig of the piezoelectric transformer of this invention. FIG. 2A is a plan view of the holding jig. FIG. 2B is a side view of the holding jig. FIG. 2C is a plan view of the fixing jig. FIG. 2D is a side view of the fixing jig. Explanatory drawing which shows the state holding the piezoelectric transformer on the circuit board with the fixing jig. FIG. 3A is a plan view of a state where a circuit board is placed on a fixing jig and a piezoelectric transformer is held. FIG. 3B is a side view of a state in which the circuit board is placed on the fixing jig, the piezoelectric transformer is placed on the holding pins, and held by the holding jig. The frequency distribution graph of the open output voltage of a piezoelectric inverter. FIG. 4A is a frequency distribution graph of the open output voltage of the piezoelectric inverter by the method of fixing the piezoelectric transformer to the circuit board according to the present invention. FIG. 4B is a frequency distribution graph of the open output voltage of the piezoelectric inverter by the conventional method of fixing the piezoelectric transformer to the circuit board. Explanatory drawing which shows the state which fixed the piezoelectric transformer to the circuit board by the conventional method. FIG. 5A is a plan view. FIG. 5B is a side view.

Explanation of symbols

1 Piezoelectric transformer 2, 52 Circuit board
3a, 3b, 3c Through hole 4a, 4b, 59a, 59b Fixing member 5a Fixing jig 5b Holding jig 5c Sheet 6a, 6b, 6c Fixing pin 7a, 7b, 7c Holding pin 8a, 8b, 8c Fixing Groove 58a, 58b, 58c Spacer

Claims (2)

  In a method of fixing the piezoelectric transformer to a circuit board on which a circuit component for driving the piezoelectric transformer is mounted via a jig having a plurality of pins, a plurality of through holes provided in the circuit board are provided with steps. After being inserted into the plurality of pins provided and applying a fixing resin to the circuit board, the piezoelectric transformer is placed on the plurality of pins and held at a predetermined height from the circuit board to fix the circuit board. A method for fixing a piezoelectric transformer, comprising fixing a piezoelectric transformer to the circuit board by drying and fixing a resin for use.   2. The method of fixing a piezoelectric transformer according to claim 1, wherein a height of the piezoelectric transformer from the circuit board is 0.9 mm or more.

Images