JPH03212994A - Circuit device - Google Patents

Abstract

PURPOSE:To eliminate that air bubbles are generated by a method wherein a potting agent is injected into a circuit board having a through hole of a round shape, a square shape or the like in the rear surface to which a hermetically sealed transformer is attached and the air existing between an edge of a case and a casting agent is discharged. CONSTITUTION:Mounting holes 12 through which metal pin terminals 6 of a hermetically sealed transformer are passed so as to be solder-connected are formed in a circuit board 10. A through hole 19 of a round shape, a square shape, an oval shape, a triangular shape or the like is formed in the central part. A space part (a) exists and the air 18 exists between an edge 1a of a case 1 of the transformer and a casting agent 9 injected into the transformer. A potting agent 16 of a prescribed volume is injected into a tray 14, for casting use, which is composed of a rubber-like mold. The substrate 10 is placed on the surface and is pushed downward. Then, the potting agent 16 is passed through the hole 19, hits the casting agent 9, is passed through a gap 1b existing between the edge 1a of the case 1 and a contact face with the substrate and flows out to the surface of the substrate 10. Thereby, since the air 18 existing between the edge 1a and the casting agent 9 is discharged to the outside from the gap 1b, the potting agent 16 creeps completely between the edge 1a and the casting agent 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a circuit device in which a sealed transformer used in various audio equipment, video equipment, industrial equipment, etc. is attached to a circuit board together with various electronic components.

BACKGROUND OF THE INVENTION First, a sealed transformer will be explained. Figure 4 is a perspective view of the completed sealed transformer, Figure 5 is a perspective view of the assembly structure of the sealed transformer, and Figure 6 is a side sectional view of the completed sealed transformer. . The structure of the sealed transformer will be explained with reference to FIG. 5. The bottom flange 3 is attached to the upper and lower ends of the bopin cylindrical part 4 made of plastic. A lower end collar 2 is provided, and a metal pin terminal 6 is incorporated into the lower end collar 2. A coil 5 is formed by winding a steel wire around the bopin having such a structure. Furthermore, the lead wire 8 is wound and connected to the base of the metal pin terminal 6, and connected to the metal pin terminal 6 using a solder dip or the like. Then, the magnetic material 7 is assembled to complete the transformer main body, and the transformer body is inserted and assembled into the cylindrical plastic case 1 with the negative side open. And for the next casting process, please refer to the 6th section.
This will be explained using the side sectional view shown in the figure. After inserting the transformer main body into a case 1 made of plastic, a fluid casting resin 9 such as silicone, epoxy, urethane, etc. is poured into the mold, and further hardened by heating or the like to complete a sealed transformer. The amount of casting resin 9 is such that a space of size a is created inside the end surface 1a of the case 1. Injecting the casting resin 9 to the same dimensions as the end surface 1a of the case 1 may cause variations in the injection amount due to variations in the accuracy of the injection equipment, or the casting resin 9 may penetrate into the coil due to the decrease in viscosity during heating and curing, causing the liquid level to drop. This is technically impossible due to factors such as lowering the temperature. Moreover, if too much casting resin 9 is poured into the mold, it will spill out from the end face 1a of the case 1, staining the surface of the case 1, or adhere to the metal pin terminals 6, making it impossible to solder them to the circuit board. Therefore, the amount of casting resin 9 is such that a space is created inside the end surface 1a of the case 1 by the dimension a.

The above-mentioned sealed transformer mounted on a conventional circuit board will be explained using FIG. 3. The circuit board 10 is provided with holes 12 for mounting the sealed transformer. A metal pin terminal 6 is inserted through the terminal, and its protrusion 6a is connected with solder 13. After that, the purpose is to block water, moisture, dust, flakes, gas, etc. that may affect the circuit conduction parts of the sealed transformer and electronic components 15 and cause short circuits, disconnections, corrosion, etc. A fluid potting agent 16 is poured into the mold. In the casting method, a specified amount of potting agent 16 is poured into a casting tray 14 in advance, and then the circuit board 10 on which the sealed transformer, electronic components 15, etc. are attached is pressed down from the upper direction Y. The hermetic transformer or other electronic component 15 is immersed in a flow such that the potting agent 16a at the bottom of the circuit board 10 flows around to the top. After that, heating is performed to harden the potting agent 16,
Complete the circuit device.

Problems to be Solved by the Invention This type of sealed transformer is generally used in a wide variety of ways. For example, vacuum cleaners, irons, washing machines,
It is used in all kinds of electronic equipment such as jar pots, water heaters, lighting equipment, and television receivers. Among them, lighting equipment used outdoors, washing machines that handle water, etc. are waterproof,
In reality, electronic components were mounted on circuits for the purpose of moisture-proofing, dust-proofing, and blocking toxic gases, and then potting them with casting resin such as urethane or epoxy to cut off the outside air and the electronic circuits. However, when a sealed transformer is installed and the casting agent is potted and heated to harden, the air inside the sealed transformer expands, penetrating the liquid of the casting agent and forming defects called bubbles on the surface. occurs.

To explain this mechanism using FIG. 3, the casting method starts by pouring a specified amount of potting agent 16 into a rubber-like mold called a casting tray 14, and then using a closed type transformer.
The circuit board 10 with the electronic components 15 etc. attached is placed on the surface of the cast potting agent 16, and further towards the bottom,
Press down from the top direction Y. Then the circuit board 10
The lower part of the potting agent 16a passes through the gap B between the casting tray 14 and the circuit board 10, goes around to the upper part, and pots the sealed transformer or electronic component 15 so as to cover it from the periphery.

There is a space a between the end face 1a of the case 1 of the sealed transformer and the casting agent 9 cast into the sealed transformer, and the end face 1 of the case 1
The potting agent 16 tries to enter through the clearance 1b between the abutting surface of the circuit board 10, but the potting agent 16 instantly covers the outer periphery of the case 1 of the sealed transformer. The air 18 in a is balanced with the settling force of the potting agent 16 and is not discharged to the outside, but is trapped inside.

Next, when the potting agent 16 is heated to harden, the air 18 in the confined space a of the closed type transformer expands, and the viscosity of the potting agent 16 decreases. The liquid penetrates into the liquid of the potting agent 16 and is discharged to the surface.

These through-holes are called bubbles 17, and remain even after the potting agent 16 is completely cured, and not only are they unsightly, but they also create a structure in which the conductive part of the electric circuit is connected to the outside air through the bubbles 17, and water, moisture, etc. Dust, flakes, and gas can easily enter, causing short circuits, disconnections, and corrosion. Therefore, the occurrence of air bubbles 17 must be visually inspected, and if air bubbles 17 have occurred, it is necessary to re-inject the casting agent 16 into the air bubbles 17 again.

As mentioned above, not only does it have many drawbacks in terms of quality and reliability, but it also has the disadvantages that it is impossible to automate and increases costs because it requires visual inspection of all products. Was.

Means for Solving rlWll The technical means of the present invention for solving the above-mentioned problems is that the lower surface of the circuit board on which the sealed transformer is mounted, on which the transformer is mounted,
It has a structure with round, square, oval, or triangular holes that pass through it, and a potting agent is cast into it.

The effect of this technical means is that on the circuit board on which the sealed transformer is mounted, there is a circle on the bottom surface on which the sealed transformer is mounted.
Square, elliptical, or triangular through holes are provided, and a potting agent such as epoxy or urethane is applied from below the hole in the circuit board to remove air from the space between the end face of the case of the sealed transformer and the potting agent. By injecting and discharging the liquid, it is possible to prevent the generation of bubbles.

Example Examples of the present invention will be described below.

The structure of the sealed transformer is completely the same as the conventional one, so a description thereof will be omitted. The circuit board to which the sealed transformer of the present invention is mounted will be explained with reference to FIG. 2. The circuit board 10 is provided with holes 12 for installation through which the metal pin terminals 6 of the sealed transformer are soldered. It has a structure in which a penetrating hole 19 having a round, square, oval, or triangular shape is provided in the center thereof.

To install such a circuit board 10, the metal pin terminal 6 of the sealed transformer is inserted into the hole 12 and passed through, and its protrusion 6a is connected to the copper foil 11 of the circuit board 1o by solder 13. There is a space a between the end surface 1a of the case 1 of the hermetic transformer and the casting agent 9 injected into the hermetic transformer, and air 18 exists therein.

Next, a method for casting the potting agent 16 will be described. A prescribed volume of the potting agent 16 is poured into the casting tray 14 made of a rubber mold. Further, the circuit board 10 to which the sealed transformer is attached is placed on the surface of the potting agent 16, and then pressed down from the upper direction Y. At that time, the potting agent 16 passes through the circuit board hole 19 provided on the lower surface of the sealed transformer, hits the potting agent 9 of the sealed transformer, and passes through the gap 1b between the end surface 1a of the case 1 and the contact surface of the circuit board 10. and flows out onto the surface of the circuit board 10.

The direction A in which the potting agent 16 flows is such that the air 18 between the end surface 1a of the case 1 of the sealed transformer and the potting agent 9 is expelled, and the potting agent 16 flows out from the gap 1b between the end surface 1a of the case 1 and the surface of the circuit board 10. discharge to.

As a result, as shown in Figure 1, case 1 of the sealed transformer
There is no air between the end surface 1a and the casting agent a, and the potting agent 16 completely enters the structure.

Therefore, in the next heating process for curing the potting agent 16, since there is no air inside the closed type transformer, engraving is not performed, and as a result, a structure can be obtained in which no air bubbles are generated at all.

As described above, by using a circuit board having a penetrating hole in the lower surface on which the sealed transformer is attached, it is possible to eliminate the generation of air bubbles from the sealed transformer.

Effects of the Invention As described above, the present invention utilizes a circuit board having round, square, elliptical, triangular, etc. penetrating holes on the bottom surface to which the sealed transformer is attached, thereby making it possible to connect the end face of the case of the sealed transformer. The air between the potting agent and the molding agent can be discharged by injecting the potting agent into the hole in the circuit board, thereby eliminating the generation of air bubbles.

Since there are no air bubbles, the conductive parts of the sealed transformer are completely isolated from the outside air by the potting agent, and water, moisture, dust, flakes, gas, etc. do not enter, preventing defects such as short circuits and disconnections. can be significantly reduced. In addition, since bubbles do not occur structurally, visual inspection of the appearance is not required, automation becomes easy, and significant improvements can be made in terms of quality, reliability, and cost.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of a circuit device in which a hermetic transformer is attached to a circuit board of the present invention, and Fig. 2 is a sectional view showing an embodiment of a circuit device in which a hermetic transformer is attached to a circuit board of the present invention. Figure 3 is a cross-sectional view of a transformer attached to a conventional circuit board, Figure 4 is a perspective view of a sealed transformer, and Figure 5 is a perspective view of the assembly structure of a sealed transformer. , FIG. 16 shows a cross-sectional view of a sealed transformer. 1...Case, 2...Lower end tsuba, 3...
... Upper end flange, 4 ... Cylindrical part, 5 ...
・Coil, 6...Metal pin terminal, 7...
・Magnetic material, 8... Lead wire, 9...
...Casting resin, 10...Circuit board, 11...
...Copper foil, 12...Mounting hole, 13...
... Solder, 14... Casting tray, 15...
...Electronic parts, 16... Potting agent, 1
7...Bubble, 18...Trapped air, 19...Circuit board hole.

Claims (1)

[Claims] It has a cylindrical part made of a plastic molded product through which a magnetic material is passed through the center and a coil is wound around the outer periphery, and an upper end flange and a lower end tsuba are provided at the upper and lower ends of the outer periphery of this cylindrical part, and a four The transformer body, which is made by planting square or round metal pin terminals and wrapping lead wires around their bases and connecting them by soldering, is inserted into a protective case made of cylindrical plastic with one side open, and then assembled. A hermetic transformer filled with a casting agent such as silicone, epoxy, or urethane, and a circuit board to which various electronic components are attached, have round, square, oval, triangular, etc. penetrating holes in the lower surface of the circuit board to which the transformer is attached. A circuit device in which a part or all of these electronic components are covered with a potting agent.