JPS6358847A - Molding of electronic circuit - Google Patents

Abstract

PURPOSE:To contrive to be able to finish a molding process in one process by a method wherein a molding resin given thixotropy is filled in the roughly boxlike resin reservoir part of a frame body and the upper and lower sides are inverted immediately after the frame body is covered with a circuit substrate in a cover form. CONSTITUTION:A frame body 3 is put in such a way that a boxlike opening part is positioned at its upper surface, its bottom part is used as a resin reservoir part 3a and a proper amount of a molding resin 4 is filled in the interior of this resin reservoir part 3a. As this molding resin 4, a polyurethane resin wherein thixotropy is highly adjusted and so on are selected. Then, the fame body 3 is covered with a circuit substrate 1 in a cover form, both are combined, the upper and lower sides are inverted and such a curing treatment as heating is performed. Thereby, the molding agent 4 filled in the resin reservoir part 3a is dropped is whole amount on the side of circuit substrate 1 by sofening due to heating in addition to a gravity and electronic circuit parts 2 are completely buried in the resin and cured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applied to molds for electronic circuits that are used outdoors under adverse conditions, such as those used in automobiles, and are molded for purposes such as moisture proofing. It is about the method.

K. Prior Art There is a conventional molding method for this type of electronic circuit as shown in FIG. First, a frame body 11 made of resin or the like is glued with an epoxy adhesive to a predetermined position of a circuit board 1 on which electronic circuit parts 2 such as transistors, resistors, and capacitors are arranged. The circuit board 1 is made white as the bottom surface, and after the adhesive has hardened, an appropriate amount of molding resin such as epoxy resin is injected into the frame 11, and then a hardening process such as heat treatment is performed. After the above-mentioned processing is completed, the molding step 12 is further bonded to the upper surface of the frame 11, and the molding process is completed.

At this time, if the electronic circuit is connected to the outside by a lead wire 13, a through hole is provided in the side surface of the frame 11 as shown in the figure, and a rubber grommet is inserted into this through hole. 14 etc., this grommet 1
When performing the molding described above, the leads l1l13 are drawn out through the leads 11 and 13, but when performing the molding described above, the parts for hardening treatment are In order to prevent the mold resin, whose viscosity is temporarily extremely reduced during heat treatment, from flowing out, this portion is sealed in advance with, for example, silicone rubber that hardens at room temperature.

K Problems to be Solved by the Invention] However, in the conventional molding method described above, the steps are listed in order: (1) The circuit board and the frame are bonded and a curing process is performed.

■ Inject the mold resin and perform the curing process.

■ Glue the base and frame and perform a hardening process.

It takes three steps to achieve this, and there are many steps, and moreover, it involves repeating processes that require a relatively long time (typically, about one hour is required), such as the curing process. Therefore, the residence time in the production line is long, resulting in the problems of high manufacturing costs and the problem of complicated production management.

Means for Solving Problem K] The present invention is a specific means for solving the problems that occur in the conventional molding method described above, in which electronic circuit components, connection terminals, etc. are provided on one side of a circuit board. In a method for molding an electronic circuit, the electronic circuit is provided with a frame body such as a resin case, and a liquid molding resin is injected into the frame body and cured. The resin reservoir is filled with an appropriate amount of thixotropic molding resin in advance, and after covering the frame with the circuit board in a lid-like manner, the circuit board is immediately turned upside down. By providing a method for molding an electronic circuit characterized in that the molding resin is cured as the bottom surface, the number of steps can be reduced and the problems of the conventional methods can be solved.

K Embodiment Next, the present invention will be described in detail based on an embodiment shown in the drawings.

In order to facilitate understanding, parts that are the same as those in the conventional example will be described with the same reference numerals, and descriptions of some overlapping parts will be omitted.

1, the electronic component 2 is the same as the conventional example.
This is a circuit board on which a frame body 3 is attached to the circuit board 1, and molding is performed.
According to the present invention, the frame body 3 has a mountain-like shape in which the lid of the conventional example is also integrated.

FIG. 2 shows the molding method using the frame 3 of the present invention in the order of steps. First, as shown in FIG. 2 (Δ), the frame 3 has a mountain-shaped opening on the top surface. is placed so that the bottom part becomes the resin reservoir part 3a, and this resin reservoir part 3
The inside of a is filled with a droplet amount of mold resin 4. At this time, the molding material 1]W4 is selected from polyurethane resin whose thixotropy is adjusted to be high, such as the one supplied to the market by the resin manufacturer tJIff for surface coating of electronic circuit components. . The frame body 3, which has been filled with the molding resin 4 in advance, is covered with the circuit board 1 at a predetermined position in a lid shape and assembled. . Next, the roughly assembled circuit board 1 and frame 3 are turned upside down as shown in FIG. 2(B).
A curing process such as heating is performed, but at this time, the entire amount of the molding agent 4 filled in the resin reservoir 3a falls onto the circuit board 11111I due to the softening caused by the heating applied to gravity, completely sealing the electronic circuit component 2. It hardens after being buried, and at this time, even if there is a gap (≧0°3 mm) between the circuit board 1 and the frame 3, as shown by arrow S in the figure, the mold resin will harden. No leakage due to the thixotropy given to 4.

What is shown in FIG. 3 is another embodiment of the present invention, in which a pair of terminal plates 5 are provided at opposite ends of the circuit board 1 to form a shape, so that the frame body 30 also has a shape, This corresponds to when beans are combined in a complicated manner.
In such a case, a resin reservoir 30a is formed by providing two ribs 30b orthogonal to the vertical wall on the frame 30 as shown in FIG. 4 can be implemented in exactly the same manner as in the previous embodiment, and the circuit board 1, the terminal board 5, the frame 3
The same applies to the gaps that occur between each of the zeros.

[Effects of the Invention] As described above, the present invention provides a method for molding an electronic circuit, in which the frame body is shaped to form a substantially box-shaped resin reservoir, and
The resin reservoir is filled with an appropriate amount of thixotropic molding resin in advance, and after covering the frame with the circuit board in a lid-like manner, the frame is immediately turned upside down and the circuit board is placed as the bottom surface. By performing a curing process on the mold resin, the thixotropy imparted to the mold resin eliminates leakage of the mold resin, eliminating the need for preliminary adhesion of the frame, and also creating a resin reservoir in the frame. By setting up a molding section, filling it with molding resin, and then turning it over so that the circuit board can be molded by gravity, the molding process, which conventionally required three steps, can be reduced to one step, reducing the number of steps. This has an excellent effect on reducing manufacturing costs, and also reduces residence time in the production line, which is also effective in simplifying process control and the like.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an embodiment of the electronic circuit molding method according to the present invention, FIG. 2 is a sectional view showing the same embodiment in the order of steps, and FIG. FIG. 4 is an exploded perspective view of the embodiment; FIG. 4 is an exploded perspective view of main parts of the embodiment shown in FIG. 3; and FIG. 5 is an exploded perspective view of the conventional example. 1...Circuit board 1a...Wiring pattern 2...Electronic circuit components 3.30...Frame bodies 3a, 30a...Resin reservoir part

Claims (1)

[Claims] In a method of molding an electronic circuit, the electronic circuit is provided with a frame such as a resin case on one side of a circuit board, and a liquid molding resin is injected into the frame and cured. , the frame body has a shape having a substantially box-shaped resin reservoir, the resin reservoir is filled with an appropriate amount of thixotropic molding resin in advance, and the frame body is covered with the circuit board. 1. A method for molding an electronic circuit, which comprises immediately covering the circuit board in a shape and then immediately turning it upside down and performing a curing process on the molding resin with the circuit board as the bottom surface.