JPH04163992A - Connecting method for circuit board - Google Patents

Abstract

PURPOSE:To simplify steps by temporarily connecting to adhere circuit boards to be connected to each other, and then connecting them with a shape memory alloy jig. CONSTITUTION:Since a first circuit board 11 is temporarily connected to be adhered to a second circuit board 12 through insulating adhesive, positional deviation between the boards 11 and 12 until a shape memory allay jig 17 is mounted. Thereafter, when the jig 17 of shape memory alloy is mounted, adhesive existing between the connecting conductive layers of the boards 11, 12 are fluidized by the pressure, or the pressure and the heat, the thickness of the remainder is reduced to perform sufficient continuity. Since any heating step is not required to temporarily connect to be adhered with the adhesive, steps are not complicated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit board connection method for electrically connecting circuit boards having electronic circuits (including lead patterns) to each other.

[Summary of the Invention] The present invention provides a method for connecting circuit boards, in which a first circuit board and a second circuit board are temporarily bonded, and both boards are connected using a shape memory alloy jig. This prevents misalignment, simplifies the process, and enables highly reliable connections between circuit boards.

[Conventional technology]

There are two main ways to electrically connect the connection part of the first circuit board and the connection part of the second circuit board:
There are different types.

The first method is to connect a connecting conductive layer (3) at a connecting portion (2) of a first circuit board (for example, a liquid crystal display board) (1) to a second circuit board, as shown in FIGS. 4A and B. (For example, a flexible wiring board) A method of connecting the connection conductive layer (5) of (4) using a pressure contact member (holding jig) (6) made of a shape memory alloy in a state where they are in contact with each other. (Unexamined Japanese Patent Publication No. 1983-
(See Publication No. 203698).

The second method is to connect a connecting conductive layer (3) at a connecting portion (2) of a first circuit board (for example, a liquid crystal display board) (1) and a second circuit board, as shown in FIGS. 5A and B. (for example, a connectable wiring board) (4) and the connecting conductive layer (5) are once connected by heat fusion through a conductive adhesive (anisotropic adhesive) (7), and then shape memory This is a method of connection using a pressure contact member (6) made of an alloy (see Japanese Patent Laid-Open No. 62-229673).

[Problem to be solved by the invention]

In the first method described above, the first and second circuit boards (1)
Since the circuit boards (1) and (4) are connected to each other by the pressure contact member (6), both the circuit boards (1) and (4)
) After alignment of the boards (1) and (4) until they are fixed with the pressure contact member (6), or during the fixing work using the pressure contact member (6), problems such as misalignment between the two boards (1) and (4) may occur. Very likely.

In addition, in the second method, since the conductive adhesive (7) is used, there is no need for positional deviation between the two substrates (1) and (4). It requires thermal bonding, making the process complicated.

In view of the above-mentioned points, the present invention provides a method for connecting circuit boards that prevents misalignment, simplifies the process, and provides continuity between circuit boards with high reliability.

[Failure to solve the problem]

The method for connecting a circuit board according to the present invention includes a method for connecting a first circuit board (
11) and the second circuit board (12) are temporarily bonded,
Both circuit boards (11) and (12) are connected by a shape memory alloy jig (17).

An insulating adhesive (18) is used for temporary bonding. Moreover, this adhesive (18) is selected from one that softens at room temperature or when heated.

[Effect]

In this method, since the first circuit board (11) and the second circuit board (12) are temporarily bonded via an insulating adhesive (18), a shape memory alloy shaped jig (17) is used. ) can be prevented from being misaligned between the circuit boards (11) and (12) until they are installed. After that, when the shape memory alloy jig (17) is attached, the connection conductive layer (1
The adhesive (18) existing between 5) and (16) flows,
By reducing the remaining thickness d to 2 μm or less, sufficient conduction can be achieved. Temporary bonding using this adhesive (18) does not require any heating process, so the process is also simplified.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1 to 3 show the steps according to this embodiment. In the figure, (11) is a first circuit board such as a liquid crystal display board, (12) is a second circuit board such as a flexible wiring board, (13) is a third circuit board, and (14) is a liquid crystal display board. The connection part of the plate (11) to the flexible wiring board (12), (
15) is a connection conductive layer led out to this connection part (14),
(16) is a connection conductive layer of the flexible wiring board (12).

In addition, (17) is a holding jig or pressure welding member (for example, 0.5 mm thick) made of a shape memory alloy such as Ni-Ti alloy.
It is.

This shape memory alloy remembers this shape when it is processed into a certain shape in the austenite phase state by heating at high temperature, and the temperature at which the austenite phase changes to the martensite phase (referred to as the transformation temperature, 10 to 100°C) It has the property of returning to the originally memorized shape when it is processed into another shape again at a temperature below (known as 2000) and then heated above the transformation temperature.

Next, the procedure for connecting the liquid crystal display board (11) and the flexible wiring board (12) will be described.

First, a wide pressure contact member (17) having a U-shaped cross section is heated, for example, at a high temperature, and in a state where the alloy is in the austenite phase, a wide pressure contact member (17) suitable for clamping the connection portion (14) and the wiring board (12) is heated. It is processed into a shape and this shape is memorized (see FIG. 1A).

Next, this pressure contact member (17) is cooled to a temperature below the transformation temperature of the shape memory alloy, and in the state of martensitic phase, it is shaped into, for example, a U-shape so that it can be easily attached to the connection portion (14) and the wiring board (12). Cut both ends into a slightly open shape (see Figure 1B).

Next, the connecting conductive layer (15) of the adhesive part (14) and the connecting conductive layer of the wiring board (12) are connected via an insulating and tack adhesive (18) that can be softened at room temperature or by heating. (1
6) Attach the connecting portion (14) and the wiring board (12) so that they are aligned (see FIG. 1, C1, FIG. 2, and FIG. 3A). In this step, the connection part (14) and the wiring board (
12) is temporarily fixed with adhesive.

Next, the pressure contact member (17) shown in FIG. 1B is attached to the connecting portion (14) and the wiring board (12) which are temporarily fixed to each other (see FIG. 1 and FIG. 3B).

Next, in this state, the pressure contact member (17) is heated above the transformation temperature to restore it to the memorized shape shown in FIG. 1A. As shown in FIG. 1E and FIG. 3C, the pressing member (17) presses and joins the connecting portion (14) of the liquid crystal display panel (11) and the wiring board (12) with uniform force by returning to the original state. That is,
At this time, the pressure of the pressure contact member (17) or the pressure contact member (1
The insulating adhesive (18) is made to flow by the pressure and heating in step 7), and the thickness d of the adhesive (18) remaining between the connecting conductive layers (15) and (16) that is in contact with the pressure contact member (17) is determined. Pressure bonding is performed at a pressure of 2μ or less.

In addition, when attaching the pressure contact member (17), it is possible to use a cushioning material (19) made of silicone rubber (for example, 0.2 m++ thick) as shown in the figure;
) is also possible.

In this way, the connecting portion (14) of the liquid crystal display board (11) and the wiring board (12) are connected to their respective connecting conductive layers (15) and (
16) with insulating adhesive (18) so that they are aligned.
Since the pressure contact member (17) is attached while temporarily adhesively bonded, it is possible to facilitate positioning and prevent misalignment between the connecting conductive layers (15) and (16) until they are fixed. can. After the pressure contact member (17) is installed, the adhesive (1) remaining between the connection conductive layers (15) and (16) due to the pressure of the pressure contact member (17) or the pressure and heating is applied.
By setting the thickness d of 8) to 2 μm or less, sufficient conduction can be obtained between the connecting conductive layers (15) and (16).

Therefore, when interconnecting the two circuit boards, it is possible to achieve a connection with good reliability without positional deviation and by simplifying the process.

Next, a specific example will be shown.

Example 1 A liquid acrylic adhesive solution (e.g. Finetac MD310-40 manufactured by Dainippon Ink & Co., Ltd.) was applied to both circuit boards (
11) It is coated on either one of the connection conductive layers (15) and (16) in (12) so that the thickness after drying is 10 μm or less, and then dried. Between the circuit boards (11) and (12)
) are bonded together while aligning the connecting conductive layers (15) and (16) using alignment marks. Thereafter, a pressure contact member (17) made of a shape memory alloy is attached and held in pressure contact to establish electrical continuity between the connection conductive layers (15) and (16) of both circuit boards (11) and (12).

Example 2 Commercially available thermoplastic heat-sensitive micro-tack adhesive film (for example, SCC NPIII, NPIOl, etc.) (thickness: 50 μm)
m) on the connecting conductive layer (1) of both circuit boards (11) and (12).
5) or (16) by heating (e.g. 100°C
) while pasting. After that, the connecting conductive layer of both circuit boards (11) and (12) is connected via this adhesive film.
(15) and (16) are pasted together while aligning using alignment marks. After that, a pressure contact member (17) made of a shape memory alloy is attached and both circuit boards (1
1) and (12) are pressed together. Next, gradually heat the
Keep in oven at 00°C for 1 hour.

Comparative Example A liquid acrylic adhesive solution (e.g. MD310-40 manufactured by Dainippon Ink & Chemicals) was applied to both circuit boards (11) and (12).
) is coated on either one of the connecting conductive layers (15) and (16) so that the thickness after drying is 5 μm or less, and dried.

Thereafter, both circuit boards (11) and (12) are bonded together while aligning them using alignment marks.

Results of the remaining thickness d of the adhesive between the upper and lower connecting conductive layers (15) and (16) and the conduction resistance value between the upper and lower connecting conductive layers (15) and (16) in Example 1.2 and Comparative Example are shown in Table 1.

Table 1 As is clear from Table 1, an insulating adhesive that softens at room temperature or when heated is selected, and after it is interposed between the reconnection conductive layers, it is bonded between the reconnection conductive layers using a pressure contact member or by using a pressure contact member and heating. By setting the thickness of the remaining adhesive to 2 μm or less, sufficient conduction between the upper and lower connecting conductive layers can be obtained.

Although the top peeling method was applied to the connection of a flexible wiring board to a liquid crystal display board, it can also be applied to the connection of other general electronic circuit boards.

〔Effect of the invention〕

According to the method for connecting circuit boards of the present invention described above, circuit boards to be connected to each other can be connected together with sufficient electrical conductivity while preventing misalignment between the connecting conductive layers and simplifying the process. be able to.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing an embodiment of the present invention, Fig. 2 is a perspective view showing a part of the process, Fig. 3 is an enlarged view of the process, and Fig. 4 is a process diagram showing an embodiment of the present invention.
5 and 5 are configuration diagrams showing conventional examples, respectively. (11
) is a liquid crystal display board, (12) is a flexible wiring board, (15)
, (16) is a connection conductive layer, (17) is a pressure contact member, (18)
) is an insulating adhesive.

Claims (1)

[Scope of Claims] A method for connecting circuit boards, comprising temporarily adhering a first circuit board and a second circuit board, and connecting the two boards using a shape memory alloy jig.