JPH0334240B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a terminal connection method applied to flat, thin, large-capacity display elements such as liquid crystal display elements and EL display elements.

[Conventional technology]

Conventionally, when connecting terminals of a liquid crystal display element (hereinafter referred to as LCD) to other circuit sections, the connection method shown in FIG. 4 has been used. That is, in FIG. 4, in order to connect the terminal 1a of the LCD display panel 1 for LCD display to the terminal 3a of the PWB (rigid wiring board) 3 via the intermediate member FPC (flexible circuit wiring board) 2, Between terminal 1a of LCD display panel 1 and terminal 2a on one side of FPC 2, and
The other terminal 2b of the FPC 2 and the terminal 3a of the PWB 3 are bonded via anisotropic conductive films 4, 4, respectively, and are pressed together while heating (the connection temperature at this time is 150 to 250℃, the pressure is 10 to 50Kg/cm ² ).

The anisotropic conductive film 4 is made of thermoplastic resin with conductive particles dispersed in it, and has the property of simultaneously satisfying conductivity between the opposing electrode and insulation between the adjacent electrodes, so it can be used for large screens. used for display
A very large number of terminals (560 to 640) with a fine terminal pitch (0.35 to 0.4 mm pitch) like an LCD,
That is, it is suitable as a connecting material for multiple terminals with fine pitch.

By the way, in this case, the terminal 1a of the LCD display panel 1 is normally connected to I・T・O, and also to the FPC 2,
Gold-plated material is usually used for the terminals 2a, 2b, and 3a of the PWD 3. This is based on past experience that gold plating has excellent surface oxidation prevention properties and good connection stability.

[Problem to be solved by the invention]

However, in the above connection method, for example
Looking at the connection between FPC2 and PWB3, FPC2 generally expands as the temperature rises,
Along with this, a force that tries to stretch also acts on the anisotropic conductive film 4, but since the PWB 3 is made of glass epoxy material, the stretch is small, and therefore, shear stress is generated in the plane direction at the above connection part. The connection often becomes unstable. Particularly when stored at high temperatures, connection failures due to the above mechanism are likely to occur.

Graph 1 in Figure 3 shows the above connections [FPC terminal (gold plating), PWB terminal (gold plating)] when stored at high temperature at a storage temperature of 70°C and a storage time of 240 hours.
This figure shows the relationship between the number of connection failures (the number of connections where the connection resistance value becomes ∞) and the connection temperature. From this graph 1, the connection temperature of the above connection part is 205 ~
Although the connection stability is good at 230℃, the quality becomes unstable at lower temperatures.

Therefore, the invention has been made in consideration of the problems in the conventional example, and provides a terminal connection that can significantly improve the connection stability in terminal connections using an anisotropic conductive film. The purpose is to provide a method.

[Means to solve the problem]

In order to solve the above problems, the terminal connection method of the present invention includes disposing an anisotropic conductive film between the other conductive part and the solder-plated terminal, and connects the above-mentioned other party conductive part and the solder-plated terminal with the solder. The method is characterized in that the solder layer of the plating terminal is heated to a temperature higher than its melting point, and the anisotropic conductive film is connected by thermocompression bonding, in which the conductive particles and resin are solidified in the form of melting into the solder plating layer.

[Effect]

According to the above configuration, the connection between the counterpart conductive part and the solder-plated terminal is performed by disposing an anisotropic conductive film between the two and thermocompression bonding. In thermocompression bonding, the solder layer of the solder-plated terminal is heated to a temperature higher than its melting point, and the anisotropic conductive film is solidified with the thin electrical particles and resin melted into the solder-plated layer. Therefore, the strength of the connection between the other conductive part and the solder-plated terminal can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

This embodiment is applied to connection processing between the terminal 2b of the FPC 2 and the terminal 3a of the PWB 3 when connecting the terminals of an LCD display panel (not shown) and the terminal 3a of the PWB 3 using the FPC 2 as an intermediate member. The terminals 2b of the FPC 2 are plated with gold 5, while the terminals 3a of the PWB 3 are plated with solder 6, an anisotropic conductive film 4 is interposed between the gold plated 5 and the solder plated 6, and they are bonded by thermocompression. The connection is made by

In the above thermocompression bonding, the terminal 3a on the PWB 3 side is coated with Sn:Pb=6:4 eutectic solder plating 6, so the solder melts at a connection temperature of 183°C, and at the same time, the anisotropic conductive film Resin 7 of 4 also melts,
The conductive particles 8 in the anisotropic conductive film 4 melt into the solder plating layer 6 and solidify, as shown in an enlarged view in FIG.

By fixing the conductive particles 8 of the anisotropic conductive film 4 in a melted state in the solder layer in this way, the connection stability is improved compared to, for example, fixation in the form of surface contact between gold plating and the anisotropic conductive film. This will improve the results. Therefore, even if shear stress is generated in the plane direction at the connection part due to the expansion of the FPC 2 due to temperature rise and the accompanying force acting on the anisotropic conductive film 4 to stretch, there is sufficient stress to counteract this. Connection strength is ensured.

In the above embodiment, #3051 manufactured by Hitachi Chemical Co., Ltd. is used as the anisotropic conductive film 4. This anisotropic conductive film 4 has a melting point of about 150°C, and can sufficiently withstand an operating temperature of about 80°C.

Graph 2 in FIG. 3 shows the relationship between the number of failed connections and the connection temperature when the connection portion according to this embodiment is stored at a high temperature of 70° C. for a storage time of 240 hours. This graph 2 and the graph 1 mentioned earlier
[FPC terminal (gold plating), PWB terminal (gold plating)]
From the comparison, it is recognized that the quality of the connection portion can be stabilized at a lower connection temperature of 190 to 230° C. in the case of this example.

Note that the terminal pitch in this case is 0.4 mm, and the number of terminals is 560.

In the above embodiment, the case where gold plating 5 was applied to the terminal 2b of the FPC 2 was explained, but the connection strength can be similarly improved when solder plating is applied thereto.

Furthermore, the same effect can be achieved even if the terminals of the LCD display panel are soldered to connect the LCD display panel and the FPC. Of course, the present invention can be applied not only to LCDs but also to connection of terminals in other display elements.

[Effects of the Invention] As described above, the terminal connection method of the present invention includes disposing an anisotropic conductive film between the mating conductive part and the solder plating terminal, and connecting the mating conductive part and the solder plating terminal. The solder layer of the solder plated terminal is heated to a temperature higher than its melting point, and the anisotropic conductive film is connected by thermocompression bonding, in which the conductive particles and resin are solidified in the form of melting into the solder plated layer.

This has the effect that the connection strength between the counterpart conductive part and the solder-plated terminal is improved, and the quality of the connection part can be significantly improved.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention. FIG. 1 is a sectional view showing one embodiment of the present invention. FIG. 2 is an enlarged sectional view of section A in FIG. 1. FIG. 3 is a graph showing measured data comparing the results of the example with the conventional example.
FIG. 4 is a sectional view showing a conventional example. 2 is FPC (flexible circuit board), 3 is
PWB (hard wiring board), 4 is an anisotropic conductive film, 5 is gold plating, 6 is solder plating, 7 is resin, and 8 is conductive particles.

Claims (1)

[Claims] 1 An anisotropic conductive film is placed between the other conductive part and the solder-plated terminal, and the above-mentioned other party conductive part and the solder-plated terminal are heated to a temperature higher than the melting point of the solder layer of the solder-plated terminal. 1. A method for connecting terminals, characterized in that a conductive film is connected by thermocompression bonding in which conductive particles and resin are melted into a solder plating layer and solidified.