JPH0277019A - Electrooptical device and conductive connecting method - Google Patents

Abstract

PURPOSE:To prevent the peeling of a plating and conductive adhesive material by covering the circuit board of a conductive junction and the substrate around the same with a resin and further disposing a 3rd substrate thereon, then curing the resin. CONSTITUTION:The circuit board of the conductive junction and the substrate around the same are coated with the resin 9 at the time of conducting and connecting the terminal of the conductive film 7 on the circuit board 6 via the conductive adhesive material 8 to the terminal 5 of the conductive film formed on the substrate 1B of an electrooptical element, etc. Further, the 3rd substrate 10 is disposed thereon and the resin 9 is cured, so that the 3rd substrate 10 and the granular material 1B or the circuit board 6 are adhered by the resin. The stress of the shrinkage arising from curing of the resin and the expansion and contraction arising from heating and cooling at the time of use is dispersed to the 3rd substrate 10 and the substrate 1B even if such shrinkage exists. The stress by the expansion and contraction is hardly applied to the conductive junction and the defects such as peeling are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electro-optical device and a conductive connection method.

[Prior Art] Conventionally, terminals of transparent conductive films of electro-optical elements such as liquid crystal display elements and electrochromic display elements, and circuit boards such as flexible printed circuit boards or drive circuits for connection to external drive circuits have been mounted. The terminals of the installed circuit board are placed so that both terminals face each other, and a conductive adhesive such as solder, anisotropic conductive film, or silver paste is placed between the two terminals to make a conductive connection. ing.

Furthermore, this conductive connection portion may peel off due to external force applied to the electro-optical element or circuit board, thermal expansion, or the like. For this reason, in order to reinforce this conductive connection part, a resin such as an ultraviolet curable resin is applied to the circuit board of the conductive connection part and the substrate around it, and then cured.

[Problem to be solved by the invention] Such reinforcement is performed by controlling the amount of resin used, the amount of ultraviolet irradiation, the amount of heat generated, etc., but the control range tends to be narrow.
Productivity was poor (there was a risk of defects occurring).

In other words, expansion and contraction due to hardening of the resin, expansion and contraction due to heating and cooling, and furthermore, due to the application of external force to this, weak parts of the conductive connection part may peel off, or part of the glass of the board may break. There was a risk that this would lead to a problem of wire breakage.

In particular, as recent liquid crystal display elements and the like have become increasingly high-definition, the number of terminals has increased and their pitch has become finer. For this reason, the area of each terminal is reduced, and even a weak force is likely to cause wire breakage. Furthermore, in such liquid crystal display devices, if even one of the many terminals is disconnected, it becomes defective. .

[Means for Solving the Problems] The present invention has been made to solve the above problems, and provides an electro-optic device with an electro-optic medium sandwiched between a pair of electrode-attached substrates and sealed around the outside of the seal. In an electro-optical device in which a terminal for connecting to an external drive circuit is formed on a substrate, and a circuit board is conductively connected to the terminal on the substrate using a conductive adhesive, the third substrate is used as the electro-optical device. An electro-optical device disposed on a terminal portion of a substrate, and an adhesive layer made of resin is formed between the third substrate and the substrate or circuit board of the electro-optical element, and an electro-optical device formed on the substrate. The terminal of the conductive film on the circuit board is electrically connected to the terminal of the conductive film on the circuit board by placing a conductive adhesive between the terminals with both terminals facing each other, and the resin is placed on the board or circuit board. A conductive device characterized in that a resin adhesive layer is formed between the third substrate and the substrate or circuit board by supplying a third substrate, placing a third substrate thereon, and curing the resin. The present invention provides a connection method, and particularly an electro-optical device or a conductive connection method in which a substrate made of the same material as the substrate on which the terminal is formed is used as the third substrate.

In the present invention, when a terminal of a conductive film on one circuit board is conductively connected to a terminal of a conductive film formed on a substrate of an electro-optical element etc. via a conductive adhesive, the circuit board of the conductive connection part is By covering the board and the surrounding board with resin, and then stacking and bonding a third board, even if there is expansion and contraction due to heating and cooling when the resin hardens or when the manufactured device is used, the stress will be absorbed. 3 and the substrate on which the terminals are formed, and does not strongly contact the conductive connection parts (this makes it difficult to cause problems such as peeling of the conductive connection parts or disconnection due to cracking of a part of the glass of the board).

As the terminal of the conductive film formed on the substrate of the present invention, copper,
Thin wires or foils made of aluminum or chromium, transparent conductive films made of indium oxide or tin oxide, or plating or conductive paste made of nickel, gold, silver, etc. baked onto these can be used.

Although a simple printed circuit board can be used as this substrate, a substrate for an electro-optical element is suitable in the present invention.

This electro-optic element is an element in which an electro-optic medium such as a liquid crystal substance or an electrochromic substance is sandwiched between substrates such as glass or plastic having an electrode made of a transparent conductive film on at least one side. Suitable for liquid crystal display elements using

In particular, as the material for the substrate, it is preferable to use a glass substrate from the viewpoint of reliability, strength, durability, etc., and the effect of the present invention is extremely high when the glass substrate has a large difference in expansion coefficient from the reinforcing resin.

As the circuit board to be conductively connected to the terminals of the substrate of the present invention, a circuit board such as a flexible printed board on which a terminal of a conductive film such as copper foil is formed can be used.

In the present invention, the terminals of the substrate such as the electro-optical element and the terminals of the circuit board are electrically connected to each other using a conductive adhesive. For this purpose, as has been done conventionally, the terminals on the board and the terminals on the circuit board are arranged so that one terminal faces each other, and solder, anisotropic conductive film, silver paste, etc. A conductive adhesive may be placed to make a conductive connection.

Before this conductive connection, pretreatment may be applied to each terminal to facilitate soldering, etc. Specifically, in the case of soldering, nickel plating and preliminary soldering may be performed on each terminal. Yes, known conductive connection processing methods can be used.

In the present invention, after the circuit board and the circuit board are electrically connected in this way, the circuit board at the electrically conductive connection portion and the surrounding boards are covered with an adhesive resin, and then a third board is superimposed. Then, the resin is cured, and the third substrate is bonded to a substrate or a circuit board on which terminals such as electro-optical elements are formed.

As a result, even if there is shrinkage due to hardening of the sealant or expansion and contraction due to heating and cooling during use, the stress is dispersed between the third substrate and the substrate, and this conductive connection part is exposed to the stress due to expansion and contraction. This makes it difficult for defects such as peeling to occur.

The resin used in the present invention can be the resin that has been conventionally used to reinforce conductive connection parts, and has no adverse effect on the board, circuit board, third board, conductive connection part, etc. during curing or subsequent use. Known resins such as ultraviolet curable resins and thermosetting resins that do not give any harmful effects can be used. In particular, from the viewpoint of productivity, it is preferable to use ultraviolet curing resins such as modified acrylate resins and urethane acrylate resins.

This (H fat) can also be mixed with granular materials such as plastic, glass, ceramic, etc. in the form of particles, hollow particles, fibers, etc. that relieve stress. The size is about 10 to 500 μm,
The mixing amount is 1 to 50vol% based on the total amount of resin and granules.
It is fine as long as it is mixed in to some extent.

A dispenser so as to cover at least a portion of the circuit board of the conductive connection part and the surrounding board with such resin;
It is supplied and applied using a printing machine, etc.

Thereafter, a third substrate is placed thereon, the resin is cured, and the third substrate is bonded to a substrate or a circuit board on which terminals such as electro-optical elements are formed.

As this third substrate, a simple plate of glass, plastic, etc. can be used. In particular, it is preferable to use a plate made of the same material as the substrate on which the terminals are formed, so that the expansion and contraction of both will be the same, and less stress will be applied.

Furthermore, if the resin is an ultraviolet curable resin, the plate must be transparent so that ultraviolet rays can pass through it.

The shape of this third substrate should normally be approximately the same shape as the terminal portion of a substrate such as an electro-optical element. of course,
If only a part of the terminal portion of the substrate that extends outside the seal of the electro-optical element has the terminal formed thereon, the shape may be such that only that part is covered; The shape may be larger than the terminal part due to the connection with the peripheral part. However, the shape is such that it covers the part where the terminal is conductively connected.6Also, the thickness of this third board may be set as appropriate considering strength, ease of handling, etc. When applied to the electro-optical device, it is preferable to make the third substrate thinner than the electro-optic device so that the third substrate does not exceed the thickness of the electro-optic device even when stacked.

Thereafter, in the case of a thermosetting resin, the resin is heated and cured, and in the case of an ultraviolet curable resin, the resin is cured by irradiation with ultraviolet rays.

This makes it possible to obtain a connection that is less prone to defects such as peeling of the conductive connection part due to shocks such as thermal shock, while making use of the original effect of reinforcing the conductive connection part.

This makes it possible to increase the reliability of conductive connections even for liquid crystal display elements that have an extremely large number of terminals and each terminal area is small, such as high-definition liquid crystal display elements that have recently been increasing in number. Can be done. As a specific example, 6
With a configuration of 40X 400 dots 3 color filter.

A large number of terminals such as 1920 terminals are drawn out on the segment side, and in order to drive at 1/200 duty, 3840 terminals are provided on the segment side and 400 terminals on the common side, for a total of 4240 electrodes. , that many terminals are required, and if a defective conductive connection occurs at even one point, the liquid crystal display element itself becomes defective.Furthermore, this defective conductive connection is not limited to complete disconnection; Since a significant increase in resistance value is also a problem, an increase in conductive connection resistance caused by part of the terminal peeling off due to stress due to thermal shock is also a major problem.

According to the present invention, the risk of such defects occurring can be significantly reduced.

This will be explained with reference to the drawings.

FIG. 1 is a sectional view of a typical example of the present invention in which terminals of a liquid crystal display element and terminals of a flexible printed circuit board are electrically connected.

In FIG. 1, IA is an upper substrate such as glass or plastic, IB is a lower substrate, and 2A and 2B are ITO (InxOs-3nOx) and 5n formed on both substrates, respectively.
A transparent conductive film such as Oi, 3 a sealing material formed around the substrate, 4 a liquid crystal substance sealed between both substrates, 5 a terminal made of a transparent conductive film exposed outside the seal of the lower substrate,
6 is a circuit board such as a flexible printed circuit board, 7 is a conductive film such as copper foil formed on the circuit board, 8 is a conductive adhesive such as solder or an anisotropic conductive film, and 9 is a conductive connection part thereof. The resin covering the substrate, IO, represents a third substrate such as glass, plastic, ceramic, etc., which is laminated on top of the resin.

In the present invention, the reinforcing resin is used to cover the circuit board at the conductive connection part and the surrounding boards, and to bond it to the third board. It is sufficient that the circuit board 6 covers the top and a part of the substrate IB, and covers the entire bottom surface of the third substrate.However, as in this example, the circuit board 6 covers the terminal 5 of the electro-optical element substrate IB. If most of the part is covered, it may be bonded to cover part of the vicinity of the terminal part (in this example, the side surface of the board IA) of the board IA facing the board IB on which the terminal is formed. .

Also in this example, since the width of the circuit board is usually narrower than the width of the electro-optical element board in the horizontal direction of the terminal, which is the front-rear direction in the figure, the resin is made to cover the top of the board IB. is preferred.

In addition, if the circuit board 6 does not cover the entire terminal 5 of the electro-optical element board IB and ends before the sealing material 3, the gap between the sealing material 3 and the circuit board 6 can be filled with resin. It is preferable to cover it.

FIG. 2 is a sectional view showing such an example.

In FIG. 2, IIA and IIB are upper and lower substrates, 12A and 12B are transparent conductive films formed on both substrates, 13 is a sealing material, 14 is a sealed liquid crystal substance, 15 is a terminal, and 16 is a transparent conductive film formed on both substrates. 17 is a conductive film formed on the circuit board; 18 is a conductive adhesive; 19
Reference numeral 20 indicates a resin covering the conductive connection portion, and 20 indicates a third substrate made of glass, plastic, ceramic, etc., which is laminated on the resin.

In this example, since the circuit board 16 does not extend to the seal portion, the resin covers and adheres to the portion of the lower substrate 11B outside the seal and the side surface of the upper substrate IIA. However, if the gap between the circuit board 16 and the seal part is large, the resin may cover only the portion of the lower board 11B outside the seal, and may not cover the side surface of the upper board 11A. , only a portion of the lower substrate 11B outside the seal may be covered.

Also, in this example, the third board has a shape corresponding to the terminal portion outside the seal of the lower board 11B.
The shape may be approximately similar to the shape of the circuit board 16. However, if the resin is applied to almost the entire area of the lower substrate 11B outside the seal, the shape of the third substrate is not as good as that of the lower substrate from the viewpoint of the purpose of the present invention to reduce stress. It is preferable that the shape corresponds to the terminal portion outside the seal 11B.

In addition to this, the present invention can be applied in various other ways as long as the effects of the present invention are not impaired.

[Function] In the present invention, 1. When a terminal of a conductive film on a circuit board is conductively connected to a terminal of a conductive film formed on a substrate of an electro-optical element etc. through a conductive adhesive, the conductive connection part of the circuit board and its surroundings are The third substrate and the substrate or circuit board are bonded with the resin by covering the substrate with resin, placing the third substrate thereon, and curing the resin.

As a result, even if there is shrinkage due to resin curing or expansion and contraction due to heating and cooling during use, the stress is dispersed between the third substrate and the substrate, and stress due to expansion and contraction is added to this conductive connection part. It becomes more durable and less likely to cause defects such as peeling.

This specific effect will be explained by taking as an example a case where expansion and contraction stress occurs due to heating and cooling in a liquid crystal display device using a glass substrate.

When such stress is applied when the third board is not used, the stress is concentrated at the conductive connection between the board and the circuit board. For this reason, breakdown is likely to occur from the weakest part of the conductive connection parts. For example, if there is a part where the adhesion of the plating on the transparent electrode of the terminal is weak, peeling will occur there, and if there is a part where there is less conductive adhesive material, peeling will easily occur there. This becomes extremely problematic when a large number of terminals are taken out at narrow pitches.

In the present invention, since this conductive connection part is sandwiched between the substrate or the third substrate, stress due to expansion and contraction of the resin is distributed and applied to the substrate on which the terminal is formed and the third substrate. Almost no bending stress is applied to the conductive connection part, and plating and peeling of the conductive adhesive are less likely to occur.

In addition, if the third board is not used and the area of the conductive connection part of each terminal is large, the strength of that part will be large and peeling of each terminal will not occur ((However, if the terminal is formed Strong stress is applied to the board being used, making it more likely that the board itself will crack.

In this case as well, by using the third substrate, the stress caused by the expansion and contraction of the resin is distributed between the substrate on which the terminal is formed and the third substrate, compared to the case where the third substrate is not used. Therefore, it can withstand stress up to about twice as much. For this reason, cracks in the substrate are less likely to occur.

[Example] Example 1 Flexible printed circuit board having terminals made of ITO electrodes (electroless nickel plating layer formed on the surface) and tinned copper terminals on a 1.1 mm thick glass substrate of a liquid crystal display element with a cell size of 105 aoo x 80 mm. conductively connect them using solder, cover the connection part with ultraviolet curing resin as shown in Figure 1, and form a third board with a thickness of 90 mm.
Laminate glass plates with a size of 3 mm and a thickness of 0.7 mm,
The resin was cured by irradiation with ultraviolet light and bonded. The size of the extended portion of the substrate outside the seal on which the terminals were formed was 105 mm x 3 mm.

Note that as a comparative example, a sample in which the third substrate was not laminated was also manufactured.

Using 10 samples each of this example and comparative example, heat cycle (-40°C 3 minutes - 80°C 3 minutes, 20
When a 0 cycle) test was conducted, no wire breakage occurred in the samples of the example, but wire breakage occurred in 30% of the samples of the comparative example.

In addition, when a standing test was conducted at -70°C for 1 hour, 10 samples of the example had wire breakage.
In the comparative sample, 50% of the wires were broken.

As described above, according to the present invention, peeling, cracking, disconnection, etc. of the conductive connection portion due to heating and cooling becomes less likely to occur.

Example 2 The size of the extended part of the board outside the seal on which the terminal was formed was 105 mm x 5 mm, and the third board was 90 mm.
A sample was manufactured in the same manner as in Example 1, except that glass plates having a size of 5 mm x 0.7 mm and a thickness of 0.7 mm were laminated as shown in FIG.

This sample of Example 3 showed the same effect as Example 1.

[Effects of the Invention] The present invention provides a method for connecting terminals of a conductive film formed on a substrate such as an electro-optical element to terminals of a conductive film on a circuit board through a conductive adhesive. The circuit board at the connection part and the surrounding board are covered with resin, and a third layer is placed on top of it.
By arranging the third substrate and curing the resin, the third substrate and the substrate or circuit board are bonded with the resin.

As a result, even if there is shrinkage due to resin curing or expansion and contraction due to heating and cooling during use, the stress is dispersed between the third substrate and the substrate, and stress due to expansion and contraction is added to this conductive connection part. It becomes difficult to cause defects such as peeling.

That is, in the present invention, this conductive connection portion is connected to the substrate or the third
Since the structure is sandwiched between two substrates, the stress caused by expansion and contraction of the resin is distributed and applied to the substrate on which the terminal is formed and the third substrate, so almost no bending stress is applied to the conductive connection part, making it easier to mount the plating. , peeling of the conductive adhesive and the like is less likely to occur.

Furthermore, even if the conductive connection part is strong enough, the stress is distributed between the board on which the terminal is formed and the third board, so it is approximately twice as strong as when the third board is not used. Can withstand stress up to. For this reason, cracks in the substrate are less likely to occur.

This makes it difficult to cause problems such as peeling of the transparent conductive film and plating layer of the substrate, peeling of the connection portion by the conductive adhesive, cracking of a part of the glass of the substrate, and the resulting disconnection.

In addition to this, the present invention can be applied in various other ways as long as the effects of the present invention are not impaired.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of typical examples of the present invention in which terminals of a liquid crystal display element and terminals of a flexible printed circuit board are electrically connected. Substrate: IA, IB, IIA, 11B Transparent conductive film = 2A, 28.12A, 12B Seal material = 3.13 Liquid crystal substance = 4.14 Terminal = 5.15 Circuit board 2〇, 16 Conductive film: 7.17 Conductive Adhesive = 8.18 Resin = 9.19 Third substrate: 10120 Figure 1 Figure 2 11B 1281413

Claims (3)

[Claims] (1) Seal of an electro-optic element in which an electro-optic medium is sandwiched between a pair of substrates with electrodes and the periphery is sealed. Terminals for connecting to an external drive circuit are formed on the external substrate, and the terminals on the substrate are sealed. In an electro-optical device in which a circuit board is electrically connected with a conductive adhesive, a third board is placed on the terminal portion of the board of the electro-optic element, and the third board and the board of the electro-optic element or the circuit are connected. An electro-optical device characterized in that a resin adhesive layer is formed between the substrate and the substrate. (2) Connect the terminal of the conductive film on the circuit board to the terminal of the conductive film formed on the circuit board by placing a conductive adhesive between the terminals with both terminals facing each other, and By supplying resin onto the substrate or circuit board, placing a third substrate on top of it, and curing the resin, an adhesive layer of resin is formed between the third substrate and the substrate or circuit board. A conductive connection method characterized by forming a conductive connection. (3) As the third substrate according to claim 1 or 2, a substrate made of the same material as the substrate on which the terminals are formed is used.