JPS63308880A - Anisotropic conductive adhesive - Google Patents

Abstract

PURPOSE:To stabilize the connection between patterns and improve the reliability of electrical conductivity by specifying the grain size of conductive grains contained in a conductive adhesive. CONSTITUTION:The grain size of conductive grains contained in a conductive adhesive is set to 1-5 times as large as the thickness of a high-resistance layer formed on the surface of the first conductive pattern. The conductive grains are contained at the range of 1-50wt.% in the conductive adhesive. The conductive grains have the specific resistance of 10<-6>OMEGAcm or less, the Vickers hardness of 50 or more, and a rugged grain shape.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is useful for electrically connecting fine-pinch conductive patterns and mechanically connecting wiring boards on which these conductive patterns are arranged. The present invention relates to a suitable anisotropic conductive adhesive.

(Summary of the Invention) The present invention is an anisotropic conductive adhesive that electrically connects fine-pitch conductive patterns having a high resistance layer on the surface and mechanically connects wiring boards on which these conductive patterns are arranged. In the body, by dispersing conductive particles having a particle size larger than the thickness of the high resistance layer in the insulating adhesive constituting the anisotropic conductive adhesive, stable connection between patterns is possible. The present invention aims to provide an anisotropic conductive adhesive that can achieve electrical conduction with excellent reliability.

[Conventional technology]

Conventionally, electrical connections were made by overlapping conductive patterns to maintain continuity, and when wiring boards on which these conductive patterns were arranged were to be mechanically connected to each other, conductive layers and insulating layers were sequentially laminated. A zebra connector, an anisotropic conductive film with fibrous conductors oriented in a predetermined direction, or a conductive adhesive patterned in stripes was used. When these connection materials are used, the conductivity between corresponding conductive patterns and the insulation between adjacent conductive patterns are almost satisfied as long as the conductive patterns are normal conductive patterns (conductive patterns with a pitch of several millimeters). It was something that However, like connecting ultra-small printed circuit boards,
When considering connections between conductive patterns with a fine pitch (a pitch of about 0.3 to 0.4 fi), it is difficult to ensure insulation between adjacent conductive patterns, and there are few applications.

Therefore, it has been proposed to connect conductive patterns using an anisotropic conductive adhesive in which conductive powder of metal or the like is dispersed in an insulating adhesive. The conductive powder dispersed in the above-mentioned insulating adhesive is extremely fine so that it can correspond to fine pitch patterns, and the conductive powder is crushed between the conductive patterns to achieve electrical conduction. I have to. When conductive patterns are connected to each other using an anisotropic conductive adhesive in which conductive powder or the like is dispersed, it is easy to apply it to fine-pitch conductive patterns because the conductive powder is extremely fine. became.

By the way, the surface of the metal conductive pattern of the wiring board connected using various conductive films as described above is exposed, and the surface of the metal conductive pattern is easily oxidized and there is a possibility that rust or the like may occur. If rust occurs on the surface of the metal conductive pattern of the wiring board, even if the conductive patterns are connected with a conductive film in between, there is a risk that a sufficient connection will not be made, resulting in poor continuity. . Therefore, it has been proposed to form a high resistance layer for preventing oxidation, such as a carbon layer pattern, on the metal conductive pattern.

[Problem that the invention seeks to solve]

However, as mentioned above, the conductive particles dispersed in the anisotropic conductive adhesive have a very fine particle size, so even if you try to connect the metal conductive patterns by pressure bonding, the conductive particles will not touch the metal conductive patterns. The presence of the carbon layer pattern formed on the substrate makes it extremely difficult to connect directly to the metal conductive pattern. That is, for example, when a substrate on which a carbon layer pattern is formed on a metal conductive pattern and a substrate on which a metal conductive pattern is formed are connected using an anisotropic conductive adhesive in which extremely fine conductive particles are dispersed, The conductive particles in the anisotropic conductive adhesive do not penetrate the carbon layer pattern, and these metal conductive patterns are connected via the carbon layer pattern. As a result, since the carbon layer pattern is a high-resistance layer as described above, the conduction resistance between these metal conductive patterns becomes high, making it impossible to achieve stable conduction.

Furthermore, even if there are conductive particles that break through the carbon layer pattern and reach the metal conductive pattern, 8i
+ There were various problems such as conduction lacking in reliability because it was only a small amount and conduction was to be achieved only in that part.

Therefore, the present invention was proposed to solve the above-mentioned problems, and enables stable connection between conductive patterns.
An object of the present invention is to provide an anisotropic conductive adhesive that can achieve electrical continuity with excellent reliability.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned purpose, the present inventors have found that by setting the particle diameter and content of conductive particles contained in the conductive adhesive within a predetermined range, metal patterns can be It was found that the connection can be made well. The present invention was proposed based on the above-mentioned knowledge, and is made by dispersing conductive particles in an insulating adhesive, and corresponds to a first conductive pattern having a high resistance layer on the surface and the first conductive pattern. electrically connecting the second conductive pattern, and mechanically connecting the first wiring board on which the first conductive pattern is arranged and the second wiring board on which the second conductive pattern is arranged. In the anisotropic conductive adhesive connected to
The conductive particles are characterized in that they have a particle diameter that is 1 to 5 times the thickness of the high-resistance layer formed on the surface of the first conductive pattern.

As the conductive particles constituting the conductive adhesive, molten metal powder, carbon fiber, metal powder, etc. can be used, and those satisfying predetermined conditions may be appropriately selected and used.

Moreover, it is preferable that the particle diameter of the conductive particles is 1 to 5 times the thickness of the high-resistance layer formed on the surface of the conductive pattern. If the particle size of the conductive particles is smaller than the thickness of the high-resistance layer, it is difficult to easily and reliably penetrate the high-resistance layer when the conductive pattern is crimped and connected, making it impossible to ensure the reliability of the connection. . In addition, if the particle diameter of the conductive particles is 5 times or more larger than the thickness of the high resistance layer,
This is because there is a possibility that the conductive pattern may connect with an adjacent conductive pattern and cause a short circuit. The particle size of the conductive particles may be satisfied as a single particle, or may satisfy a predetermined particle size in a state where small-diameter particles are aggregated by secondary aggregation or the like. .

In addition, the particle diameter of the conductive particles is 1/ of the distance between the conductive patterns.
It is preferably 3 or less. As mentioned above, the conductive particles connect with adjacent conductive patterns,
This is to prevent the possibility of short circuits occurring.

Furthermore, it is preferable that the conductive particles be contained in the conductive adhesive in an amount of 1 to 50% by weight. As mentioned above, the conductive particles contained in the conductive adhesive according to the present invention are
This is because, since they are relatively large particles, if they are contained in a large amount in an adhesive, there is a risk that the conductive particles will connect with each other and conduction will occur between adjacent conductive patterns.

Furthermore, the conductive particles contained in the conductive adhesive have a specific resistance of 10-'Ω1 or less and a Vickers hardness of 50
As mentioned above, it is preferable that the particle shape has many irregularities.If the specific resistance is 10-hΩcm or more, there is a risk that the conductivity between the conductive patterns may be poor due to the resistance of the conductive particles themselves. In addition, conductive particles with a Vickers hardness of 50 or less and without irregularities cannot easily penetrate the high resistance layer provided as an oxidation prevention layer, making it impossible to connect conductive patterns well. It is from.

On the other hand, as an insulating adhesive that constitutes a conductive adhesive,
Ordinary adhesives can be used, and can be appropriately selected and used so as to have predetermined properties.

[Effect]

As shown in FIG. 1, conductive particles (7) having a particle size larger than the thickness of the high-resistance layer (5) formed on the first conductive pattern (3) in the insulating adhesive (8) When the first conductive pattern (3) having the high resistance layer (5) and the second conductive pattern (4) are bonded together via the anisotropic conductive adhesive (6) in which the conductive particles are dispersed, the conductive particles (7) breaks through the high resistance N(5) and conductive patterns (3), (
4) Being crushed between. Therefore, the first conductive pattern (3) and the second conductive pattern (4) are directly electrically connected by the conductive particles (7), and the distance between the conductive patterns (3) and (4) is A stable connection is possible.

Furthermore, by limiting the particle diameter of the conductive particles (7) to 1/3 or less of the distance between the conductive patterns, these conductive particles (7) do not straddle and contact between adjacent conductive patterns. Short circuits between the conductive patterns can be prevented, and electrical continuity with excellent reliability can be achieved.

〔Example〕

Experimental examples of the present invention will be described below with reference to the drawings.

Ni powder (Inconisokel, type 123) classified to 20 to 32 μm was added to 20 μm in a thermosetting epoxy binder.
After adding phr (20 parts by weight to 100 parts by weight of resin, the same applies hereinafter) and stirring, a sample anisotropic conductive adhesive was prepared by forming a film to have a thickness of 35 μm after drying.

In addition, Ni powder (Inco Nickel, type 123) classified into 5 to 10 μm was added to the epoxy thermosetting binder.
After adding Qphr and stirring, a sample anisotropic conductive adhesive was prepared by forming a film to have a thickness of 35 μm after drying.

A wiring board was bonded using the sample anisotropic conductive adhesive produced as described above.

As shown in Figure 1, a 38 μm thick polyethylene terephthalate (PET) film is formed with a 9 μm thick aluminum pattern (3) with a 0.5 μm pinch and a 15 μm thick carbon layer pattern (5) formed on top of the aluminum pattern (3). A first wiring board (1) and a 38 μm thick PET film on which a 0.5 μm pitch copper pattern (4) are formed.
17 through the sample anisotropically conductive adhesive (6) produced as described above.
Crimp connection was carried out under the conditions of 0° C. and 30 kg Ic for 8.15 seconds.

Similarly, a 3 μm thick copper pattern (3
) and a carbon layer pattern with a thickness of 18 μm (5
) is formed on a 38 μm thick PET film (1), and a 0.5 μm pinch copper pattern (4) is formed on a 38 μm thick PET film (2nd wiring board). (2) and the sample anisotropically conductive adhesive (6) produced as described above at 170°C.
,30KgIcl11! The crimping connection was made for 15 seconds.

Regarding these, initial state, after 250 hours aging,
After aging for 500 hours and after aging for 1000 hours, a continuity resistance test was conducted to measure the crimping reliability. The results are shown in Tables 1 and 2.

Table 1 (blank below) Table 2 shows that when the Ni powder used was larger than the thickness of the carbon layer pattern, stable conduction resistance was exhibited even after aging. On the other hand, in the case where the Ni powder was smaller than the thickness of the carbon layer pattern, defects occurred after aging for 500 hours or more. Furthermore, when the Ni powder is smaller than the thickness of the carbon layer pattern, the conduction resistance is much larger than when the Ni powder is larger than the thickness of the carbon layer pattern even in the initial state or after 250 hours of aging. It is.

20 μm of N1 powder (Inconisokel, type 123) classified into 20-32 μm in a large epoxy thermosetting binder.
After adding phr and stirring, a sample anisotropic conductive adhesive was prepared by forming it into a film so that the thickness after drying was 35 μm.

A wiring board was bonded using the sample anisotropic conductive adhesive produced as described above.

As shown in Figure 1, there is a 9 μm thick aluminum pattern (3) with a 0.5 μm pitch and a 5 μm thick
A first wiring board (1) made of a PET film with a thickness of 38 μm on which a carbon layer pattern (5) with a thickness of 5 μm, 30 μm, and 40 μm was formed, and a copper pattern (4) with a pitch of 0.5 μm. A second wiring board (2) made of a PET film with a diameter of 38 μm is connected to the sample anisotropically conductive adhesive (6) produced as described above.
Crimp connection was performed under the conditions of 70° C., 30 KgIcm”, and 15 seconds.

Regarding these, initial state, after 250 hours aging,
After aging for 500 hours and after aging for 1000 hours, a continuity resistance test was conducted to measure the crimp chain properties. The results are shown in Tables 3 and 4.

As is clear from Tables 3 and 4, the size of the Ni powder is small (if not larger than the thickness of the carbon layer pattern, the conduction resistance will decrease as the aging time progresses). to degrade.

20p of Ni powder (Inco Nickel, type 123) classified into 5-10 μm in Daorou Charcoal epoxy thermosetting binder
After adding and stirring for hr, a sample anisotropic conductive adhesive was prepared by forming it into a film so that the thickness after drying was 35 μm.

A wiring board was bonded using the sample anisotropic conductive adhesive produced as described above.

As shown in Figure 1, there is a 9 μm thick aluminum pattern (3) with a 0.5 μm pitch and a 5 μm thick aluminum pattern (3) on top of it.
A first wiring board (1) made of a PET film with a thickness of 38 μm on which a carbon layer pattern (5) of varying thickness of 15 μm was formed, and a PET film with a thickness of 38 μm on which a copper pattern (4) with a pitch of 0.5 μm was formed. A second wiring board (2) consisting of a film was connected to the sample anisotropically conductive adhesive (6) produced as described above at 170°C and 30 kg/kg.
C++”, crimped and connected for 15 seconds.

Continuity resistance tests were conducted on these in the initial state and after aging for 1000 hours to measure the crimped body rollability. The results are shown in Table 5.

Table 5 From Table 5, unless the size of the Ni powder is at least larger than the thickness of the carbon layer pattern, the conduction resistance deteriorates as the aging time progresses.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since the particle size of the conductive particles contained in the conductive adhesive is larger than the thickness of the high-resistance layer, the conductive particles easily connect the high-resistance layer when connecting conductive patterns by pressure. It is possible to provide an anisotropic conductive adhesive that can be directly connected to a conductive pattern by piercing through it, making stable connection between patterns possible, and achieving electrical continuity with excellent reliability.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a main part schematically showing a state in which conductive patterns are connected to each other using an anisotropic conductive adhesive to which the present invention is applied. ■...First wiring board 2...Second wiring board 3...First conductive pattern 4...Second conductive pattern 5...'High resistance layer 6...Anisotropic Conductive adhesive 7... Conductive particles 8... Insulating adhesive

Claims (1)

[Claims] Electrically connecting a first conductive pattern formed by dispersing conductive particles in an insulating adhesive and having a high resistance layer on the surface and a second conductive pattern corresponding to the first conductive pattern, In an anisotropic conductive adhesive that mechanically connects a first wiring board on which the first conductive pattern is disposed and a second wiring board on which the second conductive pattern is disposed, the conductive particles An anisotropic conductive adhesive having a particle diameter that is 1 to 5 times the thickness of the high-resistance layer formed on the surface of the first conductive pattern.