JP2000008016A - Electro-conductive adhesive and mounting of electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-conductive adhesive that can mount electronic parts without occurrence of defective conduction and a method of mounting electronic parts by using the same. SOLUTION: The electrode 2 of the base plate 1 is coated with an electro- conductive paste 3 that contains an epoxy resin, a curing agent, an electro- conductive material 3a and an activation agent 3b that has an action to remove the oxide films on the surfaces of the electrodes and the electrode 5 of the electronic part is bonded via the electro-conductive paste 3 to the electrode 2. The heat is applied to melt the activation agent to remove the oxide films 2a, 5a on the surfaces of the electrodes 2, 5 whereby the electrode 2 is made electrically conductive through the conductive material 3a to the electrode 5 mutually. Thus, even works and electronic parts having electrodes of which surfaces are poor in their conductivity can be mounted by using the electro- conductive paste without occurrence of the conductive defect. In addition, the adhesive is free from solder and causes no lead pollution, when the parts or the like are disposed after their use.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive for joining an electronic component to a work and electrically connecting the same to a workpiece, and a method for mounting an electronic component using the conductive adhesive.

[0002]

2. Description of the Related Art As a method for mounting an electronic component on a work such as a substrate, a method using a conductive adhesive is known. This conductive adhesive is obtained by adding a good conductor such as silver as a conductive material to an adhesive composed of an epoxy resin and a curing agent. By joining the electrode of the electronic component and the electrode of the work via this conductive adhesive, the conductive material comes into contact with each electrode, and furthermore, the conductive materials are connected in a conductive state in the conductive adhesive. Thus, conduction between the electronic component and the work is ensured.

At this time, a metal oxide film constituting the electrode is generally formed on the surface of the electrode of the substrate or the electronic component. For this reason, in order for the conductive material to be conductive with the electrode, it is necessary that the conductive material partially breaks through the oxide film and the tip of the conductive material contacts the metal part of the electrode.

[0004]

However, in the case of an electronic component surface-mounted on an electrode of a substrate, the surface condition of the electrode for external connection is not always kept in a good condition, and oxidation of the surface progresses, resulting in thick oxidation. A film may have formed. Even in such a case, in the case of mounting by soldering, which has been the mainstream of the conventional mounting method, there is no particular obstacle since the oxide film is removed by the flux applied at the time of soldering.

[0005] However, in the field of certain types of electronic component mounting, for example, where the high reliability after mounting is not so important, the mounting method is changed from the conventional solder bonding method to the conductive adhesive bonding method. There is a tendency to move. This is because, in the method using solder, lead in the solder causes environmental pollution after the board is discarded after the end of its useful life. However, since the flux is not used in the method using the conductive adhesive, there is a problem in that conduction failure at the junction occurs due to the oxide film on the surface of the electrode as described above.

Accordingly, an object of the present invention is to provide a conductive adhesive capable of mounting an electronic component without causing a conduction failure, and a method of mounting an electronic component using the conductive adhesive.

[0007]

According to a first aspect of the present invention, there is provided a conductive adhesive for joining an electrode of an electronic component to an electrode of a work and electrically connecting the electrode to a workpiece. And an activator having a function of removing a conductive film and an oxide film on the electrode surface by being melted by heating.

[0008] The conductive adhesive according to the second aspect is the first aspect.
The conductive adhesive according to the above, wherein a trapping agent for trapping impurities such as halogen is added.

According to a third aspect of the present invention, there is provided the conductive adhesive.
The conductive adhesive according to the above, wherein the conductive material is silver, copper,
It is an alloy containing at least one or at least one of gold, platinum, palladium, nickel, and carbon.

According to a fourth aspect of the present invention, there is provided a method for mounting an electronic component, comprising the steps of: attaching a conductive adhesive containing a curing agent and an activator having a function of removing an oxide film on the surface of an electrode to a work piece to an epoxy resin; Supplying the electrode on the electrode, mounting the electronic component on the work, joining the electrode of the electronic component to the electrode of the work via the conductive adhesive, melting the activator by heating, A step of removing the oxide film on the electrode surface and conducting the electrodes with each other by the conductive material; and a step of curing the epoxy resin and bonding the electronic component to the work.

According to the present invention, an electrode having a poor surface condition can be obtained by reducing and removing an oxide film on an electrode surface of an electronic component or a work using a conductive adhesive containing an activator. It is possible to mount a work or an electronic component using a conductive adhesive without causing conduction failure.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. FIGS. 1A, 1B, and 1C are process explanatory views of a method for mounting an electronic component according to an embodiment of the present invention;
2 (a), 2 (b) and 2 (c) are enlarged cross-sectional views of a joint portion of the electronic component.

In FIG. 1A, an electrode 2 is formed on a substrate 1 by a metal such as copper. An oxide film is formed on the surface of the electrode 2 by being exposed to the air for a long time as described later (see FIG. 2A). And electrode 2
A conductive paste 3 as a conductive adhesive is supplied on the upper side by a method such as application or printing by a dispenser.
In addition, as a method of supplying the conductive paste 3, instead of applying the conductive paste 3, a method of processing the conductive paste 3 into a tape and attaching the conductive tape may be used.

As shown in FIG. 2 (a), the conductive paste 3 is made of an adhesive composed of an epoxy resin as a main material and a curing agent for curing the epoxy resin, and a metal of a good conductor such as silver or copper. Containing a conductive material 3a formed into various shapes such as particles and foils, and an activator 3b such as an organic acid or an amine having an action of removing an oxide film formed on the metal surface by melting by heating, and further trapping The agent was added. The conductive material 3a may be an alloy containing at least one of silver, copper, gold, platinum, palladium, nickel, and carbon.
The trapping agent has a function of trapping impurities such as halogen mixed in the conductive paste 3 and adversely affecting the circuit electrodes after mounting.

The melting temperature of the activator 3b is set to a temperature lower than the heat treatment temperature for curing the epoxy resin, that is, a temperature at which the activator 3b is melted during the heat treatment. Such activators include adipic acid (melting point 153 ° C), salicylic acid (melting point 156 ° C), benzoic acid (melting point 121 ° C), benzylic acid (melting point 150 ° C), and the like. These activators also have the property that when the epoxy resin is cured, it binds to the epoxy resin itself and loses its activity.

Next, as shown in FIG. 1B, the electronic component 4 is mounted on the substrate 1, and the electrodes 5 of the electronic component 4 are joined to the electrodes 2 of the substrate 1 via the conductive paste 3. At this time,
Similarly to the surface of the electrode 2, the electronic component 4
Is exposed to air until the time of mounting, so that the oxide film 5
a and 2a are generated (see FIG. 2A). These oxide films 5a and 2a hinder conduction between the electrode 5 and the electrode 2 as they are.

These oxide films 5a, 2a are brought into contact with conductive paste 3 by bonding electrode 5 and electrode 2, whereby activator 3b contained in conductive paste 3 becomes oxide film 2a. , 5a.

Thereafter, as shown in FIG.
Is sent to a heating step and heated. When the heating temperature exceeds the melting temperature of the activator 3b, the activator 3b in contact with the surfaces of the oxide films 5a and 2a is melted, and the activation action is reduced.
a, 2a. As a result, as shown in FIG. 2B, the oxide films 5a and 2a are removed from the conductive paste 3 (refer to the reduced products of the oxide films 5a and 2a shown by 2b and 5b in the figure), and the electrodes 5a and 5b elapse over time. , 2 are gradually removed in the area in contact with conductive paste 3.

As a result, the conductive material 3 in the conductive paste 3
a directly contacts the surfaces of the electrodes 5 and 2 from which the oxide films 5a and 2a have been removed. The conductive material 3a is made of a conductive paste 3
The electrode 2 and the electrode 5 are electrically connected via the conductive material 3 a in the conductive paste 3 because the particle shape and the content are defined so that the conductive state is maintained by being connected in a state where they are in contact with each other. Conduct. Thereafter, by maintaining a predetermined heating temperature for a predetermined time (eg, 150 ° C., 10 minutes, or 180 ° C., 5 minutes), the epoxy resin in the conductive paste 3 is cured, and the electronic component 4 is attached to the substrate 1. Completely fixed, electronic components 4
Is completed on the substrate 1.

As described above, by including the activator 3b in the conductive paste 3, the oxidation of the electrode surface progresses, and the electronic component 4 on which a thick oxide film is formed can be formed by solder bonding. Instead, a mounting method using a conductive adhesive can be applied. Further, the activator reacts with and bonds to the epoxy resin as the epoxy resin cures. Therefore, since the activator is sealed in the cured epoxy resin after mounting, it is possible to prevent a decrease in reliability due to corrosion of the circuit pattern after the activator is mounted.

In this embodiment, a method of applying the conductive paste 3 to the electrodes 2 of the substrate 1 is used as a method of supplying the conductive paste 3 to the electrodes 2. The conductive paste 3 may be supplied to the electrodes 2 via the electrodes 5 by applying the paste to the electrodes 5 of the component 4 by a method such as transfer.

[0022]

According to the present invention, an oxide film on an electrode surface of an electronic component or a work is removed by using a conductive adhesive containing an activator. For work and electronic components with bad electrodes, mounting using conductive adhesive can be performed without causing conduction failure.Since the mounting method does not use solder, lead contamination after disposal processing It does not become a source of generation.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an explanatory view of a process of a method of mounting an electronic component according to an embodiment of the present invention. FIG. 1B is an explanatory view of a process of a mounting method of an electronic component according to an embodiment of the present invention. Process explanatory diagram of the electronic component mounting method of one embodiment

2A is an enlarged cross-sectional view of a joint of an electronic component according to an embodiment of the present invention. FIG. 2B is an enlarged cross-sectional view of a joint of an electronic component according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a joint portion of the electronic component according to the embodiment.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 electrode 2a oxide film 3 conductive paste 3a conductive material 3b activator 4 electronic component 5 electrode 5a oxide film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Hideki Nagafuku 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 4J040 EC001 HA026 HA066 HA076 HB24 HB27 HC01 JA05 JA09 JB10 KA10 KA16 KA32 NA19 PA18 5E319 BB11 CC61

Claims (4)

[Claims] 1. A conductive adhesive for joining an electrode of an electronic component to an electrode of a work and electrically connecting the electrode to a work, wherein the epoxy resin is melted by a curing agent, a conductive material and heating to oxidize the surface of the electrode. A conductive adhesive comprising: an activator having a function of removing a film. 2. The conductive adhesive according to claim 1, further comprising a trapping agent for trapping impurities such as halogen. 3. The conductive adhesive according to claim 1, wherein said conductive material is an alloy containing at least one of silver, copper, gold, platinum, palladium, nickel, and carbon. Agent. 4. A step of supplying a conductive adhesive containing a curing agent, a conductive material and an activator having an action of removing an oxide film on the surface of an electrode to an epoxy resin onto an electrode of a work, and A step of mounting an electronic component on and bonding the electrode of the electronic component to the electrode of the work via the conductive adhesive, and melting the activator by heating to remove an oxide film on the electrode surface; A method of mounting an electronic component, comprising: a step of electrically connecting the electrodes with a conductive material; and a step of curing the epoxy resin and bonding the electronic component to the work.