JP2005302845A - Electronic parts mounter, manufacturing method thereof, and conductive adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic parts mounter capable of withstanding hierarchical mounting in electronic parts mounters for mounting electronic parts, by using a conductive adhesive. <P>SOLUTION: The electronic parts mounter is provided with wiring electrodes 9, external electrodes 2, 3 of electronic parts, and a conductive adhesive 4 having a resin 7 and a conductive filler 8 as main components and connecting to the wiring electrodes 9 and the external electrodes 2, 3 electrically. The conductive filler 8 has at least two or more kinds of metal. At least some parts of the surfaces of a core layer 6 formed of a first metal are covered with a second metal 5 that is different from the first metal 6. The rate of solution of the first metal 6 to the molten state of the metal forming the outermost layer of the external electrode 2 is made slower than the rate of solution of the second metal 5 to the molten state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electronic component mounting body that is connected using a conductive adhesive, a method for manufacturing the electronic component mounting body, and a conductive adhesive in the field of mounting electronic components on a substrate.

  In recent years, due to environmental problems, the tendency to restrict the use of lead contained in solder has increased, and component mounting technology using lead-free solder has been actively developed.

  As an alternative material for the conventional eutectic solder (63Sn37Pb), lead-free solder such as Sn-Ag-Cu has been developed and already put into practical use.

  However, no metal composition has been developed as an alternative to high-temperature solder (8Sn-2Ag-Pb: melting temperature 285 ° C., etc.) that has been used for secondary and hierarchical mounting, and there is no lead-free technology for high-temperature solder is the current situation. For this reason, problems such as re-melting of lead-free solder used during primary mounting occur during hierarchical mounting (mounting forms that undergo several reflow processes, such as when double-sided mounting or modules are mounted on a mother board). It is coming.

  On the other hand, component mounting technology using a conductive adhesive in which a conductive filler is dispersed in a resin has attracted attention in recent years. Conductive adhesives are often used in the form of pastes or films, and there are many types of conductive fillers such as silver, copper, or gold-plated plastic beads. Moreover, when mounting components, it can be cured at a relatively low temperature of 200 ° C. or lower, and thereafter, when a thermosetting resin is used, there is an advantage that it does not melt even when exposed to high temperatures. .

  However, many of the general-purpose parts that are generally used have Sn plating (or 90Sn10Pb plating, Sn-Bi plating, etc.) applied to the external electrodes, and their melting points are as low as 231 ° C for Sn and 183 ° C for 90Sn10Pb. . Therefore, when the electronic component mounting body in which these components are mounted using a conductive adhesive is further hierarchically mounted, the outermost layer (Sn, etc.) of the external electrode of the component is remelted, and the connection path with the conductive filler May be cut off.

In some cases, this problem is solved by using a high melting point material such as silver, palladium, or nickel for the external electrode of the component so that it is not melted again at the time of hierarchical mounting (for example, see Patent Document 1).
JP 2001-307947 A

  However, since the external electrodes of many parts currently in circulation are Sn or an alloy system containing the same, the method shown in Patent Document 1 has a drawback that usable parts are greatly limited.

  Thus, at present, there is no substitute material for high-temperature solder, and there is a problem that (lead-free) solder used in primary mounting at the time of hierarchical mounting is remelted. In addition, even when a conductive adhesive that does not remelt is used as a component connection material, there is a problem that external electrodes (Sn plating [melting point 232 ° C.], etc.) of the component are remelted, resulting in poor connection.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and includes an electronic component mounting body, a method for manufacturing the electronic component mounting body, and a conductive adhesive that can be hierarchically mounted without an increase in resistance value and can be made lead-free. The purpose is to provide.

In order to solve the above-described problem, the first aspect of the present invention provides:
A wiring electrode;
An external electrode of an electronic component;
It has a resin and a conductive filler as a main component, and includes a conductive adhesive that electrically connects the wiring electrode and the external electrode,
The conductive filler has at least two kinds of metals, and at least a part of the surface of the core layer formed of the first metal is coated with a second metal different from the first metal. And
In the electronic component mounting body, the dissolution rate of the first metal with respect to the molten state of the metal forming the outermost layer of the external electrode is slower than the dissolution rate of the second metal with respect to the molten state.

The second aspect of the present invention
A wiring electrode;
An external electrode of an electronic component;
It has a resin and a conductive filler as a main component, and includes a conductive adhesive that electrically connects the wiring electrode and the external electrode,
The conductive filler includes a first metal forming a core layer and a second metal different from the first metal, and the concentration of the second metal is a central portion of the conductive filler. It is formed to become lower toward
In the electronic component mounting body, the dissolution rate of the first metal with respect to the molten state of the metal forming the outermost layer of the external electrode is slower than the dissolution rate of the second metal with respect to the molten state.

The third aspect of the present invention provides
A wiring electrode;
An external electrode of an electronic component;
It has a resin and a conductive filler as a main component, and includes a conductive adhesive that electrically connects the wiring electrode and the external electrode,
The conductive filler is an alloy formed of a first metal and a second metal different from the first metal,
In the electronic component mounting body, the dissolution rate of the first metal with respect to the molten state of the metal forming the outermost layer of the external electrode is slower than the dissolution rate of the second metal with respect to the molten state.

The fourth invention relates to
The outermost layer of the external electrode of the electronic component contains at least one metal of tin, lead, bismuth, and indium;
The first metal is the electronic component mounting body according to any one of the first to third aspects of the present invention, which includes at least one of nickel, copper, aluminum, palladium, and iron.

The fifth aspect of the present invention relates to
The average thickness of the outermost layer of the external electrode is a thickness that is less than or equal to twice the average particle size of the conductive filler at the portion where the conductive adhesive is in contact with the external electrode. 3. The electronic component mounting body according to any one of 3 of the present invention.

The sixth invention relates to
The average thickness of the outermost layer of the external electrode is equal to or greater than the average thickness of the second metal at the portion where the conductive adhesive is in contact with the external electrode. A component mounting body.

The seventh invention relates to
The average thickness of the outermost layer of the external electrode is a portion where 80% or more of the second metal is contained from the surface of the conductive filler in the portion where the conductive adhesive is in contact with the external electrode. It is the electronic component mounting body of 2nd this invention which is the thickness more than the average thickness of a layer.

The eighth invention relates to
The average thickness of the outermost layer of the external electrode is a thickness equal to or less than twice the average particle diameter of the core layer at a portion where the conductive adhesive is in contact with the external electrode. It is the electronic component mounting body of this invention.

The ninth invention relates to
The conductive adhesive is the electronic component mounting body according to any one of the first to third aspects of the present invention, comprising 65 to 95 wt% of the conductive filler and 5 to 35 wt% of the resin.

The tenth aspect of the present invention is
The conductive filler is the electronic component mounting body according to any one of the first to third aspects of the present invention, wherein the tap density is 4 g / mL or more and the specific surface area is 0.7 m ² / g or less.

The eleventh aspect of the present invention is
The electronic component mounting body according to any one of the first to third aspects of the present invention, wherein a part of the outermost layer of the external electrode forms an alloy layer with a part of the conductive filler.

The twelfth aspect of the present invention is
A part of the outermost layer of the external electrode is an electronic component mounting body according to an eleventh aspect of the present invention, in which an alloy layer is formed with the first metal.

The thirteenth aspect of the present invention is
As the main component, resin,
At least a part of the surface of the core layer formed of the first metal having at least two kinds of metals and including at least one of nickel, copper, aluminum, palladium, and iron is the first A conductive adhesive comprising a conductive filler coated with a second metal different from the metal.

The fourteenth aspect of the present invention is
As the main component, resin,
A first metal containing at least one metal of nickel, copper, aluminum, palladium, iron and forming a core layer; and a second metal different from the first metal, and the second metal It is a conductive adhesive provided with the conductive filler formed so that the density | concentration of this metal may become low toward a center part.

The fifteenth aspect of the present invention is
As the main component, resin,
A first metal including at least one of nickel, copper, aluminum, palladium, and iron, and a second metal different from the first metal, the first metal and the second metal A conductive adhesive comprising a conductive filler in which a metal uniformly forms an alloy.

The sixteenth aspect of the present invention
The resin is a conductive adhesive according to any one of the thirteenth to fifteenth aspects of the present invention, which is in a B-stage state and is formed into a sheet shape.

The seventeenth aspect of the present invention provides
A method for manufacturing an electronic component mounting body according to any one of the first to third aspects of the present invention,
Applying the conductive adhesive on the wiring electrode;
Mounting the electronic component on the conductive adhesive;
It is a manufacturing method of an electronic component mounting body, comprising the step of curing the conductive adhesive and electrically connecting the electronic component and the wiring electrode.

The eighteenth aspect of the present invention is
The electronic component mounting body according to the seventeenth aspect of the present invention, wherein the step of mounting the electronic component includes a step of undergoing a temperature history higher than the melting point of the metal forming the outermost layer of the external electrode. It is a manufacturing method.

  According to the present invention, it is possible to provide an electronic component mounting body, a method for manufacturing an electronic component mounting body, and a conductive adhesive that can be hierarchically mounted without an increase in resistance value and achieve lead-free.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing an electronic component mounting body according to Embodiment 1 of the present invention.

  First, the configuration of the electronic component mounting body according to the first embodiment will be described.

  The external electrode of the chip-type electronic component 1 includes an inner layer 3 and an outermost layer 2. A wiring electrode 9 is disposed on the substrate 10. The outermost layer 2 of the external electrode and the wiring electrode 9 are electrically connected via the conductive adhesive 4 to constitute an electronic component mounting body. The conductive adhesive 4 is composed of a resin 7 and a conductive filler 8.

  The outermost layer 2 of the external electrode contains at least one metal selected from tin, lead, bismuth, and indium, which is a low-melting point metal material that easily causes metal erosion.

  The conductive filler 8 is made of at least two kinds of metals. The core layer 6 is formed of a first metal containing at least one metal selected from nickel, copper, aluminum, palladium, and iron. The entire surface of the core layer 6 or a part of the surface is covered with the second metal as the outermost layer 5. The second metal is a metal different from the first metal, and the dissolution rate of the melted outer electrode with respect to the metal of the outermost layer 2 is slower in the first metal than in the second metal.

  Next, the effect in the structure of the electronic component mounting body of this Embodiment 1 is demonstrated.

  According to the electronic component mounting body having the configuration as shown in FIG. 1, the external electrode of the external electrode can be used even in hierarchical mounting where the outermost layer 2 of the external electrode of the electronic component is melted or in a high-temperature exposure test (such as a 260 ° C. heat reflow test). A connection path at the interface between the outermost layer 2 and the conductive filler 8 is secured, and defects due to an increase in resistance value can be avoided.

  Currently, electronic parts are made of sintered silver or sintered copper as the inner layer of the external electrode, nickel as the intermediate layer, tin, tin / lead (solder) as the outermost layer, bismuth or indium added to these alloys, etc. Are generally commercially available. An electronic component having these external electrodes can be preferably used because it is easily available.

  However, the metal forming the outermost layer of these external electrodes is melted at the time of hierarchical mounting, and when the conductive filler is silver or the like, it melts into the molten metal, so-called silver erosion occurs. Therefore, the connection path is disconnected at the interface between the external electrode and the conductive adhesive.

  On the other hand, in the case of the configuration of the first embodiment shown in FIG. 1, the first metal (metal including nickel, copper, aluminum, palladium, iron) having a slow dissolution rate with respect to the outermost layer 2 of the melted external electrode is the core. Since the layer 6 is formed, only the second metal of the outermost layer 5 is eaten, and the entire conductive filler 8 is not eaten. For this reason, a connection path is secured even when the layers are mounted, so that a failure due to an increase in resistance value can be avoided.

  When nickel, copper, aluminum, or iron alone is used as the conductive filler, since these metals are easily oxidized, an oxide film is formed on the surface of the conductive filler, resulting in very high initial connection resistance. Moreover, since palladium is very expensive, there is a problem in cost when used alone.

  The conductive filler 8 in the first embodiment is a coated powder in which the entire surface of the core layer 6 or a part of the surface is coated with the second metal as the outermost layer 5. Coated powder obtained by coating the metal powder forming the core layer 6 with the second metal by a technique such as plating or vapor deposition can be preferably used. The coated powder has the advantage that it is relatively inexpensive and abundant in types, and the thickness of the outermost layer 5 can be easily controlled.

  As the second metal, a metal that is not easily oxidized and has good conductivity can be preferably used, and examples thereof include noble metals such as gold, silver, platinum, and palladium. Further, tin, lead, bismuth, indium and the like can be preferably used from the viewpoint of wettability with the outermost layer of the melted external electrode.

  Further, components other than the first metal and the second metal may be added to the conductive filler 8. For example, a surface treatment agent may be applied to the surface of the conductive filler 8 to prevent oxidation of the third metal or the conductive filler 8, or a resin ball may be added to improve reliability. That is, the first metal may be formed on the resin ball surface to form the core layer 6, and the surface coated with the second metal may be used as the conductive filler 8.

  Further, the conductive filler 8 may be mixed with other conductive fillers such as a silver filler. In that case, it is preferable that the conductive filler of the component shown in this Embodiment 1 is 60 wt% or more of the whole conductive filler.

  The electronic component in the electronic component mounting body according to the first embodiment is exemplified by the chip-type electronic component 1. However, active components such as transistors, ICs, LSIs, resistors, capacitors, inductors, diodes, thermistors, Including passive components such as switches and connectors, the shape is not particularly limited, such as a chip type or an insertion type.

  In addition, the wiring electrode in the electronic component mounting body according to the first embodiment is exemplified by the substrate electrode 9 formed on the substrate 10, but the through hole formed by plating or the via formed by conductive paste is used. The type is not particularly limited. The material of the wiring electrode is not particularly limited, such as metal or a mixture of metal and resin.

  As the resin in the first embodiment, a thermosetting resin such as an epoxy resin, an acrylic resin, a phenol resin, a silicon resin, a polyimide resin, or a urethane resin, a thermoplastic resin, or a mixture thereof can be used. Epoxy resins can be preferably used because of their low cure shrinkage and excellent adhesion.

  In addition to the resin and the conductive filler, additives such as a solvent, a reactive diluent, a thixotropic agent, a coupling agent, and an antioxidant may be added as the conductive adhesive in the first embodiment.

  Further, the electronic component mounting body shown in the first embodiment may be molded with another resin or the like. Moreover, the method of installing resin only under a component can also be utilized preferably. With these configurations, it is possible to improve reliability, high-density mounting, and the like.

(Embodiment 2)
FIG. 2 is a sectional view showing an electronic component mounting body according to the second embodiment of the present invention. In FIG. 2, the same components as those in FIG.

  The electronic component mounting body according to the second embodiment is different from the first embodiment in the configuration of the conductive filler.

  The conductive adhesive 24 is composed of a resin 7 and a conductive filler 28. The conductive filler 28 is made of at least two kinds of metals. The first metal forming the core layer includes at least one metal selected from nickel, copper, aluminum, palladium, and iron. And it is the inclination powder | flour which the density | concentration of a 2nd metal is gradually lowered toward the center part of the electroconductive filler 28, It is characterized by the above-mentioned. The second metal is a metal different from the first metal, and the dissolution rate of the melted outer electrode with respect to the metal of the outermost layer 2 is slower in the first metal than in the second metal.

  According to the electronic component mounting body configured as shown in FIG. 2, the connection at the interface between the outermost layer 2 of the external electrode and the conductive filler 28 even when the outermost layer 2 of the external electrode of the electronic component 1 is melted. A path is secured, and defects due to an increase in resistance can be avoided. That is, since the concentration of the first metal having a low dissolution rate with respect to the metal of the outermost layer 2 of the melted external electrode is higher toward the central portion of the conductive filler 28, only the second metal is eaten, This is because the entire conductive filler 28 is not eaten. For this reason, a connection path is secured even when the layers are mounted, and a defect due to an increase in resistance value can be avoided.

  Further, because of the inclined powder, only the metal forming the surface of the conductive filler 28 is not selectively eaten, and there is an advantage that it is easy to secure a conductive path.

(Embodiment 3)
FIG. 3 is a cross-sectional view showing an electronic component mounting body according to Embodiment 3 of the present invention. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted.

  The electronic component mounting body of the third embodiment is different from the first and second embodiments in the configuration of the conductive filler.

  The conductive adhesive 34 is composed of a resin 7 and a conductive filler 38. The conductive filler 38 is made of at least two kinds of metals. The first metal contains at least one metal selected from nickel, copper, aluminum, palladium, and iron. The conductive filler 38 is an alloy powder in which the first metal and the second metal uniformly form an alloy. The second metal is a metal different from the first metal, and the dissolution rate of the melted outer electrode with respect to the metal of the outermost layer 2 is slower in the first metal than in the second metal.

  According to the electronic component mounting body having the configuration as shown in FIG. 3, the conductive filler 38 is made of an alloy containing the first metal having a slow dissolution rate with respect to the metal of the outermost layer 2 of the melted external electrode. , It is possible to suppress biting at the time of hierarchical mounting and to avoid defects due to an increase in resistance value.

  In addition, because of the alloy powder, the cost of the conductive filler 38 can be suppressed, and there are advantages that there are many types that can be used.

  In the first to third embodiments, the dissolution rate of the metal forming the outermost layer of the external electrode in the molten state is preferably that the first metal is slower than the second metal. The first metal becomes a barrier layer against the outermost layer of the outer electrode in a molten state, preventing the entire conductive filler from being eaten, and the second metal acts as a bridge between the first metal and the outer electrode. Take a role. This is because the conductive path is secured without being cut.

  In the first to third embodiments, it is preferable that the average thickness of the outermost layer of the external electrode in the portion where the conductive adhesive and the external electrode are in contact is not more than twice the average particle diameter of the conductive filler. More preferably, the average thickness of the outermost layer of the external electrode is not more than the average particle diameter of the conductive filler. This is because the thinner outermost layer of the external electrode reduces the amount of biting of the conductive filler and facilitates securing a conductive path.

  Similarly, when the average particle diameter of the conductive filler is larger, the entire conductive filler is not eaten against the melted external electrode, and a conductive path is easily secured. Whether or not the conductive filler is eroded and the conductive path is cut is determined not only by the dissolution rate of the material (metal species) forming the conductive filler, but also by the relative amount (the particle size of the conductive filler and the external This greatly depends on the relationship of the thickness of the outermost layer of the electrode.

  In the first and second embodiments, it is more preferable that the average thickness of the outermost layer of the external electrode at the portion where the conductive adhesive is in contact with the external electrode is thicker than the average thickness of the second metal. Here, in the inclined powder in Embodiment 2, the portion having 80% or more of the second metal is defined as the average thickness. This is because the thicker the second metal is, the more easily the conductive path is cut by the external electrode. That is, the thicker the second metal, the closer to the characteristics of the conductive filler of the second metal alone.

  In the first and second embodiments, the average thickness of the outermost layer of the external electrode at the portion where the conductive adhesive is in contact with the external electrode is 2 of the average particle diameter of the core layer formed by the first metal. It is preferable that it is less than 2 times. More preferably, the average thickness of the outermost layer of the external electrode is equal to or less than the average particle diameter of the core layer formed by the first metal. This is because, as described above, the thinner the outermost layer of the external electrode is, the less the amount of the conductive filler eroded, and the easier it is to secure a conductive path. Similarly, when the average particle size of the core layer of the conductive filler is larger, the entire core layer is not eaten against the melted external electrode, and a conductive path is easily secured.

  In the first to third embodiments, it is preferable that the conductive adhesive contains 65 to 95 wt% of conductive filler and 5 to 35 wt% of resin. With this formulation, the conductivity required for component mounting can be obtained and the bonding strength can be satisfied without applying a large load when the conductive adhesive is cured.

  When the conductive filler of the conductive adhesive is less than 65 wt%, the filler contact probability is lowered, and thus the connection resistance value is increased unless a load is applied during mounting. Moreover, when the conductive filler of the conductive adhesive exceeds 95 wt%, the resin content decreases, the ability to hold the conductive filler decreases, and the connection resistance value increases. Therefore, by setting the amount of the conductive filler in the range of 65 to 95 wt%, the range can be used as an isotropic conductive adhesive.

In Embodiments 1 to 3, the conductive filler preferably has a tap density of 4 g / mL or more and a specific surface area of 0.7 m ² / g or less. This is because most of the conductive fillers having these characteristics are spherical, and the entire conductive filler is not eaten, and a conductive path is easily secured. On the other hand, flake powder or fine powder having a larger specific surface area is thin, and the volume of the entire conductive filler relative to the area in contact with the external electrode is small, so that the conductive path is easily cut.

Moreover, to the conductive filler 100 wt%, tap density is preferably and specific surface area of more than 4g / mL contains less conductive filler 0.7 m ² / g or more 60 wt%. If it is 60 wt% or more, these conductive fillers have a high contribution rate to the electrical conductivity, so that almost no increase in resistance value is observed in the layer mounting or in the high temperature exposure test.

  In the first to third embodiments, the chip-type electronic component is taken as an example. However, the substrate is considered as the electronic component, and the conductive bonding is applied to the substrate electrode whose outermost layer is plated with Sn or SnPb. The present invention is also effective in the case where other parts are mounted or connected to other wiring electrodes using an agent.

(Embodiment 4)
FIG. 4 is a cross-sectional view showing a connection portion of the electronic component mounting body according to the fourth embodiment of the present invention. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The electronic component mounting body according to the fourth embodiment is characterized in that the outermost layer of the external electrode and the conductive filler form an alloy layer. In FIG. 4, an alloy layer 11 is formed of the outermost layer 2 of the external electrode and the metal of the outermost layer 5 of the conductive filler 8. The alloy layer 11 may be at least part of the outermost layer 2 of the external electrode and the conductive filler 8.

  The alloy layer 11 is preferably an alloy between the metal constituting the outermost layer 2 of the external electrode and the metal constituting the conductive filler 8, and as the outermost layer 2 of the external electrode is approached, the outermost layer of the external electrode A configuration in which the concentration of the metal species constituting 2 is sequentially increased is more preferable. This is because the alloy layer 11 plays a bridging role between the outermost layer 2 of the external electrode and the conductive filler 8, and a conductive path can be secured even during hierarchical mounting or during a high temperature exposure test. Moreover, even when the outermost layer 2 of the external electrode is melted by the alloy layer 11 containing the metal species constituting the conductive filler 8 being present at the connection interface, the biting of the conductive filler 8 can be suppressed. it can.

  FIG. 5 is a cross-sectional view showing a connection portion of another electronic component mounting body according to Embodiment 4 of the present invention. In FIG. 5, the same components as those in FIG.

  The electronic component mounting body of FIG. 5 is characterized in that the first metal constituting the outermost layer 2 of the external electrode and the core layer 6 of the conductive filler forms the alloy layer 12. In the configuration of FIG. 4, the outermost layer 2 of the external electrode forms the alloy layer 11 with the metal of the outermost layer 5 of the conductive filler 8, whereas the metal of the core layer 6 of the conductive filler 8 The difference is that the alloy layer 12 is formed. The alloy layer 12 may be at least a part of the outermost layer 2 of the external electrode and the conductive filler 8.

  The alloy layer 12 is more preferably configured such that the concentration of the metal species constituting the outermost layer 2 of the external electrode increases sequentially as the outermost layer 2 of the outer electrode is approached. This is because the alloy layer 12 serves as a bridge between the outermost layer 2 of the external electrode and the conductive filler 8, and a conductive path can be secured even during hierarchical mounting or during a high temperature exposure test. Moreover, even when the outermost layer 2 of the external electrode is melted by the presence of the alloy layer 12 containing the first metal constituting the core layer 6 of the conductive filler 8 at the connection interface, the conductive filler 8 Can be suppressed.

  The filler 8 of the conductive adhesive 4 for producing the electronic component mounting body of the fourth embodiment shown in FIGS. 4 and 5 is made of at least two kinds of metals. The first metal forming the core layer 6 includes at least one metal selected from nickel, copper, aluminum, palladium, and iron. And what knead | mixed and disperse | distributed the conductive filler 8 in which the 2nd metal was coat | covered to the whole surface of the core layer 6 or a part of surface to the resin 7 can use preferably as a conductive adhesive.

  Similarly, the first metal made of at least two kinds of metals and forming the core layer 6 includes at least one metal selected from nickel, copper, aluminum, palladium and iron, and the concentration of the second metal is A material obtained by kneading and dispersing the conductive filler 8 that is successively lowered toward the center of the conductive filler 8 in the resin 7 can also be preferably used.

  Moreover, it consists of at least two kinds of metals, and includes at least one metal selected from nickel, copper, aluminum, palladium, and iron as the first metal, and the first metal and the second metal are in the conductive filler. Also, it is preferable to use an alloy powder that uniformly forms an alloy as a conductive filler, which is kneaded and dispersed in a resin.

  In addition to the resin and the conductive filler, additives such as a solvent, a reactive diluent, a thixotropic agent, a coupling agent, and an antioxidant may be added to the conductive adhesive.

  As the conductive adhesive, a paste whose viscosity has been adjusted and a resin processed into a B-stage state and processed into a sheet can be preferably used. The sheet form has the advantage that it is easy to handle.

  In addition, the amount of the conductive filler in the conductive adhesive can be reduced and used as an anisotropic conductive paste or an anisotropic conductive film. In this case, when the resin is cured, it is necessary to apply an appropriate amount of pressure to the electronic component. When the conductive filler is 65 to 95 wt% and the resin is 5 to 35 wt%, it can be used as an isotropic conductive adhesive or an isotropic conductive film.

  As described above, by using the electronic component mounting body according to the first to fourth embodiments, even when the external electrode of the electronic component is remelted at the time of hierarchical mounting, a connection path between the conductive filler and the external electrode is provided. The connection resistance can be stabilized without breaking.

(Embodiment 5)
FIG. 6 is a diagram showing a manufacturing process for explaining the method for manufacturing the electronic component mounting body according to the fifth embodiment of the present invention. It shows to Fig.6 (a)-(d) in order of a manufacturing process.

  FIG. 6 shows, as an example, a method for manufacturing the electronic component mounting body according to the first embodiment shown in FIG. In FIG. 6, the same components as those in FIG. The materials used in the fifth embodiment are the same as those in the first embodiment unless otherwise specified.

  First, a substrate 10 on which a wiring electrode 9 is disposed is prepared (a). Then, the conductive adhesive 4 is applied to a predetermined location on the wiring electrode 9 (b). Next, the electronic component 1 is mounted on the conductive adhesive 4 (c). Finally, the conductive adhesive 4 is cured to electrically connect the electronic component 1 and the wiring electrode 9 (d).

  As a method for applying the conductive adhesive 4, metal plate printing, screen printing, a dispenser, a dip method, an ink jet method, or the like can be used. Metal plate printing and a method using a dispenser can be preferably used from the viewpoint that the coating thickness of the conductive adhesive 4 can be sufficiently secured.

  As a method for mounting the electronic component 1 at a predetermined position, a chip mounter can be preferably used.

  As a method of curing and electrically connecting the conductive adhesive 4, when a thermosetting resin is included, it is necessary to raise the curing temperature. And when a thermoplastic resin is included, it is necessary to remove a solvent. It is also possible to cure the resin by light such as ultraviolet rays using a photocurable resin.

  As equipment, a batch furnace or a reflow furnace can be preferably used. A method of applying pressure to the electronic component 1 or the conductive adhesive 4 when the conductive adhesive 4 is cured can be preferably used.

  In the fifth embodiment, the case where a paste-like conductive adhesive is used is described, but a conductive adhesive processed into a sheet may be used.

(Embodiment 6)
FIG. 7 is a diagram showing a manufacturing process for explaining the method for manufacturing the electronic component mounting body according to the sixth embodiment of the present invention. It shows to Fig.7 (a)-(d) in order of a manufacturing process.

  FIG. 7 shows, as an example, a method for manufacturing the electronic component mounting body according to the first embodiment shown in FIG. In FIG. 7, the same components as those in FIG. The materials used in the sixth embodiment are the same as those in the first embodiment unless otherwise specified.

  First, the electronic component 1 is prepared (a). And the conductive adhesive 4 is apply | coated on the external electrode of the electronic component 1 (b). Next, the electronic component 1 is mounted at a predetermined position on the substrate 10 (c). Finally, the conductive adhesive 4 is cured to electrically connect the electronic component 1 and the wiring electrode 9 (d).

(Embodiment 7)
FIG. 8 is a diagram showing a manufacturing process for explaining the method for manufacturing the electronic component mounting body according to the seventh embodiment of the present invention. The manufacturing steps in the order of FIGS. 8A and 8B or FIGS. 8A and 8C are taken.

  FIG. 8 shows, as an example, a method for manufacturing the electronic component mounting body according to the fourth embodiment shown in FIGS. 4 and 5. 8, the same components as those in FIGS. 4 and 5 are denoted by the same reference numerals, and the description thereof is omitted. The materials used in the sixth embodiment are the same as those in the fourth embodiment unless otherwise specified.

  First, the electronic component mounting body 1 manufactured by the method described in the fifth embodiment or the sixth embodiment is prepared (a). Then, by passing a temperature history higher than the melting point of the metal forming the outermost layer 2 of the outer electrode of the electronic component 1, the alloy layer 11 ( Alternatively, the alloy layer 12) is formed ((b) or (c)).

  The temperature and time of the process are controlled according to the type and thickness of the metal constituting the outermost layer 2 of the external electrode, the first metal constituting the conductive filler 8, the second metal, and the particle size thereof. By doing so, the thickness and kind of the alloy layers 11 and 12 can be changed.

  According to the conditions, as shown in FIG. 8C, an alloy layer of the first metal forming the core layer 6 of the conductive filler 8 and the metal forming the outermost layer 2 of the external electrode. 12 can also be formed. Moreover, the method of forming an alloy layer by applying an ultrasonic wave simultaneously with temperature can also be utilized preferably.

  In the seventh embodiment, the electronic component mounting body in which the conductive adhesive is cured is prepared. However, when the conductive adhesive is cured, the melting point of the metal forming the outermost layer of the external electrode is determined. Passing through a high temperature history can also be used preferably.

  As described above, according to the electronic component mounting body, the electronic component mounting body manufacturing method, and the conductive adhesive of the present invention that can withstand hierarchical mounting, the outermost layer of the external electrode is configured by Sn plating. Even when the electronic component is used and mounted with a conductive adhesive, it is possible to prevent an increase in resistance value during hierarchical mounting. In other words, this is a high-temperature solder alternative technology that can achieve lead-free.

  Hereinafter, the present invention will be specifically described based on examples.

  In this example, conductive adhesives having different conductive fillers were prepared, and the electronic component mounting body of Embodiment 1 was produced by the manufacturing method of Embodiment 5.

  In order to determine the resistance value stability in hierarchical mounting of these electronic component mounting bodies, a high-temperature exposure test was conducted, and the resistance value increase rate before and after the test was compared. In the high temperature exposure test, a reflow furnace was used, and the sample was passed through a temperature profile of a lead-free solder specification with a top temperature of 260 ° C .: 10 seconds, 230 ° C. or higher: 30 seconds, and a total time of 6 minutes. The criteria for the high-temperature exposure test were determined to be non-defective when the resistance increase rate before and after the test was less than 50% and defective as 50% or more.

  Unless otherwise noted, experiments were conducted using the materials and components described below.

  A jumper chip resistor (1005 size, 0Ω) was used as the electronic component. The outermost layer of the external electrode was prepared by Sn plating and solder (90Sn10Pb) plating. In both platings, the average thickness of the outermost layer of the external electrode was 3 μm.

  As the substrate, a double-sided plate having Au wiring electrodes (Cu / Ni / Au flash) on both sides of a glass epoxy substrate (0.4 mm thickness, 100 mm square) was used.

  As a conductive adhesive, a conductive filler (85 wt%) and an epoxy resin (15 wt%) are kneaded, and a solvent (butyl carbitol acetate, 2 wt% or less) is added for viscosity adjustment as necessary. Using. In this example, all conductive adhesives were in paste form.

(Example 1)
Samples were prepared using conductive adhesives prepared by preparing conductive fillers of different metal species. A conductive filler having an average particle diameter of 6 μm was used. The resistance value change of these samples before and after the high temperature exposure test was measured.

(Comparative Example 1)
A coating powder, a gradient powder, and an alloy powder made of a combination of metals having a high dissolution rate such as Sn, Au, and Ag were prepared, and a sample was prepared using a conductive adhesive prepared using these as a conductive filler. A conductive filler having an average particle diameter of 6 μm was used. The resistance value change of these samples before and after the high temperature exposure test was measured.

(Comparative Example 2)
As a single powder, metal powders of Ag, Sn, Cu, Ni, Al, and Fe were prepared, and a sample was prepared using a conductive adhesive prepared using these as conductive fillers. A conductive filler having an average particle diameter of 6 μm was used. The resistance value change of these samples before and after the high temperature exposure test was measured.

  Table 1 shows the results of performing the high-temperature exposure test for Example 1 and Comparative Examples 1 and 2.

  From Table 1, when the coated powder having any of Cu, Ni, Pd, Al, and Fe is used as the conductive filler in the core layer, the resistance value increase rate is suppressed within 20%, which is good. I understand that. Similarly, it can be seen that the increase rate of the resistance value is within 50% before and after the high-temperature exposure test even when tilted powder or alloy powder is used. The same tendency was shown when the outermost layer of the external electrode of the electronic component was changed to SnPb.

  On the other hand, as a comparative example, in the case of a conductive adhesive (Comparative Example 1) using a conductive filler made of a combination of metals having a high dissolution rate such as Sn, Au, and Ag, the resistance value greatly increased after the high-temperature exposure test. In the case of a conductive adhesive using a single powder conductive filler (Comparative Example 2), even when Ag powder or Cu powder was used, the resistance value greatly increased after the high-temperature exposure test.

  Moreover, when Sn powder, Ni powder, Al powder, and Fe powder were used as a single substance, the initial resistance value was large, and it was judged as an initial failure.

(Example 2)
The average particle size of the conductive filler, the average particle size of the core layer, and the like were examined. Ag-coated Cu powder was prepared as a conductive filler, the average particle size and the average particle size of the core layer were changed, and a sample was prepared using the produced conductive adhesive. The average thickness of the outermost layer of the external electrode of the electronic component was 3 μm. The resistance value change of these samples before and after the high temperature exposure test was measured.

  Table 2 shows the measurement results.

  When the average particle size of the conductive filler was 1.5 μm or more, the rate of increase in resistance value after the high-temperature exposure test was stable at 20% or less. From this result, it is understood that it is effective for improving the reliability that the thickness of the outermost layer of the external electrode is not more than twice the average particle diameter of the conductive filler.

  Further, in the conductive filler having an average particle size of 1.8 μm, the average increase in the resistance value of the core layer having an average particle size of 1.5 μm is lower than that of the core layer having an average particle size of 1.0 μm. It can be seen that it is effective for improving the reliability that the average particle diameter of the core layer formed is not more than twice.

  Further, in the conductive filler having an average particle size of 10 μm, the rate of increase in resistance value is higher in the coating layer thickness of 4 μm than in the coating layer thickness of 3 μm, and the coating layer thickness is the outermost layer of the external electrode. It can be seen that the following thickness is effective. If the thickness of the coat layer is thicker than the outermost layer of the external electrode, the effect of the first metal forming the coat layer is reduced, and only the coat layer is eaten by the metal forming the outermost layer of the external electrode. Conceivable.

(Example 3)
The conductive filler of inclined powder was examined. As the tilted powder, the average thickness (part having 80% or more) of the Ag concentration of the second metal in the Ag tilted Cu powder (the core layer is Cu and the concentration of Ag increases as it approaches the surface of the conductive filler). What was changed was prepared and the sample was produced using the produced conductive adhesive. The average thickness of the outermost layer of the external electrode of the electronic component was 3 μm. The resistance value change of these samples before and after the high temperature exposure test was measured.

  Table 3 shows the measurement results.

  When the average thickness of the concentration of Ag as the second metal was 2 μm or less, there was almost no increase in resistance value after the high-temperature exposure test, and the connection resistance value was stable. On the other hand, when the average thickness of the Ag concentration was 3.2 μm, the resistance value after the high-temperature exposure test was 20% or less, but increased slightly. From this result, it can be seen that it is more effective for the reliability improvement that the average thickness of the second metal is thinner than the outermost layer of the external electrode in the inclined powder.

Example 4
The tap density and specific surface area of the conductive filler were examined. AgCu alloy powder was prepared as a conductive filler, and the tap density and specific surface area were changed to produce a conductive adhesive. A sample was prepared using this conductive adhesive, and the resistance value change before and after the high temperature exposure test was measured.

  Table 4 shows the measurement results.

Table 4 shows that when a conductive filler having a tap density of 4 g / mL or more and a specific surface area of 0.7 m ² / g or less is used, the rate of increase in resistance after the high-temperature exposure test is low, which is effective.

(Example 5)
In Example 5, the effect of the outermost layer of the external electrode and the conductive filler forming an alloy layer was verified.

  As the electronic component, an outer electrode with an outermost layer plated with Sn was used. As the conductive filler, Ag-coated Cu powder (average particle size 1.8 μm, Ag-coated thickness 0.8 μm, Cu core layer 1 μm) was used to produce a conductive adhesive.

  A sample was produced by the method of Embodiment 7 using this conductive adhesive. That is, a sample was manufactured by passing the electronic component mounting body manufactured by the method of Embodiment 1 through a history of 230 ° C. or more and 10 seconds.

  A cross section of the fabricated sample was observed, and it was confirmed that an Ag coat portion of the conductive filler and Sn, which is the outermost layer of the external electrode, formed an alloy. The resistance value change of this sample before and after the high-temperature exposure test was measured.

(Example 6)
In Example 6, the effect of the outermost layer of the external electrode and the core layer of the conductive filler forming an alloy layer was verified.

  The materials used are the same as in Example 5. The sample production method is substantially the same as that of Example 5. The sample of Example 6 was produced by passing the produced electronic component mounting body through a history of 230 ° C. or more and 120 seconds.

  A cross section of the fabricated sample was observed, and it was confirmed that Cu as the core layer of the conductive filler and Sn as the outermost layer of the external electrode formed an alloy. The resistance value change of this sample before and after the high-temperature exposure test was measured.

  Table 5 shows the results of performing the high-temperature exposure test for Examples 2, 5, and 6.

  Comparing the samples of Example 5 and Example 6 in which the alloy layer was formed with the sample of Example 2 in which the alloy layer was not formed, as is apparent from Table 5, the samples in which the alloy layer was formed It can be seen that the rate of increase in resistance after the high-temperature exposure test is lower and is more effective for hierarchical mounting.

  An electronic component mounting body according to the present invention is an electronic component mounting body in which an external electrode and a wiring electrode of an electronic component are electrically connected via a conductive adhesive composed of a resin and a conductive filler as main components. The outermost layer of the external electrode contains at least one metal selected from tin, lead, bismuth, and indium, and the conductive filler is made of at least two kinds of metals as a first metal forming the core layer. It contains at least one metal selected from nickel, copper, aluminum, palladium, and iron, and the second metal is coated on at least a part of the surface of the core layer. The electronic component mounting body manufactured with this configuration can stabilize the connection resistance even during hierarchical mounting. In other words, this is a high-temperature solder alternative technology that can achieve lead-free.

Sectional drawing of the electronic component mounting body in Embodiment 1 of this invention Sectional drawing of the electronic component mounting body in Embodiment 2 of this invention Sectional drawing of the electronic component mounting body in Embodiment 3 of this invention Sectional drawing of the electronic component mounting body in Embodiment 4 of this invention Sectional drawing of the other electronic component mounting body in Embodiment 4 of this invention (A)-(d) The figure which shows the manufacturing process of the electronic component mounting body in Embodiment 5 of this invention. (A)-(d) The figure which shows the manufacturing process of the electronic component mounting body in Embodiment 6 of this invention. (A)-(c) The figure which shows the manufacturing process of the electronic component mounting body in Embodiment 7 of this invention.

Explanation of symbols

1 Electronic component 2 External electrode (outermost layer)
3 External electrode (inner layer)
4, 24, 34 Conductive adhesive 5 Outermost layer of conductive filler 6 Core layer of conductive filler 7 Resin 8, 28, 38 Conductive filler 9 Wiring electrode 10 Substrate 11, 12 Alloy layer

Claims (18)

A wiring electrode;
External electrodes of electronic components,
It has a resin and a conductive filler as a main component, and includes a conductive adhesive that electrically connects the wiring electrode and the external electrode,
The conductive filler has at least two kinds of metals, and at least a part of the surface of the core layer formed of the first metal is coated with a second metal different from the first metal. And
The electronic component mounting body, wherein the dissolution rate of the first metal in the molten state of the metal forming the outermost layer of the external electrode is slower than the dissolution rate of the second metal in the molten state. A wiring electrode;
An external electrode of an electronic component;
It has a resin and a conductive filler as a main component, and includes a conductive adhesive that electrically connects the wiring electrode and the external electrode,
The conductive filler includes a first metal forming a core layer and a second metal different from the first metal, and the concentration of the second metal is a central portion of the conductive filler. It is formed to become lower toward
The electronic component mounting body, wherein the dissolution rate of the first metal in the molten state of the metal forming the outermost layer of the external electrode is slower than the dissolution rate of the second metal in the molten state. A wiring electrode;
An external electrode of an electronic component;
It has a resin and a conductive filler as a main component, and includes a conductive adhesive that electrically connects the wiring electrode and the external electrode,
The conductive filler is an alloy formed of a first metal and a second metal different from the first metal,
The electronic component mounting body, wherein the dissolution rate of the first metal in the molten state of the metal forming the outermost layer of the external electrode is slower than the dissolution rate of the second metal in the molten state. The outermost layer of the external electrode of the electronic component contains at least one metal of tin, lead, bismuth, and indium;
The electronic component mounting body according to any one of claims 1 to 3, wherein the first metal includes at least one of nickel, copper, aluminum, palladium, and iron.   The average thickness of the outermost layer of the external electrode is not more than twice the average particle diameter of the conductive filler at a portion where the conductive adhesive is in contact with the external electrode. The electronic component mounting body according to any one of 3 above.   2. The electron according to claim 1, wherein an average thickness of the outermost layer of the external electrode is equal to or greater than an average thickness of the second metal at a portion where the conductive adhesive is in contact with the external electrode. Component mounting body.   The average thickness of the outermost layer of the external electrode is a portion where 80% or more of the second metal is contained from the surface of the conductive filler in the portion where the conductive adhesive is in contact with the external electrode. The electronic component mounting body according to claim 2, wherein the electronic component mounting body has a thickness equal to or greater than an average thickness of the layers.   The average thickness of the outermost layer of the external electrode is not more than twice the average particle diameter of the core layer at a portion where the conductive adhesive is in contact with the external electrode. The electronic component mounting body described in 1.   The electronic component mounting body according to any one of claims 1 to 3, wherein the conductive adhesive has 65 to 95 wt% of the conductive filler and 5 to 35 wt% of the resin. 4. The electronic component mounting body according to claim 1, wherein the conductive filler has a tap density of 4 g / mL or more and a specific surface area of 0.7 m ² / g or less.   The electronic component mounting body according to claim 1, wherein a part of the outermost layer of the external electrode forms an alloy layer with a part of the conductive filler.   The electronic component mounting body according to claim 11, wherein a part of the outermost layer of the external electrode forms an alloy layer with the first metal. As the main component, resin,
At least a part of the surface of the core layer formed of the first metal having at least two kinds of metals and including at least one of nickel, copper, aluminum, palladium, and iron is the first A conductive adhesive comprising a conductive filler coated with a second metal different from the metal. As the main component, resin,
A first metal containing at least one metal of nickel, copper, aluminum, palladium, iron and forming a core layer; and a second metal different from the first metal, and the second metal A conductive adhesive comprising: a conductive filler formed so that the concentration of the metal decreases toward the center. As the main component, resin,
A first metal including at least one of nickel, copper, aluminum, palladium, and iron, and a second metal different from the first metal, the first metal and the second metal A conductive adhesive comprising a conductive filler in which a metal uniformly forms an alloy.   The conductive adhesive according to claim 13, wherein the resin is in a B-stage state and is formed into a sheet shape. It is a manufacturing method of the electronic component mounting object according to any one of claims 1 to 3,
Applying the conductive adhesive on the wiring electrode;
Mounting the electronic component on the conductive adhesive;
The manufacturing method of an electronic component mounting body provided with the process of hardening the said conductive adhesive and electrically connecting the said electronic component and the said wiring electrode. The electronic component mounting body according to claim 17, wherein the step of mounting the electronic component includes a step of undergoing a temperature history higher than a melting point of the metal forming the outermost layer of the external electrode. Manufacturing method.

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