JP2002150838A - Conductive adhesives, and mounted structure using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive adhesives and a mounted structure using the same which maintain a moisture resistant reliability even when an ordinary base metal electrode is used. SOLUTION: The conductive adhesives contains the first particle of which a standard electrode potential is higher than the standard electrode potential of silver, and the second particle of which a standard electrode potential is lower than the standard electric potential of silver. On the surface of the electrode with a potential lower than the potential of metal particle, which is the first particle, a metal compound film, with a potential higher than the potential of the metal particle, may be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive used in the field of mounting electronic components, and furthermore, a mounting structure in which a substrate and an electronic component are electrically connected using the conductive adhesive. It is about the body.

[0002]

2. Description of the Related Art In recent years, in the field of electronic packaging, restrictions on lead in solder alloys have been regulated due to increasing awareness of environmental harmony, and lead-free packaging technology, that is, electronic materials using lead-free materials, has been developed. There is an urgent need to establish a technology for joining parts. Lead-free mounting technology mainly includes mounting technology using lead-free solder and a conductive adhesive.However, conductive adhesives that are expected to have advantages such as flexibility of joints and lower mounting temperature are used. More attention is starting to come.

[0003] The conductive adhesive is generally obtained by dispersing conductive particles in a resin-based adhesive component (binder resin). The mounting of the component is usually performed by applying a conductive adhesive to the electrodes of the substrate, mounting the component, and then curing the resin. In this way, the joint is bonded with the resin, and the conductive particles come into contact with each other due to the shrinkage of the resin, so that the conduction of the connection is ensured. Since the curing temperature of the resin of the conductive adhesive is about 150 ° C., which is lower than the melting temperature of the solder of about 240 ° C., it can be used for inexpensive parts having low heat resistance. In addition, since the joint is bonded with a resin, it can flexibly follow deformation due to heat or external force. For this reason, there is an advantage that a crack is less likely to be generated in the joint as compared with solder in which the joint is an alloy. For the above reasons, conductive adhesives are expected as a substitute for solder.

[0004]

However, conductive adhesives are inferior to solder alloys in terms of mounting reliability in a state where general-purpose electrode parts and substrates are joined. Generally, a base metal such as a solder alloy or Cu is used as a terminal electrode of an electronic component or a circuit board. When an electronic component or a circuit board having a base metal terminal electrode is mounted using a conductive adhesive, the connection resistance is significantly increased in a high-temperature and high-humidity atmosphere. The increase in connection resistance in the mounting structure using the conductive adhesive is mainly caused by the base metal used for the electrode being corroded in the presence of moisture. That is, the metal particles such as silver used for the conductive adhesive and the moisture penetrating into the base metal electrode come into contact with each other to form a kind of battery, and the base metal electrode having a relatively low potential is corroded. For this reason, in order to secure moisture resistance reliability using a conductive adhesive, it was necessary to use expensive electrodes such as Au and Pd instead of general-purpose electrodes.

Accordingly, an object of the present invention is to provide a conductive adhesive and a mounting structure capable of maintaining moisture resistance reliability even when a general-purpose base metal electrode is used.

[0006]

Means for Solving the Problems The conductive adhesive of the present invention is used for electrically connecting an electronic component and a substrate, and the first particles whose standard electrode potential is higher than the standard electrode potential of silver. And second particles having a standard electrode potential lower than the standard electrode potential of silver.

In this conductive adhesive, by adding the second particles having a low potential, the second particles are sacrificed and corroded, so that the corrosion of the electrodes of electronic components and substrates is suppressed.

The present invention also provides a mounting structure in which electrodes of an electronic component and electrodes of a substrate are electrically connected by using the above-mentioned conductive adhesive. In this mounting structure, the second particles may corrode and exist as at least one compound selected from oxides, hydroxides, chlorides, and carbonates.

Further, according to the present invention, the electrode of the electronic component and the electrode of the substrate are electrically connected using a conductive adhesive, and the conductive adhesive has a standard electrode potential higher than that of silver. Contains a certain particle, at least one electrode selected from the electrodes of the electronic component and the electrode of the substrate, the standard electrode potential on the surface of the electrode lower than the particles, the standard electrode potential is higher than the standard electrode potential of the particles A mounting structure provided with a high metal compound coating is also provided.

In this mounting structure, a metal compound film having a high potential is formed on the surface of an electrode having a low potential,
Electrode corrosion was suppressed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

In the present invention, in order to achieve the above object,
As a first technique, metal particles such as silver which are added for ensuring conductivity are used as first particles, and second particles having a standard electrode potential lower than that of the first particles are added to the conductive adhesive. It was decided to. In addition, as a second technique, a standard electrode potential of an electrode of an electronic component and / or a circuit board is increased by performing a surface treatment on the electrode.

First, the first method will be described.

In this method, usually, metal particles (first particles) for securing electric connection, a conductive adhesive containing a binder resin, a curing agent and various additives, and further, a second particle are used. Is added. The second particles preferably have a lower standard electrode potential than the first particles (in other words, are susceptible to corrosion), and further have a lower standard electrode potential than the electrodes of the electronic components and the circuit board to be connected. That is, a preferable magnitude relation of the standard electrode potential is (first particle)>(electrode)> (second particle). If the standard electrode potential of the second particles is relatively lower than the standard electrode potential of the electrode, corrosion of the electrode can be effectively suppressed. The second through the first particle
This is because the particles and the electrodes are electrically connected to each other to form a corrosion battery, and the second particles having a relatively low potential corrode preferentially to the electrodes. Specifically, the standard electrode potential of the second particles is preferably lower than Sn in view of the fact that a general-purpose metal is Sn or an alloy containing Sn on the electrode surface.

This is because, in the mounting structure, the moisture that has penetrated into the joints becomes an electrolyte, causing galvanic corrosion.

In practice, the water-soluble components contained in the conductive adhesive and the substrate may be dissolved in the intruded water. Electrolyte ions generated from this component have the effect of increasing the electrolytic capacity of water to promote corrosion of the electrode, but also promote the sacrificial corrosion of the second particles. The presence of electrolyte ions to some extent improves the reliability of corrosion prevention. As confirmed by the present inventors, it is preferable that from 1 to 10000 ppm, and more preferably from 1 to 100 ppm, of electrolyte ions be present in the conductive adhesive from the viewpoint of improving reliability. As the electrolyte ion, a halogen ion (especially chloride ion) generated from bromine, chlorine and the like, and an alkali metal ion generated from sodium, potassium and the like are preferable. In Examples described later, Zn as the second particles
When the particles and chloride ions coexisted, a remarkable corrosion inhibitory effect was recognized.

The electrolyte ions may affect the value of the standard electrode potential. Therefore, when the conductive adhesive contains 5 ppm or more of electrolyte ions, usually used deionized water (conductivity of 1 μm) is considered in consideration of the actual corrosion process.
It is preferable that the above-mentioned relationship be satisfied also at the standard electrode potential when water containing electrolyte ions is used instead of S- ¹ ). As a specific measurement object, the above deionized water to which 3% by weight of NaCl is added may be used.

The first particles are composed of noble metals (gold (Au), silver (Ag), platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), osmium (O
s), metal particles of ruthenium (Ru)), Ag-Pd
Alloys of noble metals, such as alloys, are preferred. If the standard electrode potential is equal to or higher than the standard electrode potential of silver, particles containing a metal other than a noble metal, for example, copper (Cu) particles coated with Ag may be used. In view of the volume resistivity and the material cost, the first particles are preferably Ag particles.

[0019] The first particles may be corroded even if the second particles corrode.
It is preferable that the conductive adhesive be contained to such an extent that electrical connection can be maintained.
It is good to be more than 95 weight% below 95 weight%.

The second particles are made of a base metal or a non-metal, specifically, iron (Fe), carbon (C), aluminum (Al),
Zinc (Zn), magnesium (Mg), nickel (N
i), copper (Cu), beryllium (Be), chromium (C
r), at least one selected from tin (Sn), vanadium (V) and calcium (Ca).

It is desirable that the second particles have a property of easily forming an oxide. Specifically, Zn, Fe, M
At least one selected from g, Cu, V, Ca and Be is preferably used, and Zn is particularly preferable. When the second particles are oxidized, the surface of the second particles contains a large number of hydroxyl groups that are easily chemically bonded to the resin. When the adhesion between the binder resin and the metal particles is improved by this bonding, it is possible to suppress the penetration of moisture into the joint.

The second particles are carbon steel, SnAg,
A plurality of elements may be included, such as SnBi, SnCu, FeNi, BeCu, and stainless steel. Second
In the case of using an alloy as the particles, the potential of a component having a lower potential (Sn in the case of SnAg) may be adopted as a comparison target.

Generally, the content of the second particles is preferably 0.5% by weight or more and 10% by weight or less of the conductive adhesive.
If the content is too low, the effect of inhibiting corrosion may not be sufficiently obtained, and if it is too high, the conductivity of the conductive adhesive may be adversely affected. From this viewpoint, the content of the second particles is in a range exceeding 2% by weight of the conductive adhesive,
More preferably, it is at least 3% by weight.

When a lead component is used as an electronic component, when the content of the second particles is in the range of more than 2% by weight and 10% by weight or less, the effect of preventing corrosion is improved. this is,
When a lead component such as a QFP (Quad Flat Package) is used as compared with the case where a chip component is used, it is considered that the cause is that pressure is less likely to be applied to the conductive adhesive at the time of mounting the component. In the lead component, unlike the chip component in which the terminal electrode is prepared on the element main body, the lead protrudes from the element and extends as the terminal electrode.
The lead acts as a spring to reduce the force pressing the element.

If sufficient pressure is not applied to the conductive adhesive, the electrical contact between the first particles (for example, Ag particles) and the electrode surface (for example, SnPb) cannot be sufficiently maintained. In this state, the electrical connection between the second particles (for example, Zn particles) and the electrode is insufficient, and the second particles are easily consumed by self-corrosion. For this reason, when mounting a chip component, it is preferable to add the second particles slightly larger than the above in consideration of self-corrosion.

Since corrosion is suppressed by the addition of the second particles, a base metal can be used for an electrode of an electronic component or a circuit board. There is no limitation on the base metal used for the electrode,
Galvanic corrosion is likely to progress Sn, Pb, Cu, N
When at least one selected from i, Fe, and Be is used, the suppression of corrosion is particularly effective.

In the mounting structure in which the corrosion of the bonding portion is suppressed in this way, when used or left in an environment where galvanic corrosion easily proceeds, the corrosion of the second particles progresses. As a result, the second particles contain corrosive substances (typically at least one selected from oxides, hydroxides, chlorides and carbonates).
Species of compound). The present invention provides that the second particles are corroded,
It also includes a mounted structure that has been altered from the state when added. In this embodiment, if the corrosion of the second particles is more advanced than that of the electrode, the effect of suppressing the corrosion of the second particles can be confirmed.

Thus, the present invention includes a first particle having a standard electrode potential higher than the standard electrode potential of silver and a second particle having a standard electrode potential lower than the standard electrode potential of silver. A step of preparing a conductive adhesive; and a step of mounting an electronic component on a substrate using the conductive adhesive to suppress corrosion of the electronic component and / or the electrode of the substrate. It can also be understood as a corrosion control method.

An organic solvent may be further added to the conductive adhesive. When an organic solvent is added, the solvent partially dissolves the resin component at the interface between the conductive adhesive and the electrode, so that it is easy to maintain good electrical contact between the first particles and the electrode. In order to obtain this effect, for example, glycol ethers are preferable.Specifically, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether,
Propylene glycol monomethyl ether acetate,
It is preferable to use propylene glycol monoethyl ether, propylene glycol monoethyl ether acetate, or the like.

When a highly polar organic solvent is added,
Since it easily acts as a medium for the sacrificial corrosion reaction, the moisture resistance can be further improved. To achieve this effect, a dielectric constant of 15
It is preferable to use the above organic solvent, specifically,
DEG (diethylene glycol: 31.69; numerical value is dielectric constant, the same applies hereinafter), EG (ethylene glycol: 38.
66), DMF (N, N'-dimethylformamide: 3
6.71), N, N'-dimethylacetamide: 36.
71, DMSO (dimethyl sulfoxide: 46.5),
HMPA (hexamethylphosphoric triamide: 29.
6), NMP (N-methyl-2-pyrrolidone: 32.
2) or the like may be used.

The amount of the organic solvent added is not particularly limited, but is preferably in the range of 0.1% by weight to 10% by weight of the conductive adhesive.

When a material having a function of removing a metal oxide film is further added to the conductive adhesive, the moisture resistance reliability is further improved. A natural oxide film may be formed on the surface of the second particle, and this oxide film reduces the activity of the surface of the second particle. In addition, a natural oxide film may be formed on the surface of the electrode, and this oxide film suppresses sacrificial corrosion of the second particles and consequently promotes self-corrosion. Therefore, if the oxide film on the surface of the second particle (and the electrode after mounting) is removed or reduced by adding the metal oxide film removing material, the self-corrosion of the second particle is suppressed. , Can promote sacrificial corrosion. The suppression of the self-corrosion of the second particles is effective in maintaining the moisture resistance for a long period of time. It is sufficient that the metal oxide is reduced as compared with the case where no metal oxide is added, and it is not necessary to completely remove the metal oxide.

In order to remove or reduce the metal oxide film on the surface of the second particles and / or the electrodes, it is effective to add an activator. As the activator, a component added to the solder flux may be used. For example, activated rosin, a triol-based compound, an organic halide, or the like can be used. In addition, various organic acids, organic acid salts, inorganic acids, inorganic metal salts, and the like having the above action may be used as the activator. As the activator, specifically, oleic acid, lactic acid, benzoic acid, o-aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, glycerin, citric acid, stearic acid, oxalic acid, urea, thioic acid Urea, ethylenediamine, diethylenetriamine, hydrazine, glutamate, aniline hydrochloride, cetylpyridine bromide, abietic acid, phenylhydrazine hydrochloride, tetrachloronaphthalene, methylhydrazine hydrochloride, dimethylamine hydrochloride, diethylamine hydrochloride, dibutylamine hydrochloride Salt, cyclohexylamine hydrochloride, diethylethanolamine hydrochloride, zinc chloride, stannous chloride, potassium chloride, cuprous chloride, nickel chloride, ammonium chloride, tin bromide,
Zinc bromide, sodium bromide, ammonium bromide, sodium chloride, lithium chloride and the like can be used.

The use of an antioxidant can also reduce the amount of metal oxide film formed on the surface of the second particles. As the antioxidant, for example, a sulfur-based antioxidant, a phosphorus-based antioxidant, an amine-based antioxidant, and a phenol-based antioxidant may be used, and specifically, phenyl salicylate, monoglycol salicylate, etc. Rate, 2-hydroxy-4
-Methoxybenzophenone, 2 (2'-hydroxy-
5'-methylphenyl) benzotriazole, 2-mercaptobenzimidazole, N-salicyloyl-N'-
Acetylhydrazine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, phenyl-β-naphthylamine, α-naphthylamine, 2,6-di-tert-butyl-p-cresol, 2,6- Di-tert-butyl-phenol, triphenylphosphite, tridecylphosphite, trioctadecylphosphite, trilauryltrithiophosphite, ascorbic acid, glucose, dilaurylthiodipropionate, distearylthiodipropionate, 2- Mercaptobenzimidazole, dilauryl sulfide, propyl gallate, octyl gallate, dodecyl gallate, β, β'-
Thiodipropionic acid or the like can be used.

The amount of at least one selected from the group consisting of an activator and an antioxidant is not particularly limited, but is preferably in the range of 0.1% by weight to 10% by weight of the conductive adhesive.

The conductive adhesive usually requires an additional binder resin. As the binder resin, a thermosetting resin such as an epoxy resin, a phenol resin, a urea resin, a melamine resin, a furan resin, an unsaturated polyester resin, a diallyl phthalate resin, and a silicone resin can be used. The binder resin includes thermoplastic resins such as vinyl chloride resin, vinylidene chloride resin, polystyrene resin, ionomer resin, methylpentene resin, polyallomer resin, fluorine resin, polyamide resin, polyimide resin, polyamideimide resin, and polycarbonate. Although the use of a thermoplastic resin reduces the bonding strength, the binder resin is preferably made of a thermosetting resin.

The amount of the binder resin to be added is not particularly limited, but is preferably in the range of 5% by weight to 25% by weight of the conductive adhesive.

The conductive adhesive may further contain a curing agent, an adhesion improving agent, a discoloration preventing agent, an anti-sagging agent, and the like.

Next, the second method will be described.

In the second method, the surface of an electrode of an electronic component and / or a circuit board is modified, and a metal compound film is formed on the surface to increase the potential of the electrode. In this case, a particularly preferable magnitude relation of the standard electrode potential is (metal compound coating)> (metal particles (first particles)).
≧ (silver). By making the potential of the electrode relatively high, corrosion of the electrode can be effectively suppressed. Metal particles,
Since it has a potential higher than that of silver, corrosion does not substantially proceed. The metal compound coating does not need to be formed on all electrodes, but may be formed on an electrode where corrosion is a problem, specifically, an electrode having a standard electrode potential lower than that of metal particles.

Specifically, the modification of the metal compound film may be carried out by, for example, sulphidizing the surface of the terminal electrode or sulphating the metal by contact with an inorganic acid. Although there is no particular limitation on the method of modification, for example, sulfidation by contact with hydrogen sulfide is preferable.

The electric resistivity of the metal compound film is 1 × 10
^-4 Ωcm or less is preferable. This is because the connection resistance of the mounting structure is not easily affected.

The metal compound coating is preferably made of a metal compound substantially insoluble in water. Here, the term “substantially insoluble in water” specifically means that the solubility (the maximum mass that can be dissolved in 100 g of water) s is less than 1 × 10 ⁻² g and the solubility product Ksp in water is less than 1 × 10 ^−5. It is to be. In addition,
The solubility s and the solubility product Ksp are both 20 ° C.
(The same applies hereinafter).

The metal compound film is preferably a metal sulfide film. This is because many metal sulfides are insoluble in water and have excellent conductivity. For example, tin sulfide Sn
S is water-insoluble (solubility product: 1 × 10 ⁻²⁷ ) and 1
It has an electrical resistivity of × 10 ⁻⁴ Ωcm or less. However, the metal compound constituting the metal compound film may be a metal salt such as chromate, oxalate, phosphate, sulfate or the like, or may form a complex.

Also in this case, since the corrosion is suppressed by the metal compound coating, a base metal can be used for the electrodes of the electronic parts and the circuit board. Although the base metal used for the electrode is not limited, the use of the above-mentioned metal, in which galvanic corrosion is likely to progress, is particularly effective in suppressing corrosion.

FIG. 1 is a plan view of an example of a mounting structure using chip components. This mounting structure is configured such that chip resistors 3, 4, and 5, which are examples of other electric structures, are surface-mounted on electrodes 2 of a circuit board 1 made of ceramic.
The electrode 2 is provided with the conductive adhesive layer 6 made of the conductive adhesive of the present invention described above. The conductive adhesive layer 6 allows the electrodes 2 and the chip components 3 to
5 are electrically connected. Alternatively, a metal compound film is formed on the electrode 2 of the circuit board and / or the electrode of the chip component. Instead of the chip resistor, another component such as a chip capacitor may be used.

FIG. 3A shows Q as an example of a lead component.
FIG. 4 shows a perspective view of the FP. The plurality of leads 12 extending from the side surface of the element portion 11 of the lead component extend downward while bending. This QFP is bonded to the land 14 of the substrate 15 using the conductive adhesive 13 as shown in FIG.

[0048]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

In the following Examples 1 to 12 and Comparative Examples 1 and 2, changes in electrical resistance were measured using the test pieces shown in FIG. The test piece had electrodes 8 and 30 at a position separated by 30 mm.
The substrate 7 on which the substrate 9 was formed was used. The surfaces of the electrodes 8, 9 are made of a SnPb alloy (Sn ₉₀ Pb ₁₀ alloy). on the other hand,
The conductive adhesive was mixed with 7% by weight of bisphenol F type epoxy resin (liquid), 2% by weight of additives (dispersant, adhesion improver, etc.), and 89% by weight of Ag metal particles A, 2%.
The mixture was prepared by adding predetermined weight% of metal particles B and kneading using a three-roll mill. Further, depending on the sample, an organic solvent, an activator and an antioxidant were further added. in this case,
The addition amount of the bisphenol F type epoxy resin was reduced by the amount of the added component. Here, the metal particles A are substantially spherical, and have an average particle size of 2 to 15 μm.

Next, a conductive adhesive layer 10 was formed by a screen printing method so as to extend between the electrodes.
Further, the conductive adhesive layer was placed in an oven at 150 ° C. for 3 hours.
It was cured by heating for 0 minutes. The specimen thus produced was subjected to a moisture resistance test in which the specimen was left in a thermo-hygrostat kept at 85 ° C. and a relative humidity of 85% for 1000 hours, and the electric resistance between the electrodes 8 and 9 before and after the test (initial resistance and after the test) Measured value) was measured.

Example 1 As metal particles B, Ni particles (substantially spherical, average 5 μm, particle diameter 3 to 7 μm) were used.

Here, the standard electrode potential is Ni (−0.2
5V) <Sn (-0.14V) <Pb (-0.13V)
<Ag (+0.80 V) is satisfied. Therefore,
The potential of the metal particles B is lower than that of the SnPb alloy.

Example 2 Carbon steel particles (spherical, average particle size 5 μm, carbon content 5% by weight) were used as metal particles B.

Here, the standard electrode potential was deionized water to which 3% by weight of NaCl was added, and the standard electrode potential was C
(−0.76V) <Pb (−0.50V) <Sn (−
0.42 V) <Ag (−0.13 V).
Note that, as in Example 1, the relative relationships among C, Pb, Sn, and Ag for the standard electrode potential measured in deionized water are as described above.

(Examples 3 to 12) As the metal particles B, Z
n particles (spherical, average particle size 5 μm) were used.

Under the above measurement conditions where chloride ions are present, the standard electrode potential is Zn (−1.03 V) <Pb (−
0.50 V) <Sn (−0.42 V) <Ag (−0.1
3V). Zn has a property of easily forming an oxide than Ni and C. Note that, even when measured in deionized water, the relative relationship between the standard electrode potentials of Zn, Pb, Sn, and Ag is as described above.

In the fourth to twelfth embodiments,
Further, an organic solvent and an activator / antioxidant were added.

(Comparative Example 1) The same measurement as in each of the above Examples was performed without adding the metal particles B.

The results obtained as described above are summarized in (Table 1).

(Table 1) ――――――――――――――――――――――――――――――――― Metal Particle B NaCl Solvent Activator / Antioxidant Initial resistance Resistance after test (wt%) (ppm) (wt%) (wt%) (mΩ) (mΩ) ――――――――――――――――――――― ―――――――――――――― Example 1 Ni 25 − − 13 29 Example 2 C steel 25 − − 13 21 Example 3 Zn 25 − − 13 18 Example 4 Zn 2 5 BC 2-12 16 Example 5 Zn 25 DEG 2-12 15 Example 6 Zn 25 DEG 2 L (+)-ascorbic acid 0.5 11 11 Example 7 Zn 25 DEG 2 D (+)-coulose 0.5 11 11 Example 8 Zn 25 DEG 2 Oleic acid 0.5 11 11 Example 9 Zn 25 DEG 2 Glycerin 0.5 11 11 Example 10 Zn 25 DEG 2 Zinc chloride 0.5 11 1 1 Example 11 Zn 25 DEG 2 Phenyl salicylate 0.5 11 11 Example 12 Zn 25 DEG 2 Octyl gallate 0.5 11 11 Comparative Example 1-5 − − 12 326 ――――――――――― ―――――――――――――――――――――――― BC: ethylene glycol monobutyl ether, DEG: ethylene glycol

It is considered that the detected sodium chloride was contained in the bisphenol F type epoxy resin. Ni used in Example 1 has a standard electrode potential higher than Pb under the above measurement conditions in which electrolyte ions are present.
The resistance value after the test has increased slightly. Also, from the results shown in Table 1, the addition of the organic solvent and the activator / antioxidant
It was also confirmed that the resistance value was effective in preventing the initial value from decreasing and increasing.

(Examples 13 to 24)
Using the conductive adhesive used in No. 12, a chip component structure was actually produced.

Here, an electrode is formed of SnPb-plated Cu on the surface of a ceramic circuit board (30 × 60 mm, thickness 1.6 mm) so as to have the same configuration as that of FIG. Using the above conductive adhesives, a 0Ω chip resistor (3216 size, SnPb plating), a chip coil (diameter 8 mmφ, height 4 mm, SnP
b plating) and a chip capacitor (3216 size, SnPb plating). The method of applying and curing the conductive adhesive was the same as described above.

Examples 13 to 24 were made using the conductive adhesives of Examples 1 to 12, respectively.

(Example 25) In this example also, the conventional conductive adhesive used in Comparative Example 1 was used, and Examples 13 to 24 were used.
In the same manner as in the above, a chip component mounting structure was produced. However, in this case, the surface of the electrode on the ceramic circuit board was subjected to sulfuration treatment. That is, before applying the conductive adhesive, the ceramic circuit board was placed in a capacity of 0.34 m ^{3 at} a temperature of 4
The vessel was placed in a closed vessel at 0 ° C. and a relative humidity of 90%, and hydrogen sulfide was supplied for 24 hours so that the concentration of hydrogen sulfide in the vessel was 3 ppm. The standard electrode potential is Ag (0.80 V) <S
The relationship of nS (0.87 V) <PbS (0.93 V) is satisfied.

SnS and PbS are substantially insoluble in water (the solubility product of SnS, Ksp: 1 × 10 ⁻²⁷ , P
It has high conductivity with a solubility of bS: 1 × 10 ⁻³ g / 100 g water) and an electric resistivity of 1 × 10 ⁻⁴ Ωcm or less.

Comparative Example 2 Using the conventional conductive adhesive used in Comparative Example 1, the same chip component mounting structure as in Examples 13 to 24 was produced. Here, the surface treatment of the electrodes of the circuit board was not performed.

The chip partial mounting structure thus manufactured was left in a thermo-hygrostat kept at 85 ° C. and a relative humidity of 85% for 1000 hours, and the series resistance of the three components before and after the standing was measured. The results obtained are summarized in Table 2 below.

(Table 2) (Resistance value; Ω) --------------------------------------------------------------------------- Conductive adhesive Electrode surface treatment Initial resistance value Measured value after test ――――――――――――――――――――――――――――――――― Example 13 Example 1 − 2.5 3.6 Example 14 Example 2-2.5 3.1 Example 15 Example 3-2.5 2.8 Example 16 Example 4-2.4 3.5 Example 17 Example 5-2.4 3.0 Example 18 Example 6-2.3 2.5 Example 19 Example 7-2.3 2.5 Example 20 Example 8-2.3 2.5 Example 21 Example 9-2.3 2.5 Example 22 Example 10-2.3 2.5 Example 23 Example 11-2.3 2.5 Example 24 Example 12-2.3 2.5 Example Example 25 Comparative Example 1 Sulfurized (SnS, PbS) 2.5 2.6 Comparative Example 2 Comparative Example 1 − 2.5 251.2 ―――――――――――――――――――――――――――――――――

(Examples 26 to 36) Lead component structures were actually produced using various conductive adhesives in the same manner as the above chip component structures, and subjected to a moisture resistance test.

Here, SnPb-plated Cu is applied to the surface of the circuit board so as to have the same configuration as that of FIG.
A land electrode was formed, and a package size of 15 × 15 mm and 25 QFPs per side of the number of leads were mounted on this electrode using the above conductive adhesives. The interval between the lead terminals (FIG. 3: 12) is 0.5 mm. The resistance value was measured between all adjacent lead terminals electrically connected via the element body by a daisy chain, and the average value was used as the resistance value.

The conductive adhesive used and the resistance before and after the moisture resistance test are shown in Table 3.

(Table 3) ――――――――――――――――――――――――――――――――― Metal Particle B NaCl Solvent Activator / Antioxidant Initial resistance Resistance after test (wt%) (ppm) (wt%) (wt%) (mΩ) (mΩ) ――――――――――――――――――――― Example 26 Zn 25 − − 53 79 Example 27 Zn 2.55 − − 53 58 Example 28 Zn 35 − − 53 56 Example 29 Zn 35 DEG 2-53 55 Example 30 Zn 35 DEG 2 L (+)-ascorbic acid 0.5 52 52 Example 31 Zn 35 DEG 2 D (+)-coulose 0.5 52 52 Example 32 Zn 25 DEG 2 oleic acid 0.5 52 52 Example 33 Zn 25 DEG 2 Glycerin 0.5 52 52 Example 34 Zn 25 DEG 2 Zinc chloride 0.5 52 52 Example 35 Zn 25 DEG 2 Phenylsalici 0.5 52 52 Example 36 Zn 25 DEG 2 Octyl gallate 0.5 52 52 ――――――――――――――――――――――――――――― ――――

As shown in Table 3, the effect of the addition of the second particles (metal particles B) when mounting the lead component was 2%.
It became remarkable in the range exceeding 3% by weight and became stable at 3% by weight or more.

Further, in Example 15, the cross section of the conductive adhesive after the test was subjected to SIMS (secondary ion mass spectrometry).
As shown in FIGS. 4A and 4B, the portion where the Zn concentration was high and the portion where the O concentration was high coincided well as shown in FIGS. 4A and 4B (in each of FIGS. The smaller the interval, the higher the concentration of the target element was detected.) Thus, in the Zn particles in the conductive adhesive,
Oxygen atoms were present almost uniformly after the moisture resistance test. It is considered that the Zn particles were entirely changed to oxides or hydroxides due to sacrificial corrosion.

On the other hand, in Comparative Example 2, when a cross section near the interface between the conductive adhesive and the component electrode after the test was analyzed by SIMS, as shown in FIG. 5A and FIG. In the portion where the concentration was high, the oxygen concentration was slightly higher. The oxygen concentration in the conductive adhesive is lower than the electrode surface (FIG. 5B).

In the above description, a chip component mounting structure and a lead component mounting structure have been described as examples of component mounting structures. However, the present invention is not limited to this, and other components such as CSP ( Chip scale package), BGA
(Ball grid array) and other package parts,
It can be used for mounting various components such as chip components and lead components such as electrolytic capacitors, diodes, and switches, and bare IC mounting.

[0078]

As described above, according to the present invention, it is possible to provide a conductive adhesive and a mounting structure having improved moisture resistance reliability. In particular, according to the present invention, the moisture resistance can be improved while using a general-purpose base metal electrode, so that the use of a conductive adhesive and a mounted product using the same can be greatly expanded.

[Brief description of the drawings]

FIG. 1 is a plan view of one embodiment of a mounting structure of the present invention.

FIG. 2 is a plan view of a test piece used for evaluating the conductive adhesive of the present invention.

FIG. 3A is a perspective view illustrating an example of a lead component, and FIG. 3B is a cross-sectional view of one embodiment of a mounting structure of the present invention using the lead component.

4A and 4B are diagrams showing the results of analyzing the composition of a conductive adhesive in a sample to which the present invention has been applied after a moisture resistance test by using SIMS, wherein FIG. 4A shows the distribution of Zn, and FIG. Are shown respectively.

FIG. 5 is a diagram showing a result of analyzing, using SIMS, the vicinity of an interface between a conductive adhesive and an electrode of an electronic component after a moisture resistance test in a sample to which the conventional technique is applied.
5A shows the distribution of Sn, and FIG. 5B shows the distribution of O.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Electrode 3, 4, 5 Chip resistance 6 Conductive adhesive layer 11 Element 12 Lead 13 Conductive adhesive 14 Land 15 Substrate

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[Procedure amendment]

[Submission date] January 31, 2002 (2002.1.3
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

The conductive adhesive according to the present invention is used for electrically connecting an electronic component and a substrate, and comprises a first particle for securing an electrical connection, and a first particle . of
And a second particle having a lower standard electrode potential than the particle.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

The present invention also provides a mounting structure in which electrodes of an electronic component and electrodes of a substrate are electrically connected by using the above-mentioned conductive adhesive. In the mounting structure of the present invention, the second
The standard electrode potential of the particle is compared with the standard electrode potential of the electrode of the electronic component.
And the standard electrode potential of the substrate electrode
Preferably. Also, the standard electrode potential of the first particles is
The standard electrode potential of the second particle which is equal to or higher than the standard electrode potential of silver;
Preferably, the potential is lower than the standard electrode potential of silver. In this mounting structure, the second particles may corrode and exist as at least one compound selected from oxides, hydroxides, chlorides, and carbonates.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/34 501 H05K 3/34 501D (72) Inventor Yukihiro Ishimaru 1006 Odakadoma, Kadoma City, Osaka Matsushita Electric Inside Sangyo Co., Ltd. (72) Inventor Riki Mitani 1006, Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Inventor Shinji Kobayashi 1006 Kazuma, Kazuma, Osaka Pref.F-term (reference) in Matsushita Electric Industrial Co., Ltd. DA42 DD03

Claims (23)

[Claims] 1. A conductive adhesive for electrically connecting an electronic component and a substrate, the first particle having a standard electrode potential equal to or higher than the silver standard electrode potential; A conductive adhesive containing second particles lower than the standard electrode potential. 2. The method according to claim 1, wherein the second particles are Fe, C, Al, Zn,
The conductive adhesive according to claim 1, comprising at least one selected from Mg, Ni, Cu, Be, Cr, Sn, V, and Ca. 3. The conductive adhesive according to claim 2, wherein the second particles include Zn. 4. The conductive adhesive according to claim 1, wherein the standard electrode potential of the second particles is lower than Sn. 5. The conductive adhesive according to claim 1, further comprising 1 to 10000 ppm of electrolyte ions. 6. The conductive adhesive according to claim 5, wherein the electrolyte ions include chloride ions. 7. The conductive adhesive according to claim 1, wherein the content of the first particles is 70% by weight or more and 95% by weight or less. 8. The conductive adhesive according to claim 1, wherein the content of the second particles is 0.5% by weight or more and 10% by weight or less. 9. The conductive adhesive according to claim 8, wherein the content of the second particles exceeds 2% by weight. 10. The method according to claim 1, further comprising a binder resin.
10. The conductive adhesive according to any one of 9. 11. The conductive adhesive according to claim 10, wherein the binder resin is a thermosetting resin. 12. The method according to claim 1, further comprising an organic solvent.
The conductive adhesive according to any one of the above. 13. The conductive adhesive according to claim 12, wherein the organic solvent is a polar solvent having a dielectric constant of 15 or more. 14. The method according to claim 14, further comprising a material for removing a metal oxide film,
The conductive adhesive according to any one of claims 1 to 13, wherein the metal oxide film on the surface of the second particles is removed or reduced by the metal oxide film removing material. 15. The conductive adhesive according to claim 1, further comprising at least one selected from an activator and an antioxidant. 16. A mounting structure including an electronic component, a substrate, and a conductive adhesive, wherein an electrode of the electronic component and an electrode of the substrate are electrically connected using a conductive adhesive,
A mounting structure, wherein the conductive adhesive is the conductive adhesive according to claim 1. 17. A mounting structure including an electronic component, a substrate, and a conductive adhesive, wherein an electrode of the electronic component and an electrode of the substrate are electrically connected using a conductive adhesive,
An oxide formed by corroding a first particle having a standard electrode potential equal to or higher than a standard electrode potential of silver and a second particle having a standard electrode potential lower than the standard electrode potential of silver; And a at least one compound selected from hydroxides, chlorides and carbonates. 18. The mounting structure according to claim 16, wherein the standard electrode potential of the second particles is lower than any of the standard electrode potential of the electrode of the electronic component and the standard electrode potential of the electrode of the substrate. 19. A mounting structure including an electronic component, a substrate, and a conductive adhesive, wherein an electrode of the electronic component and an electrode of the substrate are electrically connected using a conductive adhesive,
The conductive adhesive contains particles whose standard electrode potential is equal to or higher than the standard electrode potential of silver, and is at least one electrode selected from the electrodes of the electronic component and the electrodes of the substrate, wherein the standard electrode potential is the particles. A mounting structure in which a metal compound film having a standard electrode potential higher than the standard electrode potential of the particles is formed on a surface of the lower electrode. 20. The electric resistivity of the metal compound film is 1 × 1.
The mounting structure according to claim 19, wherein the mounting structure is 0 ⁻⁴ Ωcm or less. 21. The mounting structure according to claim 19, wherein the metal compound coating comprises a metal compound substantially insoluble in water. 22. The mounting structure according to claim 19, wherein the metal compound coating is a metal sulfide coating. 23. At least one electrode selected from an electrode of an electronic component and an electrode of a substrate is composed of Sn, Pb, Cu,
The mounting structure according to any one of claims 16 to 22, comprising at least one selected from Ni, Fe, and Be.