JP6192444B2 - Solder composition for fine pattern coating - Google Patents

Description

  The present invention relates to a solder composition for applying a solder composition to a fine pattern by a jet dispenser or the like.

  In recent years, electronic devices have been reduced in size and weight, and at the same time, high-density mounting of wiring boards has been advanced. As the electronic components to be mounted are further reduced in size, the connection terminal pitch is also reduced. As a result, since the connection terminal itself needs to be small, the connection strength between the electronic component and the wiring board is weakened. As one of the strengthening measures, a method of putting an underfill agent between an electronic component and a wiring board and curing it has been put into practical use. However, there is a drawback that the mounting process becomes long, or repair is not possible when an electronic component or a bonding failure is found.

Therefore, it is required to improve the connection strength between the electronic component and the wiring board by using a solder paste. For example, it contains a flux containing a thermosetting resin, an organic acid, a solvent and a curing agent, and a solder powder. A solder paste has been proposed (for example, Patent Document 1).
Further, such solder paste is required to be applied in various application formats. As one of them, in recent years, it has been required to apply a solder paste in a fine pattern with a jet dispenser. In this case, it is necessary to reduce the particle diameter of the solder powder according to the size of the fine pattern.

JP 2001-219294 A

Since the solder paste described in Patent Document 1 is thermosetting, the connection strength between the electronic component and the wiring board can be reinforced (such a solder paste is also referred to as a thermosetting solder composition). However, when the solder paste described in Patent Document 1 is used to apply a solder paste to a fine pattern with a jet dispenser (this type of application is also referred to as fine pattern application), the following (i) and (ii) There is a problem like this.
(I) From the viewpoint of applicability in fine pattern application, it is necessary to reduce the particle diameter of the solder powder. However, in this case, the surface area of the solder powder is increased and the surface oxide film is increased, so that the solder meltability is lowered. On the other hand, in order to improve solder meltability, it is conceivable to increase the acid value of an activator such as an organic acid or to increase the blending amount. However, if this is done, there is a problem that the pot life is significantly reduced.
(Ii) From the viewpoint of applicability in fine pattern application, when the particle size of the solder powder is reduced, the viscosity of the solder paste is increased. Therefore, in order to reduce the viscosity of the solder paste, the solvent ratio in the composition must be increased. However, in this case, since the solvent remaining in the resin increases, the resin curability is lowered.
As described above, when a fine pattern is applied using a solder paste, it is difficult to satisfy all of applicability, resin curability, pot life, and solder meltability.

  Then, an object of this invention is to provide the solder composition for fine pattern application | coating which was excellent in applicability | paintability, resin sclerosis | hardenability, pot life, and solder meltability, when applying fine pattern.

The solder composition for fine pattern application of the present invention is a solder composition for fine pattern application for applying a solder composition to a fine pattern by a jet dispenser, and (A) a lead-free solder having a melting point of 240 ° C. or lower 70 mass% or more and 85 mass% or less of powder, (B) epoxy resin, (C) monomer, glycidyl group-containing compound that is liquid at 25 ° C., (D) activator, (E) curing agent, and (F A thermosetting resin composition containing 15% by mass to 30% by mass of the thixotropic agent, and the lead-free solder powder (A) has one or more hydroxyl groups in one molecule. Carboxylic acid or aromatic monocarboxylic acid is adhered to the surface of the solder powder to be treated, adsorbed, or bonded, and the average particle of the (A) lead-free solder powder What child diameter state, and it is more 12μm or less 1 [mu] m, a viscosity at 25 ° C. as measured by E-type viscometer of the fine pattern coating solder composition, and less than 10 Pa · s or higher 60 Pa · s It is.

In the solder composition for applying a fine pattern of the present invention, the (C) glycidyl group-containing compound has a viscosity measured by an E-type viscometer at a temperature of 25 ° C. of 1 mPa · s to 2000 mPa · s. Preferably there is.
In the solder composition for applying a fine pattern of the present invention, the (A) lead-free solder powder is preferably made of an alloy of tin and bismuth.
In the solder composition for applying a fine pattern of the present invention, the (B) epoxy resin is preferably liquid at 25 ° C.
In the solder composition for applying a fine pattern of the present invention, the (D) activator preferably contains (D1) dicarboxylic acid and (D2) an organic acid amine salt.

Although the reason why the fine pattern coating solder composition of the present invention is excellent in all of coating property, resin curability, pot life and solder melting property is not necessarily clear, the present inventors speculate as follows. .
That is, in the solder composition of the present invention, the particle diameter of the (A) lead-free solder powder is made sufficiently small from the viewpoint of applicability in fine pattern application. On the other hand, in this case, since the surface area of the solder powder increases and the oxide film on the surface increases, the solder meltability tends to decrease. However, in the solder composition of the present invention, (A) the lead-free solder powder contains an aliphatic monocarboxylic acid or an aromatic monocarboxylic acid having one or more hydroxyl groups in one molecule, It is attached, adsorbed or bound to the surface. In such a case, (A) the surface of the lead-free solder powder is in a state of bonding between the metal and the carboxylic acid, and the surface of the solder powder has one or more hydroxyl groups in one molecule. It is covered with an aliphatic monocarboxylic acid or aromatic monocarboxylic acid film. Thereby, the oxidation of the surface of solder powder can be suppressed and solder meltability can be improved. Further, deterioration of characteristics due to oxidation of the solder powder can be prevented, and the pot life of the solder composition can be improved.
Moreover, the solder composition of the present invention does not contain a solvent as an essential component. In the thermosetting solder composition as in the present invention, there is a problem that the resin curability becomes insufficient if a solvent remains during reflow or the like. However, in the solder composition of the present invention, since no solvent remains at the time of reflow or the like, the resin curability becomes high. On the other hand, when the viscosity cannot be adjusted by the solvent, the solder composition using the solder powder having a small particle diameter cannot be made low in viscosity, and the applicability in applying the fine pattern is deteriorated. However, in the solder composition of the present invention, the viscosity can be adjusted with (C) a glycidyl group-containing compound in addition to (B) epoxy resin, (D) activator and (F) thixotropic agent, which is sufficiently low. Can be viscosity. As described above, the present inventors speculate that the solder composition of the present invention can satisfy all of application properties, resin curability, pot life and solder meltability.

  ADVANTAGE OF THE INVENTION According to this invention, when apply | coating a fine pattern, the solder composition for fine pattern application excellent in applicability | paintability, resin curability, pot life, and solder meltability can be provided.

The solder composition of the present invention includes (A) a lead-free solder powder of 70% by mass to 92% by mass described below, (B) an epoxy resin, (C) a glycidyl group-containing compound, and (D) an activator described below. And (E) a thermosetting resin composition containing 8% by mass to 30% by mass of a thermosetting resin composition containing a curing agent and (F) a thixotropic agent.
When the content of the lead-free solder powder (A) is less than 70% by mass (when the content of the thermosetting resin composition exceeds 30% by mass), when the resulting solder composition is adhered A sufficient solder joint cannot be formed between the electronic component and the wiring board, and the electrical conductivity between the electronic component and the wiring board becomes insufficient. On the other hand, when the content of the (A) lead-free solder powder exceeds 92% by mass (when the content of the thermosetting resin composition is less than 8% by mass), the particle size of the solder powder must be increased. This makes it difficult to apply a fine pattern. In the obtained solder composition, from the viewpoint of applicability in fine pattern application, the content of the (A) lead-free solder powder is preferably 75% by mass or more and 90% by mass or less, and 80% by mass. More preferably, it is 85 mass% or less.

[(A) Lead-free solder powder]
The lead-free solder powder (A) used in the present invention is obtained by adhering, adsorbing, or bonding aliphatic monocarboxylic acid or aromatic monocarboxylic acid to the surface of the solder powder to be treated.

The aliphatic monocarboxylic acid or aromatic monocarboxylic acid used in the present invention needs to have one or more hydroxyl groups in one molecule.
The hydrocarbon group in the aliphatic monocarboxylic acid preferably has 12 or more and 20 or less carbon atoms. The hydrocarbon group in the aromatic monocarboxylic acid preferably has 6 or more carbon atoms, and more preferably 6 to 18 carbon atoms. If the carbon number is less than the lower limit, deterioration of physical properties due to oxidation of the solder powder tends not to be prevented.

Examples of the aliphatic monocarboxylic acid include hydroxyenanthic acid, hydroxycapric acid, hydroxylauric acid, hydroxymyristic acid, hydroxypentadecyl acid, hydroxypalmitic acid, hydroxymargaric acid, and hydroxystearic acid.
Examples of the aromatic monocarboxylic acid include hydroxybenzoic acid (such as 4-hydroxybenzoic acid and salicylic acid), dihydroxybenzoic acid (such as 2,4-hydroxybenzoic acid), hydroxynaphthalene acid, and dihydroxyhydroxynaphthalene acid.

The solder powder to be processed used in the present invention has a melting point of 240 ° C. or lower. When the solder powder having the melting point of 240 ° C. is used, it is difficult to melt the lead-free solder powder at a normal bonding temperature in the solder composition. The melting point of the solder powder to be treated is preferably 180 ° C. or lower, more preferably 170 ° C. or lower, and particularly preferably 150 ° C. or lower from the viewpoint of lowering the bonding temperature.
The lead-free solder powder means a solder metal or alloy powder to which lead is not added. However, it is allowed that lead is present as an inevitable impurity in the lead-free solder powder, but in this case, the amount of lead is preferably 100 mass ppm or less.

The (A) lead-free solder powder is selected from the group consisting of tin (Sn), copper (Cu), silver (Ag), bismuth (Bi), antimony (Sb), indium (In), and zinc (Zn). It is preferable to contain at least one metal. Among these, from the viewpoint of the melting point of the solder powder, it is more preferably made of an alloy of tin and bismuth.
Moreover, when the said (A) component consists of an alloy of tin and bismuth, content of the bismuth in the said (A) component is 58 mass% or less with respect to 100 mass% of total amounts of tin and bismuth. It is preferable.

Specific examples of the solder composition (mass ratio) in the lead-free solder powder (A) include the following.
As binary alloys, for example, Ag-Bi type such as 95.3Ag / 4.7Bi, Ag-Li type such as 66Ag / 34Li, Ag-In type such as 3Ag / 97In, Ag-type such as 67Ag / 33Te, etc. Te, Ag-Tl such as 97.2Ag / 2.8Tl, Ag-Zn such as 45.6Ag / 54.4Zn, Au-Sn such as 80Au / 20Sn, 52.7Bi / 47.3In, etc. Bi-In series, 35In / 65Sn, 51In / 49Sn, In-Sn series such as 52In / 48Sn, Bi-Zn series such as 8.1Bi / 91.9Zn, Sn-Bi series such as 43Sn / 57Bi, 42Sn / 58Bi , 98Sn / 2Ag, 96.5Sn / 3.5Ag, 96Sn / 4Ag, Sn-Ag series such as 95Sn / 5Ag, 91Sn / 9Zn, 30Sn / 7 Sn-Zn-based, such as Zn, Sn-Cu system, such 99.3Sn / 0.7Cu, include Sn-Sb system, such as 95Sn / 5Sb.
Examples of ternary alloys include Sn—Ag—In such as 95.5Sn / 3.5Ag / 1In, Sn—Zn—In such as 86Sn / 9Zn / 5In, 81Sn / 9Zn / 10In, and 95.5Sn. Sn-Ag-Cu systems such as /0.5Ag/4Cu, 96.5Sn / 3.0Ag / 0.5Cu, 98.3Sn / 1.0Ag / 0.7Cu, 99.0Sn / 0.3Ag / 0.7Cu 90.5Sn / 7.5Bi / 2Ag, Sn-Bi-Ag system such as 41.0Sn / 58Bi / 1,0Ag, and Sn-Zn-Bi system such as 89.0Sn / 8.0Zn / 3.0Bi. It is done.
Examples of other alloys include Sn / Ag / Cu / Bi system.

  The average particle size of the lead-free solder powder (A) is preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less, and particularly preferably 2 μm or more and 12 μm or less. If the average particle size of the lead-free solder powder is less than the lower limit, the meltability of the solder powder tends to be reduced, and if it exceeds the upper limit, the applicability in fine pattern application tends to be reduced. The average particle size can be measured with a laser diffraction / scattering particle size distribution analyzer.

As a method for producing the lead-free solder powder (A), for example, the following method can be adopted.
For example, by preparing a solution containing the aliphatic monocarboxylic acid or the aromatic monocarboxylic acid, immersing the solder powder to be treated in the solution, then washing and drying, the (A) Lead-free solder powder can be produced. In addition, the manufacturing method of said (A) lead-free solder powder is not limited to this method.

The solvent used for the solution is not particularly limited as long as it can dissolve the aliphatic monocarboxylic acid or the aromatic monocarboxylic acid. Examples of such a solvent include alcohols.
The processing conditions for the solder powder can be set as appropriate and are not particularly limited. For example, the concentration of the solution is preferably 5% by mass or more and 30% by mass or less. Moreover, it is preferable that the temperature of the said solution is 20 degreeC or more and 80 degrees C or less. The immersion time in the solution is preferably 10 minutes or more and 5 hours or less.

[(B) Epoxy resin]
As (B) epoxy resin used for this invention, a well-known epoxy resin can be used suitably. Examples of such epoxy resins include bisphenol A type, bisphenol F type, biphenyl type, naphthalene type, cresol novolac type, phenol novolac type, and dicyclopentadiene type epoxy resins. These epoxy resins may be used individually by 1 type, and may mix and use 2 or more types. In addition, these epoxy resins are liquid at room temperature (25 ° C.) such as liquid bisphenol A type, liquid bisphenol F type, and liquid hydrogenated type bisphenol A type from the viewpoint that the dispersibility of metal particles and paste viscosity can be adjusted. In the case of using a solid at room temperature, it is preferable to use it together with a liquid at normal temperature.

  As content of the said (B) epoxy resin, it is preferable that it is 30 to 80 mass% with respect to 100 mass% of thermosetting resin compositions, and it is 40 to 70 mass%. Is more preferable, and 50% by mass or more and 65% by mass or less is particularly preferable. If the content of the epoxy resin is less than the lower limit, sufficient strength to fix the electronic component tends to be not obtained. On the other hand, if the content exceeds the upper limit, the content of the curing component in the thermosetting resin composition Decreases, and the rate at which the thermosetting resin is cured tends to be delayed.

[(C) Glycidyl group-containing compound]
The (C) glycidyl group-containing compound used in the present invention is a monomer and is liquid at 25 ° C. In the thermosetting resin composition in the present invention, by replacing a part of the epoxy resin with such a glycidyl group-containing compound, while maintaining various properties such as curability of the thermosetting resin composition, The viscosity in a thermosetting resin composition can be adjusted to a more suitable range.
In such a (C) glycidyl group-containing compound, the viscosity measured with an E-type viscometer at a temperature of 25 ° C. is preferably 1 mPa · s or more and 2000 mPa · s or less, preferably 5 mPa · s or more and 100 mPa · s or less. It is more preferable that

As the (C) glycidyl group-containing compound, a known glycidyl group-containing compound can be appropriately used. Such a glycidyl group-containing compound may be monofunctional or polyfunctional. These may be used alone or in combination of two or more.
Examples of the monofunctional glycidyl group-containing compound include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, decyl glycidyl ether, stearyl glycidyl ether, allyl glycidyl ether, and 2-methyloctyl glycidyl ether. Ether, methoxy polyethylene glycol monoglycidyl ether, ethoxy polyethylene glycol monoglycidyl ether, butoxy polyethylene glycol monoglycidyl ether, phenoxy polyethylene glycol monoglycidyl ether, p-tertiary butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, n-butylphenyl Glycidyl ether, phenyl E Nord glycidyl ether, cresyl glycidyl ether, and the like dibromo cresyl glycidyl ether. Among these monofunctional glycidyl group-containing compounds, phenyl glycidyl ether is particularly preferable from the viewpoint of easy viscosity adjustment.
Examples of the polyfunctional glycidyl group-containing compound include cyclohexyldimethanol diglycidyl ether and 1,4-butanediol diglycidyl ether.

  The content of the (C) glycidyl group-containing compound is preferably 5% by mass or more and 40% by mass or less, and preferably 10% by mass or more and 30% by mass or less with respect to 100% by mass of the thermosetting resin composition. More preferably. If the content of the glycidyl group-containing compound is less than the lower limit, the effect of adjusting the viscosity of the thermosetting resin composition tends to be difficult to obtain. On the other hand, if the content exceeds the upper limit, the thermosetting resin composition is cured. Various characteristics such as sex tend to be lowered.

[(D) Activator]
The (D) activator used in the present invention preferably contains (D1) a dicarboxylic acid having 4 to 7 carbon atoms and (D2) an organic acid amine salt that is a salt of an amine and an organic acid. In addition, you may further contain well-known activators other than the said (D1) component and the said (D2) component.
The component (D1) is preferably a dicarboxylic acid having 4 to 7 carbon atoms. When the carbon number is less than 4, the pot life in the solder composition tends to be insufficient. On the other hand, when the carbon number exceeds 7, the solder wettability in the solder composition tends to be insufficient.
Examples of the component (D1) include adipic acid, 2,4-diethylglutaric acid, 2,2-diethylglutaric acid, 3-methylglutaric acid, glutaric acid, and succinic acid. These may be used alone or in combination of two or more. Among these (C1) components, adipic acid, glutaric acid, and the like are preferable from the viewpoint of a balance between pot life and solder wettability.

  The content of the component (D1) is preferably 0.5% by mass to 10% by mass and preferably 2% by mass to 6% by mass with respect to 100% by mass of the thermosetting resin composition. It is more preferable. When the content of the component (D1) is less than the lower limit, the solder wettability tends to decrease, and when it exceeds the upper limit, the pot life tends to decrease.

The component (D2) is preferably an organic acid amine salt that is a salt of an amine and an organic acid.
The component (D2) preferably has a softening point (also referred to as melting / decomposition start temperature) measured by thermogravimetric differential thermal analysis (TG / DTA) of 90 ° C. or higher and 210 ° C. or lower, and 110 ° C. or higher and 150 ° C. or higher. It is more preferable that it is below ℃. If the softening point is less than the lower limit, the pot life tends to be reduced. On the other hand, if the upper limit is exceeded, the solder wettability tends to be reduced. Here, the softening point can be measured by the following method.
TG / DTA measurement is performed under the following conditions while weighing 10 mg ± 3 mg using the organic acid amine salt as a sample and heating to 30 ° C. to 250 ° C. As a reference, 10 mg ± 3 mg of an inert alumina powder is weighed and used.
Measuring device: “TG / DTA6200” manufactured by Seiko Instruments Inc.
Atmosphere: Air temperature rising rate: 10 ° C / min

As said amine, a well-known amine can be used suitably. Such an amine may be an aromatic amine or an aliphatic amine. These may be used alone or in combination of two or more. As such an amine, an amine having 3 to 13 carbon atoms is preferably used, and a primary amine having 4 to 7 carbon atoms is more preferably used from the viewpoint of the stability of the organic acid amine salt.
Examples of the aromatic amine include benzylamine, aniline, and 1,3-diphenylguanidine.
Examples of the aliphatic amine include propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, cyclohexylamine, and triethanolamine.

As said organic acid, a well-known organic acid can be used suitably. Such an organic acid may be a monocarboxylic acid, a dicarboxylic acid, or a carboxylic acid other than these. Such organic acid may be an aliphatic carboxylic acid or an aromatic carboxylic acid. These may be used alone or in combination of two or more. Such an organic acid is preferably a dicarboxylic acid having 3 to 7 carbon atoms, more preferably a dicarboxylic acid having 5 to 6 carbon atoms, from the viewpoint of the stability of the organic acid amine salt.
Examples of the dicarboxylic acid include adipic acid, 2,4-diethylglutaric acid, 2,2-diethylglutaric acid, 3-methylglutaric acid, glutaric acid, succinic acid, and malonic acid.
Examples of the monocarboxylic acid include propionic acid, butyric acid, valeric acid, caproic acid, and enanthic acid.
Examples of the tricarboxylic acid include trimellitic acid, 1,2,3-propanetricarboxylic acid, and citric acid.

  The content of the component (D2) is preferably 0.5% by mass to 15% by mass and preferably 1% by mass to 10% by mass with respect to 100% by mass of the thermosetting resin composition. It is more preferable. When the content of the component (D2) is less than the lower limit, the solder wettability tends to decrease, and when it exceeds the upper limit, the pot life tends to decrease.

[(E) Curing agent]
As the (E) curing agent used in the present invention, a known curing agent can be used as appropriate. For example, the following can be used. One of these curing agents may be used alone, or two or more thereof may be mixed and used.
Examples of the latent curing agent include NOVACURE HX-3722, HX-3721, HX-3748, HX-3088, HX-3613, HX-392HP, HX-3941HP (trade name, manufactured by Asahi Kasei Epoxy Co., Ltd.), dicyandiamide (DICY). ) And the like.
Examples of the aliphatic polyamine curing agent include Fujicure FXR-1020, FXR-1030, FXR-1050, FXR-1080 (trade name, manufactured by Fuji Kasei Kogyo Co., Ltd.).
Examples of the epoxy resin amine adduct-based curing agent include Amicure PN-23, PN-F, MY-24, VDH, UDH, PN-31, and PN-40 (manufactured by Ajinomoto Fine Techno Co., Ltd., trade name), EH-3615S. EH-3293S, EH-3366S, EH-3842, EH-3670S, EH-3636AS, EH-4346S, EH-5016S (trade name, manufactured by ADEKA).
Examples of the imidazole curing accelerator include 2P4MHZ, 1B2PZ, 2MZA, 2PZ, C11Z, C17Z, 2E4MZ, 2P4MZ, C11Z-CNS, and 2PZ-CNZ (trade names, manufactured by Shikoku Kasei Kogyo Co., Ltd.).

  As content of the said (E) hardening | curing agent, it is preferable that it is 0.5 mass% or more and 10 mass% or less with respect to 100 mass% of thermosetting resin compositions, and is 2 mass% or more and 9 mass% or less. More preferably. If the content of the curing agent is less than the lower limit, the rate at which the thermosetting resin is cured tends to be delayed. On the other hand, if the upper limit is exceeded, the reactivity tends to be faster and the paste usage time tends to be shorter. .

[(F) thixotropic agent]
As the (F) thixotropic agent used in the present invention, a known thixotropic agent can be appropriately used. Examples of such thixotropic agents include organic thixotropic agents (fatty acid amide, hydrogenated castor oil, olefinic wax, etc.) and inorganic thixotropic agents (colloidal silica, benton, etc.). These thixotropic agents may be used alone or in combination of two or more. Among these, fatty acid amide, colloidal silica, and benton are preferable. Moreover, it is preferable to use it in combination with an organic thixotropic agent and an inorganic thixotropic agent from a viewpoint of the difficulty of bleeding of the solder composition obtained. Specifically, a combination of fatty acid amide and colloidal silica, and a combination of fatty acid amide and benton are exemplified.

  The thixotropic agent content is preferably 0.5% by mass or more and 10% by mass or less, and preferably 1% by mass or more and 8% by mass or less with respect to 100% by mass of the thermosetting resin composition. More preferred. If the content of the thixotropic agent is less than the above lower limit, thixotropy cannot be obtained, and when coating with a jet dispenser or the like, the cutting shape with the nozzle tends to be lowered, and the coating shape tends to deteriorate, while the upper limit is exceeded. If it exceeds, the thixotropy is too high and the coating tends to be poor due to clogging of the syringe needle.

  The thermosetting resin composition used in the present invention has an interface other than the component (B), the component (C), the component (D), the component (E), and the component (F) as necessary. You may contain additives, such as an activator, a coupling agent, an antifoamer, a powder surface treating agent, a reaction inhibitor, and an anti-settling agent. The content of these additives is preferably 0.01% by mass or more and 10% by mass or less, and 0.05% by mass or more and 5% by mass or less with respect to 100% by mass of the thermosetting resin composition. More preferably. If the content of the additive is less than the lower limit, the effect of each additive tends to be difficult to achieve. On the other hand, if the content exceeds the upper limit, the bonding strength due to the thermosetting resin composition tends to decrease.

Next, a method for connecting electrodes such as a wiring board and an electronic component using the solder composition of the present invention will be described. Here, the case where the electrodes of the wiring board and the electronic component are connected will be described as an example.
Thus, as a method of connecting the electrodes of the wiring board and the electronic component, an application step of applying the solder composition on the wiring board, and arranging the electronic component on the solder composition, and using a reflow furnace And a reflow process of heating the electronic component on the wiring board under a predetermined condition.

In the applying step, the solder composition is applied onto the wiring board.
The coating apparatus used here may be an apparatus capable of applying a fine pattern, and is, for example, a jet dispenser. The solder composition of the present invention is excellent in resin curability and applicability, and can be satisfactorily applied with such a jet dispenser.

In the reflow process, the electronic component is placed on the solder composition and heated in a reflow furnace under predetermined conditions. By this reflow process, sufficient soldering can be performed between the electronic component and the wiring board, and the resin can be cured. As a result, the electronic component can be mounted on the wiring board.
What is necessary is just to set reflow conditions suitably according to melting | fusing point of solder. For example, when using a Sn—Bi solder alloy, preheating may be performed at a temperature of 90 to 120 ° C. for 60 to 120 seconds, and the peak temperature may be set to 150 to 180 ° C.

In addition, the connection method using the solder composition of the present invention is not limited to the connection method described above, and modifications, improvements and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the connection method, the wiring board and the electronic component are bonded by the reflow process, but the present invention is not limited to this. For example, instead of the reflow process, the wiring board and the electronic component may be bonded by a process of heating the solder composition using laser light (laser heating process). In this case, the laser light source is not particularly limited, and can be appropriately selected according to the wavelength matched to the metal absorption band. As the laser light source, for example, a solid laser (ruby, glass, YAG, etc.), semiconductor laser (GaAs, InGaAsP, etc.), (such as a dye) liquid laser, a gas laser (He-Ne, Ar, CO 2, etc. excimer) is Can be mentioned.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. In addition, the material used in the Example and the comparative example is shown below.
((A) component)
Lead-free solder powder A: surface-treated solder powder obtained in Preparation Example 1 below, average particle size 10 μm, solder melting point 139 ° C., solder composition 42 Sn / 58 Bi
Lead-free solder powder B: surface-treated solder powder obtained in Preparation Example 2 below, average particle diameter 5 μm, solder melting point 139 ° C., solder composition 42 Sn / 58 Bi
Lead-free solder powder C: average particle diameter 10 μm, melting point of solder 139 ° C., solder composition 42 Sn / 58 Bi
Lead-free solder powder D: average particle diameter 21 μm, melting point of solder 139 ° C., solder composition 42 Sn / 58 Bi
((B) component)
Epoxy resin: bisphenol A type and bisphenol F type liquid epoxy resin, trade name “EXA-830LVP”, manufactured by DIC (component (C))
Glycidyl group-containing compound A: phenyl glycidyl ether, viscosity is 8 mPa · s, trade name “EX-141”, glycidyl group-containing compound B manufactured by Nagase ChemteX Corporation: 1,4-cyclohexyldimethanol diglycidyl ether, viscosity is 50 mPa · s s, trade name “EP-4085S”, manufactured by ADEKA (component (D1))
Dicarboxylic acid: adipic acid (component (D2))
Organic acid amine salt: n-butylamine adipate, softening point is 120 ° C
((E) component)
Hardener A: 2P4MHZ-PW, Shikoku Kasei Kogyo Co., Ltd. B: 2MZA-PW, Shikoku Kasei Kogyo Co., Ltd. (component (F))
Thixo: Brand name “Gelall D”, manufactured by Shin Nippon Rika Co., Ltd. (other ingredients)
Antifoaming agent: Trade name “Floren AC326F”, manufactured by Kyoeisha Chemical Co., Ltd.

[Production Example 1]
A surface treatment solution is prepared by adding 150 g of 12-hydroxystearic acid and 1000 mL of industrial ethanol to a flask, heating to 50 ° C., stirring at a rotation speed of 150 rpm under nitrogen atmosphere conditions, and dissolving 12-hydroxystearic acid. Got. To this surface treatment solution, 1000 g of solder powder to be treated (alloy composition: 42 Sn / 58 Bi, average particle size: 10 μm, solder melting point: 139 ° C.) was added and stirred for 3 hours. The solder powder after stirring was suction filtered while being washed with isopropyl alcohol, and then dried in an air drying oven at 70 ° C. to obtain a surface-treated solder powder.
[Production Example 2]
In the same manner as in Production Example 1, except that the solder powder to be treated (alloy composition: 42Sn / 58Bi, average particle size: 5 μm, solder melting point: 139 ° C.) was used instead of the solder powder to be treated used in Production Example 1. Thus, a surface-treated solder powder was obtained.

[Example 1]
Epoxy resin 61.8 mass%, thixotropic agent 1.2 mass%, glycidyl group-containing compound A 20 mass%, dicarboxylic acid 3.5 mass%, organic acid amine salt 5 mass%, curing agent A4 mass%, curing agent B4 mass % And 0.5% by mass of an antifoaming agent were put into a container and premixed with a stirrer, and then mixed and dispersed at room temperature using a three roll to obtain a thermosetting resin composition.
Next, 20% by mass of the obtained thermosetting resin composition and 80% by mass of lead-free solder powder A (100% by mass in total) were put into a container and mixed in a kneader to prepare a solder composition. .

[Examples 2-3]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
[Comparative Examples 1-4]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 2.

<Evaluation of solder composition>
Evaluation of solder composition performance (solder wettability, solder meltability, resin curability, insulation, viscosity, applicability with a jet dispenser (dischargeability), pot life) by the following methods Or measured. The obtained results are shown in Tables 1 and 2.
(1) Solder wettability to a white substrate A solder composition is placed on a white substrate (30 mm × 30 mm × 0.3 mmt) so as to be 0.30 g ± 0.03 g, and then heated to 160 ° C. with a hot plate. Heat for 30 seconds. The height (H) of the solder spread with a micrometer is measured, and the spread ratio (Sr) is obtained from the following formula (F1). This operation is repeated five times, and the average value is defined as the spread rate of the sample.
Sr = (D−H) / D × 100 (F1)
D = 1.24V ^1/3 (F2)
Sr: Spread rate (%)
H: Expanded solder height (mm)
D: Diameter when the solder used in the test is regarded as a ball (mm)
V: Mass / density of solder used in test The solder wettability to the white substrate was evaluated according to the following criteria based on the results of the spreading ratio (Sr).
○: 75% or more.
Δ: 70% or more and less than 75%.
X: Less than 70%.
(2) Solder meltability A solder composition was applied onto a wiring board (on the land) having a plurality of lands having a diameter of 1 mm to 2 mm as a circuit pattern (thickness: 0.1 mm). Thereafter, a reflow process was performed under the conditions of a temperature rise of 1.8 ° C./s and a hold of 160 ° C. for 4 minutes to produce a test substrate. About the obtained test board, the meltability of the solder was evaluated according to the following criteria.
○: There is no solder ball.
Δ: There are 5 or less solder balls.
X: 6 or more solder balls or solder does not melt.
(3) Resin curability The solder composition was applied onto a substrate and subjected to a reflow process under the conditions of a temperature increase of 1.8 ° C./s and a temperature of 160 ° C. for 4 minutes to prepare a test substrate. The hardness of the resin after heating was observed, and the resin curability was evaluated according to the following criteria.
○: Resin is hard.
Δ: When the resin is pressed hard, a mark remains.
X: Resin is soft and has tack.
(4) Insulation The insulation was evaluated according to the method described in JIS Z 3284. That is, a solder composition is printed on a copper foil land of a JIS2 type substrate (on a glass epoxy resin substrate having a copper foil land having a conductor width of 0.318 mm and a conductor interval of 0.318 mm) using a 100 μmt metal mask, A reflow process was performed under conditions of a temperature increase of 1.8 ° C./s and a temperature of 160 ° C. for 4 minutes to prepare a test substrate. A 50 V voltage was applied to the test substrate in 85 ° C. and 85% RH (relative humidity), and the insulation resistance value between the copper foil land surfaces after 168 hours was measured by applying 100 V. And insulation was evaluated according to the following criteria.
○: Insulation resistance value is 1.0 × 10 ⁹ Ω or more.
Δ: The insulation resistance value is 1.0 × 10 ⁸ Ω or more and less than 1.0 × 10 ⁹ Ω.
×: Insulation resistance value is less than 1.0 × 10 ⁸ Ω.

(5) Viscosity test (viscosity and thixo index)
In accordance with JIS Z3284 appendix 6, measurement was performed with an E-type viscometer. The viscosity value η is read at a rotation speed of 10 rpm and a temperature of 25 ° C. Then, the viscosity was evaluated according to the following criteria based on the result of the viscosity value η.
A: 10 Pa · s or more and less than 30 Pa · s.
○: 30 Pa · s or more and less than 60 Pa · s.
Δ: 60 Pa · s or more and less than 100 Pa · s.
X: Less than 10 Pa · s or 100 Pa · s or more.
Further, in the same manner as described above, the viscosity value when the rotation speed was adjusted to 10 rpm (10 rpm viscosity) and the viscosity value when the rotation speed was adjusted to 2.5 rpm (2.5 rpm viscosity) were read. And the thixo index was computed based on the following formula.
Thixo index = log [(2.5rpm viscosity) / (10rpm viscosity)] / log [20/5]
(6) Applicability (jetting properties) with a jet dispenser
Discharge was performed with a jet dispenser having a nozzle having a diameter of 0.15 mmφ, and the applicability (dischargeability) was evaluated according to the following criteria.
(Double-circle): It can discharge with a favorable shape (spherical shape).
○: Can be discharged in a good shape.
Δ: An ellipse is formed, but ejection is possible.
X: Discharge is not possible.
(7) Pot life After standing at a temperature of 40 ° C. for 12 hours, the viscosity is measured in the same manner as the viscosity measurement in the viscosity test (5). Then, when the viscosity value in the viscosity test (5) is the initial viscosity value η1 and the viscosity value after standing for 12 hours at a temperature of 40 ° C. is the viscosity value η2 after standing, the rate of change in viscosity from the following formula (F3) Ask for.
Rate of change (%) = {(η2−η1) / η1} × 100 (F3)
And pot life was evaluated according to the following reference | standard based on the result of change rate.
○: Change rate is 20% or less.
X: The rate of change is more than 20%.

As is clear from the results shown in Tables 1 and 2, the solder compositions of the present invention (Examples 1 to 4) are solder wettability to the white substrate, solder meltability, resin curability, insulation, It was confirmed that the viscosity, applicability with a jet dispenser, and pot life were all good. Therefore, it was confirmed that the solder composition of the present invention is excellent in applicability, resin curability, pot life and solder meltability when the solder composition is applied to a fine pattern by a jet dispenser.
On the other hand, it was found that when a solder composition containing a solder powder having an average particle diameter of 10 μm that was not subjected to surface treatment was used (Comparative Example 1), the solder meltability was insufficient. Moreover, when the solder composition containing a solder powder with an average particle diameter of 21 μm and a large particle diameter was used (Comparative Example 1), it was found that the applicability with a jet dispenser was insufficient. Furthermore, in the case of using a solder composition containing a solder powder having an average particle diameter of 10 μm that has not been surface-treated and having an increased amount of activator (Comparative Example 3), insulation and pot life are poor. It turned out to be sufficient. Moreover, when using the solder composition which does not contain a glycidyl group containing composition (comparative example 4), since the viscosity was too high, it turned out that the applicability | paintability with a jet dispenser is inadequate.

  The solder composition for applying a fine pattern of the present invention can be suitably used as a technique for connecting an electronic component and a wiring board.

Claims (5)

A solder composition for applying a fine pattern to a fine pattern by a jet dispenser,
(A) 70 to 85% by mass of lead-free solder powder having a melting point of 240 ° C. or lower, (B) an epoxy resin, (C) a monomer, and a glycidyl group-containing compound that is liquid at 25 ° C., D) 15% by mass to 30% by mass of a thermosetting resin composition containing an activator, (E) a curing agent and (F) a thixotropic agent,
The lead-free solder powder (A) has an aliphatic monocarboxylic acid or aromatic monocarboxylic acid having one or more hydroxyl groups in one molecule attached to the surface of the solder powder to be treated, adsorbed thereon, or , Which are combined,
The average particle diameter of the (A) lead-free solder powder state, and are more 12μm or less 1 [mu] m,
A solder composition for applying a fine pattern, wherein the solder composition for applying a fine pattern has a viscosity at 25 ° C. measured by an E-type viscometer of 10 Pa · s or more and less than 60 Pa · s . In the solder composition for applying a fine pattern according to claim 1,
The (C) glycidyl group-containing compound has a viscosity of 1 mPa · s or more and 2000 mPa · s or less measured at 25 ° C. with an E-type viscometer. . In the solder composition for applying a fine pattern according to claim 1 or 2,
Said (A) lead-free solder powder consists of an alloy of tin and bismuth. The solder composition for fine pattern application | coating characterized by the above-mentioned. In the solder composition for fine pattern application according to any one of claims 1 to 3,
(B) The epoxy resin is a liquid at 25 ° C. The solder composition for applying a fine pattern. In the solder composition for fine pattern application according to any one of claims 1 to 4,
Said (D) activator contains (D1) dicarboxylic acid and (D2) organic acid amine salt. The solder composition for fine pattern application | coating characterized by the above-mentioned.