JP6522674B2 - Flux composition, solder paste and electronic circuit board - Google Patents

Description

  The present invention relates to a flux composition, a solder paste and an electronic circuit board.

  In order to bond electronic components to an electronic circuit formed on a substrate such as a printed wiring board or a silicon wafer, a solder bonding method using a solder alloy is employed. Conventionally, it has been common to use lead as the solder alloy. However, since the use of lead is restricted by the RoHS directive and the like from the viewpoint of environmental load, in recent years, solder bonding using a so-called lead-free solder alloy containing no lead is becoming popular.

  As the lead-free solder alloy, for example, Sn-Cu-based, Sn-Ag-Cu-based, Sn-Bi-based, and Sn-Zn-based solder alloys are often used. Among them, Sn-3Ag-0.5Cu solder alloy is often used in consumer electronic devices used in TVs, mobile phones and the like and in-vehicle electronic devices mounted in automobiles.

  Also, in recent years, as in the case of electronic circuit boards used in electronic control devices, for example, the temperature difference between the engine compartment, engine directly mounted, or electromechanical integration with a motor is particularly severe (for example, -30 ° C to 110 ° C, -40 ° C) C., a temperature difference of -40.degree. C. to 150.degree. C.), and the placement of the electronic circuit board in a severe environment where vibration load is additionally applied are studied and put into practical use.

  Patent documents 1 to 7 disclose that a solder alloy used for a vehicle electronic circuit board which is placed in such an environment with a large temperature difference is a highly oxidized In, Bi and Sb for the purpose of improving the mechanical characteristics. Methods of adding such elements are disclosed.

  Moreover, in patent document 8, in order to suppress the time-dependent change of the solder paste using the solder alloy containing the element with high oxidation property, the flux with solder paste uses a dicarboxylic acid having 3 to 5 carbon atoms and 15 carbon atoms as an activator. A method is disclosed in which -20 dicarboxylic acids are used in combination.

JP-A-5-228685 Unexamined-Japanese-Patent No. 9-326554 Japanese Patent Laid-Open No. 2000-190090 JP 2000-349433 A JP 2008-28413 A International Publication Pamphlet WO2009 / 011341 JP 2012-81521 A Japanese Patent Application Publication No. 2003-260589

However, Sn-3Ag-0.5Cu-based solder alloy contains solidus temperature and liquidus temperature higher by about 40 ° C or more than conventional Sn-Pb eutectic solder, and also contains Cu with high viscosity. ing. Therefore, if the activator contained in the flux composition can not sufficiently remove the oxide film of the Sn-3Ag-0.5Cu-based solder alloy, voids are generated during the bonding, particularly when the solder paste is used for the solder paste. There is a possibility that voids may easily remain in the formed solder joint.
In particular, when an element having a high oxidizing property such as Bi, In and Sb is added to a Sn-Ag-Cu solder alloy, the surface oxide film tends to be more difficult to remove sufficiently than a Sn-3Ag-0.5Cu solder alloy. . Therefore, if the activity of the flux composition used is insufficient, particularly when solder bonding using this as a solder paste, the viscosity of the alloy powder consisting of the molten solder alloy does not easily decrease, and voids are formed in the solder joint. There is a problem that the alloy powder tends to remain, and the alloy powders are less likely to be aggregated or fused, and solder balls are easily generated. Solder balls cause open defects and shorts, such as non-fusion of electrode paste of an electronic component mounted on a substrate and solder paste. Therefore, solder balls are particularly required for automotive electronic circuit boards requiring high reliability. Control of the occurrence of is one of the important issues.
Also in solder balls used for solder bonding such as Ball Grid Array (BGA) parts, if the removal of the oxide film of the solder alloy is insufficient, bonding failure between the electrode on the substrate and the electrode on the electronic component easily occurs. Become. In particular, in the case of using a solder ball in which an element having a high oxidizing property such as Bi, In and Sb is added to a Sn—Ag—Cu-based solder alloy, the above-mentioned joint failure is more likely to occur.

  Even in the case where an activator having a strong activity and a activator having a weak activity are used in combination to suppress the generation of solder balls and joint defects due to insufficient removal of the surface oxide film of the solder alloy described above, If the combination alone is used, the oxidizing action to the solder alloy containing Bi, In, Sb, etc. becomes insufficient, and there is a possibility that it is difficult to sufficiently exhibit the effect of suppressing the generation of solder balls and voids and bonding defects.

  The present invention solves the above-described problems, and even when using a solder alloy containing a strongly oxidizing alloy element, it is possible to suppress void generation in a solder joint, generation of solder balls, and solder joint defects while being good. It is an object of the present invention to provide an electronic circuit board having a flux composition capable of exhibiting excellent printability, a solder paste, and a solder joint formed using the same.

(1) A flux composition according to the present invention is a flux composition comprising (A) a base resin, (B) an activator, (C) a thixo agent, and (D) a solvent, wherein the activator The compounding amount of (B) is 4.5% by mass or more and 35% by mass or less based on the total amount of the flux composition, and as the activator (B), (B-1) linear saturated having 3 to 4 carbon atoms The dicarboxylic acid is 0.5% to 3% by mass with respect to the total amount of the flux composition, and (B-2) the dicarboxylic acid having 5 to 13 carbon atoms is 2% to 15% by mass to the total amount of the flux composition Hereinafter, and (B-3) is characterized in that it contains a dicarboxylic acid having 20 to 22 carbon atoms in an amount of 2% by mass to 15% by mass with respect to the total amount of the flux composition.

(2) In the constitution described in the above (1), the linear saturated dicarboxylic acid having 3 to 4 carbon atoms (B-1) is at least one of malonic acid and succinic acid, and the carbon number is 5 13 dicarboxylic acid (B-2) is glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, 2-methyl azelaic acid, sebacic acid, undecane diacid, dodecane diacid and tridecanedioic acid or al The dicarboxylic acid (B-3) having at least one selected and having a carbon number of 20 to 22 is eicosadic acid, 8-ethyloctadecanedioic acid, 8,13-dimethyl-8,12-eicosadienedic acid and 11 It is characterized in that it is at least one selected from vinyl-8-octadecene diacid.

(3) In the constitution described in the above (1) or (2), the dicarboxylic acid (B-3) having 20 to 22 carbon atoms is characterized in that it is liquid or semisolid at normal temperature. .

(4) The flux composition according to the present invention has the feature described in any one of the above (1) to (3), further including an antioxidant.

(5) In the constitution according to any one of (1) to (4) above, the base resin (A) is characterized by containing (A-1) a rosin resin.

(6) In the configuration described in (5) above, the base resin (A) further includes (A-2) a synthetic resin.

(7) The solder paste according to the present invention is characterized by containing the flux composition according to any one of the above (1) to (6) and a solder alloy powder.

(8) In the configuration described in the above (7), the solder alloy powder is characterized by being composed of Sn and an alloy containing at least one selected from Pb, Ag, Bi, In and Sb.

(9) The electronic circuit board according to the present invention is characterized by having a solder joint formed using the solder paste according to (7) or (8) above.

  The flux composition of the present invention, the solder paste, and the electronic circuit board having a solder joint formed using the same have void formation in the solder joint even when using a solder alloy containing a strongly oxidizing alloy element. Thus, good printability can be exhibited while suppressing generation of solder balls and solder joint defects.

The test board which concerns on the Example and comparative example of this invention WHEREIN: The photograph image | photographed from the chip component side using the X-ray transmission apparatus showing the area | region under the electrode of chip components, and the area | region in which the fillet is formed.

  Hereinafter, one embodiment of the flux composition, solder paste and electronic circuit board of the present invention will be described in detail. In addition, it is of course that the present invention is not limited to the following embodiments.

(1) Flux Composition The flux composition of the present embodiment preferably contains (A) a base resin, (B) an activator, (C) a thixo agent, and (D) a solvent.

(A) Base resin As said base resin (A), it is preferable to use at least one of (A-1) rosin type-resin and (A-2) synthetic resin, for example.
Examples of the rosin resin (A-1) include rosin such as tall oil rosin, gum rosin, wood rosin; rosin polymerization, hydrogenation, heterogeneity, acrylation, maleation, esterification or phenol addition reaction, etc. And rosin derivatives obtained by reacting the above rosins or rosin derivatives with unsaturated carboxylic acids (acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, etc.), and modified rosin resins obtained by Diels-Alder reaction. Among these, modified rosin resin is particularly preferably used, and hydrogenated acrylic acid modified rosin resin obtained by reacting acrylic acid to be hydrogenated is particularly preferably used. In addition, you may use these individually by 1 type or in mixture of multiple types.

  The acid value of the rosin resin (A-1) is preferably 140 mg KOH / g to 350 mg KOH / g, and the weight average molecular weight thereof is preferably 200 Mw to 1,000 Mw.

  Examples of the synthetic resin (A-2) include acrylic resin, styrene-maleic acid resin, epoxy resin, urethane resin, polyester resin, phenoxy resin, terpene resin, polyalkylene carbonate, rosin resin having a carboxyl group, and dimer acid A derivative compound formed by dehydration condensation with a derivative flexible alcohol compound can be mentioned. In addition, you may use these individually by 1 type or in mixture of multiple types. Among these, acrylic resin is particularly preferably used.

  The acrylic resin can be obtained, for example, by homopolymerizing a (meth) acrylate having an alkyl group having 1 to 20 carbon atoms, or copolymerizing a monomer containing the acrylate as a main component. Among such acrylic resins, acrylic resins obtained by polymerizing methacrylic acid and a monomer containing a monomer having two linear C 2 to C 20 saturated alkyl groups having a linear carbon chain are particularly preferably used. Be In addition, the said acrylic resin may be used individually by 1 type or in mixture of multiple types.

Regarding the derivative compound (hereinafter referred to as "rosin derivative compound") formed by dehydration condensation of a rosin resin having a carboxyl group and a dimer acid derivative soft alcohol compound, first, as a rosin resin having a carboxyl group, for example, Tall oil rosins, gum rosins, rosins such as wood rosins; hydrogenated rosins, polymerized rosins, heterogeneous rosins, rosin derivatives such as acrylic acid modified rosins, and acrylic acid modified rosins, and maleic acid modified rosins, etc. If it is, it can be used. Moreover, you may use these individually by 1 type or in mixture of multiple types.
Next, as the dimer acid derivative flexible alcohol compound, for example, a compound derived from a dimer acid such as dimer diol, polyester polyol, polyester dimer diol and the like having an alcohol group at the end, etc. may be mentioned. For example, PRIPOL2033, PRIPLAST 3197, and PRIPLAST 1838 (above, manufactured by Croda Japan Ltd.) can be used.
The rosin derivative compound is obtained by dehydration condensation of a rosin-based resin having the carboxyl group and the dimer acid derivative soft alcohol compound. A commonly used method can be used as a method of this dehydration condensation. In addition, the preferable mass ratio at the time of dehydrating condensation of the rosin-based resin having the carboxyl group and the dimer acid derivative flexible alcohol compound is 25:75 to 75:25, respectively.

  The acid value of the synthetic resin (A-2) is preferably 0 mg KOH / g to 150 mg KOH / g, and the mass average molecular weight thereof is preferably 1,000 Mw to 30,000 Mw

  The amount of the base resin (A) is preferably 10% by mass to 60% by mass, and more preferably 30% by mass to 55% by mass, based on the total amount of the flux composition.

  When using the said rosin-type resin (A-1) independently, it is preferable that the compounding quantity is 20 mass% or more and 60 mass% or less with respect to the flux composition whole quantity, and is 30 mass% or more and 55 mass% or less Is more preferred. By making the compounding quantity of rosin type-resin (A-1) into this range, favorable solderability can be implement | achieved.

  Moreover, when using the said synthetic resin (A-2) independently, it is preferable that the compounding quantity is 10 mass% or more and 60 mass% or less with respect to the flux composition whole quantity, and is 15 mass% or more and 50 mass% or less Is more preferred.

  Furthermore, when using the rosin resin (A-1) and the synthetic resin (A-2) in combination, the compounding ratio is preferably rosin resin: synthetic resin = 20:80 to 50:50, and 25 More preferably, it is from 75 to 40:60.

  In addition, as said base resin (A), rosin-type resin (A-1) independent or the combined use of an acrylic resin as rosin-type resin (A-1) and a synthetic resin (A-2) is preferable.

(B) Activator As the activator (B), (B-1) a linear saturated dicarboxylic acid having 3 to 4 carbon atoms with respect to the total amount of the flux composition of 0.5% by mass or more and 3% by mass or less, (B-2) a dicarboxylic acid having 5 to 13 carbon atoms with respect to the total amount of the flux composition of 2% to 15% by mass, and (B-3) a dicarboxylic acid having a carbon number of 20 to 22 and a flux composition It is preferable to contain 2 mass% or more and 15 mass% or less with respect to the total amount.
It is preferable that it is 4.5 to 35 mass%, and, as for the compounding quantity of the said activator (B), it is more preferable that it is 4.5 to 20 mass%.

The linear saturated dicarboxylic acid (B-1) having 3 to 4 carbon atoms is preferably at least one of malonic acid and succinic acid.
Moreover, the more preferable compounding quantity of the said C3-C4 linear saturated dicarboxylic acid (B-1) is 0.5 mass% to 2 mass% with respect to the flux composition whole quantity.

The carbon chain in the dicarboxylic acid (B-2) having 5 to 13 carbon atoms may be linear or branched, but glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid , 2-methyl azelaic acid, sebacic acid, undecanoic diacid, is preferably at least one selected from dodecanoic diacid and tridecanedioic acid. Among these, adipic acid, suberic acid, sebacic acid and dodecanedioic acid are particularly preferably used.
Moreover, the more preferable compounding quantity of the said C5-C13 dicarboxylic acid (B-2) is 3 mass% to 12 mass% with respect to the flux composition whole quantity.

  The carbon chain in the dicarboxylic acid (B-3) having a carbon number of 20 to 22 may be either linear or branched, but eicosaic acid, 8-ethyloctadecanedioic acid, 8, 13 It is preferable that it is at least one selected from -dimethyl-8,12-eicosadiene diacid and 11-vinyl-8-octadecene diacid.

  Moreover, as said C20-C22 dicarboxylic acid (B-3), what is liquid or semisolid at normal temperature is used more preferably. In the present specification, normal temperature refers to a range of 5 ° C. to 35 ° C. The semi-solid state refers to a state corresponding to a liquid state and a solid state, and refers to a state in which a part has fluidity and a state in which there is no fluidity but is deformed when an external force is applied. As such a dicarboxylic acid (B-3) having 20 to 22 carbon atoms, particularly, 8-ethyloctadecanedioic acid is preferably used.

  Moreover, the more preferable compounding quantity of the said C20-C22 dicarboxylic acid (B-3) is 3 mass% to 12 mass% with respect to the flux composition whole quantity.

  By blending, as the activator (B), a dicarboxylic acid corresponding to the range of the carbon number of each of the activators (B-1), (B-2) and (B-3) according to the above blending amount, The flux composition of the embodiment can sufficiently remove the oxide film even when using a solder alloy to which a highly oxidizing element such as Bi, In and Sb is added. Therefore, when this is used for a solder paste, it is possible to improve the cohesion of alloy powders comprising the above-mentioned solder alloy and reduce the viscosity at the time of melting the solder, thereby generating solder balls and solder joints generated at the side of electronic components. Voids can be reduced. In addition, even in the case of performing solder bonding using solder balls, since surface oxidation of the solder balls can be sufficiently suppressed, bonding failure between the electrode on the substrate and the electrode of the electronic component can be suppressed.

In particular, when used for solder paste, when the linear saturated dicarboxylic acid (B-1) having 3 to 4 carbon atoms is kneaded with the flux composition and the alloy powder, a part thereof is the same as that of the alloy powder. The surface may be coated to inhibit its surface oxidation. Further, since the dicarboxylic acid (B-3) having 20 to 22 carbon atoms is slow in reactivity, it is stable also in the printing process of solder paste on a substrate over a long time, and it is difficult to volatilize even during reflow heating Thus, the surface of the molten alloy powder can be coated to suppress oxidation by the reduction action.
However, the C20 to C22 dicarboxylic acid (B-3) has low activity, and the oxidation of the surface of the alloy powder is caused only by the combination with the C3 to C4 linear saturated dicarboxylic acid (B-1). There is a possibility that the film can not be removed sufficiently. Therefore, particularly when a powder of a solder alloy containing Bi, In, Sb, etc. is used, the oxidation action to the alloy powder becomes insufficient, and it is difficult to sufficiently exhibit the effect of suppressing solder balls and voids.

  However, the flux composition of the present embodiment is a dicarboxylic acid having 5 to 13 carbon atoms which exerts a strong activity during preheating to the activators of (B-1) and (B-3) (B-2) Since a predetermined amount of C) is contained, the reliability of the flux residue can be ensured, and the oxide film can be sufficiently removed even when such an alloy powder is used. Therefore, the flux composition of the present embodiment improves the cohesion of the alloy powders and reduces the viscosity at the time of melting the solder, thereby causing voids generated in the solder ball and the solder joint portion at the side of the electronic component. Can be reduced. Further, due to such an action, even when the flux composition is used for solder balls, it is possible to suppress the bonding failure between the electrode on the substrate and the electrode on the electronic component.

  That is, in the flux composition of the present embodiment, dicarboxylic acids corresponding to the specific carbon number range of the activators (B-1), (B-2) and (B-3) are combined in a predetermined blending amount By blending it, it is possible to exhibit a redox effect to a solder alloy better than the combination of so-called short chain dicarboxylic acid and long chain dicarboxylic acid. Moreover, the flux composition which combined such an activator can also exhibit favorable printability.

Other active agents can be blended with the flux composition of the present embodiment as long as the above effects are not inhibited.
Examples of such other activators include amine salts (inorganic acid salts and organic acid salts) such as hydrogen halides of organic amines, organic acids, organic acid salts, organic amine salts and the like. Specifically, diphenyl guanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salt, dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, 1,4- Examples thereof include cyclohexanedicarboxylic acid, anthranilic acid, picolinic acid and 3-hydroxy-2-naphthoic acid. You may use these individually by 1 type or in mixture of multiple types.
It is preferable that the compounding quantity of the said other activator is more than 0 mass% and 20 mass% or less with respect to the flux composition whole quantity.

(C) Thixo agent Examples of the thixo agent (C) include hydrogenated castor oil, fatty acid amides, saturated fatty acid bisamides, oxyfatty acid and dibenzylidene sorbitols. You may use these individually by 1 type or in mixture of multiple types.
The compounding amount of the thixotropic agent (C) is preferably 2% by mass to 15% by mass, and more preferably 2% by mass to 10% by mass, with respect to the total amount of the flux composition.

(D) Solvent As the solvent (D), for example, isopropyl alcohol, ethanol, acetone, toluene, xylene, ethyl acetate, ethyl cellosolve, butyl cellosolve, hexyl diglycol, (2-ethylhexyl) diglycol, phenyl glycol, butyl carbitol And octanediol, α-terpineol, β-terpineol, tetraethylene glycol dimethyl ether, tris (2-ethylhexyl) trimellitate, bisisopropyl sebacate and the like. You may use these individually by 1 type or in mixture of multiple types.
The content of the solvent (D) is preferably 20% by mass to 50% by mass, and more preferably 25% by mass to 40% by mass, based on the total amount of the flux composition.

An antioxidant can be added to the flux composition of the present embodiment for the purpose of suppressing the oxidation of the solder alloy. Examples of the antioxidant include hindered phenol-based antioxidants, phenol-based antioxidants, bisphenol-based antioxidants, polymer-type antioxidants, and the like. Among them, hindered phenol-based oxidizing agents are particularly preferably used. You may use these individually by 1 type or in mixture of multiple types.
Although the compounding quantity of the said antioxidant is not specifically limited, Generally, it is preferable that they are 0.5 mass% or more and about 5 mass% or less with respect to the flux composition whole quantity.

Additives can be blended into the flux composition of the present embodiment as required. As said additive, an antifoamer, surfactant, a matting agent, an inorganic filler etc. are mentioned, for example. You may use these individually by 1 type or in mixture of multiple types.
The blending amount of the additive is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 15% by mass or less based on the total amount of the flux composition.

(2) Solder paste It is preferable that the solder paste of this embodiment contains the said flux composition and the solder alloy powder which consists of a solder alloy.

<Solder alloy powder>
As the solder alloy powder, a lead-free solder alloy powder is preferably used. The solder paste according to the present embodiment is not limited to the components of the solder alloy to be used, and even when the components having high oxidizing properties such as Bi, In and Sb are used, void generation in the solder joint, solder ball Good printability can be exhibited while suppressing occurrence and solder joint defects.

  Examples of alloys that can be used for the solder alloy powder include, for example, Sn and Ag, Bi, In, Sb, Cu, Zn, Ga, Ge, Au, Pa, Ni, Cr, Al, P, Cd, Tl, Alloys containing at least one selected from Se, Ti, Si, Mg and the like can be mentioned. In addition, even if it is except the element quoted above, it is possible to use for the combination.

The solder paste of this embodiment can be obtained, for example, by kneading the flux composition and the solder alloy powder.
The compounding ratio of the solder alloy powder to the flux composition is preferably 65:35 to 95: 5 in the ratio of solder alloy powder: flux composition. The more preferable blending ratio is 85:15 to 93: 7, and the particularly preferred blending ratio is 87:13 to 92: 8.

  The average particle diameter of the alloy powder is preferably 1 μm to 40 μm, more preferably 5 μm to 35 μm, and particularly preferably 10 μm to 30 μm.

(3) Electronic Circuit Board The electronic circuit board of the present embodiment includes the solder joint portion formed using the solder paste and the flux residue (in the present specification, the solder joint portion and the flux residue are combined to form a “solder joint It is preferable to have a body. The said electronic circuit board forms an electrode and a solder resist film in the predetermined position on a board | substrate, for example, prints the solder paste of this embodiment using the mask which has a predetermined pattern, and the electronic component which adapts the said pattern It mounts in a predetermined position and is produced by reflowing this.
In the electronic circuit board manufactured in this manner, a solder joint is formed on the electrode, and the solder joint electrically joins the electrode and the electronic component. And, on the substrate, flux residue adheres so as to adhere to at least a solder joint.

The solder joint is formed using the above-mentioned solder paste in the electronic circuit board of the present embodiment. Therefore, even when using a solder alloy containing an alloy element having a strong oxidizing property, generation of voids and solder in the solder joint Good printability can be exhibited while suppressing the generation of balls.
An electronic circuit board having such a solder joint can be suitably used also for an electronic circuit board which is required to have high reliability such as a car-mounted electronic circuit board.

  Further, by incorporating such an electronic circuit board, an electronic control device is manufactured.

  Hereinafter, the present invention will be described in detail by way of examples and comparative examples. The present invention is not limited to these examples.

<Synthesis of acrylic resin>
A solution was prepared by mixing 10% by mass of methacrylic acid, 51% by mass of 2-ethylhexyl methacrylate, and 39% by mass of lauryl acrylate.
Thereafter, 200 g of diethylhexyl glycol was charged into a 500 ml four-necked flask equipped with a stirrer, a reflux condenser and a nitrogen introduction pipe, and this was heated to 110 ° C. Subsequently, 0.2% by mass of dimethyl 2,2'-azobis (2-methylpropionate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) as an azo radical initiator is added to 300 g of the solution described above. The mass% was added to dissolve it.
This solution was added dropwise to the four-necked flask over 1.5 hours, and the components in the four-necked flask were stirred at 110 ° C. for 1 hour to complete the reaction to obtain a synthetic resin. In addition, the weight average molecular weight of the synthetic resin was 7,800 Mw, the acid value was 40 mg KOH / g, and the glass transition temperature was -47 ° C.

  Each component described in Tables 1 to 4 was kneaded to obtain each flux composition according to Examples 1 to 16 and Comparative Examples 1 to 18. In addition, unless otherwise indicated, the unit of the compounding quantity is a mass% in Tables 1 to 4.

* 1 Arakawa Chemical Industries, Ltd. hydro-acid modified rosin * 2 Nippon Kasei Co., Ltd. hexamethylene bishydroxystearic acid amide * 3 BASF Japan Co., Ltd. hindered phenolic antioxidant

<Preparation of solder paste>
The solder composition according to Examples 1 to 16 and Comparative Examples 1 to 18 was manufactured by mixing the flux composition in an amount of 88.8 mass% with the powders of the following solder alloys: 11.2% by mass.
Example 1, Comparative Example 4: Sn-3Ag-0.5Cu Solder Alloy Example 2, Comparative Example 5: Sn-3Ag-59Bi Solder Alloy Example 3, Comparative Example 6: Sn-2Ag-58Bi-0.5Cu- 0.1 Ni solder alloy Example 4, Comparative Example 7: Sn-3Ag-0.5Cu-3.5Bi-3Sb-0.04 Ni-0.01Co solder alloy Examples 5 to 16, Comparative Examples 1 to 3 and 8 18: Sn-3Ag-0.5Cu-0.5Bi-2.5Sb-4In-0.15Ni solder alloy * The particle size of all solder alloy powders is 20 μm to 36 μm

(1) Void test A chip part of 2.0 mm × 1.2 mm size, a solder resist having a pattern capable of mounting the chip part of the size, and an electrode (1.25 mm × 1.0 mm) connecting the chip parts And a 150 μm thick metal mask having the same pattern.
Each solder paste was printed on the glass epoxy substrate using the metal mask, and the chip parts were mounted.
Thereafter, the respective glass epoxy substrates are heated using a reflow furnace (product name: TNP-538EM, manufactured by Tamura Corporation), and solder bonding is performed to electrically bond the glass epoxy substrate and the chip component to each other. The chip parts were mounted. Reflow conditions at this time are: preheat 170 ° C. to 190 ° C. for 110 seconds, peak temperature 245 ° C., 200 ° C. or more for 65 seconds, 220 ° C. or more for 45 seconds, peak temperature to 200 ° C. The cooling rate was 3 ° C. to 8 ° C./sec, and the oxygen concentration was set to 1500 ± 500 ppm.
Next, the surface condition of each test substrate is observed with an X-ray transmission device (product name: SMX-160E, manufactured by Shimadzu Corporation), and the area under the electrode of the chip component at 40 lands in each test substrate (Figure Area ratio of void occupying area (a) surrounded by broken line of 1 (ratio of total area of void. The same applies hereinafter) and area where fillet is formed (area surrounded by broken line in FIG. 1 (b)) The average value of the area ratio of voids occupying in was determined and evaluated as follows. The results are shown in Tables 5 to 8, respectively.
A: The average value of the area ratio of voids is 3% or less, and the effect of suppressing void formation is extremely good. O: The average value of the area ratio of voids is more than 3% and 5% or less. Good: Average value of area ratio of voids is more than 5% and 8% or less, and the effect of suppressing void generation is sufficient. ×: Average value of area ratio of voids exceeds 8%, the effect of suppressing void generation is insufficient

(2) Solder ball test Each test substrate under the same conditions as the above-mentioned (1) void test except that the peak temperature of the reflow condition is 260 ° C., the time of 200 ° C. or more is 70 seconds, and the time of 220 ° C. or more is 60 seconds. The surface condition of each test substrate is observed with an X-ray transmission device (product name: SMX-160E, manufactured by Shimadzu Corporation), and the number of solder balls generated around the chip component and the lower surface is counted. And evaluated as follows. The results are shown in Tables 5 to 8, respectively.
:: The number of balls generated per 10 2.0 mm × 1.2 mm chip resistance is 0 ○: The number of balls generated per 10 2.0 mm × 1.2 mm chip resistance is more than 0 and 5 or less △ : The number of balls generated around 10 2.0 mm x 1.2 mm chip resistance exceeds 5 and is 10 or less x: The number of balls generated around 10 2.0 mm x 1.2 mm chip resistance exceeds 10

(3) Copper plate corrosion test A test was conducted according to the conditions defined in JIS Standard Z 3284 (1994), and evaluated as follows. The results are shown in Tables 5 to 8, respectively.
○: No discoloration of the Cu plate ×: Discoloration of the Cu plate (4) Printability test A glass epoxy substrate provided with a solder resist and an electrode (diameter 0.25 mm) with a pattern capable of mounting a BGA of 100 pins 0.5 mm pitch And a 120 μm thick metal mask having the same pattern was prepared.
Six sheets of each solder paste are printed continuously on the glass epoxy substrate using the metal mask, and the transfer volume ratio at a diameter of 0.25 mm is an image inspection machine (product name: aspire2, manufactured by Coyon Technology, Inc.) The following criteria were used to evaluate. The results are shown in Tables 5 to 8, respectively.
:: The number of transfer volume ratio 35% or less is 0. ○: The transfer volume ratio 35% or less is more than 0 and 10 or less. Δ: The transfer volume ratio 35% or less is more than 10 and 50 or less × : The number of transfer volume ratio 35% or less exceeds 50

As described above, in the solder paste according to the example, as the activator (B), the linear saturated dicarboxylic acid having 3 to 4 carbon atoms (B-1) and the dicarbonide having 5 to 13 carbon atoms are used. By using a flux composition containing a predetermined amount of an acid (B-2) and a dicarboxylic acid (B-3) having a carbon number of 20 to 22, it is possible to use only an alloy powder of a Sn-3Ag-0.5Cu solder alloy Even when a powder of a highly oxidizable Bi-rich solder alloy and a powder of a highly oxidizable Sb, In, Bi, Ni, Co-containing solder alloy are used, void formation in solder joints and It is understood that generation of solder balls can be sufficiently suppressed, corrosion of the copper plate can be suppressed, and good printability can be exhibited.
In addition, for example, as in Comparative Examples 5 to 10, even when the flux composition containing the dicarboxylic acid (B-2) having 5 to 13 carbon atoms is used, the solder bonding is performed when the blending amount is small. It can be seen that the effect of suppressing void formation and solder ball formation in the part is insufficient.

As described above, the flux composition of the present invention can also be suitably used for an electronic circuit board that is required to have high reliability, such as a vehicle-mounted electronic circuit board. Furthermore, such an electronic circuit board can be suitably used for an electronic control device that requires higher reliability.

Claims (9)

A flux composition comprising (A) a base resin, (B) an activator, (C) a thixo agent, and (D) a solvent,
The compounding quantity of the said activator (B) is 4.5 mass% or more and 35 mass% or less with respect to the flux composition whole quantity,
(B-1) straight-chain saturated dicarboxylic acid having 3 to 4 carbon atoms as the activator (B) in an amount of 0.5% by mass or more and 3% by mass or less based on the total amount of the flux composition (B-2) carbon The dicarboxylic acid of 5 to 13 in number is 2 mass% or more and 15 mass% or less with respect to the total amount of the flux composition, and (B-3) the dicarboxylic acid having 20 to 22 carbon atoms is 2 mass of in the total amount of the flux composition % Or more and 15 mass% or less. The linear saturated dicarboxylic acid having 3 to 4 carbon atoms (B-1) is at least one of malonic acid and succinic acid,
The carbon atoms from 5 to 13 dicarboxylic acid (B-2) is glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, 2-methyl azelaic acid, sebacic acid, undecane diacid, dodecane diacid and tridecane It is at least one selected or diacid et al,
Said C20-C22 dicarboxylic acid (B-3) is eicosadic acid, 8-ethyl octadecanedioic acid, 8,13-dimethyl-8,12-eicosadiene diacid and 11-vinyl-8-octadecene diacid The flux composition according to claim 1, wherein the flux composition is at least one selected from the group consisting of   The flux composition according to claim 1 or 2, wherein the dicarboxylic acid (B-3) having 20 to 22 carbon atoms is liquid or semisolid at normal temperature.   The flux composition according to any one of claims 1 to 3, further comprising an antioxidant.   The flux composition according to any one of claims 1 to 4, wherein the base resin (A) contains (A-1) a rosin resin.   The flux composition according to claim 5, wherein the base resin (A) further comprises (A-2) a synthetic resin.   A solder paste comprising the flux composition according to any one of claims 1 to 6 and a solder alloy powder.   The solder paste according to claim 7, wherein the solder alloy powder comprises Sn and an alloy containing at least one selected from Ag, Bi, In, Sb, Cu, Ni and Co.   An electronic circuit substrate comprising a solder joint formed using the solder paste according to claim 7 or 8.