JP6138846B2 - Solder composition and method for producing electronic substrate using the same - Google Patents

Description

  The present invention relates to a solder composition and an electronic substrate using the same.

2. Description of the Related Art In recent years, electronic devices have been miniaturized as printed wiring boards have become smaller and smaller, and mounting components mounted on printed boards have been further miniaturized. In order to join such fine parts at a fine pitch, it is required to make the solder powder fine (for example, the average particle diameter is 20 μm or less).
However, when the solder powder has a small average particle diameter, the specific surface area increases, and the amount of oxide generated on the surface of the solder powder increases accordingly. In order to melt and remove the oxide generated on the surface of the solder powder, a solder composition having a flux component having a high reducing power is required. For example, an activator in the flux component has been studied. (For example, patent document 1).

JP 2006-110580 A

  However, when the number of active agents such as organic acids is increased, the solder wettability tends to be improved, but there is a problem that corrosion tends to occur at the soldered portion. In addition, there is a problem that solder balls and dripping due to heating are likely to occur due to the pulverization of the solder powder. As described above, there are various problems associated with the pulverization of the solder powder, and there has been no solder composition that can satisfy all of these problems.

Therefore, the present invention provides excellent solder wettability even when using a solder powder having a small average particle size (for example, an average particle size of 20 μm or less), and prevents corrosion at the soldered portion, solder balls, and heating. It is an object of the present invention to provide a solder composition that can be sufficiently suppressed, and a method for producing an electronic substrate using the same.

In order to solve the above problems, the present invention provides the following solder composition and method for producing an electronic substrate.
The solder composition of the present invention comprises (A) a rosin resin, (B) an activator, (C) a thixotropic agent and (D) a flux composition containing a solvent, and (E) a melting point of 200 ° C. or higher and 250 ° C. or lower. containing the solder powder is, the component (B), (B1) melting point of 220 ° C. or less 180 ° C. or higher, have a three or more carboxyl groups in one molecule and one or more aromatic It contains an aromatic polyvalent carboxylic acid having a ring .

In the solder composition of this invention, it is preferable that the compounding quantity of the said (B1) component is 0.01 to 15 mass% with respect to 100 mass% of flux compositions.
In the solder composition of the present invention, the melting point of the component (B1) is preferably 180 ° C. or higher and 200 ° C. or lower .
In the solder composition of the present invention, the component (B1) is preferably a compound represented by the following general formula (1).

In the general formula (1), X may be the same or different, and each independently represents hydrogen, a hydroxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or An unsubstituted alkenyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted acyl group is shown. Xs may be bonded to each other to form a ring structure.
In the solder composition of this invention, it is preferable that the said (B) component further contains (B2) dicarboxylic acid whose melting | fusing point is 100 degreeC or more and 200 degrees C or less.
In the solder composition of the present invention, the average particle diameter before SL component (E) is preferably at 20μm or less.
The method for producing an electronic board according to the present invention is characterized in that an electronic component is mounted on an electronic board using the solder composition.

Even when a solder powder having a small average particle diameter is used by the solder composition of the present invention, the reason why it is excellent in solder wettability and can sufficiently suppress corrosion at the soldered portion, solder balls and heating is not necessarily determined. However, the present inventors speculate as follows.
That is, the present inventors speculate that the reason why solder balls are generated when solder powder having a small particle size (for example, the average particle size of solder powder is 20 μm or less) is as follows. That is, in preheating in the reflow process, the surface of the fine solder powder is oxidized and becomes a foreign matter. This inhibits aggregation of the solder powders during the main heating. The present inventors infer that the solder powder that has not been agglomerated flows out between the lands together with the flux component, and this becomes a solder ball.
In the flux composition of the present invention, the (B1) component having three or more carboxyl groups in one molecule and relatively strong activity is contained. The oxide can be removed. And since this (B1) component has melting | fusing point of 160 degreeC or more, it becomes a component which provides thixotropy in the preheating in a reflow process, and can suppress dripping by heating. Furthermore, since this component (B1) has a melting point of 160 ° C. or higher, it becomes a component that imparts thixotropy even during pre-heating to solder melting in the reflow process, and can prevent the solder powder from flowing out. In addition, since the component (B1) has a melting point of 220 ° C. or less, it becomes a liquid when the solder is melted in the reflow process, and unreacted substances hardly remain, and corrosion at the soldered portion hardly occurs. As described above, the present inventors speculate that the effects of the present invention are achieved.

According to the present invention, even when a solder powder having a small average particle diameter (for example, an average particle diameter of 20 μm or less) is used, the solder wettability is excellent, and corrosion at the soldered portion, solder balls and dripping due to heating are prevented. It is possible to provide a solder composition that can be sufficiently suppressed and a method for producing an electronic substrate using the same.

It is a graph which shows the relationship between time and temperature at the time of reflow in the test of the wettability of a solder. It is explanatory drawing in order to demonstrate the test method of corrosivity.

  The solder composition of this invention contains the flux composition demonstrated below and the (E) solder powder demonstrated below.

[Flux composition]
The flux composition used in the present invention is a component other than the component (E) in the solder composition, and contains (A) a rosin resin, (B) an activator, (C) a thixotropic agent, and (D) a solvent. Is.

  The blending amount of the flux composition is preferably 5% by mass to 35% by mass, more preferably 7% by mass to 15% by mass, and more preferably 8% by mass with respect to 100% by mass of the solder composition. It is particularly preferable that the content is not less than 13% and not more than 13% by mass. When the blending amount of the flux composition is less than 5% by mass (when the blending amount of the solder powder exceeds 95% by mass), the flux composition as the binder is insufficient, so the flux composition and the solder powder are mixed. On the other hand, when the blending amount of the flux composition exceeds 35% by mass (when the blending amount of the solder powder is less than 65% by mass), when the obtained solder composition is used, It tends to be difficult to form a sufficient solder joint.

[(A) component]
Examples of the (A) rosin resin used in the present invention include rosins and rosin modified resins. Examples of rosins include gum rosin, wood rosin, tall oil rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. As rosin-based modified resins, unsaturated organic acid-modified resins of the above rosins that can be reactive components of Diels-Alder reactions (aliphatic unsaturated monobasic acids such as (meth) acrylic acid, fumaric acid, maleic acid, etc.) adietic acids such as aliphatic unsaturated dibasic acids such as α, β-unsaturated carboxylic acids, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid) and abietic acids such as modified products thereof, and these The thing which has a modified substance as a main component is mentioned. These rosin resins may be used alone or in combination of two or more.

  The blending amount of the component (A) is preferably 30% by mass or more and 70% by mass or less, and more preferably 35% by mass or more and 60% by mass or less with respect to 100% by mass of the flux composition. When the blending amount of the component (A) is less than the lower limit, oxidation of the copper foil surface of the soldering land is prevented and the molten solder is easily wetted on the surface, so-called solderability is lowered, and solder balls are easily generated. On the other hand, if the upper limit is exceeded, the amount of residual flux tends to increase.

[Component (B)]
The (B) active agent used for this invention needs to contain the (B1) component demonstrated below.
This (B 1 ) component is a polyvalent carboxylic acid having a melting point of 160 ° C. or higher and 220 ° C. or lower and having three or more carboxyl groups in one molecule.
When the melting point of the component (B 1 ) is in the range of 160 ° C. or higher and 220 ° C. or lower, corrosion at the soldered portion, solder balls, and dripping due to heating can be sufficiently suppressed. Further, from the same viewpoint, the melting point of the component (B1) is more preferably 180 ° C. or higher and 200 ° C. or lower, and particularly preferably 190 ° C. or higher and 200 ° C. or lower.
If the number of carboxyl groups in one molecule in the component (B1) is 3 or more, the wettability of the solder can be sufficiently improved. From the same viewpoint, the number of carboxyl groups in one molecule is more preferably 3 or more and 6 or less, and particularly preferably 3.
This component (B1) may be an aliphatic polyvalent carboxylic acid or an aromatic polyvalent carboxylic acid, but from the viewpoint of an active action, an aromatic polyvalent carboxylic acid having one or more aromatic rings. An acid is preferred. Furthermore, examples of the aromatic ring in the component (B1) include a benzene ring and a naphthalene ring. Among these, a benzene ring is preferable from the viewpoint of lowering the melting point of the component (B1).
Examples of such a component (B1) include compounds represented by the following general formula (1).

In the general formula (1), Xs may be the same or different. X is independently hydrogen, hydroxy group, substituted or unsubstituted alkyl group (such as methyl group or ethyl group), substituted or unsubstituted aryl group (such as phenyl group), or substituted or unsubstituted alkenyl group. (Such as an ethenyl group), a substituted or unsubstituted alkoxy group (such as a methoxy group or an ethoxy group), or a substituted or unsubstituted acyl group (such as an acetyl group). X may combine with each other to form a ring structure.
Specific examples of the component (B1) include hemimellitic acid.

  The blending amount of the component (B1) is preferably 0.01% by mass or more and 15% by mass or less, and 0.1% by mass or more and 8% by mass or less with respect to 100% by mass of the flux composition. Is more preferably 0.5% by mass or more and 4% by mass or less, and particularly preferably 0.8% by mass or more and 2% by mass or less. When the blending amount of the component (B1) is less than the lower limit, solder balls and solder sagging tend to occur. On the other hand, when the upper limit is exceeded, the insulating property of the flux composition tends to decrease.

The component (B) further contains (B2) a dicarboxylic acid having a melting point of from 100 ° C. to 200 ° C. (more preferably from 120 ° C. to 200 ° C., particularly preferably from 160 ° C. to 200 ° C.). preferable. According to such (B2) component, since the fluidity | liquidity of the active agent in a flux composition can be adjusted to a more suitable range, the effect | action of (B1) component can be improved synergistically.
Examples of the component (B2) include malonic acid, succinic acid, adipic acid, suberic acid, and sebacic acid. Among these, succinic acid and adipic acid are preferable from the viewpoint of the active action, and succinic acid is more preferable. These may be used alone or in combination of two or more.

  When using the (B2), the amount of the component (B2) is preferably 0.1% by mass or more and 5% by mass or less, and 0.2% by mass or more with respect to 100% by mass of the flux composition. It is more preferably 3% by mass or less, and particularly preferably 0.5% by mass or more and 2% by mass or less. If the blending amount of the component (B2) is less than the lower limit, solder dripping tends to occur. On the other hand, if the amount exceeds the upper limit, the insulating property of the flux composition tends to decrease.

In the component (B), the component (B1) and another organic acid other than the component (B1) and the component (B2) (hereinafter referred to as component (B3)) may be used in combination.
Examples of the component (B3) include organic acids other than the component (B1) in addition to monocarboxylic acids and dicarboxylic acids other than the component (B2).
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid Arachidic acid, behenic acid, lignoceric acid, glycolic acid and the like.
Examples of the dicarboxylic acid other than the component (B2) include glutaric acid.
Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.
These (B3) components may be used individually by 1 type, and 2 or more types may be mixed and used for them. Of these (B3) components, dimer acid is preferably used. Since dimer acid tends to prevent reoxidation of the solder powder, the action of the component (B1) can be synergistically enhanced.

  The blending amount of the component (B3) 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 with respect to 100% by mass of the flux composition. It is particularly preferably 5% by mass or more and 15% by mass or less. When the blending amount of the component (B3) is less than the lower limit, the active action tends to be insufficient, and when it exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

  In the component (B), the component (B1) and (B4) a non-dissociative activator comprising a non-dissociable halogenated compound may be used in combination. The component (B4) can impart an active action as the component (B4) without substantially affecting the active action of the components (B1) to (B3).

  Examples of the component (B4) include non-salt organic compounds in which halogen atoms are bonded by a covalent bond. This halogenated compound may be a compound formed by covalent bonding of single elements of chlorine, bromine, iodine and fluorine, such as chlorinated, brominated, iodide and fluoride, but any of chlorine, bromine, iodine and fluorine may be used. The compound which has each two or all of these covalent bonds may be sufficient. In order to improve the solubility in an aqueous solvent, these compounds preferably have a polar group such as a hydroxyl group or a carboxyl group such as a halogenated alcohol or a halogenated carboxyl. Examples of the halogenated alcohol include 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol, 1,4-dibromo-2-butanol, Brominated alcohols such as tribromoneopentyl alcohol, chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and the like Compounds. Examples of the halogenated carboxyl include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid, etc., 2-chlorobenzoic acid, 3-chloropropion Examples thereof include carboxyl chloride such as acid, brominated carboxyl such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid and 2-bromobenzoic acid, and other similar compounds. Examples of these compounds include tris (2,3-dibromopropyl) isocyanurate. These activators may be used individually by 1 type, and may mix and use 2 or more types.

  The blending amount of the component (B4) is preferably 0.1% by mass or more and 10% by mass or less, and 0.2% by mass or more and 5% by mass or less with respect to 100% by mass of the flux composition. Is more preferably 0.5% by mass or more and 2% by mass or less. When the blending amount of the component (B4) is less than the lower limit, the solder spread tends to decrease, and when it exceeds the upper limit, the insulating property of the flux composition tends to decrease.

  The total amount of the component (B) is preferably 1% by mass or more and 25% by mass or less, and more preferably 3% by mass or more and 20% by mass or less with respect to 100% by mass of the flux composition. It is particularly preferably 5% by mass or more and 20% by mass or less. When the blending amount of the component (B) is less than the lower limit, solder balls tend to be easily formed. On the other hand, when the amount exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

[Component (C)]
Examples of the (C) thixotropic agent used in the present invention include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These thixotropic agents may be used alone or in combination of two or more.

  The blending amount of the component (C) is preferably 1% by mass or more and 15% by mass or less, and more preferably 2% by mass or more and 10% by mass or less with respect to 100% by mass of the flux composition. If the blending amount is less than the lower limit, thixotropy cannot be obtained and the sagging tends to occur. On the other hand, if it exceeds the upper limit, the thixotropy tends to be too high and printing tends to be poor.

[(D) component]
As the solvent (D) used in the present invention, a known solvent can be appropriately used. As such a solvent, a water-soluble solvent having a boiling point of 170 ° C. or higher is preferably used.
Examples of such solvents include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, hexyl diglycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, and 2-ethylhexyl diglycol (EHDG). , Octanediol, phenyl glycol, diethylene glycol monohexyl ether, tetraethylene glycol dimethyl ether (MTEM). These solvents may be used alone or in combination of two or more.

  The blending amount of the component (D) is preferably 20% by mass to 60% by mass and more preferably 30% by mass to 50% by mass with respect to 100% by mass of the flux composition. If the blending amount of the solvent is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted to an appropriate range.

[Other ingredients]
In addition to the component (A), the component (B), the component (C) and the component (D), the flux composition used in the present invention, if necessary, other additives, Other resins can be added. Examples of other additives include antifoaming agents, antioxidants, modifiers, matting agents, and foaming agents. Examples of other resins include acrylic resins.

[(E) component]
The solder powder (E) used in the present invention is preferably composed only of lead-free solder powder, but may be lead-containing solder powder. As the solder alloy in the solder powder, an alloy containing tin (Sn) as a main component is preferable. Examples of the second element of the alloy include silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), and antimony (Sb). Furthermore, you may add another element (after 3rd element) to this alloy as needed. Examples of other elements include copper, silver, bismuth, antimony, aluminum (Al), and indium (In).
Moreover, it is preferable that this solder powder is a lead-free solder powder from a viewpoint of the influence on an environment. Here, the lead-free solder powder refers to 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.

  Specific examples of the lead-free solder powder include Sn-Ag, Sn-Ag-Cu, Sn-Cu, Sn-Ag-Bi, Sn-Bi, Sn-Ag-Cu-Bi, Sn-Sb, Sn. -Zn-Bi, Sn-Zn, Sn-Zn-Al, Sn-Ag-Bi-In, Sn-Ag-Cu-Bi-In-Sb, In-Ag, and the like can be given. Among these, Sn—Ag—Cu-based solder alloys are preferably used from the viewpoint of solder joint strength. The melting point of the Sn—Ag—Cu solder is usually 200 ° C. or higher and 250 ° C. or lower. Note that among the Sn—Ag—Cu solders, the solder having a low silver content has a melting point of 210 ° C. or higher and 250 ° C. or lower.

The average particle diameter of the component (E) is usually 1 μm or more and 40 μm or less. However, from the viewpoint that it can be applied to an electronic substrate having a narrow solder pad pitch, the upper limit value of the average particle diameter is 25 μm or less. Is preferably 20 μm or less, more preferably 15 μm or less, and particularly preferably 12 μm or less. On the other hand, the lower limit value of the average particle diameter is not particularly limited, but may be, for example, 2 μm or more, or 3 μm or more. The average particle size can be measured with a dynamic light scattering type particle size measuring device.
Moreover, according to the solder composition of the present invention, even when the average particle diameter of the solder powder is small, the solder wettability is excellent, and corrosion at the soldered portion, solder balls and dripping due to heating can be sufficiently suppressed.

[Method for producing solder composition]
The solder composition of the present invention can be produced by blending the above-described flux composition and the above-described (E) solder powder in the above-mentioned predetermined ratio and stirring and mixing them.

[Electronic substrate]
Next, the electronic substrate of the present invention will be described. The electronic board of the present invention is characterized in that an electronic component is mounted on an electronic board (such as a printed wiring board) using the solder composition described above. Therefore, in the electronic substrate of the present invention, corrosion at the soldering portion, solder balls, and dripping due to heating can be sufficiently suppressed.
Examples of the coating apparatus used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser.
In addition, the electronic component is placed on the solder composition applied by the coating device, heated under a predetermined condition by a reflow furnace, and the electronic component is mounted on the printed wiring board by a reflow process. Can be implemented.

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 printed wiring board. As a result, the electronic component can be mounted on the printed 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—Ag—Cu-based solder alloy, preheating may be performed at a temperature of 150 to 200 ° C. for 60 to 120 seconds, and a peak temperature may be set to 230 to 270 ° C.

Further, the solder composition and the electronic substrate of the present invention are not limited to the above-described embodiments, 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 electronic board, the printed wiring board and the electronic component are bonded by the reflow process, but the invention is not limited to this. For example, instead of the reflow process, the printed 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)
Rosin resin: hydrogenated acid-modified rosin, trade name “Pine Crystal KE-604”, manufactured by Arakawa Chemical Industries, Ltd. (component (B1))
Activator A: Hemimellitic acid (see structural formula (S1) below), melting point 195 ° C.
(Other ingredients)
Activator B: trimellitic acid (see the following structural formula (S2)), melting point 229-231 ° C.
Activator C: trimesic acid (see structural formula (S3) below), melting point over 300 ° C. (component (B2))
Activator D: Succinic acid, melting point 185-187 ° C
((B3) component)
Activator E: Picolinic acid Activator F: Dimer acid, trade name “UNIDYME14”, Activator G manufactured by Arizona Chemical Co., Glutaric acid, melting point 95-98 ° C.
((B4) component)
Activator H: trans-2,3-dibromo-2-butene-1,4-diol (TDBD)
((C) component)
Thixotropic agent: Hardened castor oil, trade name “Hima-ko”, manufactured by KF Trading (component (D))
Solvent A: 2-ethylhexyl diglycol (EHDG)
Solvent B: Tetraethylene glycol dimethyl ether (MTEM)
((E) component)
Solder powder: particle size 5-15 μm (average particle size 10 μm), solder melting point 220 ° C., solder composition Sn / Ag3.0 / Cu0.5
(Other ingredients)
Antioxidant: Hindant phenolic antioxidant, trade name “Irganox 245”, manufactured by Ciba Japan

[Example 1]
Rosin resin 36% by mass, thixotropic agent 6% by mass, solvent A 30% by mass, solvent B 14.9% by mass, activator A 0.1% by mass, activator D 0.5% by mass, activator E 0.5% by mass, activity Agent F6 mass%, activator G 3 mass%, activator H 1 mass%, and antioxidant 2 mass% were put into a container and mixed using a planetary mixer to obtain a flux composition.
Thereafter, 11% by mass of the obtained flux composition and 89% by mass (100% by mass in total) of the solder powder were put into a container and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 to 5]
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 to 7]
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 the solder composition (solder ball, solder wettability, corrosiveness, heating dripping) was performed by the following method. The obtained results are shown in Tables 1 and 2.
(1) Solder ball The solder ball (solder ball) is tested in accordance with the method described in Appendix 11 of JIS Z 3284-1994. That is, a ceramic plate (size: 50 mm × 50 mm, thickness: 0.5 mm) was prepared, and a 0.2 mm thick metal mask having a circular pattern hole with a diameter of 6.5 mmφ was used for this ceramic plate, and soldering was performed. A test piece was obtained by printing the composition. The test piece was placed on a hot plate adjusted to a temperature of 260 ° C. and held for 5 seconds after the solder was melted. The test piece was observed with a microscope, and the solder balls were evaluated according to the following criteria.
A: Solder (powder) melts, and the solder becomes one large sphere with no solder balls around.
○: The solder (powder) is melted, and the solder becomes one large sphere, and there are three or less solder balls having a diameter of 75 μm or less around.
X: Solder (powder) is melted, and the solder becomes one large sphere, and there are four or more solder balls having a diameter of 75 μm or less, or many fine spheres are arranged in a semi-continuous ring.
XX: There is a portion where the solder (powder) is not melted, and a large number of fine spheres are arranged in a semi-continuous ring around a large solder sphere.
(2) Solder wettability A solder wettability (dewetting) test is performed in accordance with the method described in Appendix 10 of JIS Z 3284-1994. That is, a phosphorous deoxidized copper plate (size: 50 mm × 50 mm, thickness: 0.5 mm) was prepared and polished with an abrasive. A test piece was obtained by printing a solder composition on this phosphorous deoxidized copper plate using a 0.2 mm thick metal mask having a circular pattern hole having a diameter of 6.5 mmφ. The test piece was reflowed in a nitrogen atmosphere under the reflow conditions shown in FIG. The test piece was observed with a microscope, and the wettability of the solder was evaluated according to the following criteria.
○: All the portions to which the solder composition is applied are wet with solder.
(Triangle | delta): Most of the parts which apply | coated the solder composition are the states wet with solder (a dewetting is also included).
(3) Corrosivity Corrosion test is performed according to the method described in Appendix 4 of JIS Z 3284-1994. That is, two copper plates (size: 50 mm × 50 mm, thickness: 0.5 mm) were prepared, polished with an abrasive, and subjected to ultrasonic cleaning. And as shown in FIG. 2, what bent the U-shaped part in the 5 mm part of the copper plate to the U-shape is the 1st board | substrate A, and what bent the 6-mm part of both ends to the U-shape is the 2nd board | substrate B. did. The solder composition P was printed on the second substrate B using a metal mask with a thickness of 0.2 mm having a circular pattern hole with a diameter of 6.5 mmφ. The second substrate B is covered with the first substrate A to form a test piece. The test piece was placed on a hot plate adjusted to a temperature of 270 ° C. and held for 5 seconds after the solder was melted. Such a test piece was put into a constant temperature and humidity chamber set at a temperature of 40 ° C. and a relative humidity of 90%, and left for 96 hours to obtain a test piece after the test. About the test piece after a test, it checks visually whether there is any discoloration of the residue in the 1st board | substrate A and the 2nd board | substrate B, Furthermore, a residue is wash | cleaned with IPA, and it is confirmed visually that there is no discoloration of copper. Based on the following criteria, the discoloration of the copper foil was evaluated.
○: No residue or copper discoloration.
Δ: There is no residue, but the copper surface is discolored.
X: There is discoloration of the residue, and the copper surface is discolored.
(4) Heating Sagging A heating sagging test is performed in accordance with the method described in Appendix 8 of JIS Z 3284-1994. That is, a copper clad laminate (size: 80 mm × 60 mm, thickness: 1.6 mm) was prepared, polished with an abrasive, and the surface was wiped with IPA. And on this copper-clad laminate, there are two types of holes (i) 3.0 x 0.7 mm or (ii) 3.0 x 1.5 mm, which are arranged in 0.1 mm steps. A test piece was obtained by printing a solder composition using a metal mask having a thickness of 0.2 mm having two types of pattern holes. The test piece was heated in an oven set at 150 ° C. for 1 minute. The test piece was visually observed, and the thermal sagging was evaluated at the minimum interval at which all of the printed solder compositions were not integrated in the five rows of the two types of patterns. Note that the smaller the minimum interval, the better the heating droop.

As is clear from the results shown in Tables 1 and 2, the solder compositions of the present invention (Examples 1 to 5) all have good solder balls, solder wettability, corrosiveness, and heating dripping. confirmed. Therefore, the solder composition of the present invention has solder wettability even when using a solder powder having a small average particle diameter (solder composition is tin-silver-copper system and the melting point of the solder is 200 ° C. or higher and 250 ° C. or lower). It was confirmed that corrosion at the soldering part, solder balls and dripping due to heating can be sufficiently suppressed.
On the other hand, when the solder composition not containing the component (B1) is used (Comparative Examples 1 to 7), any one of the solder ball, the solder wettability, the corrosiveness, and the heating dripping is insufficient. I found out that

The solder composition of the present invention can be suitably used as a technique for mounting an electronic component on an electronic board such as a printed wiring board of an electronic device.

Claims (7)

(A) A flux composition containing a rosin resin, (B) an activator, (C) a thixotropic agent and (D) a solvent, and (E) a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower. ,
The component (B), (B1) or less melting point 220 ° C. 180 ° C. or higher, have a three or more carboxyl groups in a molecule and an aromatic polycarboxylic acid having one or more aromatic rings A solder composition comprising: The solder composition according to claim 1,
A blending amount of the component (B1) is 0.01% by mass or more and 15% by mass or less with respect to 100% by mass of the flux composition. In the solder composition according to claim 1 or 2,
The melting point of said (B1) component is 180 degreeC or more and 200 degrees C or less. The solder composition characterized by the above-mentioned. In the solder composition according to any one of claims 1 to 3 ,
The said (B1) component is a compound represented by following General formula (1). Solder composition characterized by the above-mentioned.

(In the general formula (1), X may be the same or different, and each independently represents hydrogen, a hydroxy group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted group. Or an unsubstituted alkenyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted acyl group, and X may be bonded to each other to form a ring structure.) In the solder composition according to any one of claims 1 to 4 ,
The component (B) further contains (B2) a dicarboxylic acid having a melting point of 100 ° C. or higher and 200 ° C. or lower. In the solder composition according to any one of claims 1 to 5 ,
The average particle diameter before Symbol (E) component, solder composition, characterized in that at 20μm or less. An electronic component is mounted on an electronic substrate using the solder composition according to any one of claims 1 to 6 , and a method for manufacturing an electronic substrate.

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