JP6466361B2 - Solder composition for forming solder bump and method for forming solder bump - Google Patents

Description

  The present invention relates to a solder composition for forming solder bumps and a method for forming solder bumps.

As a method for forming solder bumps, a plating method, a method of placing solder balls, a method of printing and reflowing a solder composition (printing method), and the like are employed. In these printing methods, the solder composition is printed on the electrodes of the electronic substrate using a metal mask. Due to the remaining scraping of the solder composition at the time of printing, the height of the bumps after the bump formation varies, and the solder bumps are not easily wetted (missing bumps).
In order to solve such a problem, a solder composition containing a flux composition containing a rosin resin, a solvent, an organic acid and a thixotropic agent has been proposed. In this solder composition, a mixture of polyalkylene glycol monoalkyl ether and polyalkylene glycol dialkyl ether is used as a solvent, and a thixotropic agent having a particle size of 10 μm or less as measured by a grind gauge (Patent Document 1). reference).

JP 2014-87814 A

  The solder composition described in Patent Document 1 can suppress the scraping residue of the solder composition during printing and has excellent printability. However, even when printing is properly performed using a solder composition having excellent printability, non-wetting of the solder bumps may occur. Therefore, a method for more reliably suppressing non-wetting of solder bumps is required.

  Then, an object of this invention is to provide the solder composition for solder bump formation which can fully suppress the non-wetting of a solder bump, and the formation method of a solder bump using the same.

In order to solve the above-mentioned problems, the present invention provides the following solder composition for forming solder bumps and a method for forming solder bumps.
The solder composition for forming solder bumps of the present invention contains (A) a binder and (B) a flux composition containing an activator and (C) solder powder, and the (A) binder comprises (A1). contains an epoxy compound, wherein the (B) active agent, (B1) an organic acid amine salt contains, weight average molecular weight of the (A1) epoxy compound is 100 to 10,000, the component (a) Is 50% by mass or more and 98% by mass or less with respect to 100% by mass of the flux composition, and the compounding amount of the component (B1) is 0.1% with respect to 100% by mass of the flux composition. It is 5 mass% or more and 20 mass% or less .

In the solder bump forming solder composition of the present invention, the (A1) epoxy compound is preferably a liquid at a temperature 25 ° C..
In the solder composition for forming solder bumps of the present invention, the average particle diameter of the (C) solder powder is preferably 10 μm or less.
In the solder composition for forming solder bumps of the present invention, the blending amount of the flux composition is preferably 15% by mass or more and 50% by mass or less with respect to 100% by mass of the solder composition.

  The method for forming a solder bump according to the present invention is a method for forming a solder bump using the solder composition for forming a solder bump, wherein a printing step of printing the solder composition on an electrode of an electronic substrate, and the electronic A bump forming step for forming solder bumps on the electrodes by melting the solder powder in the solder composition by heating the substrate, and a residue cleaning step for cleaning the flux residue on the electronic substrate, It is the method characterized by providing.

The reason why the solder bump non-wetting can be sufficiently suppressed by the solder composition for forming a solder bump of the present invention is not necessarily clear, but the present inventors speculate as follows.
That is, the present inventors infer that the mechanism by which the solder bumps are not wet even when the solder composition is properly printed is as follows. That is, the solder powder in the solder composition after printing is melted and bonded by reflow processing to form solder bumps. If the solder powder flows before melting during the reflow process, normal solder bumps cannot be formed due to insufficient supply of solder. As a result, the present inventors infer that the solder bumps are not wet.
In the solder composition of the present invention, (A) at least one of an epoxy compound and (A2) an acrylic compound is used as a binder, and (B1) an organic acid amine salt is used as an activator. Yes. When used in such a combination, surprisingly, sagging (flow of solder powder) when the solder composition is heated can be suppressed without increasing the viscosity and thixotropy of the solder composition at room temperature. . The reason for this is not necessarily clear, but in the binder such as an epoxy compound and an acrylic compound, the heated organic acid amine salt and the solder powder interact with each other to promote aggregation between the particles and the present invention. They guess. And since the dripping at the time of heating a solder composition can be suppressed, the non-wetting of a solder bump can fully be suppressed. Moreover, in the solder composition of the present invention, it is not necessary to increase the viscosity and thixotropy of the solder composition at room temperature, so that the printability of the solder composition does not deteriorate. As described above, the present inventors speculate that the effects of the present invention are achieved.

  ADVANTAGE OF THE INVENTION According to this invention, the solder composition for solder bump formation which can fully suppress the non-wetting of a solder bump, and the formation method of a solder bump using the same can be provided.

  The solder composition for forming solder bumps of the present invention contains a flux composition described below and (C) solder powder described below.

[Flux composition]
First, the flux composition used for this invention is demonstrated. The flux composition used in the present invention is a component other than the solder powder in the solder composition, and contains (A) a binder and (B) an activator.

[(A) component]
Examples of the (A) binder used in the present invention include (A1) an epoxy compound and (A2) an acrylic compound. These may be used alone or in combination of two or more. Among these, (A1) an epoxy compound is more preferable from the viewpoint of removability of the flux residue. The component (A) is preferably liquid at a temperature of 25 ° C. from the viewpoint of the applicability of the solder composition.

Examples of the (A1) epoxy compound used in the present invention include a monomer having an epoxy group, an oligomer having an epoxy group, and an epoxy resin. Among these, an epoxy resin is preferable from the viewpoint of the function as a binder. These may be used alone or in combination of two or more.
As such an epoxy resin, a known epoxy resin can be appropriately used. 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. Among these, from the viewpoint that the resin viscosity can be reduced, bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferable, and bisphenol F type epoxy resin is particularly preferable. In addition, these epoxy resins may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The weight average molecular weight of the component (A1) is preferably 100 or more and 10,000 or less, more preferably 100 or more and 5000 or less, and more preferably 100 or more and 1000 or less, from the viewpoint of applicability of the solder composition. It is particularly preferred. In the present specification, the weight average molecular weight is a value measured by gel permeation chromatography and converted using a standard polystyrene calibration curve.

The (A2) acrylic compound used in the present invention is an acrylic polymer made from an acrylic monomer (acrylic ester, methacrylic ester, acrylic acid, methacrylic acid, etc.) as a raw material.
As such an acrylic polymer, a known acrylic polymer can be appropriately used. Such an acrylic polymer may have a functional group. In this case, examples of the functional group include a hydroxyl group, a carboxyl group, an epoxy group, an alkyl group, an alkoxy group, and an alkoxysilyl group.

  The weight average molecular weight of the component (A2) is preferably 100 or more and 20000 or less, more preferably 500 or more and 15000 or less, and more preferably 1000 or more and 10,000 or less, from the viewpoint of applicability of the solder composition. It is particularly preferred.

  The blending amount of the component (A) is preferably 50% by mass or more and 98% by mass or less, more preferably 60% by mass or more and 95% by mass or less, with respect to 100% by mass of the flux composition. It is particularly preferable that the content is not less than mass% and not more than 90 mass%. When the blending amount of the component (A) is less than the lower limit, the function as a binder tends to be reduced, and it is difficult to suppress sagging when the solder composition is heated. On the other hand, when the upper limit is exceeded, B1) The compounding amount of the organic acid amine salt is insufficient, and it tends to be difficult to suppress sagging when the solder composition is heated.

[Component (B)]
The (B) activator used in the present invention contains (B1) an organic acid amine salt. In addition to the component (B1), (B2) an organic acid may be contained. Moreover, you may further contain well-known activators (a non-dissociation type active agent, an amine type activator, etc.) other than the said (B1) component and (B2).

The (B1) organic acid amine salt used in the present invention is a salt of an amine and an organic acid.
The component (B1) 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 ℃. When the softening point is less than the lower limit, the pot life tends to be lowered. On the other hand, when the upper limit is exceeded, the solder wettability at low-temperature bonding tends to be not good. 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 another 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 monocarboxylic acid include propionic acid, butyric acid, valeric acid, caproic acid, and enanthic acid.
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 other carboxylic acid include trimellitic acid, 1,2,3-propanetricarboxylic acid, citric acid, and picolinic acid.

  The blending amount of the component (B1) is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 18% by mass or less with respect to 100% by mass of the flux composition. Preferably, it is still more preferably 3% by mass or more and 15% by mass or less, and particularly preferably 5% by mass or more and 13% by mass or less. When the blending amount of the component (B1) is less than the lower limit, it tends to be difficult to suppress sagging when the solder composition is heated. On the other hand, when the upper limit is exceeded, the pot life tends to decrease.

As the (B2) organic acid used in the present invention, a known organic acid can be appropriately used. Such an organic acid may be a monocarboxylic acid, a dicarboxylic acid, or another 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, and more preferably a dicarboxylic acid having 5 to 6 carbon atoms, from the viewpoint of activity.
Examples of the monocarboxylic acid include propionic acid, butyric acid, valeric acid, caproic acid, and enanthic acid.
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 other carboxylic acid include trimellitic acid, 1,2,3-propanetricarboxylic acid, citric acid, and picolinic acid.

  The blending amount of the component (B) is preferably 1% by mass or more and 25% by mass or less, more preferably 2% by mass or more and 20% by mass or less, with respect to 100% by mass of the flux composition. It is still more preferably 3% by mass or more and 18% by mass or less, and particularly preferably 5% by mass or more and 15% by mass or less. When the blending amount of the component (B) is less than the lower limit, the activity of the flux composition tends to be insufficient, and when it exceeds the upper limit, the pot life tends to be lowered.

[Other ingredients]
The flux composition of the present invention may further contain a thixotropic agent from the viewpoint of printability. Examples of the thixotropic agent used herein 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.

  When the thixotropic agent is used, the blending amount is preferably 0.5% by mass or more and 15% by mass or less, and preferably 1% by mass or more and 10% by mass or less with respect to 100% by mass of the flux composition. More preferred. 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.

In addition to the component (A), the component (B) and the thixotropic agent, other additives and further other resins can be added to the flux composition used in the present invention, if necessary. Examples of other additives include antifoaming agents, antioxidants, modifiers, matting agents, and foaming agents. Moreover, the flux composition used for this invention may contain the rosin-type resin in the range which can achieve the effect of this invention.
In addition, although the flux composition used for this invention may contain the solvent, it is preferable not to contain a solvent from a viewpoint of suppressing dripping at the time of heating a solder composition.
Moreover, it is preferable that the flux composition used for this invention does not contain fast-curing hardening | curing agents, such as an imidazole compound, from a viewpoint of the removability of a flux residue.

[Solder composition for forming solder bumps]
Next, the solder composition for forming solder bumps of the present invention will be described. The solder composition for forming solder bumps of the present invention contains the flux composition used in the present invention and (C) solder powder described below.
The blending amount of the flux composition is preferably 15% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 45% by mass or less, with respect to 100% by mass of the solder composition, and 30% by mass. % To 42% by mass is particularly preferable. When the blending amount of the flux composition is less than 15% by mass (when the blending amount of the solder powder exceeds 85% 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 50% by mass (when the blending amount of the solder powder is less than 50% by mass), when the obtained solder composition is used, It tends to be difficult to form solder bumps.

[Component (C)]
The (C) solder powder used in the present invention preferably has a melting point of 240 ° C. or lower, and has a melting point of 180 ° C. or lower (more preferably 160 ° C. or lower) from the viewpoint of low temperature processing. More preferred. When the solder powder having a melting point exceeding 180 ° C. is used, the solder powder tends not to be melted when the temperature during reflow treatment is low (for example, 180 ° C. or lower). On the other hand, from the viewpoint of solder joint strength, the melting point of the solder powder is preferably 160 ° C. or higher, and more preferably 200 ° C. or higher.
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.

  The component (C) is a group consisting of tin (Sn), bismuth (Bi), copper (Cu), silver (Ag), antimony (Sb), indium (In), zinc (Zn), and titanium (Ti). It is preferably a metal or alloy made of at least one metal selected from the group consisting of: For example, tin-based solders include tin-copper such as Sn-0.7Cu; tin-silver such as Sn-3.5Ag; Sn-3.0Ag-0.5Cu, Sn-3.5Ag-0 Tin-silver-copper systems such as .7Cu, Sn-1.0Ag-0.7Cu, Sn-0.3Ag-0.7Cu; Sn-2.5Ag-1.0Bi-0.5Cu, Sn-1.0Ag Tin-silver-bismuth-copper system such as -2.0Bi-0.5Cu; Tin-silver-bismuth-indium system such as Sn-3.5Ag-0.5Bi-8.0In; Sn-1.0Ag-0 Tin-silver-copper-bismuth-indium system such as 7Cu-2.0Bi-0.2In; Tin-bismuth system such as Sn-58Bi; Tin-silver-bismuth system such as Sn-1.0Ag-58Bi; Sn-5 . Tin-antimony system such as 0Sb; S Tin-zinc system such as Sn-9Zn; Tin-zinc-bismuth system such as Sn-8.0Zn-3.0Bi; Tin-indium-antimony-zinc system such as Sn-30In-12Sb-3Zn; Sn-56Bi-4Ti Tin-bismuth-titanium system such as Sn-3.5Ag-4Ti; tin-silver-titanium system such as Sn-52In; tin-indium system such as Sn-52In. Examples of the indium-based solder include indium-based metal indium; indium-silver-based such as In-3.0Ag. In addition to the above metals, iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo), phosphorus (P), cerium (Ce), Germanium (Ge), silicon (Si), gallium (Ga), aluminum (Al), niobium (Nb), vanadium (V), calcium (Ca), magnesium (Mg), zirconium (Zr), gold (Au), Palladium (Pd), platinum (Pt), lead (Pb), etc. may be contained. Among these, tin-bismuth, tin-silver-bismuth, tin-indium, indium, indium-silver, and the like are more preferable from the viewpoint of low melting point characteristics. From the viewpoint of solder joint strength, tin-silver-copper, tin-silver, and the like are preferable.

  The average particle size of the component (C) is preferably 0.5 μm or more and 10 μm or less, more preferably 0.5 μm or more and 8 μm or less, from the viewpoint of corresponding to an electronic substrate having a narrow electrode pitch. The thickness is particularly preferably 5 μm or less. The average particle size can be measured by a dynamic light scattering type or laser diffraction type particle size measuring device.

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

[Method of forming solder bumps]
Next, the solder bump forming method of the present invention will be described.
The solder bump forming method of the present invention is a method using the solder bump forming solder composition of the present invention. And the formation method of the solder bump of this invention is a method provided with the printing process, bump formation process, and residue cleaning process which are demonstrated below.

In the printing process, a solder composition is printed on the electrode of the electronic substrate.
As an electronic board, a printed wiring board etc. are mentioned, for example.
The solder composition is the solder composition for forming solder bumps of the present invention.
As a printing method of the solder composition, a known method can be appropriately employed. The mask used for the printing method may be one that can be printed so as to correspond to the pattern of the electrode, or one that can be printed solid regardless of the electrode.

In the bump forming step, the electronic substrate after the printing step is heated to melt the solder powder in the solder composition, thereby forming solder bumps on the electrodes.
If the electronic substrate after the printing process is heated using a reflow apparatus or the like, the surface oxide film of the solder powder is reduced by the active component contained in the flux composition, so that the surface oxide film is removed. Then, metal bonding is performed with the solder powder or the surface of the electrode, and then diffusion proceeds, bonding of the molten solder proceeds, and a solder bump can be formed on the electrode.
In addition, when solid printing is performed in the printing process, since the molten solder on the substrate is bonded to the molten solder on the electrode while being pulled, solder bumps can be selectively formed on the electrode.
The conditions of the reflow apparatus are not particularly limited, and can be appropriately set according to the type of solder powder.
The preheating temperature in the reflow apparatus is preferably at least 70 ° C lower than the melting point of the solder, more preferably at least 50 ° C lower than the melting point of the solder, and at least 30 ° C lower than the melting point of the solder. It is particularly preferred that
The peak temperature in the reflow apparatus is preferably not less than the melting point of the solder, more preferably not less than 10 ° C. higher than the melting point of the solder, and particularly preferably not less than 20 ° C. higher than the melting point of the solder. .

In the residue cleaning step, the flux residue on the electronic substrate after the bump forming step is cleaned.
Here, examples of the cleaning liquid used for cleaning include alcohol solvents, terpene solvents, petroleum solvents, hydrocarbon solvents, alkaline solvents, and water. These may be used alone or in combination of two or more. The cleaning liquid may further contain a cleaning agent (such as a surfactant).

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.
((A1) component)
Epoxy compound: Epoxy resin, trade name “EXA-830LVP”, manufactured by DIC (component (A2))
Acrylic compound: Acrylic polymer, trade name “ARUFON UC-1020”, manufactured by Toagosei Co., Ltd. (component (B1))
Organic acid amine salt: benzylamine adipate, manufactured by Showa Chemical Co. (component (B2))
Organic acid A: Adipic acid Organic acid B: Picolinic acid Organic acid C: Glutaric acid (component (C))
Solder powder: 2 to 6 μm (average particle size 4 μm), solder melting point 139 ° C., solder composition 42 Sn / 58 Bi
(Other ingredients)
Rosin resin: hydrogenated acid-modified rosin, trade name “Pine Crystal KE-604”, Arakawa Chemical Industries, Ltd. Solvent: 2-ethylhexyl diglycol thixotropic agent A: trade name “Gelall D”, Shin Nippon Rika Co., Ltd. thixotropic agent B: Product name “Sripacs ZHH”, manufactured by Nippon Kasei Co., Ltd.

[Example 1]
An epoxy compound (86% by mass), organic acid amine salt (13% by mass) and thixotropic agent A (1% by mass) were charged into a container and mixed using a three roll to obtain a flux composition.
Thereafter, 40% by mass of the obtained flux composition and 60% by mass of solder powder (100% by mass in total) were put into a container and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 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 1.
[Comparative Examples 1-5]
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 2.

<Evaluation of solder composition>
Evaluation of the solder composition (viscosity, heating sag, melting behavior, solder bump formation (printing on electrode, solid printing), detergency) was performed by the following methods. The results obtained for the examples are shown in Table 1. The results obtained for the comparative example are shown in Table 2.
(1) Viscosity Using a spiral viscometer, the viscosity is measured as follows. First, the solder composition is left at 25 ° C. for 2 to 3 hours. Open the lid of the solder composition container, and gently stir for 1-2 minutes to avoid air contamination with a spatula. Furthermore, the container of the solder composition is placed in a thermostatic bath. Thereafter, the rotational speed is adjusted to 10 rpm, the temperature is set to 25 ° C., and after confirming that the paste sucked into the rotor appears from the discharge port after about 3 minutes, the rotor rotation is stopped and the temperature is kept constant. Wait until After the temperature becomes constant, the rotational speed is adjusted to 10 rpm, and the viscosity value η after 3 minutes is read. Then, the viscosity was evaluated according to the following criteria based on the result of the viscosity value η.
○: Less than 100 Pa · s.
X: 100 Pa · s or more.
(2) Heating sagging Heating sagging was evaluated based on the description in JIS Z 3284 appendices 5 and 7. The heating sagging was evaluated according to the following criteria.
A: 0.2 μm or less.
○: More than 0.2 μm and 0.4 μm or less.
(Triangle | delta): It is more than 0.4 micrometer and 0.6 micrometer or less.
X: More than 0.6 μm.
(3) Melting behavior Using a metal mask (opening: 30 mm × 2 mm, thickness: 50 μm) on a comb-shaped electrode substrate (wiring width: 50 μm, spacing between wirings: 50 μm, number of wirings: 50) A test substrate was obtained by printing. The test substrate is heated with a heating device (reflow simulator) at a temperature rising rate of 1.8 ° C./second from 30 ° C. to 160 ° C. and maintained at 160 ° C. for 10 seconds, and solder The melting behavior of the powder was confirmed. Then, the melting behavior was evaluated according to the following criteria.
○: The sag does not spread and the solder powder melts.
X: After the sagging spread, the solder powder melts and there are solder balls between the spaces.
(4) Solder bump formability (printing on electrodes)
Using a metal mask (opening: opening corresponding to dot-like electrode, thickness: 50 μm) on a substrate having dot-like electrodes (36, material: copper, diameter: 160 μm, electrode pitch: 320 μm) And printed to obtain a test substrate. The electrode after heating this test substrate with a heating apparatus (reflow simulator) was observed under the condition of maintaining the preheat temperature at 100 ° C. for 50 seconds and the peak temperature at 170 ° C. for 10 seconds. And according to the following reference | standard, solder bump formability (printing on an electrode) was evaluated.
○: There is no non-wetting part of the solder bump.
Δ: There are non-wetting portions of the solder bumps, but there are less than 5 places.
X: There are 5 or more non-wetting portions of solder bumps.
(5) Solder bump formability (solid printing)
Printing a solder composition on a substrate having dot-shaped electrodes (36 pieces, material: copper, diameter: 160 μm, electrode pitch: 320 μm) using a metal mask (opening: 30 mm × 2 mm, thickness: 50 μm), A test substrate was obtained. The electrode after heating the test substrate under a condition that the temperature is increased from 30 ° C. to 160 ° C. at a temperature increase rate of 1.8 ° C./second and maintained at 160 ° C. for 10 seconds with a heating device (reflow simulator). Was observed. The solder bump formability (solid printing) was evaluated according to the following criteria.
○: There is no non-wetting part of the solder bump.
Δ: There are non-wetting portions of the solder bumps, but there are less than 5 places.
X: There are 5 or more non-wetting portions of solder bumps.
(6) Detergency The substrate evaluated for solder bump formability (printing on the electrode) is used as a test substrate, and this test substrate is cleaned with a cleaning solution (trade name “Clean Through 750K”, manufactured by Kao Corporation), and its surface Was observed. The detergency was evaluated according to the following criteria.
A: The flux residue is removed.
○: The flux residue is almost removed.
X: The flux residue is not removed.

  As is clear from the results shown in Tables 1 and 2, when a solder composition containing either (A1) an epoxy compound or (A2) an acrylic compound and (B1) an organic acid amine salt is used In Examples 1 to 7, heating sag, melting behavior, solder bump formability (printing on electrodes, solid printing), and cleanability were all good. In such a case, since the viscosity is within an appropriate range, the printability is good. Therefore, according to the present invention, it was confirmed that non-wetting of solder bumps can be sufficiently suppressed while maintaining printability.

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

Claims (5)

(A) a flux composition containing a binder and (B) an activator, and (C) a solder powder,
(A) the binder contains a (A1) epoxy compound,
The (B) activator contains (B1) an organic acid amine salt ,
The weight average molecular weight of the (A1) epoxy compound is 100 or more and 10,000 or less,
The blending amount of the component (A) is 50% by mass to 98% by mass with respect to 100% by mass of the flux composition,
The solder composition for forming a solder bump , wherein the blending amount of the component (B1) is 0.5% by mass or more and 20% by mass or less with respect to 100% by mass of the flux composition . In the solder composition for forming a solder bump according to claim 1,
The solder composition for forming a solder bump, wherein the (A1) epoxy compound is liquid at a temperature of 25 ° C. In the solder composition for forming a solder bump according to claim 1 or 2 ,
(C) The solder powder for forming solder bumps, wherein the solder powder has an average particle size of 10 μm or less. In the solder composition for forming solder bumps according to any one of claims 1 to 3 ,
The solder composition for forming a solder bump, wherein the blending amount of the flux composition is 15% by mass to 50% by mass with respect to 100% by mass of the solder composition. A method for forming solder bumps using the solder composition for forming solder bumps according to any one of claims 1 to 4 ,
A printing step of printing the solder composition on an electrode of an electronic substrate;
A bump forming step of forming a solder bump on the electrode by heating the electronic substrate and melting the solder powder in the solder composition;
And a residue cleaning step of cleaning the flux residue on the electronic substrate.