Core material, electronic component and method for forming bump electrode

The present embodiment relates to a core material, an electronic component having a bump using this core material, and a method for forming a bump electrode.

The present application claims the priority of Japanese Patent Application No. 2020-151742 filed on Sep. 10, 2020, the contents of which are entirely incorporated by reference.

In recent years, with development of a small information device, size of an electronic component mounted on the information device is rapidly being reduced. A ball grid array (BGA) with an electrode disposed on a rear surface of the BGA is applied as the electronic component in order to correspond to narrowing a connection terminal and reducing mounting area according to a demand for miniaturization.

An example of the electronic component to which the BGA is applied includes a semiconductor package. The semiconductor package is configured by sealing a semiconductor chip having an electrode with a resin. A solder bump is formed on the electrode of the semiconductor chip. The solder bump is formed by bonding a solder ball to the electrode of the semiconductor chip. The semiconductor package to which the BGA is applied is mounted on a printed circuit board by bonding the solder bump melted by heating to a conductive land of the printed circuit board. In recent years, in order to meet the demand for higher-density mounting, a three-dimensional high-density mounting in which semiconductor packages are stacked in a height direction has also been developed.

When the semiconductor package obtained with the three-dimensional high-density mounting is the BGA and the solder ball is placed on the electrode of the semiconductor chip and reflowed, the solder ball may be crushed due to weight of the semiconductor package itself. When such a situation occurs, there is a problem that the solder extrudes from electrodes to bring the electrodes into contact with each other, and a short-circuit between the electrodes is caused.

In order to prevent such a short-circuit from occurring, a solder bump that is not crushed due to the weight of the semiconductor package itself and is not deformed when the solder is melted is proposed as a solder ball. Specifically, it is proposed to use a ball molded of metal or a resin as a core, and to use a core material obtained by coating the core with a solder as a solder bump.

Japanese Patent No. 5367924 discloses a solder bump in which a Cu ball is used as a core and a Sn-based solder alloy formed of Sn and Bi is plated on the Cu ball. A plating treatment is performed at a concentration gradient in which a content of Bi contained in a solder plating layer in Japanese Patent No. 5367924 is high on an inner side (inner circumferential side) and is lower as being directed toward an outer side (outer circumferential side).

As in Japanese Patent No. 5367924, when a solder is heated and melted in a state in which a concentration of Bi in the solder plating layer is high on the inner circumferential side and is low on the outer circumferential side, a density of Bi on the inner circumferential side is high. Therefore, the solder begins to be melted from a Bi region on the inner circumferential side. Even when the Bi region on the inner circumferential side is melted, the Bi region on the outer circumferential side has yet to begin to be melted. Therefore, a volume expansion in the Bi region on the inner circumferential side occurs early. Due to a slow volume expansion on the inner and outer circumferential sides, a situation occurs in which a pressure difference is generated between the inner circumferential side and the outer circumferential side (outside air) of Bi, and the pressure difference due to the volume expansion on the inner circumferential side causes the Cu ball, which is a core, to burst open when the outer circumferential side of Bi begins to be melted. The occurrence of the situation has to be avoided. As described above, a defect has been generated in a Cu core ball having a solder plating layer formed of the Sn-based solder alloy formed of Sn and Bi when Bi in the solder plating layer has a concentration gradient.

Japanese Patent No. 6217836 is proposed in order to solve the above-described problems caused in Japanese Patent No. 5367924. In Japanese Patent No. 6217836, in a core material having a solder plating layer formed by plating a (Sn—Bi)-based solder alloy formed of Sn and Bi on a core surface, the core material is provided in which Bi contained in the solder plating layer is distributed in a concentration ratio within a predetermined range of 91.4% to 106.7% in the solder plating layer.

Problem to be Solved by Invention

When a relatively large amount of Ag and Cu are contained in the surface of the solder plating layer, Ag and Cu are locally discolored to black, and the appearance is mottled, which may cause deteriorated appearance quality. As a result of the color becoming black from the viewpoint of yellowness, the yellowness increases, which may cause defect determination in appearance inspection.

As described above, when a relatively large amount of Ag and Cu are contained in the surface of the solder plating layer, the solder plating layer easily reacts with a sulfur component of the plating liquid and oxygen in the air. As a result, oxidation easily proceeds, which tends to easily cause an increased oxide film thickness. When the oxide film thickness increases as described above, dissolution behavior at the time of substrate reflow deteriorates, which may cause a state (ball missing) where the solder ball is detached from the electrode pad or positional deviation.

The present invention provides a core material and so on that is unlikely to be determined to be defective in a visual inspection and can prevent the oxide film thickness from increasing and suppress a bonding defect.

Solution to Problem

[Concept 1]

A core material may comprise:

a core;

a solder layer provided outside the core and being a solder alloy containing Sn and at least any one element of Ag, Cu, Sb, Ni, Co, Ge, Ga, Fe, Al, In, Cd, Zn, Pb, Au, P, S, Si, Ti, Mg, Pd, and Pt; and

a Sn layer provided outside the solder layer,

wherein

the solder layer may have a thickness of 1 μm or more on one side,

the Sn layer may have a thickness of 0.1 μm or more on one side, and

a thickness of the Sn layer may be 0.215% or more and 36% or less of the thickness of the solder layer.

[Concept 2]

In the core material according to concept 1, the solder layer may be a (Sn—Ag—Cu)-based solder.

[Concept 3]

The core material, according to concept 1 or 2, may further comprise a base plating layer made of any one of Ni, Co, Ni—Co, Ni—P and Ni—B between the core and the solder layer.

[Concept 4]

In the core material according to any one of concepts 1 to 3, Cu ball or Cu column may be used as the core.

[Concept 5]

An electronic component may use the core material according to any one of concepts 1 to 4 as a solder bump.

[Concept 6]

A method for forming bump electrode may comprise steps of:

mounting the core material according to any one of concepts 1 to 4 on an electrode;

forming a bump electrode by heating the mounted core material.

According to the present invention, a core material and so on that is unlikely to be determined to be defective in a visual inspection and can prevent the oxide film thickness from increasing and suppress a bonding defect can be provided.

FIG. 1 is a cross-sectional view illustrating an example of a Cu core ball according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating another example of a Cu core ball according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present embodiment will be described in detail. In the embodiment, a core material and an electronic component including a semiconductor package using the core material are provided.

The core material of the present embodiment may include a core; a solder layer provided outside the core and being a solder alloy containing Sn and at least any one element of Ag, Cu, Sb, Ni, Co, Ge, Ga, Fe, Al, In, Cd, Zn, Pb, Au, P, S, Si, Ti, Mg, Pd, and Pt; and a Sn layer provided outside the solder layer. The thickness of the solder layer may be 1 μm or more on one side. The thickness of the Sn layer is considered to be 0.1 to 12 μm on one side, but the upper limit value thereof may exceed 12 μm as long as the thickness of the Sn layer is 0.215% or more and 36% or less of that of the solder layer.

The Sn layer may be formed to have a thickness of preferably 0.26% or more and 33.3% or less of that of the solder layer. In the present embodiment, as an example, a solder plating layer is described as the solder layer to be used, and a Sn plating layer is described as the Sn layer to be used, but the present invention is not limited thereto. The solder layer may be formed by a method other than plating, and similarly, the Sn layer may be formed by a method other than plating. The Sn layer may contain a component other than Sn as an impurity such as Ag, Cu, Bi, Sb, Ni, Co, Ge, Ga, Fe, Al, In, Cd, Zn, Pb, Au, P, S, or Si.

The solder alloy may be a Sn-based solder alloy. The Sn-based solder alloy can include other additive elements in addition to (Sn—Ag)-based and (Sn—Cu)-based solder alloys. The element that can be added to the (Sn—Ag)-based and (Sn—Cu)-based solder alloys is one or two or more elements of Ag, Cu, Ni, Bi, Ge, Ga, In, Zn, Fe, Pb, Sb, Au, Pd, and Co and the like. For example, a (Sn—Ag—Cu—Ni)-based solder alloy and a (Sn—Ag—Sb)-based solder alloy and the like are considered. A Pb-based solder alloy may be used; the content (main component) of Pb may be the largest in mass; a (Pb—Sn)-based solder alloy may be used; and the content of Pb may be more than that of Sn. In Examples to be described later, SAC 305 (Ag 3.0 Cu 0.5 Sn balance), SnAg (Ag 3.5 Sn balance), SnCu (Cu 0.7 Sn balance), SnSb (Sb 10 Sn balance), SnIn (In 45 Sn balance), and SnPb (Pb 37 Sn balance) are used, but the present invention is not limited thereto. For example, for SAC, the content of Ag and the content of Cu may be changed, and Ag 0.1 Cu 0.1 Sn balance to Ag 10 Cu 10 Sn balance may be used. For SnAg, Ag 0.1 Sn balance to Ag 10 Sn balance may be used by changing the content of Ag. For SnCu, Cu 0.1 Sn balance to Cu1Sn balance may be used by changing the content of Cu. For SnSb, Sb 0.1 Sn balance to Sb 15 Sn balance may be used by changing the content of Sb. For SnIn, In 0.1 Sn balance to In 95 Sn balance may be used by changing the content of In. For SnPb, Pb 0.1 Sn balance to Pb 95 Sn balance may be used by changing the content of Pb. In the present application, the numerical value of the addition amount of each element is represented by % by mass. For example, “Ag 3.0 Cu 0.5 Sn balance” indicates that 3.0% by mass of Ag and 0.5% by mass of Cu are contained, the balance being Sn.

The Sn plating layer is formed after the solder plating layer is formed. As an example, a solder plating layer containing Sn and at least any one element of Ag, Cu, Sb, Ni, Co, Ge, Ga, Fe, Al, In, Cd, Zn, Pb, Au, P, S, Si, Ti, Mg, Pd, and Pt on the core is formed. The core material on which the solder plating layer is formed may be pulled up from a molten liquid containing Sn and at least any one element of Ag, Cu, Sb, Ni, Co, Ge, Ga, Fe, Al, In, Cd, Zn, Pb, Au, P, S, Si, Ti, Mg, Pd, and Pt, and then immersed in a molten liquid of Sn to form the Sn plating layer. Both the solder plating layer and the Sn plating layer may be formed using barrel electroplating. Electroless plating may be used as a plating method.

When the Sn plating layer is not provided, and the solder plating layer contains 0.1% by mass or more of a component other than Sn, the problem of discoloration occurs. When the Sn plating layer is not provided, and the solder plating layer is 100% by mass of Sn, the problem of discoloration does not occur, but the problem of discoloration is confirmed to occur when the solder plating layer is made of the following components. In the case of electroplating, if Ag or the like remains in the plating liquid just before the end of solder plating, substitution deposition-based discoloration of the surface is considered to occur.

Ag 0.05 Cu 0.05 Sn balance, discolored

Ag 0.1 Sn balance, discolored

Cu 0.1 Sn balance, discolored

Sb 0.1 Sn balance, discolored

In 0.1 Sn balance, discolored

Pb 0.1 Sn balance, discolored

Metal or a resin is conceivable as the core, and a shape of the core is conceivable to be a sphere or other shape (columnar column, sheet shape, and the like). In the embodiment, a case of a Cu core ball which is a sphere and uses a ball which is, particularly, formed of Cu as the core (also referred to as “Cu ball”) will be described. The Cu core ball in the embodiment only needs to contain Cu in the core, and other configurations are not particularly limited.

A particle diameter (sphere diameter) of the core differs depending on size of the BGA, but in the following example, the core has a spherical shape of about 300 μmφ and a thickness of the solder plating layer on one side in a diameter direction is 1 μm to 100 μm. A thickness of the Sn plating layer on one side in the diameter direction may be determined based on the thickness of the solder plating layer, and as described above the thickness of the Sn plating layer on one side in the diameter direction is 0.215% or more and 36% or less of the thickness of the solder plating layer, preferably 0.26% or more and 33.3% or less of the thickness of the solder plating layer. The particle diameter of the Cu core ball is appropriately selected according to a density and size of the electronic components to be used. Therefore, the core having the particle diameter in a range of 1 μm to 1000 μm can be used, and the plating thickness can be appropriately selected according to the particle diameter of the core to be used. A typical particle diameter when being used as a ball is 200 μm to 300 μm. When the particle diameter is further minimized in the future, a mainstream particle diameter may be 100 μm to 160 μm, and the present application can be used without any problem even with this particle diameter. As a plating apparatus that performs the plating treatment, an electroplating apparatus may be used.

Subsequently, an example of the Cu core ball using the Cu ball as a core will be described. FIGS. 1 and 2 are cross-sectional views illustrating an example of a Cu core ball 10 according to the embodiment of the present invention.

As illustrated in FIG. 2 , in the Cu core ball 10 , a core 12 containing Cu and a solder plating layer 16 formed of the solder alloy are formed via a Ni base plating layer 14 in the example, and a Sn plating layer 20 is formed on the solder plating layer 16 . The Ni base plating layer 14 functions as a base plating (functions as a barrier layer) for preventing a composition change of the solder plating layer 16 due to a metal diffusion between the core 12 and the solder plating layer 16 , and a thickness of the Ni base plating layer 14 on one side is about 1 μm to 4 μm. The Ni base plating layer 14 is not an indispensable requirement, and the solder plating layer 16 can be formed directly on the surface of the core 12 as illustrated in FIG. 1 When forming the base plating layer 14 , the base plating layer 14 may be configured of a layer formed of one element or more selected from the group consisting of Ni, Co, P and B. More specifically, the base plating layer made of any one of Ni, Co, Ni—Co, Ni—P and Ni—B may be provided.

Cu used in the core 12 may be pure copper or an alloy of copper.

When the core 12 having an alloy composition containing Cu as a main component is used, purity of Cu is not particularly limited, but from a viewpoint of suppressing deterioration of electric conductivity and thermal conductivity of the Cu core ball due to a decrease in purity and suppressing α-rays as necessary, the purity of Cu is preferably 99.9% by mass or more.

The core may be formed of a metal simple substance of Ni, Ag, Bi, Pb, Al, Sn, Fe, Zn, In, Ge, Sb, Co, Mn, Au, Si, Pt, Cr, La, Mo, Nb, Pd, Ti, Zr, Mg, an alloy made from two or more of these components, a metal oxide, or a metal mixture oxide in addition to Cu, and may be formed of a resin material. As the resin material, a resin material formed of an amino resin, an acrylic resin, an ethylene-vinyl acetate resin, a styrene-butadiene block copolymer, a polyester resin, a melamine resin, a phenol resin, an alkyd resin, a polyimide resin, a urethane resin, an epoxy resin, a crosslinked resin, or the like is exemplified. Of these, it is preferable to use conductive plastic such as polyacetylene, polypyrrole, polythiophene, and polyaniline. When the core is formed of the resin material, the Cu core ball can be formed by a resin core, a Cu plating layer coating an outer side of the resin core, a base plating layer such as Ni coating a surface of the Cu plating layer, and a solder plating layer coating a surface of the base plating layer. A laminated structure of the Cu core ball is not limited to the above example.

When the core 12 is spherical, from a viewpoint of controlling a stand-off height, sphericity of the core 12 is preferably 0.95 or more, and more preferably 0.990 or more. When the sphericity of the core 12 is less than 0.95, the core 12 has an indefinite shape. Therefore, a bump having a height which is not uniform is formed at the time of forming the bump, and the possibility of causing defective bonding increases. Further, when the Cu core ball 10 is mounted on the electrode and reflowed, and the sphericity is low, the Cu core ball 10 is misaligned and a self-alignment property deteriorates.

Here, the sphericity represents a deviation from the sphere. The sphericity is obtained by various methods such as a least squares center method (LSC method), a minimum zone center method (MZC method), a maximum inscribed center method (MIC method), and a minimum circumscribed center method (MCC method). Specifically, the sphericity is an arithmetic average value calculated when the diameter of each of 500 cores is divided by a long diameter, and the closer the value is to the upper limit of 1.00, the closer to the sphere. The length of the long diameter is a length measured by ULTRA QV350-PRO measurement device (ultra quick vision manufactured by MITUTOYO CORPORATION).

It is preferable that the diameter of the entire Cu core ball 10 including the solder plating layer 16 is 1 μm to 1000 μm. Within this range, the spherical Cu core ball 10 can be stably manufactured, and by selecting the particle diameter, it is possible to suppress a connection short circuit when there is a narrow pitch between the electrode terminals.

The solder plating layer 16 is made of a solder alloy, and includes Sn and at least any one element of Ag, Cu, Sb, Ni, Co, Ge, Ga, Fe, Al, In, Cd, Zn, Pb, Au, P, S, Si, Ti, Mg, Pd, and Pt in the present embodiment.

The thickness of the solder plating layer 16 varies depending on the particle diameter of the core 12 , but the thickness of the solder plating layer 16 on one side in the diameter direction is preferably 100 μm or less. For example, when the core 12 has a particle diameter of 300 μmφ, the solder plating layer 16 is formed so as to have a thickness of 1 μm to 100 μm on one side. This is for securing a sufficient amount of solder bonding.

As the plating liquid, a known plating liquid can be appropriately used according to the solder composition to be formed.

Hereinafter, the embodiment will be described in detail with reference to Examples and Comparative Examples. The embodiment is not limited to these Examples.

As an evaluation of the core ball having a composition shown in each Table which will be described later, an evaluation of yellowness and an evaluation of a defect at the time of bonding were performed based on the following criteria.

<Yellowness>

The yellowness of the core ball was measured by using a CM-2600d spectrophotometer manufactured by KONICA MINOLTA. The yellowness of 8.5 or less in the L*a*b* table color system was set to “Good” and indicated as “0” in each Table. The yellowness of more than 8.5 in the L*a*b* table color system was determined to be “defective” and indicated as “x” in each Table.

<Defect at the Time of Bonding>

Ten core balls (samples) having a composition in each Example and each Comparative Example, which are produced in the same production batch as each sample of which yellowness was measured, were prepared, and each core ball was bonded to a substrate by normal reflow processing. Regarding defects at the time of bonding, a case where a bonding defect was not measured in all the ten samples was indicated as “Good” and indicated as “o” in each Table. On the other hand, a case where misalignment or a ball missing is caused at the time of bonding in even one sample or a case where a core bursts open as the time of bonding in even one sample was determined to be “defective”, and indicated as “x” in Table.

Core balls 10 in Examples and Comparative Examples were prepared under the following conditions.

Diameter of core 12 : 300 μm Film thickness of Ni base plating layer 14 : 2 μm on one side Film thickness of solder plating layer 16 : 1 μm on one side, 18 μm or 38 μm on one side Diameter of core ball 10 excluding Sn plating layer 20 : 306 μm, 340 μm or 380 μm

As a method for plating the Ni base plating layer 14 , an electroplating method (barrel electroplating) was used for a sample having a core made of Cu. An electroless plating method was used for a sample having a core made of a resin. Aluminum as a core was subjected to a double zincate treatment for a sample having a core made of aluminum. Ni plating was thinly applied to the treated aluminum by an electroless plating method, and the Ni plating was then grown to a desired thickness by an electroplating method.

The solder plating layer 16 was plated by an electroplating method (barrel electroplating).

The Sn plating layer 20 was formed by pulling up the core ball including the solder plating layer 16 from a molten liquid containing Sn, Ag and Cu, Cu, Ag, Sb, In or Pb, and then immersing the core ball in a molten liquid of Sn. More specifically, the sample on which the solder plating layer 16 was formed was taken out from a plating liquid containing Sn, Ag and Cu, Cu, Ag, Sb, In or Pb, washed, and dried.

After that, the sample was put into a plating liquid containing methane sulfonic acid Sn, an organic acid and a surfactant, and the barrel electroplating was performed until the sample has the thickness of the Sn plating layer 20 described in each Example and each Comparative example (excluding Comparative example in which the Sn plating layer 20 is not formed).

In the following Table 1, aspects in which copper is used as the material of the core and the solder layer composition is made of SAC 305 are shown as Examples 1 to 9. Also in the following Table 2, aspects in which copper is used as the material of the core and the solder layer composition is made of SAC 305 are shown as Comparative Examples 1 to 9. In Examples 1 to 3 and Comparative Examples 1 to 3, the thickness of the solder layer on one side is 18 μm, but the thicknesses of the Sn layer one side are different from each other. In Examples 4 to 6 and Comparative Examples 4 to 6, the thickness of the solder layer one side is 38 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 7 to 9 and Comparative Examples 7 to 9, the thickness of the solder layer on one side is 1 μm, but the thicknesses of the Sn layer on one side are different from each other. The “Sn layer: solder layer” shown in each Table is calculated by an expression of Sn layer thickness (one side)/solder layer (one side)×100, and is a value obtained by dividing the thickness of the Sn layer on one side by the thickness of the solder layer on one side, and expressed in %. It has the same meaning in the other Tables. The phrase “less than the lower limit value” shown in Tables of Comparative Examples means that the thickness of the Sn layer is less than 0.215% of that of the solder layer, and the phrase “exceeding the upper limit value” shown in Tables of Comparative Examples means that the thickness of the Sn layer exceeds 36% of that of the solder layer. These have the same meanings in the other Tables. In all of Examples 1 to 9, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 1 to 9, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Table 3, aspects in which copper is used as the material of the core and the solder layer composition is made of SnCu (Cu 0.7 Sn balance) are shown as Examples 10 to 18. Also in the following Table 4, aspects in which copper is used as the material of the core and the solder layer composition is made of SnCu are shown as Comparative Examples 10 to 18. In Examples 10 to 12 and Comparative Examples 10 to 12, the thickness of the solder layer on one side is 18 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 13 to 15 and Comparative Examples 13 to 15, the thickness of the solder layer on one side is 38 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 16 to 18 and Comparative Examples 16 to 18, the thickness of the solder layer on one side is 1 μm, but the thicknesses of the Sn layer on one side are different from each other. In all of Examples 10 to 18, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 10 to 18, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Table 5, aspects in which copper is used as the material of the core and the solder layer composition is made of SnAg (Ag 3.5 Sn balance) are shown as Examples 19 to 27. Also in the following Table 6, aspects in which copper is used as the material of the core and the solder layer composition is made of SnAg are shown as Comparative Examples 19 to 27. In Examples 19 to 21 and Comparative Examples 19 to 21, the thickness of the solder layer one side is 18 μm, but the thicknesses of the Sn layer one side are different from each other. In Examples 22 to 24 and Comparative Examples 22 to 24, the thickness of the solder layer on one side is 38 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 25 to 27 and Comparative Examples 25 to 27, the thickness of the solder layer on one side is 1 μm, but the thicknesses of the Sn layer on one side are different from each other. In all of Examples 19 to 27, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 19 to 27, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Table 7, aspects in which copper is used as the material of the core and the solder layer composition is made of SnSb (Sb 10 Sn balance) are shown as Examples 28 to 36. Also in the following Table 8, aspects in which copper is used as the material of the core and the solder layer composition is made of SnSb are shown as Comparative Examples 28 to 36. In Examples 28 to 30 and Comparative Examples 28 to 30, the thickness of the solder layer on one side is 18 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 31 to 33 and Comparative Examples 31 to 33, the thickness of the solder layer on one side is 38 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 34 to 36 and Comparative Examples 34 to 36, the thickness of the solder layer on one side is 1 μm, but the thicknesses of the Sn layer on one side are different from each other. In all of Examples 28 to 36, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 28 to 36, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Table 9, aspects in which copper is used as the material of the core and the solder layer composition is made of SnIn (In 45 Sn balance) is shown as Examples 37 to 45. Also in the following Table 10, aspects in which copper is used as the material of the core and the solder layer composition is made of SnIn are shown as Comparative Examples 37 to 45. In Examples 37 to 39 and Comparative Examples 37 to 39, the thickness of the solder layer on one side is 18 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 40 to 42 and Comparative Examples 40 to 42, the thickness of the solder layer on one side is 38 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 43 to 45 and Comparative Examples 43 to 45, the thickness of the solder layer on one side is 1 μm, but the thicknesses of the Sn layer on one side are different from each other. In all of Examples 37 to 45, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 37 to 45, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Table 11, aspects in which copper is used as the material of the core and the solder layer composition is made of SnPb (Pb 37 Sn balance) are shown as Examples 46 to 54. Also in the following Table 12, aspects in which copper is used as the material of the core and the solder layer composition is made of SnPb are shown as Comparative Examples 46 to 54. In Examples 46 to 48 and Comparative Examples 46 to 48, the thickness of the solder layer on one side is 18 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 49 to 51 and Comparative Examples 49 to 51, the thickness of the solder layer on one side is 38 μm, but the thicknesses of the Sn layer on one side are different from each other. In Examples 52 to 54 and Comparative Examples 52 to 54, the thickness of the solder layer on one side is 1 μm, but the thicknesses of the Sn layer on one side are different from each other. In all of Examples 46 to 54, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 46 to 54, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Tables 13 to 24, the solder layer composition was changed to SAC 305, SnCu (Cu 0.7 Sn balance), SnAg (Ag 3.5 Sn balance), SnSb (Sb 10 Sn balance), SnIn (In 45 Sn balance), and SnPb (Pb 37 Sn balance), and the thickness of the solder layer on one side and the thickness of the Sn layer on one side were changed in the same manner as in Examples 1 to 54 and Comparative Examples 1 to 54 shown in Tables 1 to 12 except that aluminum was used as the material of the core. In all of Examples 55 to 108, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 55 to 108, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

In the following Tables 25 to 36, the solder layer composition was changed to SAC 305, SnCu (Cu 0.75 Sn balance), SnAg (Ag 3.5 Sn balance), SnSb (Sb 10 Sn balance), SnIn (In 45 Sn balance), and SnPb (Pb 37 Sn balance), and the thickness of the solder layer on one side and the thickness of the Sn layer on one side were changed in the same manner as in Examples 1 to 54 and Comparative Examples 1 to 54 shown in Tables 1 to 12, and Examples 55 to 108 and Comparative Examples 55 to 108 shown in Tables 13 to 24 except that a styrene-butadiene block copolymer as a resin was used as the material of the core. In all of Examples 109 to 162, good results could be confirmed to be obtained in each of yellowness and a defect at the time of bonding. Meanwhile, in all of Comparative Examples 109 to 162, any of yellowness and the time of bonding could be confirmed to be poor. In particular, it could be confirmed that when the Sn layer is not provided or when the thickness of the Sn layer is less than 0.215% of that of the solder layer, a problem in yellowness occurs. Meanwhile, it could be confirmed that when the thickness of the Sn layer exceeds 36% of that of the solder layer, a defect at the time of bonding occurs.

The present embodiment also provides a method for forming a bump electrode, the method including the steps of: mounting a core material on an electrode; and forming the bump electrode by heating the mounted core material.

The shape of the core material also includes not only a spherical body but also a columnar column and a sheet and the like. For example, a core column in which a Ni base plating layer and Co base plating layer and the like of 1 to 4 μm on one side are provided on the surface of a Cu column having diameters of top and bottom surfaces of 1 to 1000 μm and a height of 1 to 3000 μm, and in the same condition as that of Examples, the Cu column is covered with a solder plating layer can provide the same effects as those in Examples described above, and good results could be obtained in each of yellowness and a defect at the time of bonding.

As an example, the results of using an aspect in which a column having a diameter φ of 0.30 mm and a height of 0.53 mm is used and the Ni plating thickness is 2 μm on one side are shown below. The thickness of the solder layer is a value not including the Ni plating thickness.

The description of the embodiments, the description of Examples, and the disclosure of the drawings described above are merely examples for describing the invention described in claims. The invention described in claims is not limited by the description of the embodiments or the disclosure of the drawings described above.

10 Cu core ball

12 Core

14 Base plating layer

16 Solder plating layer (solder layer)

20 Sn plating layer (Sn layer)