TWI783150B - Cu nuclei, solder joints, solder paste and foam solder - Google Patents

Abstract

The object of the present invention is to provide a Cu core ball that uses a metal layer to coat the Cu ball, which realizes high sphericity and low hardness and can suppress discoloration. The solution of the present invention is to provide a Cu core ball 11A, which includes a Cu ball 1 and a solder layer 3 covering the surface of the Cu ball 1, and the content of the Cu ball 1 is at least one of Fe, Ag, and Ni. The total is 5.0 mass ppm to 50.0 mass ppm, the S content is 0 mass ppm to 1.0 mass ppm, the P content is 0 mass ppm to less than 3.0 mass ppm, and the rest is Cu and other impurity elements, The purity of the Cu ball 1 is not less than 99.995% by mass and not more than 99.9995% by mass, the true sphericity is not less than 0.95, the solder layer 3 is a (Sn-Sb) based solder alloy containing Sn and Sb, and the content of Sn is not less than 40% by mass.

Description

Cu nuclei, solder joints, solder paste and foam solder

The present invention relates to a Cu core ball formed by coating Cu balls with a metal layer, and a welding head, solder paste and foam solder using the Cu core ball.

In recent years, due to the development of small information devices, the electronic components mounted therein have undergone rapid miniaturization. Due to the requirement of miniaturization, electronic components are applied to Ball Grid Array (hereinafter referred to as "BGA") with electrodes arranged on the back side in response to the miniaturization of connection terminals and miniaturization of packaging area.

Electronic components using BGA are semiconductor components, for example. In semiconductor components, resin is used to seal semiconductor wafers with electrodes. The electrodes of the semiconductor wafer are formed with solder bumps. The solder bumps are formed by bonding solder balls to electrodes of a semiconductor chip. A semiconductor device to which BGA is applied is mounted on a printed board by bonding heated and melted solder bumps to conductive lands of the printed board. Also, in order to meet the demand for further high-density packaging, three-dimensional high-density packaging in which semiconductor elements are stacked in the height direction is being studied.

In the high-density packaging of electronic components, α-rays enter the memory cells of semiconductor integrated circuits (ICs), causing soft errors in which memory content is rewritten. Therefore, in recent years, the development of low-α-ray soldering materials and Cu balls that reduce the content of radioactive isotopes has been carried out. Patent Document 1 discloses Cu balls containing Pb and Bi and having a purity of not less than 99.9% and not more than 99.995% with a low amount of α-rays. Patent Document 2 discloses a Cu ball capable of achieving a purity of 99.9% to 99.995%, a true sphericity of 0.95 or more, and a Vickers hardness of 20HV to 60HV.

However, when the crystal grains of the Cu balls are finer, the Vickers hardness becomes larger, so the durability against external stress becomes lower, and the drop impact resistance deteriorates. Therefore, the Cu ball system used in the packaging of electronic components is required to have predetermined flexibility, that is, a Vickers hardness equal to or less than a predetermined value.

In order to make soft Cu balls, it is common practice to increase the purity of Cu. This is because the impurity elements function as crystal nuclei in the Cu balls, so when there are fewer impurity elements, the crystal grains grow larger, and as a result, the Vickers hardness of the Cu balls becomes smaller. However, when the purity of the Cu ball is increased, the true sphericity of the Cu ball becomes lower.

When the true sphericity of the Cu ball is low, the self-alignment may not be ensured when the Cu ball is packaged on the electrode. At the same time, the height of the Cu ball becomes uneven during the packaging of the semiconductor chip, which may cause bonding failure. situation.

Patent Document 3 discloses a Cu ball with a mass ratio of Cu greater than 99.995%, a sum of P and S mass ratios of 3 ppm or more and 30 ppm or less, and having appropriate true sphericity and Vickers hardness.

In addition, the three-dimensional high-density packaged semiconductor component is BGA. When solder balls are placed on the electrodes of the semiconductor chip and reflowed, the solder balls may collapse due to the weight of the semiconductor component. When such a situation occurs, the solder is extruded from the electrodes, and there is a possibility that the electrodes are in contact with each other and a short circuit occurs between the electrodes.

In order to prevent such short-circuit accidents, there is a proposal to disclose a solder bump that does not collapse due to its own weight or deform when solder is melted. Specifically, a ball formed of metal or the like is used as a core, and a core material obtained by coating the core with solder is used as a solder bump. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent No. 5435182 [Patent Document 2] Japanese Patent No. 5585751 [Patent Document 3] Japanese Patent No. 6256616

However, it is newly known that Cu balls containing more than a predetermined amount of S tend to be discolored by forming sulfides and sulfur oxides when heated. The discoloration of the Cu balls causes poor wettability, and the poor wettability causes non-wetting and deterioration of self-alignment. In this way, Cu balls that are prone to discoloration are not suitable for coating with a metal layer because the adhesion between the Cu ball surface and the metal layer decreases, and the oxidation and reactivity of the metal layer surface become high. On the other hand, when the true sphericity of the Cu ball is low, the true sphericity of the Cu core ball formed by coating the Cu ball with the metal layer also becomes low.

Therefore, the object of the present invention is to provide a Cu core ball that realizes high true sphericity and low hardness and uses Cu balls that can suppress discoloration, and a soldering head, solder paste, and foamed solder using the Cu core ball.

The present invention is as follows. (1) A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm ppm or less, the S content is not less than 0 mass ppm and not more than 1.0 mass ppm, the P content is not less than 0 mass ppm and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, and the purity of Cu balls is not less than 99.995 mass % and 99.9995 mass % or less, true sphericity of 0.95 or more, the solder layer is a (Sn-Sb) solder alloy containing Sn and Sb, and the Sn content is 40 mass % or more. (2) The Cu core ball as described in (1) above, wherein the solder layer is composed of a (Sn-Sb) based solder alloy containing Sn and 0.1 to 30.0% by mass of Sb, and the The concentration ratio (%) of Sb is set as concentration ratio (%)=(measured value (mass %)/target content (mass %))×100, or concentration ratio (%)=(average value of measured value (mass %) / Target content (mass %)) × 100, the concentration ratio is within the range of 70 to 125%.

(3) The Cu core ball as described in the above (1), wherein the solder layer is composed of a (Sn-5Sb) based solder alloy containing Sn and Sb, and the concentration ratio of Sb contained in the solder layer (% ) is set as concentration ratio (%)=(measured value (mass%)/target content (mass%))×100, or concentration ratio (%)=(average value of measured value (mass%)/target content (mass%) ))×100, the concentration ratio is within the range of 73.2 to 117.0%.

(4) The Cu core ball as described in (1) above, wherein the solder layer is composed of a (Sn-10Sb) based solder alloy containing Sn and Sb, and the concentration ratio of Sb contained in the solder layer (% ) is set as concentration ratio (%)=(measured value (mass%)/target content (mass%))×100, or concentration ratio (%)=(average value of measured value (mass%)/target content (mass%) ))×100, the concentration ratio is within the range of 71.9 to 121.4%.

(5) The Cu core sphere described in any one of the above items (1) to (4), wherein the true sphericity is 0.98 or more.

(6) The Cu core sphere described in any one of the above items (1) to (4), wherein the sphericity is 0.99 or more.

(7) The Cu nuclei as described in any one of the above items (1) to (6), wherein the amount of α rays is 0.0200 cph/cm ² or less.

(8) The Cu core sphere according to any one of the above items (1) to (6), wherein the amount of α rays is 0.0010 cph/cm ² or less.

(9) The Cu core ball described in any one of the above items (1) to (8), which has a metal layer covering the surface of the Cu ball, and the surface of the metal layer is covered with a solder layer, and the true sphericity is 0.95 or more .

(10) The Cu core sphere described in (9) above, wherein the sphericity is 0.98 or more.

(11) The Cu core sphere described in (9) above, wherein the sphericity is 0.99 or more.

(12) The Cu core sphere described in any one of the above items (9) to (11), wherein the amount of α ray is 0.0200 cph/cm ² or less.

(13) The Cu core sphere described in any one of the above items (9) to (11), wherein the amount of α rays is 0.0010 cph/cm ² or less.

(14) The Cu core sphere described in any one of the above items (1) to (13), wherein the Cu sphere has a diameter of 1 μm or less Above and below 1000μm.

(15) A welding head using the Cu core ball described in any one of the above items (1) to (14).

(16) A solder paste using the Cu nuclei as described in any one of the above items (1) to (14).

(17) A solder foam using the Cu nuclei as described in any one of the above items (1) to (14).

According to the present invention, the discoloration of Cu balls can be suppressed by realizing high true sphericity and low hardness of Cu balls. By realizing the high sphericity of Cu balls, it is possible to realize the high sphericity of Cu core balls formed by coating Cu balls with a metal layer, and when encapsulating Cu core balls on electrodes, self-alignment can be ensured, Variation in Cu nuclei height can be suppressed. In addition, by realizing the low hardness of the Cu balls, the drop impact resistance can also be improved by using the Cu core balls in which the Cu balls are covered with a metal layer. Furthermore, since discoloration of Cu balls can be suppressed, adverse effects of sulfides and sulfur oxides on Cu balls can be suppressed, and it is suitable for coating with a metal layer and has good wettability.

The present invention will be described in more detail below. In this specification, the units (ppm, ppb, and %) of the composition of the metal layer of the Cu nuclei are, unless otherwise specified, the ratio (mass ppm) relative to the mass of the metal layer. , mass ppb, and mass %). In addition, the units (ppm, ppb, and %) concerning the composition of Cu balls represent ratios (ppm by mass, ppb by mass, and % by mass) relative to the mass of Cu balls unless otherwise specified.

Fig. 1 shows an example of the structure of a Cu core sphere 11A according to the first embodiment of the present invention. As shown in FIG. 1 , a Cu core ball 11A according to the first embodiment of the present invention includes a Cu ball 1 and a solder layer 3 covering the surface of the Cu ball 1 .

Fig. 2 shows an example of the structure of a Cu core ball 11B according to the second embodiment of the present invention. As shown in FIG. 2, the Cu core ball 11B of the second embodiment of the present invention is provided with a Cu ball 1, and the surface of the Cu ball 1 is covered with one or more elements selected from Ni, Co, Fe, and Pd. The metal layer 2 above the layer, and the solder layer 3 covering the surface of the metal layer 2.

FIG. 3 shows an example of the configuration of an electronic component 60 in which a semiconductor semiconductor wafer 10 is mounted on a printed circuit board 40 using Cu nuclei 11A or Cu nuclei 11B according to an embodiment of the present invention. As shown in FIG. 3, the Cu nuclei 11A or Cu nuclei 11B are encapsulated on the electrode 100 of the semiconductor wafer 10 by applying flux to the electrode 100 of the semiconductor wafer 10 and the molten solder layer 3 wets and expands. . In this example, the structure in which the Cu core ball 11A or the Cu core ball 11B is packaged on the electrode 100 of the semiconductor wafer 10 is called a solder bump 30 . The solder bumps 30 of the semiconductor chip 10 are bonded to the electrodes 41 of the printed circuit board 40 through the melted solder layer 3 or the melted solder of the solder paste coated on the electrodes 41 . In this example, the structure in which the solder bump 30 is packaged on the electrode 41 of the printed circuit board 40 is called a soldering head 50 .

In the Cu core balls 11A and 11B of each embodiment, the total content of at least one of Fe, Ag, and Ni in the Cu ball system is 5.0 mass ppm or more and 50.0 mass ppm or less, and the S content is 0 mass ppm or more and 1.0 mass ppm or more. The content of P is not less than 0 mass ppm and less than 3.0 mass ppm, and the rest is Cu and other impurity elements. The sphericity is above 0.95.

The Cu core ball 11A according to the first embodiment of the present invention can increase the true sphericity of the Cu core ball 11A by increasing the true sphericity of the Cu ball 1 covered with the solder layer 3 . Furthermore, the Cu nuclei ball 11B according to the second embodiment of the present invention can increase the true sphericity of the Cu nuclei ball 11B by increasing the true sphericity of the Cu ball 1 covered with the metal layer 2 and the solder layer 3 . A preferred aspect of the Cu balls 1 constituting the Cu core balls 11A and 11B will be described below.

‧True sphericity of Cu ball: above 0.95 In the present invention, the so-called true sphericity system means a deviation from a true sphere. True sphericity means the arithmetic mean value calculated by dividing the diameter of 500 Cu balls by the long diameter, and the value means that the closer to the upper limit of 1.00, the closer to a true sphere. The true sphericity system is obtained by various methods such as the least square center method (LSC method), the minimum zone center method (MZC method), the maximum inscribed center method (MIC method), and the minimum circumscribed center method (MCC method). . In the present invention, the length of the major diameter and the length of the diameter refer to lengths measured using Ultra Quick Vision and ULTRA QV350-PRO measuring devices manufactured by Mitutoyo Corporation.

From the perspective of maintaining an appropriate space between the substrates, Cu ball 1 has a true sphericity of 0.95 or higher, a true sphericity of 0.98 or higher, and more preferably 0.99 or higher. The true sphericity of Cu ball 1 is When the degree is less than 0.95, since the Cu ball 1 becomes an indeterminate shape, the possibility of forming bumps with uneven heights during bump formation and causing poor bonding increases. When the true sphericity is 0.95 or more, since the Cu ball 1 system does not melt at the welding temperature, it is possible to suppress the variation in the height of the solder joint 50 . Thereby, bonding failure of the semiconductor wafer 10 and the printed circuit board 40 can be reliably prevented.

‧Purity of Cu balls: more than 99.995% by mass and less than 99.9995% by mass Generally, compared with Cu with higher purity, Cu with lower purity can ensure the impurity element in Cu that becomes the crystallization nucleus of Cu ball 1 , so the degree of true sphericity is higher. On the other hand, the electrical conductivity and thermal conductivity of Cu balls 1 with lower purity deteriorate.

Therefore, when the purity of the Cu ball 1 series is 99.995 mass % (4N5) or more and 99.9995 mass % (5N5) or less, sufficient true sphericity can be ensured. In addition, when the purity of Cu ball 1 is not less than 4N5 and not more than 5N5, not only the amount of α rays can be sufficiently reduced, but also the deterioration of electrical conductivity and thermal conductivity of Cu ball 1 caused by the decrease in purity can be suppressed.

When manufacturing the Cu ball 1, the Cu material, which is an example of a metal material formed into a small piece of a predetermined shape, is melted by heating, and the molten Cu becomes spherical by surface tension, and is solidified by rapid cooling to become a Cu ball. 1. In the process of solidification of molten Cu from a liquid state, crystal grains grow in spherical molten Cu. At this time, when there are many impurity elements, the impurity elements serve as crystal nuclei and suppress the growth of crystal grains. Therefore, the spherical molten Cu system becomes the Cu ball 1 with high true sphericity due to the growth-suppressed fine crystal grains. On the other hand, when there are few impurity elements, there are relatively few substances that become crystal nuclei, so grain growth is not suppressed and grows with a certain direction. As a result, a part of the spherical molten Cu-based surface protruded and solidified, and the true sphericity decreased. As impurity elements, Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au, U, Th, etc. can be considered.

Hereinafter, the content of impurities that regulate the purity and true sphericity of the Cu ball 1 will be described.

‧The total content of at least one of Fe, Ag, and Ni: 5.0 mass ppm or more and 50.0 mass ppm or less Among the impurity elements contained in the Cu ball 1 , the total content of at least one of Fe, Ag, and Ni is particularly preferably 5.0 mass ppm or more and 50.0 mass ppm or less. That is, when any one of Fe, Ag, and Ni is contained, the content of one of them is preferably 5.0 mass ppm or more and 50.0 mass ppm or less, and when two or more of Fe, Ag, and Ni are contained, the content of two or more The total content of is preferably not less than 5.0 mass ppm and not more than 50.0 mass ppm. Since Fe, Ag, and Ni become crystallization nuclei during the melting of the Cu ball 1 manufacturing step, Cu balls 1 with high true sphericity can be manufactured when a certain amount of Fe, Ag, or Ni is contained in Cu. Therefore, at least one of Fe, Ag, and Ni is an important element for estimating the content of impurity elements. In addition, when the total content of at least one of Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, not only can the discoloration of the Cu ball 1 be suppressed, but also after the Cu ball 1 is slowly heated, the Cu ball 1 is slowly heated. Slow cooling can achieve the desired Vickers hardness even without performing an annealing step to slowly recrystallize the Cu balls 1 .

‧The content of S is not less than 0 mass ppm and not more than 1.0 mass ppm Cu balls 1 containing more than a predetermined amount of S tend to discolor when heated by forming sulfides and sulfur oxides and have low wettability. Therefore, the S content must be 0 mass ppm or more and 1.0 mass ppm or less. The Cu ball 1 formed with more sulfide and sulfur oxide, the darker the brightness of the surface of the Cu ball becomes. Therefore, as will be described in detail later, when the result of measuring the brightness of the Cu ball surface is below a predetermined value, the formation of sulfide and sulfur oxide can be suppressed and wettability can be judged to be good.

‧P content is 0 mass ppm or more and less than 3.0 mass ppm The P system changes into phosphoric acid or into a Cu complex, which may adversely affect the Cu ball 1 . Also, since the hardness of Cu ball 1 series containing P in a predetermined amount increases, the content of P is preferably not less than 0 mass ppm and less than 3.0 mass ppm, more preferably less than 1.0 mass ppm.

‧Other impurity elements The content of impurity elements such as Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au (hereinafter referred to as "other impurity elements") other than the above-mentioned impurity elements contained in the Cu ball 1 is determined by It is preferably not less than 0 mass ppm and less than 50.0 mass ppm.

In addition, the Cu ball 1 system contains at least one of Fe, Ag, and Ni as an essential element as described above. However, the Cu ball 1 system cannot prevent the mixing of elements other than Fe, Ag, and Ni according to the current technology, so it substantially contains other impurity elements other than Fe, Ag, and Ni. However, when the content of other impurity elements is less than 1 mass ppm, the effects and influences of adding each element are not easily manifested. In addition, when analyzing the elements contained in the Cu ball, if the content of impurity elements is less than 1 mass ppm, the value is below the detection limit of the analyzer used. Therefore, when the total content of at least one of Fe, Ag, and Ni is 50 mass ppm, and the content of other impurity elements is less than 1 mass ppm, the purity of Cu ball 1 is substantially 4N5 (99.995 mass %). Also, when the total content of at least one of Fe, Ag, and Ni is 5 mass ppm, and the content of other impurity elements is less than 1 mass ppm, the purity of Cu ball 1 is substantially 5N5 (99.9995 mass %).

‧Vickers hardness of Cu ball: below 55.5HV The Vickers hardness of the Cu ball 1 is preferably below 55.5HV. When the Vickers hardness is high, durability against external stress decreases, drop impact resistance deteriorates, and cracks tend to occur. In addition, when an auxiliary force such as pressurization is applied during the formation of bumps and joints for three-dimensional packaging, electrode collapse may occur when relatively hard Cu balls are used. In addition, when the Vickers hardness of the Cu ball 1 is high, the crystal grains become smaller than a certain value, which may cause deterioration of electrical conductivity. When the Vickers hardness of the Cu ball 1 is 55.5 HV or less, the drop impact resistance is also good, cracks can be suppressed, electrode collapse and the like can be suppressed, and conductivity deterioration can also be suppressed. In this embodiment, the lower limit of the Vickers hardness may be greater than 0HV, preferably above 20HV.

‧Radiation α of Cu balls: below 0.0200cph/cm ² For high-density packaging of electronic parts, in order to set the amount of radiation to the extent that soft errors do not become a problem, the amount of α radiation of Cu ball 1 is preferably below 0.0200cph/cm ² . From the viewpoint of suppressing soft errors in further high-density packaging, the α radiation dose is preferably 0.0100 cph/cm ² or less, preferably 0.0050 cph/cm ² or less, more preferably 0.0020 cph/cm ² or less, and most preferably 0.0020 cph/cm 2 or less. 0.0010cph/cm ² or less. In order to suppress soft errors caused by α radiation, the content of radioactive isotopes such as U and Th is preferably less than 5 mass ppb.

‧Resistance to discoloration: the brightness is above 55 The brightness of the Cu ball 1 is preferably above 55. The so-called L* value of the brightness system L*a*b* color system. Since the luminance of the Cu ball 1 having S-derived sulfides and oxysulfides formed on the surface decreases, it can be said that sulfides and oxysulfides can be suppressed when the luminance is 55 or higher. Also, the Cu ball 1 series having a luminance of 55 or higher has good wettability during packaging. On the other hand, when the brightness of the Cu ball 1 is less than 55, it can be said that the formation of the Cu ball 1 of sulfide and sulfur oxide cannot be sufficiently suppressed. Sulfides and sulfur oxides not only adversely affect Cu balls 1, but also deteriorate wettability when, for example, Cu balls 1 are directly bonded to electrodes. Deterioration of wettability causes generation of non-wetting and deterioration of self-alignment.

‧Cu ball diameter: 1 μm or more and 1000 μm or less

The diameter of the Cu ball 1 is preferably not less than 1 μm and not more than 1000 μm, more preferably not less than 50 μm and not more than 300 μm. In this range, the spherical Cu ball 1 can be manufactured stably, and connection short circuit can be suppressed when the pitch between the terminals is narrow. Here, for example, when Cu balls 1 are used in paste, "Cu balls" may also be called "Cu powder". When "Cu ball" is used in "Cu powder", the diameter of Cu ball is usually 1~300μm.

Next, the Cu core ball 11A in the first embodiment of the present invention, the solder layer 3 covering the Cu ball 1, and the Cu core ball 11B in the second embodiment, the solder layer 3 covering the metal layer 2 will be described.

‧Solder layer

The Cu nuclei 11A and 11B in each embodiment of the present invention are Cu nuclei in which Sb in the solder layer 3 is distributed homogeneously; and solder joints, solder pastes, and foamed solders using the Cu nuclei are provided.

The composition of the solder layer 3 according to the embodiment of the present invention is composed of a (Sn—Sb) alloy containing Sn and Sb. The content of Sn is preferably 40.0% by mass or more based on the entire alloy. Regarding the Sb content, when the Sb amount is in the range of 0.1 to 30.0% by mass relative to the entire alloy, the Sb concentration ratio can be controlled within a predetermined range of 70.0 to 125.0 and the Sb distribution in the solder layer 3 can be made uniform.

For example, when the target value of the Sb content is 5.0% by mass, the allowable range of the Sb content and concentration ratio is 3.66% by mass (73.2% concentration ratio) to 5.85% by mass (117.0% concentration ratio), and the Sb concentration ratio can be adjusted to Controlling it within a predetermined range of 70.0 to 125.0% can make the Sb distribution in the solder layer 3 homogeneous. A solder alloy in which the Sb content of the target value is 5.0% by mass is referred to as a (Sn-5Sb)-based solder alloy.

Also, when the target value of the Sb content is 10.0% by mass, the allowable range of the Sb content and the concentration ratio is 7.19% by mass (71.9% concentration ratio) to 12.14% by mass (121.4% concentration ratio), and the Sb concentration ratio can be adjusted to Controlling it within a predetermined range of 70.0 to 125.0% can make the Sb distribution in the solder layer 3 homogeneous. A solder alloy having a target Sb content of 10.0% by mass is referred to as a (Sn-10Sb)-based solder alloy.

In addition, the "permissible range" refers to a range in which soldering such as bump formation can be performed without any problem within this range. Also, the concentration ratio (%) is the ratio (%) of the measured value (mass %) to the target content (mass %), or the average value (mass %) of the measured value of the target content (mass %) . That is, the concentration ratio (%) can be expressed as Concentration ratio (%)=(measurement value (mass%)/target content (mass%))×100 or, Concentration ratio (%) = (average value of measured value (mass %)/target content (mass %)) × 100.

Furthermore, even if other additive elements are added to the binary solder layer 3 composed of Sn and Sb, the concentration ratio of Sb can be controlled within a predetermined range of 70.0 to 125.0%.

As an additive element, one or two or more of Ag, Cu, Ni, Ge, Ga, In, Zn, Fe, Pb, Bi, Au, Pd, Co, etc. can be used.

As mentioned above, the Sb content in the solder layer 3 is about 3.66 mass % (concentration ratio 73.2%) to 5.85 mass % (concentration ratio 117.0%) as an allowable range relative to the target value of 5 mass %. Also, the Sb content in the solder layer 3 is preferably about 7.19 mass % (concentration ratio 71.9%) to 12.14 mass % (concentration ratio 121.4%) as an allowable range with respect to the target value of 10 mass %.

The thickness of the solder layer 3 also varies according to the particle size of the Cu balls 1. In order to ensure a sufficient amount of soldering, one side in the radial direction is preferably 100 μm or less. The solder layer 3 can be formed by conventional electroplating or electroless plating, but when the solder layer is formed by hot-dip plating, the thickness of the solder layer becomes uneven when the particle size of the Cu balls becomes small, and the Cu core balls The eccentricity of the Cu balls and the unevenness on the surface of the solder layer become large, and the true sphericity of the Cu nuclei balls decreases. Therefore, the solder layer 3 is formed by electroplating.

When forming a solder layer composed of a Sn-Sb based solder alloy composed of Sn and Sb by electroplating, since Sb is preferentially accommodated in the solder layer over Sn, there is a difference between the concentration of Sb in the plating solution and the concentration in the solder layer. The problem of inconsistency in the amount of Sb, and it is impossible to form a solder layer with a uniform concentration distribution of Sb. Therefore, as shown in FIG. 4 , electroplating was performed by adjusting the concentration of Sb in the solution so that the Sb concentration in the solution was uniform while applying a predetermined DC voltage between the anode electrode and the cathode electrode.

The process of forming the solder layer 3 by this plating process will be described in more detail with reference to FIG. 4 . FIG. 4 is a characteristic graph showing the relationship between the thickness of the solder layer 3 and the concentration of Sb in the solder layer 3 (curve L) based on the diameter of the Cu nuclei.

In this example, there is a case where a particle diameter of 215 μm is used as the initial value of Cu balls. The thickness of the solder layer 3 is carefully controlled. In this example, the thickness of the solder layer 3 is increased sequentially by a predetermined value, and Cu nuclei are collected each time as a sample. After the collected sample was washed and dried, the particle size was measured.

When the particle size of the Cu nuclei in the measurement sequence becomes the target value and the Sb content in the solder layer is sequentially measured, the result shown in the curve L in Fig. 4 can be obtained. As a result, it was found that the solder layers were sequentially increased by a predetermined thickness, and that the Sb content at this time was approximately the same as the previous content. The Sb content in the curve L is about 4.0 to 7.0% by mass. Therefore, from the curve L in FIG. 4 , it can be understood that the concentration distribution of Sb is homogeneous (equal) with respect to the plating thickness and no concentration gradient can be obtained. As above, the film thickness can be uniformly controlled. On the other hand, for the problem of electroplating with uneven concentration, by controlling the Sb concentration in the solder layer so that the Sb concentration ratio falls within a predetermined range, it is possible to obtain a solder layer with Sb. Homogenously distributed Cu nuclei in the solder layer.

Fig. 5 is an enlarged sectional view of a Cu nuclei sphere. FIG. 5 shows a Cu core ball 11B in which the Cu ball 1 is covered with the metal layer 2 and the metal layer 2 is covered with the solder layer 3 . From Fig. 5, it can be seen clearly that the Sn and Sb systems of the solder layer 3 grow while being homogeneously doped.

In addition, FIG. 6 is an enlarged view of the surface of a Cu core sphere. Since the outermost surface of the solder layer 3 covering the Cu nuclei balls 11A and 11B is closer to the state of a single metal, the crystal grains become larger, so the true sphericity of the Cu nuclei balls tends to decrease. On the other hand, since Sb in the solder layer is in a substantially homogeneously distributed state, the outermost surface of the solder layer is not a single metal but is in an alloy state and the crystal grains become small. Accordingly, the true sphericity of the Cu nuclei is higher than 0.99. When the true sphericity of the Cu nuclei is 0.95 or more, when the Cu nuclei are mounted on the electrode and reflowed, the positional displacement of the Cu nuclei can be suppressed and the self-alignment can be improved.

Since the Sb concentration in the solder layer remains approximately the same even when the thickness of the solder layer grows, it is clear that Sb in the solder layer grows (precipitates) in a substantially uniform distribution state. The electroplating treatment can be performed in a state where the Sb concentration in the electroplating solution is made homogeneous so that the Sb concentration falls within a desired value. In this example, since the Sb content in the solder layer is a target value of 5% by mass, the Sb concentration in the plating solution can be controlled so as to reach the target value.

In order to make the Sb concentration distribution in the solder layer fall into the expected value, the electroplating process is performed while controlling the voltage and current. The distribution of Sb in the solder layer can be maintained at a desired value by such plating treatment.

Cu nuclei balls 11A, 11B can also be composed of Cu nuclei balls 11A, 11B with low α ray content by using a solder alloy with low α ray content in solder layer 3 .

Next, the metal layer 2 covering the Cu ball 1 of the Cu core ball 11B according to the second embodiment of the present invention will be described.

‧Metal layer The metal layer 2 is composed of, for example, two or more Ni plating layers, Co plating layers, Fe plating layers, Pd plating layers, or plating layers (single layer or multiple layers) containing elements of Ni, Co, Fe, and Pd. Because the metal layer 2 does not melt and remains at the soldering temperature when the Cu core ball 11B is used on the solder bump, and contributes to the height of the solder joint, it can have a high degree of true sphericity and a small deviation in diameter And constitute. Also, from the viewpoint of suppressing soft errors, it can be configured to reduce the amount of α rays.

‧Composition and film layer of metal layer The composition of the metal layer 2 is that when the metal layer 2 is formed using a single Ni, Co, Fe, or Pd, Ni, Co, Fe, and Pd are 100% except for unavoidable impurities. In addition, the metal system used in the metal layer 2 is not limited to a single metal, and an alloy obtained by combining two or more elements from Ni, Co, Fe, or Pd may be used. In addition, the metal layer 2 may be a layer composed of a single Ni, Co, Fe, or Pd, or may be a layer composed of an alloy in which two or more elements are combined from Ni, Co, Fe, or Pd. It is composed of multiple layers. The film thickness T2 of the metal layer 2 is, for example, 1 μm to 20 μm.

‧Amount of α line of Cu nuclei: below 0.0200cph/cm ²

The amount of α rays of the Cu core ball 11A of the first embodiment and the Cu core ball 11B of the second embodiment of the present invention is preferably 0.0200 cph/cm ² or less. This is the alpha amount to the extent that soft errors are not a problem in high-density packaging of electronic parts. The α-ray dose of the Cu nuclei ball 11A according to the first embodiment of the present invention can be achieved when the α-ray dose of the solder layer 3 constituting the Cu nuclei ball 11A is 0.0200 cph/cm ² or less. Therefore, since the Cu core ball 11A according to the first embodiment of the present invention is coated with such a solder layer 3, it exhibits a relatively low amount of α rays. The α radiation dose of the Cu nuclei ball 11B according to the second embodiment of the present invention can be achieved when the α radiation dose of the metal layer 2 and the solder layer 3 constituting the Cu nuclei ball 11B is 0.0200 cph/cm ² or less. Therefore, the Cu core ball 11B according to the second embodiment of the present invention is coated with such a metal layer 2 and a solder layer 3, and therefore exhibits a relatively low amount of α radiation. From the viewpoint of suppressing soft errors in further high-density packaging, the α radiation dose is preferably 0.0100 cph/cm ² or less, preferably 0.0050 cph/cm ² or less, more preferably 0.0020 cph/cm ² or less, and most preferably 0.0020 cph/cm 2 or less. 0.0010cph/cm ² or less. In order to make the amount of α rays of the Cu ball 1 0.0200 cph/cm ² or less, the contents of U and Th in the metal layer 2 and the solder layer 3 are each 5 ppb or less. Also, from the viewpoint of suppressing soft errors in present or future high-density packaging, the contents of U and Th are preferably 2 ppb or less each.

‧True sphericity of Cu nuclei: 0.95 or more

The Cu core ball 11A of the first embodiment of the present invention in which the Cu ball 1 is coated with the solder layer 3 and the Cu core ball 11B of the second embodiment of the present invention in which the Cu ball 1 is coated with the metal layer 2 and the solder layer 3 The sphericity is preferably above 0.95, the true sphericity is preferably above 0.98, and more preferably above 0.99. When the true sphericity of the Cu nuclei 11A, 11B is less than 0.95, since the Cu nuclei 11A, 11B become indeterminate shapes, when the Cu nuclei 11A, 11B are mounted on the electrodes and reflowed, the Cu nuclei 11A, 11B are misaligned. shift and self-alignment also deteriorates. When the true sphericity of the Cu nuclei balls 11A, 11B is 0.95 or more, self-alignment when the Cu nuclei balls 11A, 11B are packaged on the electrode 100 of the semiconductor wafer 10 or the like can be ensured. Furthermore, since the true sphericity of Cu ball 1 is also 0.95 or more, since Cu nuclei balls 11A and 11B do not melt at the temperature at which Cu ball 1 and metal layer 2 are soldered, variations in the height of solder joint 50 can be suppressed. Thereby, bonding failure of the semiconductor wafer 10 and the printed circuit board 40 can be reliably prevented.

‧Barrier function of the metal layer During reflow, in the solder (paste) used to connect the Cu core ball and the electrode, when Cu of the Cu ball diffuses, a large amount of thinner is formed in the solder layer and at the interface. Hard and brittle Cu ₆ Sn ₅ , Cu ₃ Sn intermetallic compounds may develop cracks and destroy the connection part when impacted. Therefore, in order to obtain sufficient connection strength, it is only necessary to suppress (block) the diffusion of Cu from the Cu balls to the solder. Therefore, in the Cu core ball 11B of the second embodiment, since the metal layer 2 functioning as a barrier layer is formed on the surface of the Cu ball 1 , it is possible to suppress the diffusion of Cu in the Cu ball 1 into the solder of the paste.

‧Solder paste, foam solder, solder joint In addition, it is also possible to constitute a solder paste by adding Cu nuclei spheres 11A or Cu nuclei spheres 11B to the solder. The foamed solder can be formed by dispersing the Cu nuclei 11A or the Cu nuclei 11B in the solder. The Cu core ball 11A or the Cu core ball 11B can also be used to form a solder joint for connecting electrodes.

‧Cu ball manufacturing method Next, an example of a method of manufacturing Cu ball 1 will be described. As an example of a metal material, a Cu material is placed on a heat-resistant plate such as ceramics (hereinafter referred to as “heat-resistant plate”) and heated in a furnace together with the heat-resistant plate. The bottom of the heat-resistant plate is provided with many hemispherical circular grooves. The diameter and depth of the groove can be appropriately set according to the particle diameter of the Cu ball 1, for example, the diameter is 0.8 mm and the depth is 0.88 mm. In addition, wafer-shaped Cu materials obtained by cutting Cu fine wires were thrown into the grooves of the heat-resistant plate one at a time. A heat-resistant plate with Cu material is put into the ditch, and the temperature is raised to 1100~1300°C in a furnace filled with ammonia decomposition gas and heat-treated for 30~60 minutes. At this time, when the temperature in the furnace is equal to or higher than the melting point of Cu, the Cu material is melted and becomes spherical. Subsequently, the furnace was cooled and shaped by quenching Cu balls 1 in the grooves of the heat-resistant plate.

Also, as another method, there is an atomization method in which molten Cu is dropped from an orifice provided at the bottom of the crucible, and the droplet is cooled to room temperature (for example, 25° C.) to form Cu balls 1; and thermoelectric Slurry heating Cu cutting metal to above 1000 ℃ and pelletizing method.

In the manufacturing method of the Cu ball 1 , before forming the Cu ball 1 by pelletizing, the Cu material, which is the raw material of the Cu ball 1 , may be heat-treated at 800-1000° C.

As a Cu material as a raw material of the Cu ball 1 , for example, a nugget material, a metal wire material, a plate material, or the like can be used. From the viewpoint of not excessively reducing the purity of the Cu ball 1 , the purity of the Cu material may be greater than 4N5 and less than or equal to 6N.

In this way, when using a high-purity Cu material, it is not necessary to perform the above-mentioned heat treatment, and the holding temperature of molten Cu can be lowered to about 1000° C. as before. In this way, the aforementioned heat treatment system can be appropriately omitted or changed according to the purity of the Cu material and the amount of α radiation. In addition, when producing Cu balls 1 with high α-ray content and irregular-shaped Cu balls 1, these Cu balls 1 can be reused as raw materials and the α-ray content can be reduced.

As a method of forming the solder layer 3 on the produced Cu ball 1, the above-mentioned electroplating method or electroless plating method can be employed.

As a method of forming the metal layer 2 on the produced Cu ball 1, a known method such as an electrolytic plating method can be used. For example, when forming a Ni-plated layer, the Ni-plated layer is formed by using a Ni metal block (bullion) or a Ni metal salt to prepare a Ni-plated solution for the Ni-plated bath, immersing Cu balls 1 and making it precipitate. The surface of Cu ball 1. In addition, as another method of forming the metal layer 2 such as a Ni plating layer, a known electroless plating method or the like can also be employed. When forming the solder layer 3 on the surface of the metal layer 2 using a Sn alloy, the above-mentioned electroplating method or electroless plating method can be used. [Example]

Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto. Cu balls of Examples 1 to 19 and Comparative Examples 1 to 12 were manufactured using the compositions shown in Table 1 and Table 2 below, and the true sphericity, Vickers hardness, α ray content, and discoloration resistance of the Cu balls were measured.

In addition, the Cu balls of Examples 1 to 19 described above were coated with the solder layer of the solder alloy of the composition examples 1 to 2 shown in Table 3 to manufacture Cu core balls of Examples 1A to 19A, and the Cu core balls of the Cu core balls were measured. true sphericity. Furthermore, the Cu balls of Examples 1 to 19 described above were coated with a metal layer and a solder layer using the solder alloys of the composition examples 1 to 2 shown in Table 4 to manufacture Cu core balls of Examples 1B to 19B, and the Cu nuclei of Examples 1B to 19B were measured. True sphericity of the nuclei.

Furthermore, by coating the Cu balls of the above-mentioned Comparative Examples 1 to 12 with the solder layer of the solder alloys of the composition examples 1 to 2 shown in Table 5, the Cu core balls of Comparative Examples 1A to 12A were manufactured and the true diameter of the Cu core balls was measured. Sphericity. Also, by coating the Cu balls of Comparative Examples 1 to 12 with a metal layer and a solder layer of the solder alloys of Composition Examples 1 to 2 shown in Table 6, Cu core balls of Comparative Examples 1B to 12B were manufactured and the Cu core balls were measured. True sphericity of the ball.

In the following tables, numbers without units represent mass ppm or mass ppb. Specifically, the values in the tables showing the content ratios of Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, and Au represent ppm by mass. ">1" means that the content ratio of the impurity element to the Cu ball is less than 1 mass ppm. In addition, the numerical values showing the content ratio of U and Th in the table represent mass ppb. ">5" means that the content ratio of the impurity element to the Cu ball is less than 5 mass ppb. The "total amount of impurities" indicates the total ratio of impurity elements contained in Cu balls.

‧Manufacture of Cu balls Study the manufacturing conditions of Cu balls. As an example of a metal material, a Cu material is prepared as a bulk metal material. As the Cu material of Examples 1 to 13 and 19 and Comparative Examples 1 to 12, a product with a purity of 6N was used, and as the Cu material of Examples 14 to 18, a material with a purity of 5N was used. After putting each Cu material into the crucible, the temperature of the crucible was raised to 1200° C. and heated for 45 minutes to melt the Cu material, and the molten Cu was dropped from an orifice provided at the bottom of the crucible and the resulting droplet was rapidly cooled to At room temperature (18°C) to form spheres into Cu spheres. Thereby, the Cu ball whose average particle diameter became the value shown in each following table was manufactured. The elemental analysis system can be analyzed with high precision using inductively coupled plasma mass spectrometry (ICP-MS analysis) and glow discharge mass spectrometry (GD-MS analysis). In this example, the diameters of the Cu balls analyzed by ICP-MS were all set to 250 μm in Examples 1 to 19 and Comparative Examples 1 to 12.

‧Manufacture of Cu nuclei

Using the Cu balls of Examples 1 to 19 above, for Examples 1A to 19A, the thickness of one side is 23 μm and the solder alloy of Composition Examples 1 to 2 is used to form a solder layer by electroplating to manufacture Examples 1A to 19A. 19A Cu nuclei.

In addition, using the Cu balls of Examples 1 to 19 above, for Examples 1B to 19B, a Ni plating layer was formed as a metal layer with a thickness of 2 μm on one side, and a thickness of 23 μm on one side was used in Composition Examples 1 to 2. A solder alloy was used to form a solder layer by electroplating to manufacture Cu nuclei in Examples 1B to 19B.

Then, using the Cu balls of Comparative Examples 1 to 12, the Cu core balls of Comparative Examples 1A to 12A were produced by forming a solder layer with a thickness of 23 μm on one side and using the solder alloy of Composition Examples 1 to 2. In addition, using the Cu balls of Comparative Examples 1 to 12 above, a Ni plating layer was formed as a metal layer with a thickness of 2 μm on one side, and a solder layer was formed with a thickness of 23 μm on one side using the solder alloys of Composition Examples 1 to 2 to manufacture comparative Example 1B~12B of Cu nuclei.

Hereinafter, each evaluation method of the true sphericity of Cu balls and Cu core balls, the amount of α rays of Cu balls, the Vickers hardness, and the resistance to discoloration will be described in detail.

‧True sphericity

The true sphericity of Cu spheres and Cu core spheres is measured using a CNC image measuring system. The apparatuses were Ultra Quick Vision and ULTRA QV350-PRO manufactured by Mitutoyo Corporation.

[Evaluation criteria for true sphericity]

In each of the following tables, the evaluation criteria of the true sphericity of Cu balls and Cu core balls are as follows.

○○○: true sphericity is above 0.99

○○: true sphericity is 0.98 or more and less than 0.99

○: True sphericity is 0.95 or more and less than 0.98

╳: true sphericity is less than 0.95

‧Vickers hardness The Vickers hardness of the Cu ball was measured in accordance with "Vickers hardness test-test method JIS Z2244". As the apparatus, a micro-Vickers hardness tester manufactured by Akashi Seisakusho, AKASHI micro-hardness tester MVK-F 12001-Q was used.

[Evaluation criteria for Vickers hardness] In each of the following tables, the evaluation criteria of the Vickers hardness of Cu balls are as follows. ○: Greater than 0HV and below 55.5HV ╳: Greater than 55.5HV

‧α amount The method of measuring the amount of α rays of Cu balls is as follows. The measurement of the amount of α-rays uses an α-ray measuring device using an air flow proportional counter. The measurement sample is placed in a flat shallow container of 300mm×300mm, and the Cu balls are covered until the bottom of the container cannot be seen. This measurement sample was placed in an α ray measuring device and left to stand in the airflow of PR-10 for 24 hours, and then the amount of α ray was measured.

[Evaluation Criteria for α Radiation Amount] In each of the following tables, the evaluation criteria for the α ray amount of Cu balls are as follows. ○: The amount of α-line is less than 0.0200cph/cm ² ╳: The amount of α-line is greater than 0.0200cph/cm ²

In addition, the PR-10 gas (argon 90%-methane 10%) used for the measurement was filled with the PR-10 gas in the gas high-pressure tank for more than 3 weeks. The high-pressure tanks that have been used for more than 3 weeks are in accordance with the JEDEC STANDARD-Alpha Radiation Measurement in Electronic Materials JESD221 (JEDEC Standard-Alpha Radiation Measurement in Electronic Materials JESD221) stipulated by JEDEC (Joint Electron Device Engineering Council; Electronic Engineering Design and Development Joint Association), The reason why radon in the atmosphere entering the high-pressure gas tank does not produce alpha rays.

‧Discoloration resistance In order to measure the discoloration resistance of Cu balls, the Cu balls were heated at 200°C for 420 seconds using a constant temperature bath in the atmosphere, and the change in brightness was measured, and it was evaluated whether the Cu balls could sufficiently withstand changes over time. . The luminance is measured using a CM-3500d spectrophotometer manufactured by Konica Minolta under a D65 light source and a 10-degree field of view in accordance with JIS Z 8722 "Measurement of Color - Color of Reflected and Transmitted Objects" to measure the spectral transmittance and from the color value ( L*a*b*) to obtain. Also, (L*a*b*) is defined in JIS Z 8729 "Expression method of color-L*a*b* color system and L*u*v* color system". L* is lightness, a* is redness, and a* is yellowness.

[Evaluation criteria for discoloration resistance] In each of the following tables, the discoloration resistance evaluation criteria of Cu balls are as follows. ○: Brightness after 420 seconds is 55 or higher ╳: The brightness after 420 seconds is less than 55.

‧Overview Cu balls that are ○ or ○○ or ○○○ in any one of the above-mentioned evaluation methods and evaluation criteria of true sphericity, Vickers hardness, α-ray content, and discoloration resistance are evaluated as ○ in the comprehensive evaluation. On the other hand, Cu balls with any one of ╳ in true sphericity, Vickers hardness, α ray content, and discoloration resistance were evaluated as ╳ in the comprehensive evaluation.

In addition, Cu nuclei spheres whose true sphericity is ○ or ○○ or ○○○ in the above-mentioned evaluation method and evaluation standard were rated as ○ in the comprehensive evaluation together with the evaluation of Cu balls. On the other hand, the Cu nuclear sphere whose true sphericity is ╳ is evaluated as ╳ in the comprehensive evaluation.

In addition, since the Vickers hardness of the Cu nuclei depends on the Ni plating layer which is an example of the solder layer and the metal layer, the Vickers hardness of the Cu nuclei was not evaluated. However, in the Cu core ball, when the Vickers hardness of the Cu ball is within the specified range of the present invention, the drop impact resistance of the Cu core ball is also good, cracks can be suppressed, electrode collapse, etc. can also be suppressed, and electrical conductivity can also be suppressed. deteriorating.

On the other hand, when the Vickers hardness of the Cu ball of the Cu core ball is large and exceeds the range specified by the present invention, the durability against external stress becomes low and the drop impact resistance deteriorates, which cannot be solved. The subject of cracking.

Therefore, the Cu core balls using the Cu balls of Comparative Examples 8 to 11 whose Vickers hardness was greater than 55.5 HV were not suitable for the evaluation of the Vickers hardness, so the overall evaluation was rated as ╳.

In addition, since the discoloration resistance of the Cu nuclei depends on the Ni plating layer as an example of the solder layer and the metal layer, the discoloration resistance of the Cu nuclei was not evaluated. However, when the brightness of the Cu ball is within the range specified by the present invention, sulfide and oxysulfide on the surface of the Cu ball can be suppressed, and it is suitable to be coated with a metal layer such as a solder layer or a Ni plating layer.

On the other hand, when the brightness of the Cu ball is lower than the range specified by the present invention, the Cu ball cannot suppress the sulfide and sulfur oxide on the surface, and it is not suitable for coating with a metal layer such as a solder layer or a Ni plating layer.

Therefore, the Cu core balls using the Cu balls of Comparative Examples 1 to 6 whose luminance after 420 seconds were less than 55 were not suitable for the evaluation of discoloration resistance, so the overall evaluation was rated as ╳.

In addition, the amount of α radiation of the Cu nuclei depends on the composition of the plating solution raw material constituting the solder layer covering the Cu balls, and each element in the composition. When the Ni plating layer, which is an example of the metal layer covering the Cu balls, is provided, it also depends on the raw material of the plating solution constituting the Ni layer.

When the Cu balls have the low α-ray content specified in the present invention, and when the raw materials of the electroplating solution constituting the solder layer and the Ni plating layer have the low α-line content specified in the present invention, the Cu core balls also have the low α-line content specified in the present invention. On the other hand, when the raw material of the plating solution constituting the solder layer and the Ni plating layer has a high α-ray content that is greater than the α-line content specified in the present invention, even if the Cu balls have the above-mentioned low α-line content, the Cu nuclei become larger than the α-line content specified in the present invention. High α ray content of α ray volume.

Also, when the α ray content of the plating solution raw materials constituting the solder layer and the Ni plating layer shows a somewhat higher α ray content than the low α ray content specified in the present invention, impurities can be removed by the above-mentioned electroplating process. Reduce until the amount of α-rays falls within the range of low α-rays specified in the present invention.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

As shown in Table 1, any of the Cu spheres of the examples with a purity of 4N5 or more and 5N5 or less obtained good results in the comprehensive evaluation. Therefore, the purity of Cu balls can be said to be above 4N5 and below 5N5.

The details of the evaluation will be described below. As in Examples 1 to 12 and 18, Cu balls with a purity of 4N5 or more and 5N5 or less, and containing Fe, Ag, or Ni of 5.0 mass ppm or more and 50.0 mass ppm or less are based on the true sphericity. , Vickers hardness, α-ray content and comprehensive evaluation of discoloration resistance can get good results. As shown in Examples 13 to 17 and 19, Cu balls with a purity of 4N5 or more and 5N5 or less and a total of Fe, Ag, and Ni containing 5.0 mass ppm or more and 50.0 mass ppm or less have good sphericity, Vickers hardness, α ray content, and The comprehensive evaluation of discoloration resistance also yielded good results. Also, not shown in the table, from Examples 1, 18, and 19, the content of Fe was changed from 0 ppm to less than 5.0 ppm by mass, the content of Ag was changed from 0 ppm to less than 5.0 ppm by mass, and the content of Ni was changed to Cu balls whose content is changed from 0 mass ppm to less than 5.0 mass ppm and whose total content of Fe, Ag, and Ni is set to 5.0 mass ppm or more are also good in the comprehensive evaluation of true sphericity, Vickers hardness, α ray content, and discoloration resistance. able to get good results.

Also, as shown in Example 18, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, and Au containing Fe, Ag, or Ni and other impurity elements from 5.0 mass ppm to 50.0 mass ppm are each The Cu balls of Example 18 with 50.0 mass ppm or less can also obtain good results in the comprehensive evaluation of true sphericity, Vickers hardness, α-ray content, and discoloration resistance.

For the Cu core balls, as shown in Table 3 and Table 4, the Cu balls of Examples 1 to 19 were coated with the solder layer of the solder alloy of Example 1 containing 5.0% by mass of Sb and the remainder being Sn. The resulting Cu core balls of Examples 1A to 19A; and Example 1B formed by coating the Cu balls of Examples 1 to 19 with a Ni-plated layer and then covering them with a solder layer of the solder alloy of Example 1 The comprehensive evaluation of true sphericity of ~19B Cu nuclei can also get good results.

Formed by coating the Cu balls of Examples 1 to 19 with the solder layer of the solder alloy of Composition Example 2 containing 10.0% by mass Sb, 4.0% by mass of Ag, 0.5% by mass of Cu, and the remainder being Sn The Cu core balls of Examples 1A to 19A; and Examples 1B to 19B formed by coating the Cu balls of Examples 1 to 19 with a Ni-plated layer and then coating them with a solder layer of the solder alloy of Example 2 The comprehensive evaluation of true sphericity of Cu nuclei can also get good results.

Also, not shown in the table, from Examples 1, 18, and 19, the Fe content was changed from 0 mass ppm to less than 5.0 mass ppm, the Ag content was changed from 0 mass ppm to less than 5.0 mass ppm, and The content of Ni is changed to be 0 mass ppm or more and less than 5.0 mass ppm and the total of Fe, Ag, and Ni is 5.0 mass ppm or more of Cu balls, by using any one of the solder alloy of composition example 1 to composition example 2 The Cu core ball formed by coating the solder layer, and the Cu ball is coated with a Ni-plated layer, and the Cu core ball formed by coating the solder layer of the solder alloy of composition example 1 to composition example 2, Good results can also be obtained in the comprehensive evaluation of true sphericity.

On the other hand, the Cu spherical system of Comparative Example 7 not only failed to reach a total content of 5.0 mass ppm of Fe, Ag, and Ni, but also U and Th were less than 5 mass ppm, and other impurity elements were also less than 1 mass ppm. ball, the Cu ball of Comparative Example 7 coated with a solder layer using the solder alloy of each composition example, the Cu core ball of Comparative Example 7A, and the Cu ball of Comparative Example 7 coated with a Ni plating layer, and then by The true sphericity of the Cu core spheroid system of Comparative Example 7B coated with the solder layer of the solder alloy of each composition example did not reach 0.95. In addition, the Cu balls of Comparative Example 12 whose total content of at least one of Fe, Ag, and Ni did not reach 5.0 mass ppm even if impurity elements were contained, and the Cu balls of Comparative Example 12 were mixed by using solder alloys of the respective composition examples. The Cu core ball of Comparative Example 12A coated with a solder layer, and the Cu core ball of Comparative Example 12B coated with a solder layer using a solder alloy of each composition example by coating the Cu ball of Comparative Example 12 with a Ni plating layer The true sphericity of the ball did not reach 0.95. From these results, Cu balls in which the total content of at least one of Fe, Ag, and Ni is less than 5.0 mass ppm, and Cu core balls in which the Cu balls are coated with a solder layer using a solder alloy of each composition example , and Cu core balls formed by coating the Cu balls with a Ni-plated layer and further coating with the solder layer of the solder alloy of each composition example cannot achieve high true sphericity.

Also, in Comparative Example 10, the Cu spherical Fe, Ag, and Ni contents were 153.6 mass ppm in total and the contents of other impurity elements were each 50 mass ppm or less, but the Vickers hardness was greater than 55.5 HV and good results could not be obtained. Furthermore, in the Cu ball of Comparative Example 8, not only the total content of Fe, Ag, and Ni is 150.0 mass ppm, but also the content of other impurity elements, especially Sn, is 151.0 mass ppm, which is significantly greater than 50.0 mass ppm, and the Vickers hardness is Greater than 55.5HV does not give good results. Therefore, even for Cu balls with a purity of 4N5 or more and 5N5 or less, Cu balls with a total content of at least one of Fe, Ag, and Ni greater than 50.0 mass ppm have a high Vickers hardness and low hardness cannot be achieved. In this way, when the Vickers hardness of the Cu ball exceeds the range specified in the present invention, the durability against external stress decreases, the drop impact resistance deteriorates, and the problem that cracks are likely to occur cannot be solved. Furthermore, it can be said that it is preferable to contain other impurity elements within a range of not more than 50.0 mass ppm each.

From these results, it can be said that Cu balls with a purity of 4N5 or more and 5N5 or less and a total content of at least one of Fe, Ag, and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less can achieve high sphericity And low hardness and inhibit discoloration. Cu core balls formed by coating such Cu balls with a solder layer of a solder alloy of each composition example, coating such a Cu ball with a Ni-plated layer, and coating with a solder layer of a solder alloy of each composition example The Cu core ball system achieves high true sphericity, and by realizing the low hardness of the Cu ball, as the Cu core ball, the drop impact resistance is also good, cracks can be suppressed, and electrode collapse can also be suppressed, which in turn can also suppress electrical conduction. sexual deterioration. Furthermore, since discoloration of Cu balls can be suppressed, it is suitable for covering with metal layers such as a solder layer and a Ni plating layer. The content of other impurity elements is preferably 50.0 mass ppm or less.

Not shown in the table, Cu balls having the same composition as those of the examples and having a ball diameter of not less than 1 μm and not more than 1000 μm can be evaluated in terms of true sphericity, Vickers hardness, α ray content, and discoloration resistance. get good results. Therefore, it can be said that the diameter of the Cu ball is preferably not less than 1 μm and not more than 1000 μm, and is more preferably not less than 50 μm and not more than 300 μm.

The Cu ball of Example 19 has a total content of Fe, Ag, and Ni of not less than 5.0 mass ppm and not more than 50.0 mass ppm and contains 2.9 mass ppm of P. A comprehensive evaluation can yield good results. The Cu balls of Example 19 were coated with a solder layer using the solder alloy of each composition example. The Cu balls of Example 19 were coated with a Ni plating layer, and then by using The Cu nuclei spheres coated with solder layer obtained good results in the comprehensive evaluation of true sphericity. The total content of Fe, Ag, and Ni in the Cu ball system of Comparative Example 11 is 50.0 mass ppm or less as in the Cu ball of Example 19, but the Vickers hardness is greater than 5.5HV, which is different from the Cu ball of Example 19. result. In addition, the Vickers hardness of Comparative Example 9 is also greater than 5.5HV. This is considered to be because the P content of Comparative Examples 9 and 11 was significantly high, and from this result, it was found that when the P content increased, the Vickers hardness increased. Therefore, it can be said that the content of P is preferably less than 3 mass ppm, more preferably less than 1 mass ppm.

In the Cu balls of each example, the amount of α rays was 0.0200 cph/cm ² or less. Therefore, in the solder alloys of Composition Example 1 and Composition Example 2 that cover the Cu balls of Examples 1 to 19, the Cu core balls of Examples 1A to 19A also become the present invention because each element has a low α radiation content specified in the present invention. The amount of low alpha rays specified by the invention. Also, when the Ni plating layer as an example of the metal layer covered with Cu balls is provided, in addition to the solder alloy, each element constituting the Ni plating layer has a low α dose specified by the present invention, and each of Examples 1B to 19B The Cu nuclei also become the low α ray amount specified in the present invention.

Moreover, through the electroplating process for forming the solder layer and the Ni plating layer, the impurities that emit α rays contained in the alloy are removed. When showing some higher α-ray dose, the α-ray dose after electroplating can also be reduced to the low α-ray dose range specified by the present invention.

Therefore, when the Cu nuclei of each embodiment are used in high-density packaging of electronic components, soft errors can be suppressed by using the low α-ray content as the raw material of the plating solution constituting the solder layer and the Ni plating layer as specified in the present invention.

In the Cu ball of Comparative Example 7, good results in discoloration resistance were obtained, but in Comparative Examples 1 to 6, favorable results were not obtained in discoloration resistance. When comparing the Cu balls of Comparative Examples 1-6 with the Cu balls of Comparative Example 7, the difference in the composition is only the content of S. Therefore, in order to obtain good results in discoloration resistance, it can be said that the S content must be less than 1 mass ppm. The S content of any of the Cu spheres in each embodiment is less than 1 mass ppm, and it can be said that the S content is preferably less than 1 mass ppm.

Next, in order to confirm the relationship between the S content and the discoloration resistance, the Cu balls of Example 14, Comparative Example 1, and Comparative Example 5 were heated at 200°C, and photographed before heating, after heating for 60 seconds, after 180 seconds, and 420 Seconds later the photo is taken and the brightness is measured. Table 7 and Fig. 7 are charts showing the relationship between the time for heating each Cu ball and the brightness.

[Table 7]

From the table, when the brightness before heating is compared with the brightness after heating for 420 seconds, the brightness of Example 14, Comparative Examples 1 and 5 are values close to 64 and 65 before heating. After heating for 420 seconds, the brightness of Comparative Example 5 containing 30.0 mass ppm of S became the lowest, followed by Comparative Example 1 containing 10.0 mass ppm of S, and Example 14 in which the S content was less than 1 mass ppm. . Therefore, it can be said that the higher the S content, the lower the brightness after heating. The Cu balls of Comparative Examples 1 and 5 have brightness less than 55, so Cu balls containing 10.0 mass ppm or more of S tend to change color by forming sulfide and sulfur oxide when heated. Moreover, when the content of S is 0 mass ppm or more and 1.0 mass ppm or less, the formation of sulfide and sulfur oxide can be suppressed, and it can be said that the wettability is good. Also, when the Cu ball of Example 14 was packaged on the electrode, it showed good wettability.

As above, the purity is not less than 4N5 and not more than 5N5, the total content of at least one of Fe, Ag, and Ni is not less than 5.0 mass ppm and not more than 50.0 mass ppm, the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, P The Cu balls of the present example whose Cu content is 0 mass ppm or more and less than 3.0 mass ppm can realize high sphericity because all of them have a true sphericity of 0.95 or greater. By achieving a high degree of sphericity, it is possible to suppress variation in the height of the Cu ball while ensuring self-alignment when the Cu ball is packaged in an electrode or the like. The same effect can be obtained by using the Cu core ball formed by coating the Cu ball of this embodiment with a solder layer; and the Cu core ball formed by coating the Cu ball of this embodiment with a metal layer and further coating the metal layer with a solder layer.

In addition, since the Vickers hardness of any of the Cu ball systems of this example is 55 HV or less, low hardness can be realized. By achieving low hardness, the drop impact resistance of Cu balls can be improved. By realizing the low hardness of the Cu ball, use the Cu core ball formed by covering the Cu ball of this embodiment with a solder layer; and cover the Cu ball of this embodiment with a metal layer, and then use the Cu core formed by covering the metal layer with a solder layer The balls had good drop impact resistance and suppressed cracking, and also suppressed electrode collapse and the like, and also suppressed deterioration in electrical conductivity.

Furthermore, any of the Cu balls of this example can suppress discoloration. By suppressing discoloration of the Cu balls, it is possible to suppress adverse effects of sulfides and sulfur oxides on the Cu balls, and improve wettability when the Cu balls are encapsulated on the electrodes. Since discoloration of Cu balls can be suppressed, it is suitable for coating of metal layers such as solder layer and Ni plating layer.

In addition, the Cu material of this embodiment uses a Cu bulk metal material with a purity greater than 4N5 and less than 6N to manufacture Cu balls with a purity of more than 4N5 and less than 5N5. etc. Good results were also obtained in the comprehensive evaluation of both Cu balls and Cu core balls.

Next, the distribution of elements other than Sn in the solder layer of Cu nuclei balls formed by coating the surface of Cu balls with a solder layer using a Sn-based solder alloy will be described. As the solder layer covering the Cu balls, as shown in JP-A-2007-44718 (referred to as Patent Document 4) and JP-A No. 5367924 (referred to as Patent Document 5), solder containing Sn as a main component can be used. alloy.

In Patent Document 4, a Sn-based solder alloy composed of Sn and Bi is used to coat the surface of Cu balls to form a solder layer. The Sn-based solder alloy containing Bi has a relatively low melting temperature of 130-140°C and is called a low-temperature solder.

In Patent Document 4, the content of Bi contained in the solder layer is electroplated with a concentration gradient such that the content of Bi contained in the solder layer is lighter on the inner side (inner peripheral side) and becomes richer toward the outer side (outer peripheral side).

Patent Document 5 also discloses a solder bump in which Cu balls are plated with a Sn-based solder alloy composed of Sn and Bi. In Patent Document 5, the content of Bi contained in the solder layer is plated with a concentration gradient such that the content of Bi contained in the solder layer is richer on the inner side (inner peripheral side) and becomes lighter toward the outer side (outer peripheral side).

The technique of Patent Document 5 is a completely opposite concentration gradient to that of Patent Document 4. This is considered to be because the concentration control according to Patent Document 5 is simpler and easier to manufacture than that according to Patent Document 4.

As mentioned above, when the Cu nuclei formed by electroplating the surface of Cu balls coated with a Sn-based solder alloy containing binary or more elements added to Sn are placed on the electrodes of the semiconductor wafer and subjected to reflow treatment, the added elements Patent Documents 4 and 5, which have a concentration gradient in the solder layer, cause problems as follows.

The technique disclosed in Patent Document 4 has a solder layer with a concentration gradient in which the Bi concentration is lighter on the inner peripheral side and thicker on the outer peripheral side, and Bi is melted in such a concentration gradient (lighter on the inner side and thicker on the outer side). There is a slight possibility that the timing may deviate between the inner peripheral side and the outer peripheral side.

When the melting sequence is shifted, the outer surface of the Cu nuclei starts to melt, and the region on the inner peripheral surface side is partially melted and doped. shift. In the case of high-density packaging with narrow pitches, there is a possibility of a fatal defect in the soldering process due to the positional deviation.

The concentration gradient of Bi in Patent Document 5 is opposite to that in Patent Document 1. At this time, heat treatment by reflow is performed in order to connect the semiconductor elements. As in Patent Document 5, when heating and melting is carried out in a state where the Bi concentration in the solder layer is richer on the inner peripheral side and lighter on the outer peripheral side, since the Bi density on the inner peripheral side is high, the solder is absorbed from the Bi concentration on the inner peripheral side. The area begins to melt. Since the Bi region on the inner peripheral side melts, but the Bi region on the outer peripheral side has not yet started to melt, the volume expansion occurs relatively rapidly on the Bi region side on the inner peripheral side.

Due to the speed of this volume expansion on the inner and outer peripheral sides, a pressure difference is generated between the inner peripheral side and the outer peripheral side (outside air) of Bi, and when the outer peripheral side of Bi starts to melt, the pressure difference caused by the volume expansion on the inner peripheral side becomes a nucleus. The thick ball produces a state of affairs such as flying. Such a situation must be avoided.

In this way, the Cu nuclei ball having a solder layer composed of a Sn-based solder alloy composed of Sn and Bi causes defects when Bi in the solder layer has a concentration gradient.

In recent years, the demand for high-temperature solder has increased, and there is a proposal to disclose a solder alloy in which Sb is added to Sn. Even if a core material in which a solder alloy in which Sn is added to Sb or more is coated is used, if Sb has a predetermined concentration gradient in the solder layer, it is considered that the same problem as that of the above-mentioned Bi occurs.

Therefore, the effect that the distribution of Sb in the solder layer 3 is uniform will be described. In order to confirm that the concentration distribution of Sb in the solder layer 3 is a value commensurate with the target value, the following experiments were performed. (1) Cu core balls 11B having a composition of (Sn-5Sb) of the solder layer 3 were produced under the following conditions. In the following examples, Cu balls with the composition of Example 17 shown in Table 1 were used. ‧Diameter of Cu ball 1: 250μm ‧Film thickness of metal layer (Ni plating layer) 2: 2μm ‧Film thickness of solder layer 3: 23μm ‧Diameter of Cu nuclei 11B: 300μm

In order to facilitate measurement using experimental results, Cu nuclei balls having a thinner solder layer were produced as Cu nuclei balls 11B.

The electroplating method is based on the electroplating technology and is manufactured so as to meet the conditions of the above-mentioned Fig. 4 . (2) Ten Cu nuclei spheres 11B formed with a solder layer of a (Sn-5Sb)-based solder alloy having the same composition were prepared as samples. These were used as sample A. (3) Ten samples A were sealed with resin. (4) Each sealed sample A is ground together with the resin and the cross-section of each sample A is observed. The observation mechanism is FE-EPMAJXA-8530F manufactured by JEOL Ltd.

Fig. 8 is an explanatory diagram showing an example of a method of measuring the concentration distribution of Sb in Cu nuclei. The solder layer 3 is divided into an inner layer 16a, an intermediate layer 16b, and an outer layer 16c from the surface side of the Cu ball 1 for convenience. The inner layer 16a is from the surface of the Cu ball 1 to 9 μm, the middle layer 16b is 9-17 μm, and the outer layer 16c is 17-23 μm. From the inner layer 16a, the middle layer 16b and the outer layer 16c, as in the eighth In this example, the inner layer region 17a, the middle layer region 17b, and the outer layer region 17c were cut out with a thickness of 5 μm and a width of 40 μm, and each region was used as a measurement region to measure the concentration of Sb by qualitative analysis. This work is performed for a total of 10 fields of view for each of the inner layer 16a, the middle layer 16b, and the outer layer 16c.

Such measurement work was performed in the same manner for samples B to D manufactured separately from sample A. Samples B to D are the same as sample A, using, for example, 10 Cu nuclei spheres 11B formed with a solder layer of a (Sn-5Sb) based solder alloy of the same composition.

The concentration ratio of each layer obtained by measuring the Sb concentration of the inner layer, the middle layer, and the outer layer of the solder layer is shown in Table 8 below.

Table 8 shows the average value of Sb concentration in each layer of the solder layer measured by 10 Cu nuclei balls in samples A to D, and the Sb content when the target Sb content (target value) is 5% by mass. concentration ratio.

Samples A to D were as described above, and the Sb concentrations of the inner layer, the middle layer, and the outer layer were measured for each of the 10 Cu core spheres. For samples A to D, the measured values of the Sb concentrations in the inner layer, middle layer, and outer layer of the 10 Cu core spheres are not shown in Table 8.

The target Sb content (target value) of samples A to D was 5% by mass. At this time, the concentration ratio (%) of Sb in each of the 10 Cu core spheres of samples A to D was obtained from the measured value of the concentration of Sb by the following formula (1). Concentration ratio (%)=(measurement value/5)×100...(1)

In addition, the average value of the concentration of Sb can be obtained by the following formula (2) when the number of Cu nuclei spheres used as a sample is 10. The average value of the concentration of Sb = the total value of 10 measured values / 10...(2)

Furthermore, when the target Sb content (target value) is 5% by mass, the concentration ratios (%) of the samples A to D can be obtained from the average value of the measured values of the Sb concentrations by the following formula (3) ask for. Concentration ratio (%)=(average value of measured value/5)×100...(3)

[Table 8]

As shown in Table 8, for sample A, the average value of the concentration of Sb in the inner layer region 17a is 3.66% by mass and the concentration ratio is 73.2%, and the average value of the concentration of Sb in the middle layer region 17b is 4.73% by mass and the concentration ratio is 4.73% by mass. 94.6%, the average value of the Sb concentration in the outer layer region 17c was 3.82% by mass, and the concentration ratio was 76.4%.

Also, for sample B, the average value of the Sb concentration in the inner layer region 17a was 4.78% by mass and the concentration ratio was 95.6%, and the average value of the Sb concentration in the middle layer region 17b was 5.01% by mass and the concentration ratio was 100.2%. The average value of the concentration of Sb in the outer layer region 17c was 5.42% by mass, and the concentration ratio was 108.4%.

Furthermore, for sample C, the average value of the Sb concentration in the inner layer region 17a was 5.34% by mass and the concentration ratio was 106.8%, and the average value of the Sb concentration in the middle layer region 17b was 5.85% by mass and the concentration ratio was 117.0%. The average value of the concentration of Sb in the outer layer region 17c was 5.47% by mass, and the concentration ratio was 109.4%.

Also, for sample D, the average value of the Sb concentration in the inner layer region 17a was 4.78% by mass and the concentration ratio was 95.6%, and the average value of the Sb concentration in the middle layer region 17b was 5.52% by mass and the concentration ratio was 110.4%. The average value of the concentration of Sb in the outer layer region 17c was 4.96% by mass, and the concentration ratio was 99.2%.

In this way, for each of the inner layer region 17a, the intermediate layer region 17b, and the outer layer region 17c, since the Sb concentration in the solder layer is within the above-mentioned allowable range of 3.66% by mass to 5.85% by mass, it is known that the Sb concentration is approximately the target value. ratio.

Then, for example, 10 Cu core spheres produced in the same batch as these samples A to D were extracted, and each was bonded to a substrate by a normal reflow process. The joining results are also shown in Table 8.

Regarding the joining results, those in which no bad joints were measured in all the samples were judged as "good", and those in which even one sample had a positional shift during bonding, and even one sample in which Cu The flying object of the nuclear ball 11B was judged as "bad".

In either case, the inner peripheral side melts faster than the outer peripheral side and the volume expansion difference between the inner peripheral side and the outer peripheral side causes the Cu nuclei 11B to fly away, and the solder layer 3 is substantially uniform as a whole. Since there is no positional displacement of the core material, which is considered to be caused by a shift in the melting sequence, there is no possibility of a short circuit between electrodes due to positional deviation. Therefore, it was judged as "good" because no bonding failure occurred at all and good results were obtained.

As mentioned above, in the case of (Sn-5Sb) based solder alloys, the results in Table 8 show that the range of 3.66 mass % (concentration ratio 73.2%) to 5.85 mass % (concentration ratio 117.0%) is an allowable range.

Next, the same measurement was performed when forming the solder layer 3 of the quaternary Sn-based solder alloy composed of (Sn-10Sb-4Ag-0.5Cu) containing Ag, Cu, and Sb. At this time, the distribution of Sb was 10% by mass as the target value, and the allowable range was 7.19% by mass (71.9% concentration ratio) to 12.14% by mass (121.4% concentration ratio). The manufacturing method of the Cu nuclei is the same as that of the above-mentioned Cu nuclei using the solder alloy of (Sn-5Sb) as the examples A to D.

Regarding the specifications and experimental conditions such as the diameter of Cu balls and Cu core balls used, the thickness of the metal layer (Ni plating layer) and solder layer, etc., the conditions are the same as those of samples A~D except for the composition of the solder layer. .

The results are shown in the form of samples E to H in Table 8. At this time, because the Sb of the target value is 10% by mass, as shown in samples E~H, it is 7.19~12.14% by mass (either of which is the average value of 10 measurements for the same sample), although there is some deviation (average The minimum 7.19 mass % (concentration ratio 71.9%) ~ maximum 12.14 mass % (concentration ratio 121.4%)), but within the allowable range. Therefore, it is found that it falls within 7.19 mass % (concentration ratio 71.90%) to 12.14 mass % (concentration ratio 121.40%). The joining judgment system was the same as the examples of samples A to D, and since good results were obtained in which no joint failure occurred at all, it was judged as "good".

In samples E to H, the target Sb content (target value) was 10 (mass %). Therefore, the concentration ratios (%) of samples E to H in Table 8 can be obtained by the following formula (4).

Concentration ratio (%)=(average value of measured value/10)×100...(4)

Table 9 summarizes the results of the examples of the samples A to D and the examples of the samples E to H mentioned above. The concentration ratio of Sb is 71.9% to 121.4% by mass. Here, when measuring the true sphericity of the Cu nuclei produced in Examples A to D and Examples E to H, any one of them satisfies 0.99 or more and satisfies 0.95 or more.

The concentration ratio (%) in Table 9 can be obtained by the following formula (5).

Concentration ratio (%)=(measurement value/target value)×100...(5)

In addition, the experimental results in the case where Sb in the solder layer as a comparative example was distributed to have a concentration gradient are shown in Table 8 above. Regarding the diameter of the Cu balls and Cu core balls used, the film thicknesses of the metal layer (Ni-plated layer) and the solder layer, etc., and the experimental conditions, in addition to the following electroplating methods, they are examples of samples A to D. The same conditions were used for the examples of samples E to H.

In Comparative Example A, electroplating was performed using an electroplating solution containing a Sn compound, an organic acid, and a surfactant. And when the plating film thickness reaches 80% of the target value, only the Sb(III) compound is further added. Thereby, the electroplating treatment is performed while increasing the concentration of the Sb(III) compound while reducing the concentration of the Sn compound in the plating solution.

As a result, even if the solder layer is formed so that the content of Sb becomes the target value of 5% by mass for the entire solder layer, the concentration of Sb in the solder layer becomes lighter on the inside and becomes denser as it goes to the outside. Gradient (inner layer 0% by mass, middle layer 0% by mass, outer layer 29.58% by mass).

In Comparative Example B, electroplating was performed using an electroplating solution containing a Sn compound, a Sb(III) compound, an organic acid, and a surfactant. From the start of electroplating, while applying a predetermined DC voltage between the anode electrode and the cathode electrode, the electroplating process was performed while shaking the Cu balls.

As a result, even if the solder layer is formed so that the Sb content becomes the target value of 5% by mass for the entire solder layer, the Sb concentration in the solder layer has a concentration gradient in which the inner side is higher and the outer side becomes lower. (inner layer 43.74% by mass, middle layer 0% by mass, outer layer 0% by mass). In addition, in Comparative Examples A and B, the target Sb content is 5 (mass %), and the concentration ratio (%) can be obtained by the formula (3).

As a result, Comparative Example A was judged to be "defective" because positional displacement occurred during bonding, and Comparative Example B was judged to be "defective" because Cu nuclei spheres flew. Here, when the true sphericity was measured for the Cu nuclei produced in Comparative Example A and Comparative Example B, any of them was less than 0.95%.

In this way, when the Sb concentration in the solder layer 3 is changed, phenomena such as positional shift and Cu nuclei ball 11B being blown off occur.

As described above, in each of Examples A to H, since Sb in the solder layer is homogeneous, the Sb concentration ratio of Sb in the entire area including the inner peripheral side and the outer peripheral side with respect to the film thickness of the solder layer is within a predetermined range. Inside. Therefore, the Cu nuclei sphere system of the present invention in which the Sb in the solder layer is homogeneous does not produce such a situation that the inner peripheral side melts faster than the outer peripheral side and the volume expansion difference between the inner peripheral side and the outer peripheral side causes the Cu nuclei spheres to burst. The flying situation.

Also, since the Sb in the solder layer is homogeneous and the Cu nuclei are melted almost uniformly over the entire area, there is almost no time difference in the melting sequence in the solder layer. As a result, since there is no displacement of the Cu nuclei due to the displacement of the melting sequence, there is no possibility of causing a short circuit between the electrodes due to the displacement or the like. Therefore, a high-quality solder joint can be provided by using the Cu nuclei.

1‧‧‧Cube ball 11A, 11B‧‧‧Cu core 2‧‧‧Metal layer 3‧‧‧Solder layer 10‧‧‧semiconductor chip 16a‧‧‧inner area 16b‧‧‧Middle layer area 16c‧‧‧Outer zone 17a‧‧‧inner area 17b‧‧‧Middle layer area 17c‧‧‧outer zone 100, 41‧‧‧electrodes 30‧‧‧Solder bumps 40‧‧‧Printed Substrate 50‧‧‧welding head 60‧‧‧Electronic Parts

Fig. 1 is a diagram showing Cu nuclei according to the first embodiment of the present invention.

Fig. 2 is a diagram showing a Cu core sphere according to a second embodiment of the present invention.

Fig. 3 is a diagram showing a configuration example of an electronic component using Cu core balls according to each embodiment of the present invention.

Fig. 4 is a characteristic graph showing the relationship between the thickness of the solder layer and the concentration of Sb in the solder layer (curve L) based on the diameter of the Cu nuclei.

Fig. 5 is an enlarged sectional view of a Cu nuclei sphere.

Fig. 6 is an enlarged view of the surface of a Cu nuclei sphere.

Fig. 7 is a graph showing the relationship between the heating time and the brightness after heating the Cu balls of Examples and Comparative Examples at 200°C.

Fig. 8 is an explanatory diagram showing an example of a method of measuring the concentration distribution of Sb in Cu nuclei.

1‧‧‧Cube ball

3‧‧‧Solder layer

11A‧‧‧Cu core

Claims (16)

A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm or less , the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, the content of P is not less than 0 mass ppm and less than 3.0 mass ppm, and the rest is Cu and other impurity elements. mass % or less, the true sphericity of the aforementioned Cu balls is 0.95 or greater, the aforementioned solder layer is composed of a (Sn-Sb) based solder alloy containing Sn and 0.1 to 30.0 mass % of Sb, and the Sn content is greater than 40 mass % , the concentration ratio (%) of Sb contained in the aforementioned solder layer is set as concentration ratio (%)=(measured value (mass %)/target content (mass %))×100, or concentration ratio (%)= When expressed as (average value (mass %) of measurement value/target content (mass %))×100, the aforementioned concentration ratio is within the range of 70 to 125%. A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm or less , the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, the content of P is not less than 0 mass ppm and less than 3.0 mass ppm, and the rest is Cu and other impurity elements. Mass % or less, the true sphericity of the aforementioned Cu balls is 0.95 or higher, and the aforementioned solder layer is made of (Sn-5Sb) solder containing Sn and Sb Composed of a solder alloy and the content of Sn is 40% by mass or more, the concentration ratio (%) of Sb contained in the aforementioned solder layer is defined as the concentration ratio (%)=(measured value (mass%)/target content (mass%) %))×100, or concentration ratio (%)=(average value of measured value (mass %)/target content (mass %))×100, the aforementioned concentration ratio is within the range of 73.2 to 117.0%. A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm or less , the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, the content of P is not less than 0 mass ppm and less than 3.0 mass ppm, and the rest is Cu and other impurity elements. Mass % or less, the true sphericity of the aforementioned Cu balls is 0.95 or more, the aforementioned solder layer is composed of a (Sn-10Sb) based solder alloy containing Sn and Sb and the Sn content is 40 mass % or more, and the aforementioned solder layer The concentration ratio (%) of Sb contained in is set as concentration ratio (%)=(measured value (mass %)/target content (mass %))×100, or concentration ratio (%)=(average value of measured value When expressed as (mass %)/target content (mass %))×100, the aforementioned concentration ratio is within the range of 71.9 to 121.4%. A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm or less , the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, The content of P is not less than 0 mass ppm and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, the purity of the aforementioned Cu balls is not less than 99.995 mass % and not more than 99.9995 mass %, and the true sphericity of the aforementioned Cu balls is not less than 0.95, The aforementioned solder layer is composed of a (Sn-Sb) based solder alloy containing Sn and 0.1 to 30.0% by mass of Sb, and the content of Sn is 40% by mass or more. The solder layer covers the surface of the aforementioned metal layer and the sphericity of the aforementioned Cu nuclei is 0.95 or more, and the aforementioned metal layer is composed of a single Ni, Co, Fe, or Pd, or a combination of Ni, Co, Fe, or Pd Composed of an alloy composed of two or more elements, the concentration ratio (%) of Sb contained in the aforementioned solder layer is defined as the concentration ratio (%)=(measured value (mass %)/target content (mass %))× 100, or concentration ratio (%)=(average value of measured value (mass %)/target content (mass %))×100, the aforementioned concentration ratio is within the range of 70 to 125%. A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm or less , the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, the content of P is not less than 0 mass ppm and less than 3.0 mass ppm, and the rest is Cu and other impurity elements. mass % or less, the sphericity of the aforementioned Cu balls is 0.95 or more, the aforementioned solder layer is composed of a (Sn-5Sb) based solder alloy containing Sn and Sb and the content of Sn is 40 mass % or more, and the aforementioned Cu balls The surface is covered with a metal layer, and the surface of the aforementioned metal layer is coated with the aforementioned solder layer and the true sphericity of the aforementioned Cu nuclei is above 0.95. The aforementioned metal layer is made of a single Ni, Co, Fe or Composed of Pd, or an alloy composed of two or more elements from Ni, Co, Fe, or Pd, let the concentration ratio (%) of Sb contained in the aforementioned solder layer be the concentration ratio (%) =(measured value (mass %)/target content (mass %))×100, or concentration ratio (%)=(average value of measured value (mass %)/target content (mass %))×100, The aforementioned concentration ratio is within the range of 73.2 to 117.0%. A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, wherein the total content of at least one of Fe, Ag, and Ni in the Cu ball is 5.0 mass ppm or more and 50.0 mass ppm or less , the content of S is not less than 0 mass ppm and not more than 1.0 mass ppm, the content of P is not less than 0 mass ppm and less than 3.0 mass ppm, and the rest is Cu and other impurity elements. mass % or less, the true sphericity of the aforementioned Cu balls is 0.95 or more, the aforementioned solder layer is composed of a (Sn-10Sb) based solder alloy containing Sn and Sb and the content of Sn is 40 mass % or more, and the aforementioned Cu balls The surface is covered with a metal layer, and the surface of the aforementioned metal layer is covered with the aforementioned solder layer and the true sphericity of the aforementioned Cu nuclei is greater than 0.95. The aforementioned metal layer is composed of a single Ni, Co, Fe or Pd, or is made of , Co, Fe, or Pd is composed of an alloy composed of a combination of two or more elements, and the concentration ratio (%) of Sb contained in the aforementioned solder layer is defined as the concentration ratio (%)=(measured value (mass%) / target content (mass %)) × 100, or concentration ratio (%) = (average value of measured value (mass %) / target content (mass %)) × 100, the above-mentioned concentration ratio is 71.9~121.4% In the range. The Cu core sphere described in any one of claims 1 to 6 of the patent claims, wherein the true sphericity of the Cu core sphere is above 0.99. The Cu core sphere according to any one of claims 1 to 6 of the patent claims, wherein the amount of α ray of the Cu core sphere is 0.0010 cph/cm ² or less. The Cu nuclei as described in any one of claims 1 to 6 of the patent claims, wherein the true sphericity of the Cu nuclei is 0.99 or more, and the α ray content of the Cu nuclei is 0.0010 cph/cm ² or less. The Cu core sphere according to any one of claims 1 to 6, wherein the diameter of the Cu sphere is not less than 1 μm and not more than 1000 μm. The Cu core sphere according to any one of claims 1 to 6 of the patent claims, wherein the true sphericity of the Cu core sphere is 0.99 or more, and the diameter of the Cu sphere is 1 μm or more and 1000 μm or less. The Cu core sphere according to any one of claims 1 to 6 of the patent claims, wherein the α ray content of the Cu core sphere is 0.0010 cph/cm ² or less, and the diameter of the Cu sphere is 1 μm or more and 1000 μm or less. The Cu nuclei as described in any one of items 1 to 6 of the scope of application, wherein the true sphericity of the Cu nuclei is 0.99 or more, the alpha ray content of the Cu nuclei is 0.0010 cph/cm ² or less, and the aforementioned The Cu balls have a diameter of not less than 1 μm and not more than 1000 μm. A welding joint using the Cu core ball described in any one of items 1 to 13 of the scope of the patent application. A kind of solder paste uses the Cu nuclei as described in any one of items 1 to 13 of the scope of the patent application. A kind of foam solder, is to use the Cu nuclei sphere described in any one of items 1 to 13 of the scope of application.

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