TWI770385B - Cu core balls, solder joints, solder paste and foam solder - Google Patents

Abstract

An object of the present invention is to provide a Cu core ball in which a Cu ball is coated with a metal layer, 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 Cu ball 1 contains at least one of Fe, Ag, and Ni. The total is 5.0 mass ppm or more and 50.0 mass ppm or less, the S content is 0 mass ppm or more and 1.0 mass ppm or less, the P content is 0 mass ppm or more and less than 3.0 mass ppm, and the remainder is Cu and other impurity elements, The purity of the Cu ball 1 is 99.995 mass % or more and 99.9995 mass % or less, the sphericity is 0.95 or more, and the solder layer is an alloy containing Sn and a Sn content of 40 mass % or more, an alloy containing Sn and Ge, or an alloy containing Sn and An alloy in which the content of Ge and Sn is 40 mass % or more.

Description

Cu core balls, solder joints, solder paste and foam solder

The present invention relates to a Cu core ball formed by coating the Cu ball with a metal layer, and a solder joint, solder paste and foamed solder using the Cu core ball.

In recent years, due to the development of small information devices, the electronic components mounted thereon have been rapidly miniaturized. Due to the requirement of miniaturization, electronic components are applied to ball grid arrays (hereinafter referred to as "BGAs") with electrodes on the backside in order to meet the narrowing of connection terminals and the reduction of packaging area.

Electronic parts using BGA are such as semiconductor components. In the semiconductor device, a resin is used to seal a semiconductor wafer 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 wafer. A semiconductor device to which BGA is applied is mounted on a printed circuit board by bonding a solder bump melted by heating to a conductive land of the printed circuit board. In addition, in order to meet the requirements of further high-density packaging, three-dimensional high-density packaging in which semiconductor elements are stacked in the height direction is being studied.

In high-density packaging of electronic components, there is a case where a soft error (soft error) in which memory content is rewritten is caused by alpha lines entering into memory cells of a semiconductor integrated circuit (IC). Therefore, in recent years, the development of low-α-line soldering materials and Cu balls in which the content of radioisotopes is reduced has been carried out. Patent Document 1 discloses a Cu ball containing Pb and Bi and having a purity of 99.9% or more and 99.995% or less of a low α amount. Patent Document 2 discloses a Cu ball having a purity of 99.9% or more and 99.995% or less, a sphericity of 0.95 or more, and a Vickers hardness of 20HV or more and 60HV or less.

However, when the crystal grains of the Cu balls are relatively fine, since the Vickers hardness increases, the durability against external stress decreases and the drop shock resistance decreases. Therefore, the Cu ball system used in the packaging of electronic components is required to have a predetermined flexibility, that is, a Vickers hardness below 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. When the amount of the impurity elements is small, the crystal grains grow greatly, and as a result, the Vickers hardness of the Cu balls is reduced. However, when the purity of the Cu balls is increased, the sphericity of the Cu balls becomes lower.

When the sphericity of the Cu balls is low, there is a possibility that self-alignment cannot be ensured when the Cu balls are packaged on the electrodes, and the height of the Cu balls becomes uneven during packaging of the semiconductor wafer, resulting in poor bonding situation.

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

In addition, the semiconductor device that has undergone three-dimensional high-density packaging is a BGA. When the solder balls are placed on the electrodes of the semiconductor wafer for reflow processing, the solder balls may collapse due to the weight of the semiconductor device. 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 a short-circuit accident, there has been a proposal to disclose a solder bump that does not collapse due to its own weight or deform when the 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 Literature]

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

However, it has been newly discovered that Cu balls containing more than a predetermined amount of S have a problem that sulfides and sulfur oxides are formed when heated, and are easily discolored. The discoloration of the Cu balls causes the wettability deterioration, and the wettability deterioration causes non-wetting and self-alignment deterioration. In this way, the adhesion of the Cu ball surface and the metal layer of the Cu ball which is easily discolored is decreased, and the oxidation and reactivity of the metal layer surface are increased, so it is not suitable to use the coating of the metal layer. On the other hand, when the sphericity of the Cu balls is low, the sphericity of the Cu core balls obtained by covering the Cu balls with a metal layer also becomes low.

Therefore, an object of the present invention is to provide a Cu core ball using Cu balls that achieves high sphericity and low hardness and can suppress discoloration, and a solder joint, solder paste, and foamed solder using the Cu core ball.

The present invention is as follows. (1) A Cu core ball comprising Cu balls and a solder layer covering the surfaces of the Cu balls, wherein the Cu balls have a total content of at least one of Fe, Ag and Ni of 5.0 mass ppm or more and 50.0 mass ppm ppm or less, S content is 0 mass ppm or more and 1.0 mass ppm or less, P content is 0 mass ppm or more and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, and the purity of the Cu balls is 99.995 mass % or more and 99.9995 mass % or less, the sphericity is 0.95 or more, and the solder layer is an alloy containing Sn and a Sn content of 40 mass % or more, an alloy containing Sn and Ge (germanium), or Sn and Ge and the Sn content of 40 Alloys with more than mass %. (2) The Cu core ball according to the above (1), wherein the content of Ge in the solder layer is more than 0 mass ppm and 220 mass ppm or less.

(3) The Cu core ball according to the above (1), wherein the content of Ge in the solder layer is 50 mass ppm or more and 220 mass ppm or less.

(4) The Cu core ball according to any one of the above items (1) to (3), wherein the sphericity is 0.98 or more.

(5) The Cu core ball according to any one of the above items (1) to (3), wherein the sphericity is 0.99 or more.

(6) The Cu core ball according to any one of the above items (1) to (5), wherein the amount of α rays is 0.0200 cph/cm ² or less.

(7) The Cu core ball according to any one of the above items (1) to (5), wherein the amount of α rays is 0.0010 cph/cm ² or less.

(8) The Cu core ball according to any one of the above items (1) to (7), 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 has a sphericity of 0.95 or more .

(9) The Cu core ball according to (8) above, wherein the sphericity is 0.98 or more.

(10) The Cu core ball according to (8) above, wherein the sphericity is 0.99 or more.

(11) The Cu core ball according to any one of the above items (8) to (10), wherein the amount of α rays is 0.0200 cph/cm ² or less.

(12) The Cu core ball according to any one of the above items (8) to (10), wherein the amount of α rays is 0.0010 cph/cm ² or less.

(13) The Cu core ball according to any one of the above items (1) to (12), wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less.

(14) A solder joint using the Cu core ball according to any one of the above items (1) to (13).

(15) A solder paste using the Cu core ball according to any one of the above items (1) to (13).

(16) A foamed solder using the Cu core ball described in any one of the above items (1) to (13).

According to the present invention, high sphericity and low hardness of Cu balls are achieved and discoloration of Cu balls is suppressed. By realizing the high sphericity of the Cu balls, the high sphericity of the Cu core balls formed by coating the Cu balls with a metal layer can be achieved, and the self-alignment can be ensured when the Cu ball cores are encapsulated on the electrodes. Variation in the height of the Cu core can be suppressed. In addition, by realizing the low hardness of the Cu balls, the drop shock resistance can also be improved in the Cu core balls formed by covering the Cu balls with a metal layer. In addition, since the discoloration of the Cu balls can be suppressed, the adverse effects of sulfides and sulfur oxides on the Cu balls can be suppressed, and the coating with a metal layer is suitable and the wettability becomes good. Moreover, the oxidation resistance of the solder layer is improved by containing Ge in the solder layer.

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 core are expressed as a ratio relative to the mass of the metal layer (mass ppm) unless otherwise specified. , mass ppb, and mass %). In addition, the units (ppm, ppb, and %) of the composition of the Cu balls represent ratios (ppm by mass, ppb by mass, and % by mass) relative to the mass of the Cu balls unless otherwise specified.

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

FIG. 2 shows an example of the configuration of the Cu core ball 11B according to the second embodiment of the present invention. As shown in FIG. 2 , the Cu core ball 11B according to the second embodiment of the present invention includes a Cu ball 1 , and is composed of one or more elements selected from Ni, Co, Fe, and Pd covering the surface of the Cu ball 1 . 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 the Cu core ball 11A or the Cu core ball 11B according to the embodiment of the present invention. As shown in FIG. 3 , the Cu core ball 11A or the Cu core ball 11B is 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 is wet and expanded. . 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 wafer 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 applied to the electrodes 41 . In this example, the structure in which the solder bumps 30 are packaged on the electrodes 41 of the printed circuit board 40 is referred to as a solder joint 50 .

In the Cu core balls 11A and 11B of the respective embodiments, the total content of at least one of Fe, Ag, and Ni in the Cu balls 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. Mass ppm or less, P content is 0 mass ppm or more and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, and the purity of Cu ball 1 is 4N5 (99.995 mass %) or more and 5N5 (99.9995 mass %) or less, true The sphericity is 0.95 or more.

The Cu core ball 11A of the first embodiment of the present invention can improve the sphericity of the Cu core ball 11A by improving the sphericity of the Cu ball 1 covered with the solder layer 3 . In addition, in the Cu core ball 11B of the second embodiment of the present invention, the sphericity of the Cu core ball 11B can be improved by improving the sphericity of the Cu ball 1 covered with the metal layer 2 and the solder layer 3 . Hereinafter, preferable aspects of the Cu balls 1 constituting the Cu core balls 11A and 11B will be described.

･Cu ball sphericity: 0.95 or more In the present invention, the so-called sphericity system means a deviation from a true sphere. The sphericity represents the arithmetic mean value calculated by dividing the diameter of 500 Cu balls by the major diameter, and this value represents the closer to 1.00 of the upper limit, the closer to the true sphere. The sphericity system is obtained by various methods such as the least quadratic 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 the lengths measured using the Ultra Quick Vision and ULTRA QV350-PRO measuring devices manufactured by Mitutoyo Corporation.

From the viewpoint of maintaining an appropriate space between the substrates, the Cu ball 1 has a sphericity of 0.95 or more, preferably a sphericity of 0.98 or more, and more preferably a sphericity of 0.99 or more. When the degree is less than 0.95, since the Cu ball 1 has an indeterminate shape, bumps with uneven heights are formed during bump formation, and the possibility of poor bonding increases. When the sphericity is 0.95 or more, since the Cu balls 1 are not melted at the temperature of welding, it is possible to suppress variations in the height of the welded joint 50 . Thereby, the bonding failure of the semiconductor wafer 10 and the printed circuit board 40 can be prevented reliably.

･Purity of Cu balls: 99.995 mass % or more and 99.9995 mass % or less Generally, compared with higher-purity Cu, since lower-purity Cu can ensure the impurity element that becomes the crystal nucleus of the Cu ball 1 in Cu, the sphericity is higher. On the other hand, the electrical conductivity and thermal conductivity of the Cu balls 1 with low purity are deteriorated.

Therefore, when the purity of Cu ball 1 series is 99.995 mass % (4N5) or more and 99.9995 mass % (5N5) or less, sufficient sphericity can be ensured. In addition, when the purity of the Cu balls 1 is 4N5 or more and 5N5 or less, not only the amount of α rays can be sufficiently reduced, but also the electrical conductivity and thermal conductivity of the Cu balls 1 can be prevented from deteriorating due to the decrease in purity.

When the Cu ball 1 is produced, the Cu material, which is an example of a metal material formed into small pieces of a predetermined shape, is melted by heating, and the molten Cu is formed into a spherical shape 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 sphericity due to the fine crystal grains whose growth is suppressed. On the other hand, when there are few impurity elements, there are relatively few substances that become crystal nuclei, so that the grain growth is not inhibited and grows with a certain direction. As a result, a part of the spherical molten Cu-based surface protrudes and solidifies, and the sphericity becomes low. As the impurity element, Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au, U, Th and the like can be considered.

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

･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 balls 1 , the total content of at least one of Fe, Ag, and Ni is 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 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, two or more are contained. The total content is preferably 5.0 mass ppm or more and 50.0 mass ppm or less. Since Fe, Ag, and Ni become crystal nuclei during melting in the production process of the Cu balls 1, when a certain amount of Fe, Ag, or Ni is contained in Cu, the Cu balls 1 with high sphericity can be produced. Therefore, among Fe, Ag, and Ni, at least one of them 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 the discoloration of the Cu balls 1 can be suppressed, but also after the Cu balls 1 are slowly heated, the With slow cooling, the desired Vickers hardness can be achieved without performing the annealing step of slowly recrystallizing the Cu balls 1 .

･The content of S is 0 mass ppm or more and 1.0 mass ppm or less The Cu balls 1 containing more than a predetermined amount of S are easily discolored by forming sulfides and sulfur oxides when heated, and have low wettability, so the content of S must be 0 mass ppm or more and 1.0 mass ppm or less. The Cu ball 1 formed with more sulfides and sulfur oxides becomes darker in the brightness of the surface of the Cu ball. Therefore, as will be described in detail later, when the result of measuring the brightness of the surface of the Cu ball is equal to or less than a predetermined value, the formation of sulfides and sulfur oxides can be suppressed, and the 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 may change into phosphoric acid or a Cu complex, which may adversely affect the Cu balls 1 . In addition, since the hardness of the Cu ball 1 containing P in a predetermined amount increases, the content of P is preferably 0 mass ppm or more 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, and Au other than the above-mentioned impurity elements contained in the Cu ball 1 (hereinafter referred to as "other impurity elements") is respectively Preferably it is 0 mass ppm or more and less than 50.0 mass ppm.

In addition, the Cu ball 1 contains at least one of Fe, Ag, and Ni as an essential element as described above. However, according to the current technology, the Cu ball 1 cannot prevent elements other than Fe, Ag, and Ni from being mixed, and therefore 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 effect and influence of adding each element are not easily manifested. In addition, when the content of the impurity element is less than 1 mass ppm when analyzing the elements contained in the Cu balls, 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 the Cu ball 1 is substantially 4N5 (99.995 mass %). In addition, when the total content of at least one of Fe, Ag and Ni is 5 mass ppm, and when the content of other impurity elements is less than 1 mass ppm, the purity of the Cu ball 1 is substantially 5N5 (99.9995 mass %).

･Vickers hardness of Cu ball: 55.5HV or less The Vickers hardness of the Cu ball 1 is preferably 55.5HV or less. When the Vickers hardness is large, the durability against external stress is low, and the drop shock resistance is deteriorated, and cracks are likely to be generated. In addition, when an auxiliary force such as pressurization is applied during the formation of bumps and joints in a three-dimensional package, there is a possibility that electrodes collapse or the like is caused when a relatively hard Cu ball is used. Furthermore, when the Vickers hardness of the Cu balls 1 is large, the crystal grain size becomes smaller than a certain level, which may cause deterioration of electrical conductivity. When the Vickers hardness of the Cu ball 1 is 55.5 HV or less, the drop shock resistance is also good, cracks can be suppressed, electrode collapse and the like can also 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 greater than 20HV.

･Cu ball α-ray amount: 0.0200cph/ ^cm2 or less In order to set the α-ray amount to the extent that soft errors do not become a problem in high-density packaging of electronic components, the α-ray amount of Cu ball 1 is 0.0200cph/cm ² or less good. From the viewpoint of suppressing soft errors in further high-density packaging, the α line amount 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 0.0010cph/cm ² or less. In order to suppress soft errors caused by the amount of α rays, the content of radioisotopes such as U and Th is preferably less than 5 mass ppb.

. Discoloration resistance: Brightness is 55 or more

The brightness of the Cu ball 1 is preferably above 55. The so-called lightness is the L* value of the L*a*b* color system. Since the brightness of the Cu ball 1 having S-derived sulfide and oxysulfide formed on the surface is lowered, and the brightness is 55 or more, it can be said that sulfide and oxysulfide can be suppressed. In addition, the Cu ball 1 having a luminance of 55 or more has good wettability at the time of encapsulation. 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 the Cu balls 1, but also have poor wettability when, for example, the Cu balls 1 are directly bonded to an electrode. Deterioration of wettability causes the occurrence of non-wetting and deterioration of self-alignment.

． Diameter of Cu ball: 1 μm or more and 1000 μm or less

The diameter of the Cu balls 1 is preferably 1 μm or more and 1000 μm or less, and preferably 50 μm or more and 300 μm or less. In this range, the spherical Cu ball 1 can be stably produced, and the connection short circuit when the pitch between the terminals is narrow can be suppressed. Here, for example, when the Cu ball 1 is used in the paste, "Cu ball" may also be referred to as "Cu powder". When the "Cu ball" is used in the "Cu powder", the diameter of the Cu ball is usually 1~300μm.

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

． solder layer

The composition of the solder layer 3 according to the embodiment of the present invention is composed of Sn alone, an alloy containing Sn and other additive elements and not containing Ge, an alloy containing Sn and Ge, or an alloy containing Sn and Ge and other additive elements constitute. In addition, Sn, Ge, and other additive elements can all contain unavoidable impurities.

In the solder alloy containing Sn, the content of Sn is preferably 40.0 mass % or more with respect to the whole alloy. In the solder alloy containing Ge, the content of Ge is preferably more than 0 mass ppm and 220 mass ppm or less, preferably 50 mass ppm or more and 220 mass ppm or less, relative to the entire alloy.

When the alloy composition of the solder layer 3 contains more than 0 mass ppm and 220 mass ppm or less of Ge, the oxidation resistance is improved and the increase in the oxide film thickness can be suppressed. Even if the addition amount of Ge is more than 220 mass ppm, the oxidation resistance can be ensured, but the wettability tends to be deteriorated. Therefore, the addition amount of Ge is more than 0 mass ppm and 220 mass ppm or less, preferably 50 mass ppm or more and 200 mass ppm or less.

As the additive element, one or two or more of Ag, Ni, Ga, In, Zn, Fe, Pb, Bi, Sb, Au, Pd, Co, and the like can be considered.

The thickness of the solder layer 3 also varies according to the particle size of the Cu balls 1 , and in order to ensure a sufficient amount of soldering, it is preferable that one side in the radial direction is 100 μm or less. The solder layer 3 can be formed by a conventional molten plating process.

The Cu core balls 11A and 11B may be formed by using a solder alloy with a low α radiation amount in the solder layer 3 to constitute the low α radiation Cu core balls 11A and 11B.

Next, the metal layer 2 covering the Cu balls 1 in the Cu core balls 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 or multiple layers) of elements of Ni, Co, Fe, and Pd. The metal layer 2 is not melted and remains at the soldering temperature when the Cu core ball 11B is used in the solder bump and contributes to the height of the solder joint, so that the sphericity can be high and the variation in diameter is small. and constitute. In addition, from the viewpoint of suppressing soft errors, it is possible to configure such that the amount of α lines is reduced.

･Metal layer composition and film layer When the composition of the metal layer 2 is formed by using a single Ni, Co, Fe, or Pd to constitute the metal layer 2, Ni, Co, Fe, and Pd are 100% except for inevitable 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. Further, 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 obtained by combining two or more elements of Ni, Co, Fe, or Pd as appropriate. It is composed of multiple layers. The film thickness T2 of the metal layer 2 is, for example, 1 μm to 20 μm.

･α-ray amount of Cu core: 0.0200 cph/cm ² or less The α-ray amount of the Cu core 11A of the first embodiment and the Cu core 11B of the second embodiment of the present invention is preferably 0.0200 cph/cm ² or less . This is the amount of alpha to the extent that soft errors do not become a problem in high-density packaging of electronic parts. The α-ray amount of the Cu core ball 11A according to the first embodiment of the present invention can be achieved by the α-ray amount of the solder layer 3 constituting the Cu core ball 11A being 0.0200 cph/cm ² or less. Therefore, since the Cu core ball 11A of the first embodiment of the present invention is covered with such a solder layer 3, it exhibits a low amount of α rays. The α-ray amount of the Cu core ball 11B according to the second embodiment of the present invention can be achieved when the α-ray amount of the metal layer 2 and the solder layer 3 constituting the Cu core ball 11B is 0.0200 cph/cm ² or less. Therefore, the Cu core balls 11B according to the second embodiment of the present invention are covered with the metal layer 2 and the solder layer 3 as described above, and thus exhibit a low amount of α rays. From the viewpoint of suppressing soft errors in further high-density packaging, the α line amount 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 0.0010cph/cm ² or less. In order to set the α-ray amount of the Cu balls 1 to 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. In addition, 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.

･Cu core sphericity: 0.95 or more The Cu core ball 11A of the first embodiment of the present invention in which the Cu ball 1 is covered 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 covered with the metal layer 2 and the solder layer 3 The sphericity is preferably above 0.95, and the true sphericity is preferably above 0.98, more preferably above 0.99. When the sphericity of the Cu core balls 11A and 11B is less than 0.95, the Cu core balls 11A and 11B have an indeterminate shape. Therefore, when the Cu core balls 11A and 11B are mounted on electrodes and reflow is performed, the positional deviation of the Cu core balls 11A and 11B occurs. and the self-alignment becomes poor. When the sphericity of the Cu cores 11A and 11B is 0.95 or more, self-alignment when the Cu cores 11A and 11B are encapsulated on the electrodes 100 and the like of the semiconductor wafer 10 can be ensured. Furthermore, since the sphericity of the Cu balls 1 is also 0.95 or more, since the Cu core balls 11A and 11B do not melt at the temperature at which the Cu balls 1 and the metal layer 2 are welded, variations in the height of the welded joint 50 can be suppressed. Thereby, the bonding failure of the semiconductor wafer 10 and the printed circuit board 40 can be prevented reliably.

･Barrier function of metal layer During reflow, in the solder (paste) used to bond the Cu core ball and the electrode, when Cu in the Cu ball diffuses, a large amount of relatively large amount is formed in the solder layer and the connection interface. When the hard and relatively brittle Cu ₆ Sn ₅ and Cu ₃ Sn intermetallic compounds are subjected to impact, there is a possibility of cracking and destroying the connection portion. Therefore, in order to obtain sufficient connection strength, it is sufficient to suppress (barrier) 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 of the Cu ball 1 into the solder of the paste.

･Solder paste, foam solder, solder tip Moreover, a solder paste can also be comprised by making the solder contain Cu core ball 11A or Cu core ball 11B. The foamed solder can be formed by dispersing the Cu core balls 11A or the Cu core balls 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 joining electrodes.

･Manufacturing method of Cu ball Next, an example of the manufacturing method of the Cu ball 1 is demonstrated. As an example of the metal material, a Cu material is placed on a heat-resistant plate such as ceramics (hereinafter referred to as a "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 grooves can be appropriately set according to the particle size of the Cu balls 1 , and are, for example, 0.8 mm in diameter and 0.88 mm in depth. Further, the wafer-shaped Cu materials obtained by cutting the Cu thin wires were put into the grooves of the heat-resistant plate one at a time. A heat-resistant plate made of Cu material was put into the groove, and the temperature was raised to 1100 to 1300° C. in a furnace filled with ammonia decomposition gas, and heat treatment was performed for 30 to 60 minutes. At this time, when the temperature in the furnace becomes equal to or higher than the melting point of Cu, the Cu material is melted and becomes spherical. Subsequently, the furnace was cooled and formed by quenching the Cu balls 1 in the grooves of the heat-resistant plate.

As another method, there are atomization methods in which molten Cu is dropped from an orifice provided in the bottom of the crucible, the droplets are cooled to room temperature (for example, 25° C.), and the Cu balls 1 are formed into spheroids; and a thermoelectric method. Slurry heats Cu cutting metal to above 1000℃ to form balls.

In the method for producing the Cu balls 1 , the Cu material, which is the raw material of the Cu balls 1 , may be heat-treated at 800 to 1000° C. before the formation of the Cu balls 1 by ball formation.

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

In this way, when a high-purity Cu material is used, 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. in the same manner as before. In this way, the above-mentioned heat treatment system can be appropriately omitted and changed in accordance with the purity of the Cu material and the amount of α rays. In addition, when the Cu balls 1 with a high α-ray amount and the special-shaped Cu balls 1 are produced, these Cu balls 1 can be reused as raw materials, and the α-ray amount can be reduced.

As a method of forming the solder layer 3 on the Cu balls 1, the above-mentioned molten plating method can be used. In addition to the molten plating method, an electroplating method may also be used.

As a method of forming the metal layer 2 on the Cu balls 1, a known method such as electrolytic plating can be used. For example, when forming a Ni plating layer, a Ni plating solution is prepared by using Ni metal bullions or Ni metal salts for the Ni plating bath, and the Cu balls 1 are immersed in the prepared Ni plating solution to make the Ni plating solution. The Ni plating layer is formed on the surface of the Cu ball 1 by precipitation. In addition, as another method of forming the metal layer 2 such as a Ni plating layer, a conventional electroless plating method or the like can be used. When the solder layer 3 is formed on the surface of the metal layer 2 using Sn alloy, the above-mentioned molten plating method, or other electroless plating method or electroplating method can be used. [Example]

Hereinafter, although the Example of this invention is described, this invention is not limited by these. Cu balls of Examples 1 to 19 and Comparative Examples 1 to 12 were produced using the compositions shown in Tables 1 and 2 below, and the sphericity, Vickers hardness, α-ray amount, 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 layers of the solders and solder alloys shown in Table 3, and the Cu core balls of Examples 1A to 19A were produced and the Cu cores were measured. The sphericity of the ball. Furthermore, the Cu balls of Examples 1 to 19 described above were coated with a metal layer and a solder layer using the solders and solder alloys shown in Table 4 of Composition Examples 1 to 21 to produce Cu core balls of Examples 1B to 19B and measured. The sphericity of the Cu core ball.

Furthermore, by coating the Cu balls of Comparative Examples 1 to 12 with the solder layers of the composition examples 1 to 21 and the solder alloys shown in Table 5, the Cu balls of Comparative Examples 1A to 12A were produced and the Cu balls were measured. sphericity. In addition, by coating the Cu balls of Comparative Examples 1 to 12 with a metal layer and the solder layers of the composition examples 1 to 21 and the solder alloys shown in Table 6, the Cu core balls of Comparative Examples 1B to 12B were produced and measured. The sphericity of Cu nuclei.

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

･Manufacture of Cu balls The manufacturing conditions of Cu balls were examined. As an example of a metal material, a Cu material is prepared as a bulk metal material. As the Cu materials of Examples 1 to 13, 19, and Comparative Examples 1 to 12, those with a purity of 6N were used, and as the Cu materials of Examples 14 to 18, those with a purity of 5N were used. After each Cu material was put 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 droplets were quenched to At room temperature (18°C), the balls were formed into Cu balls. Thereby, Cu balls whose average particle diameters are the values shown in the following tables were produced. The elemental analysis system can be analyzed with high accuracy using inductively coupled plasma mass analysis (ICP-MS analysis) and glow discharge mass analysis (GD-MS analysis). In this example, the spherical diameter of the Cu balls analyzed by ICP-MS was set to 250 μm in Examples 1 to 19 and Comparative Examples 1 to 12.

． Fabrication of Cu core balls

Using the Cu balls of the above-mentioned Examples 1 to 19, for the Examples 1A to 19A, the thickness of one side was 23 μm, and the solder and the solder alloy of the composition examples 1 to 21 were used, and the solder layer was formed by the molten plating method. Cu core balls of Examples 1A~19A.

In addition, the Cu balls of the above-mentioned Examples 1 to 19 were used, and for Examples 1B to 19B, the Ni plating layer was formed with a thickness of 2 μm on one side as a metal layer, and the thickness of one side was 23 μm, and Composition Examples 1 to 21 were used. The solder and solder alloy were formed by molten plating to form a solder layer to manufacture the Cu core balls of Examples 1B to 19B.

The Cu core balls of Comparative Examples 1A to 12A were produced by using the Cu balls of Comparative Examples 1 to 12 and forming a solder layer with a thickness of 23 μm on one side and using the solders and solder alloys of Composition Examples 1 to 21. In addition, the Cu balls of Comparative Examples 1 to 12 were used to form a Ni-plated layer 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 solders and solder alloys of Composition Examples 1 to 21. Cu core balls of Comparative Examples 1B to 12B were produced.

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

． sphericity

The sphericity of Cu balls and Cu core balls was measured using a CNC video measurement system. The devices were Ultra Quick Vision, ULTRA QV350-PRO manufactured by Mitutoyo Corporation.

[Evaluation criteria for sphericity] In the following tables, the evaluation criteria for the sphericity of Cu balls and Cu core balls are as follows. ○○○: sphericity is 0.99 or more ○○: sphericity is 0.98 or more and less than 0.99 ○: sphericity is 0.95 or more and less than 0.98 ×: 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". The apparatus was a micro Vickers hardness tester manufactured by Akashi Seisakusho, AKASHI micro hardness tester MVK-F 12001-Q.

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

･α line amount The measurement method of the α-ray amount of the Cu ball is as follows. The measurement of the α-line amount was performed using an α-line measurement device using an airflow proportional counter. The measurement sample was placed in a flat, shallow-bottomed container of 300 mm×300 mm, and the Cu balls were spread until the bottom of the container could not be seen. This measurement sample was put into an α-ray measuring apparatus, and after standing in a PR-10 airflow for 24 hours, the amount of α-ray was measured.

[Evaluation Criteria of α-ray amount] In the following tables, the evaluation criteria of the α-ray amount of Cu balls are as follows. ○: α line amount is 0.0200cph/cm ² or less ×: α line amount is more than 0.0200cph/cm ²

In addition, the PR-10 gas (90% of argon-10% of methane) used for the measurement was obtained after 3 weeks or more had elapsed after the PR-10 gas was filled in the gas high pressure tank. The high-pressure tank that has been used for more than 3 weeks is in accordance with 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 Development Association), The reason is that radon (radon) in the atmosphere entering the gas high-pressure tank does not produce alpha lines.

･Discoloration resistance In order to measure the discoloration resistance of the 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 also evaluated whether the Cu balls could sufficiently withstand the change with time. . The luminance was measured using a spectrophotometer, type CM-3500d, manufactured by Konica Minolta, under a D65 light source, a 10-degree field of view, and in accordance with JIS Z 8722 "Determination of Color-Reflecting and Transmitting Object Colors". L*,a*,b*) to obtain. In addition, (L*, a*, b*) is defined in JIS Z 8729 "Representation of color - L*a*b* colorimetric system and L*u*v* colorimetric system". L* is brightness, a* is redness, a* is yellowness.

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

·Overview The Cu balls whose sphericity, Vickers hardness, α-ray amount, and discoloration resistance were ○, ○○, or ○○○ in the above-mentioned evaluation method and evaluation criteria were evaluated as ○ in the comprehensive evaluation. On the other hand, the Cu balls whose sphericity, Vickers hardness, α-ray amount, and discoloration resistance are x is evaluated as x in the comprehensive evaluation.

In addition, the Cu core balls whose sphericity was ○, ○○, or ○○○ in the above-mentioned evaluation method and evaluation criteria were evaluated as ○ in the comprehensive evaluation together with the evaluation of the Cu balls. On the other hand, the Cu core ball whose sphericity is × is evaluated as × in the comprehensive evaluation. Furthermore, even if the evaluation sphericity of the Cu core ball is ○, ○○ or ○○○, the evaluation of the sphericity, Vickers hardness, α-ray amount and discoloration resistance of the Cu ball is x. The Cu core ball was rated as × by the comprehensive evaluation.

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

On the other hand, when the Vickers hardness of the Cu balls of the Cu core balls is large and exceeds the range specified in the present invention, the durability against external stress is lowered and the drop shock resistance is deteriorated, which cannot be solved. The problem of cracking occurs.

Therefore, since the Cu core balls of the Cu balls of Comparative Examples 8 to 11 having a Vickers hardness greater than 55.5HV were used, they were not suitable for the evaluation of the Vickers hardness, so the comprehensive evaluation was rated as ×.

In addition, since the discoloration resistance of the Cu core ball depends on the Ni plating layer, which is an example of the solder layer and the metal layer, the discoloration resistance of the Cu core ball is not evaluated. However, when the brightness of the Cu ball is within the range specified in the present invention, the sulfide and oxysulfide on the surface of the Cu ball can be suppressed, and the coating of a metal layer such as a solder layer and a Ni plating layer can be suitably used.

On the other hand, when the brightness of Cu balls is lower than the range specified in the present invention, Cu balls cannot suppress sulfides and oxysulfides on the surface and are not suitable for coating with metal layers such as solder layers and Ni plating layers.

Therefore, since the Cu core balls of the Cu balls of Comparative Examples 1 to 6 whose brightness after 420 seconds was less than 55 were used, they were not suitable for the evaluation of discoloration resistance, so the comprehensive evaluation was rated as ×.

In addition, the amount of α rays of the Cu core ball depends on the composition of the raw material of the plating solution constituting the solder layer covering the Cu ball 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 material of the electroplating solution constituting the Ni layer.

When the Cu ball is the low α line amount specified in the present invention, and the raw material of the plating solution constituting the solder layer and the Ni plating layer is the low α line amount specified in the present invention, the Cu core ball also becomes the low α line amount specified in the present invention. On the other hand, when the raw material of the electroplating solution constituting the solder layer and the Ni plating layer has a high α-ray amount larger than the α-ray specified in the present invention, even if the Cu ball has the above-mentioned low α-ray amount, the Cu core ball is larger than the specified amount of the present invention. The high alpha line amount of the alpha line amount.

[表1]

[Table 1]

[表2]

[Table 2]

[table 3]

[Table 4]

[表5]

[table 5]

[表6]

[Table 6]

As shown in Table 1, all of the Cu ball systems of the respective Examples having a purity of 4N5 or more and 5N5 or less obtained favorable results in comprehensive evaluation. Therefore, the purity of the Cu balls can be said to be preferably 4N5 or more and 5N5 or less.

The details of the evaluation are described below. For example, 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 in the sphericity. , Vickers hardness, α line amount 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 containing Fe, Ag and Ni in a total of 5.0 mass ppm or more and 50.0 mass ppm or less in total have good sphericity, Vickers hardness, α-line amount and A good result was also obtained in the comprehensive evaluation of discoloration resistance. In addition, it is not shown in the table that from Examples 1, 18, and 19, the Fe content was changed to 0 mass ppm or more and less than 5.0 mass ppm, the Ag content was changed to 0 ppm or more and less than 5.0 mass ppm, and the Ni content was changed to 0 ppm or more and less than 5.0 mass ppm. Cu balls whose content is changed to 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 are also evaluated in comprehensive evaluation of sphericity, Vickers hardness, α-ray amount, and discoloration resistance. Good results can be obtained.

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

For the Cu core ball, as shown in Tables 3 and 4, by using the solder layer of the solder alloy of Composition Example 1 containing 100% by mass (but can contain unavoidable impurities) Sn, Examples 1 to Examples are covered Cu core balls of Examples 1A to 19A formed from Cu balls of 19; and Cu balls of Examples 1 to 19 coated with Ni plating layers, and then coated with a solder layer of the solder alloy of Composition Example 1 The Cu core balls of Examples 1B to 19B can also obtain good results in the comprehensive evaluation of sphericity.

The Cu core balls of Examples 1A to 19A formed by coating the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 2 containing 2 mass ppm of Ge and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with a Ni-plated layer, and then of the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 2 Good results can also be obtained.

The Cu core balls of Examples 1A to 19A formed by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 3 containing 25 mass ppm of Ge and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with a Ni-plated layer, and then of the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 3 Good results can also be obtained.

The Cu core balls of Examples 1A to 19A formed by coating the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 4 containing 50 mass ppm of Ge and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with a Ni-plated layer, and the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 4. Good results can also be obtained.

The Cu core balls of Examples 1A to 19A formed by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 5 containing 100 mass ppm of Ge and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with a Ni-plated layer, and the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 5 Good results can also be obtained.

The Cu core balls of Examples 1A to 19A formed by coating the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 6 containing 200 mass ppm of Ge and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with a Ni plating layer, and the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 6 Good results can also be obtained.

The Cu core balls of Examples 1A to 19A formed by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 7 containing 220 mass ppm of Ge and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with a Ni plating layer, and the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 7 Good results can also be obtained.

The Cu core balls of Examples 1A to 19A formed by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 8 containing 0.7 mass % of Cu and the remainder being Sn; and Comprehensive evaluation of the sphericity of the Cu balls of Examples 1 to 19 coated with Ni plating layers, and the Cu core balls of Examples 1B to 19B coated with the solder layer of the solder alloy of Composition Example 8 Good results can also be obtained.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 9 containing 0.7 mass % of Cu, 2 mass ppm of Ge and the remainder being Sn The Cu core balls of Examples 1 to 19 were coated with a Ni plating layer, and then the Cu core balls of Examples 1B to 19B were coated with the solder layer of the solder alloy of Composition Example 9. The comprehensive evaluation of sphericity can also obtain good results.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 10 containing 0.7 mass % of Cu, 25 mass ppm of Ge and the remainder being Sn The Cu core balls of Examples 1 to 19 were coated with the Ni plating layer, and then the Cu core balls of Examples 1B to 19B were coated with the solder layer of the solder alloy of Composition Example 10. The comprehensive evaluation of sphericity can also obtain good results.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 11 containing 0.7 mass % of Cu, 50 mass ppm of Ge and the remainder being Sn The Cu core balls of Examples 1 to 19 were coated with the Ni plating layer, and then the Cu core balls of Examples 1B to 19B were coated with the solder layer of the solder alloy of Composition Example 11. The comprehensive evaluation of sphericity can also obtain good results.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 12 containing 0.7 mass % of Cu, 100 mass ppm of Ge and the remainder being Sn The Cu core balls of Examples 1 to 19 were coated with a Ni plating layer, and then the Cu core balls of Examples 1B to 19B were coated with the solder layer of the solder alloy of Composition Example 12. The comprehensive evaluation of sphericity can also obtain good results.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 13 containing 0.7 mass % of Cu, 200 mass ppm of Ge and the remainder being Sn The Cu core balls of Examples 1 to 19 were coated with the Ni plating layer, and then the Cu core balls of Examples 1B to 19B were coated with the solder layer of the solder alloy of Composition Example 13. The comprehensive evaluation of sphericity can also obtain good results.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 14 containing 0.7 mass % of Cu, 220 mass ppm of Ge and the remainder being Sn and the Cu core balls of Examples 1B to 19B coated with the Cu balls of Examples 1 to 19 with a Ni plating layer, and then coated with the solder layer of the solder alloy of Composition Example 14, in The comprehensive evaluation of sphericity can also obtain good results.

Examples 1A to 19A obtained by covering the Cu balls of Examples 1 to 19 by using the solder layer of the solder alloy of Composition Example 15 containing 3.0 mass % Ag, 0.5 mass % Cu and the remainder being Sn The Cu core balls of Examples 1 to 19 were coated with the Ni plating layer, and then the Cu core balls of Examples 1B to 19B were coated with the solder layer of the solder alloy of Composition Example 15. The comprehensive evaluation of sphericity can also obtain good results.

By using the solder layer of the solder alloy of Composition Example 16 containing 3.0 mass % of Ag, 0.5 mass % of Cu, 2 mass ppm of Ge, and the remainder being Sn, the Cu balls of Examples 1 to 19 were covered with the solder layer. 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 plating layer, and then coating with the solder layer of the solder alloy of Composition Example 16 Good results can also be obtained in the comprehensive evaluation of the sphericity of the Cu core ball.

By using the solder layer of the solder alloy of Composition Example 17 containing 3.0 mass % of Ag, 0.5 mass % of Cu, 25 mass ppm of Ge, and the remainder being Sn, the Cu balls of Examples 1 to 19 were covered with the solder layer. 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 plating layer, and then coating with the solder layer of the solder alloy of Composition Example 17 Good results can also be obtained in the comprehensive evaluation of the sphericity of the Cu core ball.

By using the solder layer of the solder alloy of Composition Example 18 containing 3.0 mass % Ag, 0.5 mass % Cu, 50 mass ppm Ge and the remainder being Sn, the Cu balls of Examples 1 to 19 were covered 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 plating layer, and then coating with the solder layer of the solder alloy of Composition Example 18 Good results can also be obtained in the comprehensive evaluation of the sphericity of the Cu core ball.

By using the solder layer of the solder alloy of Composition Example 19 containing 3.0 mass % Ag, 0.5 mass % Cu, 100 mass ppm Ge and the remainder being Sn, the Cu balls of Examples 1 to 19 were covered 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 plating layer, and then coating with the solder layer of the solder alloy of Composition Example 19 Good results can also be obtained in the comprehensive evaluation of the sphericity of the Cu core ball.

By using the solder layer of the solder alloy of composition example 20 containing 3.0 mass % of Ag, 0.5 mass % of Cu, 200 mass ppm of Ge, and the remainder being Sn, the Cu balls of Examples 1 to 19 were covered with the solder layer. 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-plating layer, and then coating with the solder layer of the solder alloy of Composition Example 20 Good results can also be obtained in the comprehensive evaluation of the sphericity of the Cu core ball.

By using the solder layer of the solder alloy of Composition Example 21 containing 3.0 mass % Ag, 0.5 mass % Cu, 220 mass ppm Ge and the remainder being Sn, the Cu balls of Examples 1 to 19 were covered 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 plating layer, and then coating with the solder layer of the solder alloy of Composition Example 21 Good results can also be obtained in the comprehensive evaluation of the sphericity of the Cu core ball.

In addition, not shown in the table, from Examples 1, 18, and 19, the Fe content was changed to 0 mass ppm or more and less than 5.0 mass ppm, the Ag content was changed to 0 ppm or more and less than 5.0 mass ppm, and the Ni content was changed to 0 ppm or more and less than 5.0 mass ppm. The content is changed to 0 mass ppm or more and less than 5.0 mass ppm and the total of Fe, Ag and Ni is Cu balls of 5.0 mass ppm or more, by using the solder or solder alloy of any one of Composition Example 1 to Composition Example 21 The Cu core ball is covered with the solder layer, and the Cu ball is covered with the Ni plating layer, and the Cu core is covered with the solder layer of any one of the composition example 1 to the composition example 21, and the solder alloy is used. good results can also be obtained in the comprehensive evaluation of sphericity.

On the other hand, the Cu ball system of Comparative Example 7 not only did not have a total content of Fe, Ag and Ni of 5.0 mass ppm, but also U and Th were less than 5 mass ppb, and other impurity elements were also less than 1 mass ppm. Balls, Cu core balls of Comparative Example 7A obtained by coating the Cu balls of Comparative Example 7 with a solder layer using the solder and solder alloy of each composition example, and Cu balls of Comparative Example 7 coated with a Ni plating layer, and further The sphericity of the Cu core ball system of Comparative Example 7B, which was covered with the solder layer of each composition example and the solder alloy, did not reach 0.95. In addition, the Cu balls of Comparative Example 12 in which the total content of at least one of Fe, Ag, and Ni did not reach 5.0 mass ppm even if the impurity element was contained, the Cu balls of Comparative Example 12 were prepared by using the solders and solders of each composition example. The Cu core ball of Comparative Example 12A coated with the solder layer of the alloy, and the Cu ball of Comparative Example 12 coated with the Ni plating layer, and then coated with the solder layer of each composition example and the solder alloy. The sphericity of 12B Cu nuclei did not reach 0.95. From these results, Cu balls in which the total content of at least one of Fe, Ag, and Ni does not reach 5.0 mass ppm, Cu balls in which the Cu balls are coated with a solder layer using the solder or solder alloy of each composition example It can be said that high sphericity cannot be achieved by coating the core ball and the Cu ball with the Ni plating layer, and further coating the Cu core ball with the solder layer of each composition example and the solder alloy.

Further, in Comparative Example 10, the Cu spherical content of Fe, Ag, and Ni was 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, the total content of Fe, Ag, and Ni was 150.0 mass ppm, and the content of other impurity elements, especially Sn, was 151.0 mass ppm, which was significantly higher than 50.0 mass ppm, and the Vickers hardness was Above 55.5HV, good results cannot be obtained. Therefore, even if the purity of Cu balls is 4N5 or more and 5N5 or less, the Vickers hardness of Cu balls with a total content of at least one of Fe, Ag and Ni exceeding 50.0 mass ppm increases and it can be said that low hardness cannot be achieved. As described above, when the Vickers hardness of the Cu ball is larger than the range specified in the present invention, the durability against external stress is lowered and the drop shock resistance is deteriorated, but the problem that cracks are easily generated cannot be solved. Furthermore, it can be said that it is preferable to contain other impurity elements in a range of not more than 50.0 mass ppm each.

From these results, Cu balls with a purity of 4N5 or more and 5N5 or less and containing at least one of Fe, Ag, and Ni in a total content of 5.0 mass ppm or more and 50.0 mass ppm or less can be said to be able to achieve high sphericity. And low hardness and inhibit discoloration. The Cu core balls formed by coating the Cu balls with the solder of each composition example and the solder layer of the solder alloy, and coating the Cu ball with the Ni plating layer, and further by using the solder of each composition example and the solder of the solder alloy The layer-coated Cu core ball system achieves high sphericity, and by realizing the low hardness of the Cu ball, as the Cu core ball, the drop shock resistance is also good, and cracking and electrode collapse can also be suppressed. Deterioration of conductivity can also be suppressed. Furthermore, since the discoloration of Cu balls can be suppressed, it is suitable for coating of metal layers such as solder layers and Ni plating layers. The content of other impurity elements is preferably 50.0 mass ppm or less, respectively.

Not shown in the table, Cu balls with the same composition as those in the Examples and having a ball diameter of 1 μm or more and 1000 μm or less can be comprehensively evaluated in terms of sphericity, Vickers hardness, α-ray amount, and discoloration resistance. Got good results. Therefore, it can be said that the spherical diameter of the Cu balls is preferably 1 μm or more and 1000 μm or less, and more preferably 50 μm or more and 300 μm or less.

The Cu ball of Example 19 has a total content of Fe, Ag, and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less and contains 2.9 mass ppm of P, and has a high degree of sphericity, Vickers hardness, α-ray amount, and discoloration resistance. Comprehensive evaluation can get good results. The Cu balls of Example 19 were coated with the solder layer of each composition example, and the Cu core ball was coated with the solder layer of the solder alloy, and the Cu ball of Example 19 was coated with the Ni plating layer, and then the solder of each composition example was used. . The Cu core balls covered by the solder layer of the solder alloy have obtained good results in the comprehensive evaluation of the sphericity. The Cu balls of Comparative Example 11 have a total content of Fe, Ag, and Ni of 50.0 mass ppm or less like the Cu balls of Example 19, but the Vickers hardness is greater than 5.5HV, which is different from the Cu balls of Example 19. result. In addition, the Vickers hardness of Comparative Example 9 was also larger than 5.5HV. This is considered to be because the P content of Comparative Examples 9 and 11 was significantly larger, 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, and more preferably less than 1 mass ppm.

In the Cu balls of the respective examples, the amount of α rays was 0.0200 cph/cm ² or less. Therefore, in the solders and solder alloys of Composition Example 1 and Composition Example 2 covering the Cu balls of Examples 1 to 19, since each element has a low α radiation amount specified in the present invention, the Cu core balls of Examples 1A to 19A are also It becomes the low alpha line amount specified in the present invention. In addition, when the Ni plating layer, which is an example of the metal layer covering the Cu balls, is provided, in addition to the solder and the solder alloy, each element constituting the Ni plating layer is the low α line quantity specified in the present invention, and each of Examples 1B~ The Cu core ball of 19B also becomes the low α line quantity specified in the present invention.

Accordingly, when the Cu core balls of the respective examples are used in high-density packaging of electronic components, soft errors can be suppressed by using the raw material of the electroplating solution constituting the solder layer and the Ni plating layer to be the low α line quantity specified in the present invention.

In the Cu balls of Comparative Example 7, good results were obtained in the discoloration resistance, but on the other hand, in the systems of Comparative Examples 1 to 6, good results were not obtained in the discoloration resistance. When the Cu balls of Comparative Examples 1 to 6 are compared with the Cu balls of Comparative Example 7, the difference in these compositions is only the content of S. Therefore, in order to obtain favorable results in discoloration resistance, it can be said that the content of S must be less than 1 mass ppm. The content of S in any of the Cu balls of each example is less than 1 mass ppm, and it can be said that the content of S 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 at 420°C. seconds later and measure the brightness. Table 7 and FIG. 4 are graphs showing the relationship between the heating time of each Cu ball and the brightness.

[表7]

[Table 7]

From this table, when the brightness before heating was compared with the brightness after heating for 420 seconds, the brightness of Example 14 and Comparative Examples 1 and 5 were 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 the order of Comparative Example 1 containing 10.0 mass ppm of S, and Example 14 containing S content of less than 1 mass ppm . Therefore, it can be said that the higher the content of S, the lower the brightness after heating. Since the Cu balls of Comparative Examples 1 and 5 had a brightness of less than 55, the Cu balls containing 10.0 mass ppm or more of S formed sulfides and sulfur oxides when heated, and it can be said that they were easily discolored. Moreover, when the content of S is 0 mass ppm or more and 1.0 mass ppm or less, the formation of sulfides and sulfur oxides can be suppressed, and it can be said that the wettability is good. In addition, when the Cu ball of Example 14 was encapsulated on the electrode, good wettability was exhibited.

As above, the purity is 4N5 or more and 5N5 or less, 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, the S content is 0 mass ppm or more and 1.0 mass ppm or less, P The Cu balls of the present example whose content is 0 mass ppm or more and less than 3.0 mass ppm can achieve high sphericity because the sphericity of both is 0.95 or more. By realizing high sphericity, self-alignment can be ensured when the Cu balls are encapsulated in electrodes or the like, and variation in the height of the Cu balls can be suppressed. The Cu core balls obtained by covering the Cu balls of this embodiment with solder and a solder layer; and the Cu core balls obtained by covering the Cu balls of this embodiment with a metal layer, and further using solder and a solder layer to coat the metal layers can obtain the same Cu core balls. Effect.

In addition, since the Vickers hardness of any of the Cu ball systems of the present Example is 55HV or less, low hardness can be realized. By realizing low hardness, the drop shock resistance of the Cu ball can be improved. By realizing the low hardness of the Cu balls, the Cu core balls formed by coating the Cu balls of the present embodiment with solder and a solder layer; The resulting Cu core balls have good drop shock resistance and can suppress cracks, and can also suppress electrode collapse, etc., and can also suppress deterioration of electrical conductivity.

In addition, any of the Cu ball systems of the present Example can suppress discoloration. By suppressing the discoloration of the Cu balls, it is possible to suppress the adverse effects of sulfides and sulfur oxides on the Cu balls, and to improve the wettability when the Cu balls are encapsulated on the electrodes. Since the discoloration of Cu balls can be suppressed, it is suitable to use coating of metal layers such as solder layers and Ni plating layers.

Furthermore, the Cu material of this example uses a Cu bulk metal material with a purity of more than 4N5 and less than 6N, and produces Cu balls with a purity of more than 4N5 and less than 5N5, but even if a metal wire or a plate with a purity of more than 4N5 and less than 6N is used etc., good results can be obtained in the comprehensive evaluation of both Cu balls and Cu core balls.

Next, the effect of suppressing the increase in the thickness of the oxide film on the surface of the Cu core ball by adding Ge in the Cu core ball formed by coating the surface of the Cu ball with a solder layer containing a solder alloy containing Sn and Ge will be described.

In the following examples, Cu balls having the composition of Example 17 shown in Table 1 were used to obtain the required sphericity and the like, and Cu core balls were produced by the molten plating method, and the oxide film thickness was measured using the Cu core balls. . The ball diameter of the Cu ball was set to 250 μm, the Ni plating layer was formed with a thickness of 2 μm on one side as a metal layer, and the solder layer was formed with a thickness of 23 μm on one side by the molten plating method using the solder alloys of Composition Examples 16 to 21. The Cu core balls of Examples 1C to 6C were produced. In addition, the ball diameter of the Cu ball was set to 250 μm, a Ni plating layer was formed with a thickness of 2 μm on one side as a metal layer, and a solder layer was formed with a thickness of 23 μm on one side by the molten plating method using the solder alloy of Composition Example 15. The Cu core balls of Comparative Example 1C were produced.

(a) Solder layer composition In the Cu core ball of Example 1C, the composition of the solder layer was the solder alloy of Composition Example 16, which contained 3.0 mass % of Ag, 0.5 mass % of Cu, and 2 mass ppm of Ge, and the remainder was Sn. In the Cu core ball of Example 2C, the composition of the solder layer was the solder alloy of Composition Example 17, which contained 3.0 mass % Ag, 0.5 mass % Cu, 25 mass ppm Ge, and the remainder was Sn. In the Cu core ball of Example 3C, the composition of the solder layer was the solder alloy of Composition Example 18, which contained 3.0 mass % of Ag, 0.5 mass % of Cu, and 50 mass ppm of Ge, and the remainder was Sn. In the Cu core ball of Example 4C, the composition of the solder layer was the solder alloy of Composition Example 19, which contained 3.0 mass % Ag, 0.5 mass % Cu, 100 mass ppm Ge, and the remainder was Sn. In the Cu core ball of Example 5C, the composition of the solder layer is the solder alloy of Composition Example 20, which contains 3.0 mass % Ag, 0.5 mass % Cu, 200 mass ppm Ge, and the remainder is Sn. In the Cu core ball of Example 6C, the composition of the solder layer was the solder alloy of Composition Example 21, which contained 3.0 mass % Ag, 0.5 mass % Cu, 220 mass ppm Ge, and the remainder was Sn. In the Cu core ball of Comparative Example 1C, the composition of the solder layer was the solder alloy of Composition Example 15, which contained 3.0 mass % of Ag, 0.5 mass % of Cu, and the remainder was Sn.

(b) Measurement of oxide film thickness After each of the Cu core balls of the Examples and the Cu core balls of the Comparative Examples was heat-treated in a constant temperature bath at 150° C. for varying times, the oxide film thickness was measured by FE-AES. The oxide film thickness is a SiO2 conversion value. Table 8 shows the oxide film thickness. In Table 8, the unit of oxide film thickness is (nm).

[Table 8]

As shown in Table 8, Cu of each Example formed by forming a solder layer by a molten plating method using a Sn-3Ag-0.5Cu alloy and a solder alloy having a Ge content of 2 mass ppm or more and 220 mass ppm or less was used. For the nucleus, a large increase in the oxide film thickness could not be observed even if the heating time was increased. On the other hand, in the Cu core ball of the comparative example, which is a Sn-3Ag-0.5Cu alloy and does not contain Ge, the oxide film thickness greatly increases as the heating time increases.

Therefore, it was found that adding a predetermined Ge to the solder alloy can improve the oxidation resistance. The effect of improving the oxidation resistance can be more greatly obtained when the content of Ge is 50 mass ppm or more. Therefore, the content of Ge is preferably 50 ppm or more. In addition, when the content of Ge is increased, the solder wettability tends to be deteriorated. Therefore, the content of Ge is 220 mass ppm or less.

1‧‧‧Cu ball 11A, 11B‧‧‧Cu core ball 2‧‧‧Metal layer 3‧‧‧Solder layer 10‧‧‧Semiconductor Chips 100, 41‧‧‧electrode 30‧‧‧Solder bumps 40‧‧Printed substrate 50‧‧‧Welding Head 60‧‧‧Electronic Parts

Fig. 1 is a diagram showing a Cu core ball according to the first embodiment of the present invention. Fig. 2 is a diagram showing a Cu core ball according to the 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 graph showing the relationship between the heating time and the brightness after heating the Cu balls of Examples and Comparative Examples at 200°C.

1‧‧‧Cu ball

11A‧‧‧Cu core ball

3‧‧‧Solder layer

Claims (15)

A Cu core ball comprising Cu balls and a solder layer covering the surfaces of the Cu balls, wherein the Cu balls have 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 The content of S is 0 mass ppm or more and 1.0 mass ppm or less, the P content is 0 mass ppm or more and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, and the purity of the aforementioned Cu balls is 99.995 mass % or more and 99.9995 Mass % or less, sphericity is 0.95 or more, and the solder layer is Sn, an alloy containing Sn and a Sn content of 40 mass % or more, an alloy containing Sn and Ge, or an alloy containing Sn and Ge and a Sn content of 40 mass % or more. In the alloy, the content of Ge in the solder layer is more than 0 mass ppm and 220 mass ppm or less. The Cu core ball according to claim 1, wherein the content of Ge in the solder layer is 50 mass ppm or more and 220 mass ppm or less. The Cu core ball according to claim 1, comprising a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with the solder layer, and the sphericity is 0.95 or more, and the metal layer is composed of a single A layer composed of Ni, Co, Fe, or Pd, or a layer of an alloy obtained by combining two or more elements from Ni, Co, Fe, or Pd. The Cu core ball according to claim 3, wherein the content of Ge in the solder layer is more than 0 mass ppm and 220 mass ppm or less. The Cu core ball according to claim 3, wherein the content of Ge in the solder layer is 50 mass ppm or more and 220 mass ppm or less. The Cu core ball as described in any one of claims 1 to 5, wherein the sphericity is 0.99 or more. The Cu core ball according to any one of claims 1 to 5, wherein the amount of α rays is 0.0010 cph/cm ² or less. The Cu core ball according to any one of Claims 1 to 5, wherein the sphericity is 0.99 or more, and the α-ray amount is 0.0010 cph/cm ² or less. The Cu core ball according to any one of claims 1 to 5, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. The Cu core ball according to any one of claims 1 to 5, wherein the sphericity is 0.99 or more, and the diameter of the Cu ball is 1 μm or more and 1000 μm or less. The Cu core ball according to any one of claims 1 to 5, wherein the amount of α rays is 0.0010 cph/cm ² or less, and the diameter of the Cu ball is 1 μm or more and 1000 μm or less. The Cu core ball according to any one of claims 1 to 5, wherein the sphericity is 0.99 or more, the α-ray amount is 0.0010 cph/cm ² or less, and the diameter of the Cu ball is 1 μm or more and 1000 μm or less . A solder joint uses the Cu core ball as described in any one of the first to twelfth claims of the patent application. A solder paste using the Cu core ball as described in any one of the 1st to 12th patent application scope. A foamed solder using the Cu core ball as described in any one of the 1st to 12th patent application scope.

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