TW202003869A - Cu core ball, solder joint, solder paste, and foam solder having high sphericity and low hardness and coated with a metal layer on a Cu ball in which discoloration is suppressed - Google Patents

Abstract

The present invention provides a Cu core ball which can materialize a high sphericity and low hardness and utilizes a Cu ball coated with a metal layer so that discoloration is suppressed, and a solder joint using the Cu core ball, a solder paste and a foam solder. The solution of the present invention is a Cu core ball 11A which includes: a Cu ball 1 and a solder layer 3 covering the surface of the Cu ball 1, wherein the Cu ball 1 includes a total content of at least one of Fe, Ag, and Ni being 5.0 mass ppm or more and 50.0 mass ppm or less, a content of S being 0 mass ppm or more and 1.0 mass ppm or less, a content of P being 0 mass ppm or more and less than 3.0 mass ppm, and the balance being Cu and other impurity elements. The purity of the Cu ball 1 is 99.995% by mass or more and 99.9995% by mass or less, the sphericity is 0.95 or more, and the solder layer is made of Sn-Pb-based solder alloy containing Sn and Pb.

Description

Cu core ball, solder joint, solder paste and foam solder

The invention relates to a Cu core ball covering a Cu ball with a metal layer, and a soldering joint, solder paste and foam solder using the Cu core ball.

In recent years, due to the development of small information equipment, the electronic components loaded have been rapidly miniaturized. For electronic components, in order to meet the requirements of miniaturization and to narrow the pitch of the corresponding connection terminals or the structure area, a ball grid array (hereinafter, referred to as "BGA") in which electrodes are provided on the back side is used.

For electronic parts using BGA, for example, there are semiconductor packages. For semiconductor packaging, the semiconductor wafer with electrodes is sealed with resin. Solder bumps are formed on the electrodes of the semiconductor wafer. The solder bumps are formed by bonding solder balls to the electrodes of the semiconductor wafer. The semiconductor package using BGA is mounted on the printed circuit board by bonding the solder bumps heated and melted to the conductive contacts of the printed circuit board. Furthermore, in order to cope with the requirements of higher-density packaging, there are studies on 3-dimensional high-density packaging in which semiconductor packages are stacked in the height direction.

The high-density packaging of electronic parts sometimes causes soft errors that cause the memory contents to be rewritten due to alpha rays entering the memory cells of semiconductor integrated circuits (ICs). Therefore, in recent years, development of low alpha-ray welding materials and Cu balls for reducing the content of radioisotopes has been carried out. Patent Document 1 discloses a low α-ray Cu ball containing Pb and Bi and having a purity of 99.9% or more and 99.995% or less. Patent Document 2 discloses a Cu ball having a purity of 99.9% or more and 99.995% or less, a true sphericity of 0.95 or more, and a Vickers hardness of 20 HV or more and 60 HV or less.

However, if the crystal grains of the Cu balls are fine, the Vickers hardness becomes large, so the durability against external stress becomes low, and the drop impact resistance becomes poor. Therefore, Cu balls used for electronic component construction require a predetermined degree of flexibility, that is, a Vickers hardness below a predetermined value.

In order to manufacture soft Cu balls, the practice is to increase the purity of Cu. In this system, the impurity element acts as a crystal nucleus in the Cu ball, so if the impurity element is reduced, the crystal grains will grow greatly, and as a result, the Vickers hardness of the Cu ball will become small. However, if the purity of the Cu ball is increased, the true sphericity of the Cu ball will become lower.

When the true sphericity of the Cu ball is low, there is a possibility that the self-alignment when the Cu ball is mounted on the electrode may not be ensured. At the same time, when the semiconductor wafer is mounted, the height of the Cu ball becomes uneven. Causes poor bonding.

Patent Document 3 discloses a Cu ball in which the mass ratio of Cu exceeds 99.995%, the total mass ratio of P and S is 3 ppm or more and 30 ppm or less, and has an appropriate true sphericity and Vickers hardness.

In addition, the semiconductor package for high-density three-dimensional packaging is a BGA. When the solder balls are loaded on the electrodes of the semiconductor wafer for reflow processing, the solder balls may be crushed by the weight of the semiconductor package. If such a situation occurs, it may be considered that the solder will overflow from the electrodes, connecting the electrodes and causing a short circuit.

In order to prevent such a short circuit accident, it has been proposed to use solder that will not be crushed by its own weight or that will not deform when the solder melts. Specifically, it is proposed to use a molded ball of metal or the like as a core, and the core material covered with solder as a solder bump. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5435182 [Patent Document 2] Japanese Patent No. 5585571 [Patent Document 3] Japanese Patent No. 6256616

[Problems to be solved by the invention]

However, Cu balls containing a certain amount or more of S have a problem that sulfides or sulfur oxides are easily formed and discolor when heated. The discoloration of the Cu ball will cause the deterioration of the wettability, and the deterioration of the wettability will lead to the deterioration of non-wetting or self-alignment. In this way, the Cu balls that are easily discolored are not suitable for being covered with a metal layer because the adhesion between the surface of the Cu balls and the metal layer decreases or the oxidation or reactivity of the surface of the metal layer becomes high. On the other hand, when the true sphericity of the Cu ball is low, the true sphericity of the Cu core ball covered with the metal layer also becomes low.

Therefore, an object of the present invention is to provide a Cu core ball capable of realizing a high degree of sphericity and a low hardness while suppressing discoloration of Cu balls, and a solder joint, solder paste, and foam solder using the Cu core ball. [Means for solving problems]

The invention is as follows. (1) A Cu core ball comprising: a Cu ball; and a solder layer covering the surface of the Cu ball, the Cu ball being at least one of Fe, Ag, and Ni, the total content of which is 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 content of P is 0 mass ppm or more and less than 3.0 mass ppm, the balance is Cu and other impurity elements, and the purity of the Cu balls is 99.995 mass% or more and (Sn-Pb) type solder alloy containing 99.9995 mass% or less, a true sphericity of 0.95 or more, and a solder layer system containing Sn and Pb. (2) The Cu core ball as described in (1) above, wherein the content of Pb in the solder layer is 0% by mass or more and 95.0% by mass or less, and Sn is the balance. (3) The Cu core ball as described in (1) or (2) above, wherein the solder layer is composed of a Pb (Sn-Pb)-based solder alloy containing Sn and 37.0% by mass or more and 95.0% by mass or less, contained in the solder The concentration ratio (%) of Sn in the layer, with concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or concentration ratio (%) = (average value of measured value ( Mass %)/target content (mass %)) × 100 indicates that the concentration ratio is in the range of 70.0 to 140.0%. (4) The Cu core ball as described in (1) or (2) above, wherein the solder layer is composed of Pb (Sn-Pb)-based solder alloy containing Sn and 37.0% by mass or more and 95.0% by mass or less, contained in the solder The concentration ratio (%) of Sn in the layer, with concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100 or concentration ratio (%) = (average value of measured value (mass %)/Target content (mass%))×100 indicates that the concentration ratio is in the range of 90.0 to 110.0%. (5) The Cu core ball as described in (1) or (2) above, wherein the true sphericity is 0.98 or more. (6) The Cu core ball as described in (1) or (2) above, wherein the true sphericity is 0.99 or more. (7) The Cu core ball as described in (3) above, wherein the true sphericity is 0.99 or more. (8) The Cu core ball as described in (4) above, wherein the true sphericity is 0.99 or more. (9) The Cu core ball as described in (1) or (2) above, in which the amount of α rays is 0.0200 cph/cm ² or less. (10) The Cu core ball as described in (1) or (2) above, in which the amount of α rays is 0.0010 cph/cm ² or less. (11) The Cu core ball as described in (1) or (2) above, which has a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with a solder layer, and the true sphericity is 0.95 or more. (12) The Cu core ball as described in (3) above, 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. (13) The Cu core ball as described in (4) above, which has a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with a solder layer, and the true sphericity is 0.95 or more. (14) The Cu core ball as described in (11) above, wherein the true sphericity is 0.98 or more. (15) The Cu core ball as described in (11) above, wherein the true sphericity is 0.99 or more. (16) The Cu core ball as described in (11) above, wherein the amount of α rays is 0.0200 cph/cm ² or less. (17) The Cu core ball as described in (11) above, wherein the amount of α rays is 0.0010 cph/cm ² or less. (18) The Cu core ball as described in (1) or (2) above, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. (19) The Cu core ball as described in (11) above, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. (20) A welding head using the Cu core ball of any one of (1) to (19) above. (21) A solder paste using the Cu core ball of any one of (1) to (19) above. (22) A foam solder using the Cu core ball of any one of (1) to (19) above. [Effect of invention]

According to the present invention, it is possible to achieve high true sphericity and low hardness of Cu balls, and to suppress discoloration of Cu balls. By realizing the high sphericity of the Cu sphere, the high sphericity of the Cu core sphere covered with the metal layer can be achieved, and the self-alignment when the Cu core sphere is mounted on the electrode can be ensured, and at the same time Suppress the height error of Cu core ball. In addition, by achieving the low hardness of the Cu ball, the drop impact resistance of the Cu core ball covered with the metal layer by the metal layer can be improved. In addition, since the discoloration of the Cu ball is suppressed, the adverse effect of the sulfide or sulfur oxide on the Cu ball can be suppressed, and it is suitable for covering with a metal layer and has good wettability.

The present invention will be described in detail below. In this specification, the composition unit (ppm, ppb, and %) of the metal layer of the Cu core ball indicates the ratio to the mass of the metal layer (mass ppm, mass ppb, and mass %) unless otherwise specified. In addition, the units (ppm, ppb, and %) of the composition of the Cu balls indicate the ratio to the mass of the Cu balls (mass ppm, mass ppb, and mass %) 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: a Cu ball 1; and a 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; a layer consisting of one or more elements selected from Ni, Co, Fe, and Pd covering the surface of the Cu ball 1 The above metal layer 2; and the solder layer 3 covering the surface of the metal layer 2.

FIG. 3 shows an example of the configuration of the electronic component 60 that mounts the semiconductor wafer 10 on the 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 coated on the electrode 100 of the semiconductor wafer 10 with a flux to wet and expand the molten solder layer 3 and is mounted on the electrode 100 of the semiconductor wafer 10 . In this example, the configuration of the Cu core ball 11A or the Cu core ball 11B mounted on the electrode 100 of the semiconductor wafer 10 is referred to as the solder bump 30. The solder bumps 30 of the semiconductor wafer 10 are bonded to the electrodes 41 of the printed board 40 via the molten solder layer 3 or the solder melted with the solder paste applied to the electrodes 41. In this example, the structure in which the solder bump 30 is mounted on the electrode 41 of the printed board 40 is referred to as a solder joint 50.

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

Regarding the Cu core ball 11A according to the first embodiment of the present invention, by increasing the true sphericity of the Cu ball 1 covered with the solder layer 3, the true sphericity of the Cu core ball 11A can be improved. In addition, with regard to the Cu core ball 11B of the second embodiment of the present invention, by increasing the true sphericity of the Cu ball 1 covered with the metal layer 2 and the solder layer 3, the true sphericity of the Cu core ball 11B can be improved. Hereinafter, a preferred aspect of the Cu ball 1 constituting the Cu core balls 11A and 11B will be described.

‧Cusphericity of Cu balls: 0.95 or more In the present invention, the true degree of sphericity means the deviation from the true sphere. The true sphericity is the arithmetic average calculated when the diameters of 500 Cu balls are divided by the quotient of the long diameter. The closer the value is to the upper limit of 1.00, the closer to the true ball. The true sphericity can be 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). Get. The length of the major axis and the length of the diameter of the present invention are measured by the ULTRA Quick Vision, ULTRA QV350-PRO measuring device manufactured by Mitutoyo Corporation.

From the viewpoint of maintaining an appropriate space between the substrates, the Cu ball 1 has a true sphericity of 0.95 or more, a true sphericity of 0.98 or more, and more preferably 0.99 or more. When the true sphericity of the Cu ball 1 is less than 0.95, the Cu ball 1 becomes indefinite, and bumps of uneven height are formed when the bumps are formed, thereby increasing the possibility of occurrence of joint failure. If the true sphericity is 0.95 or more, since the Cu ball 1 does not melt at the welding temperature, the height error at the welding head 50 can be suppressed. With this, it is possible to surely prevent the joint failure of the semiconductor wafer 10 and the printed board 40.

‧Purity of Cu balls: 99.995% by mass or more and 99.9995% by mass or less In general, Cu with low purity has a higher degree of sphericity because it is more capable of securing an impurity element that can become the nucleus of the Cu sphere 1 in Cu than Cu with higher purity. On the other hand, the Cu ball 1 with low purity deteriorates the electrical conductivity and thermal conductivity.

Therefore, if the purity of the Cu sphere 1 is 99.995 mass% (4N5) or more and 99.9995 mass% (5N5) or less, sufficient sphericity can be ensured. In addition, if the purity of the Cu ball 1 is 4N5 or more and 5N5 or less, in addition to sufficiently reducing the amount of α rays, the deterioration of the electrical conductivity and thermal conductivity of the Cu ball 1 due to the decrease in purity can be suppressed.

When manufacturing the Cu ball 1, a Cu material, which is an example of a small piece of metal material formed in a predetermined shape, is melted by heating, and the molten Cu becomes spherical due to surface tension, and this rapid condensation solidifies the Cu ball 1. In the process of solidification of molten Cu from a liquid state, crystal grains will grow in spherical molten Cu. At this time, if there are many impurity elements, the impurity elements will become crystal nuclei and suppress the growth of crystal grains. Therefore, the spherical molten Cu becomes Cu balls 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 crystal nuclei, and the growth of crystal grains cannot be suppressed and the growth is directional. As a result, a part of the surface of the spherical molten Cu will protrude and solidify, reducing the true sphericity. As the impurity element, Fe, Ag, Ni, P, S, Sb, Bi, Zn, A1, As, Cd, Pb, In, Sn, Au, U, Th, etc. may be considered.

The following describes the content of impurities that determine the purity and true sphericity of Cu balls 1.

‧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 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 kind is preferably 5.0 mass ppm or more and 50.0 mass ppm or less, and when two or more kinds of Fe, Ag and Ni are contained, two or more kinds The total content of is preferably 5.0 mass ppm or more and 50.0 mass ppm or less. Fe, Ag, and Ni become crystal nuclei during melting in the manufacturing process of the Cu ball 1, and therefore a certain amount of Fe, Ag, or Ni is contained in Cu, so that the Cu ball 1 with high sphericity can be manufactured. Therefore, at least one of Fe, Ag, and Ni is an important element for estimating the content of impurity elements. In addition, by setting the total content of at least one of Fe, Ag, and Ni to 5.0 mass ppm or more and 50.0 mass ppm or less, in addition to suppressing the discoloration of the Cu ball 1, even if the Cu ball 1 is not slowly heated The annealing step of slowly recrystallizing the Cu balls 1 by Xu Leng can also achieve the desired Vickers hardness.

‧S content is 0 mass ppm or more and 1.0 mass ppm or less The Cu balls 1 containing a certain amount of S form sulfides or sulfur oxides when heated and are easily discolored, and the wettability decreases. Therefore, the content of S needs to be 0 mass ppm or more and 1.0 mass ppm or less. The more Cu balls 1 forming sulfide and sulfur oxides, the brighter the surface of the Cu balls becomes darker. Therefore, as will be described in detail later, as long as the result of measuring the brightness of the surface of the Cu ball is below a predetermined value, it can be judged that the formation of sulfides and sulfur oxides is suppressed and the wettability is good.

‧P content is 0 mass ppm or more and less than 3.0 mass ppm P can become phosphoric acid or Cu complex, which may adversely affect the Cu ball 1 in some cases. In addition, since the Cu ball 1 containing a certain amount of P has a higher hardness, the content of P is preferably 0 mass ppm or more and less than 3.0 mass ppm, and more preferably less than 1.0 mass ppm.

‧Other impurity elements The content of impurity elements such as Sb, Bi, Zn, A1, As, Cd, Pb, In, Sn, Au, etc. (hereinafter, referred to as "other impurity elements") other than the impurity elements contained in the Cu ball 1, respectively It is preferably 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, since the Cu ball 1 cannot prevent elements other than Fe, Ag, and Ni from being mixed in with the current technology, 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, it is not easy to show the effect or influence of adding each element. In addition, when analyzing the elements contained in the Cu ball, when the content of the impurity element is less than 1 mass ppm, this value is below the sensing limit of the analyzer. 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 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 the content of other impurity elements is less than 1 ppm, the purity of the 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 55.5 HV or less. When the Vickers hardness is large, the durability against external stress becomes low, the drop impact resistance becomes poor, and cracks easily occur. In addition, when an auxiliary force such as pressurization is applied to the three-dimensionally structured bumps or when forming the joint, if a hard Cu ball is used, there is a possibility that the electrode crushes or the like. In addition, when the Vickers hardness of the Cu ball 1 is large, the crystal grains become smaller than a certain range or more, which may cause deterioration in conductivity. When the Vickers hardness of the Cu ball 1 is 55.5 HV or less, the drop resistance is good, cracks can be suppressed, electrode crushing, etc. can be suppressed, and further the deterioration of conductivity can be suppressed. In this embodiment, the lower limit of the Vickers hardness may exceed 0 HV, preferably 20 HV or more.

‧The amount of α ray of Cu ball: 0.0200cph/cm ² In order to make the amount of α ray in the high-density structure of electronic parts will not cause soft errors to the extent, the α ray of Cu ball 1 is 0.0200cph/cm ² or less good. α-ray dose from the package as further suppress soft errors in view of a high density, it is preferably 0.0100cph / cm ² or less, more preferably is 0.0050cph / cm ² or less, more preferably is 0.0020cph / cm ² Below, the best is 0.0010cph/cm ² or less. In order to suppress soft errors caused by α rays, the content of radioisotopes such as U and Th is preferably less than 5 mass ppb.

‧Discoloration resistance: Brightness above 55 The Cu ball 1 preferably has a brightness of 55 or more. The L* value of the so-called lightness system L*a*b color system. Since the brightness of the Cu balls 1 in which sulfides or sulfur oxides derived from S are formed on the surface becomes low, if the brightness is 55 or more, it can be said that the sulfides and sulfur oxides are suppressed. In addition, Cu balls 1 having a brightness of 55 or more have good wettability during assembly. In contrast, when the brightness of the Cu ball 1 is less than 55 or less, it can be said that the Cu ball 1 does not sufficiently suppress the formation of sulfides and sulfur oxides. Sulfide or sulfur oxides, in addition to adversely affecting the Cu balls 1, deteriorate the wettability when the Cu balls 1 are directly bonded to the electrodes. When the wettability deteriorates, non-wetting or deterioration of self-alignment occurs.

‧Cu ball diameter: 1μm or more and 1000μm or less The diameter of the Cu ball 1 is preferably 1 μm or more and 1000 μm or less, and more preferably 50 μm or more and 300 μm. Within this range, the spherical Cu balls 1 can be stably manufactured, and the connection short circuit can be suppressed when the terminals have a narrow pitch. Here, for example, when the Cu ball 1 is used as a paste, the “Cu ball” may also be referred to as “Cu powder”. When "Cu ball" is used for "Cu powder", the diameter of the Cu ball is generally 1 to 300 μm.

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

‧Solder layer The Cu core balls 11A and 11B of the embodiments of the present invention cover the Cu balls 1 with a solder layer 3 of a solder alloy containing Sn and Pb as essential elements. In particular, regarding the Cu core balls 11A and 11B of each embodiment of the present invention, a Cu core ball in which the Pb distribution in the solder layer 3 is uniform is provided, and a solder joint, solder paste, and foam solder using the same.

The composition of the solder layer 3 according to the embodiment of the present invention is composed of (Sn-Pb) alloy containing Sn and Pb. Regarding the content of Pb, the Pb content of the entire alloy is in the range of 0% by mass or more and 95.0% by mass or less. If the Pb content is in the range of 0% by mass or more and 95.0% by mass or less, the Pb concentration ratio can be suppressed within a predetermined range Inside. Here, the distribution of Pb in the solder layer 3 is homogeneous, and the distribution of Sn is also homogeneous. Similarly, the Sn distribution in the solder layer 3 is homogeneous, and the Pb distribution is also homogeneous. In the present invention, there is a composition example in which the content of Pb is larger than that of Sn. Considering such a case, in the following description, the distribution of Sn is homogeneous, and the distribution of Pb is homogeneous.

The amount of Pb is in the range of 37.0-95.0% by mass for the entire alloy, that is, the range of Sn for the entire alloy is in the range of 5.0-63.0% by mass, then the Sn concentration ratio can be controlled within a predetermined range of 70.0-140.0%, which can make the solder The distribution of Sn and Pb in layer 3 is homogeneous.

For example, when the target value of Pb content is 95.0 mass% and the target value of Sn content is 5.0 mass%, the allowable range of Sn content and concentration ratio is 3.61 mass% (concentration ratio 72.2%) to 6.88 mass% (concentration ratio 137.6 %), the concentration ratio of Sn can be controlled within a predetermined range of 70.0 to 140.0%, and the distribution of Sn and Pb in the solder layer 3 can be made uniform.

In addition, when the target value of the Pb content is 90.0 mass% and the target value of the Sn content is 10.0 mass%, the allowable range of the Sn content and the concentration ratio is 9.74 mass% (concentration ratio 97.4%) to 11.20 mass% (concentration ratio 112.0 %), the concentration ratio of Sn can be controlled within a predetermined range of 70.0 to 140.0%, and the distribution of Sn and Pb in the solder layer 3 can be made uniform.

Furthermore, when the target value of Pb content is 37.0 mass% and the target value of Sn content is 63.0 mass%, the allowable range of Sn content and concentration ratio is 61.30 mass% (concentration ratio 97.3%) to 70.02 mass% (concentration ratio 111.1%), the concentration ratio of Sn can be controlled within a predetermined range of 70.0 to 140.0%, and the distribution of Sn and Pb in the solder layer 3 can be made uniform.

In addition, when the target value of Pb content is 37.0 mass% and the target value of Sn content is 60.0 mass%, the allowable range of Sn content and concentration ratio is 55.83 mass% (concentration ratio 93.1%) to 63.10 mass% (concentration ratio 105.2 %), the concentration ratio of Sn can be controlled within a predetermined range of 70.0-140.0%, and the distribution of Sn and Pb in the solder layer 3 can be made uniform.

In addition, the allowable range refers to a range in which soldering such as bump formation can be performed without problems as long as it is within this range. In addition, the concentration ratio (%) refers to the ratio (%) of the measured value (mass %) to the target content (mass %), or the average value of the measured value (mass %) to the target content (mass %). That is, the concentration ratio (%) can be calculated as the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100 or the concentration ratio (%) = (average value of measured values (mass %)/Target content (mass %))×100.

The concentration ratio of Sn and Pb is more preferably in the range of 90.0 to 110.0%. In addition, in the solder layer 3 composed of Sn and Pb, even if other additive elements are added, the concentration ratio of Sn and Pb can be controlled within a predetermined range of 70.0 to 140.0, more preferably 90.0 to 110.0% .

As the additional element, one or two or more of Ag, Ni, Ge, Ga, In, Zn, Fe, Bi, Sb, Au, Pd, Co, etc. may be used.

As described above, the content of Sn and Pb in the solder layer 3 is 5.0% by mass of the target value of Sn, and the allowable range is 3.61% by mass (concentration ratio 72.2%) to 6.88% by mass (concentration ratio 137.6%). good. In addition, as the allowable range for the target value of Sn of 10.0% by mass, it is preferably about 9.74% by mass (concentration ratio 97.4%) to 11.20% by mass (concentration ratio 112.0%). In addition, as the allowable range for the target value of Sn of 63.0% by mass, it is preferably about 61.30% by mass (concentration ratio 97.3%) to 70.02% by mass (concentration ratio 111.1%). In addition, as the allowable range of the target value of Sn of 60.0% by mass, it is preferably 55.83% by mass (concentration ratio 93.1%) to 63.10% by mass (concentration ratio 105.2%).

Although the thickness of the solder layer 3 varies depending on the particle size of the Cu balls 1, in order to ensure a sufficient solder bonding amount, it is preferable that the single side in the radial direction is 100 μm or less. The solder layer can be formed by an electroplating method or a hot-dip plating method, but in order to suppress the decrease in the true sphericity of the Cu core ball, it is preferable to form the electroplating method.

In order to form a solder layer with a uniform concentration distribution of Sn and Pb, by applying a predetermined DC voltage between the anode electrode and the cathode electrode, while shaking the Cu ball, the Pb concentration in the liquid is adjusted to be uniform and electroplated. When forming the solder plating layer, the concentration of the plating solution is controlled to be fixed.

In the process of forming the solder plating layer, the concentration of the plating solution is controlled to a fixed electroplating process to generate the solder layer 3, and the thickness of the solder layer 3 is monitored one by one. In this example, the thickness of the solder layer 3 is sequentially increased by a predetermined value of Cu The nuclear ball is collected as a sample each time. After the collected sample was washed and dried, the particle size was measured.

Sequentially measure the particle size of the Cu core ball at the timing of measurement, and the Pb content of the solder layer at the target value, even if the solder layer only needs to increase the predetermined thickness, the Pb content at this time can be found to be approximately the same value as the previous content . Therefore, the concentration distribution of Pb is homogeneous (equal) to the thickness of the plating layer, and it is understandable that there is no concentration gradient. As mentioned above, the film thickness can be controlled to be uniform, but the concentration will be uneven plating. By controlling the Pb concentration in the solder layer and controlling the Pb concentration ratio within a predetermined range, Pb with a solder layer can be obtained Homogeneously distributed Cu core balls.

Furthermore, when the Pb content is greater than Sn, in order to form a solder layer with a uniform concentration distribution of Sn and Pb, a predetermined DC voltage is applied between the anode electrode and the cathode electrode, while shaking the Cu ball, the concentration of Pb in the liquid Leveling is performed for electroplating, and the concentration of the plating solution is controlled to be fixed when the solder plating is formed.

In order to measure the particle size of the Cu core ball at the timing of measurement, when the Sn content of the solder layer is at the target value, even if the solder layer only needs to increase by a predetermined thickness, the Sn content at this time is almost the same as the previous content Value. Therefore, the concentration distribution of Sn is homogeneous (equal) to the thickness of the plating layer, and it is understandable that there is no concentration gradient. As above, the thickness of the film can be controlled to be uniform, but the problem of electroplating where the concentration will be heterogeneous, by controlling the Sn concentration in the solder layer, to make the Sn concentration ratio within a predetermined range, Sn with a solder layer can be obtained Homogeneously distributed Cu core balls.

Fig. 4 is an enlarged cross-sectional view of a Cu core ball. FIG. 4 shows a Cu core ball 11B that covers the Cu ball 1 with the metal layer 2 and covers the metal layer 2 with the solder layer 3. As is apparent from FIG. 4, the solder layer 3 is a step in which Sn and Pb are homogeneously mixed and grown.

In addition, the crystal grains become larger as the outermost surface of the solder layer 3 covering the Cu core balls 11A and 11B becomes closer to a single metal, so the true sphericity of the Cu core balls tends to decrease. On the other hand, since Sn and Pb in the solder layer are in a substantially uniformly 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 smaller. As a result, the Cu core ball has a high degree of sphericity, which is 0.99 or more. When the Cu core ball has a true sphericity of 0.95 or more, when the Cu core ball is mounted on an electrode for reflow soldering, positional deviation caused by the Cu core ball can be suppressed, and self-alignment can be improved.

From the viewpoint that the concentration of Sn and Pb in the solder layer maintains approximately the same state even if the thickness of the solder layer grows, it can be seen that Sn and Pb in the solder layer grow in a substantially uniformly distributed state. In a state where the Sn and Pb concentrations in the plating solution are homogenized, the Sn and Pb concentrations are kept within a desired value, and the plating process is performed. In this example, the Sn content in the solder layer is 5.0% by mass, 10.0% by mass, 60.0% by mass, or 63.0% by mass as the target value, so the Sn concentration in the plating solution is controlled to achieve the target value.

In order to bring the Sn and Pb concentration distribution in the solder layer into the desired value, plating is performed while controlling the voltage and current. With such a plating process, the distribution of Sn and Pb in the solder layer can be maintained at a desired value.

The Cu core balls 11A and 11B can also be formed of low α-ray Cu core balls 11A and 11B by using a solder alloy with a low α-ray amount in the solder layer 3.

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

‧Metal layer The metal layer 2 is composed of, for example, a Ni plating layer, a Co plating layer, an Fe plating layer, a Pd plating layer, or a plating layer (single layer or plural layers) containing two or more elements of Ni, Co, Fe, and Pd. When the Cu core ball 11B is used as a solder bump, the metal layer 2 does not melt and remains at the soldering temperature, but contributes to the height of the solder joint. Therefore, it is configured to have a high sphericity and a small diameter error. In addition, from the viewpoint of suppressing soft errors, it is configured to have a low α-ray dose.

‧Composition and thickness of metal layer When the composition of the metal layer 2 is composed of a single Ni, Co, Fe, or Pd, in addition to inevitable impurities, Ni, Co, Fe, and Pd are 100%. In addition, the metal used for the metal layer 2 is not limited to a single metal, and an alloy of two or more elements in combination of Ni, Co, Fe, or Pd may also be used. In addition, the metal layer 2 may be composed of a single layer composed of a single layer of Ni, Co, Fe, or Pd, and a plurality of layers composed of an alloy of two or more elements combined from Ni, Co, Fe, or Pd. The film thickness T2 of the metal layer 2 is, for example, 1 μm to 20 μm.

‧Α-ray dose of Cu core ball: 0.0200 cph/cm ² or less The α-ray dose of Cu core ball 11A in the first embodiment and Cu core ball 11B in the second embodiment is 0.0200 cph/cm ² or less good. This is the amount of alpha rays to the extent that high-density packaging of electronic parts does not make soft errors a problem. 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, the Cu core ball 11A according to the first embodiment of the present invention is covered with such a solder layer 3, and therefore shows 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 by the α-ray amount of the metal layer 2 and the solder layer 3 constituting the Cu core ball 11B being 0.0200 cph/cm ² or less. Therefore, the Cu core ball 11B according to the second embodiment of the present invention is covered with such a metal layer 2 and a solder layer 3, and therefore shows a low amount of α rays. α-ray dose, suppressing the package as a soft error in the viewpoint of a higher density, is preferably 0.0100cph / cm ² or less, more preferably is 0.0050cph / cm ² or less, more preferably is 0.0020cph / cm ² Below, the best is 0.0010cph/cm ² or less. In order to make the amount of α rays of the Cu ball 1 to be 0.0200 cph/cm ² or less, the U and Th contents of the metal layer 2 and the solder layer 3 are respectively 5 ppb or less. In addition, from the viewpoint of suppressing soft errors in the present or future high-density packaging, the contents of U and Th are preferably 2 ppb or less, respectively.

‧Sphericality of Cu core ball: 0.95 or more The Cu core ball 11A of the first embodiment of the present invention covering the Cu ball 1 with the solder layer 3 and the Cu core ball 11B of the second embodiment of the present invention covering the Cu ball 1 with the metal layer 2 and the solder layer 3 The true sphericity is preferably 0.95 or more, the true sphericity is more preferably 0.98 or more, and further preferably 0.99 or more. If the true sphericity of Cu core balls 11A and 11B is less than 0.95, the Cu core balls 11A and 11B will become indefinite in shape. When the Cu core balls 11A and 11B are placed on the electrodes for reflow, the Cu core balls 11A , 11B's position shift, and self-alignment will also deteriorate. When the Cu core balls 11A and 11B have a true sphericity of 0.95 or more, the self-alignment when the Cu core balls 11A and 11B are mounted on the electrode 100 of the semiconductor wafer 10 or the like can be ensured. Then, by setting the Cu sphere 1 to a true sphericity of 0.95 or more, the Cu spheres 11A and 11B do not melt the Cu sphere 1 and the metal layer 2 at the welding temperature, so that the height error of the welding head 50 can be suppressed. With this, it is possible to surely prevent the joint failure of the semiconductor wafer 10 and the printed board 40.

‧The barrier function of the metal layer During reflow, the Cu of the Cu ball diffuses into the solder (paste) used to join the Cu core ball and the electrode, and a large amount of hard and brittle Cu _{6 is} formed in the solder layer and the connection interface The intermetallic compounds of Sn ₅ and Cu ₃ Sn may become severely cracked when impacted, and may damage the connection. Therefore, in order to obtain sufficient connection strength, it is preferable to suppress (block) the diffusion of Cu from the Cu ball 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 Cu of the Cu ball 1 from diffusing into the solder paste.

‧Solder paste, foam solder, solder joint In addition, the solder paste may be constituted by including Cu core balls 11A or Cu core balls 11B in the solder. By dispersing the Cu core ball 11A or the Cu core ball 11B in the solder, a foam solder can be constituted. The Cu core ball 11A or the Cu core ball 11B can also be used to form a welded joint between bonding electrodes.

‧Cu ball manufacturing method Next, an example of a method of manufacturing Cu balls 1 will be described. As an example of a metal material, Cu material is placed on a heat-resistant plate such as ceramic (hereinafter referred to as "heat-resistant plate"), and heated together with the heat-resistant plate in a furnace. The heat-resistant plate is provided with a plurality of circular grooves whose bottoms are hemispherical. 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, small pieces of Cu material obtained by cutting Cu thin wires are put into the grooves of the heat-resistant plate one by one. A heat-resistant plate of Cu material was put into the trench, 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, if the temperature in the furnace is above the melting point of Cu, the Cu material will melt into a spherical shape. After that, it is cooled in the furnace, and is formed by rapidly cooling the Cu balls 1 in the grooves of the heat-resistant plate.

In addition, as another method, there is a spray method in which molten Cu is dropped through a small hole provided at the bottom of the crucible, and the droplet is quenched to room temperature (for example, 25° C.) to pelletize the Cu ball 1, or the Cu is cut with a thermal plasma. A method of making balls by heating metal to above 1000°C.

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

As the Cu material that is the raw material of the Cu ball 1, for example, a block material, a wire material, a plate material, or the like can be used. The purity of the Cu material may be more than 4N5 and 6N or less from the viewpoint of not excessively reducing the purity of the Cu ball 1.

When using a high-purity Cu material in this way, the holding temperature of molten Cu may be reduced to about 1000° C. as before, without performing the above-mentioned heat treatment. In this way, the above heat treatment can be appropriately omitted or changed according to the purity of the Cu material and the amount of α rays. In addition, when a Cu ball 1 having a high α-ray amount or a shaped Cu ball 1 is manufactured, these Cu balls 1 may be reused as a raw material to reduce the α-ray amount.

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

As a method of forming the metal layer 2 on the Cu ball 1, a conventional plating method or the like can be used. For example, when forming the Ni plating layer, adjust the Ni plating solution using a Ni metal block or a Ni metal salt for the Ni plating bath, and immerse the Cu ball 1 in the adjusted Ni plating solution by precipitation on the surface of the Cu ball 1 Ni plating is formed. 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 also be used. When the solder layer 3 of Sn alloy is formed on the surface of the metal layer 2, the above-mentioned plating method or electroless plating method can be used. [Example]

The following describes embodiments of the present invention, but the present invention should not be limited to these. The Cu spheres of Examples 1 to 19 and Comparative Examples 1 to 12 were prepared with the compositions shown in Tables 1 and 2 below, and the sphericity, Vickers hardness, α-ray amount, and discoloration resistance of the Cu spheres were measured.

In addition, the Cu balls of the above Examples 1 to 19 were covered with the solder layers of the solder alloys of Composition Examples 1 to 4 shown in Table 3 to prepare the Cu core balls of Examples 1A to 19A, and the true sphericity of the Cu core balls was measured . Furthermore, the Cu spheres of the above Examples 1-19 were covered with the metal layer and the solder layer of the solder alloy of the composition examples 1-4 shown in Table 4 to prepare the Cu core balls of Examples 1B-19B, and the Cu cores were measured The true degree of the ball.

In addition, the Cu balls of the above Comparative Examples 1 to 12 were covered with the solder layers of the solder alloys of Composition Examples 1 to 4 shown in Table 5 to prepare Cu core balls of Comparative Examples 1A to 12A, and the true sphericity of the Cu core balls was measured . In addition, the Cu balls of the above Comparative Examples 1 to 12 were covered with a metal layer and the solder layers of the solder alloys of Composition Examples 1 to 4 shown in Table 6 to prepare Cu core balls of Comparative Examples 1B to 12B, and the Cu core balls were measured True sphericity.

In the following table, there is no unit number, which means mass ppm or mass ppb. Specifically, the numerical values in the table indicating the content ratios of Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, and Au represent mass ppm. ">1" means that the content ratio of the impurity element to the Cu ball is less than 1 mass ppm. In addition, the values in the table showing the content ratio of U and Th represent the mass ppb. ">5" means that the content ratio of the impurity element to the Cu ball is less than 5 mass ppb. "Total Impurity" means the total proportion of impurity elements contained in Cu balls.

‧Cu ball production The production conditions of Cu balls were studied. As an example of a metal material, Cu material is prepared as a bulk material. The Cu materials of 6N purity were used as Examples 1 to 13, 19, and Comparative Examples 1 to 12, and the Cu materials of 5N purity were used as Examples 14 to 18. After putting each Cu material into the crucible, the temperature of the crucible was raised to 1200°C, heated for 45 minutes to melt the Cu material, the molten Cu was dripped from the hole provided at the bottom of the crucible, and the generated droplets were quickly cooled to room temperature (18 ℃) Pellets into Cu balls. With this, Cu spheres having an average particle diameter of the values shown in the following tables were produced. Elemental analysis, using inductively coupled plasma mass spectrometry (ICP-MS analysis) or glow discharge mass spectrometry (GD-MS analysis) enables high-precision analysis, but in this case ICP-MS analysis was used. The ball diameters of Cu balls were 250 μm in Examples 1 to 19 and Comparative Examples 1 to 12.

‧Cu core ball production Regarding Examples 1A to 19A, using the Cu balls of Examples 1 to 19 above, the solder alloys of Examples 1 to 4 were electroplated to form a solder layer with a thickness of 23 μm on one side to produce Cu core balls of Examples 1A to 19A. .

In addition, regarding Examples 1B to 19B, the Cu balls of the above Examples 1 to 19 were used to form a Ni plating layer with a thickness of 2 μm on one side as a metal layer, and the solder alloy of Composition Examples 1 to 4 was further formed with a single thickness by electroplating 23 μm solder layer production examples 1B to 19B.

Furthermore, using the Cu balls of Comparative Examples 1 to 12 above, the solder alloys of Composition Examples 1 to 4 were used to form a solder layer with a thickness of 23 μm on one side, to produce Cu core balls of Comparative Examples 1A to 12A. In addition, using the Cu balls of the above Comparative Examples 1-12, a Ni plating layer was formed as a metal layer with a thickness of 2 μm on one side, and the solder alloy of Composition Examples 1-4 was further formed into a solder layer with a thickness of 23 μm on one side. Production Example Comparative Example 1B ~12B Cu core ball.

Each evaluation method of the true sphericity of Cu balls and Cu core balls, the α-ray amount of Cu balls, Vickers hardness, and discoloration resistance will be described in detail below.

‧Sphericality The true sphericity of Cu spheres and Cu core spheres is measured by CNC image measuring system. The device is ULTRA QUICK VISION, ULTRA QV350-PRO manufactured by MITSUTOYO.

[Evaluation criteria of true sphericity] In the following tables, the evaluation criteria for the sphericity of Cu balls and Cu core balls are as follows. ○○○: Sphericality is 0.99 or more ○○: Sphericality is 0.98 or more and less than 0.99 ○: The true sphericity is 0.95 or more and less than 0.98 ╳: The true sphericity is less than 0.95

‧Vickers hardness The Vickers hardness of the Cu ball is measured in accordance with "Vickers hardness test-test method JIS Z2244". The device uses a micro Vickers hardness tester made by Akashi, AKASHI micro hardness tester MVK-F 1200l-Q.

[Vickers hardness evaluation criteria] 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 ╳: More than 55.5HV

‧Α-ray amount The method of measuring the α-ray amount of Cu balls is as follows. For the measurement of the amount of α rays, an α-ray measuring device of a ventilation ratio counter was used. The measurement sample is covered with Cu balls on a flat shallow bottom container of 300 mm×300 mm so that the bottom of the container cannot be seen. This measurement sample was placed in an α-ray measuring apparatus, and after being left under PR-10 ventilation for 24 hours, the amount of α-ray was measured.

[Evaluation Criteria of α-Ray Quantity] In the following tables, the evaluation criteria of the α-ray quantity of Cu balls are as follows. ○: The amount of α rays is 0.0200cph/cm ² or less╳: The amount of α rays exceeds 0.0200cph/cm ²

In addition, the PR-10 gas (90% argon-10% methane) used for measurement is filled with PR-10 gas for more than 3 weeks. The use of gas cylinders for more than 3 weeks is to comply with JEDEC STANDARD-Alpha Radiation Measurement prescribed by JEDEC (Joint Electron Device Engineering Council) in order to prevent radon in the atmosphere from entering the gas cylinder to generate alpha rays. in Electronic Materials JESD221.

‧Discoloration resistance In order to measure the discoloration resistance of Cu balls, the Cu balls were heated in a constant temperature bath at 200° C. for 420 seconds in an atmospheric atmosphere, the change in lightness was measured, and it was evaluated whether the Cu balls were sufficiently resistant to changes with time. Brightness, using Konica Minolta CM-3500d spectrophotometer, D65 light source, 10∘ field of view, in accordance with JIS Z 8722 "Color measurement method-reflection and penetrating object color", to measure the spectral transmittance, Obtained from the color values (L*, a*, b*). Furthermore, (L*,a*,b*) is in accordance with JIS Z 8729 "Color Representation-L*a*b* Color System and L*u*v* Color System". L* is lightness, a* is redness, b* is yellowness.

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

‧Overview In the above evaluation methods and evaluation criteria, Cu balls having all sphericity, Vickers hardness, α-ray amount, and discoloration resistance were ○, ○○, or ○○○, and the overall evaluation was ○. On the other hand, a Cu ball having any one of true sphericity, Vickers hardness, α-ray amount, and discoloration resistance as ╳ is comprehensively evaluated as ╳.

In addition, in the above evaluation method and evaluation criteria, Cu core balls with a true sphericity of ○, ○○, or ○○○, together with the evaluation of Cu balls, were evaluated as ○. On the other hand, the Cu core ball with a true sphericity of ╳ is evaluated as ╳ in a comprehensive evaluation. In addition, even in the evaluation of the Cu core ball, the true sphericity is ○, ○○, or ○○○, and in the evaluation of the Cu ball, any one of the true sphericity, Vickers hardness, α-ray amount, and discoloration resistance is ╳Cu core ball is ╳ in comprehensive evaluation.

In addition, the Vickers hardness of the Cu core ball depends on the Ni plating layer which is an example of the solder layer and the metal layer, so the Vickers hardness of the Cu core ball is not evaluated. However, in the Cu core ball, as long as the Vickers hardness of the Cu ball is within the range specified by the present invention, even the Cu core ball has good resistance to falling and impact, which can suppress cracks and suppress electrode crushing. Also, the deterioration of conductivity can be suppressed.

On the other hand, when the V core hardness of the Cu core ball and the Cu ball is larger than the range specified by the present invention, the durability against external stress becomes lower, the drop resistance is deteriorated, and it becomes easier The problem of cracks.

Therefore, the Cu core balls using the Cu balls of Comparative Examples 8 to 11 whose Vickers hardness exceeds 55.5 HV are not suitable for the evaluation of Vickers hardness, so the comprehensive evaluation is ╳.

In addition, 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, and therefore the discoloration resistance of the Cu core ball is not evaluated. However, as long as the brightness of the Cu ball is within the range specified by the present invention, the sulfide or sulfur oxide on the surface of the Cu ball can be suppressed, so it is suitable to be covered 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 sulfide or sulfur oxide on the surface of the Cu ball is not suppressed, so 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 brightness after 420 seconds was less than 55 were not suitable for the evaluation of discoloration resistance, so the overall evaluation was ╳.

In addition, the amount of α rays of the Cu core ball depends on the composition of the plating solution material constituting the solder layer covering the Cu ball and each element in the composition. When an Ni plating layer which is an example of a 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 ball is the low α-ray amount prescribed by the present invention, as long as the plating solution material constituting the solder layer and the Ni plating layer uses the low α-ray amount prescribed by the present invention, the Cu core ball may also become the low α-ray prescribed by the present invention Ray volume. On the other hand, if the solder layer and the plating solution material constituting the Ni plating layer have a high α-ray amount exceeding the predetermined α-ray amount of the present invention, even if the Cu ball has the above-mentioned low α-ray amount, the Cu core ball will become more than the present invention. High alpha radiation with a prescribed alpha radiation.

In addition, when the amount of α-rays of the plating solution material constituting the solder layer and the Ni plating layer shows a slightly higher amount of α-rays than the low α-ray amount prescribed by the present invention, impurities can be removed by the above-mentioned plating process to remove α The radiation dose is reduced to the range of the low α-ray dose prescribed by the present invention.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

As shown in Table 1, the Cu balls of each example with a purity of 4N5 or more and 5N5 or less obtained good results in comprehensive evaluation. From this, it can be said that the purity of the Cu balls is preferably 4N5 or more and 5N5 or less.

Hereinafter, the details of the evaluation will be described. As in Examples 1 to 12, 18, Cu spheres with a purity of 4N5 or more and 5N5 or less, containing Fe, Ag, or Ni of 5.0 mass ppm or more and 50.0 mass ppm or less, true sphericity, The comprehensive evaluation of the Vickers hardness, the amount of α rays and the discoloration resistance yielded good results. As shown in Examples 13 to 17, 19, Cu balls with a purity of 4N5 or more and 5N5 or less, and a total of Fe, Ag, or Ni of 5.0 mass ppm or more and 50.0 mass ppm or less also have true sphericity, Vickers hardness, and α Comprehensive evaluation of the radiation dose and discoloration resistance yielded good results. In addition, although not shown in the table, from Examples 1, 18, and 19, the Fe content is 0 mass ppm or more and less than 5.0 mass ppm, the Ag content is 0 ppm or more and less than 5.0 mass ppm, and Ni Cu balls with a content of 0 mass ppm or more and less than 5.0 mass ppm, and a total of Fe, Ag, and Ni of 5.0 mass ppm or more, are also obtained in the comprehensive evaluation of true sphericity, Vickers hardness, α-ray amount, and discoloration resistance Good result.

In addition, as shown in Example 18, Sb, Bi, Zn, A1, As, Cd, Pb, In, Sn containing Fe, Ag, or Ni in a total amount of 5.0 mass ppm or more and 50.0 mass ppm or less, and other impurity elements The Cu balls of Example 18 with Au and 50.0 mass ppm or less, respectively, also obtained good results in the comprehensive evaluation of true sphericity, Vickers hardness, α-ray amount, and discoloration resistance.

Regarding the Cu core ball, as shown in Table 3 and Table 4, the solder layer of the solder alloy of Composition Example 1 containing 95.0% by mass of Pb and the balance being Sn (Sn content: 5.0% by mass) covered Example 1 ~Cu core balls of Examples 1A to 19A of the Cu balls of Example 19, the Cu balls of Examples 1 to 19 are covered with a Ni plating layer, and the solder layer of the solder alloy of Composition Example 1 is further covered by Example 1B~ The 19B Cu core ball obtained good results in the comprehensive evaluation of the true sphericity.

The solder layer of the solder alloy of Composition Example 2 containing 90.0% by mass of Pb and the balance of Sn (Sn content: 10.0% by mass) covers Examples 1A to 19A of the Cu balls of Examples 1 to 19 Cu core balls, covering the Cu balls of Examples 1 to 19 with Ni plating, and further covering the Cu core balls of Examples 1B to 19B with the solder layer of the solder alloy of Composition Example 2, obtained by comprehensive evaluation of the degree of sphericity Good result.

The solder layer of the solder alloy of Composition Example 3 containing 37.0% by mass of Pb and the balance of Sn (Sn content: 63.0% by mass) covers Examples 1A-19A of the Cu balls of Examples 1 to 19 Cu core spheres, the Cu spheres of Examples 1 to 19 are covered with Ni plating, and the Cu core spheres of Examples 1B to 19B are further covered with the solder layer of the solder alloy of Composition Example 3, the comprehensive evaluation of the true sphericity Get good results.

The solder layer of the solder alloy of Composition Example 4 containing 37.0% by mass of Pb, 3.0% by mass of Ag, and the balance of Sn (Sn content: 60.0% by mass) covers the Cu balls of Examples 1 to 19 The Cu core balls of Examples 1A to 19A, the Cu balls of Examples 1 to 19 are covered with a Ni plating, and the Cu core balls of Examples 1B to 19B are further covered with the solder layer of the solder alloy of Composition Example 4, in The comprehensive evaluation of the true sphericity yielded good results.

In addition, although 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, and the Ag content was 0 mass ppm or more and less than 5.0 mass ppm, the content of Ni is 0 mass ppm or more and less than 5.0 mass ppm, the total Cu of Fe, Ag or Ni is 5.0 mass ppm or more Cu balls, covered with the solder layer of any one of the solder alloys of Composition Example 1 to Composition Example 4 For the Cu core ball, the same Cu ball is covered with Ni plating, and the Cu core ball is further covered with the solder layer of any one of the solder alloys of Composition Example 1 to Composition Example 4. The comprehensive evaluation of the true sphericity gives good results.

On the other hand, in the Cu ball of Comparative Example 7, not only the total content of Fe, Ag, and Ni was less than 5.0 mass ppm, but U and Th were less than 5 mass ppb, and other impurity elements were less than 1 mass ppm. Comparative Example 7 Cu balls of Comparative Example 7, Cu balls of Comparative Example 7A covered with the solder layer of the solder alloy of each composition example, and Cu balls of Comparative Example 7 covered with Ni plating of the Cu balls of Comparative Example 7, further with each composition example The Cu core ball of Comparative Example 7B covered by the solder layer of the solder alloy did not have a full sphericity of 0.95. In addition, even if the impurity element contains at least one of Fe, Ag, and Ni, the total content of the Cu balls of Comparative Example 12 is less than 5.0 mass ppm, and the Cu balls of Comparative Example 12 are solder layers of the solder alloy of each composition example. The Cu core balls of Comparative Example 12A, and the Cu balls of Comparative Example 12 were covered with Ni plating, and the Cu core balls of Comparative Example 12B, which were further covered with the solder layers of the solder alloys of the respective composition examples, also had a true sphericity of less than 0.95. From these results, Cu balls with a total content of at least one content of Fe, Ag, and Ni less than 5.0 mass ppm, Cu core balls covered with Cu layers by the solder layer of the solder alloy of each composition example, and Cu balls It can be said that the Cu core ball covered with the Ni plating layer and further covered with the solder layer of the solder alloy of each composition example cannot achieve high sphericity.

In addition, in the Cu ball of Comparative Example 10, the total content of Fe, Ag, and Ni is 153.6 mass ppm, and the content of other impurity elements is 50 mass ppm or less, respectively, but the Vickers hardness exceeds 55.5 HV, and good results are not 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 greatly exceeds 50.0 mass ppm, and the Vickers hardness More than 55.5HV without good results. Therefore, even for Cu balls with a purity of 4N5 or more and 5N5 or less, Cu balls having a total content of at least one of Fe, Ag, and Ni exceeding 50.0 mass ppm increase the Vickers hardness, and it can be said that low hardness cannot be achieved. In this way, when the Vickers hardness of the Cu ball is larger than the range specified by the present invention, it cannot solve the problem that the durability against external stress becomes low, the drop impact resistance becomes poor, and cracks easily occur. Furthermore, it can be said that other impurity elements are preferably contained in a range not exceeding 50.0 mass ppm.

From these results, 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 be said to achieve high sphericity and Low hardness, and can inhibit discoloration. The Cu core ball of such a Cu ball is covered with the solder layer of the solder alloy of each composition example, and the Cu core ball is covered with the Ni plating layer, and the Cu core ball covered with the solder layer of the solder alloy of each composition example can achieve high The sphericity, in addition, by achieving the low hardness of the Cu ball, even if the Cu core ball is made, the drop impact resistance is good, cracks can be suppressed, electrode crushing, etc. can be suppressed, and deterioration in conductivity can be suppressed. Furthermore, by suppressing the discoloration of Cu balls, it is suitable to be covered with a metal layer such as a solder layer or a Ni plating layer. The content of other impurity elements is preferably 50.0 ppm by mass or less.

Although not shown in the table, Cu balls with a spherical diameter of 1 μm or more and 1000 μm or less with the same composition as those in the Examples were obtained from the comprehensive evaluation of the true sphericity, Vickers hardness, the amount of α rays and the discoloration resistance Good result. From this, it can be said that the ball diameter of the Cu ball 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 P of 2.9 mass ppm, in terms of true sphericity, Vickers hardness, α-ray amount, and discoloration resistance The comprehensive evaluation obtained good results. The Cu core ball of the Cu ball of Example 19 is covered with the solder layer of the solder alloy of each composition example, the Cu ball of Example 19 is covered with the Ni plating layer, and the Cu core ball of the solder layer of the solder alloy of each composition example is further covered The comprehensive evaluation of the true sphericity yielded good results. The total content of Fe, Ag, and Ni in the Cu ball of Comparative Example 11 is 50.0 mass ppm or less as in the Cu ball of Example 19, but the Vickers hardness exceeds 5.5 HV and results different from the Cu ball of Example 19 . In addition, in Comparative Example 9, the YVickers hardness exceeds 5.5 HV. This is considered to be because the P content in Comparative Examples 9 and 11 is significantly higher. From this result, it is understood that as the P content increases, the Vickers hardness increases. 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.

The amount of α rays of the Cu balls in each example was 0.0200 cph/cm ² or less. Therefore, on the solder alloys of Composition Example 1 and Composition Example 2 covering the Cu balls of each of Examples 1 to 19, the Cu of each of Examples 1A to 19A was adjusted to a low α-ray amount prescribed by the present invention. The nuclear ball also exhibits a low amount of α rays as prescribed by the present invention. In addition, when the Ni plating layer which is an example of the metal layer covering the Cu ball is provided, in addition to the solder alloy, each element constituting the Ni plating layer is a low α-ray amount prescribed by the present invention, and the Cu core balls of each of Examples 1B to 19B It also becomes the low α-ray amount prescribed by this invention.

Furthermore, during the plating process of forming the solder layer and the Ni plating layer, impurities including alpha rays radiated from the alloy are removed, and the amount of alpha rays of the alloy before plating shows a lower alpha ray than that specified by the present invention When the amount of α rays is slightly higher, the amount of α rays after plating can be reduced to the range of low α rays prescribed by the present invention.

Thus, when the Cu core balls of the examples are used for high-density packaging of electronic parts, by making the raw materials constituting the solder layer and the Ni plating layer a low α-ray amount prescribed by the present invention, soft errors can be suppressed.

In the Cu ball of Comparative Example 7, the results of good discoloration resistance were obtained, but in Comparative Examples 1 to 6, the results of good discoloration resistance were not obtained. Comparing the Cu balls of Comparative Examples 1 to 6 with the Cu balls of Comparative Example 7, the difference in these compositions is only the S content. Therefore, in order to obtain a good result of discoloration resistance, it can be said that the content of S needs to be less than 1 mass ppm. In the Cu balls of each example, since the S content is less than 1 mass ppm, 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., before the heating, after 60 seconds of heating, after 180 seconds, after 420 seconds After the photos, measure the brightness. Table 7 and FIG. 5 are tables showing the relationship between the time for heating each Cu ball and the brightness.

[Table 7]

From this table, comparing the brightness before heating and the brightness after 420 seconds of heating, the brightness of Example 14, Comparative Examples 1, and 5 before heating is a value near 64 or 65. After heating for 420 seconds, the brightness of Comparative Example 5 containing 30.0 mass ppm of S became the lowest, and then, in order, the comparative example 1 containing 10.0 mass ppm of S, and the S content was less than 1 mass ppm 14. From this, it can be said that the greater the content of S, the lower the brightness after heating becomes. In the Cu balls of Comparative Examples 1 and 5, since the brightness is less than 55, the Cu balls containing S exceeding 10.0 mass ppm can be said to easily form sulfides or sulfur oxides and change color when heated. In addition, if the content of S is 0 mass ppm or more and 1.0 mass ppm or less, the formation of sulfides or sulfur oxides can be suppressed, and it can be said that the wettability is good. Furthermore, the Cu balls of Example 14 were constructed on the electrode, and showed good wettability.

As described 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, and the S content is 0 mass ppm or more and 1.0 mass ppm or less, P The Cu spheres of the present example having a content of 0 mass ppm or more and less than 3.0 mass ppm have a true sphericity of 0.95 or more, so that a high true sphericity can be achieved. By realizing a high degree of sphericity, the self-alignment when the Cu core ball is mounted on the electrode can be ensured, and the height error of the Cu core ball can be suppressed. The same effect can also be obtained by covering the Cu core ball of the present embodiment with a Cu core ball covered with a solder layer, covering the Cu ball of the present embodiment with a metal layer, and further covering the Cu core ball with a solder layer on the metal layer.

In addition, the Cu balls of the present embodiment can achieve a low hardness because the Vickers hardness is 55 HV or less. By achieving a low hardness, the drop resistance of Cu balls can be improved. Due to the low hardness of the Cu ball, the Cu ball of this embodiment is covered with a solder layer, the Cu ball of this embodiment is covered with a metal layer, and the Cu core ball of the metal layer is further covered with a solder layer, which is resistant to falling The impact resistance is also good to suppress cracking, suppress electrode crushing, etc., and also suppress deterioration of conductivity.

In addition, in the Cu balls of this example, discoloration was suppressed. By suppressing the discoloration of the Cu balls, the adverse effects of sulfides or sulfur oxides on the Cu balls can be suppressed, and at the same time, the wettability when mounting the Cu balls on the electrode can be improved. Since the discoloration of Cu balls is suppressed, it is suitable to be covered with a metal layer such as a solder layer or a Ni plating layer.

In addition, in the Cu material of this embodiment, Cu blocks with a purity exceeding 4N5 and below 6N are used to produce Cu balls with a purity of above 4N5 and below 5N5, but using wire or plate material exceeding 4N5 and below 6N, in the Cu Both the ball and the Cu core ball also achieved good results in the comprehensive evaluation.

Next, the Cu core ball on the surface of the Cu ball is covered with the solder layer of the Sn-based solder alloy, and the element distribution of Sn and Pb in the solder layer will be described. As the solder layer covering the Cu balls, a solder alloy mainly composed of Sn, as shown in Japanese Patent Laid-Open No. 2007-44718 (referred to as Patent Document 4) and Japanese Patent No. 5367924 (referred to as Patent Document 5), can be used.

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

In Patent Document 4, the content of Bi contained in the solder layer is a concentration gradient plating process in which the inner side (inner peripheral side) is lighter and the outer side (outer peripheral side) is thicker.

Patent Document 5 also discloses a solder bump of a Sn-based solder alloy composed of Sn and Bi by plating a Cu film. In Patent Document 5, the content of Bi contained in the solder layer is a concentration gradient plating process that is thicker on the inner side (inner peripheral side) and lighter toward the outer side (outer peripheral side).

The technique of Patent Document 5 has a completely opposite concentration gradient from that of Patent Document 4. This is the concentration control of Patent Document 5, which is simpler than the case of Patent Document 4, and is considered to be easier to do.

As described above, when a Sn-based solder alloy in which two or more elements are added to Sn is added, and the Cu core balls coated on the surface of the Cu balls are placed on the electrode of the semiconductor wafer for reflow processing, the added elements are in the solder layer Patent documents 4 and 5 having a concentration gradient cause the following problems.

The technology disclosed in Patent Document 4 is a solder layer in which the Bi concentration is lighter on the inner peripheral side and becomes thicker on the outer peripheral side. With such a concentration gradient (the inner side is lighter and the outer side is thicker), the timing of Bi melting There may be a slight deviation between the inner peripheral side and the outer peripheral side.

When the melting timing shifts, even if the outer surface of the Cu core ball starts to melt, the region on the inner peripheral surface side has not melted, but the mixed part melts, and as a result, the position of the core material shifts slightly to the melting side. In a high-density package with a narrow pitch, this position shift may cause fatal defects in solder processing.

In Patent Document 5, the concentration gradient of Bi is opposite to that of Patent Document 1. At this time, in order to connect the semiconductor package, a heat treatment for reflow is required. When the Bi concentration of the solder layer as in Patent Document 5 is concentrated on the inner peripheral side and heated and melted in a state where the outer peripheral side is light, the Bi density on the inner peripheral side is high, and the solder starts to melt from the Bi region on the inner peripheral side. Even if the Bi region on the inner peripheral side has melted, the Bi region on the outer peripheral side has not yet begun to melt, so volume expansion of the Bi region on the inner peripheral side occurs earlier.

Due to the speed of volume expansion between the inner and outer peripheries, a pressure difference occurs between the inner and outer peripheral sides of Bi (outer air), and the outer peripheral side of Bi begins to melt. Bounce situation. Such a situation must be avoided.

In this way, Cu core balls having a solder layer composed of a Sn-based solder alloy composed of Sn and Bi, if Bi in the solder layer has a concentration gradient, defects will occur.

In recent years, Pb-free solder alloys have been widely used. On the other hand, Pb-containing solder alloys are used for specific applications such as electronic devices used in space. In this way, the core material covered with a binary or more solder alloy in which Pb is added to Sn is also considered to have a predetermined concentration gradient in the solder layer, and the same problem as Bi described above will occur.

Therefore, the operation effect regarding the uniform distribution of Pb in the solder layer 3 will be described next. In order to confirm that the concentration distribution of Pb in the solder layer 3 has a corresponding target value, the following experiment was performed. Furthermore, in the following example, the content of Sn is 5.0% by mass, and the content of Pb is 95.0% by mass, and the content of Pb is more than Sn. Therefore, the concentration distribution of Sn in the solder layer 3 corresponds to It is confirmed that the concentration distribution of Pb in the solder layer 3 has a corresponding target value. (1) Under the following conditions, a Cu core ball 11B having a composition of the solder layer 3 of Sn5 mass% and Pb95 mass% (Sn-95Pb) was produced. In the following examples, Cu balls having the composition of Example 17 shown in Table 1 were used. ‧Cu ball 1 diameter: 250μm ‧Film thickness of metal layer (Ni plating) 2: 2μm ‧Film thickness of solder layer 3: 23μm ‧Diameter of Cu core ball 11B: 300μm

In order to easily measure the experimental results, a Cu core ball having a thin solder layer was produced as the Cu core ball 11B.

The plating method is produced by electroplating. (2) As a sample, ten Cu core balls 11B forming a solder layer of a (Sn-95Pb)-based solder alloy of the same composition were prepared. These were used as Sample A. (3) Ten samples A were sealed with resin. (4) The sealed samples A were polished for each resin to observe the cross section of the samples A. Observation equipment used FE-EPMAJXA-8530F manufactured by JEOL.

FIG. 6 is an explanatory diagram showing an example of a method of measuring the concentration distribution of Sn in Cu core balls. The solder layer 3 is expediently divided into an inner layer 16a, an intermediate layer 16b, and an outer layer 16c from the surface side of the Cu ball 1. Then, the inner layer 16a is the surface of the Cu ball 1 to 9 μm, the intermediate layer 16b is 9 to 17 μm, and the outer layer 16c is 17 to 23 μm. From the inner layer 16a, the intermediate layer 16b and the outer layer 16c, as shown in FIG. 6 in this example, The inner layer region 17a, the middle region 17b, and the outer layer region 17c were cut out with a thickness of 5 μm and a width of 40 μm. Using each region as a measurement region, the Sn concentration was measured by qualitative analysis. This operation is performed for 10 views of each of the inner layer 16a, the middle layer 16b, and the outer layer 16c.

Table 8 below shows the concentration ratio of each layer obtained by measuring the Sn concentration of the inner layer, the intermediate layer, and the outer layer of the solder layer.

Table 8 shows the Sn concentration ratio when the average Sn concentration of each layer of the solder layer was measured with 10 Cu core balls in Sample A, and the target Sn content (target value) was 5 mass%.

Sample A, as described above, measured the Sn concentration of the inner layer, the middle layer, and the outer layer of 10 Cu core balls. Regarding Sample A, the measured values of Sn concentrations of the inner layer, the intermediate layer, and the outer layer of the ten Cu core balls are not shown in Table 8.

In sample A, the target Sn content (target value) was 5% by mass. At this time, the Sn concentration ratio (%) of each of the ten Cu core balls in Sample A was obtained from the measured value of Sn concentration using the following formula (1). Concentration ratio (%)=(measured value/5)×100…(1)

In addition, the average value of the Sn concentration is obtained by the following formula (2) when the number of Cu core balls as a sample is 10 pieces. The average value of Sn concentration = the sum of 10 measured values/10... (2)

In addition, when the target Sn content (target value) is 5% by mass, the concentration ratio (%) of the sample A is obtained from the average value of the measured values of Sn concentration, and is obtained by the following formula (3). Concentration ratio (%)=(average of measured values/5)×100…(3)

[Table 8]

As shown in Table 8, regarding the sample A, the average value of Sn concentration in the inner layer region 17a is 6.88% by mass, the concentration ratio is 137.6%, and the average value of Sn concentration in the intermediate layer region 17b is 6.01% by mass The concentration ratio is 120.2%, the average value of the Sn concentration in the outer layer region 17c is 3.61% by mass, and the concentration ratio is 72.2%.

In this way, the Sn concentration of the solder layer in the inner layer region 17a, the intermediate layer region 17b, and the outer layer region 17c is within the allowable range of 3.61% to 6.88% by mass, and the concentration ratio is 72.2% to 137.6%. The value of Sn concentration ratio is 70%~140%.

Then, for example, 10 Cu core balls manufactured in the same batch as those of the sample A are drawn out, respectively, and joined on the substrate by a normal reflow process. The results of joining are also shown in Table 8.

Regarding the results of the joining, the failure to measure any joint failure was determined to be "good" for all samples.

None of the inner peripheral side melted earlier than the outer peripheral side, and there was a difference in volume expansion between the inner peripheral side and the outer peripheral side, and the Cu core ball 11B was flicked, etc. In addition, the entire solder layer 3 can be melted substantially uniformly, and There is no possibility that the position of the core material is shifted due to the shift of the melting timing, so there is no risk of short-circuiting between the electrodes due to displacement or the like. Therefore, a good result was obtained in which no joint failure occurred at all, so it was judged as "good".

As described above, in the case of the (Sn-95Pb)-based solder alloy, from the results in Table 8, it can be seen that the range of 3.61 mass% (concentration ratio 72.2%) to 6.88 mass% (concentration ratio 137.6%) is acceptable.

Next, the same measurement was performed for the case where the solder layer 3 of Sn-based solder alloy composed of Sn10 mass% and Pb90 mass% (Sn-90Pb) was formed. At this time, the distribution of Sn takes 10 mass% as the target value, but the allowable range is 9.74 mass% (concentration ratio 97.4%) to 11.20 mass% (concentration ratio 112.0%). The production method of the Cu core ball is the same as in the case of the example of the sample A using the Cu core ball of the (Sn-95Pb) solder alloy described above.

The specifications of the diameters of the Cu balls and Cu core balls used, the thickness of the metal layer (Ni plating) and the solder layer, and the experimental conditions are the same as those of the sample A except for the composition of the solder layer.

The results are shown in Sample B of Table 8. At this time, the target value of Sn is 10% by mass, so as shown in sample B, 9.74~11.20% by mass (all are the average of 10 measurements of the same sample), although there are some errors (the minimum value of the average value is 9.74% by mass ( Concentration ratio 97.4%) ~ maximum 11.20 mass% (concentration ratio 112.0%)), but within the allowable range. Therefore, it can be seen that it is in the range of 9.74 mass% (concentration ratio 97.4%) to 11.20 mass% (concentration ratio 112.0%). The joint determination was the same as the sample A example, and since a good result was obtained in which joint failure did not occur at all, it was determined as "good".

The Sn content (target value) of the sample B series target was 10 (mass %). Therefore, the concentration ratio (%) of the sample B in Table 8 is obtained by the following formula (4). Concentration ratio (%)=(average value of measured value/10)×100…(4)

Next, the same measurement was performed on the solder layer 3 forming the Sn-based solder alloy composed of Sn63% by mass and Pb37% by mass (Sn-37Pb). At this time, the target value of the Sn distribution is 63% by mass, but the allowable range is 61.30% by mass (concentration ratio 97.3%) to 70.02% by mass (concentration ratio 111.1%). The production method of the Cu core ball is the same as in the case of the example of the sample A using the Cu core ball of the (Sn-95Pb) solder alloy described above.

The specifications of the diameters of the Cu balls and Cu core balls used, the thickness of the metal layer (Ni plating) and the solder layer, and the experimental conditions are the same as those of the sample A except for the composition of the solder layer.

The results are shown in Sample C of Table 8. At this time, the target value of Sn is 63% by mass, so as shown in sample C, 61.30~70.02% by mass (all are the average of 10 measurements on the same sample), although there are some errors (the minimum value of the average is 61.30% by mass ( Concentration ratio (97.3%) to a maximum of 70.02% by mass (concentration ratio of 111.1%)), but within the allowable range. Therefore, it can be seen that it is in the range of 61.30 mass% (concentration ratio 97.3%) to 70.02 mass% (concentration ratio 111.1%). The joint determination was the same as the sample A example, and since a good result was obtained in which joint failure did not occur at all, it was determined as "good".

The target Sn content (target value) of the sample C series was 63 (mass %). Therefore, the concentration ratio (%) of the sample C in Table 8 is obtained by the following formula (5). Concentration ratio (%)=(average of measured values/63)×100…(5)

Next, the same measurement was performed for the case where the solder layer 3 of Sn-based solder alloy composed of Sn60 mass%, Pb37 mass%, and Ag3 mass% (Sn-37Pb-3Ag) was formed. At this time, the target value of Sn distribution is 60 mass%, but the allowable range is 55.83 mass% (concentration ratio 93.1%) to 63.10 mass% (concentration ratio 105.2%). The production method of the Cu core ball is the same as in the case of the example of the sample A using the Cu core ball of the (Sn-95Pb) solder alloy described above.

The specifications of the diameters of the Cu balls and Cu core balls used, the thickness of the metal layer (Ni plating) and the solder layer, and the experimental conditions are the same as those of the sample A except for the composition of the solder layer.

The results are shown in Sample D in Table 8. At this time, the target value of Sn is 60% by mass, so as shown in sample D, 55.83~63.10% by mass (all are the average of 10 measurements of the same sample), although there are some errors (the minimum value of the average is 55.83% by mass ( Concentration ratio 93.1%) ~ maximum 63.10% by mass (concentration ratio 105.2%), but within the allowable range. Therefore, it can be seen that it is in the range of 55.83% by mass (concentration ratio 93.1%) to 63.10% by mass (concentration ratio 105.2%). In the example of sample A, similarly, since a good result was obtained in which no joint failure occurred at all, it was judged as "good".

The target Sn content (target value) of the sample D series was 66 (mass %). Therefore, the concentration ratio (%) of the sample D in Table 8 is obtained by the following formula (6). Concentration ratio (%)=(average of measured values/60)×100…(6)

The results of the examples of sample A, the examples of sample B, the examples of sample C, and the examples of sample D are summarized in Table 9. The concentration ratio of Sn is 72.2 to 137.6, which is mass%. Here, the sphericity of the Cu core spheres produced in the examples of sample A, the examples of sample B, the examples of sample C, and the examples of sample D were measured, and the results were all 0.99 or more and satisfies 0.95 or more.

[Table 9]

The concentration ratio (%) in Table 9 is obtained by the following formula (5). Concentration ratio (%)=(measured value/target value)×100…(5)

In addition, when the Sn concentration in the solder layer 3 is changed, phenomena such as positional deviation or blow-off of the Cu core ball 11B occur.

As described above, in each of Examples A to D, since Sn in the solder layer is homogeneous, Pb of the solder layer is homogeneous, and the film thickness of the solder layer includes the inner and outer peripheral sides of Sn and Pb on the In the whole area, the Sn and Pb concentration ratio is within a predetermined range. Therefore, Sn and Pb in the solder layer are homogeneous Cu core balls of the present invention, the inner peripheral side does not melt earlier than the outer peripheral side, but the difference in volume expansion occurs between the inner peripheral side and the outer peripheral side, and the Cu core ball is bounced Fly and so on.

In addition, since the Sn and Pb of the solder layer are homogeneous, and the Cu core ball can be melted substantially uniformly over the entire surface, there is almost no time difference in the timing of melting in the solder layer. As a result, since the positional deviation of the Cu core ball due to the deviation of the melting timing does not occur, there is no risk of short-circuiting between the electrodes due to the positional deviation or the like. Therefore, high-quality solder joints can be provided by using this Cu core ball.

1‧‧‧Cu ball 11A, 11B‧‧‧Cu core ball 2‧‧‧Metal layer 3‧‧‧ solder layer 10‧‧‧Semiconductor chip 100、41‧‧‧electrode 30‧‧‧Solder bump 40‧‧‧ printed circuit board 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. 2 is a diagram showing a Cu core ball according to a second embodiment of the present invention. 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 an enlarged cross-sectional view of a Cu core ball. FIG. 5 is a graph showing the relationship between the heating time and the brightness of the Cu balls of Examples and Comparative Examples heated at 200°C. 6 is an explanatory diagram showing an example of a method of measuring the Cu concentration distribution of Cu core balls.

1‧‧‧Cu ball

3‧‧‧ solder layer

11A‧‧‧Cu nuclear ball

Claims (22)

A Cu core ball with: Cu balls; and The solder layer covering the surface of the Cu ball, The above Cu ball is 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 content of S is 0 mass ppm or more and 1.0 mass ppm or less, The content of P is 0 mass ppm or more and less than 3.0 mass ppm, The balance is Cu and other impurity elements. The purity of the Cu balls is 99.995% by mass or more and 99.9995% by mass or less. The true sphericity is above 0.95, The solder layer system (Sn-Pb)-based solder alloy containing Sn and Pb. For example, the Cu core ball of the first patent application, in which the content of Pb in the above solder layer is 0% by mass or more and 95.0% by mass or less, and Sn is the balance. For example, the Cu core ball of patent application item 1 or 2, wherein the above solder layer is composed of Pb (Sn-Pb) solder alloy containing Sn and 37.0% by mass or more and 95.0% by mass or less, The concentration ratio (%) of Sn contained in the above solder layer, to Concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or Concentration ratio (%) = (average of measured values (mass %)/target content (mass %)) × 100, The above concentration ratio is in the range of 70.0 to 140.0%. For example, the Cu core ball of patent application item 1 or 2, wherein the above solder layer is composed of Pb (Sn-Pb) solder alloy containing Sn and 37.0% by mass or more and 95.0% by mass or less, The concentration ratio (%) of Sn contained in the above solder layer, to Concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or Concentration ratio (%) = (average of measured values (mass %)/target content (mass %)) × 100, The above concentration ratio is in the range of 90.0 to 110.0%. For example, the Cu core ball of patent application item 1 or 2, the true sphericity is above 0.98. For example, the Cu core ball of patent application item 1 or 2 has a true sphericity of 0.99 or more. For example, the Cu core ball in the third item of the patent application scope, wherein the true sphericity is above 0.98. For example, the Cu core ball in the 4th range of patent application, the true sphericity is above 0.98. For example, the Cu core sphere of item 1 or 2 of the patent application, in which the amount of α rays is 0.0200 cph/cm ² or less. For example, the Cu core sphere of item 1 or 2 of the patent application, in which the amount of α rays is 0.0010 cph/cm ² or less. For example, the Cu core ball of claim 1 or 2 includes a metal layer covering the surface of the Cu ball. The surface of the metal layer is covered with the solder layer, and the true sphericity is 0.95 or more. For example, the Cu core ball according to item 3 of the patent application includes a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with the solder layer, and the true sphericity is 0.95 or more. For example, the Cu core ball of claim 4 has a metal layer covering the surface of the Cu ball, and the surface of the metal layer is covered with the solder layer, and the true sphericity is 0.95 or more. For example, the Cu core ball in the 11th range of patent application, the true sphericity is above 0.98. For example, the Cu core ball in the 11th range of patent application, the true sphericity is more than 0.99. For example, the Cu core ball of the 11th range of patent application, in which the amount of α rays is 0.0200cph/cm ² or less. For example, the Cu core ball of claim 11 of the patent application, in which the amount of α rays is 0.0010cph/cm ² or less. For example, the Cu core ball of claim 1 or 2, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. For example, the Cu core ball of claim 11 of the patent application, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. A welding head, which uses Cu core balls according to any one of patent application items 1 to 19. A solder paste which uses Cu core balls according to any one of patent application items 1 to 19. A foam solder, which uses Cu core balls according to any one of patent application items 1 to 19.

Images