TWI702299B - Cu core balls, solder joints, solder paste and foam solder - Google Patents

Abstract

The subject of the present invention is to provide a Cu core ball that can achieve high sphericity and low hardness, and uses a Cu ball that suppresses discoloration, and a solder joint, solder paste, and foam solder using the Cu core ball. The solution of the present invention is the Cu core ball 11A, which includes: Cu ball 1; and a solder layer 3 covering the surface of the Cu ball 1. The Cu ball 1 is at least one of Fe, Ag, and Ni. The total content is 5.0 mass ppm Above and below 50.0 mass ppm, S content is above 0 mass ppm and below 1.0 mass ppm, P content is above 0 mass ppm and below 3.0 mass ppm, the balance is Cu and other impurity elements, Cu core ball 1 The purity 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 a (Sn-Pb)-based solder alloy containing Sn and Pb.

Description

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

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

In recent years, due to the development of small information machines, electronic components loaded have been rapidly reduced in size. In order to meet the requirements of miniaturization, the ball grid array (hereinafter referred to as "BGA") with electrodes provided on the back surface is used for the narrowing of the pitch of the connection terminals and the reduction of the package area.

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

In the high-density packaging of electronic parts, sometimes alpha rays enter the memory cell of the semiconductor integrated circuit (IC), causing a soft error that causes the memory content to be rewritten. Therefore, in recent years, there has been development of low-alpha-ray soldering materials and Cu balls that reduce the content of radioisotopes. 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 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 will increase, so the durability against external stress will decrease, and the drop impact resistance will deteriorate. Therefore, Cu balls used for the assembly of electronic parts require a predetermined softness, that is, a Vickers hardness below a predetermined value.

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

When the sphericity of the Cu ball is low, it may not be possible to ensure the self-alignment when the Cu ball is assembled on the electrode. At the same time, the height of the Cu ball becomes uneven when the semiconductor wafer is assembled. Circumstances that cause 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 suitable sphericity and Vickers hardness.

In addition, the semiconductor package for 3D high-density packaging is a BGA. When the solder balls are loaded on the electrodes of the semiconductor wafer for reflow processing, the solder balls are crushed by the weight of the semiconductor package. If this happens, it can be considered that the solder will overflow from the electrodes, connecting the electrodes and causing a short circuit.

In order to prevent such short-circuit accidents, it has been proposed to use solder that does not collapse due to its own weight or deforms when the solder melts. Specifically, it is proposed to use a ball made of metal or the like as a core, and a 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. 5585751 [Patent Document 3] Japanese Patent No. 6256616

However, Cu balls containing more than a predetermined amount of S have a problem that sulfides or sulfur oxides are formed during heating, and the color is easily changed. The discoloration of the Cu ball may cause deterioration of wettability, and deterioration of wettability may cause non-wetting or deterioration of self-alignment. In this way, the Cu balls that are easily discolored are not suitable for coating with the metal layer because the adhesion between the Cu ball surface and the metal layer is reduced, or the oxidation or reactivity of the metal layer surface becomes high. On the other hand, when the sphericity of the Cu ball is low, the sphericity of the Cu core ball covered with the metal layer will also become low.

Therefore, the object of the present invention is to provide a Cu core ball capable of achieving high sphericity and low hardness, and inhibiting discoloration of the Cu ball, and a solder joint, solder paste, and foam solder using the Cu core ball.

The present invention is as follows.

(1) A Cu core ball comprising: a Cu ball; and a solder layer covering the surface of the Cu ball, and the Cu ball is at least one of Fe, Ag, and Ni, and the total content is 5.0 mass ppm or more and 50.0 mass ppm or less, The S content is 0 mass ppm or more and 1.0 mass ppm or less, the P content is 0 mass ppm or more and less than 3.0 mass ppm, and the balance is Cu and other impurity elements. The purity of the above Cu ball is 99.995% by mass or more and 99.9995% by mass or less, sphericity of 0.95 or more, and the solder layer is a (Sn-Pb)-based solder alloy containing Sn and Pb.

(2) The Cu core ball according to (1) above, wherein the solder layer has a Pb content of more than 0 mass% and 95.0 mass% or less, and Sn is the balance.

(3) The Cu core ball according to (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, as the concentration ratio (%)=(measured value (mass%)/target content (mass%))×100, or concentration ratio (%)=(Average of measured value (mass%)/target content (mass%))×100, the concentration ratio is in the range of 70.0~140.0%.

(4) The Cu core ball according to (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 is calculated as the concentration ratio (%) = (measured value (mass%)/target content (mass%)) × 100 or concentration ratio (%) = (average value of the measured values (mass %)/Target content (mass%))×100, the concentration ratio is in the range of 90.0~110.0%.

(5) The Cu core ball of (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 of (3) above, wherein the sphericity is 0.98 or more.

(8) The Cu core ball as described in (4) above, wherein the sphericity is 0.98 or more.

(9) The Cu core sphere according to (1) or (2) above, wherein the alpha radiation dose is 0.0200 cph/cm ² or less.

(10) The Cu core sphere according to (1) or (2) above, wherein the alpha radiation dose is 0.0010 cph/cm ² or less.

(11) The Cu core ball 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 sphericity is 0.95 or more.

(12) The Cu core ball described in (3) above 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 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 sphericity is 0.95 or more.

(14) The Cu core ball of (11) above, wherein the sphericity is 0.98 or more.

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

(16) The Cu core sphere as described in (11) above, wherein the alpha radiation dose is 0.0200 cph/cm ² or less.

(17) The Cu core sphere according to the above (11), wherein the α radiation dose is 0.0010 cph/cm ² or less.

(18) The Cu core ball of the above (1) or (2), wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less.

(19) The Cu core ball according to (11) above, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less.

(20) A welding joint 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.

According to the present invention, high sphericity and low hardness of the Cu ball can be realized, and the discoloration of the Cu ball can be suppressed. By realizing the high sphericity of the Cu ball, the high sphericity of the Cu core ball covered with the metal layer can be realized, and the self-alignment of the Cu core ball can be ensured when the Cu core ball is assembled on the electrode. Suppress the height error of Cu core ball. In addition, by realizing the low hardness of the Cu ball, the drop impact resistance of the Cu core ball covered with the metal layer can be improved. Furthermore, since the discoloration of the Cu ball is suppressed, the adverse effect of 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 unit (ppm, ppb, and %) of the composition of the Cu ball indicates the ratio to the mass of the Cu ball (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 related to the first embodiment of the present invention includes: a Cu ball 1; and a solder layer 3 covering the surface of the Cu ball 1.

FIG. 2 shows an example of the structure of the Cu core ball 11B according to the second embodiment of the present invention. As shown in FIG. 2, the Cu core ball 11B of the second embodiment of the present invention includes: Cu ball 1; a layer of one or more elements selected from Ni, Co, Fe, and Pd covering the surface of 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 an electronic component 60 in which a semiconductor wafer 10 is mounted on a printed circuit board 40 using Cu core balls 11A or Cu core balls 11B according to an embodiment of the present invention. As shown in FIG. 3, the Cu core ball 11A or the Cu core ball 11B is constructed on the electrode 100 of the semiconductor chip 10 by applying flux to the electrode 100 of the semiconductor chip 10 to wet and expand the molten solder layer 3 . In this example, the structure of the Cu core ball 11A or the Cu core ball 11B that is mounted on the electrode 100 of the semiconductor wafer 10 is referred to as a solder bump 30. The solder bumps 30 of the semiconductor wafer 10 are joined to the electrodes 41 of the printed circuit board 40 via the molten solder layer 3 or the solder melted by the solder paste applied to the electrodes 41. In this example, the structure in which the solder bumps 30 are mounted on the electrodes 41 of the printed circuit board 40 is called a soldering head 50.

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

Regarding the Cu core ball 11A of the first embodiment of the present invention, by increasing the sphericity of the Cu ball 1 covered with the solder layer 3, the sphericity of the Cu core ball 11A can be increased. In addition, regarding the Cu core ball 11B of the second embodiment of the present invention, by increasing the sphericity of the Cu ball 1 covered with the metal layer 2 and the solder layer 3, the sphericity of the Cu core ball 11B can be increased. Hereinafter, preferred aspects of the Cu balls 1 constituting the Cu core balls 11A and 11B will be described.

‧Cu ball true sphericity: 0.95 or more In the present invention, the so-called true 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 long-diameter quotient. The closer the value is to the upper limit of 1.00, the closer the true sphere is. The 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). Got. The length of the major diameter and the length of the diameter in the present invention are the lengths measured by the ULTRA Quick Vision, ULTRA QV350-PRO measuring device manufactured by Mitutoyo.

From the viewpoint of maintaining a suitable space between the substrates of the Cu ball 1, the sphericity is preferably 0.95 or more, more preferably 0.98 or more, and more preferably 0.99 or more. When the sphericity of the Cu ball 1 is less than 0.95, the Cu ball 1 becomes an indeterminate shape, and bumps with uneven height are formed when the bumps are formed, which increases the possibility of joint failure. If the sphericity is 0.95 or higher, since the Cu ball 1 does not melt at the welding temperature, the height error in the welding joint 50 can be suppressed. Thereby, it is possible to reliably prevent the bonding failure of the semiconductor wafer 10 and the printed circuit board 40.

‧Purity of Cu balls: 99.995% by mass or more and 99.9995% by mass or less Generally, Cu with a low purity is higher than Cu with a high purity because it can secure an impurity element that can become a crystalline nucleus of the Cu ball 1 in Cu, and the sphericity becomes higher. On the other hand, the Cu ball 1 with low purity will deteriorate electrical conductivity and thermal conductivity.

Therefore, if the purity of the Cu ball 1 is greater than or equal to 99.995% by mass (4N5) and less than or equal to 99.9995% by mass (5N5), 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 alpha dose, the conductivity and thermal conductivity of the Cu ball 1 can be suppressed from deterioration due to the decrease in purity.

When the Cu ball 1 is manufactured, a Cu material, which is an example of a metal material formed into a small piece of a predetermined shape, is melted by heating, and the molten Cu becomes spherical due to surface tension, and this is rapidly solidified into 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, when there are many impurity elements, the impurity elements become crystal nuclei and inhibit 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, relatively few can become crystal nuclei, and the growth of crystal grains cannot be suppressed and grows directionally. As a result, a part of the surface of the spherical molten Cu protrudes and solidifies and reduces the sphericity. Impurity elements include Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au, U, Th, etc.

The following describes the impurity content that determines the purity and sphericity of the Cu ball 1.

‧The total content of at least one of Fe, Ag and Ni: 5.0 mass ppm or more and 50.0 mass ppm or less Among the impurity elements contained in the Cu ball 1, the total content of at least one of Fe, Ag, and Ni is preferably 5.0 mass ppm or more and 50.0 mass ppm or less. That is, when any one of Fe, Ag, and Ni is contained, the content of one is preferably 5.0 mass ppm or more and 50.0 mass ppm or less, and when two or more of Fe, Ag, and Ni are contained, two or more 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 the melting of the Cu ball 1 production step. Therefore, a certain amount of Fe, Ag, or Ni is contained in Cu, and the Cu ball 1 with high sphericity can be produced. Therefore, at least one of Fe, Ag, and Ni is an important element for estimating the content of impurity elements. In addition, by making the total content of at least one of Fe, Ag, and Ni to be 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 after the Cu ball 1 is not slowly heated The annealing step in which the Cu ball 1 is slowly recrystallized by cooling slowly can also achieve the desired Vickers hardness.

‧S content is 0 mass ppm or more and 1.0 mass ppm or less The Cu ball 1 containing a predetermined amount of S forms sulfides or sulfur oxides when heated and easily discolors, 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 sulfide and sulfur oxide Cu balls 1 are formed, the brightness of the Cu ball surface becomes darker. Therefore, as will be described in detail later, as long as the result of measuring the brightness of the Cu ball surface 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 becomes phosphoric acid or becomes a Cu complex compound, which may adversely affect the Cu ball 1. In addition, since the hardness of the Cu ball 1 containing a predetermined amount of P increases, 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, Al, As, Cd, Pb, In, Sn, Au (hereinafter referred to as "other impurity elements") other than the aforementioned 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, as described above, contains at least one of Fe, Ag, and Ni as an essential element. However, since the Cu ball 1 cannot prevent the mixing of elements other than Fe, Ag, and Ni 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 ppm by mass, 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, if 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 ppm by mass, and the content of other impurity elements is less than 1 ppm, the purity of the Cu ball 1 is substantially 5N5 (99.9995% by mass).

‧Vickers hardness of Cu ball: 55.5HV or less The Vickers hardness of the Cu ball 1 is preferably 55.5HV or less. When the Vickers hardness is large, the durability against external stresses will decrease, the drop impact resistance will deteriorate, and cracks will easily occur. In addition, when an auxiliary force such as pressure is applied to the bumps of the three-dimensional structure or the formation of the joint, if a hard Cu ball is used, there is a possibility that the electrode may collapse. In addition, when the Vickers hardness of the Cu ball 1 is large, the crystal grains will become smaller than a certain range, and the conductivity will deteriorate. The Cu ball 1 has a Vickers hardness of 55.5 HV or less, and has good drop impact resistance, can suppress cracks, can also suppress electrode crushing, etc., and can further suppress deterioration in conductivity. In this embodiment, the lower limit of the Vickers hardness may be more than 0 HV, preferably more than 20 HV.

. Alpha radiation of Cu ball: 0.0200cph/cm ²

In order to ensure that the amount of α rays is such that the high-density packaging of electronic parts does not cause soft errors to be a problem, the α rays of the Cu ball 1 are preferably 0.0200 cph/cm ² or less. 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 0.0010 cph/cm ² or less. In order to suppress soft errors caused by alpha rays, the content of radioisotopes such as U and Th should be less than 5 mass ppb.

. Discoloration resistance: Brightness is above 55

Cu ball 1, with a brightness of 55 or more. The so-called lightness is the L* value of the L*a*b color system. Since the lightness of the Cu ball 1 that forms sulfides or sulfur oxides derived from S on the surface becomes low, if the lightness is 55 or more, it can be said that sulfides and sulfur oxides are suppressed. In addition, the Cu ball 1 having a brightness of 55 or more has good wettability during packaging. 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. Sulfides or sulfur oxides will not only have an adverse effect on the Cu ball 1, but the wettability will deteriorate when the Cu ball 1 is directly bonded to the electrode. The wettability deteriorates, non-wetting or deterioration of self-alignment may occur.

. Diameter of Cu ball: 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 or less. Within this range, spherical Cu balls 1 can be manufactured stably, and in addition, when the terminals have a narrow pitch, connection short-circuiting can be suppressed. Here, for example, when the Cu ball 1 is used in a paste, the "Cu ball" may also be referred to as "Cu powder". "Cu When "ball" is used in "Cu powder", the diameter of Cu ball is generally 1~300μm.

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

. Solder layer

The Cu core balls 11A and 11B of each embodiment 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 homogeneous is provided, and solder joints, solder paste, and foam solder using this are provided.

The composition of the solder layer 3 of the embodiment of the present invention is composed of a (Sn-Pb)-based alloy containing Sn and Pb. Regarding the Pb content, the Pb content of the entire alloy is in the range of more than 0% by mass and 95.0% by mass, and the Pb content is in the range of more than 0% by mass and 95.0% by mass, so that the Pb concentration ratio can be suppressed to the predetermined range. Inside. Here, the Pb distribution in the solder layer 3 is homogeneous, and the Sn distribution is also homogeneous. Similarly, if the Sn distribution in the solder layer 3 is homogeneous, the Pb distribution is also homogeneous. In the present invention, there is a composition example in which the content of Pb is higher than the content of Sn. Considering such a situation, in the following description, the distribution of Sn is assumed to be homogeneous, and the distribution of Pb is described as homogeneous.

The amount of Pb is within the range of 37.0-95.0% by mass for the entire alloy, that is, the amount of Sn for the entire alloy is within the range of 5.0-63.0% by mass. The concentration ratio of Sn can be controlled within the 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 the Pb content is 95.0% by mass and the target value of the sn content is 5.0% by mass, the allowable range of the Sn content and concentration ratio is 3.61% by mass (concentration ratio 72.2%) to 6.88% by mass (concentration ratio 137.6 %), the Sn concentration ratio can be controlled within a predetermined range of 70.0~140.0%, and the Sn distribution and Pb distribution in the solder layer 3 can be made homogeneous.

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

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

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

In addition, the allowable range refers to a range within which welding such as bump formation can be performed without problems. In addition, the so-called concentration ratio (%) refers to the ratio (%) of the measured value (mass %) to the target content (mass %), or the average value of the measured values (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 the measured values (mass %)/Target content (mass %))×100 means.

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

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

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

Although the thickness of the solder layer 3 differs depending on the particle size of the Cu ball 1, in order to ensure a sufficient amount of solder bonding, it is preferable that one 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 sphericity of the Cu core ball, the electroplating method is preferred.

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 the Cu ball is shaken, and the Pb concentration in the solution is adjusted uniformly for electroplating. When the solder plating layer is formed, the concentration of the plating solution is controlled to be constant.

In forming the solder plating layer, the concentration of the plating solution is controlled to a fixed plating 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 the predetermined value of Cu The nuclear ball is collected as a sample each time. After the collected sample is washed and dried, the particle size is measured.

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

Furthermore, when the content of Pb is higher than that of 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 to reduce the concentration of Pb in the liquid. Adjust the uniformity and perform the electroplating process, and control the concentration of the plating solution to a constant when forming the solder plating layer.

Sequentially measuring the particle size of the Cu core balls at the timing of the measurement. When the Sn content of the solder layer is at the target value, even if the solder layer is only increased by a predetermined thickness, the Sn content at this time is approximately the same as the previous content. Value. Therefore, the concentration distribution of Sn is homogeneous (equal) to the thickness of the coating, and it is understood that there is no concentration gradient. As above, the film thickness can be controlled to be uniform, but the concentration will be uneven in electroplating. By controlling the Sn concentration in the solder layer, the Sn concentration ratio is within a predetermined range, and Sn with a solder layer can be obtained. Homogeneously distributed Cu core balls.

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

In addition, since the outermost surface of the solder layer 3 covering the Cu core balls 11A and 11B becomes larger in the state of a single metal, the sphericity of the Cu core balls tends to decrease. In contrast, since Sn and Pb in the solder layer are substantially homogeneously distributed, the outermost surface of the solder layer is not a single metal, but is in an alloy state, and the crystal grains become smaller. Thereby, the sphericity of the Cu core ball is high, which is 0.99 or more. The sphericity of the Cu core ball is 0.95 or more. When the Cu core ball is mounted on the electrode for reflow, the positional deviation caused by the Cu core ball can be suppressed, and the self-alignment can be improved.

The concentration of Sn and Pb in the solder layer is maintained at substantially the same state even when the thickness of the solder layer grows. It can be seen that Sn and Pb in the solder layer grow in a substantially homogeneously distributed state. In a state where the concentrations of Sn and Pb in the plating solution are homogenized, the concentrations of Sn and Pb are brought within a desired value, and the plating treatment 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 reach the target value.

In order to bring the concentration distribution of Sn and Pb in the solder layer to the desired value, plating is performed while controlling the voltage and current. Through 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 by using a low-α-ray content solder alloy in the solder layer 3 to form low-α-ray Cu core balls 11A and 11B.

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

‧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 multiple layers) containing two or more elements of Ni, Co, Fe, and Pd. When the Cu core ball 11B is used for solder bumps, the metal layer 2 does not melt and remains at the soldering temperature, but contributes to the height of the solder joint. Therefore, the structure has a high sphericity and a small diameter error. In addition, from the viewpoint of suppressing soft errors, it is configured to have a low alpha dose.

‧The composition and thickness of the metal layer The composition of the metal layer 2 is that when the metal layer 2 is composed of a single Ni, Co, Fe, or Pd, except for 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 combined from Ni, Co, Fe, or Pd may also be used. In addition, the metal layer 2 may be composed of multiple layers of a single layer composed of Ni, Co, Fe, or Pd and a layer 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.

‧The alpha dose of the Cu core ball: 0.0200 cph/cm ² or less The alpha dose of the Cu core ball 11A of the first embodiment and the Cu core ball 11B of the second embodiment of the present invention is 0.0200 cph/cm ² or less good. This is a high-density packaging of electronic components, which is an alpha dose that does not make soft errors a problem. Regarding the α dose of the Cu core ball 11A of the first embodiment of the present invention, the α dose of the solder layer 3 constituting the Cu core ball 11A can be achieved by 0.0200 cph/cm ² or less. Therefore, since the Cu core ball 11A of the first embodiment of the present invention is covered with such a solder layer 3, it exhibits a low alpha dose. Regarding the α dose of the Cu core ball 11B of the second embodiment of the present invention, the α dose of the metal layer 2 and the solder layer 3 constituting the Cu core ball 11B can be achieved by 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 exhibits a low alpha dose. 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 0.0010 cph/cm ² or less. In order to make the α-ray dose of the Cu ball 1 0.0200 cph/cm ² or less, the U and Th contents of the metal layer 2 and the solder layer 3 are 5 ppb or less, respectively. In addition, from the viewpoint of suppressing soft errors in current or future high-density packaging, the contents of U and Th are preferably 2 ppb or less.

‧Spherical degree of Cu core ball: 0.95 or more Regarding 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 sphericity is preferably 0.95 or more, more preferably 0.98 or more, and more preferably 0.99 or more. The sphericity of the Cu core balls 11A and 11B is less than 0.95, and the Cu core balls 11A and 11B will become indefinite shapes. When the Cu core balls 11A and 11B are loaded on the electrode for reflow, the Cu core balls 11A will be formed. , 11B position shifts, and self-alignment will also deteriorate. If the sphericity of the Cu core balls 11A, 11B is 0.95 or more, it is possible to ensure self-alignment when the Cu core balls 11A, 11B are assembled on the electrode 100 of the semiconductor wafer 10 or the like. Then, by setting the sphericity of the Cu ball 1 to 0.95 or more, the Cu core balls 11A and 11B do not melt the Cu ball 1 and the metal layer 2 at the soldering temperature, so that the height error of the solder joint 50 can be suppressed. Thereby, it is possible to reliably prevent the bonding failure of the semiconductor wafer 10 and the printed circuit 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 Sn ₅ , Cu ₃ Sn is an intermetallic compound, and cracks will become serious when impacted, and there is a possibility of damage to the connection part. Therefore, in order to obtain sufficient connection strength, it is better 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 acting as a barrier layer is formed on the surface of the Cu ball 1, it is possible to prevent the Cu of the Cu ball 1 from diffusing into the paste solder.

‧Solder paste, foam solder, soldering head In addition, it is also possible to form a solder paste by including Cu core ball 11A or Cu core ball 11B in the solder. By dispersing the Cu core ball 11A or the Cu core ball 11B in the solder, a foamed solder can be formed. The Cu core ball 11A or the Cu core ball 11B can also be used to form a bonding joint between the bonding electrodes.

‧Method of manufacturing Cu ball Next, an example of a method of manufacturing the Cu ball 1 will be described. As an example of the metal material, the Cu material is placed on a heat-resistant plate such as ceramic (hereinafter referred to as "heat-resistant plate") and heated in a furnace together with the heat-resistant plate. The heat-resistant plate is provided with many circular grooves with a hemispherical bottom. The diameter and depth of the groove can be appropriately set according to the particle size 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 the thin Cu wires are put into the grooves of the heat-resistant plate one by one. Put a heat-resistant plate made of Cu material into the groove, raise the temperature to 1100 to 1300°C in a furnace filled with ammonia decomposition gas, and heat it for 30 to 60 minutes. At this time, if the temperature in the furnace is higher than the melting point of Cu, the Cu material will melt into a spherical shape. After that, it is cooled in a furnace, and the Cu ball 1 is rapidly cooled in the groove of the heat-resistant plate to form it.

In addition, as another method, there is a spray method in which molten Cu is dropped from a small hole provided at the bottom of the crucible, and the drop is quenched to room temperature (for example, 25°C) to pellet Cu balls 1, or cut Cu with thermoplasma A method of pelletizing metal by heating at 1000°C or higher.

In the manufacturing method of the Cu ball 1, before pelletizing the Cu ball 1, you may heat-process the Cu material which is the raw material of the Cu ball 1 at 800-1000 degreeC.

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

When using a high-purity Cu material in this way, the above-mentioned heating treatment may not be performed, and the holding temperature of molten Cu may be reduced to about 1000° C. as before. In this way, the heating treatment described above can be omitted or changed as appropriate in accordance with the purity of the Cu material and the alpha dose. In addition, when Cu balls 1 with a high alpha dose or irregular Cu balls 1 are manufactured, the Cu balls 1 can be reused as a raw material to make the alpha dose lower.

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 a Ni plating layer, for the Ni plating bath, a Ni metal block or Ni metal salt is used to prepare a Ni plating solution, and the Cu balls 1 are immersed in the prepared Ni plating solution to deposit on the surface of the Cu balls 1. The Ni plating layer 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 may also be adopted. When the Sn alloy solder layer 3 is formed on the surface of the metal layer 2, the above-mentioned electroplating 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 balls of Examples 1 to 19 and Comparative Examples 1 to 12 were produced with the compositions shown in Table 1 and Table 2 below, and the sphericity, Vickers hardness, alpha dose, and discoloration resistance of the Cu balls were measured.

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

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

In the following table, numbers without units indicate mass ppm or mass ppb. Specifically, the numerical values in the table showing 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 the content ratio of the impurity element to the Cu ball, which is less than 1 mass ppm. In addition, the numerical values indicating the content ratios of U and Th in the table indicate mass ppb. "<5" means the content ratio of the impurity element to the Cu ball, which is less than 5 mass ppb. The "total amount of impurities" means the total proportion of impurity elements contained in the Cu ball.

‧The production of Cu ball The production conditions of Cu balls were studied. As a Cu material as an example of a metal material, a bulk material is prepared. As Cu materials of Examples 1 to 13, 19, and Comparative Examples 1 to 12, purity 6N was used, and Cu materials of Examples 14 to 18 were used purity 5N. Put each Cu material into the crucible, raise the temperature of the crucible to 1200°C, heat for 45 minutes to melt the Cu material, and drop the molten Cu from the hole provided at the bottom of the crucible, and cool the resulting droplets to room temperature (18 ℃) pelletized into Cu balls. In this way, Cu balls having an average particle diameter of the values shown in the following tables were produced. Elemental analysis can be performed with high precision using inductively coupled plasma mass spectrometry (ICP-MS analysis) or glow discharge mass spectrometry (GD-MS analysis), but in this case, ICP-MS analysis is used. The spherical diameter of the Cu ball is 250 μm in all of Examples 1 to 19 and Comparative Examples 1 to 12.

‧The production of Cu core ball Regarding Examples 1A to 19A, using the Cu balls of Examples 1 to 19, the solder alloys of Composition 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, with regard to Examples 1B-19B, the Cu balls of the above-mentioned Examples 1-19 were used to form a Ni plating layer with a thickness of 2 μm on one side as a metal layer. The solder alloys of the composition Examples 1 to 4 were further formed with a thickness of one side by electroplating. The 23μm solder layer was produced in Examples 1B-19B.

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

Hereinafter, each evaluation method of the sphericity of the Cu ball and the Cu core ball, the alpha dose of the Cu ball, the Vickers hardness, and the discoloration resistance will be described in detail.

‧Sphericality The sphericity of Cu ball and Cu core ball is measured by CNC imaging measurement 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 of the sphericity of Cu balls and Cu core balls are as follows. ○○○: The sphericity is 0.99 or more ○ ○: The sphericity is 0.98 or more and less than 0.99 ○: The sphericity is 0.95 or more and less than 0.98 ╳: The true spherical degree is less than 0.95

‧Vickers hardness The Vickers hardness of Cu balls is measured in accordance with "Vickers Hardness Test-Test Method JIS Z2244". The device uses a micro Vickers hardness tester manufactured by Akashi Manufacturing, AKASHI Micro Hardness Tester MVK-F 1200l-Q.

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

‧Alpha radiation The method for measuring the α dose of Cu balls is as follows. For the measurement of the alpha dose, an alpha radiation measuring device with a ventilation ratio counter is used. For the measurement sample, a 300mm×300mm flat shallow-bottomed container was covered with Cu balls so that the bottom of the container could not be seen. Put the sample to be measured in the α-ray measuring device and leave it for 24 hours under PR-10 ventilation, and then measure the α-ray dose.

[Evaluation Criteria of α Dosage] In the following tables, the evaluation criteria of α dosing of Cu balls are as follows. ○ ︰α ray radiation amount is an amount of ² or less ╳︰α 0.0200cph / cm exceeds 0.0200cph / cm ²

In addition, the PR-10 gas (argon 90%-methane 10%) used for the measurement is more than 3 weeks after filling the gas cylinder with PR-10 gas. The use of gas cylinders that have passed more than 3 weeks is because radon in the atmosphere does not enter the gas cylinder to produce alpha rays, and it complies with the JEDEC STANDARD-Alpha Radiation Measurement specified by JEDEC (Joint Electron Device Engineering Council) in Electronic Materials JESD221.

‧Discoloration resistance In order to measure the discoloration resistance of the Cu balls, the Cu balls were heated in a constant temperature bath at 200° C. for 420 seconds in an air atmosphere, and the change in brightness was measured to evaluate whether the Cu balls were sufficiently resistant to changes over time. Brightness, using Konica Minolta CM-3500d spectrophotometer, D65 light source, 10∘ field of view, in accordance with JIS Z 8722 "Method of measuring color-reflection and penetration object color", to measure the spectral transmittance, Obtained from the color value (L*, a*, b*). Furthermore, (L*,a*,b*) complies with JIS Z 8729 "Method of Representing Color-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 of the discoloration resistance of Cu balls are as follows. ○: The brightness after 420 seconds is 55 or more ╳: The brightness after 420 seconds is less than 55.

‧Overview According to the above-mentioned evaluation method and evaluation criteria, the Cu balls whose sphericity, Vickers hardness, alpha dose, and discoloration resistance are all ○, ○○, or ○○○ are comprehensively evaluated as ○. On the other hand, Cu balls with any one of sphericity, Vickers hardness, alpha dose, and discoloration resistance as ╳ are evaluated as ╳ in a comprehensive evaluation.

In addition, in the above-mentioned evaluation methods and evaluation criteria, Cu core balls with a sphericity of ○, ○○, or ○○○ were evaluated as ○ together with the evaluation of Cu balls. On the other hand, the Cu core ball with a sphericity of ╳ has a comprehensive evaluation of ╳. In addition, even in the evaluation of the Cu core ball, the sphericity is ○, ○○ or ○○○, in the evaluation of the Cu ball, any one of the sphericity, Vickers hardness, alpha dose and discoloration resistance is ╳Cu core ball, in the overall evaluation is ╳.

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 was not evaluated. However, in the Cu core ball, as long as the Vickers hardness of the Cu ball is within the range specified in the present invention, even the Cu core ball has good drop impact resistance and can inhibit cracks and electrode crushing. It can also suppress deterioration of conductivity.

On the other hand, when the Vickers hardness of the Cu core ball and the Cu ball exceeds the range specified in the present invention, the durability against external stress cannot be solved, the durability against the external stress will be reduced, the drop impact resistance will be deteriorated, and it will become easier. The problem of cracks.

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

In addition, since the discoloration resistance of the Cu core ball depends on the Ni plating layer, which is an example of the solder layer and the metal layer, the discoloration resistance of the Cu core ball was not evaluated. However, as long as the brightness of the Cu ball is within the range specified in the present invention, the sulfide or sulfur oxide on the surface of the Cu ball can be suppressed, so it is suitable for coating with a metal layer such as a solder layer and a Ni plating layer.

On the other hand, when the brightness of the Cu ball is lower than the range specified in 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 is less than 55 are not suitable for the evaluation of the discoloration resistance, so the overall evaluation is ╳.

In addition, the α-ray dose of the Cu core ball depends on the composition of the plating solution raw material constituting the solder layer covering the Cu ball, and each element in the composition. When the Ni plating layer, which is an example of the metal layer covering the Cu ball, is provided, it also depends on the plating solution raw material constituting the Ni layer.

When the Cu ball is the low alpha dose specified in the present invention, as long as the plating solution raw materials constituting the solder layer and the Ni plating layer use the low alpha dose specified in the present invention, the Cu core ball can also become the low alpha dose specified in the present invention. Ray dose. In this regard, the solder layer, the plating solution raw material constituting the Ni plating layer is a high alpha dose exceeding the predetermined alpha dose of the present invention, and even if the Cu ball has the above low alpha dose, the Cu core ball will be more than that of the present invention. The high alpha dose of the prescribed alpha dose.

In addition, when the alpha dose of the plating solution raw materials constituting the solder layer and the Ni plating layer shows a slightly higher alpha dose than the low alpha dose specified in the present invention, the impurities can be removed in the above-mentioned plating process, and the α can be removed. The dose is reduced to the low alpha dose range specified in the present invention.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

As shown in Table 1, the Cu balls of the respective Examples having a purity of 4N5 or more and 5N5 or less have all obtained good results in comprehensive evaluation. From this, it can be said that the purity of the Cu ball is preferably 4N5 or more and 5N5 or less.

The following describes the details of the evaluation, as in Examples 1 to 12 and 18. Cu balls with a purity of 4N5 or more and 5N5 or less, and containing 5.0 mass ppm or more and 50.0 mass ppm or less of Fe, Ag or Ni, sphericity, The comprehensive evaluation of Vickers hardness, alpha dose and discoloration resistance gave good results. As shown in Examples 13 to 17, and 19, Cu balls with a purity of 4N5 or more and 5N5 or less, and a total of 5.0 mass ppm or more and 50.0 mass ppm or less of Fe, Ag, or Ni are also in true sphericity, Vickers hardness, α The comprehensive evaluation of radiation dose and discoloration resistance gave good results. In addition, although not shown in the table, from Examples 1, 18, and 19, the content of Fe is 0 ppm by mass or more and less than 5.0 ppm by mass, and the Ag content is 0 ppm or more and less than 5.0 ppm by mass. 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 by comprehensive evaluation of sphericity, Vickers hardness, alpha dose, and discoloration resistance Good results.

In addition, as shown in Example 18, Sb, Bi, Zn, Al, As, Cd, Pb, In, and Sn are contained in a total of 5.0 mass ppm or more and 50.0 mass ppm or less of Fe, Ag, or Ni, and other impurity elements. The Cu balls of Example 18 in which Au and Au were 50.0 mass ppm or less also obtained good results in the comprehensive evaluation of sphericity, Vickers hardness, alpha dose, and discoloration resistance.

Regarding the Cu core balls, as shown in Tables 3 and 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) covers Example 1 ~ The Cu core balls of Examples 1A to 19A of the Cu balls of Example 19, the Cu balls of Example 1 to Example 19 were covered with Ni plating, and the solder layer of the solder alloy of Example 1 was further covered in Example 1B~ The 19B Cu core ball has a good result in the comprehensive evaluation of the 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 the Cu balls of Examples 1A to 19A of Examples 1 to 19 Cu core balls, the Cu balls of Examples 1 to 19 are covered with Ni plating, and the Cu core balls of Examples 1B to 19B are further covered with the solder layer of the solder alloy composition of Example 2. The results are obtained by comprehensive evaluation of the sphericity Good results.

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 the Cu balls of Examples 1A-19A of Examples 1 to 19 Cu core balls, the Cu balls of Examples 1 to 19 are covered with Ni plating, and the Cu core balls of Examples 1B to 19B, which are further covered with the solder layer of the solder alloy of Example 3, are evaluated in the comprehensive evaluation of 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 being Sn (Sn content: 60.0% by mass) covers the Cu balls of Example 1 to Example 19 The Cu core balls of Examples 1A to 19A, the Cu balls of Examples 1 to 19 were covered with Ni plating, and the Cu core balls of Examples 1B to 19B were covered with the solder layer of the solder alloy of Example 4. The comprehensive evaluation of sphericity 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, and the Ag content is 0 mass ppm or more and less than 5.0 mass ppm. ppm, Ni content is 0 mass ppm or more and less than 5.0 mass ppm, and the total of Fe, Ag, or Ni is 5.0 mass ppm or more Cu balls, covered with a solder layer of any of the solder alloys of composition example 1 to composition example 4 For Cu core balls, the same Cu balls are covered with Ni plating, and the Cu core balls covered with the solder layer of any of the solder alloys of composition example 1 to composition example 4 have obtained good results in the comprehensive evaluation of sphericity.

On the other hand, in the Cu ball of Comparative Example 7, not only the total content of Fe, Ag, and Ni is less than 5.0 mass ppm, U and Th are less than 5 mass ppb, and other impurity elements are also less than 1 mass ppm. Comparative Example 7 The Cu balls of Comparative Example 7, the Cu core balls of Comparative Example 7A covered with the solder layer of the solder alloy of each composition example, and the Cu balls of Comparative Example 7 covered with the Ni plating layer, and the Cu balls of Comparative Example 7 The Cu core ball of Comparative Example 7B covered with the solder layer of the solder alloy has a sphericity of less than 0.95. In addition, even if it contains impurity elements, the total content of at least one of Fe, Ag, and Ni is less than 5.0 mass ppm for the Cu ball of Comparative Example 12. The Cu ball of Comparative Example 12 is used as the solder layer of the solder alloy of each composition example. The Cu core balls of Comparative Example 12A were covered, the Cu balls of Comparative Example 12 were covered with Ni plating, and the Cu core balls of Comparative Example 12B were further covered with the solder layer of the solder alloy of each composition example, and the sphericity was less than 0.95. From these results, at least one of Fe, Ag, and Ni has a Cu ball whose total content is less than 5.0 ppm by mass. The Cu ball is covered with the Cu core ball of the solder alloy of each composition example, and the Cu ball It can be said that the Cu core balls 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 was 153.6 mass ppm, and the content of other impurity elements was 50 mass ppm or less, but the Vickers hardness exceeded 55.5 HV, and good results were 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, the content of other impurity elements, especially Sn, is 151.0 mass ppm, which greatly exceeds 50.0 mass ppm, and the Vickers hardness It exceeds 55.5HV, and no good results are obtained. Therefore, even for Cu balls with a purity of 4N5 or more and 5N5 or less, Cu balls with a total content of at least one of Fe, Ag, and Ni exceeding 50.0 mass ppm will 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 exceeds the range specified by the present invention, the durability against external stress will be lowered, the drop impact resistance will be deteriorated, and cracks will easily occur. Furthermore, it can be said that other impurity elements are preferably contained in the range of not more than 50.0 mass ppm.

From these results, it can be said that a Cu ball with a purity of 4N5 or more and 5N5 or less, and the total content of at least one of Fe, Ag, and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less can achieve high sphericity and Low hardness, and 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, the Cu 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 In addition, by achieving low hardness of the Cu ball, even when the Cu core ball is made, the drop impact resistance is good, cracks can be suppressed, electrode crushing, etc., and deterioration of conductivity can be suppressed. Furthermore, by suppressing the discoloration of the Cu ball, it is suitable for covering with a metal layer such as a solder layer and a Ni plating layer. The content of other impurity elements is preferably 50.0 mass ppm or less.

Although not shown in the table, Cu balls with the same composition as those of the examples, with a spherical diameter of 1 μm or more and 1000 μm or less, were obtained by comprehensive evaluation of sphericity, Vickers hardness, α dose, and discoloration resistance. Good results. It can be said that the spherical 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 2.9 mass ppm of P. It has excellent sphericity, Vickers hardness, α radiation dose, and discoloration resistance. The comprehensive evaluation of the results 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 coated with Ni plating, and the Cu core ball is further covered with the solder layer of the solder alloy of each composition example , Good results are obtained in the comprehensive evaluation of sphericity. In the Cu ball of Comparative Example 11, the total content of Fe, Ag, and Ni was 50.0 mass ppm or less as in the Cu ball of Example 19, but the Vickers hardness exceeded 5.5HV and showed a different result from the Cu ball of Example 19 . In addition, in Comparative Example 9, the Vickers hardness exceeded 5.5HV. This is considered to be because the P content of Comparative Examples 9 and 11 is significantly higher. From this result, it can be seen that when the P content increases, the Vickers hardness increases. Therefore, it can be said that the content of P is preferably less than 3 ppm by mass, and more preferably less than 1 ppm by mass.

The α-ray dose of the Cu balls of each example is 0.0200 cph/cm ² or less. Therefore, in the solder alloys of composition example 1 and composition example 2 covering the Cu balls of each of Examples 1-19, the Cu of each example 1A-19A has a low alpha radiation dose specified by the present invention. The core ball also exhibits the low alpha radiation dose specified 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 made to have the low alpha radiation dose specified in the present invention. The Cu core balls of each of Examples 1B-19B It also becomes the low alpha dose prescribed by the present invention.

Furthermore, by the plating process for forming the solder layer and the Ni plating layer, the impurities contained in the alloy that emit α rays are removed, and the α rays of the alloy before plating show lower α rays than those specified in the present invention. In the case of a slightly higher α dose, the α dose after plating can be reduced to the low α dose range specified in the present invention.

Thereby, when the Cu core balls of each embodiment are used for high-density packaging of electronic parts, soft errors can be suppressed by making the raw materials constituting the solder layer and the Ni plating layer have the low alpha dose prescribed in the present invention.

In the Cu ball of Comparative Example 7, good results of discoloration resistance were obtained, but results of good discoloration resistance were not obtained in Comparative Examples 1 to 6. Comparing the Cu balls of Comparative Examples 1 to 6 with the Cu balls of Comparative Example 7, the only difference in these compositions is the S content. Therefore, in order to obtain a result with good discoloration resistance, it can be said that the content of S needs to be less than 1 ppm by mass. In the Cu balls of each example, since the content of S is less than 1 ppm by mass, it can be said that the content of S is preferably less than 1 ppm by mass.

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

[Table 7]

From this table, comparing the lightness before heating and the lightness after heating for 420 seconds, the lightness of Example 14, Comparative Examples 1, and 5 was a value around 64 or 65 before heating. After heating for 420 seconds, the lightness of Comparative Example 5 containing 30.0 ppm by mass of S became the lowest. Next, Comparative Example 1 containing 10.0 ppm by mass of S in order, and the example in which the S content was less than 1 ppm by mass. 14. It can be said that the higher the S content, the lower the lightness after heating. Since the Cu balls of Comparative Examples 1 and 5 have a brightness of less than 55 and contain more than 10.0 mass ppm of S, it can be said that sulfides or sulfur oxides are easily formed and discolored when heated. In addition, when the S content 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, as a result of mounting the Cu ball of Example 14 on the electrode, it showed good wettability.

As above, the purity is 4N5 or more and 5N5 or less, the total content of at least one of Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, and the S content is 0 mass ppm or more and 1.0 mass ppm or less, P The Cu balls of this example with a content of 0 mass ppm or more and less than 3.0 mass ppm can achieve high sphericity because the sphericity is all 0.95 or more. By achieving high sphericity, the self-alignment of the Cu core ball when assembled on the electrode can be ensured, and the height error of the Cu core ball can be suppressed. The same effect can be obtained by covering the Cu ball of this embodiment with a Cu core ball covered by a solder layer, covering the Cu ball of this embodiment with a metal layer, and further covering the Cu core ball of the metal layer with a solder layer.

In addition, the Cu balls of the present example have a Vickers hardness of 55 HV or less, so low hardness can be achieved. By achieving low hardness, the impact resistance of Cu balls can be improved. Since the Cu ball achieves low hardness, the Cu ball of this embodiment is covered with a Cu core ball 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 property is also good, cracks can be suppressed, electrode crushing, etc. can also be suppressed, and deterioration of conductivity can also be suppressed.

In addition, in all 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 the wettability when the Cu balls are assembled on the electrode can be improved. Since the discoloration of the Cu ball is suppressed, it is suitable for covering with a metal layer such as a solder layer and Ni plating layer.

Furthermore, in the Cu material of this example, a Cu block with a purity of more than 4N5 and less than 6N is used to produce a Cu ball with a purity of 4N5 or more and 5N5 or less. However, a wire or plate with a purity of more than 4N5 and less than 6N is used. Both the ball and Cu core ball have also obtained good results in comprehensive evaluation.

Next, the Cu core ball on the surface of the Cu ball covered with the solder layer of the Sn-based solder alloy will describe the element distribution of Sn and Pb in the solder layer. As the solder layer covering the Cu balls, a solder alloy containing Sn as a main component 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. Sn-based solder alloys containing Bi have a relatively low melting temperature of 130 to 140°C and are called low-temperature solders.

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) becomes thicker.

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

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

As mentioned above, when a binary or higher Sn-based solder alloy with other elements added to Sn is placed on the Cu core ball coated on the surface of the Cu ball on the electrode of the semiconductor wafer, the added element is in the solder layer. Patent Documents 4 and 5, which have a concentration gradient, cause the following problems.

The technique disclosed in Patent Document 4 is a solder layer with Bi concentration having a concentration gradient that is lighter on the inner periphery and thicker on the outer periphery. With such a concentration gradient (the inner side is lighter and the outer side is thicker), the timing of Bi melting There is a possibility of a slight deviation between the inner peripheral side and the outer peripheral side.

When the melting timing is shifted, even if the outer surface of the Cu core ball starts to melt, the area on the inner peripheral surface side has not yet melted, and the mixture is partially melted. As a result, the position of the core material is slightly shifted 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 4. At this time, in order to connect the semiconductor package, a heat treatment of reflow is required. If the Bi concentration of the solder layer of Patent Document 5 is concentrated on the inner periphery and light on the outer periphery, it is heated and melted. Since the Bi density on the inner periphery is high, the solder will start to melt from the Bi region on the inner periphery. Even if the Bi region on the inner circumference side has melted, the Bi region on the outer circumference side has not started to melt, so the volume expansion of the Bi region on the inner circumference side will occur early.

Due to the speed of volume expansion on the inner and outer circumferences, a pressure difference occurs between the inner and outer circumferences of Bi (outer air), and the outer circumference of Bi starts to melt, the core Cu ball will be generated due to the pressure difference of the volume expansion on the inner circumference. Bounce situation. This situation must be avoided.

Such a Cu core ball having a solder layer composed of a Sn-based solder alloy composed of Sn and Bi may cause defects when there is a concentration gradient of Bi in the solder layer.

In recent years, Pb-free solder alloys have been widely used. On the other hand, for specific applications such as electronic devices used in space, solder alloys containing Pb are used. In this way, it is considered that the core material covered with a binary or higher solder alloy with Pb added to Sn has a predetermined concentration gradient of Pb in the solder layer, and the same problem as the aforementioned Bi occurs.

Therefore, the effect of uniform distribution of Pb in the solder layer 3 will be described next. In order to confirm that the Pb concentration distribution in the solder layer 3 has a corresponding target value, the following experiment is 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 higher than that of 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 is corresponding to the target value. (1) Under the following conditions, a Cu core ball 11B in which the composition of the solder layer 3 is Sn 5 mass% and Pb 95 mass% (Sn-95Pb) is produced. In the following examples, Cu balls of the composition of Example 17 shown in Table 1 were used. ‧The diameter of Cu ball 1: 250μm ‧The film thickness of the metal layer (Ni plating) 2: 2μm ‧The film thickness of the solder layer 3: 23μm ‧The 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 made by electroplating method. (2) As samples, 10 Cu core balls 11B formed with a solder layer of (Sn-95Pb) based solder alloy of the same composition were prepared. Use these as sample A. (3) Ten samples A are sealed with resin. (4) Each sealed sample A was polished with each resin to observe the cross section of each sample A. The observation equipment used FE-EPMAJXA-8530F manufactured by JEOL.

Fig. 6 is an explanatory diagram showing an example of a method of measuring the Sn concentration distribution of 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 middle layer 16b is 9 to 17 μm, and the outer layer 16c is 17 to 23 μm. From the inner layer 16a, the middle layer 16b and the outer layer 16c, as shown in FIG. 6 in this example, The inner layer area 17a, the middle area 17b, and the outer layer area 17c were cut out with a thickness of 5 μm and a width of 40 μm, and each area was used as a measurement area, and the Sn concentration was measured by qualitative analysis. This operation is performed for 10 fields of view 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 middle layer, and the outer layer of the solder layer.

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

For sample A, as described above, the Sn concentration of the inner layer, the middle layer, and the outer layer was measured for 10 Cu core balls. Regarding sample A, the measured values of the Sn concentration of each of the inner, middle, and outer layers of 10 Cu core balls are not shown in Table 8.

For sample A, the target Sn content (target value) is 5 mass%. At this time, the Sn concentration ratio (%) of each of the 10 Cu core spheres in the sample A is obtained from the measured value of the Sn concentration, and the following formula (1) is obtained. 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 the sample is 10. Average value of Sn concentration=total value of 10 measurement values/10...(2)

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

Concentration ratio (%)=(Average of measured values/5)×100...(3)

As shown in Table 8, regarding the example of sample A, the average value of the Sn concentration in the inner layer region 17a is 6.88% by mass, the concentration ratio is 137.6%, and the average value of the 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 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 middle layer region 17b, and the outer layer region 17c is within the allowable range of 3.61 mass% to 6.88 mass%, and the concentration ratio is 72.2% to 137.6%, which indicates that it is roughly on target The Sn concentration ratio of the value is 70%~140%.

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

Regarding the bonding results, the judgment that no bonding failure was detected for all samples was "good".

There was no case where 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 bounced off. In addition, the entire solder layer 3 could be melted almost uniformly. The positional shift of the core material, which is considered to be caused by the shift of the melting timing, does not occur, so there is no risk of short circuit between the electrodes due to displacement or the like. Therefore, a good result was obtained without the occurrence of poor joining, 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 allowable range is 3.61% by mass (concentration ratio 72.2%) to 6.88% by mass (concentration ratio 137.6%).

Next, the same measurement was performed on the case where the solder layer 3 of the Sn-based solder alloy composed of 10% by mass of Sn and 90% by mass of Pb (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 method of producing the Cu core ball is the same as in the example of the sample A of the Cu core ball using the aforementioned (Sn-95Pb) solder alloy.

Regarding specifications such as the diameter of the Cu ball and Cu core ball, the film thickness of the metal layer (Ni plating) and the solder layer, and the experimental conditions, except for the composition of the solder layer, the same conditions as the sample A were used.

The results are shown as sample B in 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 on the same sample), although there are some errors (the minimum of the average is 9.74% by mass ( Concentration ratio 97.4%) ~ 11.20% by mass (concentration ratio 112.0%)), but within the allowable range. Therefore, it can be seen that it is in the range of 9.74% by mass (concentration ratio of 97.4%) to 11.20% by mass (concentration ratio of 112.0%). The joining judgment was the same as in the example of the sample A, and since a good result was obtained that no joining failure occurred at all, it was judged as "good".

The target Sn content (target value) of the sample B is 10 (mass%). Therefore, the concentration ratio (%) of sample B in Table 8 is obtained by the following formula (4). Concentration ratio (%)=(average 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 method of producing the Cu core ball is the same as in the example of the sample A of the Cu core ball using the aforementioned (Sn-95Pb) solder alloy.

Regarding specifications such as the diameter of the Cu ball and Cu core ball, the film thickness of the metal layer (Ni plating) and the solder layer, and the experimental conditions, except for the composition of the solder layer, the same conditions as the sample A were used.

The results are shown as sample C in 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 is some error (the minimum of the average is 61.30% by mass ( Concentration ratio 97.3%)~Maximum 70.02 mass% (concentration ratio 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 joining judgment was the same as in the example of the sample A, and since a good result was obtained that no joining failure occurred at all, it was judged as "good".

The target Sn content (target value) of the sample C is 63 (mass%). Therefore, the concentration ratio (%) of 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 on the case where the solder layer 3 of the Sn-based solder alloy composed of Sn60% by mass, Pb37% by mass, and Ag3% by mass (Sn-37Pb-3Ag) was formed. At this time, the target value of Sn distribution is 60% by mass, but the allowable range is 55.83% by mass (concentration ratio of 93.1%) to 63.10% by mass (concentration ratio of 105.2%). The method of producing the Cu core ball is the same as in the example of the sample A of the Cu core ball using the aforementioned (Sn-95Pb) solder alloy.

Regarding specifications such as the diameter of the Cu ball and Cu core ball, the film thickness of the metal layer (Ni plating) and the solder layer, and the experimental conditions, except for the composition of the solder layer, the same conditions as the sample A were used.

The results are shown as 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 to 63.10% by mass (all are the average of 10 measurements on the same sample), although there is some error (the minimum average value is 55.83% by mass ( Concentration ratio 93.1%) to maximum 63.10 mass% (concentration ratio 105.2%), but within the allowable range. Therefore, it can be seen that it is in the range of 55.83 mass% (concentration ratio 93.1%) to 63.10 mass% (concentration ratio 105.2%). Joining judgment is consistent with In the same manner as in the example of sample A, it was judged as "good" because it obtained a good result in which no poor joining occurred at all.

The target Sn content (target value) of the sample D system is 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)

Table 9 summarizes the results of the above-mentioned Example of Sample A, Example of Sample B, Example of Sample C, and Example of Sample D. The concentration ratio of Sn is 72.2-137.6 which is mass%. Here, the sphericity of the Cu core balls produced in the example of the sample A, the example of the sample B, the example of the sample C, and the example of the sample D was measured, and the results were all 0.99 or more, and satisfied 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)

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

As explained above, in each of Examples A to D, since the Sn in the solder layer is homogeneous, the Pb of the solder layer is homogeneous. The film thickness of the solder layer includes Sn and Pb on the inner and outer sides. In the whole area, the ratio of Sn and Pb concentration is within the predetermined range. Therefore, the Sn and Pb in the solder layer are homogeneous. The Cu core ball of the present invention does not melt earlier on the inner peripheral side 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 bombarded. The situation of flying and so on.

In addition, since the Sn and Pb of the solder layer are homogeneous, and the Cu core ball can be melted almost uniformly on the entire surface, there is almost no time difference in the melting timing in the solder layer. As a result, since the positional shift of the Cu core balls due to the shifting of the melting timing does not occur, there is no risk of short circuit between the electrodes due to the shifting of the position. 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 substrate 50‧‧‧welding head 60‧‧‧Electronic parts

Fig. 1 is a diagram showing a Cu core ball related to the first embodiment of the present invention.

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

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

Figure 4 is an enlarged cross-sectional view of the Cu core ball.

Fig. 5 is a graph showing the relationship between the heating time and lightness when Cu balls of the examples and the comparative examples are heated at 200°C.

Fig. 6 is an explanatory diagram showing an example of a method of measuring the Sn concentration distribution of Cu core balls.

1‧‧‧Cu Ball

3‧‧‧Solder layer

11A‧‧‧Cu core ball

Claims (22)

A Cu core ball comprising: a Cu ball; and a solder layer covering the surface of the Cu ball, wherein the Cu ball is at least one of Fe, Ag, and Ni in a total content of 5.0 mass ppm or more and 50.0 mass ppm or less, S The content of P is 0 mass ppm or more and 1.0 mass ppm or less, the P content is 0 mass ppm or more and less than 3.0 mass ppm, and the balance is Cu and other impurity elements. The purity of the above Cu ball is 99.995% by mass or more and 99.9995 Mass% or less, the sphericity of the Cu ball is 0.95 or more, and the solder layer is a (Sn-Pb)-based solder alloy containing Sn and Pb. For example, the Cu core ball of the first item in the scope of patent application, wherein the content of Pb in the solder layer is more than 0% by mass and less than 95.0% by mass, and Sn is the balance. For example, the Cu core ball of 1 or 2 in the scope of the patent application, wherein the solder layer is composed of a (Sn-Pb)-based solder alloy containing Sn and 37.0% by mass or more and 95.0% by mass or less of Pb, and is contained in the solder The concentration ratio (%) of Sn in the layer is based on the concentration ratio (%) = (measured value (mass%)/target content (mass%)) × 100, or concentration ratio (%) = (average value of the measured value ( When expressed by mass%)/target content (mass%))×100, the above concentration ratio is in the range of 70.0~140.0%. For example, the Cu core ball of 1 or 2 in the scope of the patent application, wherein the solder layer is composed of a (Sn-Pb)-based solder alloy containing Sn and 37.0% by mass or more and 95.0% by mass or less of Pb, and is contained in the solder The concentration ratio (%) of Sn in the layer, with the concentration ratio (%)=(measured value (mass%)/target content (mass%))×100, or When the concentration ratio (%) = (average of the measured value (mass%)/target content (mass%)) × 100, the above concentration ratio is in the range of 90.0~110.0%. For example, the Cu core ball of item 1 or 2 in the scope of patent application, the sphericity of the Cu ball is 0.98 or more. For example, the Cu core ball of item 1 or 2 in the scope of patent application, the true sphericity of the Cu ball is 0.99 or more. For example, the Cu core ball in the third item of the scope of patent application, the sphericity of the Cu ball is above 0.98. For example, the Cu core ball of item 4 of the scope of patent application, in which the sphericity of the Cu ball is above 0.98. For example, the Cu core ball of the first or second item in the scope of patent application, in which the α-ray dose is less than 0.0200 cph/cm ² . For example, the Cu core ball of the first or second item in the scope of patent application, in which the α-ray dose is less than 0.0010 cph/cm ² . For example, the Cu core ball of item 1 or 2 of the scope of patent application has a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with the solder layer, and the sphericity of the Cu core ball is 0.95 or more. For example, the Cu core ball according to the third item of the patent application has a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with the solder layer, and the sphericity of the Cu core ball is 0.95 or more. For example, the Cu core ball according to the fourth item of the patent application has a metal layer covering the surface of the Cu ball, the surface of the metal layer is covered with the solder layer, and the sphericity of the Cu core ball is 0.95 or more. For example, the Cu core ball in item 11 of the scope of patent application, the sphericity of the Cu core ball is 0.98 or more. For example, the Cu core ball of item 11 in the scope of patent application, the Cu core ball has a true sphericity of 0.99 or more. For example, the Cu core ball of item 11 in the scope of patent application, in which the alpha radiation is less than 0.0200 cph/cm ² . For example, the Cu core ball of item 11 in the scope of patent application, in which the alpha radiation is less than 0.0010 cph/cm ² . For example, the Cu core ball of item 1 or 2 of the scope of patent application, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. For example, the Cu core ball of item 11 in the scope of patent application, wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less. A welding joint that uses any of the Cu core balls of items 1 to 19 in the scope of patent application. A solder paste that uses any of the Cu core balls of items 1 to 19 in the scope of patent application. A foam solder using any of the Cu core balls of items 1 to 19 in the scope of patent application.

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