JP2019214761A - Cu core ball, solder joint, solder paste and foam solder - Google Patents

Abstract

To provide a Cu core ball in which a metal layer covers a Cu ball which realizes a high sphericity and a low hardness and suppresses the discoloration.SOLUTION: The Cu core ball 11A contains a Cu ball 1 and a solder layer 3 for covering a surface of the Cu ball 1. The Cu ball 1 contains at least one selected from Fe, Ag, and Ni in a total amount of 5.0 or more to 50.0 ppm by mass or lower, S in an amount of 0 or more to 1.0 ppm by mass or lower, P in an amount of 0 or more to less than 3.0 ppm by mass, and remainder of Cu and inevitable impurities. The Cu ball 1 has a purity which is 99.995% or higher and 99.9995% by mass or lower, and a sphericity which is 0.95 or higher. The solder layer is an (Sn-Pb) solder alloy containing Sn and Pb.SELECTED DRAWING: Figure 1

Description

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

  2. Description of the Related Art In recent years, with the development of small information devices, electronic components to be mounted have been rapidly downsized. For the electronic components, a ball grid array (hereinafter, referred to as “BGA”) having electrodes provided on the back surface is applied in order to cope with narrowing of connection terminals and reduction of mounting area due to demand for miniaturization. .

  Electronic components to which BGA is applied include, for example, semiconductor packages. In a semiconductor package, a semiconductor chip having electrodes is sealed with a resin. Solder bumps are formed on the electrodes of the semiconductor chip. The solder bump is formed by joining a solder ball to an electrode of a semiconductor chip. A semiconductor package to which BGA is applied is mounted on a printed circuit board by bonding a solder bump melted by heating and a conductive land of the printed circuit board. Further, in order to meet the demand for higher density mounting, three-dimensional high density mounting in which semiconductor packages are stacked in the height direction is being studied.

  High-density mounting of electronic components may cause a soft error in which stored contents are rewritten when α rays enter a memory cell of a semiconductor integrated circuit (IC). Therefore, in recent years, low α-ray solder materials and Cu balls with a reduced content of radioisotopes have been developed. Patent Literature 1 discloses a Cu ball containing Pb and Bi, having a purity of 99.9% or more and 99.995% or less and a low α dose. 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.

  By the way, the Cu ball has a large Vickers hardness when the crystal grains are fine, so that the durability against external stress is reduced and the drop impact resistance is deteriorated. Therefore, Cu balls used for mounting electronic components are required to have a predetermined softness, that is, a Vickers hardness equal to or lower than a predetermined value.

  In order to produce soft Cu balls, it is customary to increase the purity of Cu. This is because the impurity element functions as a crystal nucleus in the Cu ball, so that when the impurity element is reduced, the crystal grains grow larger, and as a result, the Vickers hardness of the Cu ball decreases. However, increasing the purity of the Cu ball lowers the sphericity of the Cu ball.

  If the sphericity of the Cu ball is low, self-alignment may not be ensured when the Cu ball is mounted on the electrode, and the height of the Cu ball may become uneven during the mounting of the semiconductor chip, resulting in poor connection. May cause

  Patent Literature 3 discloses a Cu ball having a Cu content of more than 99.995%, a total of P and S mass ratios of 3 ppm or more and 30 ppm or less, and having suitable sphericity and Vickers hardness. ing.

  In addition, when a semiconductor package on which three-dimensional high-density mounting is performed is a BGA, and a solder ball is placed on an electrode of a semiconductor chip and reflow processing is performed, the solder ball may be crushed by the weight of the semiconductor package. . If such a situation occurs, the solder may protrude from the electrodes, and the electrodes may contact each other, causing a short circuit between the electrodes.

  In order to prevent such a short circuit accident, there has been proposed a solder bump which is not crushed by its own weight or deformed when the solder is melted. Specifically, it has been proposed to use a ball formed of metal or the like as a core and use a core material obtained by coating the core with solder as a solder bump.

Japanese Patent No. 5435182 Japanese Patent No. 5585751 Japanese Patent No. 6256616

  However, it has been newly found that a Cu ball containing a predetermined amount or more of S has a problem that sulfides and sulfur oxides are formed at the time of heating and are easily discolored. Discoloration of the Cu ball causes deterioration of wettability, and deterioration of wettability causes non-wetting and deterioration of self-alignment. As described above, the Cu ball that is easily discolored is not suitable for coating with the metal layer because the adhesion between the Cu ball surface and the metal layer is reduced, and the oxidation and reactivity of the metal layer surface are increased. On the other hand, when the sphericity of the Cu ball is low, the sphericity of the Cu core ball in which the Cu ball is covered with the metal layer is also low.

  Therefore, the present invention provides a Cu core ball using a Cu ball that achieves high sphericity and low hardness and suppresses discoloration, and a solder joint, a solder paste, and a foam solder using the Cu core ball. The purpose is to provide.

The present invention is as follows.
(1) A Cu ball and a solder layer covering the surface of the Cu ball. The Cu ball has a total content of at least one of Fe, Ag and Ni of 5.0 mass ppm or more and 50.0 mass. ppm or less, the 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. Yes, the purity of the Cu ball 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 contains Sn and Pb (Sn-Pb). Cu core ball which is a solder alloy.
(2) The Cu core ball according to the above (1), wherein the solder layer has a Pb content of more than 0% by mass and 95.0% by mass or less and Sn as the balance.
(3) The solder layer is made of a (Sn-Pb) -based solder alloy containing Sn and Pb of 37.0% by mass or more and 95.0% by mass or less, and the concentration ratio (%) of Sn contained in the solder layer. The concentration ratio (%) = (measured value (mass%) / target content (mass%)) × 100 or the concentration ratio (%) = (mean value of measured values (mass%) / target) (% By mass) × 100, the Cu core ball according to the above (1) or (2), wherein the concentration ratio is in the range of 70.0 to 140.0%.
(4) The solder layer is made of a (Sn-Pb) -based solder alloy containing Sn and Pb of 37.0 mass% or more and 95.0 mass% or less, and the concentration ratio (%) of Sn contained in the solder layer. The concentration ratio (%) = (measured value (mass%) / target content (mass%)) × 100 or the concentration ratio (%) = (mean value of measured values (mass%) / target) The content (% by mass) of the Cu core ball according to the above (1) or (2), wherein the concentration ratio is in the range of 90.0 to 110.0%.
(5) The Cu core ball according to any one of (1) to (4), wherein the sphericity is 0.98 or more.
(6) The Cu core ball according to any one of (1) to (4), wherein the sphericity is 0.99 or more.
(7) The Cu core ball according to any one of (1) to (6), wherein the α dose is 0.0200 cph / cm ² or less.
(8) The Cu core ball according to any one of (1) to (6), wherein the α dose is 0.0010 cph / cm ² or less.
(9) The method according to any one of (1) to (8), further including a metal layer covering the surface of the Cu ball, wherein the surface of the metal layer is coated with a solder layer and having a sphericity of 0.95 or more. Cu core ball.
(10) The Cu core ball according to (9), wherein the sphericity is 0.98 or more.
(11) The Cu core ball according to (9), wherein the sphericity is 0.99 or more.
(12) The Cu core ball according to any one of (9) to (11), wherein the α dose is 0.0200 cph / cm ² or less.
(13) The Cu core ball according to any of (9) to (11), wherein the α dose is 0.0010 cph / cm ² or less.
(14) The Cu core ball according to any one of the above (1) to (13), wherein the diameter of the Cu ball is 1 μm or more and 1000 μm or less.
(15) A solder joint using the Cu core ball according to any of (1) to (14).
(16) A solder paste using the Cu core ball according to any of (1) to (14).
(17) A foam solder using the Cu core ball according to any of (1) to (14).

  ADVANTAGE OF THE INVENTION According to this invention, Cu ball implement | achieves high sphericity and low hardness, and the discoloration of Cu ball is suppressed. By realizing the high sphericity of the Cu ball, the high sphericity of the Cu core ball in which the Cu ball is covered with the metal layer can be realized, and the self-alignment property when the Cu ball core is mounted on the electrode can be secured. At the same time, variation in the height of the Cu core ball can be suppressed. Also, by realizing the low hardness of the Cu ball, even a Cu core ball in which the Cu ball is covered with a metal layer can improve the drop impact resistance. Further, since discoloration of the Cu ball is suppressed, adverse effects on the Cu ball due to sulfides and sulfur oxides can be suppressed, which is suitable for coating with a metal layer and has good wettability.

It is a figure showing a Cu core ball of a 1st embodiment concerning the present invention. It is a figure showing a Cu core ball of a 2nd embodiment concerning the present invention. It is a figure showing the example of composition of the electronic component using the Cu core ball of each embodiment concerning the present invention. It is an expanded sectional view of a Cu core ball. It is the table | surface which shows the relationship between the heating time and lightness which heated the Cu ball of an Example and a comparative example at 200 degreeC. It is explanatory drawing which shows an example of the method of measuring the density | concentration distribution of Cu of Cu core ball.

  The present invention is described in more detail below. In the present specification, the unit (ppm, ppb, and%) relating to the composition of the metal layer of the Cu core ball represents the ratio (mass ppm, mass ppb, and mass%) to the mass of the metal layer unless otherwise specified. The unit (ppm, ppb, and%) relating to the composition of the Cu ball represents the ratio (ppm by mass, ppb, and% by mass) to the mass of the Cu ball unless otherwise specified.

  FIG. 1 shows an example of the configuration of a Cu core ball 11A according to the first embodiment of the present invention. As shown in FIG. 1, a Cu core ball 11 </ b> A according to the first embodiment of the present invention includes a Cu ball 1 and a solder layer 3 that covers the surface of the Cu ball 1.

  FIG. 2 shows an example of the configuration of the Cu core ball 11B according to the second embodiment of the present invention. As shown in FIG. 2, the Cu core ball 11B according to the second embodiment of the present invention has a Cu ball 1 and at least one selected from Ni, Co, Fe, and Pd covering the surface of the Cu ball 1. And a 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 the semiconductor chip 10 is mounted on a printed board 40 using the Cu core ball 11A or Cu core ball 11B according to the embodiment of the present invention. As shown in FIG. 3, when the flux is applied to the electrode 100 of the semiconductor chip 10, the molten solder layer 3 spreads and spreads on the electrode 100 of the semiconductor chip 10. Has been implemented. In this example, a structure in which the Cu core ball 11A or the Cu core ball 11B is mounted on the electrode 100 of the semiconductor chip 10 is referred to as a solder bump 30. The solder bumps 30 of the semiconductor chip 10 are joined to the electrodes 41 of the printed circuit board 40 via the molten solder layer 3 or the solder in which the solder paste applied to the electrodes 41 is melted. In this example, a structure in which the solder bumps 30 are mounted on the electrodes 41 of the printed circuit board 40 is referred to as a solder joint 50.

  In the Cu core balls 11A and 11B of the respective embodiments, the Cu ball 1 has a total content of at least one of Fe, Ag, and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less. 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 is 4N5 (99.995 mass%) or more and 5N5 (99.9995 mass%) or less, and the sphericity is 0.95 or more.

  In the Cu core ball 11A of the first embodiment according to the present invention, the sphericity of the Cu core ball 11A can be increased by increasing the sphericity of the Cu ball 1 covered with the solder layer 3. it can. Further, the Cu core ball 11B of the second embodiment according to the present invention increases the sphericity of the Cu ball 1 covered with the metal layer 2 and the solder layer 3 to increase the sphericity of the Cu core ball 11B. The degree can be increased. Hereinafter, a preferred embodiment of the Cu ball 1 constituting the Cu core balls 11A and 11B will be described.

-Sphericity of Cu ball: 0.95 or more In the present invention, the sphericity indicates a deviation from a sphere. The sphericity is an arithmetic average value calculated when the diameter of each of the 500 Cu balls is divided by the major axis, and the closer the value is to the upper limit of 1.00, the closer to a true sphere. The sphericity is obtained by various methods such as a least square center method (LSC method), a minimum area center method (MZC method), a maximum inscribed center method (MIC method), and a minimum circumscribed center method (MCC method). . In the present invention, the length of the major axis and the length of the diameter refer to the length measured by an Ultra Quick Vision, ULTRA QV350-PRO measuring device manufactured by Mitutoyo Corporation.

  The Cu ball 1 preferably has a sphericity of 0.95 or more, more preferably 0.98 or more, and more preferably 0.99 or more from the viewpoint of maintaining an appropriate space between the substrates. Is even more preferred. If the sphericity of the Cu ball 1 is less than 0.95, the Cu ball 1 has an irregular shape, so that a bump having an uneven height is formed at the time of bump formation, and the possibility of occurrence of bonding failure increases. If the sphericity is 0.95 or more, the Cu ball 1 does not melt at the soldering temperature, so that the height variation in the solder joint 50 can be suppressed. Thereby, the bonding failure between the semiconductor chip 10 and the printed board 40 can be reliably prevented.

-Purity of Cu ball: 99.995 mass% or more and 99.9995 mass% or less In general, Cu having a low purity contains, in Cu, an impurity element serving as a crystal nucleus of the Cu ball 1 as compared with Cu having a high purity. The sphericity is increased because it can be secured. On the other hand, the Cu balls 1 with low purity have deteriorated electrical conductivity and thermal conductivity.

  Therefore, if the purity of the Cu ball 1 is not less than 99.995% by mass (4N5) and not more than 99.9995% by mass (5N5), sufficient sphericity can be ensured. Further, when the purity of the Cu ball 1 is 4N5 or more and 5N5 or less, the α dose can be sufficiently reduced, and the deterioration of the electrical conductivity and the thermal conductivity of the Cu ball 1 due to the decrease in the purity can be suppressed.

  When manufacturing the Cu ball 1, a Cu material, which is an example of a metal material formed in small pieces of a predetermined shape, is melted by heating, and the molten Cu becomes spherical due to surface tension, and solidifies by rapid cooling to become the Cu ball 1. . In the process of solidifying molten Cu from a liquid state, crystal grains grow in spherical molten Cu. At this time, if the amount of the impurity element is large, the impurity element becomes a crystal nucleus and the growth of crystal grains is suppressed. Therefore, the spherical molten Cu becomes a Cu ball 1 having a high sphericity due to the fine crystal grains whose growth is suppressed. On the other hand, when the impurity element is small, relatively few crystal nuclei are formed, and the crystal grows in a certain direction without suppressing the grain growth. As a result, the spherical molten Cu partially protrudes and solidifies to lower the sphericity. Examples of the impurity element include Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au, U, and Th.

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

-Total of the 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, at least among Fe, Ag and Ni It is preferable that the total content of one kind is 5.0 mass ppm or more and 50.0 mass ppm or less. That is, when any one of Fe, Ag, and Ni is contained, the content of one of them is preferably 5.0 mass ppm or more and 50.0 mass ppm or less, and among Fe, Ag, and Ni, When two or more kinds are contained, the total content of the two or more kinds is preferably 5.0 mass ppm or more and 50.0 mass ppm or less. Since Fe, Ag and Ni become crystal nuclei at the time of melting in the manufacturing process of the Cu ball 1, it is possible to manufacture the Cu ball 1 having a high sphericity if a certain amount of Fe, Ag or Ni is contained in Cu. it can. Therefore, at least one of Fe, Ag, and Ni is an important element for estimating the content of the impurity element. Further, when the total content of at least one of Fe, Ag and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, discoloration of the Cu ball 1 can be suppressed, and the Cu ball 1 The desired Vickers hardness can be realized without performing an annealing step of gradually recrystallizing the Cu ball 1 by gradually cooling after gradually heating.

・ S content is 0 mass ppm or more and 1.0 mass ppm or less The Cu ball 1 containing a predetermined amount or more of S forms sulfides and sulfur oxides when heated, easily discolors, and has a low wettability. , S content must be 0 mass ppm or more and 1.0 mass ppm or less. The lighter the surface of the Cu ball becomes, the darker the Cu ball 1 in which a large amount of sulfides and sulfur oxides are formed. Therefore, as will be described in detail later, if the result of measuring the lightness of the Cu ball surface is equal to or less than a predetermined value, the formation of sulfides and sulfur oxides is suppressed, and it can be determined that the wettability is good. .

-P content is 0 mass ppm or more and less than 3.0 mass ppm P may change to phosphoric acid or become a Cu complex to adversely affect the Cu ball 1. Further, since the Cu ball 1 containing a predetermined amount of P has a high hardness, the P content is preferably 0 mass ppm or more and less than 3.0 mass ppm, and is less than 1.0 mass ppm. More preferred.

-Other impurity elements Other than the above-mentioned impurity elements contained in the Cu ball 1, impurity elements such as Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, and Au (hereinafter, "other impurity elements") ) Is preferably 0 mass ppm or more and less than 50.0 mass ppm.

  The Cu ball 1 contains at least one of Fe, Ag, and Ni as an essential element, as described above. However, since the Cu ball 1 cannot prevent mixing of elements other than Fe, Ag, and Ni with the current technology, the Cu ball 1 substantially contains impurity elements other than Fe, Ag, and Ni. However, when the content of the other impurity elements is less than 1 mass ppm, the effects and effects due to the addition of each element are unlikely to appear. Also, 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 lower than the detection limit depending on the analyzer. Therefore, if the total content of at least one of Fe, Ag and Ni is 50 mass ppm, and if the content of other impurity elements is less than 1 mass ppm, the purity of the Cu ball 1 is substantially reduced. It is 4N5 (99.995 mass%). When the total content of at least one of Fe, Ag, and Ni is 5 mass ppm, and when the content of other impurity elements is less than 1 mass ppm, the purity of the Cu ball 1 is substantially reduced. 5N5 (99.9995% by mass).

-Vickers hardness of Cu ball: 55.5 HV or less Vickers hardness of Cu ball 1 is preferably 55.5 HV or less. When the Vickers hardness is large, the durability against external stress is reduced, the drop impact resistance is deteriorated, and cracks are easily generated. Further, when an auxiliary force such as pressure is applied during the formation of bumps or joints for three-dimensional mounting, use of a hard Cu ball may cause crushing of the electrode. Furthermore, when the Vickers hardness of the Cu ball 1 is large, the crystal grains become smaller than a certain value, which leads to deterioration of electric conductivity. When the Vickers hardness of the Cu ball 1 is 55.5 HV or less, the drop impact resistance is good, cracks can be suppressed, electrode crushing and the like can be suppressed, and furthermore, deterioration of electric conductivity can be suppressed. In this embodiment, the lower limit of the Vickers hardness may be more than 0 HV, and is preferably 20 HV or more.

-Α dose of Cu ball: 0.0200 cph / cm ² or less In order to set an α dose at which soft error does not matter in high-density mounting of electronic components, the α dose of Cu ball 1 is 0.0200 cph / cm ² or less. It is preferable that The α dose is preferably 0.0100 cph / cm ² or less, more preferably 0.0050 cph / cm ² or less, and still more preferably 0.0020 cph, from the viewpoint of suppressing soft errors in further high-density mounting. / Cm ² or less, and most preferably 0.0010 cph / cm ² or less. In order to suppress soft errors due to α dose, the content of radioisotopes such as U and Th is preferably less than 5 mass ppb.

Discoloration resistance: lightness of 55 or more The Cu ball 1 preferably has lightness of 55 or more. Lightness and is a L ^* a ^* b ^* L ^* value of color system. Since the lightness of the Cu ball 1 on the surface of which sulfides and sulfur oxides derived from S are low, it can be said that sulfides and sulfur oxides are suppressed if the lightness is 55 or more. The Cu ball 1 having a brightness of 55 or more has good wettability during mounting. On the other hand, if the lightness of the Cu ball 1 is less than 55, it can be said that the Cu ball 1 does not sufficiently suppress the formation of sulfides and sulfur oxides. The sulfides and sulfur oxides have an adverse effect on the Cu ball 1 and also deteriorate the wettability when the Cu ball 1 is directly bonded on the electrode. Deterioration of wettability causes non-wetting and deterioration of self-alignment.

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

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

-Solder layer The Cu core balls 11A and 11B of the respective embodiments according to the present invention are obtained by coating the Cu balls 1 with a solder layer 3 made of a solder alloy containing Sn and Pb as essential elements. In particular, the Cu core balls 11A and 11B of each embodiment according to the present invention include a Cu core ball in which the distribution of Pb in the solder layer 3 is uniform, and a solder joint, a solder paste, and a foam solder using the same. Is provided.

  The composition of the solder layer 3 of the embodiment according to the present invention is composed of a (Sn-Pb) -based alloy containing Sn and Pb. Regarding the content of Pb, if the Pb content is more than 0% by mass and 95.0% by mass or less based on the whole alloy, and if the Pb amount is more than 0% by mass and 95.0% by mass or less, The concentration ratio of Pb can be controlled within a predetermined range. Here, if the distribution of Pb in the solder layer 3 is uniform, the distribution of Sn is also uniform. Similarly, if the distribution of Sn in the solder layer 3 is uniform, the distribution of Pb is also uniform. In the present invention, there is a composition example in which the Pb content is larger than the Sn content, and in consideration of such a case, in the following description, the distribution of Pb is determined by the fact that the distribution of Sn is uniform. Explain that it is homogeneous.

  If the Pb content is in the range of 37.0 to 95.0 mass% with respect to the entire alloy, that is, the Sn content is in the range of 5.0 to 63.0 mass% with respect to the entire alloy, the Sn concentration is high. The ratio can be controlled within a predetermined range of 70.0 to 140.0%, and the distribution of Sn and Pb in the solder layer 3 can be made uniform.

  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 the concentration ratio is 3.61% by mass. (Concentration ratio 72.2%) to 6.88 mass% (concentration ratio 137.6%), and the Sn concentration ratio can be controlled within a predetermined range of 70.0 to 140.0%. The Sn distribution and the Pb distribution in the layer 3 can be made uniform.

  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 the concentration ratio is 9.74% by mass. (Concentration ratio 97.4%) to 11.20 mass% (concentration ratio 112.0%), and the Sn concentration ratio can be controlled within a predetermined range of 70.0 to 140.0%. The Sn distribution and the Pb distribution in the layer 3 can be made uniform.

  Further, 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 the concentration ratio is 61.30% by mass. (Concentration ratio 97.3%) to 70.02% by mass (concentration ratio 111.1%), and the Sn concentration ratio can be controlled within a predetermined range of 70.0 to 140.0%. The Sn distribution and the Pb distribution in the layer 3 can be made uniform.

  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 the concentration ratio is 55.83% by mass. (Concentration ratio 93.1%) to 63.10% by mass (concentration ratio 105.2%), and the Sn concentration ratio can be controlled within a predetermined range of 70.0 to 140.0%. The Sn distribution and the Pb distribution in the layer 3 can be made uniform.

Note that the allowable range is a range within which soldering such as bump formation can be performed without any problem as long as the range is within this range. The concentration ratio (%) is a ratio of a measured value (% by mass) to a target content (% by mass) or a ratio of an average value (% by mass) of the measured value to a target content (% by mass) ( %). That is, the concentration ratio (%)
Concentration ratio (%) = (measured value (% by mass) / target content (% by mass)) × 100
Or
Concentration ratio (%) = (average value of measured values (% by mass) / target content (% by mass)) × 100
Can be expressed as

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

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

  As described above, the contents of Sn and Pb in the solder layer 3 are 3.61% by mass (concentration ratio: 72.2%) to 6.6% as an allowable range with respect to the target value of 5.0% by mass of Sn. It is preferably about 88% by mass (concentration ratio: 137.6%). Further, it is preferable that the allowable range is about 9.74% by mass (concentration ratio: 97.4%) to 11.20% by mass (concentration ratio: 112.0%) with respect to the target value of 10.0% by mass of Sn. Further, the allowable range is preferably about 61.30% by mass (concentration ratio 97.3%) to 70.02% by mass (concentration ratio 111.1%) with respect to the target value of Sn of 63.0% by mass. Further, the allowable range is preferably about 55.83% by mass (concentration ratio 93.1%) to 63.10% by mass (concentration ratio 105.2%) with respect to the target value of 60.0% by mass of Sn.

  The thickness of the solder layer 3 varies depending on the particle size of the Cu ball 1, but is preferably 100 μm or less on one side in the radial direction to secure a sufficient amount of solder joint. The solder layer can be formed by an electroplating method or a hot-dip plating method, but is preferably formed by an electroplating method in order to suppress a decrease in the sphericity of the Cu core ball.

  In order to form a solder layer having a uniform Sn and Pb concentration distribution, a predetermined DC voltage is applied between the anode electrode and the cathode electrode, and the Pb concentration in the liquid is made uniform while oscillating the Cu ball. By performing the electroplating process so as to satisfy the following condition, the concentration of the plating solution is controlled to be constant during the formation of the solder plating layer.

  During the formation of the solder layer 3 by the electroplating process in which the concentration of the plating solution is controlled to be constant during the formation of the solder plating layer, the thickness of the solder layer 3 is monitored one by one. The Cu core balls, which are sequentially increased by value, are collected as samples each time. The collected sample is washed and dried, and the particle size is measured.

  When the Pb content in the solder layer when the particle size of the Cu core ball at the measurement timing is a target value is sequentially measured, even if the solder layer is sequentially increased by a predetermined thickness, the Pb The content was found to be almost the same value as the content immediately before. Therefore, it can be understood that the Pb concentration distribution is uniform (uniform) with respect to the plating thickness, and there is no concentration gradient. As described above, although the film thickness can be controlled uniformly, the problem of electroplating that the concentration becomes non-uniform is solved by controlling the Pb concentration in the solder layer so that the Pb concentration ratio falls within a predetermined range. By doing so, a Cu core ball having a solder layer in which Pb is uniformly distributed is obtained.

  When the content of Pb is larger than that of Sn, a predetermined DC voltage is applied between the anode electrode and the cathode electrode to form a solder layer in which the concentration distribution of Sn and Pb is uniform, By performing electroplating while adjusting the Sn concentration in the solution to be uniform while oscillating the Cu ball, the concentration of the plating solution is controlled to be constant during the formation of the solder plating layer.

  When the Sn content in the solder layer when the particle size of the Cu core ball at the measurement timing is the target value is sequentially measured, even if the solder layer is sequentially increased by a predetermined thickness, the Sn content at that time is increased. The content was found to be almost the same value as the content immediately before. Therefore, it can be understood that the Sn concentration distribution is uniform (uniform) with respect to the plating thickness and there is no concentration gradient. As described above, although the film thickness can be controlled uniformly, the problem of electroplating in which the concentration becomes non-uniform is controlled by controlling the Sn concentration in the solder layer so that the Sn concentration ratio falls within a predetermined range. By doing so, a Cu core ball having a solder layer in which Sn is uniformly distributed is obtained.

  FIG. 4 is an enlarged sectional view of the Cu core ball. FIG. 4 shows a Cu core ball 11B in which the Cu ball 1 is covered with the metal layer 2 and the metal layer 2 is covered with the solder layer 3. As is clear from FIG. 4, the process in which the solder layer 3 grew while Sn and Pb were homogeneously mixed was well understood.

  Also, the closer the outermost surface of the solder layer 3 covering the Cu core balls 11A and 11B is to a single metal state, the larger the crystal grains, and thus the sphericity of the Cu core balls tends to decrease. On the other hand, since Sn and Pb in the solder layer are in a state of being substantially uniformly distributed, the outermost surface of the solder layer is not a single metal but an alloy state, and the crystal grains are small. Thereby, the sphericity of the Cu core ball is high and is 0.99 or more. When the sphericity of the Cu core ball is 0.95 or more, when the Cu core ball is mounted on the electrode and reflow is performed, the displacement of the Cu core ball is suppressed, and the self-alignment property is improved.

  Since the concentrations of Sn and Pb in the solder layer maintain almost the same state even when the thickness of the solder layer grows, the Sn and Pb in the solder layer grow in a state of being substantially uniformly distributed. It became clear. The plating process is performed in a state where the Sn and Pb concentrations in the plating solution are made uniform so that the Sn and Pb concentrations fall within expected values. In this example, the target value of 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, so that the target value is reached. Then, the Sn concentration in the plating solution is controlled.

  In order to keep the concentration distribution of Sn and Pb in the solder layer within a desired value, plating is performed while controlling voltage and current. By such a plating treatment, the distribution of Sn and Pb in the solder layer can be maintained at a desired value.

  The Cu core balls 11A and 11B may be configured by using a low α dose solder alloy for the solder layer 3 to form the low α ray Cu core balls 11A and 11B.

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

-Metal layer The metal layer 2 includes, for example, a Ni plating layer, a Co plating layer, an Fe plating layer, a Pd plating layer, or a plating layer (single layer or plural layers) containing two or more elements of Ni, Co, Fe, and Pd. Become. When the Cu core ball 11B is used as a solder bump, the metal layer 2 remains without melting at the soldering temperature and contributes to the height of the solder joint. Therefore, the sphericity is high and the variation in diameter is small. Be composed. In addition, from the viewpoint of suppressing the soft error, the configuration is such that the α dose is reduced.

The composition and thickness of the metal layer The composition of the metal layer 2 is 100% Ni, Co, Fe, and Pd when the metal layer 2 is composed of a single Ni, Co, Fe, or Pd, except for inevitable impurities. It is. Further, the metal used for the metal layer 2 is not limited to a single metal, and an alloy in which two or more elements are combined from Ni, Co, Fe, or Pd may be used. Further, the metal layer 2 is composed of a single layer made of Ni, Co, Fe or Pd, and a plurality of layers formed by appropriately combining layers made of an alloy of two or more of Ni, Co, Fe or Pd. May be configured. The thickness T2 of the metal layer 2 is, for example, 1 μm to 20 μm.

Α dose of Cu core ball: 0.0200 cph / cm ² or less The α dose of Cu core ball 11A of the first embodiment of the present invention and Cu core ball 11B of the second embodiment is 0.0200 cph / cm ^2. cm ² or less. This is an amount of α that does not cause a soft error in high-density mounting of electronic components. The α dose of the Cu core ball 11A of the first embodiment according to the present invention is achieved when the α dose of the solder layer 3 constituting the Cu core ball 11A is 0.0200 cph / cm ² or less. Therefore, since the Cu core ball 11A of the first embodiment according to the present invention is covered with such a solder layer 3, it exhibits a low α dose. The α dose of the Cu core ball 11B of the second embodiment according to the present invention is achieved by setting the α dose of the metal layer 2 and the solder layer 3 constituting the Cu core ball 11B to 0.0200 cph / cm ² or less. Is done. Therefore, the Cu core ball 11B of the second embodiment according to the present invention exhibits a low α dose since it is covered with the metal layer 2 and the solder layer 3. The α dose is preferably 0.0100 cph / cm ² or less, more preferably 0.0050 cph / cm ² or less, and still more preferably 0.0020 cph, from the viewpoint of suppressing soft errors in further high-density mounting. / Cm ² or less, and most preferably 0.0010 cph / cm ² or less. The U and Th contents of the metal layer 2 and the solder layer 3 are each 5 ppb or less in order to keep the α dose of the Cu ball 1 at 0.0200 cph / cm ² or less. From the viewpoint of suppressing soft errors in current or future high-density mounting, the contents of U and Th are each preferably 2 ppb or less.

The sphericity of the Cu ball core: 0.95 or more The Cu core ball 11A according to the first embodiment of the present invention in which the Cu ball 1 is covered with the solder layer 3, and the Cu ball 1 is the metal layer 2 and the solder The sphericity of the Cu core ball 11B according to the second embodiment of the present invention covered with the layer 3 is preferably 0.95 or more, and more preferably 0.98 or more. , 0.99 or more. If the sphericity of the Cu core balls 11A and 11B is less than 0.95, the Cu core balls 11A and 11B have an irregular shape. Therefore, when the Cu core balls 11A and 11B are mounted on the electrodes and reflow is performed, Cu The core balls 11A and 11B are displaced, and the self-alignment is deteriorated. When the sphericity of the Cu core balls 11A and 11B is 0.95 or more, self-alignment when the Cu core balls 11A and 11B are mounted on the electrode 100 of the semiconductor chip 10 or the like can be ensured. Since the sphericity of the Cu ball 1 is also 0.95 or more, the Cu core balls 11A and 11B have a height in the solder joint 50 because the Cu ball 1 and the metal layer 2 do not melt at the soldering temperature. Can be suppressed. Thereby, the bonding failure between the semiconductor chip 10 and the printed board 40 can be reliably prevented.

-Barrier function of metal layer At the time of reflow, when Cu of the Cu ball diffuses in the solder (paste) used for joining the Cu core ball and the electrode, hard and brittle Cu ₆ Sn is present in the solder layer and the connection interface. ₅ , a large amount of Cu ₃ Sn intermetallic compound may be formed, cracks may develop when subjected to impact, and the connection may be broken. Therefore, in order to obtain a sufficient connection strength, it is preferable to suppress (barrier) the diffusion of Cu from the Cu ball into the solder. Therefore, in the Cu core ball 11B of the second embodiment, since the metal layer 2 functioning as a barrier layer is formed on the surface of the Cu ball 1, diffusion of Cu of the Cu ball 1 into the paste solder is suppressed. it can.

-Solder paste, foam solder, solder joint Also, a solder paste can be formed by including Cu core ball 11A or Cu core ball 11B in the solder. By dispersing the Cu core ball 11A or Cu core ball 11B in the solder, a foam solder can be formed. The Cu core ball 11A or Cu core ball 11B can also be used for forming a solder joint for joining between electrodes.

Next, an example of a method of manufacturing the Cu ball 1 will be described. As an example of a metal material, a Cu material is placed on a heat-resistant plate such as a ceramic (hereinafter, referred to as a “heat-resistant plate”) and heated in a furnace together with the heat-resistant plate. The heat-resistant plate is provided with a large number of circular grooves having a hemispherical bottom. The diameter and depth of the groove are appropriately set according to the particle size of the Cu ball 1, and are, for example, 0.8 mm in diameter and 0.88 mm in depth. Further, chip-shaped Cu materials obtained by cutting the Cu fine wires are put into the grooves of the heat-resistant plate one by one. The heat-resistant plate having the groove filled with the Cu material is heated to 1100 to 1300 ° C. in a furnace filled with an ammonia decomposition gas, and is heat-treated for 30 to 60 minutes. At this time, when the furnace temperature becomes equal to or higher than the melting point of Cu, the Cu material is melted and becomes spherical. Thereafter, the inside of the furnace is cooled, and the Cu balls 1 are rapidly cooled in the grooves of the heat-resistant plate to be formed.

  Further, as another method, an atomizing method in which molten Cu is dropped from an orifice provided at the bottom of the crucible and the droplet is rapidly cooled to room temperature (for example, 25 ° C.) to form a Cu ball 1 or heat, There is a method in which plasma is used to heat a Cu cut metal to 1000 ° C. or more to form a ball.

  In the method of manufacturing the Cu ball 1, a Cu material, which is a raw material of the Cu ball 1, may be subjected to a heat treatment at 800 to 1000 ° C. before forming the Cu ball 1.

  As a Cu material which is a raw material of the Cu ball 1, for example, a nugget material, a wire material, a plate material, or the like can be used. The purity of the Cu material may be more than 4N5 and 6N or less from the viewpoint of not lowering the purity of the Cu ball 1 too much.

  When a high-purity Cu material is used as described above, the holding temperature of the molten Cu may be reduced to about 1000 ° C. as in the related art without performing the above-described heat treatment. As described above, the above-described heat treatment may be omitted or changed as appropriate according to the purity of the Cu material and the α dose. Further, when the Cu ball 1 or the deformed Cu ball 1 having a high α dose is manufactured, the Cu ball 1 may be reused as a raw material, and the α dose can be further reduced.

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

  As a method of forming the metal layer 2 on the Cu ball 1, a known method such as an electroplating method can be adopted. For example, in the case of forming a Ni plating layer, a Ni plating solution is adjusted using Ni metal or a Ni metal salt for the Ni plating bath type, and the Cu ball 1 is immersed in the adjusted Ni plating solution. By depositing, a Ni plating layer is formed on the surface of the Cu ball 1. Further, as another method for forming the metal layer 2 such as the Ni plating layer, a known electroless plating method or the like can be adopted. When the solder layer 3 of the Sn alloy is formed on the surface of the metal layer 2, the above-described electroplating method or electroless plating method can be employed.

  EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. Cu balls of Examples 1 to 19 and Comparative Examples 1 to 12 were produced with the compositions shown in Tables 1 and 2 below, and the sphericity, Vickers hardness, α dose and discoloration resistance of the Cu balls were measured. .

  The Cu core balls of Examples 1A to 19A were prepared by coating the Cu balls of Examples 1 to 19 described above with a solder layer of the solder alloy of Composition Examples 1 to 4 shown in Table 3. Was measured for sphericity. Further, the Cu balls of Examples 1B to 19B were produced by coating the Cu balls of Examples 1 to 19 with a metal layer and a solder layer of the solder alloy of Composition Examples 1 to 4 shown in Table 4. The sphericity of the nuclear ball was measured.

  The Cu core balls of Comparative Examples 1A to 12A were prepared by coating the Cu balls of Comparative Examples 1 to 12 with a solder layer of the solder alloy of Composition Examples 1 to 4 shown in Table 5. Was measured for sphericity. The Cu balls of Comparative Examples 1B to 12B were prepared by coating the Cu balls of Comparative Examples 1 to 12 with a metal layer and a solder layer of the solder alloy of Composition Examples 1 to 4 shown in Table 6. The sphericity of the nuclear ball was measured.

  In the table below, numbers without units indicate mass ppm or mass ppb. Specifically, numerical values indicating the content ratios of Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, and Au in the table represent mass ppm. “<1” indicates that the content ratio of the corresponding impurity element to the Cu ball is less than 1 ppm by mass. The numerical values indicating the content ratio of U and Th in the table represent mass ppb. “<5” indicates that the content ratio of the corresponding impurity element to the Cu ball is less than 5 mass ppb. The “total amount of impurities” indicates the total ratio of impurity elements contained in the Cu ball.

-Preparation of Cu ball The preparation conditions of the Cu ball were examined. A nugget material was prepared as a Cu material as an example of a metal material. In Examples 1 to 13 and 19 and Comparative Examples 1 to 12, Cu materials having a purity of 6N were used, and Cu materials in Examples 14 to 18 having a purity of 5N were used. After putting each Cu material into the crucible, the temperature of the crucible was raised to 1200 ° C., heated for 45 minutes to melt the Cu material, and molten Cu was dropped from the orifice provided at the bottom of the crucible to form. The droplet was rapidly cooled to room temperature (18 ° C.) and formed into a Cu ball. As a result, Cu balls having an average particle diameter having values shown in the following tables were produced. Elemental analysis can be performed with high accuracy by using inductively coupled plasma mass spectrometry (ICP-MS analysis) or glow discharge mass spectrometry (GD-MS analysis). In this example, however, ICP-MS analysis was used. The ball diameter of the Cu ball was 250 μm in each of Examples 1 to 19 and Comparative Examples 1 to 12.

-Production of Cu core ball Using the Cu balls of Examples 1 to 19 described above, for Examples 1A to 19A, a solder layer formed by electroplating with a solder alloy of Composition Examples 1 to 4 at a thickness of 23 µm on one side. Was formed to produce Cu core balls of Examples 1A to 19A.

  Also, using the Cu balls of Examples 1 to 19 described above, for Examples 1B to 19B, a Ni plating layer was formed as a metal layer with a thickness of 2 μm on one side, and further a composition was formed with a thickness of 23 μm on one side. Examples 1B to 19B were prepared by forming a solder layer by an electroplating method using the solder alloys of Examples 1 to 4.

  Further, using the Cu balls of Comparative Examples 1 to 12 described above, a solder layer of the solder alloy of Composition Examples 1 to 4 was formed at a thickness of 23 μm on one side to produce Cu core balls of Comparative Examples 1A to 12A. . Further, using the Cu balls of Comparative Examples 1 to 12 described above, a Ni plating layer was formed with a thickness of 2 μm on one side as a metal layer, and further, a solder alloy of Composition Examples 1 to 4 was formed with a thickness of 23 μm on one side. The Cu core ball of Comparative Examples 1B-12B was produced by forming a solder layer.

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

-Sphericity The sphericity of Cu balls and Cu core balls was measured by a CNC image measurement system. The device is an Ultra Quick Vision, ULTRA QV350-PRO manufactured by Mitutoyo Corporation.

[Evaluation criteria for sphericity]
In each of the following tables, evaluation criteria for the sphericity of Cu balls and Cu core balls were as follows.
〇: The sphericity was 0.99 or more ○ 〇: The sphericity was 0.98 or more and less than 0.99 〇: The sphericity was 0.95 or more and less than 0.98 ×: sphericity was less than 0.95

-Vickers hardness The Vickers hardness of the Cu ball was measured according to "Vickers hardness test-test method JIS Z2244". As a device, a micro Vickers hardness tester manufactured by Akashi Seisakusho, AKASHI micro hardness tester MVK-F 12001-Q was used.

[Evaluation criteria for Vickers hardness]
In each of the following tables, evaluation criteria for Vickers hardness of Cu balls were as follows.
：: Over 0 HV and 55.5 HV or less ×: Over 55.5 HV

-Α dose The measuring method of the α dose of the Cu ball is as follows. An α-ray measuring device of a gas flow proportional counter was used for measurement of α-dose. The measurement sample is a 300 mm × 300 mm flat shallow container in which Cu balls are laid until the bottom of the container becomes invisible. This measurement sample was placed in an α-ray measuring apparatus, and allowed to stand in a PR-10 gas flow for 24 hours, after which the α dose was measured.

[Evaluation criteria for α dose]
In each of the following tables, the evaluation criteria for the α dose of Cu balls were as follows.
：: α dose was 0.0200 cph / cm ² or less ×: α dose exceeded 0.0200 cph / cm ²

  The PR-10 gas (90% argon to 10% methane) used in the measurement is one that has passed three weeks or more after filling the gas cylinder with the PR-10 gas. The reason for using a cylinder that has passed for three weeks or more is that JEDEC STANDARD-Medical Measurement Medical Equipment Measurement Material specified by the JEDEC (Joint Electron Device Engineering Council) to prevent α-rays from being generated by radon in the atmosphere entering the gas cylinder. This is because JESD221 was followed.

・ Discoloration resistance To measure the discoloration resistance of the Cu ball, the Cu ball is heated for 420 seconds at a setting of 200 ° C. in a constant temperature bath in an air atmosphere, and the change in lightness is measured, and the change over time is sufficiently measured. It was evaluated whether the Cu ball could withstand. The lightness was measured using a Konica Minolta CM-3500d type spectrophotometer with a D65 light source and a 10-degree field of view, and the spectral transmittance was measured according to JIS Z 8722 “Color measurement method-reflection and transmission object color”. From the color values (L ^* , a ^* , b ^* ). Note that (L ^* , a ^* , b ^* ) is defined in JIS Z 8729 "Color Display Method-L ^* a ^* b ^* Color System and L ^* u ^* v ^* Color System". It is. L ^* is lightness, a ^* is redness, and b ^* is yellowness.

[Discoloration resistance evaluation criteria]
In each of the following tables, the evaluation criteria for the discoloration resistance of Cu balls were as follows.
：: Lightness after 420 seconds was 55 or more ×: Lightness after 420 seconds was less than 55

・ Comprehensive evaluation In the sphericity, Vickers hardness, α dose and discoloration resistance in the evaluation method and evaluation criteria described above, the Cu ball which was ○ or ○ or did. On the other hand, any one of the spheres, the Vickers hardness, the α dose and the discoloration resistance, was evaluated as “X” in the overall evaluation.

  Further, a Cu core ball having a sphericity of ○, ○, or ○ in the above-described evaluation method and evaluation criteria was evaluated as ○ in the overall evaluation together with the evaluation of the Cu ball. On the other hand, a Cu core ball having a sphericity of x was evaluated as x in the overall evaluation. Further, even if the sphericity of the Cu core ball was evaluated as Δ, ○, or ○, any one of the sphericity, Vickers hardness, α dose, and discoloration resistance was evaluated in the Cu ball evaluation. Regarding Cu core balls that were at least x, the overall evaluation was x.

  Since 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, the Vickers hardness of the Cu core ball was not evaluated. However, as long as the Vickers hardness of the Cu core ball is within the range specified in the present invention, even if the Cu core ball is a ball, the ball has good drop impact resistance, can suppress cracking, and has a reduced electrode collapse. Can be suppressed, and furthermore, the deterioration of the electric conductivity can be suppressed.

  On the other hand, when the Vickers hardness of the Cu core ball is larger than the range specified in the present invention, the durability against external stress is reduced, the drop impact resistance is deteriorated, and cracks occur. The problem of becoming easy to solve cannot be solved.

  For this reason, Cu core balls using the Cu balls of Comparative Examples 8 to 11 having Vickers hardness exceeding 55.5 HV are not suitable for evaluation of Vickers hardness.

  In addition, since the discoloration resistance of the Cu core ball depends on the Ni plating layer which is an example of the solder layer and the metal layer, the discoloration resistance of the Cu core ball is not evaluated. However, if the lightness of the Cu ball is within the range specified in the present invention, sulfides and sulfur oxides on the Cu ball surface are suppressed, and the coating with a metal layer such as a solder layer or a Ni plating layer can be performed. Are suitable.

  On the other hand, if the lightness of the Cu ball is lower than the range specified in the present invention, the sulfide or sulfur oxide on the Cu ball surface is not suppressed, and the Cu ball is covered with a metal layer such as a solder layer or a Ni plating layer. Not suitable for

  For this reason, Cu core balls using the Cu balls of Comparative Examples 1 to 6 whose lightness after 420 seconds were less than 55 were not suitable for the evaluation of the discoloration resistance.

  The α 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 a Ni plating layer, which is an example of a metal layer covering a Cu ball, is provided, it also depends on a plating solution raw material forming the Ni layer.

  When the Cu ball has a low α dose defined in the present invention, if the plating solution raw material constituting the solder layer and the Ni plating layer is the low α dose defined in the present invention, the Cu core ball is also defined in the present invention. Low alpha dose. On the other hand, if the plating solution raw material constituting the solder layer and the Ni plating layer is a high α dose exceeding the α dose specified in the present invention, even if the Cu ball has the low α dose described above, the Cu core The ball also has a high α dose exceeding the α dose specified in the present invention.

  In addition, when the α dose of the plating solution raw material constituting the solder layer and the Ni plating layer shows a slightly higher α dose than the low α dose specified in the present invention, the impurities are removed in the plating process described above. , Α dose is reduced to the low α dose range defined in the present invention.

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

  The details of the evaluation will be described below. As in Examples 1 to 12, 18, a Cu ball having 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. Showed good results in the comprehensive evaluation of sphericity, Vickers hardness, α dose and discoloration resistance. As shown in Examples 13 to 17, 19, Cu balls having a purity of 4N5 or more and 5N5 or less and containing a total of 5.0 mass ppm or more and 50.0 mass ppm or less of Fe, Ag, and Ni are also sphericity and Vickers hardness. Good results were obtained in the comprehensive evaluation of α-dose and discoloration resistance. In addition, although not shown in the table, from Examples 1, 18, and 19, the Fe content was reduced to 0 mass ppm or more and less than 5.0 mass ppm, and the Ag content was reduced to 0 pp or more and less than 5.0 mass ppm, respectively. , Ni content is changed from 0 mass ppm or more to less than 5.0 mass ppm, and the Cu ball whose total of Fe, Ag and Ni is 5.0 mass ppm or more also has sphericity, Vickers hardness and α dose. Good results were obtained in the overall evaluation of discoloration resistance.

  Further, as shown in Example 18, Fe, Ag, or Ni is contained in an amount of 5.0 mass ppm or more and 50.0 mass ppm or less, and Sb, Bi, Zn, Al, As, Cd, and Pb of other impurity elements are contained. Also, the Cu ball of Example 18 in which each of In, Sn, and Au is 50.0 mass ppm or less also obtained good results in the comprehensive evaluation of sphericity, Vickers hardness, α dose, and discoloration resistance.

  As shown in Tables 3 and 4, the Cu core ball contains 95.0% by mass of Pb and the balance is Sn (Sn content: 5.0% by mass). The Cu core balls of Examples 1A to 19A coated with the Cu balls of Examples 1 to 19 and the Cu balls of Examples 1 to 19 with a solder layer were coated with a Ni plating layer. In the Cu core balls of Examples 1B to 19B coated with a solder layer of a solder alloy, good results were obtained in the comprehensive evaluation of sphericity.

  The Cu balls of Examples 1 to 19 were coated with a solder layer of the solder alloy of Composition Example 2 containing 90.0% by mass of Pb and the balance being Sn (Sn content: 10.0% by mass). The Cu nuclei balls of Examples 1A to 19B in which the Cu core balls of Examples 1A to 19A and the Cu balls of Examples 1 to 19 were covered with a Ni plating layer and further covered with a solder layer of the solder alloy of Composition Example 2. Good results were also obtained with the ball in the overall sphericity evaluation.

  A Cu layer of Examples 1 to 19 was coated with a solder layer containing 37.0% by mass of Pb and the balance being Sn (Sn content: 63.0% by mass) with the solder alloy of Composition Example 3. The Cu core balls of Examples 1A to 19B obtained by coating the Cu core balls of Examples 1A to 19A and the Cu balls of Examples 1 to 19 with a Ni plating layer and further coating with a solder layer of the solder alloy of Composition Example 3. Good results were also obtained with the ball in the overall sphericity evaluation.

  A solder layer made of the solder alloy of Composition Example 4 containing 37.0% by mass of Pb and 3.0% by mass of Ag, and the balance being Sn (Sn content: 60.0% by mass). The Cu core balls of Examples 1A to 19A coated with the Cu ball of Example 19, and the Cu balls of Examples 1 to 19 were coated with a Ni plating layer, and further coated with a solder layer of the solder alloy of Composition Example 4. In the Cu core balls of Examples 1B to 19B, good results were obtained in the comprehensive evaluation of sphericity.

  In addition, although not shown in the table, from Examples 1, 18, and 19, the Fe content was reduced to 0 mass ppm or more and less than 5.0 mass ppm, and the Ag content was reduced to 0 pp or more and less than 5.0 mass ppm, respectively. , Ni content is changed to 0 mass ppm or more and less than 5.0 mass ppm, and a Cu ball having a total of 5.0 mass ppm or more of Fe, Ag, and Ni is prepared according to any one of composition examples 1 to 4. Cu core ball coated with a solder layer of the solder alloy of No. 1, Cu core ball coated with the Ni plating layer, and further coated with a solder layer of any of the solder alloys of Composition Examples 1 to 4, Good results were obtained in the overall evaluation of sphericity.

  On the other hand, in the Cu ball of Comparative Example 7, the total content of Fe, Ag, and Ni was less than 5.0 ppm by mass, U and Th were less than 5 ppm by mass, and the other impurity elements were also 1 ppm by mass. The Cu core ball of Comparative Example 7A, in which the Cu ball of Comparative Example 7 and the Cu ball of Comparative Example 7 were coated with a solder layer of a solder alloy of each composition example, and the Cu ball of Comparative Example 7 was Ni The Cu core ball of Comparative Example 7B coated with a plating layer and further coated with a solder layer of a solder alloy of each composition example had a sphericity of less than 0.95. In addition, even if it contains an impurity element, the Cu ball of Comparative Example 12 and the Cu ball of Comparative Example 12 in which the total content of at least one of Fe, Ag, and Ni is less than 5.0 mass ppm, The Cu core ball of Comparative Example 12A and the Cu ball of Comparative Example 12 covered with a solder layer of the solder alloy of each composition example were covered with a Ni plating layer, and further covered with a solder layer of the solder alloy of each composition example. The Cu core ball of Example 12B also had a sphericity of less than 0.95. From these results, a Cu ball having a total content of at least one of Fe, Ag and Ni of less than 5.0 mass ppm, a Cu ball obtained by coating the Cu ball with a solder layer of a solder alloy of each composition example It can be said that the core ball and the Cu core ball obtained by coating the Cu ball with a Ni plating layer and further coating with a solder layer of a solder alloy of each composition example cannot achieve high sphericity.

  The Cu ball of Comparative Example 10 had a total content of Fe, Ag, and Ni of 153.6 ppm by mass and the content of other impurity elements was 50 ppm by mass or less, respectively, but had a Vickers hardness of 55.5 HV. And good results could not be obtained. Further, in the Cu ball of Comparative Example 8, the total content of Fe, Ag, and Ni was 150.0 mass ppm, and the content of other impurity elements, particularly, Sn was 151.0 mass ppm, The content greatly exceeded 50.0 ppm by mass, the Vickers hardness exceeded 55.5 HV, and good results could not be obtained. Therefore, even in the case of a Cu ball having a purity of 4N5 or more and 5N5 or less, the Vickers hardness of a Cu ball in which the total content of at least one of Fe, Ag, and Ni exceeds 50.0 mass ppm increases. It can be said that low hardness cannot be realized. As described above, when the Vickers hardness of the Cu ball is larger than the range specified in the present invention, the durability against external stress is reduced, the drop impact resistance is deteriorated, and cracks are easily generated. Problem cannot be solved. Furthermore, it can be said that other impurity elements are preferably contained in a range not exceeding 50.0 mass ppm.

  From these results, a Cu ball having a purity of 4N5 or more and 5N5 or less and a total content of at least one of Fe, Ag, and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less is highly spherical. It can be said that a degree and low hardness are realized and discoloration is suppressed. A Cu core ball obtained by coating such a Cu ball with a solder layer of a solder alloy of each composition example, and a Cu core obtained by coating such a Cu ball with a Ni plating layer and further coated with a solder layer of a solder alloy of each composition example The ball realizes a high sphericity, and also realizes a low hardness of the Cu ball, so that the Cu core ball also has a good drop impact resistance, can suppress cracks, can suppress electrode crushing, and the like. Deterioration of electrical conductivity can be suppressed. Further, since discoloration of the Cu ball is suppressed, it is suitable for coating 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 having the same composition as those of the examples and having a sphere diameter of 1 μm or more and 1000 μm or less are all excellent in sphericity, Vickers hardness, α dose, and overall evaluation of discoloration resistance. The result was obtained. From this, it can be said that the 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 had a total content of Fe, Ag and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less, contained 2.9 mass ppm of P, and had sphericity, Good results were obtained in the comprehensive evaluation of Vickers hardness, α dose and discoloration resistance. A Cu core ball in which the Cu ball of Example 19 was coated with a solder layer of the solder alloy of each composition example, the Cu ball of Example 19 was coated with a Ni plating layer, and further coated with a solder layer of the solder alloy of each composition example Good results were also obtained with the Cu core ball in the overall evaluation of sphericity. The Cu ball of Comparative Example 11 had a total content of Fe, Ag, and Ni of 50.0 mass ppm or less similarly to the Cu ball of Example 19, but had a Vickers hardness exceeding 5.5 HV. The result was different from that of the Cu ball of Example 19. Also, in Comparative Example 9, the Vickers hardness exceeded 5.5 HV. This is considered to be because the content of P in Comparative Examples 9 and 11 was remarkably large. From this result, it can be seen that as the P content increases, the Vickers hardness increases. Therefore, the P content is preferably less than 3 ppm by mass, and more preferably less than 1 ppm by mass.

In the Cu balls of the respective examples, the α dose was 0.0200 cph / cm ² or less. Therefore, in each of the solder alloys of Composition Examples 1 and 2 covering the Cu balls of Examples 1 to 19, each element has a low α dose defined in the present invention. The Cu core ball also has a low α dose specified in the present invention. Further, when a Ni plating layer, which is an example of a metal layer that covers the Cu ball, is provided, in addition to the solder alloy, each element constituting the Ni plating layer has a low α dose defined in the present invention. The Cu core balls of Examples 1B to 19B also have the low α dose specified in the present invention.

  Furthermore, in the plating step of forming the solder layer and the Ni plating layer, impurities that emit α-rays contained in the alloy are removed, so that the α-dose of the alloy before plating can be reduced to a low α defined by the present invention. Even when the α dose is slightly higher than the dose, the α dose after plating is reduced to the low α dose range defined in the present invention.

  Thereby, when the Cu core ball of each embodiment is used for high-density mounting of electronic components, since the raw materials constituting the solder layer and the Ni plating layer have the low α dose specified in the present invention, the soft error is reduced. Can be suppressed.

  In the Cu ball of Comparative Example 7, good results were obtained in color fastness, whereas in Comparative Examples 1 to 6, good results were not obtained in color fastness. When the Cu balls of Comparative Examples 1 to 6 and the Cu ball of Comparative Example 7 are compared, the only difference between these compositions is the S content. Therefore, it can be said that the content of S needs to be less than 1 mass ppm in order to obtain a good result in discoloration resistance. Since the Cu content of each example has an S content of less than 1 ppm by mass, it can be said that the S content is preferably less than 1 ppm by mass.

  Subsequently, in order to confirm the relationship between the content of S and the discoloration resistance, the Cu balls of Example 14, Comparative Examples 1 and 5 were heated at 200 ° C. Seconds and 420 seconds later, photographs were taken and the lightness was measured. Table 7 and FIG. 5 are graphs showing the relationship between the heating time of each Cu ball and the brightness.

  From this table, comparing the brightness before heating and the brightness 420 seconds after heating, the brightness of Example 14 and Comparative Examples 1 and 5 was close to 64 or 65 before heating. After 420 seconds from heating, the lightness of Comparative Example 5 containing 30.0 mass ppm of S became the lowest, followed by Comparative Example 1 containing 10.0 mass ppm of S and the content of S was 1 mass ppm. Example 14 was in the order of less than. From this, it can be said that the higher the S content, the lower the brightness after heating. Since the lightness of the Cu balls of Comparative Examples 1 and 5 was lower than 55, it can be said that the Cu balls containing 10.0 mass ppm or more of S easily form sulfides and sulfur oxides during heating and are easily discolored. When the S content is 0 mass ppm or more and 1.0 mass ppm or less, it can be said that the formation of sulfides and sulfur oxides is suppressed and the wettability is good. When the Cu ball of Example 14 was mounted on the electrode, good wettability was exhibited.

  As described above, the purity is 4N5 or more and 5N5 or less, the total content of at least one of Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, and the S content is 0 mass ppm or less. Since the sphericity was 0.95 or more in any of the Cu balls of this example in which the content of P is 0 to less than 3.0 and less than 3.0 ppm by mass. , High sphericity was realized. By realizing a high sphericity, self-alignment when a Cu ball is mounted on an electrode or the like can be ensured, and variations in the height of the Cu ball can be suppressed. The same effect can be obtained with a Cu core ball in which the Cu ball of the present embodiment is covered with a solder layer, and a Cu core ball in which the Cu ball of the present embodiment is covered with a metal layer and the metal layer is further covered with a solder layer.

  In addition, the Vickers hardness of each of the Cu balls of this example was 55 HV or less, so that a low hardness was realized. By realizing low hardness, the drop impact resistance of the Cu ball can be improved. By realizing a low hardness of the Cu ball, a Cu core ball obtained by coating the Cu ball of the present example with a solder layer, a Cu core ball obtained by coating the Cu ball of the present example with a metal layer, and further coating the metal layer with a solder layer The core ball also has good drop impact resistance, can suppress cracking, can suppress electrode crushing, and can also suppress deterioration of electrical conductivity.

  Further, in the Cu balls of the present example, discoloration was suppressed in all cases. By suppressing the discoloration of the Cu ball, the adverse effect of the sulfide or the sulfur oxide on the Cu ball can be suppressed, and the wettability when the Cu ball is mounted on the electrode is 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 a Ni plating layer.

  In addition, a Cu ball having a purity of 4N5 or more and 5N5 or less was manufactured using a Cu nugget material having a purity of more than 4N5 and 6N or less for the Cu material of the present example. , Good results were obtained in the overall evaluation of both the Cu ball and the Cu core ball.

  Next, the distribution of the elements Sn and Pb in the solder layer in a Cu core ball in which the surface of the Cu ball is covered with a solder layer of a Sn-based solder alloy will be described. As a solder layer for covering a Cu ball, as disclosed in Japanese Patent Application Laid-Open No. 2007-44718 (referred to as Patent Document 4) and Japanese Patent No. 5368924 (referred to as Patent Document 5), a solder alloy containing Sn as a main component is used. Is used.

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

  In Patent Document 4, the content of Bi contained in the solder layer is plated with a concentration gradient such that the inside (inner side) is thinner and the outer side (outer side) becomes denser.

  Patent Literature 5 also discloses a solder bump in which a Cu ball is plated with a Sn-based solder alloy composed of Sn and Bi. The Bi content contained in the solder layer in Patent Literature 5 is plated with a concentration gradient such that the inside (inner side) is denser and the outer side (outer side) becomes thinner.

  The technique of Patent Document 5 has a concentration gradient completely opposite to that of Patent Document 4. This is probably because the density control according to Patent Literature 5 is simpler than that according to Patent Literature 4, and is easier to manufacture.

  As described above, when a Cu core ball obtained by plating a surface of a Cu ball with a binary Sn-based solder alloy obtained by adding another element to Sn is mounted on an electrode of a semiconductor chip and reflowed, Patent Literatures 4 and 5 in which the element has a concentration gradient in the solder layer cause the following problems.

  The technique disclosed in Patent Document 4 is a solder layer having a concentration gradient such that the Bi concentration is low on the inner peripheral side and is higher on the outer peripheral side. In the case of (2), the timing of Bi melting may be slightly shifted between the inner peripheral side and the outer peripheral side.

  If the melting timing shifts, even if the outer surface of the Cu core ball has begun to melt, there will be partial melting in which the melting has not yet occurred in the region on the inner peripheral surface side. Slightly displaces the melted side. In high-density mounting at a narrow pitch, soldering due to this positional shift may be a fatal defect.

  In Patent Document 5, Bi concentration gradient is opposite to that in Patent Document 1. Even in this case, heat treatment by reflow is performed to connect the semiconductor package. As in Patent Literature 5, when heating and melting in a state where the Bi concentration in the solder layer is high on the inner circumference side and thin on the outer circumference side, the Bi density on the inner circumference side is high, so the solder starts to melt from the Bi area on the inner circumference side. . Even if the inner peripheral Bi region is melted, the outer peripheral Bi region has not yet begun to melt, and therefore the volume expansion on the inner peripheral Bi region occurs quickly.

  Due to the slowing of the volume expansion on the inner and outer peripheral sides, a pressure difference occurs between the inner peripheral side of Bi and the outer peripheral side (outside air), and when the outer peripheral side of Bi starts to melt, the pressure difference due to the volume expansion on the inner peripheral side causes the core. , A situation occurs in which the Cu ball jumps out. Such a situation must be avoided.

  As described above, the Cu core ball having the solder layer composed of the Sn-based solder alloy composed of Sn and Bi has a defect when Bi has a concentration gradient in the solder layer.

  In recent years, Pb-free solder alloys have been widely used. On the other hand, in specific applications such as electronic devices used in space, a solder alloy containing Pb is used. Thus, even with a core material whose core is coated with a binary or more solder alloy in which Sn is added with Pb, if Pb has a predetermined concentration gradient in the solder layer, it is considered that the same problem as that of Bi described above occurs. Can be

Therefore, the operation and effect of the uniform distribution of Pb in the solder layer 3 will be described. The following experiment was performed to confirm that the Pb concentration distribution in the solder layer 3 was a value corresponding to the target value. In the following examples, the Sn content is 5.0% by mass, whereas the Pb content is 95.0% by mass, which is higher in Pb content than Sn. Since the Sn concentration distribution in the solder layer 3 was a value corresponding to the target value, it was confirmed that the Pb concentration distribution in the solder layer 3 was a value corresponding to the target value.
(1) A Cu core ball 11B in which the composition of the solder layer 3 is 5% by mass of Sn and 95% by mass of Pb (Sn-95Pb) is prepared under the following conditions. In the following examples, Cu balls having the composition of Example 17 shown in Table 1 were used.
・ Cu ball 1 diameter: 250 μm
・ Film thickness of metal layer (Ni plating layer) 2: 2 μm
・ Thickness of solder layer 3: 23 μm
・ Diameter of Cu core ball 11B: 300 μm

  In order to facilitate the measurement of the experimental results, a Cu core ball having a relatively thin solder layer was manufactured as the Cu core ball 11B.

The plating was performed by an electroplating method.
(2) As samples, ten Cu core balls 11B on which a solder layer of a (Sn-95Pb) -based solder alloy having the same composition was formed were prepared. These were used as Sample A.
(3) Ten samples A are sealed with resin.
(4) The sealed sample A is polished together with the resin, and the cross section of each sample A is observed. The observation equipment used was FE-EPMAJXA-8530F manufactured by JEOL.

  FIG. 6 is an explanatory diagram showing an example of a method for measuring the Sn concentration distribution of the Cu core ball. The solder layer 3 is divided into an inner layer 16a, an intermediate layer 16b, and an outer layer 16c from the surface side of the Cu ball 1 for convenience. The inner layer 16a has a thickness of 9 μm from the surface of the Cu ball 1, the intermediate layer 16b has a thickness of 9 to 17 μm, and the outer layer 16c has a thickness of 17 to 23 μm. The inner layer 16a, the intermediate layer 16b and the outer layer 16c have a thickness as shown in FIG. An inner layer region 17a, an intermediate layer region 17b, and an outer layer region 17c each having a width of 5 μm and a width of 40 μm were cut out, and the Sn concentration was measured by qualitative analysis using each region as a measurement region. This operation was performed for each of the inner layer 16a, the intermediate layer 16b, and the outer layer 16c for a total of 10 visual fields.

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

  Table 8 shows that, in Sample A, the average value of the Sn concentration of each layer of the solder layer measured with ten Cu core balls and the Sn content when the target Sn content (target value) is 5% by mass. Are shown.

  As described above, in Sample A, the Sn concentration of the inner layer, the intermediate layer, and the outer layer was measured for ten Cu core balls. Table 8 does not show the measured values of the concentrations of Sn in the inner layer, intermediate layer, and outer layer of each of the ten Cu core balls for sample A.

Sample A has a target Sn content (target value) of 5% by mass. In this case, the Sn concentration ratio (%) of each of the ten Cu core balls in the sample A is obtained from the measured value of the Sn concentration by the following equation (1).
Concentration ratio (%) = (measured value / 5) × 100 (1)

The average value of the Sn concentration is obtained by the following equation (2) when the number of Cu core balls used as the sample is 10.
Average value of Sn concentration = total value of 10 measured values / 10 (2)

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

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

  As described above, in each of the inner layer region 17a, the intermediate layer region 17b, and the outer layer region 17c, the concentration of Sn in the solder layer is within the allowable range of 3.61% by mass to 6.88% by mass. Is 72.2% to 137.6%, so that it is almost within the target value of the Sn concentration ratio of 70% to 140%.

  Then, for example, ten Cu core balls manufactured in the same lot as the sample A were extracted, and each was bonded to a substrate by a normal reflow process. Table 8 also shows the joining results.

  Regarding the joining results, samples in which no joining failure was measured in all samples were judged as “good”.

  In any case, the situation in which the inner peripheral side is melted earlier than the outer peripheral side, a volume expansion difference occurs between the inner peripheral side and the outer peripheral side, and the Cu core ball 11B is repelled, does not occur, or the entire solder layer 3 does not occur. Since the melting is performed almost uniformly, there is no positional shift of the nuclear material, which is considered to be caused by a shift in the melting timing. Therefore, there is no danger of a short circuit between the electrodes due to the positional shift or the like. Therefore, a good result was obtained in which no bonding failure occurred at all.

  As described above, in the case of the (Sn-95Pb) -based solder alloy, from the results in Table 8, 3.61% by mass (concentration ratio: 72.2%) to 6.88% by mass (concentration ratio: 137.6%) Was found to be acceptable.

  Next, the same measurement was performed for the case where the solder layer 3 of the Sn-based solder alloy composed of (Sn-90Pb), which is Sn 10% by mass and Pb 90% by mass, was formed. The Sn distribution at this time is 10% by mass as a target value, but the allowable range is 9.74% by mass (concentration ratio: 97.4%) to 11.20% by mass (concentration ratio: 112.0%). is there. The method of manufacturing the Cu core ball is the same as that of the embodiment of the sample A using the Cu core ball using the (Sn-95Pb) solder alloy described above.

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

  The results are shown as Sample B in Table 8. In this case, the target value of Sn is 10% by mass. Therefore, as shown in Sample B, 9.74 to 11.20% by mass (in all cases, an average value measured 10 times for the same sample) is slightly increased. (A minimum of 9.74% by mass (concentration ratio 97.4%) to a maximum of 11.20% by mass (concentration ratio 112.0%) of the average value) is within an allowable range. Therefore, it can be seen that it is within the range of 9.74% by mass (concentration ratio: 97.4%) to 11.20% by mass (concentration ratio: 112.0%). The bonding was determined to be “good” because good results were obtained in which no poor bonding occurred, as in the example of sample A.

Sample B has a target Sn content (target value) of 10 (% by mass). Therefore, the concentration ratio (%) of the sample B in Table 8 is obtained by the following equation (4).
Concentration ratio (%) = (average of measured values / 10) × 100 (4)

  Next, the same measurement was performed for the case where the solder layer 3 of the Sn-based solder alloy composed of (Sn-37Pb) having 63% by mass of Sn and 37% by mass of Pb was formed. The Sn distribution at this time is 63% by mass as a target value, but the allowable range is 61.30% by mass (concentration ratio 97.3%) to 70.02% by mass (concentration ratio 111.1%). is there. The method of manufacturing the Cu core ball is the same as that of the embodiment of the sample A using the Cu core ball using the (Sn-95Pb) solder alloy described above.

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

  The results are shown as Sample C in Table 8. In this case, the target value of Sn is 63% by mass, and therefore, as shown in Sample C, it is slightly from 61.30 to 70.02% by mass (in all cases, an average value measured ten times for the same sample). (A minimum of 61.30% by mass (concentration ratio 97.3%) to a maximum of 70.02% by mass (concentration ratio 111.1%) of the average value) is within an allowable range. Therefore, it can be seen that it is within 61.30% by mass (concentration ratio 97.3%) to 70.02% by mass (concentration ratio 111.1%). The bonding was determined to be “good” because good results were obtained in which no poor bonding occurred, as in the example of sample A.

Sample C has a target Sn content (target value) of 63 (% by mass). Therefore, the concentration ratio (%) of the sample C in Table 8 is obtained by the following equation (5).
Concentration ratio (%) = (mean value of measured value / 63) × 100 (5)

  Next, the same measurement was performed for the case where the Sn-based solder alloy solder layer 3 composed of (Sn-37Pb-3Ag), which was Sn 60% by mass, Pb 37% by mass, and Ag 3% by mass, was formed. The Sn distribution at this time is 60% by mass as a target value, but the allowable range is 55.83% by mass (concentration ratio 93.1%) to 63.10% by mass (concentration ratio 105.2%). is there. The method of manufacturing the Cu core ball is the same as that of the embodiment of the sample A using the Cu core ball using the (Sn-95Pb) solder alloy described above.

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

  The results are shown as Sample D in Table 8. In this case, the target value of Sn is 60% by mass, and therefore, as shown in Sample D, 55.83 to 63.10% by mass (in all cases, an average value measured 10 times for the same sample). (A minimum of 55.83% by mass (concentration ratio 93.1%) to a maximum of 63.10% by mass (concentration ratio 105.2%) of the average value) is within an allowable range. Therefore, it can be seen that it is within the range of 55.83% by mass (concentration ratio 93.1%) to 63.10% by mass (concentration ratio 105.2%). The bonding was determined to be “good” because good results were obtained in which no poor bonding occurred, as in the example of sample A.

Sample D has a target Sn content (target value) of 66 (% by mass). Therefore, the concentration ratio (%) of the sample D in Table 8 is obtained by the following equation (6).
Concentration ratio (%) = (average of measured values / 60) × 100 (6)

  Table 9 summarizes the results of the above-described Examples of Sample A, Examples of Sample B, Examples of Sample C, and Examples of Sample D. The concentration ratio of Sn is 72.2 to 137.6% by mass. Here, when the sphericity was measured for the Cu core balls prepared in the example of sample A, the example of sample B, the example of sample C, and the example of sample D, all were 0.99 or more, 0.95 or more was satisfied.

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

  In addition, when the Sn concentration in the solder layer 3 was changed, phenomena such as displacement and blow-off of the Cu core ball 11B occurred.

  As described above, in each of Examples A to D, Sn in the solder layer is homogeneous, so Pb in the solder layer is uniform, and the inner peripheral side of Sn and Pb with respect to the film thickness of the solder layer. The Sn, Pb concentration ratio is within a predetermined range over the entire area including the outer peripheral side. For this reason, in the Cu core ball of the present invention in which Sn and Pb in the solder layer are homogeneous, the inner peripheral side is melted earlier than the outer peripheral side, and a volume expansion difference occurs between the inner peripheral side and the outer peripheral side, so that the Cu nucleus is increased. A situation where the ball is repelled does not occur.

  In addition, since Sn and Pb in the solder layer are homogeneous, they are almost uniformly melted over the entire surface of the Cu core ball, so that there is almost no time difference in the melting timing in the solder layer. As a result, the displacement of the Cu core ball caused by the displacement of the melting timing does not occur, so that there is no danger of short-circuiting between the electrodes due to the displacement. Therefore, a high quality solder joint can be provided by using the Cu core ball.

DESCRIPTION OF SYMBOLS 1 ... Cu ball, 11A, 11B ... Cu core ball, 2 ... metal layer, 3 ... solder layer, 10 ... semiconductor chip, 100, 41 ... electrode, 30 ... Solder bump, 40: Printed circuit board, 50: Solder joint, 60: Electronic component

ADVANTAGE OF THE INVENTION According to this invention, the high sphericity and low hardness of a Cu ball are implement | achieved, and the discoloration of a Cu ball is suppressed. By realizing the high sphericity of Cu balls, the Cu balls can achieve high sphericity of Cu nuclei balls coated with metal layers, ensuring self-alignment property when mounting the Cu nuclei ball on an electrode In addition, the variation in the height of the Cu core ball can be suppressed. Also, by realizing the low hardness of the Cu ball, even a Cu core ball in which the Cu ball is covered with a metal layer can improve the drop impact resistance. Further, since discoloration of the Cu ball is suppressed, adverse effects on the Cu ball due to sulfides and sulfur oxides can be suppressed, which is suitable for coating with a metal layer and has good wettability.

The sphericity of the Cu core ball: 0.95 or more The Cu core ball 11A of the first embodiment according to the present invention in which the Cu ball 1 is covered with the solder layer 3, and the Cu ball 1 is the metal layer 2 and the solder The sphericity of the Cu core ball 11B according to the second embodiment of the present invention covered with the layer 3 is preferably 0.95 or more, and more preferably 0.98 or more. , 0.99 or more. If the sphericity of the Cu core balls 11A and 11B is less than 0.95, the Cu core balls 11A and 11B have an irregular shape. Therefore, when the Cu core balls 11A and 11B are mounted on the electrodes and reflow is performed, Cu The core balls 11A and 11B are displaced, and the self-alignment is deteriorated. When the sphericity of the Cu core balls 11A and 11B is 0.95 or more, self-alignment when the Cu core balls 11A and 11B are mounted on the electrode 100 of the semiconductor chip 10 or the like can be ensured. Since the sphericity of the Cu ball 1 is also 0.95 or more, the Cu core balls 11A and 11B have a height in the solder joint 50 because the Cu ball 1 and the metal layer 2 do not melt at the soldering temperature. Can be suppressed. Thereby, the bonding failure between the semiconductor chip 10 and the printed board 40 can be reliably prevented.

Claims (17)

Cu balls,
A solder layer covering the surface of the Cu ball,
The Cu ball,
The sum of the contents of at least one of Fe, Ag and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less;
S content is 0 mass ppm or more and 1.0 mass ppm or less,
P content is 0 mass ppm or more and less than 3.0 mass ppm,
The balance is Cu and other impurity elements, and the purity of the Cu ball is not less than 99.995% by mass and not more than 99.9995% by mass;
The sphericity is 0.95 or more,
The Cu core ball is a (Sn-Pb) solder alloy containing Sn and Pb. 2. The Cu core ball according to claim 1, wherein the solder layer has a Pb content of more than 0% by mass and 95.0% by mass or less and Sn being the balance. 3. The solder layer is made of a (Sn-Pb) -based solder alloy containing Sn and Pb of 37.0 mass% or more and 95.0 mass% or less,
The concentration ratio (%) of Sn contained in the solder layer is
Concentration ratio (%) = (measured value (% by mass) / target content (% by mass)) × 100,
Or
When expressed as concentration ratio (%) = (average value of measurement values (% by mass) / target content (% by mass)) × 100,
The Cu core ball according to claim 1, wherein the concentration ratio is in a range of 70.0 to 140.0%. The solder layer is made of a (Sn-Pb) -based solder alloy containing Sn and Pb of 37.0 mass% or more and 95.0 mass% or less,
The concentration ratio (%) of Sn contained in the solder layer is
Concentration ratio (%) = (measured value (% by mass) / target content (% by mass)) × 100,
Or
When expressed as concentration ratio (%) = (average value of measurement values (% by mass) / target content (% by mass)) × 100,
The Cu core ball according to claim 1 or 2, wherein the concentration ratio is in a range of 90.0 to 110.0%.   The Cu core ball according to any one of claims 1 to 4, wherein the sphericity is 0.98 or more.   The Cu core ball according to any one of claims 1 to 4, having a sphericity of 0.99 or more. The Cu core ball according to any one of claims 1 to 6, wherein the α dose is 0.0200 cph / cm ² or less. The Cu core ball according to any one of claims 1 to 6, wherein the α dose is 0.0010 cph / cm ² or less.   The metal layer which covers the surface of the said Cu ball is provided, The surface of the said metal layer is covered with the said solder layer, The sphericity is 0.95 or more, The statement in any one of Claims 1-8. Cu core ball.   The Cu core ball according to claim 9, having a sphericity of 0.98 or more.   The Cu core ball according to claim 9, having a sphericity of 0.99 or more. The Cu core ball according to any one of claims 9 to 11, wherein the α dose is 0.0200 cph / cm ² or less. The Cu core ball according to any one of claims 9 to 11, wherein the α dose is 0.0010 cph / cm ² or less. The Cu core ball according to any one of claims 1 to 13, wherein a diameter of the Cu ball is 1 µm or more and 1000 µm or less.   A solder joint using the Cu core ball according to claim 1.   A solder paste using the Cu core ball according to any one of claims 1 to 14.   A foam solder using the Cu core ball according to any one of claims 1 to 14.

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