TWI589712B - Copper ball, welding head, foam solder and solder paste - Google Patents

Description

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

The present invention relates to a copper core ball, a solder joint, a foam solder, and a solder paste having a small amount of α lines and having magnetic properties.

In recent years, with the development of small information machines, electronic components are being rapidly developed and miniaturized. In order to reduce the size of the connection terminal and reduce the mounting area, the electronic component is a ball grid array package (hereinafter referred to as "BGA") in which an electrode is provided on the back surface.

Electronic parts suitable for BGA are, for example, semiconductor packages. The semiconductor package seals a semiconductor wafer provided with electrodes with a resin. Solder bumps are formed on the electrodes of the semiconductor wafer. The solder bumps are formed by bonding solder balls to the electrodes of the semiconductor wafer. The semiconductor package to which the BGA is applied is mounted on a printed circuit board by bonding the heated solder bumps to the conductive islands of the printed circuit board. In addition, in order to meet further high-density mounting requirements, the semiconductor package has been reviewed for high-density three-dimensional installations that overlap in the height direction.

However, if a BGA is applied to a semiconductor package mounted in a high-density three-dimensional manner, the solder ball may collapse due to the self-weight of the semiconductor package. If this happens, the solder will seep out from the electrode, causing the electrodes to be connected, and it is judged that a short circuit will occur.

Here, a review is made of solder bumps that electrically couple Cu balls on the electrodes of the electronic components using solder paste. Solder bumps formed using Cu balls When the electronic components are mounted on a printed circuit board, even if the weight of the semiconductor package is applied to the solder bumps, the semiconductor package can be supported by Cu balls that do not melt at the melting point of the solder. Therefore, the solder bumps do not collapse due to the self-weight of the semiconductor package.

The method of disposing the Cu balls on the electrodes is a method of feeding Cu balls to the opening of the mask member disposed on the printed circuit board. In the feeding method, the Cu ball is dropped toward the electrode by the feeding means, the Cu ball is mechanically moved on the mask, and the Cu ball is fed into the opening of the mask. The feeding method is effective for a method in which the Cu ball is miniaturized and the Cu ball is placed on the electrode with high precision.

However, it is conventionally known that when the Cu ball is moved toward the opening portion, the movement of the Cu ball is accompanied by the use of a doctor blade or a bristles, so that the welding ball may be damaged or deformed due to the blade, or the foreign matter may be mixed from the bristles. .

Here, there is a proposal for a feeding method in which the ball is made magnetic, and the ball is damaged during installation. For example, in the welding ball arrangement device described in Patent Document 1, the surface of the solder ball is coated with a ferromagnetic material such as Ni to bond the magnetic solder ball to the substrate, and then the magnet is placed in the stage. Moving, the solder nuclear ball is fed into the opening of the mask by magnetic force.

Further, the copper nucleus ball described in Patent Document 2 is coated with Ni on the surface of the Cu ball for the purpose of preventing Cu of the Cu ball from diffusing into the solder. The metal ball described in Patent Document 3 is provided with Ni, a NiP alloy, a NiB alloy, and between a nuclear ball and a plating layer for the purpose of suppressing the reaction between Cu and the solder. A reaction suppression layer composed of any of Co and Pt.

However, in recent years, although high-density mounting has been achieved with the miniaturization of electronic components, the evolution of high-density mounting has caused soft errors. The soft error is caused by the alpha line entering the memory unit of the semiconductor integrated circuit (hereinafter referred to as "IC"), and the memory content may be overwritten. The α line can be considered to be emitted due to the occurrence of α collapse of radioactive elements such as U, Th, and Po in the solder alloy. Here, in recent years, development of low alpha wire solder materials for reducing the content of radioactive elements has been carried out.

In order to reduce the amount of alpha line, the content of U, Th, Pb, Bi containing radioisotope is generally reduced. For example, Patent Document 4 of the related literature. Patent Document 4 discloses an Sn ingot invention having a low α-line amount. In order to reduce the amount of α-line, not only electrolytic refining but also adsorption of Pb and Bi俾 to reduce the amount of α-line by suspending the adsorbent in the electrolytic solution. Patent Document 5 describes Ag and an Ag alloy having a low α-line amount. Patent Document 6 describes Cu and a Cu alloy having a low α-line amount.

Prior technical literature

Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2009-32813

Patent Document 2: Japanese Patent Laid-Open Publication No. 2010-99736

Patent Document 3: Japanese Patent Laid-Open Publication No. 2007-46087

Patent Document 4: Japanese Patent No. 4472752

Patent Document 5: Japanese Patent Laid-Open Publication No. 2011-214040

Patent Document 6: International Publication No. 2012/120982

However, in the above-mentioned Patent Documents 4 to 6, although a copper nucleus having a low α amount is manufactured, a low α amount of a copper nucleus can be realized by using high-purity Cu, but on the other hand, a true sphericity of the copper nucleus is caused. Reduce the problem. Moreover, there is no consideration in the damage of the copper core ball at the time of installation.

Further, in the above Patent Documents 1 to 3, the problem of reducing the α-line amount of the solder nucleus and the copper nucleus is not considered at all, and there is a problem that the occurrence of soft errors cannot be suppressed at the time of high-density mounting.

Accordingly, the present invention has been made to solve the above problems, and an object of the invention is to provide a copper core ball, a solder joint, a solder paste, and a solder paste which can prevent ball breakage when a copper core ball is attached to an electrode.

The inventors first screened the Cu balls used for the copper nucleus balls. As a result, it was found that if a certain amount of Cu ball contains at least one of Pb and Bi, the true sphericity of the Cu ball is lowered, and even if Ni plating is applied, plating is performed in a low true sphericity state, resulting in The true sphericity of the obtained copper nucleus is reduced.

Next, in order to reduce the amount of α-line of the metal layer containing Ni, Co, and Fe constituting the copper nucleus, attention has been paid to the formation of the metal layer by electroplating. As a result, the inventors of the present invention unexpectedly formed a plating film on the Cu ball while flowing the Cu ball or the plating solution while reducing the Pb and Bi in the plating solution and reducing the Po generated by the collapse of the elements. It was found that even if the adsorbent was not suspended, the Pb, Bi, and Po elements formed a salt. As a result, the elements are not taken in a metal layer such as Ni, and it is found that the amount of the α line is lowered. Further, it has been found that high-purity Ni, Co, and Fe are used for the metal constituting the metal layer, and ion-exchanged water or the like is used. The amount of α-line of the obtained metal layer can be reduced by forming a plating solution with water having less impurities.

Here, the present invention is as follows.

(1) A copper nucleus ball comprising: a Cu ball; and a metal layer which is coated on the surface of the Cu ball and which is composed of one or more elements selected from the group consisting of Ni, Co, and Fe; and characterized in that: the Cu ball The purity is 99.9% or more and 99.995% or less, the U content is 5 ppb or less, the Th content is 5 ppb or less, and the total content of at least one of Pb and Bi is 1 ppm or more, the true sphericity is 0.95 or more, and the α linear amount is 0.0200. Below cph/cm ² .

(2) A copper nucleus ball comprising: a Cu ball; and a metal layer which is coated on the surface of the Cu ball and which is composed of one or more elements selected from the group consisting of Ni, Co, and Fe; and characterized in that: the Cu ball The purity is 99.9% or more and 99.995% or less, and the content of at least one of Pb and Bi is 1 ppm or more, and the true sphericity is 0.95 or more; the metal layer U content is 5 ppb or less, and the Th content is 5 ppb or less. The amount of α line is 0.0200 cph/cm ² or less.

(3) A copper nucleus ball comprising: a Cu ball; a metal layer covered with an element of one or more selected from the group consisting of Ni, Co, and Fe; and a second metal layer; The surface of the metal layer is coated with an element selected from one or more of Ni, Co, and Fe which are not contained in the metal layer, and the Cu ball system has a purity of 99.9% or more and 99.995% or less, Pb. The content of at least one of Bi and Bi is 1 ppm or more, and the true sphericity is 0.95 or more; the second metal layer has a U content of 5 ppb or less, a Th content of 5 ppb or less, and an α line amount of 0.0200 cph/cm ² or less. .

(4) A copper nucleus ball comprising: a Cu ball; a metal layer covered with an element of the surface of the Cu ball and selected from one or more of Ni, Co, and Fe; and a solder layer covered with a solder layer The surface of the metal layer is characterized in that the Cu ball system has a purity of 99.9% or more and 99.995% or less, and at least one of Pb and Bi has a total content of 1 ppm or more and a true sphericity of 0.95 or more; The U content is 5 ppb or less, the Th content is 5 ppb or less, and the α line amount is 0.0200 cph/cm ² or less.

(5) A copper nucleus ball comprising: a Cu ball; a metal layer covered with an element of one or more selected from the group consisting of Ni, Co, and Fe; and a second metal layer; Covering the surface of the metal layer, and comprising one or more elements selected from Ni, Co, and Fe which are not contained in the metal layer; and a solder layer covering the surface of the second metal layer; The Cu ball system has a purity of 99.9% or more and 99.995% or less, and a content of at least one of Pb and Bi is 1 ppm or more, and a true sphericity is 0.95 or more; and the solder layer U content is 5 ppb or less, and Th The content is 5 ppb or less, and the amount of α line is 0.0200 cph/cm ² or less.

(6) The copper nucleus ball according to the above (1) to (5), wherein the α line amount is 0.0200 cph/cm ² or less.

(7) The copper nucleus ball according to the above (1) to (5), wherein the α line amount is 0.0010 cph/cm ² or less.

The copper nucleus ball according to any one of the above aspects, further comprising a flux layer covering the metal layer, the second metal layer or the surface of the solder layer .

(9) A welding head according to any one of the above (1) to (8), wherein the copper core ball is used.

(10) A foamed solder using the copper nucleus ball according to any one of the above (1) to (8).

(11) A solder paste characterized by using the copper nucleus ball according to any one of the above (1) to (8).

According to the present invention, since the α line amount of the Cu ball is set to 0.0200 cph/cm ² or less, when the bonding head is formed using the copper core ball of the present invention, occurrence of soft errors can be suppressed. Further, since the surface of the Cu ball is covered with a metal layer such as Ni, the copper nucleus can be made magnetic. Thereby, it is possible to prevent damage or the like when the copper core ball is attached to the electrode, and it is possible to ensure alignment.

1‧‧‧Cu Ball

2‧‧‧metal layer

11‧‧‧copper ball

Fig. 1 is a view showing an example of the structure of a copper core ball of the present invention.

The invention is described in more detail below. In this specification, the metal layer constituent units (ppm, ppb, and %) of the relevant copper nucleus balls are referred to before the special statement, and the ratio is relative to the mass of the metal layer (mass ppm, mass ppb, and mass%). . Further, the unit (ppm, ppb, and %) of the composition of the relevant Cu spheres is expressed beforehand unless otherwise stated, and indicates the ratio (mass ppm, mass ppb, and mass%) to the mass of the Cu sphere.

Fig. 1 shows an example of the configuration of the copper core ball 11 of the present invention. As shown in FIG. 1, the copper core ball 11 of the present invention includes a Cu ball 1 and a metal layer which is coated with a surface of the Cu ball 1 and which is composed of one or more elements selected from Ni, Co, and Fe. Cu ball 1 has a purity of 99.9% or more and 99.995% or less, a U content of 5 ppb or less, a Th content of 5 ppb or less, a total content of Pb and/or Bi of 1 ppm or more, a true sphericity of 0.95 or more, and an α line amount of 0.0200 cph. /cm ² or less. According to the copper core ball 11 of the present invention, the amount of α line of the bonding head can be reduced, and the entire copper core ball 11 can be made magnetic.

Metal layer

First, the metal layer 2 of the present invention will be described in detail. The metal layer 2 is made of, for example, a Ni plating layer, a Co plating layer, an Fe plating layer, or a plating layer containing at least two of Ni, Co, and Fe elements. When the copper core ball 11 is used as a solder bump, the metal layer 2 does not melt and remain at the soldering temperature, and contributes to the height of the solder joint. Therefore, the metal layer 2 has a high true sphericity, a small diameter variation, and a low α line amount.

. The amount of α-line of the copper nucleus ball: 0.0200 cph/cm ² or less

The α-line amount of the copper core ball 11 of the present invention is 0.0200 cph/cm ² or less. When this type of electronic component is mounted at a high density, the soft error does not constitute the amount of alpha line to the extent of the problem. The α-line amount of the copper core ball 11 of the present invention can be achieved by the amount of the α line of the metal layer 2 constituting the copper core ball 11 being 0.0200 cph/cm ² or less. Therefore, the copper core ball 11 of the present invention has a low alpha line amount because it is covered by the metal layer 2. α dose inhibiting the soft error from the viewpoint of further high-density mounting, preferably based 0.0020cph / cm ² or less, more preferably ² or less based 0.0010cph / cm. The U and Th contents of the metal layer 2 are set to be 5 ppb or less by setting the α line amount of the Cu balls 1 to 0.0200 cph/cm ² or less. Moreover, from the viewpoint of suppressing soft errors of current or future high-density mounting, the U and Th contents are preferably below 2 ppb.

. Magnetic function of the metal layer

Since the surface of the Cu-core ball 11-based Cu ball 1 is covered with the metal layer 2 made of a ferromagnetic material, the entire ball has magnetic properties. Accordingly, by imparting magnetism to the copper core ball 11, the following effects can be obtained. That is, when the copper core ball 11 is mounted on the electrode by the feeding method, the copper core ball 11 scattered on the mask placed on the substrate can be explicitly fed by the magnetic force of the magnet provided in the platform. Mask The opening. Therefore, since the blade and the bristles are directly brought into contact with the copper core ball 11 as in the conventional feeding means, the copper core ball 11 can be prevented from being damaged and deformed by the feeding means, and foreign matter can be prevented from entering. Moreover, since the position of the copper core ball 11 can be adjusted by the action of the magnet, the alignment property when the copper core ball 11 is attached to the electrode can be ensured.

. Barrier function of metal layer

At the time of reflow soldering, in the solder (paste) used to bond the copper core ball 11 and the electrode, there is Cu which diffuses the Cu ball 1, and a large amount of hard and brittle Cu ₆ Sn is formed in the solder and the joint interface. ₅ , Cu ₃ Sn intermetallic compound, when the impact is cracked will progress, resulting in damage to the joint. Therefore, in order to obtain sufficient joint strength, it is necessary to suppress (blocking) the diffusion of Cu from the Cu balls 1 toward the solder. In the present embodiment, since the metal layer 2 functioning as a barrier layer is formed on the surface of the Cu ball 1, it is possible to suppress diffusion of Cu of the Cu ball 1 into the paste solder.

. Metal layer composition and film thickness

The composition of the metal layer 2 is such that when the metal layer 2 is composed of a single Ni, Co or Fe, Ni, Co, and Fe are 100% excluding unavoidable impurities. Further, the metal used in the metal layer 2 is not limited to a single metal, and an alloy of two or more elements selected from Ni, Co or Fe may be used. Further, a second metal layer made of a single metal or alloy of Ni, Co, or Fe other than the element selected from the metal layer 2 may be coated on the surface of the metal layer 2. In the metal layer 2 or the second metal layer, it is also possible to quantitatively add other elements to the extent that the barrier function and the magnetic function of Ni, Co, and Fe are not affected. The added elements may be, for example, Sn, Ag, Cu, In, Sb, Ge, P, or the like. The film thickness T of the metal layer 2 or the second metal layer is, for example, 1 μm to 20 μm.

2. Cu ball

Next, the Cu ball 1 constituting the present invention will be described in detail. When the copper ball 11 is used as a solder bump, the Cu ball 1 is not melted and remains at the soldering temperature, and contributes to the height of the bonding head. Therefore, the true sphericity is high, the diameter variation is small, and the α line amount is low. .

. U: 5 ppb or less, Th: 5 ppb or less

U and Th are radioactive isotopes, and it is necessary to suppress such content in order to suppress soft errors. The U and Th contents are such that the α line amount of the Cu balls 1 can be set to 0.0200 cph/cm ² or less, and it is necessary to set them to 5 ppb or less. Further, from the viewpoint of suppressing soft errors of current or future high-density mounting, the U and Th contents are preferably 2 ppb or less, respectively.

. Cu ball purity: 99.9% or more and 99.995% or less

The Cu sphere 1 constituting the present invention preferably has a purity of 99.9% or more and 99.995% or less. When the purity of the Cu ball 1 is within this range, a sufficient amount of crystal nucleus for increasing the true sphericity of the Cu ball 1 can be secured in the molten Cu. The reason for the improvement in true sphericity is detailed below.

When the Cu ball 1 is produced, the Cu material forming the predetermined shape piece is melted by heating, and the molten Cu becomes spherical by the surface tension, and it solidifies into the Cu ball 1. During the solidification of molten Cu from a liquid state, the crystal grains grow in spherical molten Cu. At this time, if the amount of the impurity element is excessive, the impurity element becomes a crystal nucleus and suppresses the growth of the crystal grain. Therefore, the spherical molten Cu is a Cu ball 1 having a high true sphericity due to the fine crystal grains whose growth is suppressed. On the other hand, when the amount of the impurity element is small, the relative crystallinity of the crystal nucleus is also reduced, and the directional growth is not inhibited by the grain growth. As a result, spherical molten Cu Some of the surface will protrude and solidify. Such a Cu ball 1 has a low true sphericity. As the impurity element, for example, Sn, Sb, Bi, Zn, As, Ag, Cd, Ni, Pb, Au, P, S, U, Th, or the like can be considered.

The lower limit of the purity is not particularly limited, and is preferably 99.9% or more from the viewpoint of suppressing the amount of α-line and suppressing the deterioration of the conductivity and thermal conductivity of the Cu ball 1 due to the low purity.

Here, the higher the purity of the metal layer 2 such as the Ni plating layer, the lower the α line amount, and the relative Cu ball 1 can reduce the α line amount even if the purity is not increased more than necessary. The melting point of Cu is higher than that of Sn, and the heating temperature at the time of production is higher. In the present invention, when the Cu ball 1 is produced, as will be described later, the radioactive element represented by ²¹⁰ Po, ²¹⁰ Pb, and ²¹⁰ Bi is volatilized by performing a conventional heat treatment on the Cu material. Among these radioactive elements, ²¹⁰ Po is particularly volatile.

. α line amount: 0.0200 cph/cm ² or less

The α-line amount of the Cu balls 1 constituting the present invention is preferably 0.0200 cph/cm ² or less. When this type of electronic component is mounted at a high density, the soft error does not constitute the amount of alpha line to the extent of the problem. In the present invention, a step which is usually adopted for producing the Cu ball 1 is added, and heat treatment is again performed. Therefore, the extremely small ²¹⁰ Po in the raw material of Cu volatilizes, and the Cu ball 1 exhibits a lower α line amount than the raw material of Cu. α dose can be further suppressed from the viewpoint of a soft error in the high-density mounting, preferably based 0.0020cph / cm ² or less, more preferably ² or less based 0.0010cph / cm.

. The content of at least one of Pb and Bi is more than 1 ppm

The Cu sphere 1 constituting the present invention contains Sn, Sb, Bi, and Zn of an impurity element. As a content of at least one of As, Ag, Cd, Ni, Pb, Au, P, S, U, Th, and the like, in particular, at least one of Pb and Bi is contained in an amount of 1 ppm or more. In the present invention, even when the Cu balls 1 are exposed during the formation of the solder joint, it is not necessary to reduce the content of at least one of Pb and Bi of the Cu balls 1 to the limit without lowering the α line amount. The reasons are as follows.

²¹⁰ Pb and ²¹⁰ Bi will be converted to ²¹⁰ Po due to β collapse. In order to reduce the amount of alpha rays, it is preferable to also reduce the Pb and Bi contents belonging to the impurity elements.

However, the content of ²¹⁰ Pb and ²¹⁰ Bi contained in Pb and Bi is relatively low. When the content of Pb and Bi is lowered to some extent, it is considered that ²¹⁰ Pb and ²¹⁰ Bi are almost removed. The Cu ball 1 of the present invention is produced by setting the melting temperature of Cu to be slightly higher than conventionally, or by subjecting the Cu material and/or the pelletized Cu ball 1 to heat treatment. This temperature is vaporized even when it is lower than the boiling points of Pb and Bi, so that the amount of impurity elements can be reduced. Further, in order to increase the true sphericity of the Cu ball 1, the higher the impurity element content, the better. Therefore, the Cu ball 1 of the present invention has a total content of at least one of Pb and Bi of 1 ppm or more. When both Pb and Bi are contained, the total content of Pb and Bi is 1 ppm or more.

Accordingly, at least one of Pb and Bi remains in a certain amount even after the Cu ball 1 is produced, and thus the measurement error of the content is small. Further, as described above, since Bi and Pb become crystal nucleus when the Cu ball 1 is melted in the production step, Cu balls 1 having high true sphericity can be produced by containing a certain amount of Bi and Pb in Cu. Therefore, Pb and Bi are important elements for estimating the content of impurity elements. From this viewpoint, the total content of at least one of Pb and Bi is preferably 1 ppm or more in total. The content of at least one of Pb and Bi is more preferably 10 ppm or more in total. The upper limit value is not particularly limited, and the guidance of the Cu ball 1 is suppressed. In view of electric conductivity deterioration, it is preferable that the content of at least one of Pb and Bi is less than 1000 ppm in total, and particularly preferably 100 ppm or less. The Pb content is preferably 10 ppm to 50 ppm, and the Bi content is preferably 10 ppm to 50 ppm.

. Cu ball true sphericity: 0.95 or more

The Cu balls 1 constituting the present invention have a true sphericity of 0.95 or more from the viewpoint of an appropriate space (gap height) between the control substrates. When the true sphericity of the Cu ball 1 is less than 0.95, since the Cu ball 1 has an indefinite shape, a bump having a height unevenness is formed at the time of forming the bump, and the possibility of occurrence of joint failure is improved. Further, when the copper core ball 11 is mounted on the electrode and reflow is performed, the copper core ball 11 is displaced, causing deterioration in self-alignment. The true sphericity is better than 0.990. In the present invention, the "true sphericity" means a deviation from the true sphere. The true sphericity is obtained by various methods such as a least square circle method (LSC method), a minimum area circle method (MZC method), a maximum inscribed circle method (MIC method), and a minimum circumscribed circle method (MCC method). In detail, the "true sphericity" is an arithmetic mean value obtained by dividing each diameter of 500 Cu balls by the long diameter, and the closer the value is to the upper limit of 1.00, the closer to the positive sphere. In the present invention, the "length of the long diameter" and the "length of the diameter" refer to the length measured by the Ultra Qucik version manufactured by MITUTOYO Co., Ltd., and the ULTRA QV350-PRO measuring device.

. Cu ball diameter: 1~1000μm

The diameter of the Cu balls 1 constituting the present invention is preferably 1 to 1000 μm. If it is within this range, the spherical Cu balls 1 can be stably produced, and the connection short-circuit condition when the terminals are narrow pitches can be suppressed.

Here, for example, when the diameter of the copper core ball 11 of the present invention is about 1 to 300 μm, the "copper core ball" aggregate may also be referred to as "Cu core powder. end". Here, the "Cu core powder" includes an aggregate of a plurality of copper core balls 11 each having the above-described characteristics of the copper core balls 11. For example, the solder paste is blended in a powder form or the like, and is distinguished from the single copper core ball 11 in use form. Similarly, when the solder bumps are formed, they are usually disposed in the form of aggregates, and thus the "Cu core powder" used in this form is distinguished from the single copper core ball 11.

Furthermore, the true sphericity of the copper core ball 11 of the present invention is preferably 0.95 or more. When the true sphericity of the copper core ball 11 is low, when the copper core ball 11 is mounted on the electrode and reflow is performed, the copper core ball 11 is displaced, causing deterioration in self-alignment. The true sphericity is better than 0.990.

Further, the surface of the metal layer 2 constituting the copper core ball 11 of the present invention or the second metal layer may be coated with a flux layer. Further, the surface of the metal layer 2 or the second metal layer constituting the copper core ball 11 may be covered with a solder layer. At this time, the surface of the solder layer may be further covered with the flux layer.

In the present invention, the α-line amount of the metal layer 2, the second metal layer or the solder layer which is the outermost shell in the copper core ball 11 configuration is set at 0.0200 cph, except that the Cu ball 1 is set to a low α-line amount. The present invention can be achieved by /cm ² or less. Therefore, since the copper core ball 11 of the present invention is covered by such a outermost casing, it has a low alpha amount. α dose when the viewpoint of suppressing the soft errors from further high-density mounting, preferably based 0.0020cph / cm ² or less, more preferably ² or less based 0.0010cph / cm. In order to set the α line amount of the copper core ball 11 to 0.0200 cph/cm ² or less, the U and Th contents of the metal layer 2, the second metal layer or the solder layer are each 5 ppb or less. Further, from the viewpoint of suppressing soft errors of current or future high-density mounting, the U and Th contents are preferably 2 ppb or less, respectively.

Furthermore, by dispersing the copper core ball 11 of the present invention in the solder, Can be used as a foam solder. Further, by including the copper core ball 11 of the present invention, it can also be used as a solder paste. Further, the copper core ball 11 of the present invention can also be used for a solder joint in which terminals of an electronic component are joined to each other.

An example of a method of manufacturing the copper core ball 11 of the present invention will be described. The Cu material of the material is placed on a heat-resistant plate such as ceramic (hereinafter referred to as "heat-resistant plate"), and then heated in a furnace together with the heat-resistant plate. The heat-resistant plate is provided with a plurality of circular channels having a hemispherical shape at the bottom. The diameter and depth of the ditch are appropriately set in accordance with the particle diameter of the Cu ball 1, for example, a diameter of 0.8 mm and a depth of 0.88 mm. Moreover, the wafer-shaped Cu material (hereinafter referred to as "wafer material") obtained by cutting the Cu thin wires is placed in the trench of the heat-resistant plate one at a time. The heat-resistant plate into which the wafer material has been placed in the trench is heated to 1100 to 1300 ° C in a furnace filled with ammonia-decomposing gas, and heat-treated for 30 to 60 minutes. At this time, if the furnace temperature becomes equal to or higher than the melting point of Cu, the wafer material is melted and becomes spherical. Then, it is cooled in the furnace and formed into a Cu ball 1 in the ditch of the heat-resistant plate. After cooling, the formed Cu balls 1 are again subjected to heat treatment at a temperature of 800 to 1000 ° C which is less than the melting point of Cu.

Further, other methods are as follows: an atomization method in which molten Cu is dropped from an orifice provided at the bottom of the crucible, the droplet is cooled to form a Cu sphere 1; and a Cu cut metal is heated by a thermoplasm to A method of making balls above 1000 °C. The Cu balls 1 made by the ball can also be reheated for 30 to 60 minutes at a temperature of 800 to 1000 ° C, respectively.

In the method for producing the copper core ball 11 of the present invention, the Cu material belonging to the material of the Cu ball 1 may be subjected to heat treatment at 800 to 1000 ° C before the Cu ball 1 is formed.

For the Cu material belonging to the Cu ball 1 raw material, for example, pellets, welding can be used. Lines, columns, etc. The purity of the Cu material is preferably from 99.9 to 99.99% from the viewpoint that the purity of the Cu sphere 1 is not excessively lowered.

Further, in the case of using a high-purity Cu material, the heat treatment may not be performed, and the holding temperature of the molten Cu may be lowered to 1000 ° C in the same manner as conventionally. According to the above, the heat treatment may be appropriately omitted and changed in accordance with the purity of the Cu material and the amount of the α line. Further, when the Cu balls 1 having a high α-line amount or the Cu balls 1 having a different shape are produced, the Cu balls 1 can be reused as a raw material, and the amount of α-lines can be further reduced.

A method of forming the metal layer 2 on the produced Cu ball 1 may be a method such as a known electrolytic plating method. For example, in the case of forming a Ni plating layer, the Ni plating solution is adjusted by using a Ni base metal, and the Cu ball 1 is immersed in the adjusted Ni plating solution and subjected to electrolysis, thereby forming a Cu ball. A Ni plating layer is formed on the surface of 1. Further, another method of forming the metal layer 2 such as a Ni plating layer may be a known electroless plating method or the like.

Furthermore, the present invention can also be applied to a column, a column, and a particle form in which Cu is a core.

Example 1

Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to the above. In this embodiment, a Cu ball having a high degree of sphericity is produced, a Ni plating layer of a metal layer is formed on the surface of the Cu ball, and the amount of α line is measured.

. Cu ball making

Investigate the production conditions of Cu balls with high true sphericity. Cu particles having a purity of 99.9%, Cu wires having a purity of 99.995% or less, and Cu plates having a purity of more than 99.995% were prepared. Invest in the sputum, and then raise the temperature to 1200 ° C, A heat treatment of 45 minutes was performed. Next, molten Cu was dropped from the orifice provided at the bottom of the crucible, and the generated droplets were cooled to form a Cu sphere, thereby producing a Cu sphere having an average particle diameter of 250 μm. For elemental analysis, U and Th systems were implemented by inductively coupled plasma mass spectrometry (ICP-MS analysis), and other elements were implemented by inductively coupled plasma luminescence spectrometry (ICP-AES analysis).

. True sphericity

The true sphericity is measured using a CNC image measurement system. The device uses an Ultra Qucik version manufactured by MITUTOYO Co., Ltd., and ULTRA QV350-PRO.

.线 line amount

The method for measuring the amount of α line is as follows. The measurement of the amount of α line is an α line measuring device using a gas flow ratio counter. The measurement sample was laid with Cu balls in the bottom of a 300 mm × 300 mm flat shallow bottom container. The measurement sample was placed in an α-ray measuring device, and placed under a flow of PR-10 gas for 24 hours, and then the amount of α line was measured.

In addition, the PR-10 gas (argon 90%-methane 10%) used for the measurement was three weeks or more after the PR-10 gas was filled in the gas cylinder. The reason for using the cylinder for more than 3 weeks is that the α line is not generated due to the enthalpy in the atmosphere of the gas cylinder, and JEDEC STANDARD-Alpha Radiation Measurement In Electronic Materials JESD221 is specified in accordance with JEDEC (Joint Electron Device Engineering Council). The elemental analysis results and the α-line amount of the produced Cu balls are shown in Table 1.

As shown in Table 1, Cu balls having a purity of 99.9% Cu particles and a Cu wire having a purity of 99.995% or less were all found to have a true sphericity of 0.990 or more. On the other hand, as shown in Table 1, a Cu ball having a purity of more than 99.995% Cu plate was used, and the true sphericity was less than 0.95.

Next, a Ni-plated layer was formed on the surface of a Cu ball made of a purity of 99.9% Cu particles using a Ni base metal having a purity of 99.99% or more to produce a copper nucleus. In this embodiment, since the Ni plating layer is deposited by using a Watt bath, the adjustment of the plating solution is carried out as follows. First, a Ni base metal is dissolved in hydrochloric acid to evaporate water and excess hydrochloric acid gas to produce a crystal of Ni chloride. Further, the Ni base metal is dissolved in sulfuric acid to evaporate water and excess sulfuric acid gas to produce a crystal of sulfuric acid Ni. Nitric acid Ni and sulfuric acid Ni were dissolved by 1/3 of the ion exchange water used in the bath construction. The remaining 2/3 of the ion-exchanged water is heated to 60 ° C, and after the boric acid is dissolved, a mixed solution of Ni chloride and Ni-sulfuric acid is added, and the mixture is thoroughly stirred, and the Ni plating is terminated by completely dissolving Ni, Ni, and boric acid. Liquid adjustment.

Next, in the plating tank of the plating apparatus, the Ni plating solution which was bathed by the above method was filled, and Cu balls were thrown, and the Cu balls were immersed in the Ni plating solution. Then, by applying an electric current and performing electrolysis, Ni plating is applied to the surface of the Cu ball. In this embodiment, Electroplating is performed while flowing the Cu ball and the plating solution, but the method of flowing is not particularly limited. For example, in the case of the barrel type electrolytic plating method, the Cu ball and the plating solution can be caused to flow by rotating the barrel by a specific number of rotations. At this time, the liquid temperature of the Ni plating solution was maintained at 40 to 60 °C. Further, the electric quantity is set to 0.0019 coulomb, and for example, a Ni plating layer of 2 μm (see T of FIG. 1) is formed on one side of one Cu sphere having a diameter of 100 μm. If the Ni film thickness has grown to the target ball diameter, the plating apparatus is stopped, and a copper-nuclear ball having a Ni-plated layer formed on the surface of the Cu ball is recovered.

The α-line amount of the copper nucleus was measured in the same manner as in the above-described Cu ball. Further, the true sphericity of the relevant copper nucleus was also measured in accordance with the same conditions as those of the Cu ball. The results of these measurements are shown in Table 2.

Example 2

In Example 2, a Cu ball made of a Cu wire having a purity of 99.995% or less shown in Table 1 was used, and a Ni plating treatment was performed in the same manner as in Example 1 to prepare a copper core in which a Ni plating layer was formed on the surface of the Cu ball. The ball was subjected to the same evaluation as in Example 1. The α-line amount and the true sphericity were measured in the same manner as in Example 1 with respect to the produced copper nucleus. The measurement results are shown in Table 2.

Example 3

In Example 3, a Cu ball made of a Cu plate having a purity of more than 99.995% as shown in Table 1 was used, and a Ni plating treatment was performed in the same manner as in Example 1 to prepare a copper core in which a Ni plating layer was formed on the surface of the Cu ball. The ball was subjected to the same evaluation as in Example 1. The α-line amount and the true sphericity were measured in the same manner as in Example 1 with respect to the produced copper nucleus. The measurement results are shown in Table 2.

According to Table 2, the α-line amount of the copper core ball of Example 1 was less than 0.0010 cph/cm ² . According to the copper core ball of Example 1, it was confirmed that the amount of α line can be reduced even if a Ni plating layer is formed on the surface of the Cu ball. Further, the α-line amount of the copper nucleus balls produced in Example 1 is not described in Table 1, but the α-line rise was not observed after one year after the production.

Similarly, in Example 2 and Example 3, the amount of α-line of the copper core ball was less than 0.0010 cph/cm ² . According to the copper core balls of Examples 2 and 3, it was confirmed that the amount of α line can be reduced even in the case where a Ni plating layer is formed on the surface of the Cu ball. Further, the α-line amount of the copper nucleus balls produced in Example 2 and Example 3 is not described in Table 1, but the α-line rise has not been observed after one year after the production.

In addition, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications added to the above-described embodiments are possible without departing from the gist of the present invention. For example, in the above embodiment, an example in which a Ni plating layer is used for the metal layer is described. However, when the metal layer is a Co plating layer or an Fe plating layer, the same amount as the Ni plating layer can be obtained, and a low α amount can be obtained. Highly spherical nucleus ball.

1‧‧‧Cu Ball

2‧‧‧metal layer

11‧‧‧copper ball

Claims (11)

A copper nucleus ball comprising: a Cu ball; and a metal layer covered with the surface of the Cu ball and selected from elements selected from Ni, Co, and Fe; wherein the Cu ball system has a purity of 99.9 % or more and 99.995% or less, U content is 5 ppb or less, Th content is 5 ppb or less, and content of at least one of Pb and Bi is 1 ppm or more, true sphericity is 0.95 or more, and α linear amount is 0.0200 cph/cm. ² or less. A copper nucleus ball comprising: a Cu ball; and a metal layer covered with the surface of the Cu ball and selected from elements selected from Ni, Co, and Fe; wherein the Cu ball system has a purity of 99.9 % or more and 99.995% or less, and the content of at least one of Pb and Bi is 1 ppm or more, and the true sphericity is 0.95 or more; the metal layer U content is 5 ppb or less, the Th content is 5 ppb or less, and the α line amount is 0.0200 cph/cm ² or less. A copper nucleus ball comprising: a Cu ball; a metal layer covered with an element of the surface of the Cu ball and selected from one or more of Ni, Co, and Fe; and a second metal layer covered with the above The surface of the metal layer is composed of one or more elements selected from the group consisting of Ni, Co, and Fe which are not contained in the metal layer, and is characterized in that the Cu ball system has a purity of 99.9% or more and 99.995% or less, and is in Pb and Bi. The content of at least one of them is 1 ppm or more, and the true sphericity is 0.95 or more. The second metal layer has a U content of 5 ppb or less, a Th content of 5 ppb or less, and an α line amount of 0.0200 cph/cm ² or less. A copper nucleus ball comprising: a Cu ball; a metal layer covered with a surface of the Cu ball and selected from elements selected from Ni, Co, and Fe; and a solder layer coated with the metal layer The surface of the Cu sphere is 99.9% or more and 99.995% or less, and the content of at least one of Pb and Bi is 1 ppm or more, and the true sphericity is 0.95 or more; Below 5 ppb, the Th content is 5 ppb or less, and the α line amount is 0.0200 cph/cm ² or less. A copper nucleus ball comprising: a Cu ball; a metal layer covered with an element of the surface of the Cu ball and selected from one or more of Ni, Co, and Fe; and a second metal layer covered with the above The surface of the metal layer is composed of an element selected from the group consisting of Ni, Co, and Fe which are not contained in the metal layer; and a solder layer covering the surface of the second metal layer; The purity of the Cu ball system is 99.9% or more and 99.995% or less, and the content of at least one of Pb and Bi is 1 ppm or more, and the true sphericity is 0.95 or more; the content of the solder layer U is 5 ppb or less, and the Th content is 5 ppb. Hereinafter, the amount of α line is 0.0200 cph/cm ² or less. The copper core ball according to any one of claims 1 to 5, wherein the α line amount is 0.0200 cph/cm ² or less. The copper core ball according to any one of claims 1 to 5, wherein the α line amount is 0.0010 cph/cm ² or less. The copper core ball according to any one of claims 1 to 5, further comprising a flux layer covering the metal layer, the second metal layer or the surface of the solder layer. A welding head characterized by using the copper core ball of any one of claims 1 to 8. A foam solder characterized by using the copper core ball of any one of claims 1 to 8. A solder paste characterized by using a copper core ball according to any one of claims 1 to 8.