WO2021206096A1

WO2021206096A1 - Solder particles, production method for solder particles, and substrate with solder particles

Info

Publication number: WO2021206096A1
Application number: PCT/JP2021/014656
Authority: WO
Inventors: 勝将宮地; 芳則江尻; 邦彦赤井; 純一畠
Original assignee: 昭和電工マテリアルズ株式会社
Priority date: 2020-04-06
Filing date: 2021-04-06
Publication date: 2021-10-14
Also published as: TW202146679A; CN115362044A; JPWO2021206096A1

Abstract

A production method for solder particles, the production method including a preparation step for preparing a substrate that has a plurality of protrusions, a solder layer formation step for forming a solder layer on at least a portion of the protrusions of the substrate, and a fusion step for fusing the solder layer that has been formed on the protrusions and thereby forming solder particles on the protrusions.

Description

Solder particles, manufacturing method of solder particles, and substrate with solder particles

The present invention relates to solder particles, a method for producing solder particles, and a substrate with solder particles.

Conventionally, the use of solder particles has been studied as conductive particles to be blended in anisotropic conductive materials such as anisotropic conductive films and anisotropic conductive pastes. For example, Patent Document 1 describes a conductive paste containing a thermosetting component and a plurality of solder particles that have been subjected to a specific surface treatment.

Japanese Unexamined Patent Publication No. 2016-76494

In recent years, as the definition of circuit members has become higher, the connection points have become smaller, and the conduction reliability and insulation reliability required for anisotropic conductive materials have increased. In order to ensure conduction reliability and insulation reliability, it is necessary to miniaturize and homogenize the conductive particles blended in the anisotropic conductive material, but in the conventional method for producing solder particles, small average particles are required. It has been difficult to produce solder particles having both a diameter and a narrow particle size distribution.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing solder particles capable of producing solder particles having both a small average particle size and a narrow particle size distribution. Another object of the present invention is to provide solder particles having both a small average particle size and a narrow particle size distribution by the above manufacturing method.

One aspect of the present invention includes a preparatory step of preparing a substrate having a plurality of convex portions, a solder layer forming step of forming a solder layer on the convex portions of at least a part of the substrate, and forming on the convex portions. The present invention relates to a method for producing solder particles, which comprises a fusion step of fusing the said solder layers to form solder particles on the convex portion.

According to the above manufacturing method, solder particles having a desired particle size can be obtained with a narrow particle size distribution by appropriately adjusting the shape of the convex portion and the thickness of the solder layer. That is, according to the above manufacturing method, it is possible to easily manufacture solder particles having both a small average particle size and a narrow particle size distribution, which was difficult to manufacture in the past.

In one aspect, the convex portion may be columnar or frustum-shaped.

In one aspect, the substrate may have a first surface comprising a plurality of convex portions and a bottom portion formed between the convex portions, and the projection of the bottom portion in the projected area of the first surface. The area ratio may be 8% or more.

The manufacturing method according to one aspect may form the solder layer on the convex portion by at least one method selected from the group consisting of plating, vapor deposition, sputtering and spray coating in the solder layer forming step.

The manufacturing method according to one aspect may further include a reduction step of exposing the solder layer formed on the convex portion to a reducing atmosphere before the fusion step.

In the manufacturing method according to one aspect, in the fusion step, the solder layer formed on the convex portion may be fused in a reducing atmosphere.

In one embodiment, the solder layer may contain at least one selected from the group consisting of tin, tin alloys, indium and indium alloys.

In one embodiment, the solder layer comprises In—Bi alloy, In—Sn alloy, In—Sn—Ag alloy, Sn—Au alloy, Sn—Bi alloy, Sn—Bi-Ag alloy, Sn—Ag—Cu alloy and It may contain at least one selected from the group consisting of Sn—Cu alloys.

Another aspect of the present invention is that the average particle size is 100 nm or more and less than 1 μm, and C.I. V. For solder particles with a value of 20% or less.

The solder particles according to one aspect are obtained when a quadrangle circumscribing the projected image of the solder particles is created by two pairs of parallel lines and the distances between the opposing sides are X and Y (however, Y <X). X and Y may satisfy the following formula.
0.8 <Y / X <1.0

The solder particles according to one embodiment may contain at least one selected from the group consisting of tin, tin alloys, indium and indium alloys.

The solder particles according to one embodiment include In—Bi alloy, In—Sn alloy, In—Sn—Ag alloy, Sn—Au alloy, Sn—Bi alloy, Sn—Bi-Ag alloy, Sn—Ag—Cu alloy and Sn. -It may contain at least one selected from the group consisting of Cu alloys.

Yet another aspect of the present invention relates to a substrate with solder particles, comprising a substrate having a plurality of convex portions and a plurality of solder particles arranged on the convex portions of the substrate. Such a substrate with solder particles can be easily manufactured by the fusion step in the above-mentioned manufacturing method. Such a substrate with solder particles facilitates transportation, storage and management of the solder particles.

In one embodiment, the average particle size of the solder particles may be 100 nm or more and less than 1 μm, and the C.I. V. The value may be 20% or less.

According to the present invention, there is provided a method for producing solder particles capable of producing solder particles having both a small average particle size and a narrow particle size distribution. Further, according to the present invention, solder particles having both a small average particle size and a narrow particle size distribution are provided.

FIG. 1A is a plan view schematically showing an example of a substrate, and FIG. 1B is a cross-sectional view taken along the line Ib-Ib shown in FIG. 1A. FIG. 2A is a cross-sectional view schematically showing an example of the convex portion, and FIG. 2B is a cross-sectional view schematically showing another example of the convex portion. 3A to 3E are diagrams schematically showing an example of the shape of the cross section perpendicular to the height direction of the convex portion. FIG. 4 is a cross-sectional view schematically showing an example of a state in which a solder layer is formed on a convex portion of a substrate. FIG. 5 is a cross-sectional view schematically showing an example of a state in which solder particles are formed on the convex portion of the substrate. FIG. 6 is a cross-sectional view schematically showing another example of a state in which a solder layer is formed on a convex portion of a substrate. FIG. 7 is a cross-sectional view schematically showing another example of a state in which solder particles are formed on the convex portion of the substrate. FIG. 8 is a diagram showing distances X and Y (provided that Y <X) between opposite sides when a quadrangle circumscribing a projected image of solder particles is created by two pairs of parallel lines. FIG. 9 is an SEM image of the substrate prepared in Example 13. FIG. 10 is an SEM image of the state in which the solder layer is formed on the convex portion of the substrate in Example 13. FIG. 11 is an SEM image of the state in which the solder particles are formed on the convex portion of the substrate in Example 13. FIG. 12 is an SEM image of the solder particles obtained in Example 2. FIG. 13 is an SEM image of the solder particles obtained in Comparative Example 2.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. The numerical range indicated by using "-" indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step may be replaced with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

<Manufacturing method of solder particles>
The method for producing solder particles according to the present embodiment includes a preparatory step of preparing a substrate having a plurality of convex portions, a solder layer forming step of forming a solder layer on at least a part of the convex portions of the substrate, and a solder layer forming step on the convex portions. It includes a fusion step of fusing the solder layers formed in the above to form solder particles on the convex portion.

According to the above manufacturing method, solder particles having a desired particle size can be obtained with a narrow particle size distribution by appropriately adjusting the shape of the convex portion and the thickness of the solder layer. That is, according to the above manufacturing method, solder particles having both a small average particle size and a narrow particle size distribution (for example, an average particle size of 100 nm to 30 μm and a CV value of 20%), which was difficult to manufacture in the past, are achieved. The following solder particles) can be easily manufactured.

Further, according to the above manufacturing method, it is possible to obtain solder particles that are difficult to manufacture by the conventional method. For example, according to the above manufacturing method, extremely small solder particles having an average particle diameter of 100 nm or more and less than 1 μm can be obtained with a narrow particle size distribution (for example, a CV value of 20% or less).

Hereinafter, a method for manufacturing solder particles will be described with reference to FIGS. 1 to 7.

First, prepare the substrate for forming the solder layer (preparation process). FIG. 1A is a diagram schematically showing an example of a substrate, and FIG. 1B is a cross-sectional view taken along the line Ib-Ib shown in FIG. 1A. The substrate 10 shown in FIG. 1A has a plurality of convex portions 11. The plurality of convex portions 11 may be regularly arranged in a predetermined pattern. In this case, the solder particles formed on the convex portion 11 can be transferred to a resin material or the like so that the solder particles can be arranged regularly.

The substrate 10 may have a first surface 10a including a plurality of convex portions 11 and a bottom portion 12 formed between the convex portions 11. The first surface 10a may be composed of a top portion 11a of the convex portion 11 and a bottom surface 12a composed of the bottom portion 12.

If the convex portions 11 are too close to each other, the solder particles on the convex portions 11 may come into contact with each other and fuse with each other to generate solder particles having a large particle size in the fusion step described later. From the viewpoint of suppressing the formation of the large particle size particles, the ratio of the projected area of the bottom 12 to the projected area of the first surface 10a (that is, the area of the bottom surface 12a to the projected area of the first surface 10a). The ratio) is preferably 8% or more, more preferably 10% or more, and may be 15% or more. The upper limit of the ratio is not particularly limited. From the viewpoint of further improving the production efficiency of the solder particles, for example, it may be 95% or less, preferably 90% or less, and further preferably 80% or less.

In FIGS. 1A and 1B, the convex portion 11 is formed in a columnar shape, but the shape of the convex portion 11 is not limited to this. The convex portion 11 may have a columnar shape such as a columnar shape, an elliptical columnar shape, a triangular columnar shape, a square columnar shape, or a polygonal columnar shape, and may have a conical frustum shape, an elliptical frustum shape, a triangular frustum shape, or a square frustum shape. , It may be a frustum shape such as a polygonal frustum shape.

Although the top portion 11a of the convex portion 11 is described as a flat surface in FIGS. 1A and 1B, the top portion 11a does not necessarily have to be a flat surface. For example, the top 11a may have a recess or a protrusion. From the viewpoint of improving the retention of the solder particles formed on the top portion 11a, it is preferable that the top portion 11a has a recess in the center.

FIG. 2A is a cross-sectional view schematically showing an example of a convex portion, and FIG. 2B is a cross-sectional view schematically showing an example of a convex portion. The convex portion 11 shown in FIG. 2A is a prismatic convex portion, and the convex portion 21 shown in FIG. 2B is a frustum-shaped convex portion.

Convex portion 11, the width _{D 11} at the top 11a, and the width _{D 12} in contact surface between the bottom portion 12 may be substantially the same. The width D ₁₁ and the width D ₁₂ are not particularly limited, and may be, for example, 200 nm or more, preferably 400 nm or more, and more preferably 1.0 μm or more from the viewpoint of avoiding contact between solder particles on adjacent convex portions. Further, the width D ₁₁ and the width D ₁₂ may be, for example, 10 μm or less, preferably 4.0 μm or less, and more preferably 2.0 μm or less from the viewpoint of producing ultrafine particle size solder particles having a particle size of 800 nm or less.

_{The height H 1} of the convex portion 11 is not particularly limited, and may be, for example, _{10% or more of the width D 11} , avoiding contact with the solder on the bottom portion 12, and making it easier to obtain more accurate solder particles. preferably at least 25% of the width _{D 11} from the viewpoint, more preferably at least 50% of the width _{D 11.} The height _{H 1} of the convex portion 11, for example, may be less 1000% of the width _{D 11,} avoiding the breakage of the projections 11, 500% of the width _{D 11} from the viewpoint of enhancing the recovery rate of the solder particles The following is preferable, and 300% or less of _{the width D 11 is more preferable.}

The convex portion 11 can be arranged at an arbitrary position on the substrate 10.

_{The distance L 1} between the adjacent convex portions 11 is not particularly limited, but from the viewpoint of suppressing the formation of large particle size particles due to the contact and fusion of the solder particles on the convex portions 11, for example, it is 3% or more of the _{width D 11.} be in a, preferably 8% or more of the width _{D 11,} more preferably at least 15% of the width _{D 11.} The distance _{L 1} between the convex portions 11 adjacent, for example may be up to 1000% of the width _{D 11,} from the viewpoint of further improving the manufacturing efficiency of the solder particles, preferably 500% or less of the width _{D 11,} More preferably, it is 200% or less of the _{width D 11.}

_{The width D 21 at} the top 21 a of the convex portion 21 is smaller than the _{width D 22 at the contact surface} with the bottom 22. The width D ₂₁ is not particularly limited, and may be, for example, 200 nm or more, preferably 400 nm or more, and more preferably 1.0 μm or more from the viewpoint of avoiding contact between solder particles on adjacent convex portions. The width D ₂₁ may be, for example, 10 μm or less, preferably 4.0 μm or less, and more preferably 2.0 μm or less from the viewpoint of producing ultrafine particle size solder particles having a particle size of 800 nm or less. The width D ₂₂ is not particularly limited, and may be, for example, 200 nm or more, preferably 400 nm or more, and more preferably 1.0 μm or more from the viewpoint of avoiding contact between solder particles on adjacent convex portions. The width D ₂₂ may be, for example, 10 μm or less, preferably 4.0 μm or less, and more preferably 2.0 μm or less, from the viewpoint of producing ultrafine particle size solder particles having a particle size of 800 nm or less.

The ratio of the width D ₂₁ to the width D ₂₂ _{(D 22 /} D ₂₁ ) is not particularly limited, and may be, for example, 1.1 or more. From the viewpoint of avoiding contact between solder particles on the adjacent convex portion, 1. 3 or more is preferable, and 1.5 or more is more preferable. The ratio (D _{22 /} D ₂₁ ) may be, for example, 3.0 or less, preferably 2.0 or less.

The difference between the width D ₂₁ and the width D ₂₂ _{(D 22-} D ₂₁ ) is not particularly limited and may be, for example, 2.0 μm or less, reducing the amount of solder supplied to the side surface and the bottom 22 of the convex portion 21. From the viewpoint that more accurate solder particles can be easily obtained, 1.0 μm or less is preferable, and 500 nm or less is more preferable.

_{The height H 2} of the convex portion 21 is not particularly limited, and may be, for example, _{10% or more of the width D 22} , avoiding contact with the solder on the bottom portion 12, and making it easier to obtain more accurate solder particles. preferably at least 25% of the width _{D 22} from the viewpoint, more preferably at least 50% of the width _{D 22.} The height _{H 2} of the convex portion 21, for example, may be less 1000% of the width _{D 22,} avoiding the breakage of the projections 11, 500% of the width _{D 22} from the viewpoint of enhancing the recovery rate of the solder particles The following is preferable, and 300% or less of _{the width D 22 is more preferable.}

_{The distance L 2} between the adjacent convex portions 21 is not particularly limited, but from the viewpoint of suppressing the formation of large particle size particles due to the contact and fusion of the solder particles on the convex portions 21, for example, it is 3% or more of the _{width D 22.} be in a, preferably 8% or more of the width _{D 22,} more preferably at least 15% of the width _{D 22.} The distance _{L 2} between adjacent convex portions 21 is, for example may be up to 1000% of the width _{D 22,} from the viewpoint of further improving the manufacturing efficiency of the solder particles, preferably 500% or less of the width _{D 22,} More preferably, it is 200% or less of the _{width D 22.}

The shape of the cross section perpendicular to the height direction of the convex portion 11 and the convex portion 21 is not particularly limited, and may be, for example, the shape shown in FIG. 3A to 3E are diagrams schematically showing an example of the shape of the cross section perpendicular to the height direction of the convex portion.

The material constituting the substrate 10 is not particularly limited, and a material having heat resistance that does not deteriorate at the melting temperature of the solder layer is preferable. The material constituting the substrate 10 may be, for example, an inorganic material such as silicon, various ceramics, glass, or stainless steel, or an organic material such as various resins.

The method for producing the substrate 10 is not particularly limited, and the substrate 10 can be appropriately produced by a known method (for example, a photolithography method) capable of forming the convex portion 11.

Next, a solder layer is formed on at least a part of the convex portion of the substrate (solder layer forming step). As the solder material for forming the solder layer, a commercially available solder material can be used without particular limitation, and can be appropriately selected depending on the desired characteristics of the solder particles, the method for forming the solder layer, and the like. For example, when forming a solder layer by sputtering, a solder plate that can be used as a target for sputtering is selected.

The solder material may include, for example, tin or a tin alloy. As the tin alloy, for example, In—Sn alloy, In—Sn—Ag alloy, Sn—Au alloy, Sn—Bi alloy, Sn—Bi—Ag alloy, Sn—Ag—Cu alloy, Sn—Cu alloy and the like are used. be able to. Specific examples of these tin alloys include the following examples.
-In-Sn (In 52% by mass, Bi48% by mass, melting point 118 ° C)
-In-Sn-Ag (In 20% by mass, Sn77.2% by mass, Ag 2.8% by mass, melting point 175 ° C.)
-Sn-Bi (Sn43% by mass, Bi57% by mass, melting point 138 ° C.)
-Sn-Bi-Ag (Sn42% by mass, Bi57% by mass, Ag1% by mass, melting point 139 ° C.)-Sn-Ag-Cu (Sn96.5% by mass, Ag3% by mass, Cu0.5% by mass, melting point 217 ° C.)
-Sn-Cu (Sn99.3% by mass, Cu0.7% by mass, melting point 227 ° C)
-Sn-Au (Sn21.0% by mass, Au79.0% by mass, melting point 278 ° C.)

The solder material may include, for example, indium or an indium alloy. As the indium alloy, for example, an In—Bi alloy, an In—Ag alloy, or the like can be used. Specific examples of these indium alloys include the following examples.
-In-Bi (In66.3% by mass, Bi33.7% by mass, melting point 72 ° C.)
-In-Bi (In33.0% by mass, Bi67.0% by mass, melting point 109 ° C)
-In-Ag (In97.0% by mass, Ag3.0% by mass, melting point 145 ° C)

The tin alloy or indium alloy can be selected as the solder material according to the use of the solder particles (temperature at the time of use) and the like. For example, when it is desired to obtain solder particles used for fusion at a low temperature, an In—Sn alloy or a Sn—Bi alloy may be adopted. In this case, solder particles that can be fused at 150 ° C. or lower can be obtained. When a solder material having a high melting point such as a Sn—Ag—Cu alloy or a Sn—Cu alloy is used, solder particles capable of maintaining high reliability even after being left at a high temperature can be obtained.

The solder material may further contain one or more selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P and B. Among these elements, Ag or Cu may be contained from the following viewpoints. That is, when the solder material contains Ag or Cu, the melting point of the obtained solder particles can be lowered to about 220 ° C., and the solder particles having excellent bonding strength with the electrode can be obtained, so that better conduction reliability can be obtained. The effect of obtaining sex is achieved.

The Cu content of the solder material is, for example, 0.05 to 10% by mass, and may be 0.1 to 5% by mass or 0.2 to 3% by mass. When the Cu content is 0.05% by mass or more, it becomes easy to obtain solder particles capable of achieving good solder connection reliability. Further, when the Cu content is 10% by mass or less, solder particles having a low melting point and excellent wettability can be easily obtained, and as a result, the connection reliability of the joint portion by the solder particles tends to be improved.

The Ag content of the solder material is, for example, 0.05 to 10% by mass, and may be 0.1 to 5% by mass or 0.2 to 3% by mass. When the Ag content is 0.05% by mass or more, it becomes easy to obtain solder particles capable of achieving good solder connection reliability. Further, when the Ag content is 10% by mass or less, solder particles having a low melting point and excellent wettability can be easily obtained, and as a result, the connection reliability of the joint portion by the solder particles tends to be improved.

In the solder layer forming step, a solder layer is formed on each of the convex portions of the substrate. The solder layer forming step may be a step of forming a solder layer on all the convex portions of the substrate prepared in the preparation step, and is a step of forming a solder layer on a part of the convex portions of the substrate prepared in the preparation step. May be good.

In the solder layer forming step, the method of forming the solder layer is not particularly limited. Examples of the method for forming the solder layer include plating, vapor deposition, sputtering, and spray coating. Of these, sputtering is preferable from the viewpoint that the thickness of the solder layer can be strictly controlled and solder particles having a smaller particle size distribution can be easily obtained.

In the solder layer forming step, the amount of the solder layer formed is not particularly limited, and may be appropriately changed according to the desired size of the solder particles. By appropriately changing the amount of the solder layer formed on the convex portion, the size of the solder particles formed on the convex portion can be easily adjusted.

In the solder layer forming step, the solder layer may be formed only on the convex portion of the substrate, and the solder layer may be formed on a portion other than the convex portion of the substrate. For example, in the solder layer forming step, a solder layer may be formed on the convex portion and the bottom portion of the substrate.

FIG. 4 is a cross-sectional view schematically showing an example of a state in which the solder layer 50 is formed on the convex portion 11 of the substrate 10. In the embodiment shown in FIG. 4, the solder layer is formed only on the convex portion 11 of the substrate 10.
The solder layer is formed using the above-mentioned solder materials and may contain at least one selected from the group consisting of tin, tin alloys, indium and indium alloys. The solder layer includes In—Bi alloy, In—Sn alloy, In—Sn—Ag alloy, Sn—Au alloy, Sn—Bi alloy, Sn—Bi-Ag alloy, Sn—Ag—Cu alloy and Sn—Cu. It may include at least one selected from the group consisting of alloys.

FIG. 6 is a cross-sectional view schematically showing another example of a state in which the solder layer 50 is formed on the convex portion 11 of the substrate 10. In the embodiment shown in FIG. 6, the solder layer 50 is formed on the convex portion 11 of the substrate 10, and the solder layer 51 is also formed on the bottom portion 12 of the substrate 10. In this embodiment, the amount of the solder layer 50 formed on the convex portion 11 is, for example, 20% with respect to the total volume of the solder layers formed on the substrate (total volumes of the solder layer 50 and the solder layer 51). The above is preferable, 30% or more is more preferable, 50% or more is further preferable, and 60% or more is further preferable.

Next, the solder layers formed on the convex portions are fused to form solder particles on the convex portions (fusion step). In the fusion process, the solder layer formed on the convex portion is united by melting and spheroidized by surface tension to form solder particles.

Examples of the method of melting the solder layer include a method of heating the solder layer to a temperature equal to or higher than the melting point of the solder material constituting the solder layer. Due to the influence of the oxide film, the solder layer may not melt even if it is heated at a temperature equal to or higher than the melting point, it may not spread even if it melts, or it may not unify. Therefore, it is preferable to expose the solder layer to a reducing atmosphere to remove the oxide film on the surface of the solder layer, and then heat the solder layer to a temperature equal to or higher than the melting point of the solder material. Further, it is preferable that the solder layer is melted in a reducing atmosphere. By melting the solder layer in a reducing atmosphere, melting, wetting and spreading of the solder layer and coalescence can proceed more efficiently.

The method for creating a reducing atmosphere is not particularly limited as long as the above effects can be obtained, and for example, there is a method using hydrogen gas, hydrogen radical, formic acid gas, or the like. For example, by using a hydrogen reduction furnace, a hydrogen radical reduction furnace, a formic acid reduction furnace, or a conveyor furnace or a continuous furnace thereof, the solder layer can be melted in a reduction atmosphere. These devices may be equipped with a heating device, a chamber filled with an inert gas (nitrogen, argon, etc.), a mechanism for evacuating the inside of the chamber, etc., which makes it easier to control the reducing gas. Become. Further, if the inside of the chamber can be evacuated, voids can be removed by reducing the pressure after the solder layer is melted and coalesced, and solder particles having further excellent connection stability can be obtained.

Profiles such as reduction of the solder layer, melting conditions, temperature, and adjustment of the atmosphere in the furnace may be appropriately set in consideration of the melting point, particle size, recess size, substrate material, etc. of the solder layer. For example, a substrate having a solder layer formed on a convex portion is inserted into a furnace, evacuated, and then a reducing gas is introduced to fill the inside of the furnace with the reducing gas to form an oxide film on the surface of the solder layer. After removal, the reducing gas is removed by evacuation, and then heated above the melting point of the solder layer to melt and coalesce the solder layer to form solder particles on the convex parts, and then nitrogen gas. After filling, the temperature inside the furnace can be returned to room temperature to obtain solder particles. Further, for example, a substrate having a solder layer formed on a convex portion is inserted into a furnace, evacuated, and then a reducing gas is introduced to fill the inside of the furnace with the reducing gas, and then a heater in the furnace is used. After heating the solder layer to remove the surface oxide film of the solder layer, the reducing gas is removed by vacuuming, and then the solder layer is heated to a temperature equal to or higher than the melting point of the solder layer to melt and coalesce the solder layer. After forming the solder particles on the convex portion, the temperature inside the furnace can be returned to room temperature after filling with nitrogen gas to obtain the solder particles. By heating the solder layer in a reducing atmosphere, there is an advantage that the reducing power is increased and the surface oxide film of the solder layer can be easily removed.

Further, for example, a substrate having a solder layer formed on a convex portion is inserted into a furnace, and after vacuuming, a reducing gas is introduced to fill the inside of the furnace with the reducing gas, and a heater in the furnace is used. The substrate is heated above the melting point of the solder layer to remove the surface oxide film of the solder layer by reduction, and at the same time, the solder layer is melted and united to form solder particles on the convex portions, which are reduced by vacuuming. After removing the gas and further reducing the voids in the solder particles, the solder particles can be obtained by filling with nitrogen gas and then returning the temperature in the furnace to room temperature. In this case, since it is sufficient to adjust the temperature rise and fall in the furnace once, there is an advantage that the processing can be performed in a short time.

After forming the solder particles on the above-mentioned convex portion, the inside of the furnace may be made into a reducing atmosphere again, and a step of removing the surface oxide film that could not be completely removed may be further added. As a result, it is possible to reduce the residue such as the solder layer remaining without being fused and a part of the oxide film remaining without being fused.

When using an atmospheric pressure conveyor furnace, a substrate having a solder layer formed on a convex portion can be placed on a conveyor and passed through a plurality of zones in succession to obtain solder particles. For example, a substrate having a solder layer formed on a convex portion is placed on a conveyor set at a constant speed, passed through a zone filled with an inert gas such as nitrogen or argon at a temperature lower than the melting point of the solder layer, and then passed. The surface oxide film of the solder layer is removed by passing through a zone where a reducing gas such as formic acid gas having a temperature lower than the melting point of the solder layer is present, and then nitrogen, argon or the like having a temperature higher than the melting point of the solder layer is not used. Solder particles can be obtained by passing through a zone filled with active gas to melt and coalesce the solder layer, and then through a cooling zone filled with an inert gas such as nitrogen or argon. For example, a substrate having a solder layer formed on a convex portion is placed on a conveyor set at a constant speed, passed through a zone filled with an inert gas such as nitrogen or argon at a temperature equal to or higher than the melting point of the solder layer, and then passed. The surface oxide film of the solder layer is removed, melted and coalesced by passing through a zone where a reducing gas such as formic acid gas having a temperature equal to or higher than the melting point of the solder layer exists, and then inert such as nitrogen and argon. Solder particles can be obtained by passing through a gas-filled cooling zone. Since the conveyor furnace can be processed at atmospheric pressure, a film-like material can be continuously processed by roll-to-roll. For example, a continuous roll product of a substrate in which a solder layer is formed on a convex portion is produced, a roll unwinder is installed on the inlet side of the conveyor furnace, and a roll winder is installed on the outlet side of the conveyor furnace to maintain a constant speed. By transporting the substrate and passing it through each zone in the conveyor furnace, the solder layer formed on the convex portion can be fused.

The formed solder particles may be transported and stored in a state of being formed on the convex portion of the substrate. A substrate in which solder particles are formed on the convex portion can be suitably handled as a substrate with solder particles. A substrate with solder particles includes a substrate having a plurality of convex portions and a plurality of solder particles arranged on the convex portions of the substrate. The average particle size of the solder particles is 100 nm or more and less than 1 μm, and the C.I. V. The value may be 20% or less. The formed solder particles may be recovered from the convex portion. Further, the resin material may be arranged so as to face the convex portion of the substrate, and the solder particles on the convex portion may be transferred to the resin material. At this time, if the convex portions are regularly arranged, the solder particles can be regularly arranged on the resin material.

FIG. 5 is a cross-sectional view schematically showing an example of a state in which solder particles are formed on the convex portion of the substrate. The substrate 100 with solder particles shown in FIG. 5 is obtained by subjecting the substrate 10 on which the solder layer 50 shown in FIG. 4 is formed to a fusion step. In the base 100 with solder particles, the solder particles 1 are formed on the convex portions 11 of the base 10 having a plurality of convex portions 11.

FIG. 7 is a cross-sectional view schematically showing another example of a state in which solder particles are formed on the convex portion of the substrate. The base 110 with solder particles shown in FIG. 7 is obtained by subjecting the base 10 on which the solder layer 50 and the solder layer 51 shown in FIG. 6 are formed to a fusion step. In the base 110 with solder particles, the solder particles 1 are formed on the convex portions 11 of the base 10 having a plurality of convex portions 11. Further, in the base 110 with solder particles, solder particles 2 derived from the solder layer 51 are formed on the bottom portion 12 between the convex portions 11. Since the solder particles 2 do not always show a small particle size distribution, in this embodiment, it is preferable to collect or transfer only the solder particles 1. The solder particles 2 are fixed to the bottom portion 12 of the substrate 10 and exist at a position lower than the solder particles 1 on the convex portion 11. Therefore, for example, by arranging the resin material so as to face the convex portion 11 of the substrate 10 and transferring the solder particles 1 on the convex portion 11 to the resin material, only the solder particles 1 can be recovered. ..

With the manufacturing method of this embodiment, it is possible to form solder particles having a uniform size regardless of the material and shape of the solder material. For example, indium-based solder can be precipitated by plating, but it is difficult to precipitate it in the form of particles, and it is soft and difficult to handle. However, in the production method of the present embodiment, by using an indium-based solder plate as a raw material, indium-based solder particles having a uniform particle size can be easily produced. Further, since the formed solder particles can be handled in a state of being formed on the convex portion of the substrate, the solder particles can be transported and stored without being deformed. Further, since the formed solder particles are simply formed on the convex portion of the substrate, they can be easily taken out, and the solder particles can be collected, surface-treated, etc. without being deformed.

Further, the solder material may have a large variation in size and particle size distribution, or may have a distorted shape, and if a solder layer can be formed on the convex portion by a method such as sputtering, plating, or spray coating, the present invention. It can be used as a raw material for the production method of the embodiment.

Further, in the manufacturing method of the present embodiment, the shape of the convex portion of the substrate can be freely designed by a photolithography method, an imprint method, a machining method, an electron beam processing method, a radiation processing method, or the like. Since the size of the solder particles depends on the amount of the solder layer formed on the convex portion, the size of the solder particles can be freely designed by the design of the convex portion in the manufacturing method of the present embodiment.

(Solder particles)
The solder particles according to this embodiment have an average particle size of 100 nm or more and 30 μm or less, and have a C.I. V. The value is 20% or less, preferably the average particle size is 100 nm or more and less than 1 μm, C.I. V. The value is 20% or less. Such solder particles have both a small average particle size and a narrow particle size distribution, and can be suitably used as conductive particles applied to an anisotropic conductive material having high conductivity reliability and insulation reliability. The solder particles according to this embodiment are manufactured by the above-mentioned manufacturing method.

The average particle size of the solder particles is not particularly limited as long as it is within the above range, and may be, for example, 30 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 3 μm or less, or 2 μm or less, preferably less than 1 μm. The average particle size of the solder particles may be, for example, 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or 500 nm or more.

The average particle size of the solder particles can be measured using various methods according to the size. For example, a dynamic light scattering method, a laser diffraction method, a centrifugal sedimentation method, an electrical detection band method, a resonance type mass measurement method, or the like can be used. Further, a method of measuring the particle size from an image obtained by an optical microscope, an electron microscope, or the like can be used. Specific devices include a flow-type particle image analyzer, a microtrack, a Coulter counter, and the like.

C. of solder particles V. The value is preferably 20% or less, more preferably 10% or less, still more preferably 7% or less, and particularly preferably 5% or less, from the viewpoint of achieving more excellent conductivity reliability and insulation reliability. In addition, C.I. V. The lower limit of the value is not particularly limited. For example, C.I. V. The value may be 1% or more, and may be 2% or more.

C. of solder particles V. The value is calculated by multiplying the value obtained by dividing the standard deviation of the particle size measured by the above method by the average particle size by 100.

A flat surface portion may be formed on a part of the surface of the solder particles, and at this time, the surface other than the flat surface portion is preferably spherical crown-shaped. That is, the solder particles may have a flat surface portion and a spherical crown-shaped curved surface portion. The ratio (A / B) of the diameter A of the flat surface portion to the diameter B of the solder particles may be, for example, more than 0.01 and less than 1.0 (0.01 <A / B <1.0), and may be 0.1. It may be ~ 0.9. Since the solder particles have a flat surface portion, the seating of the solder particles is improved and the handleability is improved. Specifically, when arranging solder particles on an object to be connected by solder particles such as electrodes, it is easy to arrange them in a predetermined position because there is a flat part, and it is soldered by vibration, wind, external force, static electricity, etc. It has the effect of suppressing the movement of particles from a predetermined position. Further, when the member on which the solder particles are arranged is tilted, there is an effect that the solder particles are hard to move due to gravity as compared with, for example, spherical solder particles having no flat portion.

In the above-mentioned manufacturing method, solder particles are formed on the convex portion of the substrate. At this time, the flat surface portion may be formed at the contact surface between the solder particles and the top portion of the convex portion.

When a quadrangle circumscribing the projected image of solder particles is created by two pairs of parallel lines, and the distance between the opposing sides is X and Y (where Y <X), the ratio of Y to X (Y / X) may be more than 0.8 and less than 1.0 (0.8 <Y / X <1.0), and may be 0.9 or more and less than 1.0. Such solder particles can be said to be particles closer to a true sphere. According to the manufacturing method of the present embodiment described above, such solder particles can be easily obtained.
Since the solder particles are close to a true sphere, for example, when a plurality of opposing electrodes are electrically connected via the solder particles, the contact between the solder particles and the electrodes is less likely to be uneven, and a stable connection can be obtained. Tend. Further, when a conductive film or resin in which solder particles are dispersed in a resin material is produced, high dispersibility is obtained, and dispersion stability during production tends to be obtained. Furthermore, when a film or paste in which solder particles are dispersed in a resin material is used for connection between electrodes, even if the solder particles rotate in the resin, if the solder particles have a spherical shape, when viewed in a projected image, The projected areas of the solder particles are close to each other. Therefore, when connecting the electrodes, it tends to be easy to obtain a stable electrical connection with little variation.

FIG. 8 is a diagram showing distances X and Y (where Y <X) between opposite sides when a quadrangle circumscribing a projected image of solder particles is created by two pairs of parallel lines. For example, an arbitrary particle is observed with a scanning electron microscope to obtain a projected image. Two pairs of parallel lines are drawn with respect to the obtained projected image, and the pair of parallel lines are arranged at the position where the distance between the parallel lines is the minimum, and the other pair of parallel lines are arranged at the position where the distance between the parallel lines is the maximum. , Find the Y / X of the particle. This operation is performed on 300 solder particles, the average value is calculated, and the Y / X of the solder particles is obtained.

The solder particles may contain tin or a tin alloy. As the tin alloy, for example, In—Sn alloy, In—Sn—Ag alloy, Sn—Au alloy, Sn—Bi alloy, Sn—Bi—Ag alloy, Sn—Ag—Cu alloy, Sn—Cu alloy and the like are used. be able to. Specific examples of these tin alloys include the following examples.
-In-Sn (In 52% by mass, Bi48% by mass, melting point 118 ° C)
-In-Sn-Ag (In 20% by mass, Sn77.2% by mass, Ag 2.8% by mass, melting point 175 ° C.)
-Sn-Bi (Sn43% by mass, Bi57% by mass, melting point 138 ° C.)
-Sn-Bi-Ag (Sn42% by mass, Bi57% by mass, Ag1% by mass, melting point 139 ° C.)-Sn-Ag-Cu (Sn96.5% by mass, Ag3% by mass, Cu0.5% by mass, melting point 217 ° C.)
-Sn-Cu (Sn99.3% by mass, Cu0.7% by mass, melting point 227 ° C)
-Sn-Au (Sn21.0% by mass, Au79.0% by mass, melting point 278 ° C.)

The solder particles may contain indium or an indium alloy. As the indium alloy, for example, an In—Bi alloy, an In—Ag alloy, or the like can be used. Specific examples of these indium alloys include the following examples.
-In-Bi (In66.3% by mass, Bi33.7% by mass, melting point 72 ° C.)
-In-Bi (In33.0% by mass, Bi67.0% by mass, melting point 109 ° C)
-In-Ag (In97.0% by mass, Ag3.0% by mass, melting point 145 ° C)

The above tin alloy or indium alloy can be selected according to the application (temperature at the time of use) of the solder particles. For example, when solder particles are used for fusion at a low temperature, an In—Sn alloy or a Sn—Bi alloy may be used, and in this case, the solder particles can be fused at 150 ° C. or lower. When a material having a high melting point such as Sn—Ag—Cu alloy or Sn—Cu alloy is used, high reliability can be maintained even after being left at a high temperature.

The solder particles may contain one or more selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P and B. Among these elements, Ag or Cu may be contained from the following viewpoints. That is, when the solder particles contain Ag or Cu, the melting point of the solder particles can be lowered to about 220 ° C., and the bonding strength with the electrode is further improved, so that better conduction reliability can be obtained. It will be easier.

The Cu content of the solder particles is, for example, 0.05 to 10% by mass, and may be 0.1 to 5% by mass or 0.2 to 3% by mass. When the Cu content is 0.05% by mass or more, it becomes easy to achieve better solder connection reliability. Further, when the Cu content is 10% by mass or less, the melting point is low and the solder particles tend to have excellent wettability, and as a result, the connection reliability of the joint portion by the solder particles tends to be good.

The Ag content of the solder particles is, for example, 0.05 to 10% by mass, and may be 0.1 to 5% by mass or 0.2 to 3% by mass. When the Ag content is 0.05% by mass or more, it becomes easy to achieve better solder connection reliability. Further, when the Ag content is 10% by mass or less, the melting point is low and the solder particles tend to have excellent wettability, and as a result, the connection reliability of the joint portion by the solder particles tends to be good.

The use of the solder particles is not particularly limited, and for example, it can be suitably used as conductive particles for an anisotropic conductive material. In addition, applications such as ball grid array connection method (BGA connection), which is widely used for mounting semiconductor integrated circuits, are used to electrically connect electrodes, and parts such as MEMS are sealed, sealed, brazed, and high. It can also be suitably used for applications such as a spacer for controlling a sheath gap. That is, the solder particles can be used for general applications in which conventional solder is used.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Example 1>
(Step a1) Preparation of a substrate A substrate (polyimide film, thickness 50 μm) having a plurality of convex portions having a top diameter of 0.15 μmφ, a bottom diameter of 0.15 μmφ, and a height of 0.13 μm was prepared. The plurality of protrusions were regularly arranged at intervals of 0.15 μm.

(Step b1) Formation of Solder Layer The substrate having a plurality of convex portions obtained in the step a1 was put into a sputtering apparatus (manufactured by Arios Co., Ltd.), and after evacuation, argon gas was added to make the inside of the apparatus an argon atmosphere of 1 Pa. .. Then, sputtering was carried out under the following conditions for the time shown in Table 1 to form a solder layer.
(Device conditions)
Target: Sn-Bi solder plate (melting point 139 ° C)
Input power ・・・・・・・・・・・ 60W

(Step c1) Formation of solder particles The substrate having the solder layer obtained in step b1 is put into a formic acid radical reduction furnace (reflow equipment manufactured by Shinko Seiki Co., Ltd.), vacuumed, and then formic acid mixed nitrogen gas (formic acid content 4). %) Was introduced into the furnace to fill the inside of the furnace. Then, the inside of the furnace was adjusted to 120 ° C., and the reduction treatment was carried out for 5 minutes. Then, after heating to 180 ° C., the gas in the furnace is removed by vacuuming, nitrogen is introduced into the furnace to return it to atmospheric pressure, and then the temperature inside the furnace is lowered to room temperature to form solder particles. bottom.

(Evaluation of solder particles)
The substrate having the solder particles obtained in step c1 was fixed on the conductive tape fixed to the surface of the SEM observation pedestal. Then, platinum sputtering was carried out under the conditions of 20 mA and 60 seconds. The diameter of 200 core-shell type solder particles was measured by SEM, and the average particle diameter and C.I. V. The value was calculated. The results are shown in Table 1.

<Examples 2 to 12>
Solder particles were prepared and evaluated in the same manner as in Example 1 with the top diameter, bottom diameter, height, interval, sputtering time and material shown in Table 1. The results are shown in Table 1. Further, FIG. 12 shows an SEM image of the solder particles obtained in Example 2.

<Examples 13 to 17>
Solder particles were produced in the same manner as in Example 1 with the top diameter, bottom diameter, height, spacing, sputtering time and material shown in Table 1, except that the following step c2 was performed instead of step c1. And evaluated. The results are shown in Table 1. The SEM image of the substrate prepared in Example 13 is shown in FIG. 9, the SEM image of the solder layer formed on the substrate is shown in FIG. 10, and the SEM image of the solder particles formed is shown in FIG.

(Step c2) Formation of solder particles The substrate having the solder layer obtained in step b1 is put into a hydrogen radical reduction furnace (plasma reflow device manufactured by Shinko Seiki Co., Ltd.), vacuumed, and then hydrogen gas is introduced into the furnace. The inside of the furnace was filled with hydrogen gas. Then, the inside of the furnace was adjusted to 130 ° C. and irradiated with hydrogen radicals for 5 minutes. After that, the hydrogen gas in the furnace is removed by vacuuming, and after heating to 165 ° C., nitrogen is introduced into the furnace to return it to atmospheric pressure, and then the temperature inside the furnace is lowered to room temperature to remove the solder particles. Formed.

<Comparative example 1>
500 g of Sn-Bi solder fine particles (manufactured by 5N Plus, melting point 139 ° C., Type 8, D ₅₀ = 3.0 μm, CV value 42%) were separated into 5 parts of 100 g each and each of them was added to distilled water. After immersion and ultrasonic dispersion, the mixture was allowed to stand and the solder fine particles floating in the supernatant were recovered. By repeating this operation, a total of 1 g of solder fine particles was collected. The average particle size of the obtained solder fine particles and C.I. V. The values are shown in Table 1.

<Comparative example 2>
Solder particles were prepared and evaluated in the same manner as in Example 2 except that a smooth substrate (polyimide film, thickness 50 μm) having no convex portion was prepared. The results are shown in Table 1. An SEM image of the obtained solder particles is shown in FIG.

1 ... Solder particles, 10 ... Base, 11,21 ... Convex, 12, 22 ... Bottom, 50 ... Solder layer, 100, 110 ... Base with solder particles.

Claims

A preparatory step for preparing a substrate having a plurality of protrusions, and
A solder layer forming step of forming a solder layer on at least a part of the convex portion of the substrate, and
A fusion step of fusing the solder layer formed on the convex portion to form solder particles on the convex portion, and a fusion step.
A method for manufacturing solder particles, including.
The method for producing solder particles according to claim 1, wherein the convex portion has a columnar shape or a frustum shape.
The substrate has a first surface comprising a plurality of protrusions and a bottom formed between the protrusions.
The method for producing solder particles according to claim 1 or 2, wherein the ratio of the projected area of the bottom portion to the projected area of the first surface is 8% or more.
Any one of claims 1 to 3, wherein in the solder layer forming step, the solder layer is formed on the convex portion by at least one method selected from the group consisting of plating, vapor deposition, sputtering and spray coating. The method for producing solder particles according to.
The method for producing solder particles according to any one of claims 1 to 4, further comprising a reduction step of exposing the solder layer formed on the convex portion to a reducing atmosphere before the fusion step.
The method for producing solder particles according to any one of claims 1 to 5, wherein in the fusion step, the solder layer formed on the convex portion is fused in a reducing atmosphere.
The method for producing solder particles according to any one of claims 1 to 6, wherein the solder layer contains at least one selected from the group consisting of tin, tin alloys, indium and indium alloys.
The solder layer is an In-Bi alloy, an In-Sn alloy, an In-Sn-Ag alloy, a Sn-Au alloy, a Sn-Bi alloy, a Sn-Bi-Ag alloy, a Sn-Ag-Cu alloy and a Sn-Cu alloy. The method for producing solder particles according to claim 7, which comprises at least one selected from the group consisting of.
The average particle size is 100 nm or more and less than 1 μm, and C.I. V. Solder particles with a value of 20% or less.
When a quadrangle circumscribing the projected image of solder particles is created by two pairs of parallel lines, and the distance between the opposing sides is X and Y (where Y <X), X and Y satisfy the following equation. , The solder particles according to claim 9.
0.8 <Y / X <1.0
The solder particles according to claim 9 or 10, which include at least one selected from the group consisting of tin, tin alloys, indium and indium alloys.
Select from the group consisting of In-Bi alloys, In-Sn alloys, In-Sn-Ag alloys, Sn-Au alloys, Sn-Bi alloys, Sn-Bi-Ag alloys, Sn-Ag-Cu alloys and Sn-Cu alloys. The solder particles according to any one of claims 9 to 11, which comprises at least one of the alloys.
A substrate with solder particles, comprising a substrate having a plurality of convex portions and a plurality of solder particles arranged on the convex portions of the substrate.
The average particle size of the solder particles is 100 nm or more and less than 1 μm, and the C.I. V. The substrate with solder particles according to claim 13, wherein the value is 20% or less.