Method for manufacturing a connection structure

Abstract

Provided is a manufacturing method for a connection structure by which it is possible to favorably dispose a conductive paste on two electrodes adjacent to each other by using one opening of a metal mask, and by which it is possible to increase uniformity in the amount of solder accumulated on each electrode.　This manufacturing method for a connection structure comprises: a first disposal step, in which, by using the metal mask, a conductive paste is disposed on a surface of a first connection member having, on the surface thereof, a plurality of first electrodes. The metal mask has an opening with a length direction and a width direction. The opening has a specific aperture section, a specific first wide section, and a specific second wide section. A minimum opening width B of the aperture section divided by a maximum opening width A of the opening is 0.3 to 0.7, inclusive. In the first disposal step, the metal mask is disposed such that, from among the adjacent first electrodes, one of the first electrodes opposes the first wide section and the other first electrode opposes the second wide section.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a connection structure using a conductive paste containing solder particles. [Background technology]

[0002] A method using a metal mask is known as a method for disposing a conductive paste containing solder particles on an electrode, in which the conductive paste is disposed on the electrode through openings in the metal mask.

[0003] Patent Document 1 below discloses a bonding method for bonding two electrodes by applying solder to at least one of the bonding surfaces of two electrodes through an opening in a metal mask, overlapping the bonding surfaces, and heating the solder between the bonding surfaces to melt it and then solidifying the solder. One of the two electrodes is located on the bonding side of an electronic component, and the other is located on the bonding side of a circuit board. The shape of the opening in the metal mask is outlined by a straight line portion parallel to the Y-axis direction and curved lines tapering from both ends of the straight line portion toward the X-axis, forming a hand drum shape with two bowl-shaped shapes arranged line-symmetrically about the Y-axis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-205756 Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, in a conventional method of applying a conductive paste using a metal mask, the conductive paste is applied to one electrode through one opening in the metal mask. Furthermore, in the conventional method, the conductive paste needs to be applied only to the electrode portion.

[0006] The object of the present invention is to provide a method for manufacturing a connection structure that enables conductive paste to be well placed on two adjacent electrodes through one opening in a metal mask, and that increases the uniformity of the amount of solder that accumulates on each electrode. [Means for solving the problem]

[0007] According to a broad aspect of the present invention, there is provided a method for manufacturing a substrate, comprising: a first arranging step of arranging, using a metal mask, a conductive paste containing a plurality of solder particles on the surface of a first connection target component having a plurality of first electrodes on its surface; a second arranging step of arranging a second connection target component having a plurality of second electrodes on its surface on the surface of the conductive paste opposite the first connection target component side, so that the first electrodes and the second electrodes face each other; and a connecting step of forming a connection portion connecting the first connection target component and the second connection target component using the conductive paste by heating the conductive paste to a temperature equal to or higher than the melting point of the solder particles, and electrically connecting the first electrodes and the second electrodes by a solder portion in the connection portion, wherein the metal mask is A method for manufacturing a connection structure is provided, which has an opening having a length direction and a width direction, the opening having a narrowed portion with a small opening width in a central portion in the length direction, a first wide portion connected to one side of the narrowed portion in the length direction and having a larger opening width than the narrowed portion, and a second wide portion connected to the other side of the narrowed portion in the length direction and having a larger opening width than the narrowed portion, wherein when the maximum opening width of the opening is A and the minimum opening width of the narrowed portion is B, B / A is 0.3 or more and 0.7 or less, and in the first arrangement step, the metal mask is arranged so that one of the adjacent first electrodes faces the first wide portion and the other first electrode faces the second wide portion.

[0008] In a specific aspect of the manufacturing method of the connection structure according to the present invention, the contours of both ends of the opening in the length direction include curved lines.

[0009] In a particular aspect of the manufacturing method of the connection structure according to the present invention, the first connection target member has a convex partition portion on the surface on the first electrode side where the first electrode is not present, and in the first placement step, the metal mask is placed so that at least a portion of the partition portion faces the narrowed portion.

[0010] In a specific aspect of the manufacturing method of the connection structure according to the present invention, the contour of the drawn portion includes a curve.

[0011] In a specific aspect of the manufacturing method of the connection structure according to the present invention, the contour of the drawn portion includes a straight line. [Effects of the Invention]

[0012] The method for manufacturing a connection structure according to the present invention allows for good placement of conductive paste on two adjacent electrodes through one opening in the metal mask, and also increases the uniformity of the amount of solder that agglomerates on each electrode. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view schematically showing a first example of a metal mask used in the present invention. [Figure 2] FIG. 2 is a plan view schematically showing a second example of the metal mask used in the present invention. [Figure 3] Figure 3(a) is a plan view for explaining the first placement step of the method for manufacturing a connection structure according to the first embodiment of the present invention, and Figure 3(b) is a cross-sectional view for explaining the first placement step of the method for manufacturing a connection structure according to the first embodiment of the present invention. [Figure 4] Figure 4(c) is a cross-sectional view for explaining the second placement step of the method for manufacturing a connection structure according to the first embodiment of the present invention, and Figure 4(d) is a cross-sectional view of a connection structure obtained by the method for manufacturing a connection structure according to the first embodiment of the present invention. [Figure 5]FIG. 5 is a cross-sectional view illustrating a first arrangement step in a method for manufacturing a connection structure according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a plan view schematically showing the metal mask used in Comparative Example 2. As shown in FIG. [Figure 7] FIG. 7 is a plan view schematically showing the metal mask used in Comparative Example 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below.

[0015] (Method of manufacturing connection structure) A method for manufacturing a connection structure according to the present invention includes a first arrangement step of arranging, using a metal mask, a conductive paste containing a plurality of solder particles on the surface of a first connection-target member having a plurality of first electrodes on its surface.A method for manufacturing a connection structure according to the present invention includes a second arrangement step of arranging, on the surface of the conductive paste opposite the first connection-target member side, a second connection-target member having a plurality of second electrodes on its surface, so that the first electrodes and the second electrodes face each other.A method for manufacturing a connection structure according to the present invention includes a connecting step of forming a connection portion connecting the first connection-target member and the second connection-target member using the conductive paste by heating the conductive paste to a temperature equal to or higher than the melting point of the solder particles, and electrically connecting the first electrodes and the second electrodes with a solder portion in the connection portion.

[0016] In the method for manufacturing a connection structure according to the present invention, the metal mask has the following openings X.

[0017] The opening X is an opening that satisfies all of the following (1) to (3).

[0018] (1) It has a length direction and a width direction.

[0019] (2) It has a narrowed section with a small opening width in the central part in the longitudinal direction, a first wide section connected to one side of the narrowed section in the longitudinal direction and with a larger opening width than the narrowed section, and a second wide section connected to the other side of the narrowed section in the longitudinal direction and with a larger opening width than the narrowed section.

[0020] (3) When the maximum opening width of the opening is A and the minimum opening width of the throttle portion is B, B / A is 0.3 or more and 0.7 or less.

[0021] In the method for manufacturing a connection structure according to the present invention, in the first arrangement step, the metal mask is arranged so that one of the adjacent first electrodes faces the first wide portion and the other first electrode faces the second wide portion.

[0022] The method for manufacturing a connection structure according to the present invention has the above-described configuration, which allows for good placement of conductive paste on two adjacent electrodes simultaneously through one opening in the metal mask, and improves the uniformity of the amount of solder condensed on each electrode. In other words, the method for manufacturing a connection structure according to the present invention has the above-described configuration, which improves both printability and the uniformity of the amount of solder condensed on each electrode. As a result, the electrical conductivity reliability of each of the multiple electrodes of the resulting connection structure can be improved, and poor connection can be prevented.

[0023] In conventional conductive paste placement methods using metal masks, the conductive paste is placed on one electrode through one opening in the metal mask. Furthermore, with conventional methods, the conductive paste must be placed only on the electrode. In recent years, the diameter of metal mask openings has become smaller as electronic components have become smaller. However, if the opening area of ​​the metal mask is small, the conductive paste cannot be properly placed on the electrode through the opening, which can result in poor printability.

[0024] The inventors have found that, for example, when a metal mask having rectangular openings is used to place conductive paste on two adjacent electrodes through one rectangular opening so as not to make the opening area excessively small, uneven amounts of solder tend to accumulate on each electrode.

[0025] To address these issues, the inventors discovered that by using a metal mask having openings X, it is possible to effectively place conductive paste on two adjacent electrodes simultaneously using one opening in the metal mask, and to increase the uniformity of the amount of solder that agglomerates on each electrode.

[0026] In the present invention, when the electrodes are electrically connected, multiple solder particles tend to gather between the upper and lower opposing electrodes, allowing multiple solder particles to be arranged on the electrodes (lines). Furthermore, some of the multiple solder particles are less likely to be arranged between horizontal electrodes that should not be connected, significantly reducing the amount of solder particles arranged between horizontal electrodes that should not be connected. As a result, the present invention can effectively improve the reliability of conductivity between the upper and lower electrodes that should be connected, and can effectively improve the reliability of insulation between adjacent horizontal electrodes that should not be connected.

[0027] (metal mask) The metal mask has an opening X that satisfies all of the above (1) to (3). The metal mask may have only one opening X, or may have two or more openings X. The metal mask may have three or more openings X, five or more openings X, or ten or more openings X. When the metal mask has multiple openings X, the shapes of the multiple openings X may be the same or different. Furthermore, the metal mask may have openings other than the opening X.

[0028] Fig. 1 is a plan view schematically showing a first example of a metal mask used in the present invention. Fig. 1 shows an enlarged view of the periphery of one opening X. Note that in Fig. 1 and in the figures described below, the dimensions have been appropriately changed from the actual dimensions for the sake of convenience.

[0029] The metal mask 10 shown in FIG. 1 has an opening X having a length direction L and a width direction W. In FIG. 1, the left-right direction is the length direction L of the opening X, and the up-down direction is the width direction W of the opening X. The length direction L and the width direction W are directions perpendicular to each other. The length direction L is greater than the width direction W.

[0030] The metal mask 10 has an opening X having a first wide portion 11, a narrowed portion 13, and a second wide portion 12. The opening X is composed of the first wide portion 11, the narrowed portion 13, and the second wide portion 12. The narrowed portion 13 is a portion with a smaller opening width located in the center of the opening X in the longitudinal direction L. The narrowed portion 13 is a portion with a smaller opening width than the first wide portion 11 and the second wide portion 12. The first wide portion 11 is connected to one side of the narrowed portion 13 in the longitudinal direction L and has a larger opening width than the narrowed portion 13. The second wide portion 12 is connected to the other side of the narrowed portion 13 in the longitudinal direction L and has a larger opening width than the narrowed portion 13.

[0031] When the maximum opening width of the opening X is A and the minimum opening width of the diaphragm portion 13 is B, B / A is 0.3 or more and 0.7 or less. The maximum opening width A exists in at least one of the first wide portion and the second wide portion. The opening width of at least one of the first wide portion and the second wide portion is the maximum opening width A of the opening X. When the opening widths of the first wide portion and the second wide portion are the same, the opening widths of both the first wide portion and the second wide portion are the maximum opening width A of the opening X.

[0032] The contours of both ends of the opening X in the length direction L are curved. The first wide portion 11 and the second wide portion 12 are each formed by a curve. The contour of the narrowed portion 13 is also curved. The opening X does not have any parts formed by straight lines. The shape of the opening X when viewed in a plane is what is called a gourd shape.

[0033] 2 is a plan view schematically showing a second example of a metal mask used in the present invention, in which the periphery of one opening X is shown in an enlarged manner.

[0034] The metal mask 10A shown in FIG. 2 has an opening X having a length direction L and a width direction W. In FIG. 2, the left-right direction is the length direction L of the opening X, and the up-down direction is the width direction W of the opening X. The length direction L and the width direction W are directions perpendicular to each other. The length direction L is greater than the width direction W.

[0035] The metal mask 10A has an opening X having a first wide portion 11A, a narrowed portion 13A, and a second wide portion 12A. The opening X is formed by the first wide portion 11A, the narrowed portion 13A, and the second wide portion 12A. The narrowed portion 13A is a portion having a smaller opening width located in the center of the opening X in the longitudinal direction L. The narrowed portion 13A is a portion having a smaller opening width than the first wide portion 11A and the second wide portion 12A. The first wide portion 11A is connected to one side of the narrowed portion 13A in the longitudinal direction L and has a larger opening width than the narrowed portion 13A. The second wide portion 12A is connected to the other side of the narrowed portion 13A in the longitudinal direction L and has a larger opening width than the narrowed portion 13A.

[0036] When the maximum opening width of opening X is A and the minimum opening width of throttle portion 13A is B, B / A is 0.3 or more and 0.7 or less. Maximum opening width A exists in at least one of first wide portion 11A and second wide portion 12A.

[0037] The contours of both ends of the opening X in the length direction L are curved. The first wide portion 11A and the second wide portion 12A are each formed by a curve. The contours of the narrowed portion 13A are straight. The opening X has a portion formed by a curve and a portion formed by a straight line. The shape of the opening X when viewed in a plane is what is called a dumbbell shape.

[0038] In the present invention, the contours of both ends of the opening X in the longitudinal direction may include curves or may include straight lines. In the present invention, the contours of both ends of the opening X in the longitudinal direction may be curves or may include straight lines. An opening X whose both ends in the longitudinal direction are straight lines may have, for example, a hand-held hourglass shape when viewed from above, but is not limited to this. From the viewpoint of properly disposing the conductive paste on the electrode, the contours of both ends of the opening X in the longitudinal direction preferably include curves, and are preferably curved. From the viewpoint of properly disposing the conductive paste on the electrode, the contours of the first wide portion and the second wide portion each preferably include curves, and are preferably curved. Note that when both ends of the opening X in the longitudinal direction are dot-shaped, if the dot-shaped portion and a portion connected to it are curved (i.e., if the dot-shaped portion forms part of a curve), the contours of both ends of the opening X in the longitudinal direction are considered to be curved.

[0039] The contour of the drawn portion may include a curve, may include a straight line, or may include a curve and a straight line. The contour of the drawn portion may be curved, may be straight, or may be composed of a curve and a straight line. From the viewpoint of properly disposing the conductive paste on the electrode, the contour of the drawn portion preferably includes a curve, and is preferably a curve. From the viewpoint of easily producing a metal mask having openings X, the contour of the drawn portion preferably includes a straight line, and is preferably a straight line.

[0040] From the viewpoint of properly disposing the conductive paste on the electrode, it is preferable that the number of the narrowed portions in the opening X is one. From the viewpoint of properly disposing the conductive paste on the electrode, it is preferable that the number of narrowed portions connected to the first wide portion and the second wide portion in the opening X is one. From the viewpoint of properly disposing the conductive paste on the electrode, it is preferable that the number of narrowed portions connected to the first wide portion and the second wide portion in the opening X is one.

[0041] When the contour length of the opening X is taken as 100%, the proportion of the contour length that is made up of curves is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. In this case, the conductive paste can be more effectively disposed on the electrode. Note that when the contour length of the opening X is taken as 100%, the proportion of the contour length that is made up of curves may be 100%, less than 100%, or 95% or less.

[0042] When the length of the contour of the opening X is taken as 100%, the proportion of the length of the contour that is made up of straight lines is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. In this case, the conductive paste can be more effectively disposed on the electrode. Note that when the length of the contour of the opening X is taken as 100%, the proportion of the length of the contour that is made up of straight lines may be 0%, may exceed 0%, or may be 5% or more.

[0043] In a metal mask in which the contours of both ends of the opening X in the longitudinal direction include or are curved, when the total length of the contours of the first wide portion and the second wide portion is taken as 100%, the proportion of the contour length that is made up of curves is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. In this case, the conductive paste can be more effectively disposed on the electrode. When the total length of the contours of the first wide portion and the second wide portion is taken as 100%, the proportion of the contour length that is made up of curves may be 100%, less than 100%, or 95% or less.

[0044] Furthermore, when the total length of the contours of the first wide portion and the second wide portion is taken as 100%, the proportion of the length of the contours made up of straight lines is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. In this case, the conductive paste can be more effectively disposed on the electrode. When the total length of the contours of the first wide portion and the second wide portion is taken as 100%, the proportion of the length of the contours made up of straight lines may be 0%, more than 0%, or 5% or more.

[0045] In a metal mask in which the contour of the drawn portion includes or is a curve, when the total contour length of the drawn portion is taken as 100%, the proportion of the contour length that is made up of curves is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. In this case, the conductive paste can be more effectively disposed on the electrode. When the total contour length of the first wide portion and the second wide portion is taken as 100%, the proportion of the contour length that is made up of straight lines may be 100%, less than 100%, or 95% or less.

[0046] Furthermore, when the total length of the contours of the narrowed portion is taken as 100%, the proportion of the length of the contours made up of straight lines is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. In this case, the conductive paste can be more effectively disposed on the electrode. When the total length of the contours of the first wide portion and the second wide portion is taken as 100%, the proportion of the length of the contours made up of straight lines may be 0%, more than 0%, or 5% or more.

[0047] From the viewpoint of easily producing a metal mask having an opening X, in a metal mask in which the contour of the drawn portion includes or is a straight line, when the total length of the contour of the drawn portion is taken as 100%, the proportion of the length of the contour that is made up of straight lines may exceed 0%, may be 5% or more, may be 50% or more, or may be 100% or less.

[0048] The opening X may or may not be line-symmetric at the center position in the length direction, with a straight line parallel to the width direction as the axis of symmetry.The opening X may or may not be line-symmetric at the center position in the length direction, with a straight line parallel to the length direction as the axis of symmetry.

[0049] To achieve the effects of the present invention, the ratio (B / A) of the minimum opening width (B) of the constriction portion to the maximum opening width (A) of the opening X is 0.3 or more and 0.7 or less. If the ratio (B / A) is less than 0.3, the size of the opening becomes too small, resulting in increased variation in the placement of the conductive paste, which can lead to poor printability. If the ratio (B / A) exceeds 0.7, the uniformity of the amount of solder condensed on each electrode tends to decrease when the amount of solder placed between the opposing electrodes increases. The ratio (B / A) is preferably 0.35 or more, more preferably 0.4 or more, and preferably 0.5 or less, more preferably 0.45 or less. If the ratio (B / A) is equal to or greater than the lower limit and equal to or less than the upper limit, the effects of the present invention can be more effectively achieved. In particular, if the ratio (B / A) is equal to or greater than the lower limit, printability can be further improved, and if the ratio (B / A) is equal to or less than the upper limit, the uniformity of the amount of solder condensed on each electrode can be further improved.

[0050] The opening width of the opening X can be set, for example, in relation to the vertical length of the first electrode. In the first arrangement step, one of the adjacent first electrodes faces the first wide portion 11A of the opening X, and the other first electrode faces the second wide portion 12A of the opening X.

[0051] The maximum opening width (A) of the opening X is preferably 1.0 times or more, more preferably 1.02 times or more, and preferably 1.1 times or less, more preferably 1.08 times or less, the vertical length of the first electrode.

[0052] The minimum opening width (B) of the restrictor is preferably 0.45 times or more, more preferably 0.47 times or more, and preferably 0.65 times or less, more preferably 0.48 times or less, the vertical length of the first electrode.

[0053] The opening length of the opening X is preferably 1.13 times or more, more preferably 1.15 times or more, and preferably 1.19 times or less, more preferably 1.18 times or less, the total length of the adjacent first electrodes in the left-right direction.

[0054] The opening area of ​​the opening X is preferably 0.95 times or more, more preferably 0.97 times or more, and preferably 1.04 times or less, more preferably 1.02 times or less, the total area of ​​the adjacent first electrodes. When the opening area is equal to or greater than the lower limit and equal to or less than the upper limit, the effects of the present invention can be more effectively exhibited.

[0055] When opening X is divided into openings X1 and X2 at the center in the longitudinal direction with a straight line parallel to the width direction as the axis of symmetry, it is preferable that the difference between the opening area of ​​opening X1 on one side and the opening area of ​​opening X2 on the other side is small. It is preferable that the opening area of ​​opening X1 on one side and the opening area of ​​opening X2 on the other side are the same, or that the larger opening area of ​​opening X1 on one side and the opening area of ​​opening X2 on the other side is 1.3 times or less (more preferably 1.2 times or less, and even more preferably 1.1 times or less) the smaller opening area.

[0056] The metal mask preferably has a plurality of openings X. In this case, the conductive paste can be placed on more electrodes, for example, on four or more electrodes.

[0057] Fig. 6 is a plan view schematically showing the metal mask used in Comparative Example 2. Fig. 6 shows an enlarged view of the periphery of one opening (sometimes referred to as opening Y).

[0058] The metal mask 100 shown in FIG. 6 has an opening Y having a length direction L and a width direction W. In FIG. 6, the left-right direction is the length direction L of the opening Y, and the up-down direction is the width direction W of the opening Y. The length direction L and the width direction W are directions perpendicular to each other. The length direction L is greater than the width direction W.

[0059] The metal mask 100 has an opening Y having a first wide portion 101, a narrowed portion 103, and a second wide portion 102. The opening Y is composed of the first wide portion 101, the narrowed portion 103, and the second wide portion 102. The narrowed portion 103 is a portion with a narrow opening width located in the center of the opening Y in the longitudinal direction L. The narrowed portion 103 is a portion with a narrower opening width than the first wide portion 101 and the second wide portion 102. The first wide portion 101 is connected to one side of the narrowed portion 103 in the longitudinal direction L and has a wider opening width than the narrowed portion 103. The second wide portion 102 is connected to the other side of the narrowed portion 103 in the longitudinal direction L and has a wider opening width than the narrowed portion 103.

[0060] When the maximum opening width of the opening Y is A and the minimum opening width of the restrictor 103 is B, B / A is 0.75. The maximum opening width A exists in at least one of the first wide portion 101 and the second wide portion 102.

[0061] The contours of both ends of the opening Y in the length direction L are curved. The first wide portion 101 and the second wide portion 102 are each formed by a curve. The contour of the narrowed portion 103 is a straight line. The opening Y has a portion formed by a curve and a portion formed by a straight line. The shape of the opening Y when viewed in a plane is what is called a dumbbell shape.

[0062] With the metal mask 100, the ratio (B / A) exceeds 0.7, so when the electrodes are electrically connected, some of the multiple solder particles are likely to be disposed between the horizontal electrodes that should not be connected, and the amount of solder particles disposed between the horizontal electrodes that should not be connected increases. As a result, when the metal mask 100 is used, the reliability of the conductivity between the upper and lower electrodes that should be connected and the reliability of the insulation between the adjacent horizontal electrodes that should not be connected decrease.

[0063] Fig. 7 is a plan view schematically showing the metal mask used in Comparative Example 1. Fig. 7 shows an enlarged view of the periphery of one opening (sometimes referred to as opening Y).

[0064] The metal mask 100A shown in FIG. 7 has an opening Y having a length direction L and a width direction W. In FIG. 7, the left-right direction is the length direction L of the opening Y, and the up-down direction is the width direction W of the opening Y. The length direction L and the width direction W are directions perpendicular to each other. The length direction L is greater than the width direction W.

[0065] The ratio (B / A) is different between the metal mask 10 shown in Fig. 1 and the metal mask 100A shown in Fig. 7. That is, in the metal mask 100A shown in Fig. 7, when the maximum opening width of the opening Y is A and the minimum opening width of the narrowed portion 103 is B, B / A is 0.24. The maximum opening width A exists in at least one of the first wide portion 101A and the second wide portion 102A.

[0066] With the metal mask 100A, the ratio (B / A) is less than 0.3, which leads to large variations in the placement of the conductive paste and tends to reduce printability. That is, with the metal mask 100A, it is not possible to properly place the conductive paste on two adjacent electrodes at the same time using one opening Y.

[0067] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0068] (First placement process) Fig. 3(a) is a plan view illustrating a first arrangement step in the method for manufacturing a connection structure according to the first embodiment of the present invention, and Fig. 3(b) is a cross-sectional view illustrating the first arrangement step in the method for manufacturing a connection structure according to the first embodiment of the present invention. Fig. 3(b) is a cross-sectional view taken along line II in Fig. 3(a). In Fig. 3, the metal mask 10 shown in Fig. 1 is used.

[0069] In the first arrangement step, a conductive paste 3 is arranged on the surface (upper surface) of a first connection target member 1 having a plurality of first electrodes 1a on its surface (upper surface) using a metal mask 10. In this embodiment, the conductive paste 3 contains a plurality of solder particles 3A, a thermosetting component 3B, and flux. The thermosetting component 3B of the conductive paste 3 contains a thermosetting compound and a thermosetting agent.

[0070] Specifically, the conductive paste 3 is placed as follows.

[0071] A metal mask 10 is placed so that one of adjacent first electrodes 1a faces the first wide portion 11 of the opening X, and the other first electrode 1a faces the second wide portion 12 of the opening X. Next, a conductive paste 3 is applied from the upper surface of the metal mask 10, and the conductive paste 3 is placed on the surface of the first connection target member 1 through the opening X. After the conductive paste 3 is placed, solder particles 3A are placed on both one first electrode 1a and the other first electrode 1a.

[0072] FIG. 5 is a cross-sectional view illustrating a first arrangement step in a method for manufacturing a connection structure according to a second embodiment of the present invention.

[0073] The first arranging step shown in FIG. 3(b) and the first arranging step shown in FIG. 5 differ in the structure of the first connection target member.

[0074] 5, a first connection target member 1A is used, which has a convex partition portion 5 on the surface on the first electrode 1a side, in a portion where no first electrode 1a is present. The partition portion 5 is disposed between adjacent first electrodes 1a. The height of the partition portion 5 is greater than the height of the first electrodes 1a.

[0075] By using a first connection target member 1A having a partition portion 5, the uniformity of the amount of solder condensing on each electrode can be further improved compared to a first connection target member that does not have a partition portion 5 (for example, the first connection target member 1 shown in Figure 3(b)).

[0076] In the first arrangement step when using a first connection target member 1A having a partition portion 5, a metal mask 10 is arranged so that at least a part of the partition portion 5 faces the narrowed portion 13. Thereafter, the conductive paste 3 is arranged in the same manner as in the first embodiment. Note that the partition portion 5 may or may not face the first wide portion 11 of the opening X. Furthermore, the partition portion 5 may or may not face the second wide portion 12 of the opening X.

[0077] As described above, in the present invention, a first connection target member that does not have a convex partitioning portion may be used, or a first connection target member that has a convex partitioning portion may be used.

[0078] After the first disposing step, the metal mask is preferably removed.

[0079] (Second placement process) Fig. 4(c) is a cross-sectional view illustrating a second arrangement step in the method for manufacturing a connection structure according to the first embodiment of the present invention. Fig. 4(d) is a cross-sectional view of a connection structure obtained by the method for manufacturing a connection structure according to the first embodiment of the present invention. Note that Figs. 4(c) and 4(d) show the state when a first connection target member without a convex partition portion is used, but the same applies when a first connection target member with the above-mentioned partition portion is used.

[0080] A second member to be connected 2 having a second electrode 2a on its surface (lower surface) is prepared. In a second placement step, the second member to be connected 2 is placed on the surface of the conductive paste 3 opposite the first member to be connected 1 side. The second member to be connected 2 is placed on the surface of the conductive paste 3 from the second electrode 2a side. At this time, the first electrode 1a and the second electrode 2a are opposed to each other.

[0081] (Connection process) Next, the conductive paste 3 is heated to a temperature equal to or higher than the melting point of the solder particles 3A. Preferably, the conductive paste 3 is heated to a temperature equal to or higher than the curing temperature of the thermosetting component 3B (thermosetting compound). During this heating, the solder particles 3A present in the region where no electrodes are formed gather between the first electrode 1a and the second electrode 2a (self-aggregation effect). In the present invention, the solder particles 3A gather more effectively between the first electrode 1a and the second electrode 2a. The solder particles 3A also melt and bond together. The thermosetting component 3B also thermally hardens. As a result, as shown in FIG. 4(d), a connection portion 4 connecting the first connection target member 1 and the second connection target member 2 is formed by the conductive paste 3, and a connection structure 20 is obtained. The connection portion 4 is formed by the conductive paste 3, and the solder portion 4A is formed by bonding the multiple solder particles 3A, and the thermosetting component 3B is thermally hardened to form a hardened portion 4B. The first electrode 1a and the second electrode 2a are electrically connected by the solder portion 4A in the connection portion 4. If the solder particles 3A move sufficiently, it is not necessary to maintain a constant temperature from the start of the movement of the solder particles 3A that are not located between the first electrode 1a and the second electrode 2a until the movement of the solder particles 3A to between the first electrode 1a and the second electrode 2a is completed.

[0082] It is preferable that no pressure be applied in the second arranging step and the connecting step. In this case, the weight of the second connection target member 2 is added to the conductive paste 3. This allows the solder particles 3A to gather more effectively between the first electrode 1a and the second electrode 2a when the connection portion 4 is formed. If pressure is applied in at least one of the second arranging step and the connecting step, the action of the solder particles 3A to gather between the first electrode 1a and the second electrode 2a is more likely to be inhibited.

[0083] Furthermore, in this embodiment, since no pressure is applied, even if the first connection target member 1 and the second connection target member 2 are overlapped with a slight misalignment between the first electrode 1a and the second electrode 2a, the slight misalignment can be corrected to connect the first electrode 1a and the second electrode 2a (self-alignment effect). This is because the molten solder that self-aggregates between the first electrode 1a and the second electrode 2a is energetically stable when the contact area between the solder and other components of the conductive paste between the first electrode 1a and the second electrode 2a is minimized, and a force acts to create an aligned connection structure with this minimum contact area. At this time, it is desirable that the conductive paste is not hardened and that the viscosity of components other than the solder particles in the conductive paste is sufficiently low at that temperature and for that time.

[0084] The second arranging step and the connecting step may be performed consecutively. After the second arranging step, the resulting laminate of the first connection-target member 1, the conductive paste 3, and the second connection-target member 2 may be moved to a heating unit, and the connecting step may be performed. To perform the heating, the laminate may be placed on a heating member, or the laminate may be placed in a heated space.

[0085] The heating temperature in the above-mentioned connection step is preferably 140°C or higher, more preferably 160°C or higher, and preferably 450°C or lower, more preferably 250°C or lower, and even more preferably 220°C or lower.

[0086] Heating methods for the above connection process include a method of heating the entire connection structure using a reflow furnace or an oven to a temperature above the melting point of the solder and above the curing temperature of the thermosetting component, and a method of locally heating only the connection portion of the connection structure.

[0087] Examples of tools used for localized heating include a hot plate, a heat gun that applies hot air, a soldering iron, and an infrared heater.

[0088] Furthermore, when heating locally with a hot plate, it is preferable to form the top surface of the hot plate with a metal having high thermal conductivity directly below the connection part, and with a material having low thermal conductivity such as fluororesin for other areas where heating is not desirable.

[0089] In the present invention, a metal mask having openings X is used, allowing for good placement of the conductive paste on the first electrodes even when the distance between adjacent first electrodes is short. Furthermore, in the present invention, solder particles are more likely to gather between the first and second electrodes, and the uniformity of the amount of solder condensed on each electrode can be improved. Therefore, solder particles can be efficiently placed on the electrodes (lines). In the present invention, the uniformity of the amount of solder can be further improved across multiple solder portions. Furthermore, some of the solder particles are less likely to be placed in areas (spaces) where no electrodes are formed, significantly reducing the amount of solder particles placed in areas where no electrodes are formed. Therefore, the reliability of conductivity between the first and second electrodes can be improved. Furthermore, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, thereby improving insulation reliability.

[0090] (Connection target parts) The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors, and diodes, as well as electronic components such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

[0091] At least one of the first and second connection target members is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate. Resin films, flexible printed circuit boards, flexible flat cables, and rigid-flexible substrates have the properties of being highly flexible and relatively lightweight. When a conductive film is used to connect such connection target members, solder tends to be less likely to collect on the electrodes. In contrast, by using a conductive paste, solder can be efficiently collected on the electrodes even when a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate is used, thereby sufficiently improving the conductivity reliability between electrodes. When a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate is used, the effect of improving the conductivity reliability between electrodes by not applying pressure can be more effectively achieved compared to when other connection target members such as semiconductor chips are used.

[0092] Examples of the electrode provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connection target member is a flexible printed circuit board, the electrode is preferably a gold electrode, nickel electrode, tin electrode, silver electrode, or copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, copper electrode, molybdenum electrode, silver electrode, or tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode made of aluminum alone, or an electrode in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

[0093] In the connection structure according to the present invention, the first electrode and the second electrode are preferably arranged in an area array or peripheral arrangement. When the first electrode and the second electrode are arranged in an area array or peripheral arrangement, solder can be more effectively concentrated on the electrodes. The area array refers to a structure in which the electrodes are arranged in a grid pattern on the surface of the connection target component on which the electrodes are arranged. The peripheral arrangement refers to a structure in which the electrodes are arranged on the outer periphery of the connection target component. In a structure in which the electrodes are arranged in a comb-like pattern, solder only needs to be concentrated in a direction perpendicular to the combs, whereas in the area array or peripheral structure, solder must be concentrated uniformly over the entire surface on which the electrodes are arranged. Therefore, while conventional methods tend to result in uneven solder amounts, the method of the present invention allows solder to be concentrated uniformly over the entire surface.

[0094] As described above, the first connection target member may have a convex partition portion on the surface on the first electrode side in a portion where the first electrode is not present.

[0095] The shape of the partition is not particularly limited.

[0096] The height of the partition is preferably higher than that of the first electrode. The height of the partition is preferably 20 μm or more higher than that of the first electrode, more preferably 25 μm or more higher, preferably 30 μm or less higher, and more preferably 27 μm or less higher. The height of the first electrode is the height of the exposed electrode portion.

[0097] The material of the partition is not particularly limited, and examples of the material of the partition include glass epoxy and glass.

[0098] A method for obtaining a first connection target member having a partitioning portion includes a method of later attaching a partitioning portion between electrodes.

[0099] (Conductive paste) The conductive paste is preferably an anisotropic conductive paste, is suitable for use in electrical connection of electrodes, and is preferably a circuit connecting material.

[0100] <Solder particles> The conductive paste includes a plurality of solder particles.

[0101] The solder particles are formed of solder at both the center and the outer surface. The solder particles are particles in which both the center and the outer surface are solder. If conductive particles comprising a base particle formed from a material other than solder and a solder portion arranged on the surface of the base particle are used instead of the solder particles, the conductive particles are less likely to gather on the electrode. Furthermore, since the conductive particles have low solder bonding between the conductive particles, the conductive particles that have moved onto the electrode tend to easily move outside the electrode, and the effect of suppressing misalignment between the electrodes also tends to be reduced.

[0102] The solder is preferably a metal (low melting point metal) having a melting point of 450°C or less. The solder particles are preferably metal particles (low melting point metal particles) having a melting point of 450°C or less. The low melting point metal particles are particles containing a low melting point metal. The low melting point metal refers to a metal having a melting point of 450°C or less. The melting point of the low melting point metal is preferably 300°C or less, more preferably 230°C or less. The solder is preferably a low melting point solder having a melting point of less than 230°C.

[0103] The melting point of the solder particles can be determined by differential scanning calorimetry (DSC). Examples of DSC devices include the "EXSTAR DSC7020" manufactured by SII Corporation.

[0104] Furthermore, the solder particles preferably contain tin. The tin content of the solder particles, based on 100% by weight of the metals contained in the solder particles, is preferably 30% by weight or more, more preferably 40% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the tin content in the solder particles is equal to or greater than the lower limit, the electrical continuity reliability and connection reliability between the solder portion and the electrode are further improved.

[0105] The tin content can be measured using a high-frequency inductively coupled plasma atomic emission spectrometer ("ICP-AES" manufactured by Horiba, Ltd.) or a fluorescent X-ray analyzer ("EDX-800HS" manufactured by Shimadzu Corporation).

[0106] By using the solder particles, the solder melts and bonds to the electrodes, and the solder portion establishes electrical continuity between the electrodes. For example, the solder portion and the electrodes are more likely to have surface contact rather than point contact, which reduces connection resistance. Furthermore, the use of the solder particles increases the bonding strength between the solder portion and the electrodes, making it even less likely for the solder portion and the electrodes to peel off, thereby further improving the reliability of electrical continuity and connection.

[0107] The low-melting-point metal constituting the solder particles is not particularly limited. The low-melting-point metal is preferably tin or an alloy containing tin. Examples of such alloys include tin-silver alloys, tin-copper alloys, tin-silver-copper alloys, tin-bismuth alloys, tin-zinc alloys, and tin-indium alloys. Because of their excellent wettability with electrodes, the low-melting-point metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, or a tin-indium alloy. The low-melting-point metal is more preferably a tin-bismuth alloy or a tin-indium alloy.

[0108] To further increase the bond strength between the solder part and the electrode, the solder particles may contain metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. Furthermore, from the viewpoint of further increasing the bond strength between the solder part and the electrode, the solder particles preferably contain nickel, copper, antimony, aluminum, or zinc. To further increase the bond strength between the solder part and the electrode, the content of these metals is preferably 0.0001 wt % or more and preferably 1 wt % or less based on 100 wt % of the metals contained in the solder particles.

[0109] The content of the solder particles in 100% by weight of the conductive paste is preferably 40% by weight or more, more preferably 45% by weight or more, even more preferably 50% by weight or more, and most preferably 55% by weight or more, and is preferably 90% by weight or less, more preferably 85% by weight or less, and even more preferably 80% by weight or less. When the content of the solder particles is equal to or greater than the lower limit and equal to or less than the upper limit, the solder can be more efficiently arranged on the electrodes, making it easier to arrange a large amount of solder between the electrodes, and the electrical conductivity reliability can be more effectively improved. From the viewpoint of more effectively improving the electrical conductivity reliability, the higher the content of the solder particles, the better.

[0110] <Thermosetting component> The conductive paste may contain a thermosetting component. The thermosetting component preferably contains a thermosetting compound. The conductive paste may contain a thermosetting compound and a thermosetting agent as the thermosetting component. In order to cure the conductive paste more satisfactorily, the conductive paste preferably contains a thermosetting compound and a thermosetting agent as the thermosetting component. In order to cure the conductive paste more satisfactorily, the conductive paste preferably contains a curing accelerator as the thermosetting component.

[0111] (Thermosetting component: thermosetting compound) The conductive paste preferably contains a thermosetting compound. The thermosetting compound is a compound that can be cured by heating. The thermosetting compound is not particularly limited. Examples of the thermosetting compound include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. From the viewpoint of further improving the curability and viscosity of the conductive paste and further increasing the conduction reliability, epoxy compounds or episulfide compounds are preferred, and epoxy compounds are more preferred. The conductive paste preferably contains an epoxy compound. Only one type of the thermosetting compound may be used, or two or more types may be used in combination.

[0112] The epoxy compound is a compound having at least one epoxy group. Examples of the epoxy compound include bisphenol A epoxy compounds, bisphenol F epoxy compounds, bisphenol S epoxy compounds, phenol novolac epoxy compounds, biphenyl epoxy compounds, biphenyl novolac epoxy compounds, biphenol epoxy compounds, naphthalene epoxy compounds, fluorene epoxy compounds, phenol aralkyl epoxy compounds, naphthol aralkyl epoxy compounds, dicyclopentadiene epoxy compounds, anthracene epoxy compounds, epoxy compounds having an adamantane skeleton, epoxy compounds having a tricyclodecane skeleton, naphthylene ether epoxy compounds, and epoxy compounds having a triazine nucleus in the skeleton. The epoxy compounds may be used alone or in combination of two or more.

[0113] The epoxy compound is liquid or solid at room temperature (23°C). If the epoxy compound is solid at room temperature, the melting temperature of the epoxy compound is preferably equal to or lower than the melting point of the solder particles. By using the preferred epoxy compound, the viscosity is high when the connection target components are bonded together, and misalignment between the first connection target component and the second connection target component can be suppressed when acceleration is applied due to an impact during transportation, etc. Furthermore, the heat generated during curing can significantly reduce the viscosity of the conductive paste, allowing the solder to efficiently aggregate during conductive connection.

[0114] From the viewpoint of more effectively improving insulation reliability and more effectively improving conduction reliability, it is preferable that the thermosetting component contains an epoxy compound, and it is preferable that the thermosetting compound contains an epoxy compound.

[0115] From the viewpoint of disposing the solder on the electrodes more effectively, the thermosetting compound preferably includes a thermosetting compound having a polyether skeleton.

[0116] Examples of the thermosetting compound having a polyether skeleton include a compound having glycidyl ether groups at both ends of an alkyl chain having 3 to 12 carbon atoms, and a polyether epoxy compound having a polyether skeleton having 2 to 4 carbon atoms and a structural unit in which 2 to 10 polyether skeletons are bonded consecutively.

[0117] From the viewpoint of more effectively increasing the heat resistance of the cured product, the thermosetting compound preferably includes a thermosetting compound having an isocyanuric skeleton.

[0118] Examples of the thermosetting compound having an isocyanuric skeleton include triisocyanurate-type epoxy compounds, such as the TEPIC series (TEPIC-G, TEPIC-S, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC-PAS, TEPIC-VL, TEPIC-UC) manufactured by Nissan Chemical Industries, Ltd.

[0119] From the viewpoints of more efficiently disposing the solder on the electrodes, more effectively improving the reliability of conduction between the upper and lower electrodes to be connected, and more effectively suppressing discoloration of the thermosetting compound, the thermosetting compound preferably has high heat resistance, and is more preferably a novolac epoxy compound. Novolac epoxy compounds have relatively high heat resistance.

[0120] The content of the thermosetting compound in 100% by weight of the conductive paste is preferably 5% by weight or more, more preferably 8% by weight or more, even more preferably 10% by weight or more, and is preferably 99% by weight or less, more preferably 90% by weight or less, even more preferably 80% by weight or less, and particularly preferably 70% by weight or less. When the content of the thermosetting compound is equal to or greater than the lower limit and equal to or less than the upper limit, the solder can be more efficiently arranged on the electrodes, the insulation reliability between the electrodes can be more effectively improved, and the conduction reliability between the electrodes can be more effectively improved. From the viewpoint of more effectively improving impact resistance, the content of the thermosetting compound is preferably higher.

[0121] The content of the epoxy compound in 100% by weight of the conductive paste is preferably 5% by weight or more, more preferably 8% by weight or more, even more preferably 10% by weight or more, and is preferably 99% by weight or less, more preferably 90% by weight or less, even more preferably 80% by weight or less, and particularly preferably 70% by weight or less. When the content of the epoxy compound is above the lower limit and below the upper limit, the solder can be more efficiently arranged on the electrodes, the insulation reliability between the electrodes can be more effectively improved, and the conduction reliability between the electrodes can be more effectively improved. From the viewpoint of further improving impact resistance, a higher content of the epoxy compound is preferable.

[0122] (Thermosetting component: thermosetting agent) The conductive paste may contain a thermosetting agent. The conductive paste may contain a thermosetting agent together with the thermosetting compound. The thermosetting agent thermally cures the thermosetting compound. The thermosetting agent is not particularly limited. Examples of the thermosetting agent include imidazole curing agents, phenol curing agents, thiol curing agents, amine curing agents, acid anhydride curing agents, thermal cation curing agents, and thermal radical generators. Only one type of the thermosetting agent may be used, or two or more types may be used in combination.

[0123] From the viewpoint of enabling the conductive paste to be cured more quickly at low temperatures, the thermosetting agent is preferably an imidazole curing agent, a thiol curing agent, or an amine curing agent. Furthermore, from the viewpoint of improving storage stability when the thermosetting compound and the thermosetting agent are mixed, the thermosetting agent is preferably a latent curing agent. The latent curing agent is preferably a latent imidazole curing agent, a latent thiol curing agent, or a latent amine curing agent. The thermosetting agent may be coated with a polymeric substance such as a polyurethane resin or a polyester resin.

[0124] The imidazole curing agent is not particularly limited, and examples of the imidazole curing agent include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroximide, 2-methyl-4-methylimidazole ... Examples of the imidazole compounds include 2-amino-4-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-para-toluyl-4-methyl-5-hydroxymethylimidazole, 2-meta-toluyl-4-methyl-5-hydroxymethylimidazole, 2-meta-toluyl-4,5-dihydroxymethylimidazole, and 2-para-toluyl-4,5-dihydroxymethylimidazole, in which the hydrogen at the 5-position of 1H-imidazole is substituted with a hydroxymethyl group and the hydrogen at the 2-position with a phenyl group or a toluyl group.

[0125] The thiol curing agent is not particularly limited, and examples of the thiol curing agent include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate.

[0126] The amine curing agent is not particularly limited, and examples of the amine curing agent include hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5.5]undecane, bis(4-aminocyclohexyl)methane, metaphenylenediamine, and diaminodiphenyl sulfone.

[0127] The acid anhydride curing agent is not particularly limited, and any acid anhydride that is used as a curing agent for thermosetting compounds such as epoxy compounds can be widely used. Examples of the acid anhydride curing agent include phthalic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, anhydrides of phthalic acid derivatives, maleic anhydride, nadic anhydride, methylnadic anhydride, glutaric anhydride, succinic anhydride, glycerin bistrimellitic anhydride monoacetate, and ethylene glycol bistrimellitic anhydride, bifunctional acid anhydride curing agents such as trimellitic anhydride, and tetrafunctional or higher acid anhydride curing agents such as pyromellitic anhydride, benzophenonetetracarboxylic anhydride, methylcyclohexenetetracarboxylic anhydride, and polyazelaic anhydride.

[0128] The thermal cationic initiator is not particularly limited. Examples of the thermal cationic initiator include an iodonium cationic curing agent, an oxonium cationic curing agent, and a sulfonium cationic curing agent. Examples of the iodonium cationic curing agent include bis(4-tert-butylphenyl)iodonium hexafluorophosphate. Examples of the oxonium cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the sulfonium cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate.

[0129] The thermal radical generator is not particularly limited. Examples of the thermal radical generator include azo compounds and organic peroxides. Examples of the azo compounds include azobisisobutyronitrile (AIBN). Examples of the organic peroxides include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

[0130] The content of the thermosetting agent is not particularly limited. The content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, and preferably 200 parts by weight or less, more preferably 100 parts by weight or less, and even more preferably 75 parts by weight or less, relative to 100 parts by weight of the thermosetting compound. When the content of the thermosetting agent is equal to or greater than the lower limit, the conductive paste can be easily cured sufficiently. When the content of the thermosetting agent is equal to or less than the upper limit, excess thermosetting agent that is not involved in curing is less likely to remain after curing, and the heat resistance of the cured product is further improved.

[0131] (Thermosetting component: Curing accelerator) The conductive paste may contain a curing accelerator. The curing accelerator is not particularly limited. The curing accelerator preferably acts as a curing catalyst in the reaction between the thermosetting compound and the thermosetting agent. The curing accelerator preferably acts as a curing catalyst in the reaction with the thermosetting compound. Only one type of the curing accelerator may be used, or two or more types may be used in combination.

[0132] Examples of the curing accelerator include phosphonium salts, tertiary amines, tertiary amine salts, quaternary onium salts, tertiary phosphines, crown ether complexes, amine complex compounds, and phosphonium ylides. Specific examples of the curing accelerator include imidazole compounds, isocyanurates of imidazole compounds, dicyandiamide, derivatives of dicyandiamide, melamine compounds, derivatives of melamine compounds, amine compounds such as diaminomaleonitrile, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, bis(hexamethylene)triamine, triethanolamine, diaminodiphenylmethane, and organic acid dihydrazides, 1,8-diazabicyclo[5,4,0]undecene-7, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, boron trifluoride, boron trifluoride-amine complex compounds, and organic phosphorus compounds such as triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine.

[0133] The phosphonium salt is not particularly limited, and examples of the phosphonium salt include tetra-normal-butylphosphonium bromide, tetra-normal-butylphosphonium OO diethyldithiophosphate, methyltributylphosphonium dimethylphosphate, tetra-normal-butylphosphonium benzotriazole, tetra-normal-butylphosphonium tetrafluoroborate, and tetra-normal-butylphosphonium tetraphenylborate.

[0134] The content of the curing accelerator is appropriately selected so that the thermosetting compound is cured satisfactorily. The content of the curing accelerator per 100 parts by weight of the thermosetting compound is preferably 0.5 parts by weight or more, more preferably 0.8 parts by weight or more, and preferably 10 parts by weight or less, more preferably 8 parts by weight or less. When the content of the curing accelerator is equal to or greater than the lower limit and equal to or less than the upper limit, the thermosetting compound can be cured satisfactorily. Furthermore, when the content of the curing accelerator is equal to or greater than the lower limit and equal to or less than the upper limit, the solder can be more efficiently arranged on the electrodes, and the electrical connection reliability between the upper and lower electrodes to be connected can be more effectively improved.

[0135] (Other ingredients) The conductive paste may contain various additives, as needed, such as flux, filler, extender, softener, plasticizer, thickener, thixotropic agent, leveling agent, polymerization catalyst, curing catalyst, colorant, antioxidant, heat stabilizer, light stabilizer, ultraviolet absorber, lubricant, antistatic agent, and flame retardant.

[0136] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0137] The following materials were prepared for the conductive paste.

[0138] Thermosetting component (thermosetting compound): Thermosetting compound 1: Phenol novolac epoxy compound, "DEN431" manufactured by Dow Chemical Company Thermosetting compound 2: Bisphenol F type epoxy compound, "DER354" manufactured by Dow Chemical Company

[0139] Thermosetting component (cure accelerator): "Boron trifluoride ethylamine" manufactured by Tokyo Chemical Industry Co., Ltd.

[0140] Solder particles: SnBi solder particles, "Sn42Bi58ST-3" manufactured by Mitsui Mining & Smelting Co., Ltd., melting point 138°C

[0141] Flux: Adipic acid benzylamine salt (melting point 170°C)

[0142] Preparation of adipic acid benzylamine salt: A mixed solvent of 200 g of water and 350 g of ethanol was added to a glass beaker as the reaction solvent, and 70.719 g of adipic acid (Tokyo Chemical Industry Co., Ltd., melting point 153°C) was added and dissolved at room temperature until homogeneous. Next, 96.452 g of benzylamine (Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was heated and stirred at 100°C for approximately 10 minutes to obtain a mixed solution. The resulting mixed solution was placed in a refrigerator at 5°C to 10°C and left overnight. The precipitated crystals were separated by filtration, washed with water, and vacuum dried to obtain a flux.

[0143] The melting points of the solder particles and the flux were measured using a differential scanning calorimetry (DSC) device ("EXSTAR DSC7020" manufactured by SII Corporation).

[0144] The following metal masks A to H were prepared.

[0145] Metal mask A having an opening X of the approximate shape shown in FIG. 1: Maximum opening width A of opening X: 170 μm Minimum aperture width B: 52 μm Opening length of opening X: 380 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture X): 0.31 Contours of both ends of opening X in the longitudinal direction: curved Contour of the drawer: curved

[0146] Metal mask B having an opening X of the approximate shape shown in FIG. 1: Maximum opening width A of opening X: 165 μm Minimum aperture width B: 67 μm Opening length of opening X: 385 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture X): 0.41 Contours of both ends of opening X in the longitudinal direction: curved Contour of the drawer: curved

[0147] Metal mask C having an opening X of the approximate shape shown in FIG. 1: Maximum opening width A of opening X: 162 μm Minimum aperture width B: 77 μm Opening length of opening X: 391 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture X): 0.48 Contours of both ends of opening X in the longitudinal direction: curved Contour of the drawer: curved

[0148] Metal mask D having an opening X of the approximate shape shown in FIG. 2: Maximum opening width A of opening X: 162 μm Minimum aperture width B: 91 μm Opening length of opening X: 377 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture X): 0.56 Contours of both ends of opening X in the longitudinal direction: curved Contour of the drawing part: Straight line

[0149] Metal mask E having an opening X of the approximate shape shown in FIG. 2: Maximum opening width A of opening X: 140 μm Minimum aperture width B: 98 μm Aperture length: 335 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture X): 0.70 Contours of both ends of opening X in the longitudinal direction: curved Contour of the drawing part: Straight line

[0150] Metal mask F having openings Y of the approximate shape shown in FIG. 7: Maximum opening width A of opening Y: 170 μm Minimum aperture width B: 41 μm Opening length of opening Y: 380 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture Y): 0.24 Contours of both ends of the length of opening Y: curved Contour of the drawer: curved

[0151] Metal mask G having openings Y of the approximate shape shown in FIG. 6: Maximum opening width A of opening Y: 160 μm Minimum aperture width B: 120 μm Opening length of opening Y: 365 μm Ratio (minimum aperture width B of aperture section / maximum aperture width A of aperture Y): 0.75 Contours of both ends of the length of opening Y: curved Contour of the drawing part: Straight line

[0152] Metal mass H having an opening that is rectangular in plan view: Minimum and maximum opening width: 140 μm Aperture length: 335 μm Ratio (minimum opening width / maximum opening width): 1 Contours of both ends of the opening length: Straight line No constriction (all contours are straight)

[0153] Example 1 (1) Preparation of anisotropic conductive paste An anisotropic conductive paste was obtained by blending 100 parts by weight of a thermosetting compound (50 parts by weight of thermosetting compound 1, 50 parts by weight of thermosetting compound 2), 30 parts by weight of a curing accelerator, 162 parts by weight of solder particles, and 3 parts by weight of flux.

[0154] (2) Preparation of test connection structure (P) (L / S = 120 μm / 95 μm) As the first connection target component, a glass epoxy substrate (FR-4 substrate, thickness 0.5 mm) having a copper electrode pattern (first electrode, L / S = 120 μm / 95 μm, electrode length: 140 μm, electrode thickness: 15 μm) on its surface (top surface) was prepared.

[0155] Metal mask A was placed on the first connection target component so that one of the adjacent first electrodes faced the first wide portion of the opening, and the other first electrode faced the second wide portion of the opening. An anisotropic conductive paste was then placed on the upper surface of the connection target component. The anisotropic conductive paste layer was then heated to a temperature of the solder particle melting point minus 10°C 30 seconds after the start of the temperature increase, and this temperature was maintained for 30 to 40 seconds after the start of the temperature increase. The anisotropic conductive paste layer was then heated to a temperature of the solder particle melting point plus 80°C 70 seconds after the start of the temperature increase, hardening the anisotropic conductive paste layer and obtaining a test connection structure (P). Note that no pressure was applied during heating. The obtained test connection structure (P) did not use a second connection target component.

[0156] (3) Fabrication of connection structure (Q) (L / S = 120 μm / 95 μm) As the first connection target component, a glass epoxy substrate (FR-4 substrate, thickness 0.5 mm) having a copper electrode pattern (first electrode, L / S = 120 μm / 95 μm, electrode length: 140 μm, electrode thickness: 15 μm) on its surface (top surface) was prepared.

[0157] As the second connection target member, an LED chip having a copper electrode pattern (second electrode, L / S=120 μm / 95 μm, electrode length: 120 μm) on the bottom surface was prepared.

[0158] A metal mask A was placed on the first connection target component so that one of the adjacent first electrodes faced the first wide portion of the opening, and the other first electrode faced the second wide portion of the opening. An anisotropic conductive paste was then placed on the top surface of the first connection target component (first placement step). Metal mask A was then removed, and a second connection target component was placed on the top surface of the anisotropic conductive paste so that the first electrode and the second electrode faced each other (second placement step). No pressure was applied during this process. The weight of the flexible printed circuit board was added to the anisotropic conductive paste layer. The anisotropic conductive paste layer was then heated to a temperature 10°C below the melting point of the solder particles 30 seconds after the start of heating, and this temperature was maintained for 30 to 40 seconds after the start of heating. Next, the anisotropic conductive paste layer was heated so that its temperature reached the melting point of the solder particles + 80°C 70 seconds after the start of the temperature rise, hardening the anisotropic conductive paste layer, forming a connection, and electrically connecting the first electrode and the second electrode via the solder in the connection (connection process). In this way, a connection structure (Q) was obtained. Note that no pressure was applied during heating. Note that the obtained connection structure (Q) includes a second connection target member.

[0159] (Examples 2 to 5 and Comparative Examples 1 and 2) Test connection structures (P) and (Q) were obtained in the same manner as in Example 1, except that the type of metal mask was changed as shown in Tables 1 and 2.

[0160] (Comparative Example 3) A test connection structure (P) and a connection structure (Q) were obtained in the same manner as in Example 1, except that a metal mask H was used and the metal mask H was positioned so that the openings of the metal mask H faced two adjacent first electrodes.

[0161] (evaluation) (1) Printability The anisotropic conductive paste was placed on a glass plate using a metal mask with the same opening shape as the metal mask on which the anisotropic conductive paste was placed. The shapes of 100 of the placed anisotropic conductive pastes were then measured using a non-contact surface texture measuring device (Mitaka Kohki Co., Ltd., "PF-60"). From the measurement results, the transfer rate of the anisotropic conductive paste was calculated, and the coefficient of variation (CV value) of the transfer rate was calculated. The printability (1) and (2) were evaluated according to the following criteria. The better the results of printability (1) and (2), the better the conductive paste was placed on two adjacent electrodes using one opening in the metal mask.

[0162] The transfer rate (transfer area rate and transfer height rate) is calculated as follows.

[0163] Transfer area ratio (%) = (A / S) x 100 Transfer height ratio (%) = (B / H) x 100 A: Measured area of ​​the transcript S: Opening area of ​​metal mask B: Actual measured height of the transfer H: Metal mask thickness

[0164] [Criteria for printability (1)] ○: Transfer area rate is 80% or more △: Transfer area rate is 50% or more but less than 80% ×: Transfer area rate is less than 50%

[0165] The coefficient of variation (CV value) of the transfer rate was calculated as follows: The CV value calculated using the standard deviation of the transfer area rate and the average value of the transfer area rate (CV value of the transfer area rate) was compared with the CV value calculated using the standard deviation of the transfer height rate and the average value of the transfer height rate (CV value of the transfer height rate), and the larger value was used to judge printability (2).

[0166] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of transfer area ratio or transfer height ratio Dn: average value of transfer area rate or transfer height rate

[0167] [Criteria for printability (2)] ○: The larger of the CV value of the transfer area rate and the CV value of the transfer height rate is less than 0.2% △: The larger of the CV value of the transfer area ratio and the CV value of the transfer hardness ratio is 0.2% or more and less than 0.3% ×: The larger of the CV value of the transfer area rate and the CV value of the transfer height rate is 0.3% or more

[0168] (2) Uniformity of the amount of solder condensed on each electrode In the obtained test connection structure (P), adjacent first electrodes (X) and (Y) with conductive paste placed in one opening were identified, and second electrodes (X) and (Y) were placed opposite them to obtain a test connection structure (P2). Next, an X-ray transmission image of the test connection structure (P2) was obtained using an X-ray transmission device (Hitachi Engineering Co., Ltd., "MF100C"). Next, image processing of the X-ray transmission image was performed using image processing software "ImageJ," and the amount of solder (X) placed between the first electrode (X) and the second electrode (X) and the amount of solder (Y) placed between the first electrode (Y) and the second electrode (Y) were converted into pixel values. Next, the sum of the solder amount (X) and the solder amount (Y) was set to 100%, and the absolute value (Z) of the difference between the solder amount (X) and the solder amount (Y) was measured.

[0169] The absolute values ​​(Z) were determined for each of the 200 electrodes, and the average value and maximum value of the absolute values ​​(Z) were calculated. The average value of the absolute values ​​(Z) is preferably less than 9%.

[0170] [Criteria for determining uniformity of the amount of solder condensed on each electrode] ○○: The average absolute value (Z) is less than 7% ○: The average absolute value (Z) is 7% or more and less than 9% △: The average absolute value (Z) is 9% or more and less than 11% ×: The average absolute value (Z) is 11% or more

[0171] The results are shown in Tables 1 and 2 below.

[0172] [Table 1]

[0173] [Table 2]

[0174] (2) Evaluation of the uniformity of the amount of solder condensed on each electrode was performed using a test connection structure (P2) in which second electrodes (X) and (Y) were arranged on the test connection structure (P). Even when the connection structure (Q) was used, the results of the uniformity of the amount of solder condensed on each electrode tended to be similar. The connection structures (Q) of Examples 1 to 5 tended to be superior in the uniformity of the amount of solder condensed on each electrode compared to the connection structures (Q) of Comparative Examples 1 to 3. [Explanation of symbols]

[0175] 1, 1A...first connection target member 1a...first electrode 2...Second connecting member 2a...Second electrode 3...Conductive paste 3A...solder particles 3B…Thermosetting component 4...Connection 4A...Solder part 4B…Cured product part 5...Partition 10, 10A, 100, 100A...metal mask 11, 11A, 101, 101A...First wide section 12, 12A, 102, 102A...Second wide section 13, 13A, 103, 103A...Throttling section 20...Connection structure

Claims

1. a first placement step of placing an anisotropic conductive paste containing a plurality of solder particles and a thermosetting component on a surface of a first connection target member having a plurality of first electrodes on a surface thereof, using a metal mask; a second placement step of placing a second connection target member having a plurality of second electrodes on a surface of the anisotropic conductive paste opposite the first connection target member side, so that the first electrodes and the second electrodes face each other; a connecting step of forming a connection portion connecting the first connection target member and the second connection target member by using the anisotropic conductive paste by heating the anisotropic conductive paste to a temperature equal to or higher than the melting point of the solder particles and equal to or higher than the hardening temperature of the thermosetting component, the metal mask has an opening having a length direction and a width direction, the opening has a narrowed portion having a small opening width in a central portion in the longitudinal direction, a first wide portion connected to one side of the narrowed portion in the longitudinal direction and having a larger opening width than the narrowed portion, and a second wide portion connected to the other side of the narrowed portion in the longitudinal direction and having a larger opening width than the narrowed portion, When the maximum opening width of the opening portion is A and the minimum opening width of the throttle portion is B, B / A is 0.3 or more and 0.7 or less, In the first arranging step, the metal mask is arranged so that one of the adjacent first electrodes faces the first wide portion and the other of the adjacent first electrodes faces the second wide portion; A method for manufacturing a connection structure, wherein in the connection process, a connection portion is formed having a solder portion formed by joining a plurality of the solder particles and a hardened portion formed by thermally hardening the thermosetting component, the first electrode and the second electrode are electrically connected by the solder portion in the connection portion, and the hardened portion in the connection portion is formed in an area where the first electrode and the second electrode are not formed.

2. The method for manufacturing a connection structure according to claim 1 , wherein the contours of both ends of the opening in the length direction include curved lines.

3. the first connection target member has a convex partition portion on a surface on the first electrode side in a portion where the first electrode is not present, The method for manufacturing a connection structure according to claim 1 or 2, wherein in the first arranging step, the metal mask is arranged so that at least a part of the partition portion faces the drawn portion.

4. The method for manufacturing a connection structure according to any one of claims 1 to 3, wherein the contour of the drawn portion includes a curve.

5. The method for manufacturing a connection structure according to any one of claims 1 to 3, wherein the contour of the drawn portion includes a straight line.

6. A method for manufacturing a connection structure described in any one of claims 1 to 5, wherein in the first placement step, the metal mask is positioned so that the entirety of one of the adjacent first electrodes faces the first wide portion, and so that the entirety of the other first electrode faces the second wide portion.

7. The anisotropic conductive paste includes a thermosetting compound as the thermosetting component, A method for manufacturing a connection structure described in any one of claims 1 to 5, wherein the content of the multiple solder particles is 90% by weight or less and the content of the thermosetting compound is 5% by weight or more in 100% by weight of the anisotropic conductive paste.

8. The anisotropic conductive paste includes a thermosetting compound as the thermosetting component, the content of the plurality of solder particles is 90% by weight or less and the content of the thermosetting compound is 5% by weight or more in 100% by weight of the anisotropic conductive paste; The method for manufacturing a connection structure described in any one of claims 1 to 5, wherein in the first placement step, the metal mask is placed so that of adjacent first electrodes, the entirety of one first electrode faces the first wide portion and the entirety of the other first electrode faces the second wide portion.

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