lead frame

Abstract

The problem is to provide a lead frame which is a lead frame in which silver plating is performed as electroplating of the top surface, side surface, and bottom surface of a lead frame base material as the outermost layer while reducing cost, operation time, and improving productivity, can suppress the thickness of the entire plating layer including the silver plating layer to be thin, and significantly improves adhesion to sealing resin. The solution is to provide a lead frame in which, among the top surface, side surface, and bottom surface of a lead frame base material (10) composed of a copper-based material, a plating layer (12, 13) in which nickel, palladium, and gold are sequentially stacked is provided on the top surface and bottom surface, and a roughened silver plating layer (11) having a needle-shaped protrusion group is provided as the outermost layer plating layer on the side surface, and the roughened silver plating layer has a crystal structure in which the ratio of crystal orientation <101> is the highest among the ratios of crystal orientations <001>, <111>, and <101>.

Description

TECHNICAL FIELD

[0001] The present application relates to a lead frame for semiconductor, in which silver plating is applied to the side surface of the upper surface, side surface and lower surface of the lead frame substrate as the topmost layer plating. BACKGROUND

[0002] The lead frame is one of components for mounting semiconductor elements. In the past, a lead frame in which silver plating is applied to the entire surface or a part of the lead frame substrate as the topmost layer plating has been used in large quantities, but the adhesion of silver or silver-containing alloy to sealing resin is poor, and the lead frame and the sealing resin are easily peeled off due to impact or heat, so that there is a problem in reliability.

[0003] To solve this problem, a method is known in which the surface of the lead frame substrate is roughened to have a concave-convex structure by micro-etching treatment, thereby producing a physical anchoring effect and improving the adhesion to the sealing resin.

[0004] However, the lead frame substrate used in large quantities in the manufacture of the lead frame is formed of a copper alloy containing silicon, and impurity residues called smut are generated due to the micro-etching treatment. Therefore, a method in which the surface of the lead frame substrate composed of a copper alloy is roughened to have a concave-convex structure by micro-etching treatment cannot be used.

[0005] Further, in the case of the lead frame using the lead frame substrate composed of a copper alloy, in order to ensure good adhesion to a metal wire used when a semiconductor element is joined, it is necessary to minimize the influence of diffusion of copper present in the lead frame substrate composed of a copper alloy of the base. Therefore, in the case where a plating layer composed of a noble metal such as silver or silver-containing alloy or a noble metal alloy is formed directly on the lead frame substrate composed of a copper alloy without providing a base plating layer, it is generally necessary to make the thickness of the plating layer composed of a noble metal or a noble metal alloy 2 μm or more.

[0006] On the other hand, in recent years, high-density mounting of light, thin and short semiconductor packages is required for miniaturization and cost reduction. In order to achieve miniaturization, it is required to make the thickness of the plating layer thinner, and from the viewpoint of cost reduction, it is also required to make the thickness of the plating layer composed of a noble metal or a noble metal alloy thinner.

[0007] In the lead frame using the lead frame substrate composed of a copper alloy, as one of countermeasures for making the thickness of the plating layer composed of a noble metal or a noble metal alloy thin, there is a method in which, as a base plating layer of the plating layer composed of a noble metal or a noble metal alloy, a plating layer is formed of nickel or a nickel-containing alloy having an effect of suppressing diffusion of copper, thereby making the thickness of the plating layer composed of a noble metal or a noble metal alloy thin.

[0008] However, even if the plating layer composed of a noble metal or a noble metal alloy is made thin, the adhesion to the resin cannot be improved.

[0009] As a prior art related to these problems, Patent Literature 1 discloses the following technology on a base plating layer of a plating layer composed of a noble metal or a noble metal alloy: forming a dense and flat nickel plating layer on the entire surface of a copper alloy, forming a nickel plating layer on which longitudinal crystal growth is preferential to lateral crystal growth, and making the surface a surface having unevenness, thereby producing a physical anchoring effect and improving the adhesion to a sealing resin.

[0010] Further, Patent Literature 2 discloses the following technology on a base plating layer of a plating layer composed of a noble metal or a noble metal alloy: forming a mountain-shaped nickel plating layer on a copper alloy, and then forming a nickel plating layer having good flow properties thereon so as to make the unevenness semi-spherical, thereby improving the adhesion to a sealing resin and preventing the exudation of an epoxy resin component.

[0011] Further, Patent Literature 3 discloses a technology of forming a noble metal plating layer composed of a gold layer and a silver layer on a nickel layer having a rough surface.

[0012] Prior Art Documents

[0013] Patent Literature

[0014] Patent Literature 1: Japanese Patent No. 3259894

[0015] Patent Literature 2: Japanese Patent No. 4853508

[0016] Patent Literature 3: Japanese Patent No. 5151438 SUMMARY

[0017] PROBLEMS TO BE SOLVED BY THE INVENTION

[0018] The technologies of these patent literatures are technologies of forming a base plating layer so that the surface becomes a roughened surface, and then stacking a noble metal plating layer so as to follow the shape of the roughened surface, in order to improve the adhesion to the resin. However, in order to form the roughened surface of the base plating layer into a surface having unevenness that can improve the adhesion to the resin even if the noble metal plating layer is stacked, it is necessary to form the base plating layer thick, and since the plating speed is slow in order to make the base plating layer a roughened surface, the operation time increases, the cost increases, and the productivity decreases.

[0019] Further, as another means for improving adhesion to resin, it is considered to roughen the surface of the noble metal plating layer after forming a smooth noble metal plating layer on the surface of the lead frame substrate, but in order to form the surface of the noble metal plating layer into a roughened surface having a concavo-convex shape capable of improving adhesion to resin, it is necessary to form the smooth noble metal plating layer before forming the roughened surface relatively thick, and thus the cost of the noble metal plating layer increases and the productivity decreases.

[0020] Further, if the surface is roughened after forming a smooth plating layer, the plating metal removed at the time of roughening is wasted.

[0021] However, the present inventors have conducted repeated experiments and as a result, it has been clarified that there is room for reducing the cost, operation time, and improving the productivity for forming a roughened surface of the surface, while controlling the thickness of the entire plating layer including the silver plating layer to be relatively thin and significantly improving adhesion to sealing resin, compared to the technologies disclosed in each of the above patent documents.

[0022] The present application has been made in view of the above problem, and an object thereof is to provide a lead frame which is a lead frame in which silver plating is implemented as the topmost layer plating on the side surface among the upper surface, side surface, and lower surface of a lead frame substrate, and which is capable of reducing cost, operation time, and improving productivity, while suppressing the thickness of the entire plating layer including the silver plating layer to be relatively thin and significantly improving adhesion to sealing resin.

[0023] Method for solving the problem

[0024] In order to solve the above problem, the lead frame of the present application is characterized in that among the upper surface, side surface, and lower surface of a lead frame substrate composed of a copper-based material, a plating layer in which nickel, palladium, and gold are sequentially stacked is provided on the upper surface and lower surface, and a roughened silver plating layer having a group of needle-shaped protrusions is provided as the topmost layer plating on the side surface, and the roughened silver plating layer has a crystal structure in which the ratio of crystal orientation <101> is the highest among the ratios of crystal orientations <001>, <111>, and <101>.

[0025] Further, preferably, in the lead frame of the present application, the average crystal grain size of the roughened silver plating layer is less than 0.28 μm.

[0026] Further, preferably, in the lead frame of the present application, a base plating layer is provided between the lead frame substrate and the roughened silver plating layer.

[0027] Effects of the invention

[0028] According to the present application, a lead frame can be obtained, which is a lead frame in which silver plating is performed as a topmost layer plating on the upper surface, side surface, and lower surface of a lead frame substrate, and in which the side surface is reduced in cost, operation time, and production rate, and the thickness of the entire plating layer including the silver plating layer is suppressed to be thin, and the adhesion to sealing resin is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 FIG. 1 is a diagram showing an example of a lead frame according to the first embodiment of the present application, (a) is a top view, (b) is a bottom view, and (c) is a diagram schematically showing the A-A cross section of (a).

[0030] Figure 2 FIG. 2 is a plan view showing an example of a lead frame arranged in multiple columns according to the first embodiment of the present application.

[0031] Figure 3 FIG. 3 is a diagram showing an example and other examples of a manufacturing step of a lead frame for mounting a semiconductor element according to the first embodiment of the present application.

[0032] Figure 4 FIG. 4 is a diagram showing an example of a manufacturing step of a semiconductor package using a lead frame for mounting a semiconductor element according to the first embodiment of the present application.

[0033] Figure 5 FIG. 5 is a diagram showing an example of a lead frame according to the second embodiment of the present application, (a) is a top view, (b) is a bottom view, and (c) is a diagram schematically showing the B-B cross section of (a).

[0034] Figure 6 FIG. 6 is a plan view showing an example of a lead frame arranged in multiple columns according to the second embodiment of the present application.

[0035] Figure 7 FIG. 7 is a diagram showing an example and other examples of a manufacturing step of a lead frame for mounting a semiconductor element according to the second embodiment of the present application.

[0036] Figure 8 FIG. 8 is a diagram showing an example of a manufacturing step of a semiconductor package using a lead frame for mounting a semiconductor element according to the second embodiment of the present application.

[0037] LIST OF SYMBOLS

[0038] 1 - lead frame; 2 - semiconductor package; 10 - lead frame base material (metal plate); 10a - terminal portion for internal connection; 10b - terminal portion for external connection; 10c - pad portion; 11 - roughened silver plating layer; 12 - plating layer for internal connection; 13 - plating layer for external connection; 14 - solder; 15 - sealing resin; 16 - die bond; 17 - wire; 20 - semiconductor element; 31 - 1 - resist mask for first plating; 32 - resist mask for etching (and also for plating); R1 - first resist layer; R2 - second resist layer. DETAILED DESCRIPTION

[0039] Before explaining the embodiments, the background of the derivation of the present application and the effects of the present application are explained.

[0040] The present inventors believe that, in order to reduce the cost, operation time for forming the roughened surface, improve the productivity, while improving the adhesion to the sealing resin, and make the thickness of the plating layer as a whole thin, it is necessary to take the following measures: for the lead frame base material, not to provide a base plating layer for surface roughening, to form a silver plating layer for surface roughening without roughening the surface of the smooth silver plating layer, or to form a base plating layer smoothly, and to form a silver plating layer for surface roughening on the base plating layer without roughening the surface of the smooth silver plating layer.

[0041] Thus, the present inventors derived a lead frame, in which, among the upper surface, side surface, and lower surface of a lead frame base material composed of a copper-based material, the side surface is provided with a roughened silver plating layer having a group of needle-shaped protrusions as the outermost plating layer, thereby serving as a silver plating layer for surface roughening without roughening the surface of the smooth silver plating layer.

[0042] Note that, in the present application, the group of needle-shaped protrusions of the roughened silver plating layer refers to a collection of a plurality of needle-shaped protrusions having a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of the smooth surface) of 1.30 or more and 6.00 or less.

[0043] It was clarified that if the roughened silver plating layer is formed to have a group of needle-shaped protrusions having such a surface area ratio, the sealing resin easily flows into the base of each needle-shaped protrusion, and the physical anchoring effect due to the increase in the contact area at the time of curing of the sealing resin and the concave-convex shape can be exerted.

[0044] Further, the present inventors have repeatedly tested the results, and have ascertained that the roughened silver plating layer having the needle-shaped protrusion group is different in crystal structure from the conventional smooth silver plating layer and the roughened silver plating layer having a roughened surface formed by roughening the surface of the smooth silver plating layer, is formed by growing the crystal structure with an increased ratio of a prescribed crystal orientation, and that the roughened surface having the needle-shaped protrusion group formed by the substantial growth of the crystal structure has an effect of significantly improving the adhesion to the sealing resin, thereby leading to the present application.

[0045] The lead frame of the present application has a plating layer of nickel, palladium, and gold successively laminated on the upper surface and the lower surface of the lead frame substrate composed of a copper-based material, and has a roughened silver plating layer having a needle-shaped protrusion group as the outermost layer plating layer on the side surface, the roughened silver plating layer having a crystal structure with the highest ratio of crystal orientation <101> among the respective ratios of crystal orientations <001>, <111>, and <101>.

[0046] If the roughened silver plating layer has a needle-shaped protrusion group with a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of the smooth surface) of 1.30 or more and 6.00 or less as in the lead frame of the present application, the sealing resin easily flows into the base of each needle-shaped protrusion. Therefore, the physical anchoring effect due to the increase in the contact area and the concave-convex shape at the time of curing of the sealing resin can be exerted, and good adhesion is obtained. Note that the extending direction of each needle-shaped protrusion in the needle-shaped protrusion group is not the same, and includes not only the upward direction and the oblique direction, but also a curved needle shape. If each needle-shaped protrusion in the needle-shaped protrusion group is in a random extending state in a radial shape, the anchoring effect to the sealing resin can be further improved.

[0047] Moreover, if the roughened silver plating layer having a needle-shaped protrusion group as the outermost layer plating layer on the side surface of the lead frame substrate composed of a copper-based material is configured to have a crystal structure with the highest ratio of crystal orientation <101> among the respective ratios of crystal orientations <001>, <111>, and <101> as in the lead frame of the present application, the sealing resin more easily enters the deep portion compared to, for example, a silver plating layer having a roughened surface composed of a concave-convex with a surface area ratio (here, the ratio of the surface area of the silver plating layer to the surface area of the smooth surface) of less than 1.30, and compared to a roughened silver plating layer having a conventional crystal structure different from the crystal structure with the highest ratio of crystal orientation <101> among the respective ratios of crystal orientations <001>, <111>, and <101>, and having a roughened surface formed by roughening the surface of a smooth silver plating layer, and the adhesion to the sealing resin is further improved.

[0048] Note that the roughened silver plating layer having the crystal structure with the highest ratio of the crystal orientation <101> among the respective ratios of the crystal orientations <001>, <111>, and <101> and the needle-shaped protrusion group can be formed on the lead frame substrate.

[0049] Furthermore, if the lead frame of the present application is manufactured as such, the adhesion to the sealing resin can be significantly improved by the roughened silver plating layer having the crystal structure with the highest ratio of the crystal orientation <101> among the ratios of the crystal orientations <001>, <111>, and <101> and the needle-shaped protrusion group, and as a result, when it is necessary to form a barrier plating layer for suppressing the diffusion of copper, which is the material of the lead frame substrate, as a base plating layer, it is sufficient to form the barrier plating layer to be thin and smooth to a thickness that suppresses the diffusion of copper of the base, and it is not necessary to form the barrier plating layer with a roughened surface.

[0050] Furthermore, the roughened silver plating layer having the crystal structure with the highest ratio of the crystal orientation <101> among the respective ratios of the crystal orientations <001>, <111>, and <101> and the needle-shaped protrusion group can be formed without roughening the surface of the smooth silver plating layer by silver plating under the conditions described later.

[0051] Therefore, if the lead frame of the present application is manufactured as such, the formation cost of the roughened surface for improving the adhesion to the resin can be minimized, and the thickness of the entire plating layer can be minimized.

[0052] Furthermore, preferably, in the lead frame of the present application, the average crystal grain diameter of the roughened silver plating layer is less than 0.28 μm.

[0053] If the average crystal grain diameter of the roughened silver plating layer is 0.28 μm or more, the interval between the crystals of the silver plating layer becomes wide when the crystals grow in the height direction, and it is not possible to obtain a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of the smooth surface) of 1.30 or more and 6.00 or less.

[0054] If the average crystal grain diameter of the roughened silver plating layer is less than 0.28 μm, the interval between the crystals of the silver plating layer becomes narrow when the crystals grow in the height direction, and a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of the smooth surface) of 1.30 or more and 6.00 or less is obtained. Note that more preferably, the average crystal grain diameter of the roughened silver plating layer is 0.15 μm or more and 0.25 μm or less.

[0055] Note that in the lead frame of the present application, a base plating layer can be provided between the lead frame substrate and the roughened silver plating layer.

[0056] The shape of the needle-like protrusion group possessed by the roughened silver plating layer in the lead frame of the present application preferably does not have any influence on the surface morphology of the base thereof, and is formed only by the roughened silver plating layer, and the surface state of the base can be either smooth or rough. In consideration of cost, etc. in terms of productivity, it is preferable that the base be a roughened silver plating layer formed on a surface subjected to an activation treatment only on the surface of the lead frame base material. In consideration of the influence of diffusion of copper, which is the material of the lead frame base material as the base, in a high temperature environment, a smooth base plating layer can be provided as a barrier plating layer between the lead frame base material and the roughened silver plating layer. In this case, it is sufficient that the plating layer be formed thin and smooth to a thickness that suppresses the diffusion of copper of the base, and therefore a thin base plating layer is preferable.

[0057] Furthermore, in the lead frame of the present application, when a silver plating layer including a roughened silver plating layer is formed directly on the side surface of the lead frame base material without providing a base plating layer thereon, the thickness of the plating layer as a whole possessed by the side surface of the lead frame base material is preferably 0.4 μm or more and 6.0 μm or less. In detail, it is good that a silver strike plating layer having a thickness of 0.2 μm or more and 3.0 μm or less, more preferably 1.5 μm, is formed on the surface of the side surface of the lead frame base material, and a roughened silver plating layer having a needle-like protrusion group on the surface having a thickness of 0.2 μm or more and 3.0 μm or less, more preferably 0.5 μm, is laminated thereon.

[0058] In the case where a nickel plating layer is provided as a barrier plating layer on the base, the thickness of the nickel plating layer possessed by the side surface of the lead frame base material is preferably 0.3 μm or more and 3.0 μm or less. In detail, it is good that a nickel plating layer having a thickness of 0.3 μm or more and 3.0 μm or less, preferably 1.0 μm, is formed on the surface of the side surface of the lead frame base material, and a roughened silver plating layer having a needle-like protrusion group on the surface having a thickness of 0.2 μm or more and 3.0 μm or less, preferably 0.5 μm, is laminated thereon.

[0059] In the case where a palladium plating layer is provided between the base nickel plating layer and the roughened silver plating layer, the thickness of the palladium plating layer is preferably 0.005 μm or more and 0.1 μm or less. In detail, it is good that a palladium plating layer having a thickness of 0.005 μm or more and 0.1 μm or less, preferably 0.01 μm, is formed on the nickel plating layer formed on the surface of the side surface of the lead frame base material.

[0060] In the case where a gold plating layer is provided between the base nickel plating layer and the palladium plating layer and the roughened silver plating layer, the thickness of the gold plating layer is preferably 0.0005 μm or more and 0.01 μm or less. In detail, it is good that a gold plating layer having a thickness of 0.0005 μm or more and 0.01 μm or less, preferably 0.001 μm, is formed on the nickel plating layer and the palladium plating layer formed on the surface of the side surface of the lead frame base material.

[0061] Note that in the lead frame of the present application, the roughened silver plating layer having a needle-shaped protrusion group, which has a crystal structure having the highest ratio of crystal orientation <101> among the respective ratios of crystal orientations <001>, <111>, and <101>, can be formed by using a silver plating bath composed of a methanesulfonic acid-based silver plating solution having a silver concentration of 1.0 g / L or more and 10 g / L or less, at a temperature of 55°C or more and 65°C or less, and at a current density of 3 A / dm 2 20 A / dm 2 Electroplating is performed for 5 to 60 seconds.

[0062] Accordingly, the lead frame of the present application can provide a lead frame in which silver plating is applied to the side surface of the upper surface, side surface, and lower surface of the lead frame substrate as the most surface layer plating, and the cost, operation time, and productivity for forming the roughened surface of the surface can be reduced, the thickness of the entire plating layer including the silver plating layer can be made thin, and the adhesion to the sealing resin can be significantly improved.

[0063] The lead frame of the present application and the method for manufacturing the same will be described below. Note that the present application is not limited by the following detailed description unless otherwise specified.

[0064] First Embodiment

[0065] Figure 1 FIG. (a) is a top view, FIG. (b) is a bottom view, and FIG. (c) is an explanatory view schematically showing the A-A cross section of FIG. (a) to show an example of the lead frame related to the first embodiment of the present application. Figure 2 FIG. is a plan view to show an example of the lead frame arranged in multiple columns related to the first embodiment of the present application. Figure 3 FIG. is an explanatory view to show an example and other examples of the manufacturing steps of the lead frame for mounting a semiconductor element related to the first embodiment of the present application. Figure 4 FIG. is an explanatory view to show an example and other examples of the manufacturing steps of the semiconductor package using the lead frame for mounting a semiconductor element related to the first embodiment of the present application.

[0066] As shown in FIG. (a), the lead frame 1 of the present embodiment has a plurality of terminals extending from the four sides to a region on which a semiconductor element is mounted, as shown in FIG. (c). Figure 1 As shown in FIG. (c), the upper surface, side surface, and lower surface of the lead frame substrate 10 composed of a copper-based material have a roughened silver plating layer 11 as the most surface layer plating on the side surface. Figure 1 In the present embodiment, 10a is an internal connection terminal portion electrically connected to a semiconductor element, and 10b is an external connection terminal portion. Figure 1

[0067] ​The roughened silver plating 11 has a group of needle-like protrusions with a surface area ratio (here, the ratio of the surface area of ​​the roughened silver plating to the surface area of ​​the smooth surface) of 1.30 to 6.00 or less.

[0068] Furthermore, the roughened silver plating 11 has a crystal orientation <001> , <111> , <101> Crystal orientation in their respective ratios <101> The crystal structure with the highest ratio.

[0069] The roughened silver coating 11 has an average crystal grain size of less than 0.28 μm.

[0070] Furthermore, in this embodiment, the roughened silver plating layer 11 is formed with a thickness of 0.2 μm to 3.0 μm based on a lead frame substrate 10 made of copper-based material.

[0071] It should be noted that, as a variation of this embodiment, a base plating layer that functions as a barrier plating layer to prevent copper diffusion at high temperatures may be provided between the lead frame substrate 10 made of copper-based material and the roughened silver plating layer 11. This base plating layer can be formed by any one of nickel plating, nickel / palladium plating, or nickel / palladium / gold plating. In this case, the roughened silver plating layer 11 can be formed with a thickness of 0.2 μm to 3.0 μm.

[0072] In detail, for example, the base plating functions as a barrier plating that prevents the diffusion of copper when making electrical connections with semiconductor elements using solder. When the base plating is composed of a plating made of nickel / palladium or a plating made of nickel / palladium / gold, the roughened silver plating 11 can be formed with a thickness of 0.2 μm or more and 3.0 μm or less.

[0073] Furthermore, in this embodiment, the lead frame 1 has an internal connection plating layer 12 on the upper surface of the lead frame substrate 10 corresponding to the internal connection terminal portion 10a, and an external connection plating layer 13 on the lower surface of the lead frame substrate 10.

[0074] The internal connection plating layer 12 and the external connection plating layer 13 are composed of plating layers made of nickel, palladium and gold stacked in sequence, respectively.

[0075] Furthermore, in the lead frame 1 of this embodiment, as follows: Figure 2 As shown, each lead frame 1 is arranged in multiple columns.

[0076] Next, use Figure 3 An example and other examples of the manufacturing process of the lead frame 1 in this embodiment will be described.

[0077] First, prepare a metal plate 10 made of copper-based material as the lead frame substrate (refer to...). Figure 3 (a)

[0078] Next, a resist layer Rl is formed on both surfaces of the metal plate 10 (refer to Figure 3 (b) ).

[0079] Next, the first resist layer Rl on the upper surface side of the metal plate 10 is exposed and developed using a glass mask on which a prescribed shape corresponding to the internal connection terminal portion 10a is drawn, and at the same time, the first resist layer Rl on the lower surface side of the metal plate 10 is exposed and developed using a glass mask on which a prescribed shape corresponding to the external connection terminal portion 10b is drawn, to form a first plating resist mask 31-1 which is opened at a portion corresponding to the internal connection terminal portion 10a on the upper surface side of the metal plate 10 and at the same time is opened at a portion corresponding to the external connection terminal portion 10b on the lower surface side of the metal plate 10 (refer to Figure 3 (c) ).

[0080] Next, using the first plating resist mask 31-1, a plating layer 12 for internal connection and a plating layer 13 for external connection are formed by, for example, sequentially laminating a nickel plating layer having a thickness of 0.3 to 3 μm, a palladium plating layer having a thickness of 0.005 to 0.1 μm, and a gold plating layer having a thickness of 0.0005 to 0.1 μm, at portions corresponding to the internal connection terminal portion 10a on the upper surface and at portions corresponding to the external connection terminal portion 10b on the lower surface of the metal plate 10, respectively (refer to Figure 3 (d) ).

[0081] Next, the first plating resist mask 31-1 is removed (refer to Figure 3 (e) ), and a second resist layer R2 is formed on both surfaces of the metal plate 10 (refer to Figure 3 (f) ).

[0082] Next, exposure and development are performed using a glass mask on which a prescribed lead frame shape is drawn, to form a resist mask 32 for etching (refer to Figure 3 (g) ).

[0083] Next, etching processing is performed on both surfaces to form a prescribed lead frame shape (refer to Figure 3 (h) ).

[0084] Next, using the resist mask 32 for etching on both surfaces of the metal plate 10 as a second plating resist mask, a roughened silver plating layer 11 having a group of needle-like projections is formed as a topmost plating layer on the side surface of the metal plate 10 (refer to Figure 3 (i) ).

[0085] Next, the resist mask 32 is removed (refer to Figure 3 (j) ).

[0086] Thus, the lead frame 1 of the present embodiment is completed.

[0087] Note that, by the above Figure 3 (a) to Figure 3 (j) to manufacture the lead frame 1 having the roughened silver plating layer 11 of the needle-like protrusion group only on the side surface of the lead frame base material 10, but the lead frame 1 of the present embodiment can be formed further on the upper surface of the lead frame base material 10 except for the inner connection terminal portion 10a.

[0088] Such a lead frame 1 can be manufactured by the following steps.

[0089] From the preparation of the metal plate 10 (refer to (a) of Figure 3 to the formation of the 2nd resist layer R2 on both surfaces of the metal plate 10 (refer to (f) of Figure 3 , the above manufacturing steps are the same.

[0090] Next, among the glass masks that depict both surfaces of the prescribed lead frame shape, as the glass mask on the upper surface side of the metal plate 10, a glass mask that depicts the prescribed lead frame shape in a manner in which the concentration of the light-shielding material that covers the portion of the upper surface of the lead frame base material 10 other than the inner connection terminal portion 10a is denser than the concentration of the light-shielding material that covers the portion of the lead frame base material 10 corresponding to the inner connection terminal portion 10a is used, and, as the glass mask on the lower surface side of the metal plate 10, a glass mask that depicts the prescribed lead frame shape in a manner in which the concentration of the light-shielding material that covers the portion corresponding to the outer connection terminal portion 10b is the same as the concentration of the light-shielding material that covers the portion of the upper surface of the lead frame base material 10 corresponding to the inner connection terminal portion 10a in the glass mask on the upper surface side of the metal plate 10 is used, exposure and development are performed, and an etching resist mask 32 is formed (refer to (g) of Figure 3 . At this time, in the etching resist mask 32 formed on the upper surface of the metal plate 10, the portion of the upper surface of the lead frame base material 10 other than the inner connection terminal portion 10a has a lower exposure amount than the portion corresponding to the inner connection terminal portion 10a, and has fast peeling properties with respect to the resist peeling liquid.

[0091] Next, etching processing is performed on both surfaces, and a prescribed lead frame shape is formed (refer to (h) of Figure 3 .

[0092] Next, the etching resist mask 32 on both surfaces of the metal plate 10 is removed, and the etching resist mask 32 on the upper surface side of the metal plate 10 is removed from the portion of the lead frame base 10 upper surface corresponding to the portion other than the internal connection terminal portion 10a, and the etching resist mask 32 on the lower surface side is not removed (see Figure 4 (h2) of FIG. 6).

[0093] Next, the etching resist mask 32 on both surfaces of the metal plate 10 is used as a second electroplating resist mask, and a roughened silver plating layer 11 having a needle-shaped protrusion group is formed as the outermost plating layer on the portion of the metal plate 10 upper surface other than the internal connection terminal portion 10a and the side surface (see Figure 3 (i') of FIG. 7).

[0094] Next, the etching resist mask 32 is removed (see Figure 3 (j') of FIG. 8).

[0095] Thus, the other example of the lead frame 1 of the present embodiment is completed, in which the roughened silver plating layer 11 having a needle-shaped protrusion group is formed on the portion of the lead frame base 10 upper surface other than the internal connection terminal portion 10a in addition to the side surface of the lead frame base 10.

[0096] Note that the formation step of the roughened silver plating layer 11 having a needle-shaped protrusion group as the outermost plating layer is, for example, to form the roughened silver plating layer by performing an activation treatment on the surface of the lead frame base 10, or to form a nickel plating layer as a barrier plating layer, for example, thinly and smoothly to a thickness that can suppress the diffusion of the copper of the substrate, and to form the roughened silver plating layer 11 thereon. At this time, in the case where the adhesion of the roughened silver plating layer 11 is a concern, a silver strike plating layer, for example, can be formed immediately before the roughened silver plating, and the roughened silver plating layer 11 can be formed thereon.

[0097] At this time, in order to form the roughened silver plating layer 11 having a needle-shaped protrusion group having a crystal structure in which the ratio of the crystal orientation <101> is the highest among the ratios of the crystal orientations <001>, <111>, and <101>, and having a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of the smooth surface) of 1.30 or more and 6.00 or less, the silver concentration in a silver plating bath composed of a methanesulfonic acid-based silver plating solution is set to a range of 1.0 g / L or more and 10 g / L or less. In particular, it is more preferable to set the silver concentration to a range of 1.5 g / L or more and 5.0 g / L or less.

[0098] If the silver concentration is below 1.0 g / L, a sufficiently roughened silver coating cannot be formed, which is therefore undesirable. If the silver concentration is above 10 g / L, the formed roughened silver coating will have a smooth surface, making it impossible to obtain needle-like silver crystals, which is also undesirable.

[0099] Furthermore, by using a palladium or palladium alloy plating as an alternative to the silver impact plating used to improve the adhesion between the substrate and the roughened silver plating 11, it is also possible to properly bond the substrate to the roughened silver plating 11.

[0100] Furthermore, a gold or gold-containing alloy coating can also be formed under the roughened silver plating layer 11.

[0101] It should be noted that when the roughening silver plating layer 11 is formed directly on the lead frame substrate without a base plating layer, the thickness of the roughening silver plating layer 11 must be 0.2 μm or more, and can be set to 0.2 μm or more but less than 3.0 μm. From a cost perspective, it is more preferable to set it to 0.3 μm or more but less than 1.0 μm.

[0102] Furthermore, the base plating layer functions as a barrier to prevent the diffusion of copper when making electrical connections with semiconductor elements using solder. When the base plating layer is a plating layer composed of nickel / palladium plating or a plating layer composed of nickel / palladium / gold plating, the thickness of the roughened silver plating layer 11 can be set to 0.2 μm or more and 3.0 μm or less.

[0103] Next, use Figure 4 An example of the manufacturing process of a semiconductor package using the lead frame 1 of this embodiment will be described.

[0104] First, prepare to pass Figure 4 (a)~ Figure 4 The lead frame 1 of this embodiment, manufactured according to the manufacturing steps shown in (j), is as follows (refer to...). Figure 4 (a)

[0105] Next, solder 14 is printed on the internal connection terminal portion 10a on the upper surface of the lead frame 1, and a semiconductor element 20 is mounted and fixed thereon, thereby electrically connecting the electrodes of the semiconductor element 20 to the internal connection terminal portion 10a of the lead frame 1 (see reference). Figure 4 (b)

[0106] Next, using a mold, the space area outside the external connection terminal portion 10b on the lower surface of the lead frame 1 is sealed with sealing resin 15 (see reference). Figure 3 (c)).

[0107] Finally, the semiconductor packages arranged in multiple rows are monolithically assembled through processes such as cutting and stamping (see reference). Figure 3(d).

[0108] The semiconductor package 2 using the lead frame 1 of the present embodiment is obtained by the same steps as described above (refer to Figure 3 (e).

[0109] Note that the semiconductor package 2 using the lead frame 1 of the other example of the present embodiment manufactured by the manufacturing steps shown in Figure 3 (a) to Figure 3 (h), Figure 4 (h2), Figure 4 (i'), Figure 5 (j') is also obtained by the same steps as described above (refer to Figure 6 (a') to Figure 7 (e').

[0110] 2nd Embodiment

[0111] Figure 8 (a) is a top view, (b) is a bottom view, and (c) is an explanatory diagram schematically showing a B-B cross section of (a). Figure 5 (a) is a top view, (b) is a bottom view, and (c) is an explanatory diagram schematically showing a B-B cross section of (a). Figure 5 (a) is a top view, (b) is a bottom view, and (c) is an explanatory diagram schematically showing a B-B cross section of (a). Figure 5 (a) is a top view, (b) is a bottom view, and (c) is an explanatory diagram schematically showing a B-B cross section of (a).

[0112] As shown in (a) of Figure 6 (a), the lead frame 1' of the present embodiment has a pad portion 10c on which a semiconductor element is mounted and a plurality of terminals extending from four sides toward the pad portion 10c, as shown in Figure 7 (c), the upper surface, the side surface, and the lower surface of the lead frame base material 10 composed of a copper-based material have a roughened silver plating layer 11 as the outermost plating layer on the side surface. Figure 3 In the drawing, 10a is an internal connection terminal portion to be electrically connected to a semiconductor element, and 10b is an external connection terminal portion.

[0113] The roughened silver plating layer 11 has a group of needle-shaped protrusions having a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of a smooth surface) of 1.30 or more and 6.00 or less.

[0114] Further, the roughened silver plating layer 11 has a crystal structure in which the ratio of the crystal orientation <101> is the highest among the ratios of the crystal orientations <001>, <111>, and <101>.

[0115] The average crystal grain size of the roughened silver plating layer 11 has a size of less than 0.28 μm.

[0116] Further, in the present embodiment, the roughened silver plating layer 11 is formed to a thickness of 0.2 μm or more and 3.0 μm or less on the lead frame base material 10 composed of a copper-based material.

[0117] Note that, as a modification of the present embodiment, a base plating layer that functions as a barrier plating layer that prevents diffusion of copper at high temperatures can be provided between the lead frame base material 10 composed of a copper-based material and the roughened silver plating layer 11. The base plating layer at this time can be composed of a plating layer formed by any one of nickel plating, nickel / palladium plating, and nickel / palladium / gold plating. In this case, the roughened silver plating layer 11 can be formed to a thickness of 0.2 μm or more and 3.0 μm or less.

[0118] In detail, for example, the base plating layer functions as a barrier plating layer that prevents diffusion of copper in the case of electrical connection to a semiconductor element by a wire bonding method, and when the base plating layer is composed of a plating layer including nickel plating, the roughened silver plating layer 11 can be formed to a thickness of 0.2 μm or more and 3.0 μm or less.

[0119] Further, for example, the base plating layer functions as a barrier plating layer that prevents diffusion of copper in the case of electrical connection to a semiconductor element by a wire bonding method, and when the base plating layer is composed of a plating layer including nickel / palladium plating, the roughened silver plating layer 11 can be formed to a thickness of 0.2 μm or more and 3.0 μm or less.

[0120] Further, the lead frame 1' of the present embodiment is provided with an internal connection plating layer 12 in a portion corresponding to the internal connection terminal portion 10a in the upper surface of the lead frame base material 10 and an external connection plating layer 13 in the lower surface of the lead frame base material 10.

[0121] The internal connection plating layer 12 and the external connection plating layer 13 are each composed of a plating layer in which nickel, palladium, and gold are sequentially stacked.

[0122] Further, in the lead frame 1' of the present embodiment, as shown in FIG. 1, the plurality of lead frames 1' are arranged in a plurality of columns. Figure 7

[0123] Next, an example of a manufacturing process of the lead frame 1' of the present embodiment will be described. Figure 7

[0124] The manufacturing process of the lead frame 1' of the present embodiment is the same as that of the lead frame 1 of the first embodiment. Figure 7 ​​The manufacturing process of the lead frame 1 of the first embodiment is substantially the same as that of the first embodiment, and the formation step of the roughened silver plating layer 11 having the needle-shaped protrusion group as the outermost layer plating layer is also substantially the same as that of the lead frame 1 of the first embodiment (see Figure 7 (a) to Figure 7 (j) of FIG. 1, (b) to Figure 7 (a) to Figure 7 (h) of FIG. 1, Figure 8 (h2) of FIG. 1, Figure 7 (i') of FIG. 1, Figure 8 (j') of FIG. 1).

[0125] Note that, in the case where the base plating layer is not provided and is directly formed on the lead frame base material, the thickness of the roughened silver plating layer 11 must be 0.2 μm or more, and can be set to 0.2 μm or more and 3.0 μm or less. Further, from the viewpoint of cost, it is more preferable to set to 0.3 μm or more and 1.0 μm or less.

[0126] Further, the base plating layer functions as a barrier that prevents the diffusion of copper in the case of electrically connecting with the semiconductor element by the wire bonding method, and when the nickel plating layer is provided as the base plating layer, the thickness of the roughened silver plating layer 11 can be set to 0.2 μm or more and 3.0 μm or less.

[0127] Further, the base plating layer functions as a barrier that prevents the diffusion of copper in the case of electrically connecting with the semiconductor element by the wire bonding method, and when the plating layer containing nickel / palladium plating is provided as the base plating layer, the thickness of the roughened silver plating layer 11 can be set to 0.2 μm or more and 3.0 μm or less.

[0128] Next, an example of the manufacturing process of the semiconductor package using the lead frame 1' of the present embodiment will be described using FIG. 1. Figure 8

[0129] First, the lead frame 1' of the present embodiment manufactured by the manufacturing steps shown in FIG. 1 is prepared (see (a) of FIG. 1). Figure 8 Figure 8

[0130] Next, the semiconductor element 20 is mounted and fixed on the gasket portion 10c of the upper surface of the lead frame 1' via the die bond 16, and at the same time, the electrodes of the semiconductor element 20 are electrically connected to the internal connection terminal portion 10a of the lead frame 1' by the bonding wire 17 (see (b) of FIG. 1). Figure 8

[0131] Next, using a mold, the space region of the lower surface of the lead frame 1' except for the external connection terminal portion 10b is sealed with the sealing resin 15 (see (c) of FIG. 1). Figure 7 ​​​​(c) of FIG. 1.

[0132] Finally, the semiconductor package 2' of the lead frame 1' of the present embodiment is obtained by singulating the semiconductor packages 2' arranged in multiple columns by cutting, punching, or the like (refer to Figure 7 (d) of FIG. 1.

[0133] Thus, the semiconductor package 2' of the lead frame 1' of the present embodiment is obtained by singulating the semiconductor packages 2' arranged in multiple columns by cutting, punching, or the like (refer to Figure 7 (e) of FIG. 1.

[0134] Note that the semiconductor package 2' of the lead frame 1' of the present embodiment manufactured using the manufacturing steps shown in Figure 7 (a) to Figure 7 (h) of FIG. 1, Figure 8 (h2) of FIG. 1, Figure 8 (i') of FIG. 1, Figure 3 (j') of FIG. 1 is also obtained by substantially the same steps as described above (refer to Figure 3 (a') to Figure 3 (e') of FIG. 1.

[0135] Example

[0136] (Example 1)

[0137] The lead frame of Example 1 is an example of a lead frame having no base plating layer, taking the lead frame base material 10 as a base, and forming a roughened silver plating layer 11 on the side surface of the lead frame base material 10.

[0138] In Example 1, a strip-shaped copper material having a thickness of 0.2 mm and a width of 180 mm was prepared as the lead frame base material 10 (refer to Figure 3 (a) of FIG. 1), a first resist layer R1 having a thickness of 25 μm was formed on both surfaces of the copper material (refer to Figure 3 (b) of FIG. 1), the first resist layer R1 on the upper surface side of the metal plate 10 was exposed and developed using a glass mask on which a prescribed shape corresponding to the internal connection terminal portion 10a was drawn, and at the same time, the first resist layer R1 on the lower surface side of the metal plate 10 was exposed and developed using a glass mask on which a prescribed shape corresponding to the external connection terminal portion 10b was drawn, thereby forming a first plating resist mask 31-1 which was open at a portion corresponding to the internal connection terminal portion 10a on the upper surface side of the metal plate 10 and at the same time was open at a portion corresponding to the external connection terminal portion 10b on the lower surface side of the metal plate 10 (refer to Figure 3 (c) of FIG. 1.

[0139] Next, using the first electroplating resist mask 31-1, a nickel plating layer of 1.0 μm in thickness, a palladium plating layer of 0.01 μm in thickness, and a gold plating layer of 0.001 μm in thickness are sequentially laminated in the portions of the upper surface of the metal plate 10 corresponding to the internal connection terminal portions 10a and in the portions of the lower surface of the metal plate 10 corresponding to the external connection terminal portions 10b, to form the internal connection plating layer 12 and the external connection plating layer 13 (see (d) of Figure 3 ).

[0140] Next, the first electroplating resist mask 31-1 is removed (see (e) of Figure 3 , and a second resist layer R2 is formed on both surfaces of the metal plate 10 (see (f) of Figure 3 ).

[0141] Next, exposure and development are performed using a glass mask on which a prescribed lead frame shape is drawn, to form an etching resist mask 32 (see (g) of Figure 3 ).

[0142] Next, etching processing is performed on both surfaces to form a prescribed lead frame shape (see (h) of Figure 3 ).

[0143] Next, using the etching resist mask 32 on both surfaces of the metal plate 10 as a second electroplating resist mask, the side surface of the metal plate 10 is subjected to pretreatment using an alkali and an acid, and then plating processing is performed as follows.

[0144] A silver plating bath composed of a methanesulfonic acid-based silver plating solution, with a silver concentration of 3.5 g / L, is used to perform plating at a temperature of 60°C and a current density of 5 A / dm 2 for 45 seconds, to form a roughened silver plating layer 11 having a needle-shaped protrusion group, a surface area ratio (here, the ratio of the surface area of the roughened silver plating layer to the surface area of a smooth surface), a ratio of crystal orientations <001>, <111>, <101>, and a crystal grain size (average value) of the values shown in Table 1, and a thickness of about 1.5 μm (see (i) of Figure 3 ).

[0145] Next, the resist mask 32 is removed (see (j) of Figure 7 , to thereby obtain the lead frame 1 of Example 1.

[0146] (Example 2)

[0147] The lead frame of Example 2 is an example of a lead frame in the case where electrical connection to a semiconductor element is performed by a wire bonding (gold wire or copper wire) method, in which a barrier plating layer of nickel is formed on the side surface of the lead frame base material 10 as a base to prevent thermal diffusion of copper present in the lead frame base material 10.

[0148] In Example 2, the formation of the lead frame shape (refer to...) Figure 7 (a)~ Figure 3 (h) Before the electroplating pretreatment of the sides of the metal plate 10, it is performed in roughly the same manner as in Example 1. For the subsequent electroplating treatment, firstly, a nickel plating bath composed of nickel sulfamate, nickel chloride, and boric acid is used at 2 A / dm³. 2 Electroplating was performed at a current density of 1 minute and 30 seconds to form a smooth nickel plating layer with a base thickness of approximately 1.0 μm. Next, a silver plating bath with a silver concentration of 3.5 g / L, composed of a methanesulfonic acid-based silver plating solution, was used at a temperature of 60°C and a current density of 5 A / dm³. 2 Electroplating is performed for 15 seconds to form a group of needle-like protrusions, with a surface area ratio (here, the ratio of the surface area of ​​the roughened silver plating to the surface area of ​​the smooth surface) and crystal orientation. <001> , <111> , <101> A roughened silver plating layer 11 with a thickness of approximately 0.5 μm and a ratio and crystal grain size (average) as shown in Table 1 was formed. Then, the resist mask 32 was removed in approximately the same manner as in Example 1 (see [reference]). Figure 3 (j)) to obtain the lead frame 1' of Example 2.

[0149] (Example 3)

[0150] Example 3 is an example of a lead frame with the following structure: Similar to the lead frame of Example 2, when the electrical connection to the semiconductor element is made by wire bonding (gold wire or copper wire), a nickel plating layer and a palladium plating layer are stacked on the side of the lead frame substrate 10 as a barrier plating layer to prevent thermal diffusion of copper present in the lead frame substrate 10.

[0151] In Example 3, the electroplating process on the sides of the metal plate 10, prior to forming a nickel plating layer, was performed in essentially the same manner as in Example 2. Next, a palladium plating bath composed of a dichloroamine-based palladium plating solution was used at a current density of 2 A / dm³. 2 Electroplating was performed for 10 seconds to form a smooth palladium plating layer as a substrate with a thickness of approximately 0.01 μm. Next, a silver plating bath with a silver concentration of 3.5 g / L, composed of a methanesulfonic acid-based silver plating solution, was used at a current density of 5 A / dm³. 2 Electroplating is performed for 15 seconds to form a group of needle-like protrusions, with a surface area ratio (here, the ratio of the surface area of ​​the roughened silver plating to the surface area of ​​the smooth surface) and crystal orientation. <001> , <111> , <101> A roughened silver plating layer 11 with a thickness of approximately 0.6 μm and a ratio and crystal grain size (average) as shown in Table 1 was formed. Then, the resist mask 32 was removed in approximately the same manner as in Example 1 (see...). Figure 3 (j)) to obtain the lead frame 1' of Example 3.

[0152] (Example 4)

[0153] The lead frame of Example 4 is an example of a lead frame in which, in the case of electrically connecting a semiconductor element by soldering, silver is made to easily diffuse to the solder by forming a silver plating layer as a barrier plating layer on the side surface of the lead frame base material 10.

[0154] In Example 4, the formation of the lead frame shape (see Figure 3 (a) to (h) of FIG. 1) and the pretreatment for the electroplating of the side surface of the metal plate 10 were performed substantially similarly to Example 1. In the electroplating treatment thereafter, a silver plating bath composed of a cyanide-based silver plating solution was used, and electroplating was performed at a current density of 3 A / dm2for 60 seconds at a temperature of 60°C to form a smooth silver plating layer as a barrier plating layer having a thickness of about 1.1 μm. 2 In Example 4, the formation of the lead frame shape (see ​ (a) to (h) of FIG. 1) and the pretreatment for the electroplating of the side surface of the metal plate 10 were performed substantially similarly to Example 1. In the electroplating treatment thereafter, a silver plating bath composed of a cyanide-based silver plating solution was used, and electroplating was performed at a current density of 3 A / dm2for 60 seconds at a temperature of 60°C to form a smooth silver plating layer as a barrier plating layer having a thickness of about 1.1 μm. 2 In Example 4, the formation of the lead frame shape (see ​ (a) to (h) of FIG. 1) and the pretreatment for the electroplating of the side surface of the metal plate 10 were performed substantially similarly to Example 1. In the electroplating treatment thereafter, a silver plating bath composed of a cyanide-based silver plating solution was used, and electroplating was performed at a current density of 3 A / dm2for 60 seconds at a temperature of 60°C to form a smooth silver plating layer as a barrier plating layer having a thickness of about 1.1 μm.

[0155] (Example 5)

[0156] The lead frame of Example 5 is an example of a lead frame in which, as in the lead frame of Example 4, in the case of electrically connecting a semiconductor element by soldering, a barrier plating layer as a barrier plating layer is formed by laminating a nickel plating layer, a palladium plating layer, and a gold plating layer on the side surface of the lead frame base material 10, and diffusion of copper present in the lead frame base material 10 is prevented.

[0157] In Example 5, the formation of the palladium plating layer in the electroplating treatment of the side surface of the metal plate 10 was performed substantially similarly to Example 3. Next, a gold plating bath composed of a cyanide-based gold plating solution was used, and electroplating was performed at a current density of 2 A / dm2for 10 seconds at a temperature of 60°C to form a smooth gold plating layer as a barrier plating layer having a thickness of about 0.001 μm. 2 In Example 4, the formation of the lead frame shape (see ​ (a) to (h) of FIG. 1) and the pretreatment for the electroplating of the side surface of the metal plate 10 were performed substantially similarly to Example 1. In the electroplating treatment thereafter, a silver plating bath composed of a cyanide-based silver plating solution was used, and electroplating was performed at a current density of 3 A / dm2for 60 seconds at a temperature of 60°C to form a smooth silver plating layer as a barrier plating layer having a thickness of about 1.1 μm. 2A silver plating layer 11 having a roughened surface with a protrusion group having a needle shape, a surface area ratio (here, a ratio of a surface area of the roughened silver plating layer to a surface area of a smooth surface) of 1.30, a ratio of crystal orientations <001>, <111>, <101> of 0.5, a crystal grain size (average) of 0.5 μm, and a thickness of about 0.5 μm was formed by electroplating for 15 seconds. Then, the resist mask 32 was removed substantially similarly to Example 1 (see (j) of FIG. 1), to obtain the lead frame 1 of Example 5. ​

[0158] (Comparative Example 1)

[0159] The lead frame of Comparative Example 1 is an example of a lead frame having no base plating layer, and a silver plating layer formed on the side surface of the lead frame substrate, which is smooth.

[0160] In Comparative Example 1, the formation of the lead frame shape and the electroplating pretreatment to the side surface of the metal plate were performed substantially similarly to Example 1. In the electroplating treatment thereafter, a silver plating bath composed of a cyan-based silver plating solution was used, and the silver concentration was 65 g / L, the current density was 3 A / dm2, and the plating time was 3 minutes. 2 A silver plating layer having a smooth surface and a thickness of about 2.5 μm was formed by electroplating for 3 minutes. Then, the resist mask was removed substantially similarly to Example 1, to obtain the lead frame of Comparative Example 1.

[0161] (Comparative Example 2)

[0162] The lead frame of Comparative Example 2 is an example of a lead frame having a silver plating layer formed on the side surface of the lead frame substrate, which has a roughened surface composed of unevenness having a surface area ratio (here, a ratio of a surface area of the silver plating layer to a surface area of a smooth surface) of less than 1.30.

[0163] In Comparative Example 2, the formation of the lead frame shape and the electroplating pretreatment to the side surface of the metal plate were performed substantially similarly to Example 1. In the electroplating treatment thereafter, a silver plating bath composed of a cyan-based silver plating solution was used, and the silver concentration was 65 g / L, the current density was 3 A / dm2, and the plating time was 6 minutes. 2 A silver plating layer having a smooth surface and a thickness of about 5.0 μm was formed by electroplating for 6 minutes. Next, a microetching treatment was performed on the surface of the silver plating layer by using a silver plating stripping solution for 2 minutes, to form a roughened surface having unevenness on the surface of the silver plating layer. At this time, the thickness of the silver plating layer having the roughened surface with unevenness on the surface was 2.8 μm, and the thickness was about half of the silver plating layer having a smooth surface. Then, the resist mask was removed substantially similarly to Example 1, to obtain the lead frame of Comparative Example 2.

[0164] (Comparative Example 3)

[0165] ​The lead frame of Comparative Example 3 is an example of a lead frame in which a base plating layer having a roughened surface on the surface is formed on the side surface of the lead frame substrate, and a silver plating layer is formed thereon.

[0166] In Comparative Example 3, the formation of the lead frame shape and the electroplating pretreatment for the side surface of the metal plate were performed substantially similarly to those of Example 1. In the electroplating treatment thereafter, first, a nickel plating bath composed of nickel sulfamate and nickel chloride, boric acid was used to form a nickel plating layer having a smooth surface at a current density of 2 A / dm2for 7 minutes and 30 seconds. Next, a surface of the nickel plating layer was subjected to a microetching treatment for 2 minutes by using a nickel plating stripping solution to form a roughened surface having unevenness on the surface of the nickel plating layer. At this time, the thickness of the nickel plating layer having the roughened surface with unevenness on the surface was 2.6 μm, which was about half of the thickness of the nickel plating layer having a smooth surface. Next, a silver plating bath composed of a cyanide-based silver plating solution at a silver concentration of 65 g / L was used to form a silver plating layer having a roughened surface with unevenness at a thickness of about 1.5 μm, a surface area ratio (here, a ratio of the surface area of the silver plating layer to the surface area of the smooth surface), a ratio of crystal orientations <001>, <111>, <101>, and a crystal grain size (average) shown in Table 1, following the shape of the roughened surface of the nickel plating layer. Then, the resist mask on the lower surface side of the metal plate was removed substantially similarly to Example 1 to obtain the lead frame of Comparative Example 3. 2 2

[0167] The plating layer constituent elements (the type and thickness of the plating layer, the surface area ratio (here, a ratio of the surface area of the (rough or smooth) silver plating layer to the surface area of the smooth surface), the ratio of the crystal orientation of the silver plating layer, and the crystal grain size (average)) of the lead frames of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0168] Note that the ratio of the crystal orientation was calculated by setting the allowable angle for each of the <001>, <111>, and <101> orientations to 15°, using an electron backscatter diffraction analysis device (ESBD) for a field of view observed at 10,000 times using a scanning electron microscope (SEM). Further, the crystal grain size was set to the area circle equivalent diameter of the crystal grain calculated by taking the orientation difference of 15° or more as a grain boundary.

[0169] Further, the plating thickness of the silver plating layer was measured using a fluorescent X-ray analysis device (SFT3300 manufactured by SII), and the plating thickness of the nickel, palladium, and gold plating layers was measured using a fluorescent X-ray analysis device (SFT3300 manufactured by SII).​​

[0170] Further, the surface area ratio was measured with a 3D laser microscope (OLYMPUS OLS4100).

[0171] [Table 1]

[0172]

[0173] Evaluation of resin adhesion

[0174] On the roughened silver plating layer of each of the lead frames of Examples 1 to 5 and Comparative Examples 1 to 3 (the smooth silver plating layer in Comparative Example 1), a cylindrical resin mold of Φ 2 mm for evaluation was formed. For the resin, the shear strength was measured using a Dage Series 4000 (manufactured by Dage) as a bonding tester, and thus the resin adhesion was evaluated.

[0175] The results of the evaluation of the resin adhesion of each of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0176] [Table 2]

[0177]

[0178] With regard to the lead frame of Comparative Example 1, it was confirmed that the shear strength was 10 MPa, and it could not be said that the resin adhesion was sufficient for practical use.

[0179] With regard to the lead frames of Examples 1 to 5, it was confirmed that each had a shear strength that was 1.5 times the shear strength of the lead frame of Comparative Example 1, as shown in Table 1, and the resin adhesion was significantly improved.

[0180] On the other hand, with regard to the lead frames of Comparative Examples 2 and 3, it was confirmed that, although the shear strength was higher than that of the lead frame of Comparative Example 1, the resin adhesion was improved, but the shear strength was only 1.1 times that of the lead frame of Comparative Example 1, and a significant improvement in the resin adhesion as with the lead frames of Examples 1 to 5 could not be obtained.

[0181] Evaluation of productivity

[0182] The processing time and silver plating amount required to form the surface morphology of the surface layer plating layer of each of the lead frames of Examples 1 to 5 and Comparative Examples 2 and 3 into a morphology having a roughened surface were compared, and the productivity was evaluated. When evaluating the productivity, the relative values of the processing time and silver plating amount used in the lead frame of Comparative Example 1, in which a smooth silver plating layer was formed as the surface layer plating layer, were set to 100, respectively, and the relative values were used as evaluation values. Note that the plating processing of the lead frame was performed in a state in which the lead frame was conveyed on a production line, and thus the evaluation values of the processing time were calculated based on the time required to form the metal plating layer that required the longest plating time in the plating processing of the lead frames of each of the examples and comparative examples (Example 1: roughened silver plating, Examples 2, 3, and 5: smooth nickel plating, Example 4: smooth silver plating, Comparative Example 2: smooth silver plating, Comparative Example 3: smooth nickel plating).

[0183] The evaluation results of the productivity (processing time and silver plating amount required to form the surface morphology of the surface layer plating layer into a morphology having a roughened surface) of each of Examples 1 to 5 and Comparative Examples 2 and 3 are shown in Table 2.

[0184] The lead frame of Comparative Example 2 is an example in which a roughened surface having unevenness was formed on the surface of a silver plating layer having a smooth surface and a thickness of about 5.0 μm by performing micro-etching processing using a silver plating stripping solution after forming the silver plating layer. The thickness of the silver plating layer having the roughened surface with unevenness on the surface was 2.8 μm, which was about half the thickness of the silver plating layer having a smooth surface. As shown in Table 2, the processing time was 200 and the silver usage amount was 200, and in addition to the increase in the processing time, the cost of the expensive silver greatly increased, and the productivity deteriorated.

[0185] The lead frame of Comparative Example 3 is an example in which a roughened surface having unevenness was formed on the surface of a nickel plating layer having a smooth surface and a thickness of about 5.0 μm by performing micro-etching processing using a nickel plating stripping solution after forming the nickel plating layer. The thickness of the nickel plating layer having the roughened surface with unevenness on the surface was 2.6 μm, which was about half the thickness of the nickel plating layer having a smooth surface. As shown in Table 2, the processing time was 250 and the silver usage amount was 60, and although the cost of the silver was reduced to some extent, the processing time greatly increased, and the productivity greatly deteriorated.

[0186] In contrast, the lead frames of Examples 1 to 5 were confirmed to have a processing time of 25 to 50 and a silver usage amount of 20 to 60, as shown in Table 2, and the processing time was reduced by 75 to 87.5% and the silver usage amount was reduced by 70 to 90% compared to the lead frame of Comparative Example 2, and thus the productivity was significantly improved.

[0187] Further, as to the lead frames of Examples 2, 3, and 5, it was confirmed that the processing time was reduced by 80% and the silver usage was reduced by 67% as compared with the lead frame of Comparative Example 3, and the productivity was significantly improved. Note that, as to the lead frames of Example 1 and Example 4, it was confirmed that, although the silver usage was equivalent to that of the lead frame of Comparative Example 3, it was significantly reduced as compared with the lead frame of Comparative Example 2, and further, the processing time was reduced by 88 to 90% as compared with the lead frame of Comparative Example 3, and the productivity was significantly improved.

[0188] The preferred embodiments and examples of the present application are described in detail above, but the present application is not limited to the above-described embodiments and examples, and various modifications and substitutions can be made to the above-described embodiments and examples without departing from the scope of the present application.

[0189] Further, although the material of the lead frame substrate in the lead frame of the present application is a copper-based material such as a copper alloy, a nickel-based alloy can also be applied as the material of the lead frame substrate.

[0190] Further, as long as the prescribed thickness of the surface area ratio and the crystal structure of the roughened surface of the group of needle-shaped protrusions is not impaired, in the lead frame of the present application, a silver plating layer, a plating layer composed of nickel, palladium, and gold, or the like can be further layered as a plating layer for covering on the roughened silver plating layer having a group of needle-shaped protrusions provided as the outermost layer plating layer.

[0191] Industrial applicability

[0192] The lead frame of the present application is useful in a field in which a lead frame having a silver plating layer provided as the outermost layer is required to manufacture a resin-sealed semiconductor package.

Claims

1. A lead frame, characterized in that, The lead frame substrate, made of copper-based materials, has a top surface, side surface, and bottom surface with nickel, palladium, and gold layered sequentially on the top and bottom surfaces. Simultaneously, the side surface has a roughened silver plating layer with needle-like protrusions as the outermost plating layer. The needle-like protrusions in the roughened silver plating layer refer to an aggregate of multiple needle-like protrusions whose surface area to the smooth surface ratio is between 1.30 and 6.

00. This roughened silver plating layer has a crystal orientation... <001> , <111> , <101> Crystal orientation in their respective ratios <101> The crystal structure with the highest ratio; wherein a surface-roughened silver plating layer is formed without roughening the smooth silver plating surface, by using a silver plating bath composed of a methanesulfonic acid-based silver plating solution with a silver concentration of 1.0 g / L to 10 g / L, at a temperature of 55°C to 65°C and a current density of 3 A / dm³. 2 Above 20A / dm 2 The following is obtained by electroplating for 5-60 seconds.

2. The lead frame according to claim 1, characterized in that, The average crystal grain size of the roughened silver coating is less than 0.28 μm.

3. The lead frame according to claim 1 or 2, characterized in that, A base plating layer exists between the lead frame substrate and the roughened silver plating layer.

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