Lead frame

Abstract

A lead frame can maximize the opening area of ​​the side surface of a semiconductor package product while preventing deformation caused by reduced strength of the lead, the side surface being gate-shaped and allowing visual inspection of the welded portion. A first region of the lead formed of a copper-based metal plate has a thin-walled portion formed by a depression on one side that is 75 to 90% of the thickness of the metal plate, the first region includes a portion of a region to be an external connection terminal and straddles a boundary line of a cutting region for cutting into individual packages, a concave reinforcing plating layer is formed on the surface of the thin-walled portion with a thickness of 7.5% or more of the thickness of the metal plate, an external connection plating layer is formed on the surface of a second region including the first region where the reinforcing plating layer is formed, and the surface of the external connection plating layer at the concave bottom position of the boundary line of the cutting region of the lead is located at a position that is approximately 50% or more of the thickness of the metal plate from one side of the metal plate.

Description

Technical Field

[0001] The present invention relates to a lead frame for manufacturing a semiconductor package of a type in which external connection terminals on the back side are connected to external devices such as a printed circuit board. Background Art

[0002] When assembling a semiconductor package to an external device, it is required to visualize the soldered portion so that it is possible to visually check whether the soldering state between the semiconductor package and the external device is good or bad.

[0003] In the past, the structure of semiconductor packages such as QFN (Quad-Flat No-leaded) that do not have external leads on the periphery is that external connection terminals are arranged on the back side of the semiconductor package, and the multiple external connection terminals exposed on the back side of the semiconductor package are connected to external devices such as a printed circuit board, so it is difficult to visually check whether the two are soldered.

[0004] However, if the welded part cannot be visually inspected, the inherent poor connection cannot be found during the welding operation, and additional operation costs are required until the poor connection is found later during the power-on inspection, etc. In addition, the welded part can also be inspected using an X-ray device, but this will increase the equipment cost of the X-ray device.

[0005] Therefore, in the past, as a technology that can visually check whether the welding state of the welding part of the QFN type semiconductor package is good or bad, patent document 1 has proposed: a groove that crosses the lead is formed at the cutting position of the terminal part that will become the external connection terminal on one side (back side) of the lead of the lead frame, thereby providing a space portion extending to the edge portion at the external connection terminal exposed on the back side of the semiconductor package that has been cut one by one, and solder is placed in the space portion, so that the welding part can be visually checked from the external connection terminal exposed on the side of the semiconductor package.

[0006] In addition, patent document 2 discloses a technology in which a recess is provided on the inner side of a specified area, and after the front side is sealed with resin, a cutting process is performed at a position where the surface of the recess may be exposed, thereby making the side surface where the external connection terminal is exposed into a gate shape, so that the welding part can be visually viewed from the external connection terminal exposed on the side of the semiconductor package. The specified area includes the area of ​​one side surface (back side) of the lead frame that will become the external connection terminal of the lead, and straddles the boundary line of the cutting area.

[0007] Background Art Literature

[0008] Japanese Patent Laid-Open No. 2000-294715

[0009] Japanese Patent Publication No. 2018-200994 Summary of the invention

[0010] However, in the technique for forming a groove that crosses the lead described in Patent Document 1, resin enters the groove during resin sealing, so that a space portion that can be used for visually viewing the soldering portion cannot be formed, and the yield of the semiconductor package product may be reduced.

[0011] In this regard, although the technology described in Patent Document 2 that forms the side of the external connection terminal into a gate shape can provide a space portion through which the welding portion can be visually observed, in recent years, people have hoped to further expand the opening area of ​​the side formed into a gate shape so that the welding portion can be visually observed as easily as possible.

[0012] If the opening area of ​​the side surface of the external connection terminal that will be formed into a gate shape is increased as much as possible in a lead frame structure such as that described in Patent Document 2 in order to facilitate visual inspection of the welding portion, the lead will be locally thinned and thus lack strength, which may cause deformation during the assembly process of the semiconductor package.

[0013] The present invention is completed in view of the above-mentioned previous problems, and its purpose is to provide a lead frame that can maximize the opening area of ​​the side of the semiconductor packaging product while preventing deformation caused by reduced strength of the lead. The side is a part where the welding part can be visually seen and will be formed into a gate shape.

[0014] Means to solve the problem

[0015] In order to achieve the above-mentioned purpose, the lead frame of the present invention is used for a semiconductor package in which external connection terminals are exposed on one side of the surface and side surface, and has a first area of ​​a lead formed by a metal plate composed of a copper-based material, and has a thin-walled portion formed by a depression on one side that is 75 to 90% of the thickness of the metal plate, the first area includes a part of the area that will become the external connection terminal and straddles the boundary line of the cutting area for cutting into individual packages, and a concave reinforcing plating layer is formed on the surface of the thin-walled portion with a thickness of more than 7.5% of the thickness of the metal plate, and an external connection plating layer is formed on the surface of one side of the second area including the first area where the reinforcing plating layer is formed, and the surface of the external connection plating layer at the position of the concave bottom of the boundary line of the cutting area of ​​the lead is located at a position that is more than approximately 50% of the thickness of the metal plate from one side of the metal plate.

[0016] In the lead frame of the present invention, the reinforcing plating layer is preferably a plating layer containing nickel, and the thickness of the plating layer at the portion where the reinforcing plating layer and the external connection plating layer are stacked is at least 10% of the thickness of the metal plate. It is practicable that the thickness is in the range of about 5 to 55 μm.

[0017] In the lead frame of the present invention, it is preferable that the side surface of the lead has a portion where the reinforcing plating layer is exposed from the metal plate.

[0018] In the lead frame of the present invention, it is preferable that the reinforcing plating layer is exposed on the side surface of the lead at the position of the boundary line of the cutting region.

[0019] Effects of the Invention

[0020] According to the present invention, a lead frame can be obtained which can maximize the opening area of ​​the side surface of the semiconductor package product while preventing deformation caused by reduced strength of the lead. The side surface is a portion where the welding portion can be visually viewed and will be formed into a gate shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is an explanatory diagram showing the main part structure of the lead frame of the first embodiment of the present invention, and (a) is a diagram observed from one side (the side connected to the external device), (b) is a diagram observed from the opposite side of (a), (c) is an AA cross-sectional view of the area of ​​the lead frame of (a) that becomes the external connection terminal, (c') is a partial enlarged view of (c), (d) is a BB cross-sectional view of the area of ​​the lead frame of (a) that becomes the external connection terminal, (e) is a diagram showing a modified example observed from the side connected to the external device, and (f) is a CC cross-sectional view of (e).

[0022] Figure 2 So Figure 1 (a) AA cross section representation Figure 1 An explanatory diagram of an example of a manufacturing step of a lead frame.

[0023] Figure 3 So Figure 1 (a) BB cross section representation Figure 1 An explanatory diagram of an example of a manufacturing step of a lead frame.

[0024] Figure 4 It means to use according to Figure 2 and Figure 3 An explanatory diagram of an example of a manufacturing step of a lead frame package manufactured by the manufacturing steps of FIG.

[0025] Figure 5 It means that it will be Figure 4The state in which the external connection terminals of the semiconductor package manufactured by the manufacturing step are welded to the external device is from Figure 4 (e) Side view viewed from the same side. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0027] First Embodiment

[0028] like Figure 1 As shown, the lead frame 1 of the first embodiment has a thin-walled portion 11-1a in an area 11-1, and the area 11-1 includes a portion of an area that will become an external connection terminal on one side of the lead 11 formed of a metal plate composed of a copper-based material, and crosses a boundary line L of a cutting area for cutting into individual packages, and intersects with a blocking rod 13.

[0029] like Figure 1 (c) Figure 1 As shown in (c′), the thin-walled portion 11 - 1 a is formed by a depression on one surface side that is 75 to 90% of the thickness of the metal plate 10 .

[0030] Furthermore, a concave reinforcing plating layer 14 composed of a plating layer containing nickel is formed on the surface (inner surface) of the thin-walled portion 11 - 1 a , and the reinforcing plating layer 14 has a thickness of 7.5% or more of the plate thickness of the metal plate 10 .

[0031] In addition, the external connection plating layer 12 is formed on the surface of one side of the second region 11 - 2 including the first region 11 - 1 on which the reinforcing plating layer 14 is formed.

[0032] Furthermore, the thickness of the plating layer at the portion where the reinforcing plating layer 14 and the external connection plating layer 12 are laminated is 10% or more of the plate thickness of the metal plate 10 .

[0033] The surface of the external connection plating layer 12 at the concave bottom of the boundary line L of the cutting region of the lead 11 is located at a depth of approximately 50% or more of the thickness of the metal plate 10 from one surface of the metal plate 10 .

[0034] Furthermore, the external connection plating layer 12 is preferably composed of a plating layer in which nickel, palladium, and gold are stacked in this order.

[0035] In addition, if Figure 1 As shown in (d), the thin-walled portion 11-1a is Figure 1 (a) BB cross section is formed into a concave structure like a gate shape. In addition, Figure 1 (e) Figure 1As shown in FIG. 5( f ), the thin-walled portion 11 - 1 a may be formed only on the other side of the lead 11 , and the reinforcing plating layer 14 may be exposed on the side surface of the lead 11 .

[0036] Next, use Figure 2 , Figure 3 right Figure 1 An example of a process for producing the lead frame according to the present embodiment will be described.

[0037] First, prepare a copper-based metal plate 10 (see Figure 2 (a) Figure 3 (a)).

[0038] Next, the metal plate 10 is subjected to half etching to form the recessed portion 11 - 1 b .

[0039] Specifically, a first resist layer R1 (see FIG. 1 ) such as a dry film resist is formed on both surfaces of the metal plate 10. Figure 2 (b) Figure 3 (b)). Next, the entire surface of the first resist layer R1 on the other side of the metal plate 10 is exposed, and the first resist layer R1 on one side of the metal plate 10 is exposed and developed using a glass mask on which a predetermined pattern is drawn, thereby forming an etching-plating dual-purpose resist mask 31 having an opening at a portion corresponding to the thin-walled portion 11-1a and covering other portions (see Figure 2 (c) Figure 3 (c)). Next, a half-etching process is performed from one side of the metal plate 10 with an etching liquid to a depth of 75 to 90% of the thickness of the metal plate 10 to form a recessed portion 11-1b on one side of the metal plate 10 (see Figure 2 (d) Figure 3 (d)). The width of the inner surface of the recess 11-1b is formed to be 50 to 100% of the width of the lead 11 according to the width of the lead 11. If the width of the inner surface of the recess 11-1b is formed to be 100% (or more) of the width of the lead 11, the reinforcing plating layer can be exposed on the side of the lead 11 when the lead frame shape is formed in the subsequent process.

[0040] Next, a nickel or nickel alloy plating having a thickness of 7.5% or more of the thickness of the metal plate 10 is applied to the surface (inner surface) of the concave portion 11-1b from one side of the metal plate 10, thereby forming a concave reinforcement plating layer 14 (see Figure 2 (e), 3 (e)). Then, the etching-plating dual-purpose resist mask 31 formed on the metal plate 10 is removed (refer to Figure 2 (f) Figure 3 (f)).

[0041] Next, three steps for forming the internal connection plating layer and the external connection plating layer will be briefly described.

[0042] First, if the lead frame needs to have the same material for the internal connection plating layer and the external connection plating layer, plating is performed after forming a resist mask on both sides with openings for the portions where the plating layers are to be formed. For example, plating is performed in the order of nickel, palladium, and gold, and then the resist masks on both sides are removed.

[0043] In addition, if the lead frame needs to have the internal connection plating layer and the external connection plating layer as plating layers of different materials, a resist mask with an opening for forming the internal connection plating layer is formed on the other side, and a resist mask covering the entire surface is formed on one side, and then a plating process is performed, for example, silver plating is performed to form the internal connection plating layer, and then the resist masks on both sides are removed. Next, a resist mask covering the entire surface is formed on the other side, and a resist mask with an opening for forming the external connection plating layer is formed on one side, and then a plating process is performed, for example, plating is performed in the order of nickel, palladium, and gold, and then the resist masks on both sides are removed.

[0044] In addition, if a lead frame is required to have a plating layer for external connection without forming an internal connection plating layer, a resist mask covering the entire surface is formed on the other side, and a resist mask with an opening for forming a plating layer for external connection is formed on one side, and then plating is performed, for example, plating is performed in the order of nickel, palladium, and gold, and then the resist masks on both sides are removed.

[0045] Here, use Figure 2 , Figure 3 The step of forming the external connection plating layer will be described again.

[0046] A second resist layer R2 (see Figure 2 (g) Figure 3 (g)). Next, the entire surface of the second resist layer R2 on the other side is exposed, and the second resist layer R2 on one side is exposed and developed using a glass mask on which a predetermined pattern is drawn, thereby forming a plating resist mask 32 that opens a portion corresponding to the second region 11-2 of the lead 11 and covers other portions (see Figure 2 (h) Figure 3 (h)).

[0047] Next, the exposed portion from the plating resist mask 32 is plated with nickel, palladium, and gold in this order (see Figure 2 (i) Figure 3(i)) Thus, the external connection plating layer 12 is formed on one surface of the second region 11 - 2 including the first region where the concave reinforcing plating layer 14 is formed.

[0048] In addition, when forming the plating layer 12 for external connection, the plating thickness is adjusted in the following manner, that is, the surface of the plating layer 12 for external connection at the position of the concave bottom of the boundary line L of the said cutting area of ​​the lead 11 is located at a position that is approximately 50% or more of the thickness of the metal plate 10 from one side of the metal plate 10.

[0049] At this time, it is preferable that the total thickness of the reinforcing plating layer 14 and the external connection plating layer 12 is 10% or more of the plate thickness of the metal plate 10. It is practicable that the thickness is within a range of about 5 to 55 μm.

[0050] In addition, the surface of the external connection plating layer 12 may be formed into a rough surface. In the case of forming a rough surface, for example, the nickel plating layer of the external connection plating layer 12 may be formed by rough plating. In addition, for example, after forming a smooth nickel plating layer, the surface of the nickel plating layer may be formed into a rough surface by etching. Furthermore, a plating layer may be stacked in the order of palladium and gold on the nickel plating layer formed with a rough surface.

[0051] Then, the plating resist masks 32 on both sides are removed (see Figure 2 (j) Figure 3 (j)).

[0052] Next, the metal plate 10 is etched to form a lead frame shape.

[0053] Specifically, a third resist layer R3 (see FIG. 1 ) such as a dry film resist is formed on both surfaces of the metal plate 10. Figure 3 (k)). Next, the third resist layer R3 on the other side and the third resist layer R3 on the one side of the metal plate 10 are exposed and developed using a glass mask on which a predetermined pattern required for obtaining the lead frame shape is drawn, thereby forming an etching resist mask 33 on both sides of the metal plate 10 (see Figure 3 (l)).

[0054] Next, etching is performed on both sides of the metal plate 10 using an etching liquid to form a lead frame, which is a multi-row lead frame in which each lead frame region is connected to the blocking rod 13, and the cross-sectional shape of the terminal portion that becomes the external connection terminal when cut into each semiconductor package is formed into a gate shape (refer to Figure 3 (m)).

[0055] Next, the etching resist mask 33 (see Figure 3 (n)).

[0056] At this point, the lead frame 1 of the present embodiment is completed.

[0057] Furthermore, when the lead frame 1 is formed by etching, a half etching process may be performed on the middle portion of the lead or other necessary portions.

[0058] Next, use Figure 4 , Figure 5 A manufacturing process of a semiconductor package using the lead frame of the present embodiment will be briefly described.

[0059] A semiconductor element is mounted on the other surface of the lead frame of this embodiment, and electrodes of the semiconductor element and predetermined internal connection terminals are connected by wire bonding or flip-chip mounting (not shown).

[0060] Next, a sheet of masking tape m1 (see Figure 4 (a)), a mold (not shown) is placed, and the semiconductor element mounting side is sealed with resin 21 (refer to Figure 4 (b) At this time, one end surface of the concave portion formed by laminating the reinforcing plating layer 14 and the external connection plating layer 12 is in close contact with the masking tape m1, thereby forming an internally sealed state. Therefore, when the sealing resin is formed, the resin 21 does not penetrate into the interior of the concave portion formed by laminating the reinforcing plating layer 14 and the external connection plating layer 12.

[0061] Next, remove the masking tape m1 (see Figure 4 (c)), and cut the semiconductor package 40 into pieces according to the specified size (refer to Figure 4 (d) Figure 4 (d')). At this point, the semiconductor package 40 using the lead frame of this embodiment is completed (see Figure 4 (e)).

[0062] When the external connection terminals of the semiconductor package 40 using the lead frame 1 of the present embodiment are soldered to the terminals 81 of the printed circuit board 80, the soldered portion can be visually checked from the gate-shaped opening of the external connection terminals exposed on the side of the semiconductor package 40 while facing the solder 90, thereby making it possible to visually check whether the connection state is good or bad (see FIG. Figure 5 ).

[0063] According to the lead frame 1 of the present embodiment, when the semiconductor package is welded to the external device, the welded portion can be visually confirmed from the side, and by forming the reinforcing plating layer 14 with a thickness of 7.5% or more of the plate thickness of the metal plate 10, even if the gate-shaped opening area is formed larger (wider) than before, the strength of the lead 11 will not be reduced, thereby preventing the lead 11 from being deformed during the manufacturing process of the semiconductor package. In addition, when the cutting process is performed at the boundary line L of the cutting area by the blade, the cut surface that becomes the side of the semiconductor package has less copper material due to the increase in the gate-shaped opening area, so the burrs caused by the copper material on the external connection terminal exposed on the side of the semiconductor package, which would have been produced in the past, can be reduced.

[0064] In addition, when the width of the inner surface of the recess 11-1b formed by the half-etching process described above is formed to be the width of the lead 11 (100%), most of the side surface of the lead 11 in the cut surface that becomes the side surface of the semiconductor package becomes a reinforcing plating layer and a plating layer for external connection, and the copper-based material existing on the side surface is significantly reduced (the copper-based material exists only on the side surface on the other side), thereby further suppressing the generation of burrs caused by the copper-based material.

[0065] As a result, the productivity of the process of cutting and processing the semiconductor packages one by one using a blade can also be improved.

[0066] Example 1

[0067] First, a copper-based material having a thickness of 0.2 mm is prepared as a metal plate 10 (see Figure 2 (a) Figure 3 (a)), and a dry film resist is laminated on both sides as the first resist layer R1 (refer to Figure 2 (b) Figure 3 (b)).

[0068] Next, exposure and development are performed to form an etching-plating dual-purpose resist mask 31 covering the entire surface on the other side (front side), and a resist mask 31 is formed on one side (back side) in contact with the surface. Figure 1 The lead frame shown in FIG. 1 has an opening at a portion corresponding to the thin-walled portion 11-1a and covers other portions of the lead frame. The etching-plating dual-purpose resist mask 31 (see FIG. 1 ) Figure 2 (c) Figure 3 (c)).

[0069] Next, a half etching process is performed using an etching solution to form a recessed portion 11-1b on one side of the metal plate 10 (see Figure 2 (d) Figure 3(d)) The half-etching process conditions are set such that the recess 11-1b is at a depth of 85% of the thickness of the metal plate 10 and has a 20% width of copper-based material on both sides in the width direction of 60% of the width of the lead 11 (to be formed later).

[0070] After the concave portion 11-1b is formed on one side of the metal plate 10, the same etching-plating dual-purpose resist mask 31 is used for plating, and nickel plating with a set thickness of 19 μm is performed on (the inner surface of) the concave portion 11-1b to form a concave reinforcing plating layer 14 with an opening on one side (see Figure 2 (e) Figure 3 (e)).

[0071] Then, the etching-plating dual-purpose resist mask 31 on both sides is removed (see Figure 2 (f) Figure 3 (f)).

[0072] Next, a dry film resist is laminated on both surfaces of the copper-based metal plate 10 as a second resist layer R2 (see Figure 2 (g) Figure 3 (g)).

[0073] Then, a glass mask having a predetermined pattern is used for exposure and development, thereby forming a plating resist mask 32 on the other side with an opening corresponding to a region (not shown) to be an internal connection terminal and covering other regions, and forming a plating resist mask 32 on one side with an opening corresponding to a second region 11-2 including a first region 11-1 (see FIG. 1 ) where a concave reinforcement plating layer 14 is formed and covering other regions. Figure 2 (h) Figure 3 (h)).

[0074] Next, a plating process is performed, wherein nickel plating with a set thickness of 1 μm, palladium plating with a set thickness of 0.01 μm, and gold plating with a set thickness of 0.001 μm are sequentially performed, thereby forming an internal connection plating layer (not shown) on the surface of the region (not shown) of the lead 11 that will become the internal connection terminal, and forming an external connection plating layer 12 (see FIG. 1 ) on the surface of the second region 11-2. Figure 2 (i) Figure 3 (i)) The structure formed by this plating process is that the external connection plating layer 12 is stacked on the previously formed concave reinforcement plating layer 14.

[0075] Then, the resist masks 32 on both sides are removed (see Figure 2 (j) Figure 3 (j)).

[0076] Next, a dry film resist is laminated on both surfaces of the metal plate 10 as a third resist layer R3 (see Figure 3 (k)).

[0077] Next, exposure and development are performed to form an etching resist mask 33 on the other side, which covers the portion that will become the prescribed lead frame and the portion that will become the blocking rod, and exposes other portions. The portion that will become the prescribed lead frame includes the portion that will become the internal connection terminal and is formed by stacking nickel, palladium, and gold plating layers in sequence; and an etching resist mask 33 is formed on one side, which covers the portion that will become the prescribed lead frame and exposes other portions. The portion that will become the prescribed lead frame includes the portion that will become the external connection terminal and is formed by stacking nickel, palladium, and gold plating layers in sequence (see Figure 3 (l)).

[0078] Next, etching is performed to form a predetermined lead frame and a plugging rod shape (see Figure 3 (m)).

[0079] Then, the etching resist masks 33 on both sides are removed (see Figure 3 (n)).

[0080] In this way, a lead frame of Example 1 is obtained, which has internal connection terminals on the other side and external connection terminals on one side, and the portion of the boundary line L that spans the cutting area for cutting into individual packages of the lead 11 connected to the blocking rod 13 is formed by the metal plate 10, the reinforcing plating layer 14 and the external connection plating layer 12, and the inner side of the external connection plating layer 12 on one side is provided with a concave opening.

[0081] It was confirmed that the leads 11 having the concave openings in the obtained lead frame of Example 1 were not deformed.

[0082] Example 2

[0083] The process from preparation of the metal plate 10 to formation of the etching-plating dual-purpose resist mask 31 is carried out in substantially the same manner as in Example 1, the etching-plating dual-purpose resist mask 31 is opened in such a manner that the width of the inner surface of the recess 11-1b formed on one side of the metal plate 10 becomes the same as the width of the lead 11, and half-etching is performed at the same depth as in Example 1 to form the recess 11-1b on one side of the metal plate 10, and nickel plating with a set thickness of 15 μm is implemented to form a concave reinforcing plating layer 14 with an opening on one side.

[0084] By performing the subsequent steps in the same manner as in Example 1, a lead frame of Example 2 is obtained, which has internal connection terminals on the other side and external connection terminals on one side, and the portion of the lead 11 connected to the blocking rod 13 that spans the boundary line L of the cutting area for cutting into individual packages is formed by a metal plate 10, a reinforcing plating layer 14, and an external connection plating layer 12 in the same manner as in Example 1, and the metal plate 10 is exposed on the other side, the reinforcing plating layer 14 and the side of the metal plate 10 on the other side are exposed on the side, and the external connection plating layer 12 is exposed on one side.

[0085] It was confirmed that the leads 11 having the concave openings in the obtained lead frame of Example 2 were not deformed.

[0086] Comparative Example 1

[0087] The preparation of the metal plate 10 and the formation of the recessed portion 11 - 1 b on one side of the metal plate 10 were carried out in the same manner as in Example 2, and then nickel plating was performed with a set thickness of 11 μm to form a recessed reinforcing plating layer 14 with one side open.

[0088] By performing the subsequent steps in the same manner as in Example 2, a lead frame of Comparative Example 1 is obtained, which has internal connection terminals on the other side and external connection terminals on one side, and the portion of the lead 11 connected to the blocking rod 13 that spans the boundary line L of the cutting area for cutting into individual packages is formed by a metal plate 10, a reinforcing plating layer 14, and an external connection plating layer 12 in the same manner as in Example 1, and the metal plate 10 is exposed on the other side, the reinforcing plating layer 14 and the side of the metal plate 10 on the other side are exposed on the side, and the external connection plating layer 12 is exposed on one side.

[0089] In the obtained lead frame of Comparative Example 1, it was finally confirmed that the plurality of leads 11 having the concave openings were deformed, and therefore it was found that the strength was insufficient if the thickness of the reinforcing plating layer 14 was 5.5% of the metal plate 10 .

[0090] Comparative Example 2

[0091] The recess 11-1b is formed in substantially the same manner as in Example 1, but the conditions for the half-etching process are set as follows: the recess 11-1b is set to have a width of 70% of the width of the lead 11 (formed later) at a depth of 85% of the thickness of the metal plate 10, and a copper-based material of 15% width is provided on both sides of the width direction of the recess 11-1b.

[0092] Then, the etching-plating dual-purpose resist mask 31 is removed without forming the reinforcing plating layer 14 .

[0093] By performing the subsequent steps in the same manner as in Example 1, a lead frame of Comparative Example 2 is obtained, which has internal connection terminals on the other side and external connection terminals on one side, and the portion of the lead 11 connected to the blocking rod 13 that spans the boundary line L of the cutting area for cutting into individual packages is formed by a metal plate 10 and a plating layer 12 for external connection, and the metal plate 10 is exposed on the other side and the side surface, respectively, and the metal plate 10 and the plating layer 12 for external connection are exposed on one side.

[0094] It was finally confirmed that the plurality of leads 11 having the concave openings were deformed in the obtained lead frame of Comparative Example 2, and therefore the strength was found to be insufficient.

[0095] Comparative Example 3

[0096] After the recessed portion 11 - 1 b is formed in the same manner as in Example 1, the etching-plating dual-purpose resist mask 31 is removed without forming the reinforcing plating layer 14 .

[0097] By performing the subsequent steps in the same manner as in Example 1, a lead frame of Comparative Example 3 is obtained, which has internal connection terminals on the other side and external connection terminals on one side, and the portion of the boundary line L that spans the cutting area for cutting into individual packages of the lead 11 connected to the blocking rod 13 is formed by a metal plate 10 and a plating layer 12 for external connection, and the metal plate 10 is exposed on the other side and the side surface, respectively, and the metal plate 10 and the plating layer 12 for external connection are exposed on one side.

[0098] It was finally confirmed that the plurality of leads 11 having the concave openings were deformed in the obtained lead frame of Comparative Example 3, and therefore the strength was found to be insufficient.

Claims

1. A lead frame for a semiconductor package having external connection terminals exposed on one surface and side surfaces thereof, characterized in that: A first region of a lead formed of a metal plate made of a copper-based material has a thin-walled portion formed by a depression on one side that is 75 to 90% of the thickness of the metal plate, the first region including a portion of a region to be the external connection terminal and straddling a boundary line of a cutting region for cutting into individual packages, A concave reinforcing plating layer is formed on the surface of the thin-walled portion with a thickness of 7.5% or more of the plate thickness of the metal plate. An external connection plating layer is formed on a surface of one side of the second region including the first region where the reinforcing plating layer is formed, The surface of the external connection plating layer at the concave bottom position of the boundary line of the cutting region of the lead is located at a position deeper than 50% of the plate thickness of the metal plate from one surface side of the metal plate.

2. The lead frame according to claim 1, characterized in that: The reinforcing plating layer is a plating layer containing nickel, and The thickness of the plating layer at the portion where the reinforcing plating layer and the external connection plating layer are laminated is 10% or more of the plate thickness of the metal plate.

3. The lead frame according to claim 1, wherein: The side surface of the lead has a portion where the reinforcing plating layer is exposed from the metal plate.

4. The lead frame according to claim 1, wherein: The reinforcing plating layer is exposed on the side surface of the lead at the position of the boundary line of the cutting region.

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