Lead frame and semiconductor device using the same

Abstract

To provide a lead frame that can improve adhesion with sealing resin and inhibit moisture infiltration, even for a semiconductor device with a short lead length structure.SOLUTION: A lead frame 100 is a lead frame having a plurality of leads 102 spaced around a mounting area 101 of the semiconductor chip and extending from the mounting area 101 side, and the lead 102 has a lead tip 102a located on the side adjacent to the mounting area 101 and a lead body 102b with step 102c along the edge in the direction of extension of the top surface.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a lead frame and a semiconductor device using the same. [Background technology]

[0002] In a manufacturing process called a "post-process" in the manufacturing process of a resin-encapsulated semiconductor device, a lead frame on which a die pad and leads are formed is often used first.

[0003] The specific manufacturing process involves fixing a semiconductor chip on the top surface of the die pad, electrically connecting the semiconductor chip to the leads with bonding wires, clamping the lead frame between two dies, injecting resin into the dies and solidifying it to seal them, and then dividing them into individual pieces to produce multiple semiconductor devices.

[0004] When the semiconductor device manufactured in this manner is subjected to a moisture absorption treatment, which is a pretreatment for a reliability test, or a reliability test under high temperature and humidity conditions, moisture penetrates through the interface between the leads and the sealing resin and accumulates inside the semiconductor device. If reflow is performed in this state, the temperature of the moisture accumulated at the interface between the leads and the sealing resin rises rapidly and the moisture expands in volume during the process of vaporization. This volume expansion of the moisture may cause peeling at the interface between the leads and the sealing resin, which may result in defects such as disconnection of the bonding wire.

[0005] In particular, in semiconductor devices that are divided into individual pieces by cutting, mechanical stress is applied to the leads during cutting, which makes it easy for peeling to occur at the interface between the leads and the sealing resin. Also, in the case of semiconductor devices with short leads, moisture can easily reach the tip of the leads from the outside.

[0006] In order to prevent peeling at the interface between the lead and the sealing resin and the infiltration of moisture, for example, the invention described in Patent Document 1 provides a narrow portion of the lead and forms a groove on the top surface of the lead perpendicular to the longitudinal direction of the lead, thereby preventing moisture from penetrating from the outside into the tip of the lead. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-268017 A Summary of the Invention [Problem to be solved by the invention]

[0008] One aspect of the present invention aims to provide a lead frame that can improve adhesion with sealing resin and suppress the intrusion of moisture, even in a semiconductor device having a structure with short leads. [Means for solving the problem]

[0009] The lead frame in one embodiment of the present invention comprises: A lead frame having a plurality of leads arranged at intervals around a mounting portion of a semiconductor chip and extending from the mounting portion, The lead is a lead tip portion located adjacent to the mounting portion; a lead body having a step portion along a side in an extension direction of an upper surface; Equipped with. Effect of the Invention

[0010] According to one aspect of the present invention, it is possible to provide a lead frame that can improve adhesion with a sealing resin and suppress the intrusion of moisture, even in a semiconductor device having a structure with short leads. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a schematic top view of a lead frame in an embodiment of the present invention. [Figure 1B] FIG. 1B is an enlarged view of part A in FIG. 1A. [Figure 2A]FIG. 2A is a schematic cross-sectional view taken along line II-II shown in FIG. 1A. [Figure 2B] FIG. 2B is an enlarged view of part B in FIG. 2A. [Figure 3A] FIG. 3A is a schematic cross-sectional view taken along line III-III shown in FIG. 1A. [Figure 3B] FIG. 3B is an enlarged view of part C in FIG. 3A. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV shown in FIG. 1A. [Diagram 5] FIG. 5 is a schematic cross-sectional view of line VV shown in FIG. 1A. [Figure 6] FIG. 6 is a schematic side view showing a state after the lead frame and the semiconductor chip have been connected by wire bonding in the embodiment of the present invention. [Figure 7] FIG. 7 is a schematic side view (perspective view) showing a semiconductor device using a lead frame in an embodiment of the present invention. [Figure 8] FIG. 8 is a schematic side view showing the exposed lead side of a semiconductor device using a lead frame in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The lead frame in the embodiment of the present invention is based on the following findings. The lead frame described in Patent Document 1 can suppress the intrusion of moisture to a certain extent. However, since a groove is formed on the upper surface of the lead perpendicular to the lead longitudinal direction, the thickness of the lead is thin, and the mechanical strength is reduced. For this reason, when cutting into individual pieces, stress is concentrated in the groove part where the lead is thin, and peeling is likely to occur at the interface between the lead and the sealing resin at the groove part. Moisture that has infiltrated from the interface between the lead and the sealing resin accumulates at this peeling point. If reflow is performed in this state, the temperature of the moisture accumulated at the peeling point rises suddenly and the volume of the moisture expands in the process of vaporization. This volume expansion of the moisture may cause slight peeling at the interface between the lead and the sealing resin, which may cause defects such as disconnection of the bonding wire.

[0013] Therefore, the lead frame in one embodiment of the present invention is a lead frame having a plurality of leads arranged at a distance around the mounting portion of a semiconductor chip and extending from the mounting portion, and the leads have a lead tip portion located on the side adjacent to the mounting portion, and a lead main body portion having a step portion provided along an edge in the extension direction of the upper surface.

[0014] As a result, this lead frame can provide a lead frame that can improve adhesion with the sealing resin and suppress the infiltration of moisture, even in a semiconductor device having a structure with short leads.

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0016] In the drawings, the same components are denoted by the same reference numerals, and duplicate explanations may be omitted.

[0017] Additionally, the X-axis, Y-axis, and Z-axis shown in the drawings are mutually perpendicular. The Z-axis direction may be referred to as the "height direction" or "thickness direction." The surface of each component on the +Z side may be referred to as the "front surface" or "top surface," and the surface on the -Z side as the "back surface" or "bottom surface." "Planar view" refers to viewing each component from the +Z side toward the -Z side.

[0018] Furthermore, the drawings are schematic, and the ratios of width, depth, and thickness are not as shown. The quantity, position, shape, structure, size, etc. of each member are not limited to the embodiments shown below, and may be any quantity, position, shape, structure, size, etc. that are preferable for implementing the present invention. (An example of an embodiment) Fig. 1A is a schematic top view of a lead frame in an embodiment of the present invention, and Fig. 1B is an enlarged view of part A in Fig. 1A. Fig. 2A is a schematic cross-sectional view taken along line II-II in Fig. 1A, and Fig. 2B is an enlarged view of part B in Fig. 2A. Fig. 3A is a schematic cross-sectional view taken along line III-III in Fig. 1A, and Fig. 3B is an enlarged view of part C in Fig. 3A. Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 1A, and Fig. 5 is a schematic cross-sectional view taken along line VV in Fig. 1A.

[0019] 1A, the lead frame 100 has a plurality of leads 102. In this embodiment, the lead frame 100 is formed with a die pad 101, suspension leads 103, and tie bars 104. The plurality of leads 102 are arranged at intervals around the die pad 101 in a plan view. The plurality of leads 102 extend from the die pad 101 side and are connected to the tie bars 104.

[0020] Note that a plurality of combinations of a plurality of leads 102, a die pad 101, and a suspension lead 103 are formed on the lead frame 100, and FIG. 1A shows one combination that forms one semiconductor device.

[0021] This lead frame 100 is the base of the semiconductor device 10. As will be described later in detail, the die pad 101 is a mounting portion for the semiconductor chip 110, and the semiconductor chip 110 is fixed thereto by a conductive adhesive 120. Lead tip portions 102a of the multiple leads 102 are electrically connected to the electrode pads of the semiconductor chip 110 by bonding wires 130 (see FIG. 6). Next, the lead frame 100 is sandwiched between two molds, and a sealing resin 140 is injected into the molds and solidified. At this time, a part of the lead 102 is exposed so that it functions as an external terminal, and multiple semiconductor devices 10 are manufactured by dividing the lead frame 100 into individual pieces. In this embodiment, the lead frame 100 is formed of a copper alloy.

[0022] 1B, the multiple leads 102 include lead tip portions 102a located on the side facing the die pad 101, and lead body portions 102b connected to tie bars 104. Lead body portions 102b are provided with step portions 102c along the sides in the extension direction of the upper surface of lead body portions 102b.

[0023] 1B and 3B, the lead tip 102a has a length s1 and a width w1. The lead body 102b has a length s2, an upper width w21, and a lower width w22. The width w22 of the lower six faces of the lead body 102b is the same as the width w1 of the lead tip 102a.

[0024] 2A and 2B, lead tip 102a has a thickness t1 and a width w1, and is formed so that the width of the upper surface and the lower surface are the same. The upper surface of lead tip 102a is electrically connected to the electrode pad of semiconductor chip 110 by bonding wire 130. For this reason, the upper surface of lead tip 102a is formed to be a smooth surface. This ensures a sufficient bonding area for wire bonding and suppresses a decrease in connection strength.

[0025] As shown in FIG. 3A, FIG. 3B, and FIG. 5, the lead body 102b has a step portion 102c provided along a side in the extension direction of the upper surface of the lead body 102b. The thickness t22 of the step portion 102c is thinner than the thickness t21 of the lead body 102b. In this embodiment, the thickness t21 of the lead body 102b is the same as the thickness t1 of the lead tip portion, and the thickness t22 of the step portion 102c is thinner by half the thickness t21 of the lead body 102b. This results in a structure in which the area where the lead body 102b and the sealing resin 140 are bonded to each other is increased, and the adhesion between the lead body 102b and the sealing resin 140 can be improved.

[0026] The width w21 of the upper surface of the lead body 102b is narrower than the width w1 of the lead tip 102a. In this embodiment, the width w21 of the upper surface of the lead body 102b is narrower than 1 / 3 of the width w1 of the lead tip 102a. This results in a structure in which most moisture infiltration passes through the step portion 102c, and by lengthening the moisture infiltration path, it is possible to suppress the infiltration of moisture.

[0027] As shown in FIG. 4, the thickness t21 of the lead body 102b is the same as the thickness t1 of the lead tip, and the upper surface of the lead body 102b is flush with the upper surface of the lead tip 102a. The lower surface of the lead body 102b is flush with the lower surface of the lead tip 102a. As shown in FIG. 1B, the width w22 of the lower surface of the lead body 102b is the same as the width w1 of the lead tip 102a. This allows the lead 102 to have a simple structure that can be obtained by forming the step portion 102c of the lead body 102b. This makes processing easier and reduces manufacturing costs.

[0028] 4 and 5, the lead tip portion 102a has a step 102d on the lower surface facing the die pad 101. This prevents the lead 102 from falling off the sealing resin 140.

[0029] In this manner, the lead frame 100 has the step portion 102c provided along the side in the extension direction of the upper surface of the lead body portion 102b. The step portion 102c improves the adhesion between the lead 102 and the sealing resin 140 and also suppresses the intrusion of moisture.

[0030] Furthermore, the thickness t21 of the lead body 102b and the width w22 of the lower surface of the lead body 102b are the same as the thickness t1 and width w1 of the lead tip 102a. This allows the lead body 102b to have a uniform thickness from the tie bar 104 to the lead tip 102a, which can prevent a decrease in mechanical strength and prevent peeling at the interface between the lead 102 and the sealing resin 140.

[0031] In this embodiment, only the top surface of the lead tip 102a of the lead 102 is silver plated. By silver plating only the top surface of the lead tip 102a and making the rest of the lead tip 102 and the surface of the lead body out of a copper alloy, the adhesion between the lead 102 and the sealing resin 140 is improved.

[0032] Furthermore, in order to improve the adhesion of the sealing resin 140 even if only slightly, the leads 102 may be subjected to a surface roughening treatment to form minute projections and recesses.

[0033] A method of forming the leads 102 in the leadframe 100 will now be described.

[0034] A press process is performed on the upper surface of the lead 102 to form the step portion 102c of the lead body 102b so that the step portion 102c has a predetermined thickness. Next, a press process is performed to shear the lead 102 in accordance with the position of the step portion 102c, thereby providing the lead tip portion 102a and the lead body 102b.

[0035] In this way, the lead frame 100 is provided with the step portion 102c along the side in the extension direction of the upper surface of the lead body portion 102b. This improves the adhesion between the lead 102 and the sealing resin 140, and the structure is such that most of the moisture intrusion route passes through the step portion 102c, thereby suppressing the intrusion of moisture. In addition, by making the thickness t21 of the lead body portion and the width w22 of the lower surface of the lead body portion 102b the same as the thickness t1 and width w1 of the lead tip portion 102a, it is possible to suppress peeling at the interface between the lead 102 and the sealing resin 140 without reducing the mechanical strength.

[0036] Next, a method for manufacturing a resin-encapsulated semiconductor device using the lead frame 100 will be described with reference to FIGS.

[0037] 6, a semiconductor chip 110 is fixed to the upper surface of a die pad 101 with a conductive adhesive 120. Then, a plurality of electrode pads (not shown) formed on the upper surface of the semiconductor chip 110 and the upper surfaces of the lead tips 102a of the plurality of leads 102 are electrically connected with bonding wires 130.

[0038] Next, the lead frame 100 is sandwiched between two dies (not shown), and sealing resin is injected into the dies and solidified to seal, and then the dies are cut into individual pieces, thereby manufacturing the semiconductor device 10 as shown in Figures 7 and 8. As shown in Figures 7 and 8, a part of the lead 102 is exposed from the sealing resin 140 to function as an outer lead. In addition, in order to improve the heat dissipation of the semiconductor chip 110, the lower surface of the die pad 101 is also exposed from the sealing resin 140.

[0039] Thus, the semiconductor device 10 in this embodiment has a lead frame 100, a semiconductor chip 110 mounted on a semiconductor chip mounting portion 101 and having a plurality of electrode pads electrically connected to the lead tips 102a of a plurality of leads 102, and a sealing resin 140 covering at least a portion of the leads 102.

[0040] This improves the adhesion between the lead frame 100 and the sealing resin 140 of the semiconductor device 10, and also suppresses the intrusion of moisture. This makes it difficult for defects such as breakage of the bonding wires 130 to occur, thereby improving the reliability of the semiconductor device 10.

[0041] Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and includes designs and the like within the scope of the gist of the present invention.

[0042] For example, in the present embodiment, the mounting portion of the semiconductor chip is a die pad, but it is not limited thereto and may be a resin film. In addition, the electrical connection between the lead and the semiconductor chip is made by wire bonding, but it may be made by a flip chip and a collection of pads forming Au bumps. That is, the lead frame has a structure in which the die pad is integrated, but the die pad may not be required. The material of the lead frame is a copper alloy, but it is not limited thereto and may be other materials. Only the upper surface of the lead tip is silver plated, but the upper surface of the lead body may be silver plated. It is not limited to silver plating and may be other plating films. In addition, the leads of the lead frame are formed by pressing, but it is not limited thereto and may be formed by etching or the like. [Explanation of symbols]

[0043] 10 Semiconductor device 100 Leadframe 101 Die pad (part for mounting semiconductor chip) 102 Leads 102a Lead tip 102b Lead body 102c Step 102d Step (underside of lead tip) 103 Suspension Lead 104 Tie bar 110 Semiconductor Chip 120 Conductive adhesive 130 Bonding Wire 140 Sealing resin s1 Length of the lead tip s2 Length of lead body t1 Thickness of the lead tip t21 Lead body thickness t22 Thickness of step w1 Width of lead tip w21 Width of the top surface of the lead body w22 Width of the bottom of the lead body

Claims

1. A lead frame having a plurality of leads arranged at intervals around a mounting portion of a semiconductor chip and extending from the mounting portion, The lead is a lead tip portion located on the mounting portion side; a lead body having a step portion along a side in an extension direction of an upper surface; A lead frame comprising:

2. 2. The lead frame according to claim 1, wherein an upper surface of the lead body is flush with an upper surface of the lead tip.

3. 2. The lead frame according to claim 1, wherein a lower surface of the lead body is flush with a lower surface of the lead tip and is formed with the same width as the lead tip.

4. 2. The lead frame according to claim 1, wherein the width of the upper surface of the lead body is 1 / 3 or less of the width of the upper surface of the lead tip.

5. 2. The lead frame according to claim 1, wherein the thickness of the step portion of the lead body is equal to or less than half the thickness of the lead tip portion.

6. The lead frame according to claim 1 , wherein the length of the lead body is equal to or less than half the length of the lead.

7. 2. The lead frame according to claim 1, wherein the top surfaces of the lead tips are plated with silver.

8. A lead frame according to any one of claims 1 to 7, the semiconductor chip is mounted on the mounting portion and includes a plurality of electrode pads electrically connected to the lead tip portions of the plurality of leads, respectively; a sealing resin covering at least a portion of the lead; A semiconductor device comprising:

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