JPH02235365A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To reduce stress generating in a semiconductor element, and improve heat dissipation by forming an island part of material whose linear expansion coefficient is small, and forming a lead part of material whose thermal conductivity is large. CONSTITUTION:A plate type clad material wherein iron based alloy like 42 alloy and copper based alloy like phosphor bronze are stacked and made composite, is etched. An island part 1 and a retaining arm 5 are formed of iron based alloy 10. A lead part 2 and a tie bar 4 are formed of copper based alloy 11. A frame 3 is formed by stacking the alloy 10 and the alloy 11 as intact. By this constitution, the linear expansion coefficient of the island part 1 becomes approximate to that of the semiconductor element, so that the stress generating in the element is reduced. The thermal conductivity of the lead part 2 is large, so that heat dissipation is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a lead frame for a semiconductor device (hereinafter referred to as
(referred to as lead frames).

(Prior art) Fig. 5 is a perspective view showing a conventional lead frame, in which a plate material of a copper alloy such as phosphor bronze or an iron alloy such as 42 alloy is used to form a required pattern by etching or punching with a mold. In the figure, (1) is an island part on which a semiconductor element is placed, (2) is a lead part for leading out the semiconductor element to the outside and establishing electrical continuity.
(3) is a frame placed at both ends of the lead frame;
) and (5) are tie bars and support arms that connect and support the lead part (2) and island part (1) to the frame (3), respectively.

FIG. 6 is a perspective view showing a semiconductor element assembled on the lead frame of FIG. 5, in which a semiconductor element (6) made of silicon is placed on an island part (1) and a bonding material (7) is fixed. Semiconductor element (6)
There is a thin metal wire (9) between the electrode (8) and the lead part (2).
are bonded and electrically connected to each other (4).
), support arm (5), cutting and removal of frame (3), lead part <<2
] is performed to manufacture the semiconductor device.

Next, the operation will be explained. When the semiconductor element (6) is energized, heat is generated there, transmitted to various parts, and the temperature rises. This heat is absorbed by the lead part (2) and the package (not shown).
is emitted to the outside. By the way, the coefficients of linear expansion of each part made of different materials are different, and since the semiconductor element (6) is fixed to the island part (1), stress is generated depending on the difference in coefficient of linear expansion between the two and changes in temperature.

FIG. 7 is a perspective view showing another conventional lead frame, in which the island portion (1) is sunk downward in the figure by press working. FIG. 8 is a sectional view showing a state in which a semiconductor element is assembled on the lead frame of FIG. 7. In the example shown in Fig. 6, there is a large step in the height direction at both ends of the thin metal wire (9), so the bonded thin metal wires (9) may be too close to each other. ), so if you try to pull out the lead part (2) from the center of the package (not shown) in the thickness direction, the size of the package (not shown) will become larger; In this case, since the position of the semiconductor element (1) is low, such a situation will not occur.

[Problems to be solved by invention]

Conventional lead frames are made of a single material as described above, and when iron-based alloys such as 427 Roy are used, their thermal conductivity is low, making it difficult for the heat generated in the semiconductor element to dissipate to the outside. In addition, when copper-based alloys are used, their coefficient of linear expansion is much higher than that of semiconductor elements made of silicon, etc., which increases the stress generated in the semiconductor elements and impairs their characteristics. However, due to the recent demand for higher performance of semiconductor devices,
As the size of semiconductor devices increases, the above problems tend to become more noticeable.

This invention was made to solve the above-mentioned problems, and aims to provide a lead frame that can reduce the stress generated in a semiconductor element and has good heat dissipation.

[Means to solve the problem]

In the lead frame according to the present invention, the island portion and the lead portion are respectively formed of a first material and a second material, the first material is made of a material having a coefficient of linear expansion smaller than that of the second material, and the first material is made of a material having a smaller linear expansion coefficient than the second material. As the second material, a material having higher thermal conductivity than the first material is used.

[For production]

In the lead frame of the present invention, the linear expansion coefficient of the first material used for the island portion is small, so the linear expansion coefficient is close to that of silicon, etc. used in the semiconductor element, and the stress generated in the semiconductor element is reduced. In addition, since the second material has a high thermal conductivity, heat generated in the semiconductor element can be efficiently dissipated to the outside. In other words, the preferable characteristics of both of the above materials can be utilized.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a perspective view showing a lead frame according to an embodiment of the present invention. The shape shown in the figure is formed by etching a composite plate-shaped cladding material made of a copper-based alloy. (1) to (5) are the cases shown in Figure 5. It has the same shape and function as , but the island part (1) and support arm (5) are made of iron-based alloy QO, and the lead part (
2) and the tieper (4) are made of a copper-based alloy (b), and the frame (3) is formed by overlapping the iron-based alloy αQ and the copper-based alloy αQ. Figure 2 is a cross-sectional view taken along line 1-1 in Figure 1, and the island part (1) and lead part (2) are made by removing one material from the cladding material, which is made by superimposing two types of materials. Since they are formed in parallel, they are shifted from each other in the vertical direction in the figure.

Next, the manufacturing method will be explained. Fig. 3 is a cross-sectional view of a part corresponding to Fig. 2 showing the method for manufacturing the lead frame of Fig. 1. As shown in the same figure (6), the first mask (self) is connected to the lead part (2), tieper (4) and The copper-based alloy (B) is selectively removed by forming it in the area corresponding to the frame (3) and etching it from the direction of the arrow to the interface between the two cladding materials, as shown in Figure (C). Next, as shown in ) in the same figure, a second mask (to) is formed on the iron-based alloy o1 side at a location corresponding to the island part (1), support arm (5) and frame (3), and By etching from the direction of the cladding material to the interface between both materials,
As shown in FIG. 2(E), the iron-based alloy 00 is selectively removed, resulting in a structure similar to that shown in FIG. 2.

In the semiconductor device using the above lead frame,
Since the island portion (1) is formed of the iron-based alloy αQ, its coefficient of linear expansion is smaller than that of the copper-based alloy α. In the case of iron-based alloys, it is 1 to 1 times as large as silicon.
．． The coefficient of linear expansion is 5 times that of silicon, which is close to that of silicon. Furthermore, since the lead portion (2) is made of a copper-based alloy (b), it has a higher thermal conductivity than an iron-based alloy, and therefore conducts the heat generated in the semiconductor element to the outside.Furthermore, in this embodiment, , copper-based alloy αη is easily plastically deformed, so it can be easily bent even in cases such as J leads.In addition, as can be seen in Figures 1 and 2, the island part (11 is the lead part (2
), but in the case of Fig. 7, the support arm (6) is bent by a press, whereas in this example, it is etched, so the accuracy of the sinking dimension is There is also the effect that it is good.

FIG. 4 is a perspective view of a lead frame according to another embodiment of the present invention, in which a lead part (2) is provided with an extension part (self) that reaches and overlaps the island part (1), and the semiconductor element The heat generated in the lead portion (2) is better transmitted to the lead portion (2), and therefore heat dissipation to the outside is improved.

In addition, although phosphor bronze was shown as the second material in the above embodiment, tinned copper, copper-nickel alloy, etc. may also be used.

〔Effect of the invention〕

As described above, according to the present invention, the island portion and the lead portion are formed of the first and second materials, respectively, and the first material is made of a material having a smaller coefficient of linear expansion than the second material. Since the second material is configured to have a higher thermal conductivity than the first material, it is possible to utilize the favorable characteristics of each material, and the coefficient of linear expansion of the island portion is equal to that of the semiconductor element. Because they are close to each other, stress generated in the semiconductor element is reduced, and because the lead portion has high thermal conductivity, heat generated in the semiconductor element is effectively dissipated from the lead portion.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a lead frame according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line 1-1 in FIG. 1, and FIG.
The figure is a cross-sectional view showing the manufacturing method of the lead frame shown in Figure 1.
FIG. 4 is a perspective view of a lead frame according to another embodiment of the present invention, FIG. 5 is a perspective view of a conventional lead frame, and FIG.
The figure is a perspective view showing a semiconductor element assembled on the lead frame of FIG. 5, I! FIG. 7 is a perspective view showing another conventional lead frame, and FIG. 8 is a sectional view showing a semiconductor element assembled on the lead frame of FIG. In the figure, <<1) is an island portion, (2) is a lead portion, (6) is a semiconductor element, αQ is an iron-based alloy, and (b) is a copper-based alloy. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Patent Attorney Masu Oiwa Yuken Ekatsu 4R5A Figure 6: Kamo Senbukuro 3 Review Figure 8 Figure 1 Display of the Case 1999 Patent Application No. 056608 2 Name of Invention Lead for Semiconductor Device Frame 3 Relationship with the case of the person making the amendment Patent Applicant Address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601 1) Mitsubishi Electric Corporation Representative Moriya Shiki 4 Agent Address Marunouchi, Chiyoda-ku, Tokyo 2-2-3 Mitsubishi Electric Corporation Name (7375) Patent attorney Masuo Oiwa and 2 others 5
Drawings (Figures 6 and 8) in the detailed description of the invention in the specification to be amended? Details of the amendment (1) In the 14th line of page 3 of the specification, the phrase ``comrade'' is corrected to ``in the corner of the semiconductor element (6).'' ■ On page 3 of the specification, lines 18 and 19, it says that "the dimensions of the package (not shown) will be larger" is shown in the upper side of the semiconductor element (6) and the lower ■ side of the island part {1) in figure r. The thickness of the molded resin (not shown) is different, creating a force that causes the package to warp.'' (3) Correct the drawings (Figures 6 and 8) as shown in the attached sheet. (The lead part of the thin metal wire (9) (the bulge at the tip on the 21 side has been erased.) 7 Attached document catalog drawings (Figures 6 and 8)

Claims (1)

[Claims] In a device comprising an island portion on which a semiconductor element is placed and a lead portion leading the semiconductor element to the outside, the island portion is formed of a first material, the lead portion is formed of a second material, The first material has a linear expansion coefficient smaller than that of the second material, and the second material has a coefficient of linear expansion smaller than that of the second material.
A lead frame for semiconductor devices characterized by higher thermal conductivity than other materials.