JPH04337659A - Lead frame - Google Patents

Abstract

PURPOSE:To obtain a lead frame which enables and assembly of a semiconductor device to be facilitated by eliminating deflection in longer direction or in shorter direction due to self weight of the lead frame. CONSTITUTION:The frame is provided with a die pad 1 where a semiconductor element is jointed and an external frame 4 which retains the die pad 1 through a support arm 3 and a machining curing part 10 is formed at the above external frame 4.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a lead frame for a semiconductor device (hereinafter referred to as a lead frame) used for mounting and bonding semiconductor elements to assemble a semiconductor device.
It is related to.

0002

2. Description of the Related Art FIG. 7 is a plan view showing a part of the conventional lead frame shown in FIG. The lead frame is made by etching or punching a desired pattern using a plate material of a copper alloy such as phosphor bronze or an iron alloy such as 42 alloy. In the figure, 1 is a die pad on which a semiconductor element (not shown) is placed and bonded, 2 is a lead for leading out the semiconductor element to the outside for electrical continuity, and 3 is a die pad that fixes the die pad 1 to the outer frame 4. It is a supporting arm. 5 is a tie bar for fixing the lead 2.

FIG. 8 shows an example of a semiconductor device assembled on the lead frame of FIG. 7, in which a semiconductor device 6 made of silicon is placed on a die pad 1 and a bonding material (not shown) ) is fixed. A thin metal wire 8 is bonded between the electrode 7 formed on the semiconductor element 6 and the lead 2 to electrically connect them.

Next, the operation will be explained. After bonding the semiconductor element 6 onto the die pad 1 of the lead frame shown in FIG. 7 and bringing it into the state shown in FIG.
After a package (not shown) is placed inside the semiconductor device, the tie bars 5 that are no longer needed are cut and removed, and the leads 2 are bent to produce a semiconductor device. The semiconductor element 6 mounted and bonded on the die pad 1 operates by exchanging electric signals with the outside through an electrode 7 on the element, a thin metal wire 8, and a lead 2.

[0005]

[Problems to be Solved by the Invention] Conventional lead frames use thin plates of copper alloys or iron alloys with a thickness of 0.1 mm to 0.25 mm. ), the lead frame deflects in the longitudinal direction due to its own weight, and in the transverse direction as shown in Figure 9(b), the frame may get caught in the equipment during die bonding or wire bonding, or during inspection after wire bonding. There were problems such as deformation of the thin metal wire.

The present invention has been made to solve the above-mentioned problems, and provides a lead frame that eliminates deflection in the longitudinal or lateral directions due to the lead frame's own weight and facilitates the assembly of semiconductor devices. The purpose is to

[0007]

[Means for Solving the Problems] A lead frame according to the present invention includes a die pad to which a semiconductor element is bonded, and an outer frame that holds the die pad via support arms, and the outer frame has a work-hardened portion. It is constructed so that it forms.

[0008]

[Operation] The work-hardened portion of the present invention increases the rigidity of the frame and reduces deflection in the longitudinal or lateral direction of the frame.

[0009]

[Example] Example 1. FIG. 1 is a plan view showing a lead frame according to an embodiment of the present invention. In the figure, 9 indicated by diagonal lines is a groove formed by coining, and 10 is a work-hardened portion formed around this groove 9. The grooves 9 are formed by coining on the longitudinal and lateral surfaces or back surfaces of the outer frame 4 shown in the shaded area in the figure, after etching or punching into a required pattern with a mold, or simultaneously with the punching. It was formed.

Generally, when a metal material is plastically deformed by coining, bending, etc., a large number of dislocations are introduced into the metal material. A plurality of these dislocations become entangled around grain boundaries, solid solution atoms, and precipitated particles in the metal. When attempting to deform a metal material in such a state, the movement of new dislocations is hindered by these entangled dislocations. Therefore, once a metal material has been plastically deformed by coining, bending, etc., its elastic modulus and elastic stress will be higher than at the beginning. This phenomenon is called work hardening.

FIG. 2 shows a cross section of the outer frame 4 of the lead frame which has been work hardened by coining. In the figure, 9 is a groove formed by coining, and a work-hardened portion 10 is formed around this groove 9. As described above, this work-hardened region has a higher elastic modulus than the region where coining is not performed, and the elastic modulus of the entire outer frame 4 is also higher than when coining is not performed.

FIG. 3 shows a metal plate 11 with one end fixed. FIG. 3(a) shows the one without coining, and FIG. 3(b) shows the one with grooves formed by coining. If the plate material is thin and has a small elastic modulus, the plate material bends due to its own weight and a displacement of ΔZ occurs at the tip, as shown in FIG. 3(a). However, when a groove is formed by coining to form a work hardening region as shown in Fig. 3(b), the rigidity increases and
There is no bending in the Z direction as shown in (a).

As described above, according to this embodiment, the work-hardened portion 10 is formed by providing grooves 9 by coining in the longitudinal and lateral directions of the outer frame 4 of the lead frame, as shown in FIG. Therefore, deflection due to the lead frame's own weight in both the longitudinal and lateral directions of the lead frame can be eliminated. Therefore, effects such as preventing the thin metal wire from getting caught in the equipment during die bonding or wire bonding and from deforming the thin metal wire after wire bonding can be obtained.

Example 2. The hatched area in FIG. 4, which describes an embodiment in which coining is performed after a part of the outer frame is bent to the back side, indicates the bent portion 12 of the outer frame 4, which is bent to the back side of the frame. An enlarged view of the folded portion is shown in FIG. 5(a). In this state, since a space 13 is created in the bent portion, the thickness t of the entire frame is likely to vary. Therefore, as shown in FIG. 5(b), if the groove 9 is formed by coining while caulking from the front and back sides of the lead frame, the space 13 is eliminated and at the same time the work hardened part 10 is formed, resulting in the same effect as in the previous embodiment. It will be done.

Example 3. FIG. 6 shows an example in which similar processing is performed between the outer frame 4 and the tie bar 5. Bent part 1 is pre-etched by etching process.
2 is formed, and then folded to the back side and coined to form a groove 9. (Dotted line in the figure) A work-hardened portion is also formed in this manner, and the same effect as in the above embodiment can be obtained.

Note that the work-hardened portion 10 does not necessarily have to be provided on the entire outer frame 4. In addition, it is sufficient to form it on at least one of the front and back sides of the lead frame, and the formation method is not limited to coining only.

[0017]

As described above, according to the present invention, a work-hardened portion is formed in the outer frame of the lead frame, so that the deflection in the longitudinal direction or the lateral direction due to the lead frame's own weight is eliminated, and the semiconductor This has the effect of making it possible to obtain a lead frame that facilitates assembly of the device.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a lead frame according to an embodiment of the present invention.

FIG. 2 is a sectional view of an outer frame illustrating a work-hardened portion of the embodiment shown in FIG. 1;

FIG. 3 is a diagram illustrating the deflection of a metal material.

FIG. 4 is a plan view showing a lead frame according to another embodiment of the present invention.

FIG. 5 is an enlarged view of the folded portion of FIG. 4;

FIG. 6 is a diagram showing still another embodiment of the invention.

FIG. 7 is a plan view showing a conventional lead frame.

8 is a plan view showing a semiconductor element assembled on the lead frame of FIG. 7; FIG.

FIG. 9 is a schematic diagram illustrating deflection of a lead frame.

[Explanation of symbols]

1 Die pad 3 Support arm 4 Outer frame 10　　　　Work hardening part

Claims (1)

[Claims] 1. A lead frame comprising a die pad to which a semiconductor element is bonded, and an outer frame that holds the die pad via support arms, the outer frame having a work-hardened portion formed therein. .