JP2000294711A - Lead frame - Google Patents

Abstract

(57) [Problem] To provide a lead frame in which a bent portion of a lead is not damaged such as a crack when bending the lead. SOLUTION: This lead frame 30 is a surface mount IC.
This is a lead frame for a package, and has the same configuration as a conventional lead frame except that grooves are provided in all leads 32. The grooves 34 and 36 are provided at positions that serve as fulcrums for bending when the lead 32 is bent. The groove 34 is formed in the lead so as to have a downward opening just outside the boundary line 18 of the resin sealing region, and the groove 36 is formed in the lead so as to have an opening upward outside the groove 34. ing. The groove is a U-shaped groove provided by chemically etching the lead. The depth of the groove is not less than ３ and not more than の of the thickness t of the lead. Surface mount type I
When this lead frame is used for the C package and the lead is subjected to a bending process, a bent portion having no damage such as cracks is formed in two bent portion forming regions of the lead due to the effect of providing the groove portion. Is done.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for a package of an IC chip, and when forming an IC package, forming a bent portion on a lead by performing a bending process outside a sealing mold of the IC package. More particularly, the present invention relates to a lead frame in which a bent portion of the lead is not damaged such as a crack when the lead is subjected to a bending process.

[0002]

2. Description of the Related Art An IC chip composed of one semiconductor element on which an integrated circuit is formed is usually die-bonded on a lead frame, and then wire-bonded between electrodes of the IC chip and inner leads of the lead frame. Then, it is sealed with a sealing material such as resin or ceramic. Then, unnecessary lead frame portions are cut off, and the leads are bent to form bent portions. Have been.

[0003] Incidentally, depending on the mounting method at the time of mounting the IC package 1, the IC package is a surface mount type I package.
It is roughly classified into a C package and an insertion type IC package. In order to facilitate the work of mounting the IC package on the mounting board, the leads of the IC package should be used in accordance with the mounting method of the surface mount type package and the insertion type package.
It is bent on the outside sealed with resin.

For example, a surface mount type IC package 1 is
As shown in FIG. 6A, the lead 2 of the IC package 1
Is soldered to electrode pads of a wiring pattern on a mounting board (not shown) and mounted. The leads 2 are bent downward on the outside sealed with resin, and then bent outward. ing. The insertion type IC package 3 is shown in FIG.
As shown in (b), the lead 4 is inserted into an insertion hole of a mounting board (not shown) and mounted, and the lead 4 is bent downward on the outside sealed with resin. In FIG.
5 is an IC chip, 6 is a bonding wire, 7 is a sealing material such as resin or ceramic when sealing the IC package, 8 is a part of a lead frame, and a die pad for die bonding the semiconductor element 1. It is.

[0005] A lead frame for bonding a semiconductor element is formed by punching or etching a metal tape such as an Fe-Ni alloy or a Cu alloy. As shown in FIG. 7, a typical planar lead frame 10 has
Each IC chip is provided with a die pad (island) 12 for bonding the IC chip, leads 14 extending radially from a position separated from the die pad 12, and a die support bar 16 for supporting the die pad 12. It is continuous. In FIG. 7, reference numeral 18 denotes a boundary line of a sealing mold made of resin or the like, and a region inside the boundary line 18 of the lead frame 10 is sealed with a sealing material.

A lead frame 20 of another shape is
Similarly, it is formed by punching a metal tape of Fe—Ni alloy, Cu alloy, or the like. As shown in FIG. 8, a die pad (island) 22 for bonding IC chips and a die pad 22 are provided for each IC chip. An inner lead 24 extending radially from a position separated from the inner lead 24,
Outer lead 26 connected to inner lead 24
And a tie bar 28 for sequentially connecting the connecting portions of the inner lead 24 and the outer lead 26, and a die support bar 29 for supporting the die pad 12, and are continuous in a tape shape.

[0007]

By the way, in order to facilitate the operation of mounting an IC package on a mounting board, an I / O package is required.
As described above, the lead of the C package is bent on the outside sealed with a resin.
By pressing the external terminals of the leads into the mold and pressing,
It has been bent. However, the lead frame is
Since the lead is thicker, the radius of curvature of the bend becomes smaller because the lead is made of a metal such as an e-Ni alloy or a Cu alloy. As shown in FIG. Compressive stress is generated on the inner periphery of the portion, and cracks, cracks, and the like occur in the bent portion of the lead. Once damages such as cracks and cracks are generated, stress concentrates and progresses inward with the passage of time and with repeated changes in the external environment such as temperature changes.

Accordingly, when cracks, cracks, and the like occur in the bent portion of the lead, the following various problems occur,
Product yield decreases. Such defects include, for example, a decrease in lead strength, a deterioration in the appearance of the lead, and a failure in product inspection, a deterioration in solderability when mounting the IC package on the substrate, and a bending process of the lead. This is a problem such as a decrease in the accuracy of

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lead frame in which a bent portion of the lead is not damaged when the lead is bent.

[0010]

In order to achieve the above-mentioned object, a lead frame according to the present invention is a lead frame for a package of an IC chip. The lead frame is formed by bending at the outside of the lead to form a bent portion in the lead, characterized in that the groove is formed at the center of curvature of the lead portion forming the bent portion.

In order to improve the bending processability of the external terminals (leads) of the IC package and prevent damage such as cracks from occurring in the leads, a groove is formed at the center of curvature of the lead portion forming the bent portion. Then, as shown in FIG.
By relaxing the tensile stress and the compressive stress at the outer periphery of the bend by the groove, damage such as cracks can be prevented. Also,
In the groove portion, unlike a crack or the like, the once formed groove shape does not expand over time. Although there is no limitation on the method of forming the groove, for example, the groove may be formed by etching the lead frame by a chemical etching method, or the groove may be formed by indentation by a mechanical pressing method using a mold. .

A lead frame to which the present invention is applied is an IC
When forming a package, the type and shape of the lead frame are limited as long as the lead frame is used for an IC package that is formed by bending outside the sealing mold of the IC package to form a bent portion of the lead. However, the present invention can be applied to, for example, a lead frame for a surface mount type IC package and a lead frame for an insertion type IC package. There is no limitation on the shape of the lead frame. For example, the lead frame 10 shown in FIG. 7 or the lead frame 20 shown in FIG. 8 may be used.

In a preferred embodiment of the present invention, the groove is provided at a position which becomes a fulcrum of bending at the time of bending. This further enhances the effect of forming the groove. Preferably,
The depth of the groove is not less than ３ and not more than の of the thickness of the lead, and the sectional shape of the groove is not limited.
It is a U-shaped groove or a U-shaped groove, but is preferably a groove shape without an angle, for example, a U-shaped groove.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment of a lead frame according to the present invention. FIG. 1 is a plan view showing a configuration of a lead frame of this embodiment, and FIG. FIG. 3 is a detailed view showing a groove shape and a groove dimension provided in a bent portion of a lead of the lead frame, and FIG. 3 is a side view of a surface mount type IC package using the lead frame of the present embodiment. FIG.
5, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. The lead frame 30 of the present embodiment is a lead frame for a surface mount IC package, and has the same configuration as the conventional lead frame 10 shown in FIG. 7 except that all the leads 32 are provided with grooves. ing.

As shown in FIG. 1, the grooves 34 and 36 are lead portions on the center of curvature of a bent portion forming region where a bent portion is formed in the lead 32, and serve as fulcrums of bending when the lead 32 is bent. It is provided in the position. The groove portion 34 is formed in the lead 32 so as to have an opening below at a position just outside the boundary line 18 of the resin sealing region, and the groove portion 36 is formed so as to have an opening above at a position outside the groove portion 34. 32.

The grooves 34 and 36 provided in the lead frame 30 of this embodiment are grooves formed by etching a bent portion forming region of the lead frame 30 by a chemical etching method, and as shown in FIG. , U-shaped grooves.
The depth of the grooves 34 and 36 is １ ／ of the thickness t of the lead 32.
More than 1/2. Surface mount type IC package 34
When the lead frame 30 according to the present embodiment is used and the lead 32 is bent, as shown in FIG. 3, two bent portion forming regions of the lead 32 are formed due to the effect of providing the grooves 34 and 36. Are formed with bent portions 38 and 39 in which damage such as cracks does not occur.

Embodiment 2 This embodiment is another example of the embodiment of the lead frame according to the present invention, and FIG. 4 shows a groove shape provided in a bent portion of a lead of the lead frame of this embodiment. FIG. 5 is a side view of a surface mount type IC package using a lead frame according to the present embodiment. The lead frame of the present embodiment is the same as the lead frame of the first embodiment except that the shape of the groove is a V-shaped groove instead of the U-shaped groove of the grooves 34 and 36 of the first embodiment. It has a configuration. As shown in FIG. 4, the groove portions 40 and 42 provided in the lead frame of the present embodiment are V-shaped grooves formed by pressing the bent portion forming region of the lead 44 with a mold. . The depth of the grooves 40 and 42 is
The thickness is not less than ３ and not more than の of the thickness t of No. 2.

When the lead frame 40 of this embodiment is used for the surface mount type IC package 34 and the lead 32 is bent, the lead 32 is provided as shown in FIG. The bent portions 46 and 48 where no damage such as cracks occur are formed in the two bent portion forming regions.
Is formed.

[0019]

According to the present invention, the stress applied to the bent portion of the external terminal (lead) is reduced by forming the groove in the lead portion on the center of curvature of the lead region forming the bent portion. This has the following effects. (1) Cracks, cracks, and the like generated on the outer periphery of the lead can be significantly reduced. (2) The strength of the lead can be increased by reducing the occurrence of cracks and the like. (3) By improving the appearance (appearance) of the lead, the occurrence rate of defective products in the appearance inspection can be reduced. (4) The lead bending workability and bending accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating a configuration of a lead frame according to a first embodiment.

FIG. 2 is a detailed view showing a groove shape and a groove dimension provided in a bent portion of a lead of a lead frame according to a second embodiment.

FIG. 3 is a side view of a surface mount type IC package using the lead frame according to the first embodiment.

FIG. 4 is a detailed view showing a groove shape and a groove dimension provided in a bent portion of a lead of the lead frame according to the second embodiment.

FIG. 5 is a side view of a surface mount IC package using a lead frame according to a second embodiment.

FIGS. 6A and 6B are cross-sectional views showing the configurations of a surface mount type IC package and an insert type IC package, respectively.

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

FIG. 8 is a plan view showing a configuration of another conventional lead frame.

FIG. 9 is a cross-sectional view of the lead showing a state of a crack generated in a bent portion of the lead.

FIG. 10 is a sectional view of a bent portion of a lead for describing an effect of the lead frame according to the present invention.

[Explanation of symbols]

1 ... Surface mount type IC package, 2 ... Lead, 3
…… Insert type IC package, 4 …… Lead, 5… I
C chip, 6 bonding wire, 7 sealing resin, 8 die pad, 10 lead frame, 12
…… Die pad (island), 14 …… Lead, 16
... die support bar, 18 ... border line of resin sealing, 20 ...
.. Leadframes of different shapes, 22 die pads (islands), 24 inner leads, 26 outer leads, 28 tie bars, 30 lead frame of the first embodiment, 32 lead, 34 , 36... Groove, 38, 39... Bent part, 40, 42... Groove provided in the lead frame of the second embodiment, 44.
6... Lead frame according to the second embodiment, 48, 49.
Bending part.

Claims (4)

[Claims] 1. A lead frame for an IC chip package, wherein a bent portion is formed on a lead by performing a bending process outside a sealing mold of the IC package when forming the IC package. 3. The lead frame according to claim 1, wherein the groove is formed on the center of curvature of a lead portion forming the bent portion. 2. The lead frame according to claim 1, wherein the groove is provided at a position serving as a fulcrum of bending at the time of bending. 3. The lead frame according to claim 1, wherein the depth of the groove is not less than １ ／ and not more than の of the thickness of the lead. 4. The lead frame according to claim 1, wherein the cross-sectional shape of the groove is a V-shaped groove or a U-shaped groove.