JPH1197599A - Lead frame and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead frame which reduces output power level of the ultrasonic wave used for bonding the lead frame to a heat sink, and which prevents deformation and damage or the like of leads, and a method of manufacture thereof. SOLUTION: A lead frame comprises a lead frame body 2 and a heat sink plate 3, bonded together by using an ultrasonic-wave bonding method, wherein a metal layer having superior bonding property to the counter material in the ultrasonic bonding is formed on at least either of the both, and the bonding is performed via the metal layer. Manufacture of the lead frame contains a process of forming a layer of a metal having superior bonding property to the counter material in the ultrasonic bonding onto at least either of the lead frame body 2 and the heat sink plate 3, and a process of bonding the lead frame body 2 and the heat sink plate 3 via the metal layer by using an ultrasonic-wave bonding method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame formed by joining a lead frame body and a heat sink to each other by ultrasonic bonding, and a method of manufacturing the lead frame.

[0002]

2. Description of the Related Art When manufacturing a semiconductor device having a heat sink, a lead frame to which a heat sink is attached in advance, that is, a lead frame formed by joining a lead frame body and a heat sink is used. The lead frame body and the heat sink in the lead frame are joined to each other by an ultrasonic joining machine A as shown in FIG. This ultrasonic bonding machine A has a fixedly mounted stage block B,
An ultrasonic horn C connected to a generator (oscillator) (not shown); a heat sink H is placed at a predetermined position of the lead frame body L set on the stage block B; By pressing the lead frame body L and the heat radiating plate H to each other by C and applying ultrasonic waves, the lead frame L and the heat radiating plate H are joined, and the lead frame LF is manufactured.

[0003]

By the way, the lead frame body L and the heat radiating plate H constituting the above-mentioned lead frame LF are almost always formed of a copper-based metal material. Therefore, when the lead frame main body L and the heat sink H are ultrasonically bonded as described above, the lead frame main body L and the heat sink H both made of a copper-based material having good heat dissipation properties are used.
It is difficult for heat to be stored in the joint with the above, and it is necessary to increase the output (energy) of the ultrasonic wave applied to the joint. As described above, since a large amount of energy is required for joining the lead frame body L and the heat sink H, the work involved in manufacturing the lead frame LF becomes complicated, and the ultrasonic joining machine becomes large. In addition, due to the application of the ultrasonic wave having a large energy to the joint, the lead frame body L and the heat radiating plate H are greatly damaged, which may lead to deformation or breakage of the lead.
SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to suppress the output of ultrasonic waves applied at the time of ultrasonic bonding, suppress the damage to the lead frame main body and the heat sink, and generate the deformation or breakage of the lead. An object of the present invention is to provide a lead frame and a method for manufacturing the same, which can prevent the occurrence of the lead frame.

[0004]

According to the lead frame of the present invention, at least one of the lead frame main body and the heat radiating plate is formed with a metal layer having an excellent joining property by ultrasonic joining to the other material. The lead frame body and the heat sink are ultrasonically bonded to each other via a metal layer.

[0005] Further, a method of manufacturing a lead frame according to the present invention includes a step of forming a metal layer having excellent bonding properties in ultrasonic bonding on at least one of a lead frame body and a heat sink, Bonding the lead frame main body and the heat sink to each other by ultrasonically bonding the lead frame main body and the heat sink through the metal layer.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments. As is clear from FIG.
A lead frame 1 according to the present invention includes a lead frame main body 2 and a heat sink 3 bonded to the lead frame main body 2.
Is provided.

The lead frame body 2 is formed by punching or etching a thin copper-based metal plate, has a large number of inner leads 2a, 2a,... 3 are provided diagonally opposed to each other to mount three tabs 2b, 2b,.
b are bent so as to protrude downward so as to prevent the inner leads 2a, 2a.

On the other hand, the heat radiating plate 3 is formed by punching and forming a thin copper-based metal plate, similarly to the lead frame main body 2, and corresponds to the four tabs 2b of the lead frame main body 2. It has a rectangular shape.

As shown in FIG. 2, the tabs 2b, 2b... Of the lead frame main body 2 have excellent ultrasonic bonding to copper-based metal as a material of the heat sink 3, that is, energy. Without the need for large ultrasonic waves
Metal layer 4 made of Ag (silver) to be joined to heat sink 3
Is formed by plating, and the lead frame 1 is configured by ultrasonically bonding the lead frame main body 2 and the heat sink 3 to each other via the metal layer 4.

To manufacture the lead frame 1 having the above structure, first, as shown in FIG. 3A, a metal layer 4 made of Ag (silver) is formed on the back surface of the tab 2b of the lead frame body 2 by plating. .

Here, the tab 2b of the lead frame body 2
As described above, the material of the metal layer 4 to be formed
Ag (silver) is the most preferable because it has excellent bondability in ultrasonic bonding to copper-based metal, which is the material of the above, and is conventionally applied as plating for wire bonding on inner leads and the like. However, for example, N
i (nickel), Pd (palladium), Au (gold), Pb
(Lead), Cu (copper) or the like can be adopted.

The thickness of the metal layer 4 formed on the tab 2b of the lead frame main body 2 is set to 15 μm or less.

This is because the plating of the inner leads 2a of the lead frame main body 2 and the plating for forming the metal layer 4 on the tab 2b are performed on the same line, so that the thickness of the metal layer 4 is reduced. By setting the plating thickness to be the same as that of the inner lead, the thickness of the Ag plating required for performing wire bonding is adjusted to 15 μm or less so that a lead frame can be efficiently produced. Things.

When the thickness of the metal layer 4 is set to 15 μm or more, there is a concern that the Ag particles may become large, and the strength may be reduced due to the increase in the size of the Ag particles.
When the lead frame body 2 and the heat sink 3 are overlapped,
There is a risk that the plating will peel off due to the impact,
In addition, since there is a problem such as so-called plating burn caused by increasing the heat input to improve the work efficiency of plating, the thickness of the metal layer 4 is set to 15 μm or less for the purpose of suppressing these inconveniences. It is.

As shown in FIG. 3A, after a metal layer 4 made of Ag (silver) is formed on the tab 2b of the lead frame main body 2, as shown in FIG. On the stage block B, the lead frame main body 2 and the heat sink 3 are overlapped, and the metal layer 4 formed on the tab 2 b is brought into contact with the upper surface of the corner of the heat sink 3.

Thereafter, the ultrasonic horn C of the ultrasonic bonding machine A applies ultrasonic waves while pressing the lead frame main body 2 and the heat radiating plate 3, more specifically, the metal layer 4 formed on the tab 2 b and the heat radiating plate 3 with each other. By applying the lead frame main body 2
And the heat sink 3 are joined to each other, whereby the lead frame 1 is manufactured.

At this time, the joining portion between the lead frame body 2 and the heat sink 3 is a metal bond between Ag (silver) forming the metal layer 4 and the copper-based material forming the heat sink 3.
The output (energy) of the ultrasonic wave applied to the joining portion can be reduced as compared with the case where the copper-based materials are joined by ultrasonic bonding.

As described above, since a large amount of energy is not required for joining the lead frame body 2 and the heat sink 3,
The operation involved in manufacturing the lead frame 1 is not complicated, and the ultrasonic bonding machine A is not increased in size.

Further, since ultrasonic waves having a large energy are not applied to the joint, no major damage is given to the lead frame main body 2 and the heat radiating plate 3, thereby preventing the lead from being deformed or damaged. It is possible to do.

On the other hand, the lead frame 10 of the present invention shown in FIG. 4 includes a lead frame main body 20 and a radiator plate 30 joined to the lead frame main body 20.

The lead frame body 20 is formed by punching or etching a thin copper-based metal plate, has a pad 20a in the center, and has a number of inner leads 20b surrounding the periphery of the pad 20a. ., And the center pad 20a is provided with inner leads 20b, 20b.
0 to prevent contact with the inner lead 20.
b, 20b ... a position one step lower (backward in FIG. 4)
It is in.

On the other hand, the heat radiating plate 30 is formed by punching and forming a thin copper-based metal plate similarly to the lead frame main body 20, and has a rectangular shape slightly larger than the pad 20a in the lead frame main body 20. Present.

As shown in FIG. 5, the pad 20a of the lead frame main body 20 has an excellent bonding property in ultrasonic bonding to a copper-based metal which is a material of the heat radiating plate 30, in other words, an ultra-high energy bonding. A metal layer 40 made of Ag (silver) that is joined to the heat radiating plate 30 without forming a sound wave is formed by plating, and the lead frame 10 is connected to the lead frame main body 20 via the metal layer 40. And the heat sink 30 are ultrasonically bonded to each other.

To manufacture the lead frame 10 having the above structure, first, as shown in FIG.
0 on the back surface of the pad 20a by plating.
A metal layer 40 made of (silver) is formed.

The pad 2 of the lead frame body 20
The thickness of the metal layer 40 formed at 0a is 15 μm for the same reason as described in detail for the lead frame 1 of FIG.
It is set as follows.

The material of the metal layer 40 formed on the tab 2b of the lead frame main body 2 is, for example, Ni (nickel), Pd (balladium), Au, in addition to Ag (silver) described above.
Of course, (gold), Pb (lead), Cu (copper) and the like can be adopted.

As shown in FIG. 6A, after a metal layer 40 made of Ag (silver) is formed on the pad 20a of the lead frame main body 20, as shown in FIG. On the stage block B, the lead frame body 2
Then, the metal layer 40 formed on the pad 20a is brought into contact with the upper surface of the central portion of the heat sink 30 by superimposing the heat sink 30 on the heat sink 30.

Thereafter, the ultrasonic horn C of the ultrasonic bonding machine A applies ultrasonic waves while pressing the lead frame body 20 and the heat radiating plate 30, specifically, the metal layer 40 formed on the pad 20a, and the heat radiating plate 30 to each other. By applying the voltage, the lead frame main body 20 and the heat sink 30 are joined to each other, whereby the lead frame 10 is manufactured.

At this time, the joint between the lead frame main body 20 and the heat sink 30 is made of Ag (silver) constituting the metal layer 40.
And a metal bond with the copper-based material constituting the radiator plate 30, compared with a case where the copper-based materials are ultrasonically bonded to each other.
The output (energy) of the ultrasonic wave applied to the joint portion can be reduced.

As described above, since a large amount of energy is not required for joining the lead frame main body 20 and the heat radiating plate 30, the work involved in manufacturing the lead frame 10 becomes complicated, and the ultrasonic joining machine A becomes large. I will not invite you.

Further, since high-energy ultrasonic waves are not applied to the joint, the lead frame main body 20 is not required.
In addition, it is possible to prevent the lead from being deformed or damaged without causing significant damage to the heat sink 30.

The lead frame 1 shown in FIG. 1 and the lead frame 10 shown in FIG. 4 are both connected to the lead frame main body 2 and the lead frame main body 20 by Ag (silver).
The metal layer 4 and the metal layer 40 made of
The metal layer only needs to be formed on at least one of the lead frame main body and the heat sink.
Needless to say, a metal layer can be formed on the heat sink 30.

Further, depending on the conditions such as the materials of the lead frame main body and the heat radiating plate, it is possible to form a metal layer on both the lead frame main body and the heat radiating plate. , One metal layer is made of Cu (copper), the other metal layer is made of Ag (silver), etc.
It goes without saying that one of the metal layers is made of a metal having excellent bonding properties in ultrasonic bonding to the other metal layer.

[0034]

As described above in detail, the lead frame according to the present invention has at least one of the lead frame main body and the heat radiating plate formed with a metal layer having excellent bonding properties in ultrasonic bonding to the other material. The lead frame body and the heat sink are ultrasonically bonded to each other via the metal layer. Further, a method for manufacturing a lead frame according to the present invention includes a step of forming a metal layer having excellent bonding properties in ultrasonic bonding on at least one of a lead frame main body and a heat sink, And a step of joining the lead frame body and the heat sink to each other by ultrasonically joining the lead frame body and the heat sink through the substrate. According to the configuration of the present invention as described above, when the lead frame main body and the heat sink are ultrasonically joined, the output (energy ) Can be kept small. Therefore, according to the lead frame and the manufacturing method thereof according to the present invention, since the output of the ultrasonic wave applied at the time of ultrasonic bonding can be suppressed, the damage to the lead frame main body and the heat radiating plate can be suppressed, so that the deformation of the lead and It is possible to prevent the occurrence of breakage and the like beforehand, and it is not necessary to complicate the operation related to the manufacture of the lead frame or to increase the size of the ultrasonic bonding machine.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIGS. 3A and 3B are conceptual diagrams sequentially illustrating a method of manufacturing a lead frame according to the present invention.

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

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIGS. 6A and 6B are conceptual diagrams sequentially illustrating another method of manufacturing a lead frame according to the present invention.

FIG. 7 is a conceptual diagram showing a conventional lead frame manufacturing mode using an ultrasonic bonding machine.

[Explanation of symbols]

 1, 10: lead frame, 2, 20: lead frame main body, 3, 30: heat sink, 4, 40: metal layer.

Claims (2)

[Claims] 1. A lead frame in which a lead frame main body and a heat sink are joined to each other by ultrasonic bonding, wherein at least one of the lead frame main body and the heat sink is ultrasonically bonded to the other material. A lead frame, comprising: forming a metal layer having excellent bonding properties in the above, and ultrasonically bonding the lead frame main body and the heat sink to each other via the metal layer. 2. A method for manufacturing a lead frame, comprising joining a lead frame main body and a heat radiating plate to each other by ultrasonic bonding, wherein at least one of the lead frame main body and the heat radiating plate is provided with respect to the other material. A step of forming a metal layer having excellent bondability in ultrasonic bonding, and ultrasonically bonding the lead frame main body and the heat sink through the metal layer, thereby connecting the lead frame main body and the heat sink. Bonding the lead frame to each other.