JP2000026926A - Composite material for lead frame and semiconductor package using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an inexpensive base stock for a lead frame provided with mechanical strength that a lead material is not easily deformed, capable of radiating the heat generation of an element with high efficiency, excellent in electric characteristics and good in etching and punching properties needed for the pattern formation of a lead frame, to provide a method for producing it and to provide a semiconductor package using it. SOLUTION: A lead frame 1 is formed from a composite material for a lead frame by punching or etching. The composite material for a lead frame is a composite rolled material contg. copper(Cu) and >=50 wt.% molybdenum(Mo) and has 40 to 250 μm sheet thickness, 160 to 250 W/m k thermal conductivity, 180 to 280 GPa Young's modulus, <=11×10-6/K thermal expansion coefficient and <=10 g/cm3 density. For producing this composite material for a lead frame, powder obtd. by sufficiently mixing Cu powder of <=30 μm and Mo powder of 2 to 6 μm so as to contain copper(Cu) and >=50 wt.% molybdenum(Mo) is mixed with a binder, and kneaded sufficiently, and, after that, it is subjected to extrusion molding, sintering and cold rolling or warm rolling to obtain a Cu-Mo composite rolled material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a Cu-Mo composite material used for a lead frame, a method of manufacturing the same, and a semiconductor package using the same.

[0002]

2. Description of the Related Art In the field of semiconductors, high density and high speed of IC chips are increasingly promoted, and as a result, the number of pins and the pitch of chips are increased, and the unit density per unit volume is increased due to the improvement of integration. Since Joule heat increases, it is necessary to radiate heat more efficiently.

In order to efficiently dissipate heat generated in semiconductor elements, Cu and Cu-based composite materials are often used as element mounting board materials. -The role played by the frame has become increasingly important, and it is necessary that the material has not only electrical characteristics but also high heat dissipation.

[0004]

Generally, a lead frame material of a semiconductor device has (a) a mechanical strength such that the lead material is not easily deformed, and (a) heat is efficiently dissipated with respect to heat generated by the element. (C) excellent electrical properties, (d) good etching and punching properties required for forming a lead frame pattern,
(E) It is required to be inexpensive.

[0005] Therefore, Cu or Cu alloy, Fe-
Ni alloys or Fe alloys are mainly used, but each has advantages and disadvantages, and it is difficult to satisfy all the above characteristics. That is, although Cu has excellent electrical conductivity and thermal conductivity, it has a large coefficient of thermal expansion and is inferior in strength. Although Cu alloys and Fe-based alloys have excellent mechanical strength, their thermal conductivity is as low as several tens of W / m · K or less, which is considerably inferior in terms of heat dissipation.

On the other hand, Cu, which has excellent conductivity and thermal conductivity characteristics, and Mo, which has high mechanical strength and a thermal expansion coefficient close to that of Si,
There is disclosed a Cu-Mo composite material which is a metal composite material utilizing the characteristics of both, and which is mainly used for a heat dissipation substrate mounted on an IC package.

However, in this method, the thickness (T) is 100 μm.
It is evident that the production of a plate having a length of about m requires a considerable increase in the number of times of rolling, which leads to an increase in the production cost.
It is not suitable as a production method because the o-particles are elongated and the anisotropy of the coefficient of thermal expansion in particular increases.

Accordingly, it is an object of the present invention to provide a lead frame material which satisfies all of the above requirements (A) to (E), a method of manufacturing the same, and a semiconductor package using the same. is there.

[0009]

According to the present invention, copper (C
u) and at least 50% by weight of molybdenum (Mo), a composite rolled material having a thickness of 40 to 250 μm and a thermal conductivity of 16
0-250W / m · K, Young's modulus 180-280GP
a, Coefficient of thermal expansion 11 × 10 ⁻⁶ / K or less and density 10 g
/ Cm ³ or less, a composite material for a lead frame is obtained.

According to the present invention, the composite material for a lead frame is made of a rolled Cu-Mo composite material,
Mo in each of the rolling (Y) direction and the rolling vertical (X) direction
Ratio of particle aspect ratio (L / W) [(L / W) _Y /
(L / W) _X ] is 2 or less and the anisotropy of the thermal expansion coefficient is 1.
A composite material for a lead frame, which is not more than 5 × 10 ⁻⁶ / K, is obtained.

In a semiconductor package having a lead frame on which semiconductor components are mounted, the lead frame is made of copper (Cu) and 50% by weight or more of molybdenum (M).
a rolled Cu-Mo composite material containing o), having a thickness of 40 to
250 μm, thermal conductivity 160 to 250 W / m · K, Young's modulus 180 to 280 GPa, coefficient of thermal expansion 11 × 10 −6
/ K and a density of 10 g / cm ³ or less can be obtained.

Further, according to the present invention, in the semiconductor package, the Cu-Mo composite rolled material has an aspect ratio (L / W) of Mo particles in a rolling (Y) direction and a rolling perpendicular (X) direction. Ratio [(L / W) _Y / (L
/ W) _X ] is 2 or less and the anisotropy of the thermal expansion coefficient is 1.5 ×
A semiconductor package characterized by being at most 10 ⁻⁶ / K is obtained.

Further, a Cu powder of 30 μm or less and 2-6 μm
m, and a binder obtained by adding a binder to a powder obtained by sufficiently mixing copper (Cu) and molybdenum (Mo) by 50% by weight or more, extruding, sintering, and cold rolling or hot rolling. A method for producing a composite material for a lead frame, characterized by obtaining a Cu-Mo composite rolled material by cold rolling.

According to the present invention, in the method for producing a composite material for a lead frame, the Cu-Mo composite rolled material may have a thickness of 40 to 250 μm and a thermal conductivity of 160 to 25.
0 W / mK, Young's modulus 180 to 280 GPa, coefficient of thermal expansion 11 × 10 ⁻⁶ / K or less, and density 10 g / cm ³ or less. can get.

Further, according to the present invention, in any of the above-mentioned methods for producing a composite material for a lead frame, the cold rolling or the warm rolling is performed by using the rolling (Y) direction and rolling of the Cu—Mo composite rolled material. The ratio of the aspect ratio (L / W) of each Mo particle in the vertical (X) direction [(L / W) _Y / (L
/ W) _X ] is 2 or less and the anisotropy of the thermal expansion coefficient is 1.5 ×
A method for producing a composite material for a lead frame, which is performed so as to be 10 ⁻⁶ / K or less, is obtained.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a semiconductor package according to an embodiment of the present invention. FIG. 2 is a top view showing a lead frame used in the semiconductor package of FIG.

Referring to FIG. 1, a semiconductor package 10
Is a stage unit 2 on which a semiconductor (IC) chip 1 is mounted.
A lead frame main body 6 including a lead frame base 3, an outer lead terminal 4 extending outward from the lead frame base 3, and an inner lead terminal 5 extending inward from the lead frame base 3, and a semiconductor chip 1 And a mounting board 8 that covers these while leaving the outer lead terminal 4.

Referring to FIG. 2, the lead frame 11
Is formed from a thin and long plate-like material for a lead frame by punching integrally with a press or by etching while having the carrier portion 12 and the connecting portion 13. The carrier part 12 and the connection part 13 are cut off when the semiconductor package 10 is formed.

In the lead frame according to the embodiment of the present invention, after the Cu powder and the Mo powder mixed in a desired ratio are sufficiently mixed uniformly, a water-soluble binder, a plasticizer and pure water are added and kneaded sufficiently. After extrusion molding, a thin plate of T40 to 250 μm obtained by a production method of debinding, sintering and rolling is used as a lead frame material.

The Cu content of the lead frame material is 10 to 50% by mass, with the remainder being Cu-Mo
Composites are suitable due to their thermal conductivity, coefficient of thermal expansion and rigidity.

Further, the lead frame often comes into contact with air, and cannot be used as a heat radiation material unless it is 150 W / m · K or more. With the recent increase in density,
160 to 170 W / mK or more is desirable.

Table 1 below shows a comparison of various characteristics between the present typical lead frame material and the present invention. Alloy 42 is a commonly used Fe-42% Ni alloy, and has a tensile strength of 600 MPa compared to a high-strength Cu alloy.
As described above, the high-conductivity-type Cu alloys are those having 75% IACS or more, and representative examples thereof are shown.

The products of the present invention are all excellent in thermal conductivity, coefficient of thermal expansion, Young's modulus, conductivity and the like. Also, 4
Compared with Alloy 2, the coefficient of thermal expansion is slightly larger, but is superior to other properties. Looking at the characteristics of the high-strength Cu alloy,
The characteristic value of -Mo of 30% by mass or less is almost equal to that of the high-conductivity-type Cu alloy, but is lower than the conductivity, but the other characteristic values are excellent. It turns out that it is quite excellent as a lead frame material.

[0025]

[Table 1]

The product of the present invention is manufactured by the extrusion method disclosed in JP-A-7-307422 so as to be suitable as a lead frame material as follows.

To a Mo powder having an average particle size (Fsss) of 2 to 6 μm, 10 to 50% by mass of a Cu powder having a particle size of 30 μm or less is added and mixed sufficiently and uniformly. This mixed powder is kneaded with methyl cellulose having good tensile strength and debinding property as a binder, industrial propylene glycol as a surfactant, and pure water as a solvent. For kneading, the mixture is passed through a kneader several times, and then passed through a three roll about 10 times to sufficiently spread the binder and to give the Mo particles an orientation. And the thickness (T) is 0.1 to 1.8 mm, desirably, T
Extrusion is performed at 0.2 to 1.2 mm to obtain a green body. After sufficiently removing the binder from the green body, the sintered material is rolled to obtain a dense plate having a T of 40 to 250 μm. The aspect ratio of Mo particles of this rolled sheet (longest diameter /
Shortest Kai: L / W) in parallel to the rolling direction (Y) direction of the aspect ratio (L / W) _Y to the rolling direction in the vertical (X) direction of the aspect ratio (L / W) ratio of _X [(L / W) _Y
/ (L / W) _X ] is 2 or less, the anisotropy of the thermal expansion coefficient is 1.5 × 10 ⁻⁶ / K or less, and the surface roughness Ra ≦ 0.1 μm.
m, Rmax ≤ 1 are obtained.

If the anisotropy and the surface roughness of the thermal expansion coefficient of the lead frame material are at the above-mentioned levels and the characteristics shown in Table 1 above, heat is generated at the time of assembling the semiconductor device or generated during operation. It can be said that the material does not decrease in bonding strength due to heat or the like and can withstand shocks such as deformation and vibration due to heat.

It is also important that the punching property or etching property required for the lead frame material is good or bad.

Here, since the punching is sufficiently densified with Cu and Mo, cracks and cracks are not generated on the side surface and the surface, and the punching is favorable. On the other hand, the etching property requires technology because Cu and Mo are mixed,
There is no problem as disclosed in JP-A-91.

Hereinafter, a specific example of manufacturing a composite rolled material for a lead frame according to the embodiment of the present invention will be described.

Example 1 M having an average particle size (Fsss) of 3 μm
10% by mass of the same 8 μm electrolytic Cu powder is added to the o powder and mixed sufficiently and uniformly. To this mixed powder, methylcellulose as a binder, propylene glycol for industrial use as a surfactant, and pure water were mixed and kneaded. For kneading, the mixture was passed through a kneader three times, and then passed three times through three rolls to sufficiently spread the binder to obtain a high viscosity slurry. The kneaded material was extruded with a thickness (T) of 1.2 mm to obtain a green body. After sufficiently debinding the green body, the sintered material was rolled green at a rolling rate of 10% or less, and T250 μm A plate was obtained.

The aspect ratio (L / W) _{Y in the} direction parallel to the rolling direction (Y) of the Mo particles of the rolled sheet (L / W) _Y = 3.4, and the aspect ratio in the direction (X) perpendicular to the rolling direction (L / W) _X =
2.0, and their ratio [(L / W) _Y / (L /
W) _X ] = 1.7. At this time, the anisotropy of the thermal expansion coefficient in the Y and X directions was 1.3 × 10 ⁻⁶ / K. The surface roughness was Ra ≦ 0.1 μm and Rmax ≦ 1 μm.
In addition, thermal conductivity 163W / m · K, tensile strength 780MP
a, A material having a Young's modulus of 280 GPa, good heat dissipation, and high strength was obtained.

The obtained plate was processed into a lead frame having the shape shown in FIGS. 1 and 2 by double-sided etching.
There was no deformation due to the etching process, the side etch was 50 μm, and there was no problem in practical use.

(Example 2) The same Mo powder and Cu as in Example 1
The powders are mixed in a ratio of 7: 3 and mixed sufficiently and uniformly.
This mixed powder was mixed with the same binder, surfactant and pure water as in Example 1 and kneaded. For kneading, the mixture was passed twice through a kneader and then passed through a three-roll mill seven times to sufficiently spread the binder to form a high-viscosity slurry. This kneading material is
Extrusion was carried out at 0.8 mm to obtain a green body.
Rolling was repeated at a rolling reduction of 0% or less to obtain a T150 μm plate.

The aspect ratio of the Mo particles (L
/ W) _Y = 3.1, (L / W) _X = 2.1, and their ratio [(L / W) _Y / (L / W) _X ] = 1.5. At this time, the anisotropy of the coefficient of thermal expansion in the Y and X directions was 1.2 × 10 ⁻⁶ / K.

The surface roughness is Ra ≦ 0.1 μm, Rmax ≦
It was 1 μm. In addition, a material having good heat dissipation properties and high strength properties was obtained with a thermal conductivity of 190 W / m · K, a tensile strength of 660 MPa, and a Young's modulus of 220 GPa.

The obtained plate was processed into a lead frame having the shape shown in FIG. 1 by double-sided etching. There was no deformation due to the etching process, and the side etch was 30μ.
m, and there was no problem in practical use.

(Example 3) The same Mo powder and Cu as in Example 1
The powders are mixed at a ratio of 1: 1 and mixed sufficiently and uniformly.
This mixed powder was mixed with the same binder, surfactant and pure water as in Example 1 and kneaded. For kneading, the mixture was passed twice through a kneader, and then passed three times through a three-roll mill to sufficiently spread the binder to form a high-viscosity slurry. This kneaded material was added to T0.
Extrusion was performed at 2 mm to obtain a green body, and after sufficiently debinding the green body, the sintered material was reduced to 10%.
Rolling was repeated at the following rolling rates to obtain a T40 μm plate.

The aspect ratio (L) of the Mo particles in the rolled sheet
/ W) _Y = 3.2, (L / W) _X = 1.9, and their ratio [(L / W) _Y / (L / W) _X ] = 1.7. At this time, the anisotropy of the thermal expansion coefficient in the Y and X directions was 1.5 × 10 ⁻⁶ / K. The surface roughness is Ra ≦ 0.
1 μm, Rmax ≦ 1 μm. In addition, the thermal conductivity 25
0W / m · K, tensile strength 530MPa, Young's modulus 180
A material having good heat dissipation and good strength with GPa was obtained.

The obtained plate material was processed into a lead frame having the shape shown in FIG. 1 by double-sided etching. There was no deformation due to the etching process, and the side etch was 8 μm, and there was no problem in practical use.

[0042]

As described above, according to the present invention,
With mechanical strength so that the lead material does not easily deform,
An inexpensive lead frame material that can efficiently dissipate the heat generated by the element, has excellent electrical characteristics, has good etching and punching properties required for forming a lead frame pattern, and is inexpensive. And a semiconductor package using the same.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a view showing a lead frame used for the semiconductor package shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor (IC) chip 2 Stage part 3 Lead frame base 4 Outer lead part terminal 5 Inner lead part terminal 6 Lead frame main body 7 Bonding wire 8 Mounting board 11 Lead frame

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C22C 9/00 C22C 9/00 C22F 1/00 627 C22F 1/00 627 628 628 661 661A 685 685A 685Z 687 687 (72) Inventor Akira Ichida 2nd Iwase Koshimachi, Toyama City, Toyama Prefecture Tokyo Tan Gusten Co., Ltd. Toyama Works F term (reference) 4K018 BA02 BA09 BC12 CA07 CA31 EA52 FA01 5F067 AA03 EA00

Claims (7)

[Claims] 1. A composite rolled material containing copper (Cu) and 50% by weight or more of molybdenum (Mo), having a thickness of 40 to 25.
For a lead frame, comprising a composite material having a thickness of 0 μm, a thermal conductivity of 160 to 250 W / m · K, a Young's modulus of 180 to 280 GPa, a thermal expansion coefficient of 11 × 10 ⁻⁶ / K or less, and a density of 10 g / cm ³ or less. Composite materials. 2. The composite material for a lead frame according to claim 1, wherein the composite material comprises a rolled Cu—Mo composite material and is rolled (Y).
Of the aspect ratio (L / W) of Mo particles in the vertical direction and the rolling perpendicular (X) direction [(L / W) _Y / (L / W)
_X ] is 2 or less, and the anisotropy of thermal expansion coefficient is 1.5 × 10 ⁻⁶
/ K or less. 3. A semiconductor package having a lead frame on which a semiconductor component is mounted, wherein the lead frame is made of copper (Cu) and molybdenum (Mo) of 50% by weight or more.
And a Cu-Mo composite rolled material containing:
0 μm, thermal conductivity 160 to 250 W / m · K, Young's modulus 180 to 280 GPa, coefficient of thermal expansion 11 × 10 −6 / K
And a density of 10 g / cm ³ or less. 4. The semiconductor package according to claim 3, wherein the Cu—Mo composite rolled material has an aspect ratio (L / W) of Mo particles in each of a rolling (Y) direction and a rolling perpendicular (X) direction. [(L / W) _Y / (L / W) _X ] is 2
A semiconductor package having an anisotropy of thermal expansion coefficient of 1.5 × 10 ⁻⁶ / K or less. 5. A binder obtained by adding a binder to a powder obtained by sufficiently mixing Cu powder of 30 μm or less and Mo powder of 2 to 6 μm so as to contain copper (Cu) and 50% by weight or more of molybdenum (Mo), A method for producing a composite material for a lead frame, comprising extruding, sintering, and cold rolling or warm rolling to obtain a Cu-Mo composite rolled material. 6. The method for manufacturing a composite material for a lead frame according to claim 5, wherein the Cu—Mo composite rolled material has a thickness of 40 to 250 μm and a thermal conductivity of 160 to 250 W / m ·.
K, Young's modulus 180-280 GPa, coefficient of thermal expansion 11 ×
A method for producing a composite material for a lead frame, comprising characteristics of 10 ⁻⁶ / K or less and a density of 10 g / cm ³ or less. 7. The method for manufacturing a composite material for a lead frame according to claim 5, wherein the cold rolling or the warm rolling is performed by a rolling (Y) direction and a rolling vertical (X) of the Cu—Mo composite rolled material. ) Direction, the ratio [(L / W) _Y / (L / W) _X ] of the aspect ratio (L / W) of each Mo particle is 2
A method for producing a composite material for a lead frame, wherein the anisotropy of the thermal expansion coefficient is set to 1.5 × 10 ⁻⁶ / K or less.