JP3014673B2 - Lead frame for semiconductor device - Google Patents

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 semiconductor device such as an IC having excellent punching workability, corrosion resistance and bending workability.

[0002]

2. Description of the Related Art Conventionally, lead frame materials and terminal materials of semiconductor devices have been made of iron-based materials and copper-based alloys such as Cu-Sn-based alloys and Cu-Fe-based alloys having excellent electrical and thermal conductivity. System materials are widely used.

[0003] By the way, in addition to the strength, heat resistance, electric conductivity, and heat conductivity, the lead frame material and the like include
Since noble metal (Ag or the like) plating or solder plating is applied, characteristics such as plating properties, solder bonding properties, and surface smoothness are emphasized. In addition, in order to ensure dimensional accuracy when molding a lead frame from a strip and a plate, it is required that etching workability or punching workability be good. Furthermore, it is important that price is practical, and these characteristics are increasingly required as semiconductor devices become more integrated, smaller, more functional, and less costly. ,
Correspondingly, lead frames are becoming more multi-pin, smaller, thinner, etc., and among them, fine-pitch lead frames and matrix-type lead frames with fewer pins but processed in multiple rows will be developed. It has become.
Since these lead frames are manufactured by a high-precision, low-cost punching method, it is strongly required that lead frame materials have improved punching workability.

[0004]

The above-mentioned Cu-Sn-based alloy and Cu-Fe-based alloy are inferior in punching workability.
As an alternative, a Cu-Zn-based alloy has been proposed (Japanese Patent Laid-Open No. 1-162737), but this alloy is excellent in punching workability but has a problem that it is inferior in stress corrosion cracking resistance. Was.

Therefore, Ni and Pd are deposited on a Cu—Zn alloy.
Have been proposed in order to improve the stress corrosion cracking resistance (JP-A-5-36878). But,
This material has a thickness of 0.01 because the Pd layer is expensive.
If the thickness is reduced to about μm, sufficient corrosion resistance will not be obtained, and if the lead is bent, cracks will occur in the plating layer, and the alloy base will be exposed or the tie bar cut will expose the alloy base. And stress corrosion cracking. Also, punching workability was insufficient for a multi-pin lead frame having 100 pins or more. Further, the occurrence of cracks in the plating layer may be caused by cracks in the base material (copper alloy), and improvement in bending workability of the copper alloy itself has been required.

[0006] The present invention has been made under such circumstances,
Punching workability, corrosion resistance, bending workability, stress corrosion cracking resistance,
An object of the present invention is to provide a lead frame for a semiconductor device which is excellent in strength, conductivity, processability, and the like.

[0007]

In order to solve the above-mentioned problems, the present invention (claim 1) provides that Zn is 5 to 35 wt%,
0.1-3 wt% of Sn , Pb, Bi, Se, Te, C
one selected from the group consisting of a, Sr and rare earth elements
Or contain two or more kinds in total of 0.001 to 0.5 wt% ,
The content of both O and S is 50 ppm or less,
The balance consists of Cu and unavoidable impurities, and the grain size is 5 to 5.
Pd of 0.01 μm or more on a 35 μm copper alloy member
A lead frame for a semiconductor device characterized by being formed in a layered thickness .

In the present invention (claim 2), the Zn content is 5 to 5.
Pb, B containing 35 wt%, Sn containing 0.1 to 3 wt%
i, Se, Te, Ca, Sr and one or more selected from the group consisting of rare earth elements in a total of 0.001 to
0.5wt%, Ni, Si, Cr, Zr, F
a group consisting of e, Co, Mn, Al, Ag, Mg and P
One or more selected from a total of 0.001 to 1
wt%, O and S content are both 50ppm
Or less, and the balance of Cu and unavoidable impurities, on the copper alloy member of grain size 5 to 35 m, Pd is 0.0
A lead frame for a semiconductor device, wherein the lead frame is formed in a layer having a thickness of 1 μm or more .

Further, according to the present invention (claim 3), Zn
35 wt%, Sn is 0.1-3 wt%, Pb, Bi, S
e, Te, Ca, Sr and one or more selected from the group consisting of rare earth elements in total of 0.001 to 0.5
wt%, O and S content are both 50ppm
Or less, and the balance of Cu and unavoidable impurities, on the copper alloy member of grain size 5 to 35 m, Pd is 0.0
A lead frame for a semiconductor device characterized by being formed in a layer having a thickness of 1 to 0.15 μm. Ma
In addition, the present invention (claim 4) is based on the followings.
n is 0.1 to 3 wt%, Pb, Bi, Se, Te, C
one selected from the group consisting of a, Sr and rare earth elements
Or contain two or more kinds in total of 0.001 to 0.5 wt%,
Further, Ni, Si, Cr, Zr, Fe, Co, Mn, A
one selected from the group consisting of 1, Ag, Mg and P or
Contains 0.001 to 1 wt% in total of two or more,
And the content of S is 50 ppm or less, and the balance is
Consisting of Cu and unavoidable impurities, with a crystal grain size of 5-35 μm
m on a copper alloy member having a Pd of 0.01 to 0.15 μm
A semiconductor device characterized by being formed in a layer having a thickness.
A mounting lead frame is provided.

[0010] The present invention (claim 5 ) provides that
35 wt%, Sn is 0.1-3 wt%, Pb, Bi, S
from the group consisting of e, Te, Ca, Sr and rare earth elements
One or more selected ones are 0.001-0.5 in total
wt%, O and S content are both 50ppm
The remainder is composed of Cu and unavoidable impurities.
On a copper alloy member having a crystal grain size of 5-35 μm,
1 μm or more (excluding 0.2 μm or more)
A semiconductor device package formed in a layer shape.
Provide a code frame. The present invention (claim 6)
Is Zn of 5 to 35 wt%, Sn of 0.1 to 3 wt%,
Pb, Bi, Se, Te, Ca, Sr and rare earth elements
One or more selected from the group consisting of
001-0.5wt%, Ni, Si, Cr, Z
from r, Fe, Co, Mn, Al, Ag, Mg and P
One or more selected from the group consisting of a total of 0.00
1 to 1 wt%, and the content of O and S is 50
ppm or less, with the balance being Cu and unavoidable impurities.
Pd is formed on a copper alloy member having a crystal grain size of 5 to 35 μm.
0.01 μm or more (excluding 0.2 μm or more)
A semiconductor device characterized by being formed in a layer having a thickness.
A mounting lead frame is provided.

The present invention (claim 7 ) provides the above-described lead frame for a semiconductor device (claims 1 to 6 ) wherein Ni, Co, Ni-Co alloy, and Ni-Co alloy are provided between the copper alloy and the Pd layer. One or more selected from the group consisting of Ni-Pd alloys are formed in layers. Also, the present invention (claim 8) provides the above-described semiconductor device.
In the lead frame (claims 1 to 7), the crystal grain
The degree is 5 to 30 μm.

The lead frame for a semiconductor device according to the first invention is characterized in that a Pd layer is formed on a Cu-Zn-Sn-based copper alloy member having a predetermined grain size.
In such a semiconductor device lead frame, Zn contained in the copper alloy has an effect of suppressing the generation of burrs and the twisting of the leads during the punching process. 5 to 3
The reason for specifying 5 wt% is that if it is less than 5 wt%, the effect of the present invention cannot be sufficiently obtained, and if it exceeds 35 wt%, a β phase appears and the cold workability deteriorates.

Sn contributes to improvement in strength, improvement in stress corrosion cracking resistance, and improvement in corrosion resistance after Pd plating. The reason for defining the content to be 0.1 to 3% by weight is as follows.
If it is less than 3 wt%, the effect of the present invention cannot be sufficiently obtained, and 3 w
If the content exceeds t%, the conductivity and the hot workability decrease. The preferred Sn content is 0.1 to 2 wt%.
It is.

In the present invention, the crystal grain size of the copper alloy is 5 to 3
The reason for specifying 5 μm is that even if the crystal grain size is less than 5 μm,
This is because even if it exceeds 35 μm, the effect of improving the bending workability cannot be sufficiently obtained. The crystal grain size is JIS-H
It shall be measured according to 0501. The preferred crystal grain size of the copper alloy is 10 to 30 μm.

The inventors of the present invention conducted various studies on the cause of poor bending workability of a conventional alloy (Cu-Zn-based alloy) and found out that it was caused by the grain size. It was made after further research.

The Pd layer formed on the copper alloy member has an effect of improving stress corrosion cracking resistance, wire bonding properties, and solder wettability. This Pd layer has a thickness of 0.
The effect is sufficiently exhibited when the thickness is 01 μm or more. Pd
The upper limit of the thickness of the layer is not particularly specified, but if the thickness is increased to 1 μm or more, the effect is saturated and processing cost and material cost are increased, which is uneconomical.

[0017] In the first semiconductor device lead frame according to the invention, Pb to be al, Bi, Se, Te, Ca , Sr
And one or two selected from the group consisting of rare earth elements
More than one kind is contained to improve the punching workability. The reason that the content is defined as 0.001 to 0.5 wt% in total is that if the content is less than 0.001 wt%, the effect of the present invention cannot be sufficiently obtained. Is to be reduced.

In the lead frame for a semiconductor device according to the second invention, the copper alloy according to the first invention further includes Ni,
Si, Cr, Zr, Fe, Co, Mn, Al, Ag, M
One or two or more selected from the group consisting of g and P are contained to increase the alloy strength and thereby improve the punching workability. The total content is 0.00
The reason for defining the content to be 1 to 1 wt% is that if the content is less than 0.001 wt%, the effect of the present invention cannot be sufficiently obtained, and if the content exceeds 1 wt%, the conductivity and the hot workability are reduced.

As additional elements effective for improving the strength and heat resistance of the copper alloy in the first and second inventions, Ti, I
n, Ba, Sb, Hf, Be, Nb, Pd, B, C and the like. The addition amount is desirably in a range that does not significantly lower the conductivity. Further, when the content of O and S mixed at the time of melting and casting is set to 50 ppm or less, the plating property,
Good surface properties such as solder jointability and solder wettability are maintained.

In the lead frame for a semiconductor device according to the present invention, Ni, Co, Ni-Co is provided between the copper alloy and the Pd layer.
By forming one or more selected from the group consisting of a base alloy and a Ni-Pd base alloy in a layered form, the resistance to stress corrosion cracking is improved. Further, even when the semiconductor device is assembled at a high temperature, the diffusion of Cu or Zn of the copper alloy into the Pd layer is suppressed, and the wire bonding property and the solder wettability are well maintained. By forming such an intermediate layer, the Pd layer can be thinned without deteriorating the reliability, and the cost can be reduced. The effect of the intermediate layer is sufficiently exhibited when the thickness is 0.1 μm or more.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to various embodiments of the present invention. (Example 1) Copper alloys having the compositions shown in Tables 1 and 2 below were melted in a high-frequency melting furnace and cast at a cooling rate of 6 ° C / sec to obtain a thickness of 30 mm, a width of 200 mm, and a length of 300 m.
m was obtained.

Next, the ingot was hot-rolled at 850 ° C. to obtain a hot-rolled plate having a thickness of 12 mm.
To remove the oxide film, and then to a thickness of 1.
After cold rolling to 2 mm, 53
After annealing at 0 ° C. for 1 hour and further cold rolling to a thickness of 0.21 mm, annealing at 530 ° C. for 1 hour in an inert gas,
Then, it was finish-rolled into a 0.15 mm thick plate.

For each of the thus obtained sheet materials, (1) tensile strength (TS), (2) electric conductivity (EC),
(3) punching workability and (4) bending workability were examined. Also,
A 28-pin DIP lead frame was punched from the plate material, Ni was electroplated on the lead frame to a thickness of 0.5 μm, and Pd was further electroplated on the lead frame to a thickness of 0.01 μm. The lead frame samples thus obtained were examined for (5) stress corrosion cracking resistance and (6) corrosion resistance. The results are shown in Tables 3 and 4 below.

In Table 1 below, Pb, Bi, Se,
The group consisting of Te, Ca, Sr and the rare earth element is referred to as a first group additive element, Ni, Si, Cr, Zr, Fe, Co, M
The group consisting of n, Al, Ag, Mg and P was described as a second group additional element.

The test methods (1) to (6) are described below. (1) Tensile strength (TS): Measured according to JIS-Z2241. (2) Conductivity (EC): Measured according to JIS-H0505.

(3) Punching property: 1 with SKD11 mold
Open a square hole of 5 mm x 5 mm
Twenty samples were extracted at random from the punching up to the 0th time, and the height of each burr was measured. Further, the thickness a of the fractured portion on the punched surface was measured, and the ratio of the fractured portion to the thickness b of the test piece (a / b) × 100% was determined. This fractured portion is considered as one of the standards of the punching workability. It is evaluated that the larger the value is, the better the punching workability is, the higher the yield in the punching work is, and the processing can be performed precisely.

(4) Bending workability: A plate material is cut out to a width of 10 mm and a length (parallel to the rolling direction) of 50 mm, and is bent by W at a bending radius of 0.1 mm, and the presence or absence of cracks in the bent portion is determined by a factor of 50. It was visually observed with a microscope. The results were indicated by を for those without cracks and rough skin, Δ for those with rough skin, and x for those with cracks.

(5) Stress corrosion cracking resistance (SCC resistance):
After bending the outer lead of the above lead frame sample with a bending radius of 0.1 mm, JIS-C830
Exposure test was performed for a maximum of 500 hours in an ammonia atmosphere in accordance with No. 6, and samples were taken out periodically during the test, and the state of stress corrosion cracking in the bent portion was observed with an electron microscope. The SCC resistance was evaluated based on the time until crack generation.

(6) Corrosion resistance: The same sample as used in (5) was subjected to a salt spray test (salt water: 5% NaCl, 35 ° C.) for 24 hours in accordance with JIS-Z2371, and the corrosion state was visually observed. did. Those that did not corrode were marked with ○, those that corroded slightly were marked with Δ, and those that were severely corroded were marked X.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

As apparent from Tables 3 and 4,
No. of the present invention example. All of Nos. 7 to 22 were excellent in various properties such as punching workability (burr height, fracture portion ratio) and corrosion resistance.

On the other hand, the comparative example No. 23 is Zn
, The tensile strength was low and the punching workability was poor. No. Sample No. 24 was inferior in corrosion resistance due to a large amount of Zn, and cracked by cold rolling. No. 25 is S
Since n was small, stress corrosion cracking resistance and corrosion resistance were extremely poor.

In addition, No. Sample No. 26 had a low conductivity due to a large amount of Sn, and a crack was generated by hot rolling. No. 27
Has a small crystal grain size. No. 28 was inferior in bending workability because of a large crystal grain size. No. 29
However, because of the large amount of the first additive element, hot rolling cracking was severe and could not be produced. No. In No. 30, since the second additive element was large, the electrical conductivity was lowered, and cracks were generated by hot rolling.
No. Reference numeral 31 denotes a conventional Cu-Zn alloy, which was inferior in tensile strength, punching workability, bending workability, stress corrosion cracking resistance, and corrosion resistance.

(Example 2) No. 2 used in Example 1 13
Various metal layers were formed on the plate material by electroplating to obtain samples. The samples were examined for (7) wire bonding property and (8) solder wettability. The results are shown in Table 5 below.

The test methods (7) and (8) are described below. (7) Wire bonding property: 30 μm for the sample
One hundred (100) φ gold wires were bonded and a pull test was performed on all 100 wires, and the ratio of the number of wires broken at the wire portion was evaluated as the wire breakage rate. The larger the wire breaking ratio, the better the bonding property. Bonding was performed using a fully automatic wire bonder with a load of 50
g, ultrasonic output 0.1W, ultrasonic application time 30ms
c, The test was performed under the conditions of a stage temperature of 240 ° C.

(8) Solder wettability: The sample was treated with 250
After holding on a hot plate heated to ℃ for 3 minutes,
The solder wetting time was measured by the meniscograph method under the following conditions.

Solder used: Sn-40% Pb, Temperature: 230 ° C., Immersion speed: 25 mm / sec, Immersion time: 10 seconds, Flux: RMA type flux.

[0041]

[Table 5]

As is apparent from Table 5, as shown in FIG. 31
No. 40 to No. 40 each have a Pd layer formed to a thickness of 0.01 μm or more, and are excellent in both wire bonding property and solder wettability. Among them, No. 35-38
Since the intermediate layer was provided and the diffusion of the copper alloy component into the Pd layer was suppressed, the solder wettability was further improved.

No. Properties of 39 and 40 are slightly inferior to those of others, but this is because the Pd layer was thin.
No. No. 40 corresponds to the provision of the intermediate layer. It has better characteristics than 39.

[0044]

As described in detail above, the lead frame of the present invention has a punching property, a corrosion resistance, a bending property,
Excels in stress corrosion cracking resistance, strength, conductivity, and processability.
It has a remarkable industrial effect.

Continued on the front page (72) Inventor Takao Hirai 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 9/00-9 / 10 H01L 23/48-23/50

Claims (8)

(57) [Claims] 1. A Zn content of 5 to 35 wt% and a Sn content of 0.1 to 3 wt.
wt%, one or two or more selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr and rare earth elements in a total amount of 0.001 to 0.5 wt%, and the content of O and S is Both are 50 ppm or less, the balance is composed of Cu and inevitable impurities, and the crystal grain size is 5-35 μm, on a copper alloy member having a thickness of 0.01 μm or more, Pd is formed in a layer shape. Semiconductor device lead frame. 2. The Zn content is 5 to 35 wt%, and the Sn content is 0.1 to 3%.
wt%, one or two or more selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr and rare earth elements in a total amount of 0.001 to 0.5 wt%.
One or more selected from the group consisting of Cr, Zr, Fe, Co, Mn, Al, Ag, Mg, and P are contained in a total of 0.001 to 1 wt%, and the content of O and S is both A semiconductor comprising 50 ppm or less, the balance being Cu and unavoidable impurities, and Pd being formed in a layered form having a thickness of 0.01 μm or more on a copper alloy member having a crystal grain size of 5 to 35 μm. Equipment lead frame. 3. A Zn content of 5 to 35 wt% and a Sn content of 0.1 to 3 wt.
wt%, one or two or more selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr and rare earth elements in a total amount of 0.001 to 0.5 wt%, and the content of O and S is both are at 50ppm or less, and the balance of Cu and unavoidable impurities, grain size on the copper alloy of 5 to 35 m, and Pd is formed in layers of a thickness of 0.01 to 0.1 5 [mu] m A lead frame for a semiconductor device. 4. A Zn content of 5 to 35% by weight and a Sn content of 0.1 to 3%.
wt%, one or two or more selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr and rare earth elements in a total amount of 0.001 to 0.5 wt%.
One or more selected from the group consisting of Cr, Zr, Fe, Co, Mn, Al, Ag, Mg, and P are contained in a total of 0.001 to 1 wt%, and the content of O and S is both and at 50ppm or less, and the balance of Cu and unavoidable impurities, the grain size on the copper alloy of 5 to 35 m, Pd is formed in 0.01 to 0.1 5 [mu] m of the thickness of the laminar A lead frame for a semiconductor device. 5. A Zn content of 5 to 35% by weight and a Sn content of 0.1 to 3%.
wt%, one or two or more selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr and rare earth elements in a total amount of 0.001 to 0.5 wt%, and the content of O and S is All are 50 ppm or less, the balance being Cu and unavoidable impurities, Pd is 0.01 μm or more (but 0.2 μm) on a copper alloy member having a crystal grain size of 5 to 35 μm.
m) (excluding m or more). 6. A Zn content of 5 to 35 wt% and a Sn content of 0.1 to 3 wt%.
wt%, one or two or more selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr and rare earth elements in a total amount of 0.001 to 0.5 wt%.
One or more selected from the group consisting of Cr, Zr, Fe, Co, Mn, Al, Ag, Mg, and P are contained in a total of 0.001 to 1 wt%, and the content of O and S is both 50 ppm or less, the balance being Cu and unavoidable impurities, and a Pd having a thickness of 0.01 μm or more (excluding 0.2 μm or more) on a copper alloy member having a crystal grain size of 5 to 35 μm. A lead frame for a semiconductor device, wherein the lead frame is formed. 7. A method according to claim 6, wherein Ni, Co,
7. The semiconductor device according to claim 1, wherein one or more selected from the group consisting of a Ni-Co alloy and a Ni-Pd alloy are formed in a layered form. For lead frame. 8. The lead frame for a semiconductor device according to claim 1, wherein said crystal grain size is 5 to 30 μm.