JPH1136027A - Lead frame for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead frame for semiconductor device, excellent in blankability, corrosion resistance, stress corrosion cracking resistance, strength, electric conductivity, manufacturability, etc. SOLUTION: Pd is formed into lamellar state on a copper alloy member having a composition consisting of, by weight, 5-35% Zn, 0.1-3% Sn, and the balance Cu with inevitable impurities. This copper alloy can further contain 0.001-0.5 wt.%, in total, of one or >=2 elements selected from the group consisting of Pb, Bi, Se, Te, Ca, Sr, and rare earth elements and can further contain 0.001-1 wt.%, in total, of one or >=2 elements selected from the group consisting of Ni, Si, Cr, Zr, Fe, Co, Mn, Al, Ag, Mg, and P.

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 and corrosion resistance.

[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). However, 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, the plating layer will crack, exposing the alloy base or the area where the tie bar cut exposes the alloy base. And stress corrosion cracking. Also, punching workability was insufficient for a multi-pin lead frame having 100 pins or more.

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

[0007]

In order to solve the above-mentioned problems, the present invention (claim 1) has a feature that Zn is 5-35 wt%,
A lead frame for a semiconductor device, characterized in that Pd is formed in a layer on a copper alloy member containing 0.1 to 3 wt% of n and the balance of Cu and unavoidable impurities.

In the present invention (claim 2), the Zn content is 5 to 5.
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
Provided is a lead frame for a semiconductor device, characterized in that Pd is formed in a layered form on a copper alloy member containing wt% and the balance consisting of Cu and unavoidable impurities.

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%, Ni, Si, Cr, Zr, Fe, C
o, Mn, Al, Ag, Ma and P, one or more selected from the group consisting of a total of 0.001 to 1 wt%
Provided is a lead frame for a semiconductor device, characterized in that Pd is formed in a layer on a copper alloy member that contains Cu and the unavoidable impurities.

The present invention (claim 4) is characterized in that in the above-mentioned lead frame for a semiconductor device (claims 1 to 3), the thickness of the Pd layer is 0.01 μm or more.

The present invention (Claim 5) provides the above-mentioned lead frame for a semiconductor device (Claims 1 to 4), 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.

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. 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. The reason for defining the content to be 5 to 35 wt% is as follows.
If it is less than 35 wt%, the effect of the present invention cannot be sufficiently obtained, and
If the content exceeds 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 content of Sn is 0.1 to 2
wt%.

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.

In the lead frame for a semiconductor device according to the second invention, the copper alloy according to the first invention further includes Pb,
Punching workability is improved by containing one or more selected from the group consisting of Bi, Se, Te, Ca, Sr and rare earth elements. The reason for specifying the content in total 0.001 to 0.5 wt% is 0.00
If it is less than 1 wt%, the effect of the present invention cannot be sufficiently obtained,
If the content exceeds 0.5% by weight, the hot workability decreases.

In the lead frame for a semiconductor device according to the third invention, the copper alloy according to the second 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 the additional elements effective for improving the strength and heat resistance of the copper alloy in the first to third 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.

[0019]

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) A copper alloy having the composition shown in Table 1 below was melted in a high-frequency melting furnace and cast at a cooling rate of 6 ° C / second to form an ingot having a thickness of 30 mm, a width of 200 mm, and a length of 300 mm. Obtained.

Next, the ingot was hot-rolled at 850 ° C. to obtain a hot-rolled plate having a thickness of 12 mm, which was then 9 mm thick.
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) The punching workability was examined. In addition, 28p from the plate material
An inDIP lead frame was punched out, Ni was plated on this lead frame to a thickness of 0.5 μm, and Pd was further electroplated thereon to a thickness of 0.01 μm. About the lead frame sample obtained in this way,
(4) Stress corrosion cracking resistance and (5) corrosion resistance were examined. The results are shown in Tables 2 and 3 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 (5) 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. It is evaluated that the larger this ratio is, the better the punching processability is, the higher the yield in the punching process is, and the more precise the process can be.

(4) 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 by the time until crack generation.

(5) Corrosion resistance: The same sample used in (4) 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.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

As is clear from Tables 2 and 3,
No. of the present invention example. All of Nos. 1 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 corrosiveness due to a large amount of Zn, and cracked by cold rolling. No. In No. 25, since there was little Sn, stress corrosion cracking resistance and corrosion resistance were remarkably inferior.

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 lot of first additive elements, so hot rolling cracks are severe,
Could not be manufactured. No. In No. 28, since the amount of the second additive element was large, the electrical conductivity was lowered, and cracks were generated by hot rolling. No. 29 is a conventional Cu-Zn alloy, which was inferior in tensile strength, punching workability, stress corrosion cracking resistance, and corrosion resistance.

(Example 2) No. 2 used in Example 1 Various metal layers were formed on the plate material of No. 5 by electroplating to obtain samples. The samples were examined for (6) wire bonding property and (7) solder wettability. The results are shown in Table 4 below.

The test methods (6) and (7) are described below. (6) 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.

(7) Solder wettability: The sample was subjected to 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: RΜA type flux.

[0037]

[Table 4]

As is evident from Table 4 above, no. 30
In each of Nos. To 36, the Pd layer is formed to a thickness of 0.01 μm or more, and both the wire bonding property and the solder wettability are excellent. Among them, No. 33-36
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. 37 and 38 have slightly inferior characteristics to the others, but this is because the Pd layer was thin.
No. No. 38 corresponds to No. 38 provided with the intermediate layer. The characteristics are better than 37.

[0040]

As described in detail above, the lead frame of the present invention has excellent punching workability, corrosion resistance, stress corrosion cracking resistance, strength, conductivity, manufacturing workability, etc., and is industrially remarkable. It works.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takao Hirai 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd.

Claims (5)

[Claims] 1. A Zn content of 5 to 35 wt% and a Sn content of 0.1 to 3 wt.
A lead frame for a semiconductor device, characterized in that Pd is formed in a layer on a copper alloy member containing wt%, the balance being Cu and unavoidable impurities. 2. The Zn content is 5 to 35 wt%, and the Sn content is 0.1 to 3%.
wt%, contains one 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%, with the balance being Cu and inevitable impurities. A lead frame for a semiconductor device, wherein Pd is formed in a layer on a copper alloy member made of: 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%.
One or more selected from the group consisting of Cr, Zr, Fe, Co, Mn, Al, Ag, Ma and P are contained in a total of 0.001 to 1% by weight, and the balance is composed of Cu and inevitable impurities. A lead frame for a semiconductor device, wherein Pd is formed in a layer on a copper alloy member. 4. The lead frame for a semiconductor device according to claim 1, wherein said Pd layer has a thickness of 0.01 μm or more. 5. A method according to claim 1, wherein Ni, Co, and Pd are provided between the copper alloy and the Pd layer.
The semiconductor device according to any one of claims 1 to 4, wherein at least one selected from the group consisting of a Ni-Co alloy and a Ni-Pd alloy is formed in a layer. For lead frame.