JP3066952B2 - Lead frame material - 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 material suitably used for manufacturing a lead frame of a semiconductor device.

[0002]

2. Description of the Related Art The number of pins has increased with the increase in the degree of integration of ICs and LSIs. A method of manufacturing a lead frame by etching a lead frame material is a method suitable for miniaturization of a lead portion. Japanese Unexamined Patent Publication (Kokai) No. 3-148856 discloses an etching stop layer made of aluminum having two layers of metal having different thicknesses. A method of manufacturing a lead frame by using a lead frame material having a three-layer structure sandwiched between layers in a sandwich shape and etching the lead frame material is described.

According to this method, two metal layers having different thicknesses can be selectively etched by providing the etching stop layer, and a thick metal layer serving as a base material of a lead frame is required. By providing a thin metal layer serving as a connecting portion with the IC with a thickness corresponding to the fineness required for the connecting portion, a fine connecting portion with the IC and sufficient mechanical strength can be obtained. A strong lead frame can be manufactured.

However, the lead frame material having a three-layer structure used in this method is aluminum on which an etching stop layer material is formed by vapor deposition. The formation of an aluminum layer by vapor deposition has a problem that the process is complicated and leads to an increase in the cost of the lead frame material.

In a method of manufacturing a lead frame using a lead frame material having a three-layer structure, a polyimide film which is an insulating protective film is formed on a surface on which leads are formed by using a polyamic acid-based adhesive. For example, there is a process in which the lead frame material is exposed to a high temperature, such as curing at a temperature of 350 ° C. or more and bonding, and the etching stop layer is required to have heat resistance to withstand such a high temperature. When a nickel layer or the like which can be easily formed by electroplating or the like is exposed to a high temperature of 350 ° C. or more, copper of the metal layer diffuses into the nickel layer and cannot function as an etching stop layer.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a three-layer structure which can be easily formed by electroplating without requiring a complicated process such as vapor deposition and has an etching stop layer having excellent heat resistance as an intermediate layer. And a lead frame material.

[0007]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a specific alloy layer having a specific thickness is used as an etching stop layer for a lead frame material having a three-layer structure. By adopting this method, it was found that an etching stop layer can be easily formed by electroplating without the need for complicated steps such as vapor deposition, and a lead frame material having a three-layer structure having excellent heat resistance was obtained. Based on the above, the present invention has been completed.

[0008] That is, the present invention provides a thickness of 35 to 300 μm.
1.6 to 10 μm in thickness and a phosphorus content of 0.3 to 1.0 m between a copper or copper alloy layer having a thickness of m and a copper layer having a thickness of 0.2 to 30 μm.
An object of the present invention is to provide a lead frame material provided with a nickel-phosphorus alloy layer of a weight percent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the lead frame material of the present invention, a copper or copper alloy layer having a thickness of 35 to 300 μm is a member for forming an outer lead or the like of a lead frame. If it is, the mechanical strength of the outer lead cannot be maintained, and the thickness is 300μ.
If it exceeds m, etching for a long time is required, and productivity is deteriorated. The preferred thickness is 50-200 μm.
As the copper alloy, for example, copper, Sn, Ni, Zn,
An alloy with at least one metal selected from P, Fe, Zr, Cr, Mg, and Si, wherein a content of the metal other than copper in the copper alloy is 0.01 to 5% by weight. It is suitable. Further, the copper or copper alloy layer preferably has a surface roughness Ra of 0.1 to 2.0 μm, more preferably 0.2 to 0.8 μm.

The copper layer having a thickness of 0.2 to 30 μm serves as a member for forming a fine pattern.
If it is less than μm or more than 30 μm, a fine pattern cannot be formed. Preferred thickness is 0.5-10μ
m.

The thickness is 1.6 to 10 μm and the phosphorus content is 0.1 to 10 μm.
The nickel-phosphorus alloy layer of 3 to 1.0% by weight is a metal layer which is not etched by an etching solution for copper or copper alloy, and has a role of preventing one of the metal layers sandwiching it from being etched by the other. Fulfill. Since the nickel-phosphorus alloy layer can be easily formed by electroplating, there is an advantage that a low-cost lead frame material can be obtained without complicated steps as compared with an aluminum layer conventionally formed by vapor deposition. Further, since the nickel-phosphorus alloy contains phosphorus, even if it is exposed to a high temperature, copper in an adjacent layer does not diffuse into the nickel-phosphorus alloy layer, and is excellent in heat resistance. The content of phosphorus in the nickel-phosphorus alloy layer is preferably 0.3 to 1.0.
%, More preferably 0.5 to 0.8% by weight. If the phosphorus content is less than 0.3% by weight, the heat resistance decreases, copper diffuses into the nickel layer, and cannot serve as an etching stop layer. On the other hand, when the content exceeds 1.0% by weight, the nickel-phosphorus electrodeposition efficiency decreases, and the productivity decreases.

The thickness of the nickel-phosphorus alloy layer is 0.04 μm.
m, the function as an etching stop layer,
That is, when one of the metal layers is etched, the function of protecting the other metal layer cannot be sufficiently secured. On the other hand, when the thickness exceeds 70 μm, it takes a long time to finally remove the etching stop layer, and the productivity in manufacturing a lead frame is reduced. Preferred thickness is 1.6 to 10 μm
And more preferably 2.0 to 5.0 μm.

From the viewpoint of ensuring rust prevention, the surface of the lead frame material is preferably subjected to a chromate treatment or a chromate treatment containing a zinc compound.

The lead frame material of the present invention has a thickness of 35 to
Nickel-phosphorus plating on the surface of a 300 μm copper or copper alloy layer to a thickness of 1.6 to 10 μm and a phosphorus content of 0.3
It can be manufactured by forming a nickel-phosphorus alloy layer of about 1.0% by weight and further forming a copper layer by copper plating on the surface of the nickel-phosphorus alloy layer. As needed,
A chromate layer is formed on the surface of the copper layer. Preferred plating solution compositions and plating conditions used for nickel-phosphorus plating are described below. (1) Plating bath composition Nickel sulfate 200 to 300 g / l Boric acid 10 to 100 g / l Phosphorous acid 0.2 to 20 g / l Sodium imide sulfobenzoate 1 to 50 g / l Magnesium sulfate 10 to 200 g / l ( 2) Electrolysis conditions pH: 1.6 to 3.0, current density: 1 to 10 A / d
m ² , liquid temperature: 20-70 ° C. As a preferable semiconductor device that can be manufactured using the lead frame material of the present invention, TBGA (tape ball)
grid array), CSP (chipsize)
package) and the like.

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A copper alloy foil having a thickness of 150 μm (copper-nickel-tin alloy, manufactured by Mitsubishi Shindoh Co., Ltd., trade name: TAMAC15, surface roughness Ra: 0.2 μm) was prepared. A plating metal deposition prevention coating made of plastic was previously applied to the plating surface.

Using this, the following manufacturing steps (1 to 5) are sequentially performed, and a nickel-phosphorus alloy layer (thickness 2 μm, phosphorus content 0.8% by weight, surface roughness Ra) is formed on the copper alloy layer. :
0.2 μm) and a copper layer (thickness 2 μm, surface roughness Ra:
0.2 μm) to produce a three-layered lead frame material. After the completion of each of the steps 1 to 5, washing was performed. Manufacturing process Degreasing treatment (1) Degreasing liquid Sodium orthosilicate 30 g / l Sodium carbonate 20 g / l Sodium hydroxide 20 g / l (2) Electrolytic degreasing conditions Current density: 5 A / dm ² , treatment time: 30 seconds, liquid temperature: 4
1. 0 ° C., cathode: copper alloy foil, anode: iridium oxide 2. Pickling treatment (1) Cleaning solution sulfuric acid: 25 g / l (2) Cleaning conditions Treatment time: 30 seconds, liquid temperature: 20 ° C Formation of nickel-phosphorus alloy plating layer (1) Plating solution Nickel sulfate 300 g / l Boric acid 40 g / l Phosphorous acid 4 g / l O-sulfobenzoimide sodium 10 g / l Magnesium sulfate 80 g / l (2) Electrolytic conditions Current ^3. Density: 1.1 A / dm ² , electrolysis time: 10 minutes, liquid temperature: 35 ° C., pH: 2.5, anode: iridium oxide Formation of copper plating layer (1) Plating solution Copper sulfate 280 g / l Sulfuric acid 70 g / l Additive (gelatin) 3 ppm Additive (Cl ⁻ ) 10 ppm (2) Electrolysis conditions Current density: 3.5 A / dm ² , electrolysis time: 4 minutes, liquid temperature:
4. 35 ° C., anode: iridium oxide Formation of antirust layer (1) Treatment liquid 3.5 g / l sodium dichromate (2) Treatment conditions Immersion treatment time: 25 seconds, liquid temperature: 20 ° C, pH: 4.7 Drying Drying conditions Temperature: 100 ° C., time: 5 minutes by using a lead frame material resulting three-layer structure in the above step, a heat treatment (200 ° C. in an N ₂ gas atmosphere, 3
(00 ° C., 400 ° C., 500 ° C.) for 30 minutes, and the heat resistance of the lead frame material was evaluated by the following high-temperature heat diffusion test.

High Temperature Thermal Diffusion Test A cross section of a lead frame (joint between nickel-phosphorus alloy layer and thin copper layer) using SEM (scanning electron microscope) and Auger electron spectroscopy for test specimens heat-treated at each temperature. The degree of heat diffusion alloying between metals depending on the heating temperature was analyzed and determined as a thermal diffusivity (%). The numerical values are shown in Table 1. The smaller the thermal diffusivity (%), the less alloying between the metal layers has progressed, and the lead frame material has excellent heat resistance and excellent selectivity.

COMPARATIVE EXAMPLE 1 Using the same copper alloy foil as in Example 1, the above-mentioned step 3 was changed to the following nickel plating layer forming step 3 ', and the nickel-phosphorus alloy layer was replaced with a nickel layer (2 μm thick). , Surface roughness R
a 0.2 μm), except that it was changed to
A lead frame material was prepared and subjected to a thermal diffusion test in the same manner as in Example 1, and the results are shown in Table 1. 3 '. Formation of nickel plating layer (1) Plating solution Nickel sulfate 280 g / l Boric acid 40 g / l o-Sulfobenzoimide sodium 5 g / l (2) Electrolysis conditions Current density: 1.0 A / dm ² , electrolysis time: 10 minutes , Liquid temperature: 35 ° C, pH: 2.5, anode: iridium oxide

[0020]

[Table 1] The results in Table 1 show that the lead frame material of Example 1 has excellent heat resistance.

[0021]

Since the lead frame material of the present invention has a three-layer structure having an etching stop layer made of a nickel-phosphorus alloy as an intermediate layer, it is not only suitable for forming fine lead portions. It is also excellent in heat resistance. In addition, since the etching stop layer is a nickel-phosphorus alloy layer that can be formed by electroplating, the lead frame material of the present invention can be easily manufactured without a complicated process such as vapor deposition, and can improve productivity. Is also excellent.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyoshi Aso 1226 Shimoedashiri, Shimodate City, Ibaraki Pref. Japan Electrolysis Co., Ltd. Shimodate Plant (56) References 308115 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 23/50

Claims (1)

(57) [Claims] 1. A thickness of 1.6-10 μm between a copper or copper alloy layer having a thickness of 35-300 μm and a copper layer having a thickness of 0.2-30 μm.
m. A lead frame material provided with a nickel-phosphorus alloy layer having a phosphorus content of 0.3 to 1.0% by weight.