JP3077963B2 - 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 used for a semiconductor device such as an IC, and more particularly, to a lead frame excellent in solder wettability and solder heat peelability.

[0002]

2. Description of the Related Art Lead frames for transistors and ICs are plated with Ni in order to satisfy the corrosion resistance and solderability required for a chip mounting portion, a wire bonding portion, and a soldering portion during mounting. . For this Ni plating, a watt bath or a sulfamic acid bath is usually used.
Brighteners and stress relaxation agents are added.

In general, a Ni plating film easily forms a corrosion-resistant oxide film, and when an oxide film is formed on the surface, solder wettability is remarkably reduced and soldering becomes impossible. In order to solve this problem, a method of immediately performing soldering after removing an oxide film using a strongly active flux, a method of performing soldering in a reducing atmosphere containing hydrogen gas, and the like have been used.

However, in the case of using a flux, it is necessary to wash with a chlorofluorocarbon or a chlorinated organic solvent in order to remove the flux. In recent years, however, global environmental problems and safety standards for handling chemical substances have been considered. Therefore, there is a problem that the use of chlorofluorocarbon or a chlorine-based organic solvent must be reduced. Further, when soldering is performed in a reducing atmosphere containing hydrogen gas, there are disadvantages such as an increase in complexity of the apparatus and an increase in cost.

In order to solve the above problem, Japanese Patent Publication No. Sho 60
According to Japanese Patent No. 33312, a bright Ni plating film is formed on a copper or copper alloy lead frame, and then a P-containing Ni plating film is formed on the Ni plating film. A lead frame that prevents soldering and has excellent solder wettability has been proposed, and can be soldered in a nitrogen gas atmosphere. Also, N
In addition to i-P, Ni-Fe-P, Ni-Co-P (JP-A-4-162460, JP-A-4-162461, JP-A-4-247646, JP-A-5-226)
540) has been proposed.

However, when the Ni plating film contains impurities (S, C, etc.) from a brightener or P for reducing action, if the Ni plating film is held at a high temperature after soldering, P, etc. will be formed at the interface between the solder and the plating. A phenomenon of concentration and peeling of the solder (hereinafter referred to as a thermal peeling phenomenon) occurs. The thermal delamination phenomenon impairs the reliability of an IC, and is a problem that is concerned when, for example, a semiconductor device is used at a high temperature or an IC that generates a large amount of heat from a chip itself is used.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and provides a lead frame for a semiconductor device which is excellent in solder wettability and also excellent in solder heat peelability. The purpose is to:

[0008]

The semiconductor device lead frame with respect to the present invention SUMMARY OF THE INVENTION, at least in the chip mounting portion of the lead frame, the hydrogen weight at 10ppm or more, 5000
It is characterized by having a plating film containing less than ppm . Here, hydrogen in the plating film has a reducing action, is released from the plating film when heated for soldering, reduces the oxide film generated on the plating film surface, and makes the surface excellent in solder wettability. . Most of the hydrogen in the plating film is released by heating and has no adverse effect.

The amount of hydrogen contained in the plating film is 10 p
If it is less than pm, the oxide film formed on the surface of the plating film cannot be sufficiently reduced, so that the film must contain an amount of hydrogen of 10 ppm or more. On the other hand, if the hydrogen content in the film exceeds 5000 ppm, the toughness of the plated film is lost and the film becomes brittle, which causes a problem in bending workability. Therefore, the amount of hydrogen in the film is 5000 ppm or less . . From the viewpoint of both reducing action and bending workability, the hydrogen content of the plating film is more preferably 50 to 1000 p.
pm.

[0010] The composition of the plating film is Ni, F
e, Co or their alloys, ie, Ni, Fe, C
o simple metal, Ni-Fe alloy, Ni-Co alloy, Fe
-Co alloys and Ni-Fe-Co alloys are preferred. Particularly, the following composition formula (wt%): Ni _(85-100) Fe _(0-10) Co
Those represented by _(0-5) are preferred. In addition, Pd,
Pd-Ag, Ni-P, Ni-B, etc., metals or alloys of other compositions used as plating films for lead frames can be used, and any hydrogen contained in these metals or alloys can be used to form oxide films. Has a reducing action.

The above-mentioned plating film is formed without an underlying plating layer.
Alternatively, Ni, Fe, Co or an alloy thereof, that is, a single metal of Ni, Fe, Co, a Ni—Fe alloy, N
It is formed on a base plating layer made of an i-Co alloy, an Fe-Co alloy, or a Ni-Fe-Co alloy, and constitutes the outermost surface layer of the lead frame. The above-mentioned plating film has a high hardness due to the inclusion of hydrogen, and the bending workability and the like are reduced accordingly. However, the bending workability and the like can be improved by applying a base plating layer. Ni plating, Ni-
It is preferable to apply a relatively soft film having excellent corrosion resistance, such as Co plating or Co plating.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, hydrogen is
The plating film containing not less than m and not more than 5000 ppm is formed on at least the chip mounting portion of the lead frame, if necessary, the wire bond portion and / or the soldering portion at the time of mounting, or the entire lead frame. The thickness of the plating film is required to be 0.01 μm or more irrespective of the composition of the plating film in order to secure the corrosion resistance and the reducing action of the oxide film, and the upper limit is set to 5 μm at which the bending workability decreases.
Preferably, it is 0.05 to 3 μm. When the plating film is formed on the underlying plating layer, the thickness of the plating film is 0.01 to 5 μm, more preferably 0.01 to 1 μm from the viewpoint of workability, and the thickness of the underlying plating layer is: 0.5 to 5 regardless of the composition of the plating layer from the viewpoint of corrosion resistance
μm range.

As the solder used for the lead frame according to the present invention, for example, 90% Sn-10% Pb, 63
% Sn-37% Pb, Pb-5% Sn-1.5% Ag,
Sn-3.5% Sb and the like. Further, as the lead frame substrate according to the present invention, for example, Fe-42% N
Iron-based materials such as i, Cu-0.1% Fe-0.03%
P, Cu-0.1% Fe-0.03% P-2% Sn, C
u-0.6% Cr-0.25% Zr, Cu-3.2% N
A copper-based material such as i-0.7% Si-1.25% Sn-0.3% Zn can be used.

As a specific means for containing hydrogen in the plating film, for example, a method of co-depositing hydrogen at the time of plating, that is, a method of incorporating hydrogen generated on the cathode surface during plating, and a method of incorporating hydrogen during plating. A method of bubbling and containing, a method of absorbing after plating,
Is used. In the above, electrolysis is performed under plating conditions that generate hydrogen, and the adjustment of the hydrogen content is performed by changing the bath composition, current density, and the like.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a lead frame for a semiconductor device according to the present invention will be described below. Cu-0.1% Fe-0.0
Lead frame materials each having a single-layer or multiple-layer plating having the configuration shown in Table 1 were prepared on a copper alloy material composed of 3% P. The plating solution used to form each plating film was as shown in Table 2, and the amount of hydrogen contained was adjusted by changing the current density, the temperature, and the like. In addition, in the column of “plating configuration” and the column of “plating thickness” in Table 1, the left side of the slash (/) represents the upper plating film, and the right side of the slash (/) represents the underlying plating layer. Those with no slash are single-layer plating films.

[0016]

[Table 1]

[0017]

[Table 2]

Solder wettability of the above lead frame material (solder spread area, solder wet time, solder wettability)
And the heat-peeling resistance (peeling time) of the solder were measured by the following evaluation test method, and the results are shown in Table 1.

In the solder spread test, nitrogen gas (oxygen 2
In a glove box flowing nitrogen gas + 5% hydrogen gas, place a plated sample on a hot plate heated to 420 ° C., and after heating for 1 minute, 1.1 mmφ Pb-5% Sn A −1.5% Ag solder ball was placed (without flux), and the area where the solder ball spread was measured. Solder wetting time and solder wetting power are as follows for 90Sn-10Pb solder melted at 270 ° C.
The sample coated with the flux was immersed to a depth of 12 mm, and measured by a meniscograph method. The peeling time is 90 Sn
The sample to which the −10 Pb solder was soldered was heated in a clean oven at 175 ° C., and after a certain period of time, the sample was taken out, subjected to a bending test, visually inspected for peeling, and the heating time until peeling was measured. Table 3 shows the above evaluation test methods and test conditions.

[0020]

[Table 3]

As shown in Table 1, in the example of the present invention having the plating film containing hydrogen, the solder spread area was inferior to that of the conventional Ni-8% P and Ni-8% P / Ni, but the solder wettability was low. The time, solder wettability and heat-peelability are all excellent. In addition, since the film of the present invention does not contain any impurities in the film, it does not peel even after aging at high temperature similarly to the conventional Ni film, and has excellent heat-resistant peeling properties. On the other hand, the comparative example having a small hydrogen content is inferior in the solder spreading area, the solder wetting time, and the solder wetting force to the examples of the present invention.

[0022]

As described above, according to the present invention,
By including a predetermined amount of hydrogen in the plating film,
A lead frame for a semiconductor device having both excellent solder wettability and solder heat-peelability can be obtained. Further, according to the present invention, it is possible to perform soldering without flux, and there is also an effect that it is not necessary to perform soldering in a reducing atmosphere.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-69122 (JP, A) JP-A-53-73969 (JP, A) JP-A 8-186050 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 23/50 C25D 3/00 B23K 1/20

Claims (4)

(57) [Claims] 1. A lead frame for a semiconductor device, characterized in that at least a chip mounting portion of the lead frame has a plating film containing 10 ppm or more and 5000 ppm or less of hydrogen. 2. The plating film according to claim 1, wherein the plating film is a plating film made of Ni, Fe, Co, or an alloy thereof containing 10 ppm or more and 5000 ppm or less of hydrogen. Lead frame for semiconductor devices. 3. The lead frame for a semiconductor device according to claim 2, wherein the plating film is formed on a base plating layer made of Ni, Fe, Co, or an alloy thereof. 4. The Ni-plated film according to claim 2, wherein the plated film is a Ni-plated film containing 10 ppm or more and 5000 ppm or less of hydrogen, and is formed on the underlying Ni-plated layer. Semiconductor device lead frame.