KR101028048B1 - Metal pad formation method - Google Patents

Abstract

A method of forming a metal pad is disclosed. Providing a substrate having a circuit pattern formed thereon, applying an ink including metal particles capped with a protective film to form a pad pattern connected to the circuit pattern, and heating the pad pattern to sinter the metal particles. The metal pad formation method can improve the connection property with a solder ball or a wire by forming the metal pad which has a uniform surface and high adhesive force.

Pad, Metal Particle, Ink, Sinter

Description

Method for forming metal pad

The present invention relates to a metal pad forming method.

In a semiconductor package or the like, a gold pad surface-treated with gold is used on the surface of an electrode for the purpose of improving connection characteristics with solder balls or wires.

In the past, a plating method was mainly used to surface-treat the surface of the electrode with gold. However, the method of forming the gold pad by plating has problems such as complexity of the process, difficulty in managing the plating solution, waste of the discarded plating solution and difficulty in recovering the plating solution.

Thus, in order to solve the problem of the plating process, a method of forming a gold pad using gold ink has been proposed. However, the method of forming a gold pad using gold ink has many problems in practical use because of problems such as uneven surface, lack of adhesion to the substrate, and high temperature sintering temperature.

The present invention provides a metal pad forming method for forming a metal pad having a uniform surface state and high adhesion by using an ink containing metal particles.

In addition, the present invention provides a metal pad forming method for forming a metal pad even at a low sintering temperature.

According to an aspect of the present invention, providing a substrate having a circuit pattern, forming a pad pattern connected to the circuit pattern by applying an ink including metal particles capped with a protective film, heating the pad pattern There is provided a metal pad forming method comprising the step of sintering metal particles.

The metal particles may comprise gold.

The protective film may be made of dodecylamine.

In the sintering step, the metal particles may be sintered in an atmosphere including at least one of nitrogen, formic acid, and air.

The sintering step may be performed at 170 to 250 ° C.

Prior to forming the pad pattern, the method may further include forming a nickel (Ni) layer on the circuit pattern, wherein the pad pattern may be formed on the nickel layer.

In the forming of the nickel layer, the nickel layer may be formed by a plating method.

In the forming of the pad pattern, ink may be applied using any one of a jetting method, a dropping method, a spraying method, and a printing method. .

According to the present invention, by forming the metal pad in the process of applying and sintering the metal ink, the process can be simplified and the cost can be reduced.

In addition, the present invention can improve the connection properties with the solder ball or wire by forming a metal pad having a uniform surface and high adhesion.

In addition, the present invention by sintering the metal pad at a low temperature, it is possible to prevent damage to the electronic device when forming the metal pad.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a pad forming method according to an embodiment of the present invention.

The method of forming a pad according to an embodiment of the present invention includes providing a substrate (S110), forming a pad pattern (S120), and sintering (S130).

First, as shown in FIG. 2, a substrate 10 on which a metal pad 35 is to be formed is provided (S110). The circuit pattern 20 to be electrically connected to the metal pad 35 is formed on the substrate 10. Here, the substrate 10 may be a semiconductor substrate having various electronic devices, and the circuit pattern 20 formed on the semiconductor substrate may be electrically connected to the electronic devices.

Next, an ink including the metal particles 32 capped by the protective film 34 is coated to form a pad pattern 30 connected to the circuit pattern 20 (S120). As shown in FIG. 4, ink is selectively sprayed where a metal pad 35 is needed to form a pad pattern 30. Selective jetting of the ink may be performed by a jetting method, a dropping method, a spraying method, or a printing method. In this embodiment, a printing method in which ink is ejected by the inkjet head 50 is used.

Here, the capped metal particles 32 included in the ink may include a protective film including metal particles 33 having a particle diameter of several nanometers (nm) and capping molecules surrounding the metal particles 33. It consists of 34. The protective film 34 prevents the metal particles 33 in the ink state from being bonded or agglomerated. In addition, since the protective film 34 is removed by heat in the sintering step to be described later, it does not prevent grain growth of the metal particles 33. Accordingly, the protective film 34 may serve to increase the surface smoothness of the metal pad 35 by allowing the growth of the metal particles 33 in an even particle state.

In this embodiment, in order to form a gold pad, an ink including gold particles and a dodecylamine protective film 34 surrounding them is presented. The protective film 34 including dodecylamine may also play a role of increasing adhesion to the substrate 10 or the circuit pattern 20, which is the application target, in addition to the smoothness described above.

In addition, as shown in FIG. 3, in the present embodiment, the nickel layer 25 may be formed on the circuit pattern 20 before the pad pattern 30 is formed. When the circuit pattern 20 is formed of copper, the nickel layer 25 prevents the diffusion of the gold film formed of the gold particles into the copper layer. Here, the nickel layer 25 may be formed by an electrolytic or electroless plating method.

Next, the pad pattern 30 is heated to sinter the metal particles 33 (S130). By heating the ink forming the pad pattern 30, the solvent contained in the ink, the protective film 34, and the like are volatilized. As a result, the protective film 34 capping the metal particles 33 is removed, and the metal particles 33 are fused with each other to form a metal film. As shown in FIG. 5, in the present embodiment, the pad pattern 30 is heated through a heater 65 installed in the sintering furnace 60.

Here, in order to minimize the residual ratio of the solvent and the protective film 34 and to increase the uniformity of the sintered particles, the sintering process may be performed under the atmosphere 40. Accordingly, the metal pad 35 having a uniform surface and high adhesion can be formed to improve the connection property between the metal pad 35 and the solder ball or wire. As shown in FIG. 5, in this embodiment, the sintering is performed in the sealed sintering furnace 60 into which the atmosphere 40 is injected.

In this embodiment, in order to improve the connection characteristics of the gold pad, the gold pad is sintered in the atmosphere 40 containing at least one of nitrogen, formic acid and air. Here, the atmosphere 40 may also play a role of lowering the sintering temperature as well as improving the connection characteristics of the gold pad. Conventionally, when forming a gold pad using a gold ink, it could not be sintered at 250 degrees C or less. Accordingly, in the case of the semiconductor substrate, a problem occurs that damages the electronic device due to heat. In the present embodiment, using the atmosphere 40, the gold pad is formed to ensure the connection characteristics with the solder ball or wire even at a sintering temperature of 170 ~ 250 ℃. Therefore, there is an advantage of preventing damage to the electronic device due to heat.

On the other hand, the gold pad manufactured by the method according to the present embodiment shows a high reliability in a wire pull test showing the bonding ability with the wire. Experimental results, it is confirmed that the gold pad manufactured by the method according to the present embodiment has a binding force of the wire and 4.5 ~ 5gf. This bonding force is generally sufficient for wire bonding, demonstrating that the gold pads formed by the printing method at low temperatures (170-250 ° C) by this embodiment have sufficient reliability.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

Many embodiments other than the above-described embodiments are within the scope of the claims of the present invention.

1 is a flow chart showing a pad forming method according to an embodiment of the present invention.

2 to 5 are cross-sectional views showing the steps of the pad forming method according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: substrate 20: circuit pattern

25: nickel layer 30: pad pattern

32: capped metal particles 33: metal particles

34: protective film 35: metal pad

40: atmosphere 50: inkjet head

60: sintering furnace 65: burner

Claims (8)

Providing a substrate having a circuit pattern formed thereon; Forming a nickel (Ni) layer on the circuit pattern; Forming a pad pattern connected to the circuit pattern by applying an ink including metal particles capped with a protective film on the nickel layer; And Heating the pad pattern to sinter metal particles. The method of claim 1, The metal particle forming method of the metal pad, characterized in that it comprises gold. The method of claim 2, The protective film is a metal pad forming method comprising a dodecylamine (dodecylamine). The method of claim 3, The sintering step, A metal pad forming method comprising sintering metal particles in an atmosphere containing at least one of nitrogen, formic acid and air. The method of claim 4, wherein The sintering step, the metal pad forming method, characterized in that made at 170 ~ 250 ℃. delete The method of claim 1, In the forming of the nickel layer, Forming the nickel layer is a metal pad forming method, characterized in that the plating method. 6. The method according to any one of claims 1 to 5, Forming the pad pattern, A method for forming a metal pad, characterized in that the ink is applied by any one of a jetting method, a dropping method, a spraying method, and a printing method.

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