KR20000039475A - Semiconductor package - Google Patents

Abstract

PURPOSE: A semiconductor package is provided to improve wire-bondability and solderability, and to prevent an absorption of moisture through an interface between outer leads and a mold body. CONSTITUTION: A semiconductor package(50) includes a semiconductor chip(60) having electrode pads(62) formed thereon. The package(50) further includes a lead frame(70) made of copper or copper alkloy. The lead frame(70) has a die pad(71) on which the chip(60) is attached by an adhesive(75), inner leads(72) electrically connected with the electrode pads(62) by bonding wires(66), and outer leads(74) outwardly protruding from a mold body(77). In the package(50), wire-bonded portions of the inner leads(72) and the outer leads(74) are plated with nickel(82) and gold(81). The nickel plating layer(82) acts as a diffusion barrier for preventing copper diffusion during wire bonding process. In addition, the bonding wires(66) has the same material as the gold plating layer(81). Thereby, wire-bondability of the inner leads(72) is improved. Moreover, since the remaining portions of the inner leads(72) are copper, adhesive property to the mold body(77) becomes excellent and thereby absorption of moisture is prevented. The nickel-gold plating layer(80a) of the outer leads(74) improves solderability.

Description

Semiconductor package

The present invention relates to a semiconductor package, and more particularly, to a semiconductor package using a copper-based lead frame having a nickel-gold plated layer or a tin-gold plated layer capable of securing good solderability and wire bonding properties.

A semiconductor package having a structure in which a semiconductor chip is mounted on a leadframe and sealed with a molding resin may be formed at the leading end of the inner lead in order to ensure good wire bonding between the gold (Au) bonding wire and the leading end of the inner lead. Silver (Ag) is plated thinly, and a lead (Pb) plating layer is formed on the package outer lead to ensure good solderability with the printed circuit board.

However, in order to shorten the environmental problem in the world and to shorten the manufacturing process of the semiconductor package, the semiconductor package and lead frame manufacturers may use nickel (Ni) -palladium (Pd) as a plating material to replace the silver plating layer and the lead plating layer. A plating film is developed. The lead frame on which the nickel-palladium plating film is formed is a kind of pre-plated leadframe (PPF).

1 is a cross-sectional view showing a semiconductor package using a copper-based lead frame having a nickel-palladium plated film according to the prior art. Referring to FIG. 1, the semiconductor package 10 may include a semiconductor chip 20 attached to a die pad 31 of a copper-based lead frame 30 on which a nickel-palladium plating film 40 is formed by an adhesive 35. And a lead 33 extending toward the die pad 31, a bonding wire 26 made of gold (Au) and a semiconductor chip 20 electrically connecting the electrode pad 24 and the lead 33 of the semiconductor chip. ) And a package body 37 formed by sealing a portion of the lead 33 connected by the bonding wire 26 with a liquid molding resin. On the other hand, the lead 33 is formed with the inner lead 32 connected to the electrode pad 24 and the bonding wire 26 of the semiconductor chip, and the outer lead 32 and the outside protruding out of the package body 37. It consists of a lead 34, the external lead 34 is bent to fit the mounting form of the printed circuit board. In Figure 1 it is bent into a gull wing type (Gull Wing Type) of the surface mounting form.

Then, after the nickel plating layer 42 is formed on the entire surface of the copper-based lead frame 30 with a thickness of 30 to 70 microinches (μinch), a palladium plating layer of at least 3 micro inches or more on the nickel plating layer 42 ( 41) to form a nickel-palladium plating layer 40.

When the copper-based lead frame 30 having the nickel-palladium plating layer 40 formed therein has advantages such as shortening of the assembly process and removal of environmentally harmful substances (Pb), but it has the following problems.

First, the palladium plating layer 41 and the bonding wire 26 made of gold are inferior in bonding property. That is, palladium and gold are dissimilar metals, and since palladium has a melting point of 492 ° C or higher than gold (Au) having a melting point of 1063 ° C, the bonding state of the palladium plating layer 41 and the bonding wire 26 is unstable.

Second, the palladium plating layer 41 and the solder formed on the external lead 74 are inferior in solderability. That is, the external lead 74 and the solder with which the nickel-palladium plating layer 40 is formed, and the preferred soldering process, proceed with the soldering process at an operating temperature of about 245 ° C., and the palladium plating layer (Atomic Diffusion) within 10 seconds. 41 is melted to join the nickel plating layer 42 and the solder inside the palladium. However, when the soldering process is not performed as described above, when the soldering process is performed at about 245 ° C., the palladium plating layer may be oxidized by heat damage to form a palladium oxide layer (PdO). Palladium oxide, on the other hand, is a stable organic material that is insoluble in aqua regia (a chemical used to melt gold). Therefore, when soldering using a solder, the palladium plating layer is not melted by the palladium oxide film, and thus the bonding between the nickel plating layer inside the palladium plating layer and the solder is hindered, which causes a decrease in solderability.

Third, the palladium plated layer 41 has a lower bonding property with respect to a molding resin forming the package body 37, for example, an epoxy molding compound (EMC), compared with copper, and thus the package body 37 and the external lead. It acts as a factor that reduces the reliability of the semiconductor package 10 by providing a moisture absorption path through the adhesive interface of 74.

Accordingly, an object of the present invention is to provide a semiconductor package capable of improving wire bonding properties and solderability, and preventing moisture from being absorbed through the adhesion interface between the external lead and the package body.

1 is a cross-sectional view showing a semiconductor package using a copper-based lead frame having a nickel-palladium (Ni-Pd) plated film according to the prior art;

2 is a cross-sectional view showing a semiconductor package using a copper-based lead frame having a nickel-gold (Ni-Au) plated film according to the present invention.

Description of the main parts of the drawing

10, 50: semiconductor package 20, 60: semiconductor chip

24, 62: electrode pads 26, 66: bonding wire

30, 70: copper-based lead frame 31, 71: die pad

33, 73: lead 35, 75: adhesive

37, 77: package body 40: nickel-palladium plated film

80a, 80b: nickel-gold plated film

In order to achieve the above object, the present invention (A) a semiconductor chip having a plurality of electrode pads formed on the upper surface; (B) (a) a die pad to which the semiconductor chip is attached, (b) a plurality of internal leads extending toward the die pad, and (c) a plurality of external bodies formed integrally with the internal leads and extending out of the die pad. A copper-based lead frame including a lead; (C) bonding wires electrically connecting the electrode pads of the semiconductor chip to the internal leads; And (D) a package body formed by sealing the semiconductor chip, the bonding wire, and the inner lead with a liquid molding resin, wherein the outer lead protruding out of the package body is bent to a mounting form, and the bonding wire is Provided is a semiconductor package, wherein a nickel plated layer and a gold plated layer are sequentially formed on a front end portion of the inner lead to be joined, and a surface having a predetermined thickness on the surface of the outer lead.

In addition, the thickness of the nickel plating layer according to the present invention is 15 to 100 microinch (μinch), the thickness of the gold plating layer is preferably 1 microinch or more.

The present invention also provides a semiconductor package in which a tin plated layer and a gold plated layer are sequentially formed on the front end portion of the inner lead to which the bonding wire is bonded, and on the surface of the outer lead to a predetermined thickness. The thickness of the tin plating layer is 30 to 70 micro inches, and the thickness of the gold plating layer is preferably 1 micro inch or more.

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

2 is a cross-sectional view showing a semiconductor package using a copper-based lead frame having a nickel-gold plated film according to the present invention. Referring to FIG. 2, the semiconductor package 50 according to the present invention is a copper-based lead frame 70 in which nickel-gold (Ni-Au) plating layers 80a and 80b are formed instead of a copper-based lead frame in which a nickel-palladium plating layer is formed. ) Is a semiconductor package using.

Referring to the semiconductor package 50 using the copper-based lead frame 70 having the nickel-gold plating layers 80a and 80b, the semiconductor chip 60 having the plurality of electrode pads 62 formed on the upper surface thereof, and the semiconductor The package body 77 formed by sealing a copper lead frame 70 on which the chip 60 is mounted, and an electrical connection portion between the semiconductor chip 60 and the lead 73 of the copper lead frame with a liquid molding resin. It is composed of

The copper-based lead frame 70 includes a die pad 71 to which the semiconductor chip 60 is attached by an adhesive 75, a plurality of internal leads 72 extending toward the die pad 71, and an internal lead ( It is formed integrally with 72 and includes a plurality of external leads 74 extending out of the package body 77, the external leads 74 are bent to fit the mounting form of the printed circuit board. The outer lead 74 according to the embodiment of the present invention is bent into a hook wing type. The tip portion of the electrode pad 62 and the inner lead 72 of the semiconductor chip are electrically connected by a bonding wire 66 made of gold.

In the embodiment of the present invention, the nickel plated layer 82 and the gold plated layer 81 have a predetermined thickness on the front end portion of the inner lead 72 to which the bonding wire 66 is connected, the surface of the outer lead 74. This is formed in turn. Reference numeral 80a denotes a nickel-gold plating layer formed to a predetermined thickness on the surface of the outer lead 74, and reference numeral 80b denotes a nickel-gold plating layer formed to a predetermined thickness on the tip portion of the inner lead 72. As shown in FIG.

First, the nickel plating layer 82 serves as a diffusion barrier to prevent diffusion of copper by thermal shock during the wire bonding process. Nickel plated layer 82 is plated to a thickness of 15 to 100 microinches.

The gold plating layer 81 is formed on the nickel plating layer 82 at least 1 micro inch or more, and the nickel-gold plating layer 80b plated at the tip portion of the inner lead 72 provides good bonding reliability with the bonding wire 66. In addition, the nickel-gold plating layer 80a plated on the outer lead 74 realizes good soldering reliability with the solder. That is, since the gold bonding layer 66 and the gold plating layer 81 which are the same metal are formed in the front end surface of the inner lead 72, the favorable bonding reliability between the bonding wire 66 and the inner lead 72 is carried out. In addition, since the gold plating layer 81 plated on the external lead 74 also has good wetting, good soldering reliability with the solder can be ensured. That is, the gold plating layer 81 is theoretically impossible to form an oxide on the surface at the soldering process temperature of about 245 ° C. The gold plating layer 81, which is a thin film during soldering, instantly melts by atomic diffusion, and the nickel plating layer underneath ( 82) to facilitate the bonding of the solder.

By forming the nickel-gold plated layers 80a and 80b only at the front end portion of the inner lead 72 and the outer lead 74, the outer lead 74, which is the first bonding interface where moisture is absorbed into the semiconductor package 50, is formed. Since the portion of the inner lead 72 which is continued is a copper material which is not plated with the nickel-gold plating layers 80a and 80b, and forms an adhesive interface directly with the molding resin, the path of moisture absorption into the semiconductor package 50 is absorbed. Block it. That is, the reliability of the semiconductor package 50 due to moisture absorption can be prevented from falling.

Although FIG. 2 illustrates a semiconductor package 50 using a copper-based lead frame 70 having nickel-gold plating layers 80a and 80b formed thereon, as another embodiment of the present invention, a tin-gold (Sn-Au) plating layer may be used. It can also be implemented as a semiconductor package using the formed copper-based lead frame. Meanwhile, since the structure of the semiconductor package using the copper-based lead frame having the tin-gold plated layer is the same as that of the semiconductor package shown in FIG. 2, detailed descriptions of the illustration and structure of the separate drawings will be omitted. The reason why the plating layer of the gold plating layer is formed will be explained.

The tin plating layer is formed in the tip portion of the inner lead to which the bonding wire is bonded and on the surface of the outer lead to have a thickness of 30 to 70 micro inches. The reason for adopting such a tin plated layer is that tin has the same face-centered structure (FCC) as copper, so it is excellent in bonding with copper despite being copper and dissimilar metals, It is because adhesiveness is excellent.

Then, a gold plating layer is formed on the tin plating layer by plating with a thickness of at least 1 microinch or more. The reason for adopting the gold plating layer is almost the same as the reason for forming the gold plating layer in the above-described nickel-gold plating layer. That is, at the soldering process temperature of about 245 ° C, theoretically no oxide can be formed on the surface of the gold plating layer, and when soldering, the gold plating layer, which is a thin film, melts instantly by atomic diffusion, facilitating the bonding of tin and solder in the lower layer. to be.

On the other hand, the tin has a melting point of 232 ° C., which is significantly lower than the melting point of copper of 1083 ° C., when copper is diffused by thermal shock during the wire bonding process, the tin plated layer does not sufficiently prevent the diffusion of copper. An oxide can also be formed in. In other words, the gold plating layer is the most oxidatively stable metal, and since the gold plating layer prevents the diffusion and oxidation of the copper even though the tin plating layer does not prevent the diffusion of copper and the oxide is generated, the problems described above occur. I never do that.

On the other hand, in the embodiment according to the present invention has been described a conventional semiconductor package structure in which the semiconductor chip is mounted on the die pad, in the semiconductor package of the lead-on chip structure in which the tip portion of the inner lead is mounted on the upper surface of the semiconductor chip, Even if the nickel-gold plated layer or the tin-gold plated layer is formed on the front end of the inner lead and the outer lead to which the bonding wire is connected, it does not depart from the scope of the inventive concept.

Therefore, according to the structure of the present invention, since a nickel-gold plated layer or a tin-gold plated layer is formed at the tip of the inner lead and the outer lead, good wire bonding between the bonding wire and the inner lead and good solderability between the outer lead and the solder. Can be secured.

In addition, since the inner lead portion connected to the outer lead, which is the first adhesive interface with the molding resin forming the package body, is made of copper, it is possible to effectively block moisture absorbed through the first adhesive interface into the package body.

Claims (4)

(A) a semiconductor chip having a plurality of electrode pads formed on an upper surface thereof; (B) (a) a die pad to which the semiconductor chip is attached, (b) a plurality of internal leads extending toward the die pad, and (c) a plurality of external bodies formed integrally with the internal leads and extending out of the die pad. A copper-based lead frame including a lead; (C) a bonding wire for electrically connecting the electrode pad of the semiconductor chip and the internal lead; And (D) a package body formed by sealing the semiconductor chip, the bonding wire, and the inner lead with a liquid molding resin. The outer lead protruding out of the package body is bent in a mounting form, and a nickel plated layer and a gold plated layer are sequentially formed on the front end portion of the inner lead to which the bonding wire is bonded, and at a predetermined thickness on the surface of the outer lead. Semiconductor package. The semiconductor package of claim 1, wherein the nickel plating layer has a thickness of 15 to 100 microinch, and the gold plating layer has a thickness of 1 microinch or more. (A) a semiconductor chip having a plurality of electrode pads formed on an upper surface thereof; (B) (a) a die pad to which the semiconductor chip is attached, (b) a plurality of internal leads extending toward the die pad, and (c) a plurality of external bodies formed integrally with the internal leads and extending out of the die pad. A copper-based lead frame including a lead; (C) bonding wires electrically connecting the electrode pads of the semiconductor chip to the internal leads; And And (D) a package body formed by sealing the semiconductor chip, the bonding wire, and the inner lead with a liquid molding resin. The outer lead protruding out of the package body is bent in a mounting form, and a tin plated layer and a gold plated layer are sequentially formed on the front end portion of the inner lead to which the bonding wire is bonded, and the surface of the outer lead to a predetermined thickness. Semiconductor package. The semiconductor package of claim 1, wherein the tin plating layer has a thickness of 30 to 70 micro inches, and the gold plating layer has a thickness of 1 micro inch or more.