JP2006196648A - Electronic component having external junction electrode and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a junction electrode having both of solder junction reliability and improved gold wire-bonding properties inexpensively, and to provide a reliable and low-cost electronic component manufactured using a method for manufacturing the junction electrode. <P>SOLUTION: The electronic component having the external junction electrode comprises a ceramic base; an external connection electrode section formed on the ceramic base; an underlayer made of a metal film mainly comprising nickel or a nickel alloy formed on the surface of the external connection electrode section; an intermediate layer comprising palladium or a palladium alloy formed on the surface of the underlayer; and a surface covering layer comprising gold or a gold alloy formed on the surface of the intermediate layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bonding electrode for an electronic component and a method for manufacturing the same, for example, a ceramic electronic component in which a bonding electrode is formed on the surface of a substrate formed of a ceramic material, and a method for manufacturing the bonding electrode.

  With the downsizing of portable electronic devices, semiconductor packages are becoming popular in the Ball Grid Array (BGA) type that can be mounted at high density. The semiconductor chip is connected to the package substrate by gold wire bonding, and the package substrate is connected to the mother board by solder bonding.

  In order to ensure gold wire bonding and solder connection reliability, for example, phosphorous nickel plating and gold plating described in Japanese Patent Laid-Open No. 2003-183843 are applied on the electrode of the conductor formed on the surface of the base material. Japanese Patent Application Laid-Open No. 10-135607 proposes a two-layer nickel and gold plating technique using boron-based nickel plating together. According to these technologies, wettability is ensured by the gold film on the outermost surface at the time of solder joining, and an alloy layer with solder is formed by a nickel film, thereby obtaining good joint strength. The nickel film also has a barrier function to prevent the conductor of the base electrode from being eroded by the solder.

On the other hand, for gold wire bonding, for example, the gold film thickness is preferably 0.3 μm or more (Chino et al .: MES2000, 11, 299 (2000): hereinafter referred to as Document 1). The reason for this is that nickel diffuses in the gold film due to heat treatment during wire bonding and segregates on the outermost surface, hindering metal-to-metal bonding in wire bonding. Is valid. Therefore, a gold film thickness of 0.3 μm or more is necessary to prevent nickel segregation on the outermost surface. It is also suggested that nickel diffusion occurs through pinholes generated during the gold plating of the surface layer, suggesting a decrease in strength due to interfacial corrosion between the nickel layer and the gold layer (Watanabe: Surface Technology, vol53, No1 , 22 (2002): Reference 2 below).
JP2003-183843 JP-A-10-135607

  In the prior art, each of the base electrodes consists of two layers of nickel plating and gold plating. In this configuration, it is essential to form a gold plating film with good adhesion on the nickel film. Therefore, it is common to use a displacement type gold plating solution. That is, electrons are taken out by dissolving a nickel film on the surface to be plated in a gold plating solution, and the electrons are used for reduction of gold ions. By this substitution reaction, a gold film having good adhesion is deposited on the nickel film. However, since the nickel elution site and the gold deposition site are different, the substitution gold plating film tends to generate pinholes. Therefore, there is a problem that nickel is easily segregated on the surface through the pinhole, and as a result, the wire bonding property is lowered. Further, the displacement gold plating reaction decreases as the nickel surface is covered with gold, and only about 0.1 μm is practically deposited. Thus, in order to obtain gold having a thickness of 0.3 μm necessary for gold wire bonding, further, two-step gold plating using an autocatalytic gold plating solution is required, which increases the cost. Also, even if the gold film is thickened to about 0.3 μm by thick gold plating and apparently the pinhole disappears, the nickel film and the gold film due to nickel elution during the gold plating until the pinhole is sealed There was a problem that the interfacial corrosion progressed and adversely affects the solder connection reliability.

  The present invention has been made in view of such problems, and is manufactured at low cost by using a bonding electrode having both solder bonding reliability and good gold wire bonding property and a method for manufacturing the bonding electrode. An object is to provide an electronic component with excellent reliability.

  Focusing on the fact that the gold film on the nickel film generates many pinholes due to the substitution reaction, and earnestly researched to obtain a method for forming a plating film with excellent adhesion without using the substitution reaction on nickel. It was found that a reduced palladium plating film was deposited on the film with good adhesion, and that gold on the palladium plating film was able to obtain good gold wire bonding even by substitutional single-step gold plating.

  The present invention has been made based on such knowledge, and the first invention of the present application is a ceramic base, an external connection electrode formed on the ceramic base, and formed on the surface of the external connection electrode. An underlayer made of a nickel or nickel alloy-based metal film, an intermediate layer made of palladium or a palladium alloy formed on the surface of the underlayer, and a gold or gold alloy formed on the surface of the intermediate layer It is an electronic component with an external joining electrode characterized by including the surface coating layer which becomes.

  The external connection electrode part is preferably made of silver or a silver alloy. There is a firing process in manufacturing a ceramic substrate, but if it can be fired in the air instead of an inert atmosphere (nitrogen or the like), there is a great cost advantage. Silver or a silver alloy is preferable as the metal that does not oxidize when fired in the air.

  The film thickness of the underlayer is preferably 2 to 15 μm. In the case of solder connection, if the base layer is thinner than 2 μm, the solder reaches the external connection electrode part due to diffusion of the solder and the base layer, and the solder biting of the electrode part occurs, which is not preferable. On the other hand, when it is thicker than 15 μm, it is too thick to prevent solder erosion, which is useless without any special effect.

  The thickness of the intermediate layer is preferably 0.05 to 1.0 μm. If it is thinner than 0.05 μm, the intermediate layer may disappear due to the displacement gold plating reaction of the surface coating layer. On the other hand, if it is thicker than 1.0 μm, a special effect cannot be obtained and it becomes useless.

  The thickness of the surface coating layer is preferably 0.03 to 0.2 μm. When soldered, if the surface coating layer is thinner than 0.03 μm, sufficient solder wettability cannot be ensured. On the other hand, if it is thicker than 0.2 μm, there is no special effect on the solder wettability and it is wasted. The reason why the thickness can be limited to be smaller than the film thickness (0.3 μm) of the above-described prior art is that the intermediate layer Pd also has some solder wettability.

The second invention of the present application forms a base layer made of a metal film mainly composed of nickel or a nickel alloy on the surface of the external connection electrode portion formed on the ceramic substrate,
An intermediate layer made of palladium or a palladium alloy is formed on the surface of the underlayer by reduced palladium plating,
A method of manufacturing an electronic component with an external bonding electrode, wherein a surface coating layer mainly composed of gold or a gold alloy is formed on a surface of the intermediate layer by substitutional gold plating.
The reduction type plating solution and the substitution type plating solution can use commercially available plating solutions, and are not limited. The plating conditions can be the same as the handling conditions for each commercially available plating solution.

  The underlayer, intermediate layer and surface coating layer are preferably formed by electroless plating. The electroless plating method has a merit that plating can be applied to an electrically isolated electrode portion because plating deposition proceeds by a chemical reaction. On the other hand, in order to use the electrolytic plating method, it is necessary to form a lead-out wiring for supplying power to the electrode part, which is not only disadvantageous for high-density wiring formation, but also because the lead-out wiring itself serves as an antenna, it is used at high frequency If it causes noise.

  In the method for manufacturing an electronic component according to the present invention, an electroless nickel plating is applied as a base layer to an object to be plated on which a bonding electrode is formed on the substrate surface, followed by electroless palladium plating as an intermediate layer. It is characterized in that a substitutional gold plating film is formed as a surface layer. The electroless nickel plating can use at least one of phosphorous and boron.

  An intermediate layer of palladium plating is applied onto the nickel film of the underlayer, and the palladium plating solution is excellent in adhesion even when a reduced plating solution is used. That is, since the potential difference between nickel and palladium is as very small as about 1.24 V, nickel elution hardly occurs during palladium plating. Therefore, there is no need to ensure adhesion by substitutional plating in which pinholes are likely to occur in the plating film, and reduction-type palladium plating with few pinholes can be performed. This made it possible to suppress the diffusion of nickel into the surface layer.

  Moreover, in order to ensure good bondability using a gold wire, the metal bond becomes stronger when the bonding electrode side is also made of the same metal. Therefore, it is desirable that the outermost surface of the bonding electrode of the base material is gold, and a gold plating film is formed on the surface of the palladium film. Further, since the gold film thickness does not need to prevent nickel diffusion as in Document 1, it is possible to reduce the thickness of the gold film, which is a low-cost manufacturing method.

  According to the present invention, there is provided an electrode having a surface coating layer on an electrode forming portion of a conductor formed on the surface of a base material, and a metal film mainly composed of nickel or a nickel alloy on the surface of the electrode forming portion. An intermediate layer made of palladium or palladium alloy formed by reduced palladium plating on the surface of the underlying layer and a substitutional gold plating formed on the surface of the intermediate layer. By forming the surface coating layer made of gold or gold alloy and having no interfacial corrosion, it is possible to provide an electronic component excellent in gold wire bondability and solder joint reliability.

  Next, embodiments of the present invention will be described below with reference to the drawings. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

  FIG. 1 is a cross-sectional view schematically showing one embodiment of an electronic component manufactured by the method for manufacturing a ceramic electronic component according to the present invention. In the package substrate shown in the figure, an internal wiring 2 made of silver or a silver alloy is formed in the inner layer of the ceramic substrate 1, and this is electrically exposed to the external connection electrode portion 3 formed exposed on the surface of the substrate. Configured to be connected. The surface of the external connection electrode portion 3 is coated with nickel or a nickel alloy film 5 as a base layer, and the surface of the base layer is coated with palladium or a palladium alloy film 6 as an intermediate layer. Further, a gold film 7 is applied as a surface coating layer on the surface of the intermediate layer.

  Next, a method for manufacturing the electrode 10 of the electronic component will be described. First, the ceramic substrate 1 including the wiring 2, the external connection electrode portion 3, and the insulating layer 4 formed through predetermined molding and firing treatment was produced. Next, in order to form a film by the electroless plating method on the surface of the external connection electrode part 3, the following pretreatment for plating was performed.

(Preprocessing)
The ceramic substrate was immersed for 1 minute in a degreasing solution (trade name: Z-200, manufactured by World Metal) heated to 40 ° C. Then, after washing using a three-stage washing tank, it was immersed in a 10% sulfuric acid aqueous solution at room temperature for 1 minute. Then, after washing in a three-stage water washing tank, in order to activate the surface of the silver electrode, it was immersed in an activating solution (trade name: PB-300, manufactured by Ebara Eugelite) at room temperature for 1 minute. Then, it was washed in a three-stage water washing tank.

[Example 1]
The pretreated ceramic base material was immersed in an electroless nickel-phosphorous plating solution (trade name: ENIPAK LV, manufactured by Ebara Eugene Corporation) at 90 ° C. to form a nickel-phosphorous film having a thickness of about 2 μm. Then, after washing in a three-stage water washing tank, it was immersed in a reduced electroless palladium plating solution (trade name: Palette II, manufactured by Kojima Chemical Co., Ltd.) at 70 ° C. to form a palladium film of about 0.05 μm. Immediately after washing in a three-stage water-washing tank, it was immersed in a substitutional electroless gold plating solution (trade name: NC Gold MP, manufactured by Kojima Chemical Co., Ltd.) at 75 ° C. to form a gold film of about 0.03 μm. Segregation of nickel on the gold plating surface layer was not observed. Further, no interfacial corrosion was observed at any interface. After hot air drying, gold wire bonding evaluation and solder ball shear test were performed. As the gold wire bonding apparatus, Shinkawa Co., Ltd. (UTC-100) was used, and bonding was performed at a stage temperature of 170 ° C. using a 27 μm gold wire. In addition, the tensile tester after bonding was made by Resuka (PRT-1000) and measured at a tensile speed of 0.5 mm / sec. On the other hand, in the ball shear test, a eutectic solder ball was mounted at a position corresponding to the electrode 10 and then reflowed and connected at 225 ° C. And it broke with the bond tester, and the fracture mode was confirmed by observing the solder ball fracture part with a stereomicroscope.

[Example 2]
Using the same ceramic substrate 1 as in Example 1, the surface of the external connection electrode portion 3 is approximately 8 μm in nickel-phosphorus film, approximately 1.0 μm in palladium film and approximately 0.1 μm in gold film on the surface of the external connection electrode part 3 in the same procedure as in Example 1. μm was formed. Segregation of nickel on the gold plating surface layer was not observed. Further, no interfacial corrosion was observed at any interface. Then, a gold wire bonding test and a ball shear test were performed in the same procedure as in Example 1.

[Example 3]
Using the same ceramic substrate 1 as in Example 1, the surface of the external connection electrode part 3 was coated with a nickel-phosphorus film of about 15 μm, a palladium film of about 0.4 μm and a gold film of about 0.2 in the same procedure as in Example 1. μm was formed. Segregation of nickel on the gold plating surface layer was not observed. Further, no interfacial corrosion was observed at any interface. Then, a gold wire bonding test and a ball shear test were performed in the same procedure as in Example 1.

[Comparative Example 1]
The pretreated ceramic base material 1 was immersed in an electroless nickel-phosphorus plating solution (trade name: ENIPAK LV, manufactured by Sugawara Eugleite Co., Ltd.) at 90 ° C. to form a film of about 2 μm. After washing in a three-stage water washing tank, the film was immersed in a substitutional electroless gold plating solution (trade name: Supermex # 250, manufactured by NEM Chemcat) at 70 ° C. to form a film of about 0.03 μm. Segregation of nickel on the gold-plated surface layer due to local battery reaction was observed. During gold plating, interfacial corrosion between nickel film and gold film progressed due to nickel elution. After hot air drying, gold wire bonding evaluation and solder ball shear test were performed. As the gold wire bonding apparatus, Shinkawa Co., Ltd. (UTC-100) was used, and bonding was performed using a 27 μm gold wire at a stage temperature of 170 ° C. In addition, the tensile tester after bonding was made by Reska Co. (PRT-1000) and measured at a tensile speed of 0.5 mm / sec. On the other hand, in the ball share test, a eutectic solder ball was mounted at a position corresponding to the electrode 10 and then reflowed at 225 ° C. for connection. And it fractured | ruptured with the bond tester, and the fracture mode was confirmed by observing the solder ball fracture | rupture part with a stereomicroscope.

[Comparative Example 2]
Using the same ceramic substrate 1 as in Comparative Example 1, a nickel-phosphorous film was formed on the surface of the external connection electrode part 3 in the same procedure as in Example 1 by about 8 μm. After washing in a three-stage water washing tank, the film was immersed in a substitutional electroless gold plating solution (trade name: Supermex # 250, manufactured by NEM Chemcat) at 70 ° C. to form a film of about 0.03 μm. Subsequently, after washing in a three-stage water washing tank, it was immersed in a reduced electroless gold plating solution (trade name: Supermex # 850, manufactured by NEM Chemcat) at 70 ° C. to form a film of about 0.1 μm. Segregation of nickel on the gold-plated surface layer due to local battery reaction was observed. During thick gold plating, interfacial corrosion between nickel film and gold film progressed due to nickel elution. Then, a gold wire bonding test and a ball shear test were performed in the same procedure as in Example 1.

[Comparative Example 3]
Using the same ceramic substrate as in Comparative Example 1, a nickel-phosphorous film was formed on the surface of the external connection electrode portion 3 in the same procedure as in Example 1 by about 8 μm. After washing in a three-stage water washing tank, the film was immersed in a substitutional electroless gold plating solution (trade name: Supermex # 250, manufactured by NEM Chemcat) at 70 ° C. to form a film of about 0.03 μm. Subsequently, after washing in a three-stage water washing tank, it was immersed in a reduced electroless gold plating solution (trade name: Supermex # 850, manufactured by NEM Chemcat) at 70 ° C. to form a film of about 0.2 μm. During thick gold plating, interfacial corrosion between nickel film and gold film progressed due to nickel elution. Although the gold film was thickened by reduction-type electroless gold plating, the thickness was insufficient, 0.2 μm, so the nickel diffusion path was not completely blocked and some segregation of nickel on the gold plating surface layer was observed. It was. Then, a gold wire bonding test and a ball shear test were performed in the same procedure as in Example 1.

Table 1 shows the measurement results.

As is apparent from Table 1, the gold wire bonding strength in the external connection electrode portion of the present invention is superior to that of the prior art even if the gold film thickness of the surface coating layer is the same, and the solder connectivity is interface fracture. It was confirmed that it was excellent in reliability without any occurrence. In the comparative example, it was confirmed that both the bondability and the solder connection reliability were inferior to those of the examples. According to the present invention, it has been found that reduction type electroless gold plating which is a cause of high cost can be eliminated. Reduced electroless palladium plating is significantly less expensive than reduced electroless gold plating.

  The present invention relates to a bonding electrode for an electronic component and a method for manufacturing the same, for example, a ceramic electronic component in which a bonding electrode is formed on the surface of a substrate formed of a ceramic material, and a method for manufacturing the bonding electrode. According to the present invention, it is possible to provide a low cost and highly reliable electronic component manufactured by using a bonding electrode that is inexpensive and has both solder bonding reliability and good gold wire bonding property and a manufacturing method thereof. it can.

It is the figure which showed typically the cross section of the electronic component of this invention.

Explanation of symbols

1: Ceramic base material 2: Internal wiring 3: External connection electrode part 4: Insulating layer 5: Underlayer 6: Intermediate layer 7: Surface coating layer 10: Electrode

Claims (7)

A ceramic base, an external connection electrode formed on the ceramic base, a base layer made of a metal film mainly composed of nickel or a nickel alloy formed on the surface of the external connection electrode, and a surface of the base layer An electronic component with an external bonding electrode, comprising: an intermediate layer made of palladium or a palladium alloy formed thereon; and a surface coating layer made of gold or a gold alloy formed on the surface of the intermediate layer. 2. The electronic component with an external bonding electrode according to claim 1, wherein the external connection electrode portion is made of silver or a silver alloy. 2. The electronic component with an external bonding electrode according to claim 1, wherein the underlayer is 2 to 15 [mu] m. 2. The electronic component with an external bonding electrode according to claim 1, wherein the intermediate layer is 0.05 to 1.0 [mu] m. 2. The electronic component with an external joining electrode according to claim 1, wherein the surface coating layer is 0.03 to 0.2 [mu] m. On the surface of the external connection electrode part formed on the ceramic substrate, a base layer made of a metal film mainly composed of nickel or a nickel alloy is formed,
An intermediate layer made of palladium or a palladium alloy is formed on the surface of the underlayer by reduced palladium plating,
A method of manufacturing an electronic component with an external bonding electrode, comprising forming a surface coating layer mainly composed of gold or a gold alloy on a surface of the intermediate layer by substitutional gold plating. 7. The method of manufacturing an electronic component with an external bonding electrode according to claim 6, wherein the underlayer, the intermediate layer, and the surface coating layer are formed by an electroless plating method.

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