JP2004260147A - Soldering method and method for manufacturing component-packaged substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein deterioration is produced at a joint, when an electronic circuit board is used under a high-temperature and high-humidity environment in soldering, with a solder having the basic composition of Sn and Zn, even although the heat damage to electronic components is relieved more than that in the case of solder formed of Sn and Ag. <P>SOLUTION: On the bonding interface of a Cu surface at a part where a circuit board joins with an electronic component, a compound of Cu and Sn or an alloy 12 are formed. By using a soldering material 11 containing Sn and Zn in a composition to solder, deterioration of the joint due to a Cu-Zn compound layer is prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a soldering method for mounting components on an electronic circuit board, and a method for manufacturing a component mounting board for soldering a circuit board and an electronic component.

  In recent years, with respect to electronic component mounting, there has been an increasing demand for improvement in mechanical strength of soldered portions and improvement in reliability characteristics such as thermal shock strength. On the other hand, with the growing interest in global environmental protection, laws and regulations on the treatment of industrial waste such as electronic circuit boards are also advancing. Therefore, it is necessary to develop soldering that satisfies both of these requirements.

  By the way, the main constituent components of the conventional solder material are Sn and Pb, and have a composition of 63Sn-37Pb.

  Hereinafter, a joint structure between an electronic component and an electronic circuit board in a conventional soldering method using a solder material will be described with reference to the drawings.

  FIG. 3 is a schematic view showing a joining structure using a conventional solder material. In FIG. 3, reference numeral 1 denotes a solder material, whose constituent components are Sn and Pb, 2 denotes an electrode of an electronic component, 3 denotes a land of an electronic circuit board, the constituent component is Cu, and 4 denotes CuSn of a compound layer formed at a bonding interface. is there. The melting point of the conventional solder material is relatively low, and the reliability of the joint under a high temperature and high humidity environment is practically sufficient. However, as described above, a solder material using Pb is not preferable from the viewpoint of global environmental protection.

  Therefore, it is conceivable to use a lead-free solder which is a solder material containing no lead. A solder composed of Sn and Ag as main components, which is an example of lead-free solder, has a melting point higher by 30 to 40 ° C. than Sn—Pb solder, and has a higher soldering temperature than lead-containing solder. Therefore, the soldering temperature may be higher than the heat-resistant temperature of the electronic component, and there is a problem that the electronic component is damaged. In addition, there was a problem that the wettability was inferior to that of the Sn-Pb solder.

  It has also been considered to use a solder having a basic composition of Sn and Zn whose melting point is higher by 10 to 20 ° C. than that of the Sn—Pb solder.

FIG. 4 is a schematic diagram showing a bonding structure using a solder material having a basic composition of Sn and Zn. In FIG. 4, reference numeral 5 denotes an Sn—Zn solder, and reference numeral 6 denotes a Cu—Zn compound layer formed at a bonding interface of the land 3 as a material to be bonded.
JP-A-09-094688 (pages 2-4)

  In the soldering using the solder having Sn and Zn as basic compositions, the thermal damage of the electronic component is reduced, but the deterioration of the joint portion when the electronic circuit board is used in a high-temperature and high-humidity environment becomes a problem. . It is considered that Zn existing on the surfaces of the Cu—Zn compound layer 6 and the Sn—Zn solder 5 elutes in a high-temperature and high-humidity environment, which is a cause of deterioration.

  SUMMARY OF THE INVENTION An object of the present invention is to realize a bonded portion of an electronic circuit board having excellent resistance to high temperature and high humidity.

  In order to achieve this object, the present invention provides a method of forming a compound or alloy of Cu and Sn at a bonding interface of a Cu surface at a bonding portion and performing soldering using a solder material containing Sn and Zn in a composition. It is a feature.

  This makes it possible to prevent the deterioration of the joint due to the Cu—Zn compound layer.

  Further, by joining the circuit board and the electronic component by using this soldering, it is also possible to manufacture a component mounting board having a joint having excellent resistance to high temperature and humidity.

  As described above, according to the present invention, a compound or an alloy of Cu and Sn is formed at a bonding interface of a Cu surface at a bonding portion, and soldering is performed using a solder material containing Sn and Zn in a composition. An advantageous effect of preventing the deterioration of the joint due to the Cu-Zn compound layer can be obtained.

  Further, by joining the circuit board and the electronic component by using this soldering, it is also possible to manufacture a component mounting board having a joint having excellent resistance to high temperature and high humidity.

  Hereinafter, the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted.

  FIG. 1 is a schematic diagram showing a joint structure using a solder material having a basic composition of Sn and Zn according to an embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a Sn—Zn solder, 12 denotes a Cu—Sn compound layer formed at a bonding interface, 13 denotes a land as a material to be bonded, and 14 denotes an electronic component electrode.

  The melting point of the Sn-Zn solder 11 is higher than that of the Sn-Pb solder by about 10 to 20 ° C. By the way, during the development, if the compound or alloy of Cu and Sn is formed on the Cu surface of the land 13 on the electronic circuit board and soldered, the Cu base material and the Sn—Zn solder 11 are formed. It has been found that Zn reacts directly to suppress the formation of a Cu—Zn compound. Then, it was also found that, when the thickness of the compound or alloy of Cu and Sn exceeds 5 μm, the compound or alloy of Cu and Sn has a property of being hard and brittle, so that the interface strength decreases. Therefore, when a compound or alloy of Cu and Sn having a thickness of 5 μm or less is formed on the surface of Cu of the land 13 on the electronic circuit board and soldered, the Cu base material and Zn of the Sn—Zn solder 11 are directly connected. The formation of a Cu—Zn compound by the reaction was suppressed, and a joint having excellent resistance to high temperature and high humidity was obtained.

  Also, by adding a metal, for example, Ni, which is more easily oxidized than Zn, in the solder in advance, an oxide film of the added metal can be preferentially formed on the solder surface. FIG. 2 is a schematic diagram showing a bonding structure using a solder material having a basic composition of Sn and Zn and a small amount of Ni added according to the embodiment of the present invention. In FIG. 2, reference numeral 15 denotes a solder material having a basic composition of Sn and Zn and a small amount of Ni added, and reference numeral 16 denotes a Ni oxide film. The Ni oxide film 16 has a function to prevent the elution of Zn in the solder under high temperature and high humidity. The amount of Ni added to the solder is preferably 0.1% by weight or less, more preferably 0.01% by weight or less. If the amount of Ni exceeds 0.1% by weight, the wettability of the solder is remarkably reduced, and there is a problem that sufficient soldering quality cannot be secured. The Zn content at this time is desirably 5 to 10% by weight. Further, it is preferable that Bi is contained in the solder material in an amount of 0.1 to 5.0% by weight.

  The same effect can be obtained by adding a small amount of Al, Si, In, Mn, Ge, Mo, P, or the like, which is a metal that is easily oxidized than Zn and does not elute under high temperature and high humidity, into the solder.

  Meanwhile, as a method of forming a compound of Cu and Sn, there is a method of performing a heat treatment after coating a metal containing Sn on the Cu surface. The coating of the metal containing Sn on the Cu surface is also possible by plating or dipping or vapor deposition in molten metal. Then, for coating by plating and vapor deposition, it is necessary to form a compound layer of Cu and Sn at the bonding interface by heat treatment. Regarding the method of dipping in a molten metal, when a compound layer of Cu and Sn is further grown by heat treatment, the formation of a Cu—Zn compound layer can be suppressed, and a bonded portion having excellent resistance to high temperature and high humidity can be obtained.

  Examples of the type of coating include Sn coating, Ag coating, Sn-Bi coating, Sn-Ag coating, Sn-Cu coating, Sn-Ag-Cu coating, and Sn-Ag-Bi coating. The thickness of the coating is desirably 10 μm or less. If the thickness exceeds 10 μm, the coated metal may be melted in the solder at the time of soldering, or may remain at the interface even if not melted, thereby deteriorating the joint characteristics.

  Furthermore, although the one formed at the bonding interface is a Cu-Sn compound layer, it may be an alloy layer.

  Further, a similar effect can be obtained by preparing a compound or alloy of Cu and Sn in advance and installing the compound or alloy in a soldered portion.

  In addition to covering the Cu lands of the electronic circuit board, the same effect can be obtained for covering the terminal electrodes of the electronic components.

  Further, by soldering the circuit board and the electronic component using the above method, it is also possible to manufacture a component mounting board having a joint having excellent resistance to high temperature and humidity.

FIG. 1 is a schematic diagram showing a joint structure using a solder material having a basic composition of Sn and Zn according to an embodiment of the present invention. Schematic diagram showing a joint structure using a solder material containing Sn and Zn as basic components and a small amount of Ni added according to an embodiment of the present invention. Schematic diagram showing joining structure using conventional solder material Schematic diagram showing a joint structure using a solder material having a basic composition of Sn and Zn

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 11 Sn-Zn solder 12 Cu-Sn compound layer 13 Land 14 Electronic component electrode 15 Solder which added a small amount of Ni 16 Ni oxide film

Claims (10)

A soldering method comprising forming a compound or alloy of Cu and Sn at a bonding interface on a Cu surface of a bonding portion, and performing soldering using a solder material containing Sn and Zn in a composition. The soldering method according to claim 1, wherein the thickness of the compound or the alloy is 5 µm or less. 3. The soldering method according to claim 1, wherein the method of forming a compound of Cu and Sn includes performing heat treatment after coating a metal containing Sn on the Cu surface. The coating is any one of Sn coating, Ag coating, Sn-Bi coating, Sn-Ag coating, Sn-Cu coating, Sn-Ag-Cu coating, and Sn-Ag-Bi coating. The soldering method described in 1. The soldering method according to claim 3, wherein the coating method is any one of a plating method, an immersion method, and a vapor deposition method. The soldering method according to any one of claims 3 to 5, wherein the thickness of the coating is 10 µm or less. 2. The soldering method according to claim 1, wherein a metal which is more easily oxidized than Zn is added to the solder in advance. The soldering method according to claim 7, wherein the metal added to the solder is Ni, Si, Al, In, Mn, Ge, Mo, or P. 9. The soldering method according to claim 8, wherein the amount of the metal added to the solder is 0.1% by weight or less. A method for manufacturing a component mounting board, comprising: soldering a circuit board and an electronic component by the method according to claim 1.

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