JP2005057117A - Soldering method, joining structure, and electric/electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent the deterioration of a soldered part (or a joined part) owing to the continuous use thereof under a high temperature condition, that is a typical problem caused when an electric/electronic component is soldered to a substrate using a soldering material containing Sn and Zn such as an Sn-Zn based material as a soldering material, and to ensure enough heat resistant fatigue strength. <P>SOLUTION: When the land 2 of the substrate 1 and the lead 6 of an electronic component 5 are soldered using a soldering material containing Sn and Zn, the surfaces of the land 2 and the lead 6 are covered with coating layers 3, 7 comprising a material containing Ag. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a soldering method for soldering members to be joined together, a joining structure to which the soldering method is applied, and an electrical / electronic component.

  2. Description of the Related Art Conventionally, in the manufacturing process of an electronic circuit board used in an electronic device or the like, for example, in order to mount an electronic component on the substrate, more specifically, a lead drawn from the electronic component and a land formed on the substrate are electrically and As one of the methods used for physical joining, a reflow soldering method is known.

  In a general reflow soldering method, cream solder is first supplied by screen printing onto lands that are part of a wiring pattern formed on a substrate. Cream solder is usually configured by mixing a solder powder made of a solder material and a flux made of rosin, an activator, and a solvent.

  After supplying the cream solder, the electronic component is disposed at a predetermined position on the substrate so that the lead drawn out from the electronic component to be bonded adheres to the cream solder disposed on the land of the substrate. The solder material which activates the flux by heat-treating the substrate on which the electronic components are arranged via the cream solder in this way at a temperature equal to or higher than the melting point of the solder material to be used and constitutes the solder powder in the cream solder. Is once melted and other components such as flux in the cream solder are evaporated (or volatilized). Next, the molten solder material is solidified by cooling (or allowing to cool).

  The solidified solder material forms a joint between the lead of the electronic component and the land of the substrate, and joins both electrically and physically. There may be other components such as flux other than the solder material in the joint, but such other components are phase-separated from the solder material during the heat treatment, and therefore do not exist inside the joint. It can be slightly left on the joint surface. As a result, an electronic circuit board in which the electronic component is mounted on the substrate is obtained by the joint portion (or soldering portion) made of the solder material.

  As a solder material, an Sn—Pb-based material, particularly one having a eutectic composition (hereinafter also simply referred to as “Sn—Pb eutectic material”) is generally used. The eutectic composition of the Sn—Pb-based material is the Sn-37Pb composition (that is, a composition comprising 37% by weight of Pb and the balance (63% by weight) of Sn). In this eutectic composition, the Sn—Pb-based material is It is known to have a melting point of 183 ° C.

  In recent years, disposal methods for electronic devices including the electronic circuit board as described above have begun to be regarded as problems, and there is concern about the influence of the lead (Pb) contained in the solder material on the global environment and the human body.

For this reason, instead of the Sn-Pb-based material that has been conventionally used as a solder material, there is a movement to use a lead-free solder material, that is, a lead-free solder material, and its practical use has been attempted. (See Patent Document 1).
JP 2001-284785 A

  Currently, materials having various compositions have been proposed as lead-free solder materials, one of which is a Sn—Zn-based material. As a result of recent research, the eutectic composition of the Sn—Zn-based material is approximately the Sn-9Zn composition (that is, a composition comprising 9 wt% Zn and the balance (91 wt%) Sn). It has been found that Sn—Zn-based materials have a melting point of 199 ° C.

  Considering the heat-resistant temperature of electronic components to be mounted on a substrate and the application of existing soldering methods, the melting point of lead-free solder materials is sufficiently low to prevent damage to electronic components, and conventional Sn-Pb-based materials It is desirable that the melting point is relatively close. The melting point of the Sn—Zn-based material is lower than the melting point of other lead-free solder materials such as Sn—Ag-based material, and is relatively close to the melting point of the Sn—Pb-based material. It is regarded as a promising alternative to Sn—Pb materials.

  However, the use of Sn—Zn-based material instead of Sn—Pb-based material has the advantage that the electronic component can be soldered to the substrate while avoiding thermal damage of the electronic component. As a result of subjecting the circuit board to a continuous use test under a high temperature condition, it was found that the joint portion between the land of the board and the lead of the electronic component was deteriorated and sufficient heat fatigue strength could not be obtained.

  This is because zinc (Zn) contained in the Sn—Zn-based material comes into contact with copper (Cu) used as a land and lead material, and between the junction and the land and between the junction and the lead. This is thought to be due to the formation of an intermetallic compound composed of Cu—Zn at the bonding interface.

  Hereinafter, referring to FIG. 2, in the conventional reflow soldering method described above, an electronic component is soldered to a substrate using cream solder containing solder powder made of Sn—Zn material instead of Sn—Pb material. The attached electronic circuit board will be described.

  In this electronic circuit board, the lands 9 formed on the board 8 and the leads 13 drawn out from the electronic component 12 are joined electrically and mechanically via the joint 11. The land 9 is generally made of Cu and is formed integrally with the wiring pattern. The lead 13 is generally formed by coating a base material made of Cu with a plating 14 made of a Sn—Pb eutectic material. The joint portion 11 is formed by heat-treating cream solder and is substantially composed of a solder material derived from solder powder as described above.

  Currently, lead-free materials are also being promoted for lead materials for electronic components. However, Sn-Pb-based materials may still be used in the transition period as in the present situation.

  During the heat treatment, since the solder material and the land 9 are in direct contact, Cu constituting the land 9 diffuses into the solder material and bonds with Zn, and an intermetallic compound composed of Cu—Zn at this contact interface. 10 is formed.

  In addition, during the heat treatment, the solder material of the solder powder is melted, and the plating 14 made of the Sn—Pb eutectic material having a melting point lower than the heat treatment temperature is also melted to come into contact with the molten solder material. The portion 14 melts and diffuses in the solder material. For this reason, the plating 14 of the lead 13 is partially peeled off, and the base material comes into direct contact with the molten solder material.

  Accordingly, Cu constituting the base material of the lead 13 is diffused into the solder material and bonded to Zn in the same manner as described above, and the intermetallic compound 15 made of Cu—Zn is formed at this contact interface.

  In particular, when the substrate 8 to which the electronic component 12 is soldered as described above is placed under a high temperature condition for a long time, a larger amount of Cu diffuses into the joint (or solder material) 11 and a metal made of Cu—Zn. Formation of intermetallic compounds 10 and 15 proceeds. Eventually, when all of the Zn in the solder material is consumed for the formation of the intermetallic compound composed of Cu—Zn, then the remaining Cu and / or Cu—Zn metal without contributing to the formation of the intermetallic compound Interdiffusion occurs in which Cu constituting the intermetallic compound diffuses into the solder material, and the voids generated by the diffusion of Cu and the Sn in the solder material diffuse and move. It is considered that such a phenomenon causes deterioration of the joint portion.

  Note that copper (Cu) used as a land and / or lead material diffuses into the joint even when a cream solder containing solder powder made of Sn—Pb-based material is used as in the past. Then, by bonding with tin (Sn) contained in the Sn—Pb-based material, an intermetallic compound composed of Sn—Cu can be formed at the bonding interface between the bonding portion and the land and / or the lead.

  However, since the intermetallic compound made of Sn—Cu is stable, it can withstand continuous use under high temperature conditions. Therefore, even if the intermetallic compound made of Sn—Cu is formed, it is considered that the problem of deterioration of the joint portion as in the case of the intermetallic compound made of Cu—Zn did not occur.

  In addition to Cu, an Fe-42Ni alloy material (that is, an alloy material having a composition of 42 wt% Ni and the balance (58 wt%) Fe) is used as the base material of the lead 13. There is a case. In this case, even if the plating 14 of the lead 13 melts and diffuses into the solder material and the base material and the solder material are in direct contact with each other, a metal made of Cu—Zn is present at the interface between the lead 13 and the joint 11. Intermetallic compound 15 is not formed.

  However, since the intermetallic compound 12 made of Cu—Zn is still formed at the interface between the land 9 made of Cu and the joint 11, the obtained electronic circuit board was subjected to a continuous use test under a high temperature condition. Therefore, there is an unavoidable problem that the joint 11 is deteriorated and sufficient thermal fatigue strength cannot be obtained.

  As described above, the case of the Sn—Zn-based material has been described in detail, but the same problem may occur with other solder materials containing at least Sn and Zn.

  An object of the present invention is a high temperature condition, which is a problem peculiar to soldering (or joining) an electric / electronic component to a substrate using a solder material containing Sn and Zn such as a Sn—Zn-based material as a solder material. Degradation of the soldered part (or joint) due to continuous use under the above can be effectively prevented, and a soldering method capable of obtaining sufficient thermal fatigue strength, and this soldering method is applied. It is to provide a joint structure and an electrical / electronic component.

  In order to achieve the object, a soldering method according to the present invention is a soldering method in which a solder material containing Sn and Zn is used to solder between a first member and a second member, A method of forming a layer to be coated with a material containing Ag on at least one of the first member and the second member, that is, a solder material containing Sn and Zn such as a Sn—Zn-based material A method of soldering (or joining) between the first member and the second member using the method, wherein at least one of the first member and the second member contains Cu A base material made of a material and an Ag layer covering the base material are provided. The solder material is supplied (or arranged) between the first member and the second member, and the solder material is brought into contact with the Ag layer in a molten state. And diffuse Ag in the solder, By Zn reaction coagulation in I is a method for soldering between the first member and the second member.

  According to the soldering method as described above, the base material made of a material containing Cu is coated on the Ag layer, the solder material containing Sn and Zn is in contact with the Ag layer, and Ag diffuses into the solder. Therefore, Zn in the solder material is prevented from coming into direct contact with Cu contained in the base material. Thereby, formation of the intermetallic compound which consists of Cu-Zn can be suppressed or prevented effectively, Therefore, deterioration of the soldering part (joining part) by continuous use under high temperature conditions, and also heat-resistant fatigue strength The cause of the decrease can be eliminated.

  In addition, the bonded structure according to the present invention is a bonded structure in which the first member and the second member are soldered using a solder material containing Sn and Zn. At least one of the member and the second member includes a base material made of a material containing Cu and a layer made of a material containing Ag that covers the base material, A joint structure in which a first member and a second member are soldered using a solder material containing Sn and Zn, and at least one of the first member and the second member is made of Cu. The base material which consists of the material which contains and the Ag layer which coat | covers a base material are provided with the layer which reacted with Zn in solder.

  In such a bonded structure, since the formation of an intermetallic compound composed of Cu-Zn can be effectively suppressed or prevented in the base material composed of a material containing Cu, it is suitable for continuous use under high temperature conditions. In this case, the heat resistance fatigue strength can be maintained without causing deterioration of the joint portion.

  The electrical / electronic component according to the present invention is an electrical / electronic component having an electrode to be soldered using a solder material containing Sn and Zn, and the electrode comprises a base material made of a material containing Cu. A layer made of a material containing Ag covering the base material, and the base material made of a material containing Cu, like the junction structure, includes Cu— The formation of an intermetallic compound composed of Zn can be effectively suppressed or prevented, so that even when subjected to continuous use under high-temperature conditions, it is possible to maintain high heat fatigue strength without causing deterioration of the joint. it can.

  As described above, according to the present invention, in the method of soldering between the first member and the second member using the solder material containing Sn and Zn, the first member and the second member In at least one of the above, a part made of a material containing Cu is used as a base material, an Ag layer that covers the base material is provided, the solder material is brought into contact with the Ag layer in a molten state, or Ag is diffused into the solder, Since the first member and the second member can be soldered (or joined) by reacting and solidifying with Zn, it reacts with the Ag coating layer in which Zn in the solder material has melted, By preventing or suppressing direct contact with Cu contained in the base material, formation of an intermetallic compound composed of Cu-Zn can be effectively suppressed or prevented, and therefore, continuous use under high temperature conditions. Joining by Degradation, it is possible to eliminate the causes leading to thus decrease the thermal fatigue strength.

  Furthermore, according to the present invention, it is possible to provide a joint structure and an electrical / electronic component in which the first member and the second member are soldered using a solder material containing Sn and Zn. At least one of the first member and the second member includes a base material made of a material containing Cu and an Ag layer that covers the base material, and thus has the same effect as described above. .

  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a cross-sectional view showing a main part of a soldered electronic circuit board for explaining a soldering method, a joint structure, and an electric / electronic component according to an embodiment of the present invention.

  A processing flow of the soldering method of this embodiment will be described.

  First, the board | substrate 1 and the electronic component 5 which should be joined to this are prepared. The substrate 1 is formed with lands 2 in which a base material made of Cu is covered with a coating layer made of an Ag layer. The land 2 can be formed by, for example, the following method.

  That is, a base material made of Cu is formed integrally with a wiring pattern (not shown) by thermocompression bonding (or pasting) and etching of a copper foil on the upper surface of the substrate 1 made of glass epoxy resin or the like. The wiring pattern has a width of about 50 to 100 μm, for example. Thereafter, a resist is formed in a predetermined region on the surface of the substrate 1 so as to cover the wiring pattern. At this time, the base material is exposed without being covered with the resist. The height of the base material (that is, the height of the wiring pattern) is, for example, about 10 to 40 μm.

  The substrate 1 on which the base material is thus formed is immersed in an electrolytic solution in which Ag is dissolved, and an appropriate voltage is applied to the base material to deposit Ag on the surface of the base material. Then, an Ag layer is formed. The height of the Ag layer is, for example, about 0.01 to 5 μm. The land 2 has, for example, a rectangular outline when viewed from the upper surface of the substrate 1 and can have a horizontal width of about 0.5 to 2 mm and a vertical width of about 0.5 to 2 mm, for example. It is not limited to this, and can be any appropriate shape and size.

  In the above description, the Ag layer is formed by electroplating. However, instead of this, for example, a hot dipping method in which the substrate 1 on which the base material is formed is immersed in a molten Ag material, or The substrate 1 is immersed in a liquid material containing a metal for plating to replace the surface portion of the base material with a plating metal, or a vapor deposition method in which Ag is evaporated on the base material. You may employ | adopt the method of forming Ag layer to coat | cover.

  The electronic component 5 to be bonded to the substrate 1 is provided with leads 6. The lead 6 is coated with a base layer made of Cu with a coating layer 7 made of a single Ag layer. The lead 6 is formed by coating the Ag layer as the coating layer 7 by the same method as described above. The electronic component 5 is manufactured by using the leads 6 in advance.

  Cream solder is supplied onto the land 2 of the substrate 1 prepared as described above by, for example, screen printing or dispensing. This cream solder is constituted by dispersing metal particles (or solder powder) made of Sn—Zn-based material, for example, Sn—Zn eutectic material, in a flux. As the flux, one composed of rosin, an activator and a solvent can be used. The metal particles have an average particle diameter of, for example, about 20 to 40 μm and are present at a ratio of about 85 to 90% by weight based on the whole cream solder.

  Thereafter, the electronic component 5 is appropriately placed on the substrate 1 such that the lead 6 of the electronic component 5 comes into contact with the cream solder supplied on the land 2. Here, the cream solder contacts the Ag coating layer 7 of the lead 6 and the Ag coating layer 3 of the land 2, and does not contact the lead 6 and the base material of the land 2.

  Thus, the board | substrate 1 with which the electronic component 5 is arrange | positioned is heat-processed by passing through the heating atmosphere of about 205-230 degreeC, for example, Preferably about 210-220 degreeC. As a result, heat is supplied to the cream solder, the Sn—Zn-based material constituting the metal particles in the cream solder is melted, and components other than the metal particles such as flux are evaporated (or volatilized) and removed. .

  At this time, in the molten Sn—Zn-based material, the Ag coating layers 3 and 7 are such that Ag constituting them melts and diffuses into the molten Sn—Zn-based material, and the molten Sn—Zn-based material It reacts with Zn and is dispersed in the solder. Therefore, the amount of Zn that reacts with the base material Cu is suppressed.

  Therefore, formation of an intermetallic compound composed of Cu—Zn is prevented. The thickness of the Ag layer is preferably, for example, 0.01 μm to 5 μm. If the thickness is larger than this, Ag does not sufficiently melt and diffuse in the solder, so that the weakness of the joint interface appears in the joint characteristics. , There is almost no effect.

  Next, the heat-treated substrate 1 is cooled (or allowed to cool) to solidify the molten Sn—Zn-based material, whereby the joint portion (or soldering portion) 4 substantially made of the Sn—Zn-based material is obtained. It is formed. The joint 4 joins (or solders) the lead 6 of the electronic component 5 and the land 2 of the substrate 1 electrically and mechanically.

  As described above, an electronic circuit board having the electronic component 5 mounted on the board 1 is manufactured. Cu-Zn is used for both the bonding interface between the lead 6 of the electronic component 5 and the bonding portion 4 and the bonding interface between the land 2 and the bonding portion 4 of the substrate 1 in the obtained electronic circuit board. The formation of intermetallic compounds is prevented or suppressed.

  In this embodiment, both the base material of the land and the lead are made of Cu, and both of the base materials are covered with the Ag layer. However, the present invention is not limited to this, It is not necessary to be a simple substance of Ag, and any alloy containing Ag may be used. For example, an alloy such as Sn—Ag or Sn—Ag—Cu may be used.

  As described above, the soldering method according to the present embodiment includes the substrate 1 as the first member and the electronic component 5 as the second member using a solder material containing Sn and Zn such as a Sn—Zn-based material. A method of soldering (or joining) between the first member and the second member, comprising a base material made of a material containing Cu and an Ag layer covering the base material, Solder material is supplied (or arranged) between the first member and the second member, the solder material is brought into contact with the Ag layer in a molten state, Ag is diffused into the solder, and Zn in the solder is reacted and solidified. This is a method of soldering between the first member and the second member.

  According to the soldering method as described above, the base material made of a material containing Cu is coated on the Ag layer, the solder material containing Sn and Zn is in contact with the Ag layer, and Ag diffuses into the solder. Therefore, Zn in the solder material is prevented from coming into direct contact with Cu contained in the base material. Thereby, formation of the intermetallic compound which consists of Cu-Zn can be suppressed or prevented effectively, Therefore, deterioration of the soldering part (joining part) by continuous use under high temperature conditions, and also heat-resistant fatigue strength The cause of the decrease can be eliminated.

  Note that both the land 2 (first member) of the substrate 1 and the lead 6 (second member) of the electronic component 5 are made of a material containing Cu as in the present embodiment, and both members In the case where Cu can diffuse into the solder material (or joint), it is preferable that the material containing Cu is covered with an Ag layer so that the material containing Cu is not in direct contact with the solder material. Thus, formation of an intermetallic compound composed of Cu—Zn can be prevented. However, even in such a case, only one of them includes the Ag layer, so that it is possible to alleviate the decrease in the heat fatigue strength compared to the case where there is no Ag layer.

  Ag of the coating layer melts and diffuses into the solder during soldering, reacts with Zn in the solder, and prevents Zn from reacting with Cu as a base material. Therefore, Ag is suitable for use as a material for the coating layer.

  In the bonded structure of the embodiment in which the electronic component 5 is bonded to the substrate 1, an intermetallic compound composed of Cu—Zn is formed on the base material composed of the land 2 and the lead 6 including Cu. Therefore, even when subjected to continuous use under high temperature conditions, the joint is not deteriorated and high thermal fatigue strength can be maintained.

  In the present bonded structure, at least one of the parts to be soldered (the land 2 and the lead 6) may be formed by using at least one of the parts containing Cu as a base material and covering the base material with an Ag layer.

  When one of the first member and the second member to be joined has a portion containing Cu and the other does not have a portion containing Cu, the portion containing one Cu is Ag (as a base material). For example, when both the first member and the second member have a portion containing Cu, at least one of the portions, preferably both (as a base material) is covered with an Ag layer. .

  The substrate 1 includes, for example, those made of paper phenol material, glass epoxy material, polyimide film material, ceramic material, metal material, and the like.

  Further, as electrical / electronic parts other than the electronic parts 5, semiconductor parts (for example, so-called QFP (quad flat package) parts, CSP (chip scale package) parts, and SOP (single outside package) parts). Etc.), chip components (eg, resistors, capacitors, transistors, inductors, etc.), connectors, and the like.

  Such an electrode of an electric / electronic component is, for example, a lead, terminal, or terminal drawn out from the electronic component, and has a base material made of Cu, and the base material is covered with an Ag layer.

  However, as the first member and the second member, various members to be soldered to each other can be applied, and an electrical component or an electronic component that is soldered using a solder material containing Sn and Zn ( An electrical / electronic component having an electrode provided with a base material made of a material containing Cu and an Ag layer covering the base material is applied.

  The solder material is a metal material having a relatively low melting point, for example, a metal material that melts at a temperature of about 100 to 250 ° C., and a solder material containing Sn and Zn is such a solder material. Among them, it contains at least Sn and Zn, for example, a Sn—Zn-based material (including a Sn—Zn—B1 material in which B1 is added to a Sn—Zn eutectic material and a Sn—Zn eutectic material).

  In addition, the expression “˜system material” refers to a material that is centered on the eutectic composition of the system composed of the metal component and can further contain a trace amount of other metal components. For example, Sn—Zn-based material is Sn. It has a -9Zn eutectic composition as a center and contains a small amount of other metal components (whether added intentionally or inevitably mixed). The Sn—Zn-based material has a melting point of about 190 to 200 ° C., for example.

  As a soldering method, for example, either a reflow soldering method or a flow soldering method can be adopted. Either one side of the substrate may be soldered or both sides of the substrate may be soldered.

  In addition, the concept of preventing contact between Cu and Zn in the present invention by providing an Ag layer eliminates the harmful effects caused by the coexistence of Cu and Zn to form an intermetallic compound composed of Cu-Zn. Can be suitably used when desired.

  As described above, the soldering method, the joining structure, and the electrical / electronic component according to the present invention are the land formed on the substrate and the electrode (for example, lead) of the electrical component or the electronic component in the manufacturing process of the electronic circuit substrate. In addition, the present invention is also applicable to various joint structures to which the soldering method is applied, particularly electric / electronic parts.

Sectional drawing which shows the principal part of the soldered electronic circuit board for demonstrating the soldering method in embodiment of this invention, and a joining structure and an electrical / electronic component Sectional drawing which shows the principal part of the electronic circuit board obtained by the conventional soldering method

Explanation of symbols

1 Substrate 2 Land 3 Ag coating layer (lead side)
4 Junction 5 Electronic component 6 Lead 7 Ag coating layer (land side)

Claims (8)

  A soldering method for soldering between a first member and a second member using a solder material containing Sn and Zn, wherein at least one of the first member and the second member, A soldering method comprising forming a layer to be coated with a material containing Ag.   The soldering method according to claim 1, wherein any one of Ag, Sn-Ag, and Sn-Ag-Cu is used as the material containing Ag.   2. The soldering method according to claim 1, wherein at least one layer of the Ag-containing material is formed by any one of an electroplating method, a hot dipping method, a displacement plating method, and a vapor deposition method. .   The soldering method according to claim 1, wherein the first member is an electrode formed on a substrate, and the second member is an electrode of an electronic component.   A joint structure in which a first member and a second member are soldered using a solder material containing Sn and Zn, and at least one of the first member and the second member Comprising a base material made of a material containing Cu and a layer made of a material containing Ag covering the base material.   6. The bonded structure according to claim 5, wherein a thickness of the coating layer of the material containing Ag is set to 0.01 to 5 [mu] m.   6. The bonded structure according to claim 5, wherein the first member is an electrode formed on a substrate, and the second member is an electrode of an electronic component.   An electric / electronic component having an electrode to be soldered using a solder material containing Sn and Zn, wherein the electrode is made of a base material made of a material containing Cu and a material containing Ag covering the base material An electrical / electronic component comprising:

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