JP2005279734A - Fine joining method and complex tape for joining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fine joining method and a complex tape for joining used for this method with which in the fine joining method for joining a fine wire and a terminal by using the complex tape for joining, the sufficient continuity between the wire and the terminal can be achieved and such problem as the short-circuit between circuits, is not developed. <P>SOLUTION: This fine joining method and the complex tape for joining used for this method, are treated as the followings. The wire 6 is disposed on the terminal 1 and on this wire, the complex tape 7 for joining, having a conductible metallic base material layer (A) and a solder layer (B), is disposed so that this solder layer (B) is laid to this wire side. The complex tape for joining and the wire, are pressed with a heating head from the conductible metallic base material layer (A) side, and after deforming the cross sectional shape of this wire, the solder layer (B) is fused by supplying the electric power to join the wire and the terminal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fine bonding method applied to bonding terminals and wires, which is necessary for circuit formation in the field of micro bonding, and a composite tape for bonding suitably used in this method.

  In the field of micro joining, electric resistance welding is used for joining terminals and wires, which are necessary for circuit formation. Japanese Patent Application Laid-Open No. 11-333561 (Patent Document 1) discloses an example of electric resistance welding using a fine joining apparatus. The fine bonding apparatus includes a base, a heating head composed of two electrodes facing each other, a head driving unit, a control unit, and the like, and uses a tape-like resistance heating element that passes through the surface of the electrode to form a coil. Terminal wires are joined to terminals (input / output terminals of coil modules plated with tin, nickel, gold, etc.).

  In order to perform electric resistance welding using this fine joining apparatus, a coil end is placed on a terminal, a heating head is aligned with this position, a tape-like resistance heating element is pressed, and at the same time, an electric current is passed between the two electrodes. The pressed portion of the resistance heating element is heated. Due to this heat generation, the insulating coating on the coil terminal is removed by thermal decomposition or the like, and the tin of the solder layer is melted to form a joint between the coil core wire and the input / output terminal. After the joining is completed, the tape-like resistance heating element is wound around the reel via the foreign matter removing means.

  By doing so, foreign matters such as flux generated at the joint and removal of the insulating film are excluded from the vicinity of the electrode, and the vicinity of the electrode can always be kept clean. And it can always repeat a connection using a new part, shifting a tape-like resistance heating element little by little.

  WO02 / 45897A1 (Patent Document 2) describes a fine joining method in which a wire is joined to a terminal using the same fine joining apparatus as described above. The document discloses an example using a composite tape for bonding in which a conductive tape (conductive metal substrate layer) and a brazing material tape are integrally formed as a tape-like resistance heating element (claims). , Claim 9). By using such a composite tape for joining, joining work is easily performed, and together with the above-mentioned advantages, the heating location can be limited to a narrow range and only the brazing material in that portion can be melted. There are advantages such as no wasted consumption, no extra brazing material around the joint portion of the terminal, the finish is clean, and the quality of the joint portion is improved (page 13, lines 5-12).

However, with the recent miniaturization of electric appliances, devices with higher density are demanded, and finer circuit formation is required. In the case of such finer circuit formation, problems such as a short circuit between circuits may occur even by the above-described fine bonding method using the bonding composite tape. When the coil module is small, the above method may not achieve sufficient and stable conduction (electrical connection) of the connected coil modules. Therefore, a fine joining method using a composite tape for joining, which can achieve sufficient conduction of the coil module, and even when forming a finer circuit as required in recent years, a short circuit between the circuits. There has been a demand for the development of a fine joining method that does not cause problems such as the above, and a composite tape for joining used in the fine joining method.
JP-A-11-333561 (FIG. 2) WO02 / 45897A1 (Claims, page 13, lines 5-12)

  The present invention is a fine joining method for joining a fine wire and a terminal by using a composite tape for joining, and even when used for forming a finer circuit in recent years, a sufficient amount between the wire and the terminal is sufficient. It is an object of the present invention to provide a fine bonding method that can achieve conduction and does not cause a problem of short circuit between circuits. Another object of the present invention is to provide a composite tape for joining that is suitably used for such a fine joining method.

  As a result of intensive studies, the present inventors use a bonding composite tape having a conductive metal substrate layer and a solder layer, and the thickness of the solder layer being within a predetermined range, and a terminal to which a wire is bonded In addition, by using a material made of an elastically deformable material and pressing the wire toward the terminal side, the wire and the terminal are brought into close contact with each other while the cross-sectional shape of the wire is deformed, and then the composite tape for bonding is used. It has been found that if heating and soldering are performed, the problem of short circuit between circuits can be prevented, and sufficient conduction between the wire and the terminal can be achieved, and the present invention has been completed.

  In the present invention, as claimed in claim 1, a wire is disposed on a terminal, the conductive metal base layer (A) and the solder layer (B) are provided on the wire, and the thickness of the solder layer (B) is A bonding composite tape having a thickness of 0.1 to 2 μm is arranged so that the solder layer (B) is on the wire side, and the bonding composite tape and the wire are connected to the conductive metal base layer by a heating head. (A) Press from the side, deform the cross-sectional shape of the wire so that the diameter of the wire in the pressing direction is shortened, and then energize the heating head to melt the solder layer (B) A fine joining method is provided, wherein the wire and the terminal are joined by solder.

In the fine joining method of the present invention, first, a wire is disposed on a terminal. Here, the terminal is a portion where a wire is joined to form a circuit or the like in a coil module or the like. Therefore, it is necessary to have conductivity. In the fine joining method of the present invention, when the wire is pressed, the cross-sectional shape of the wire is deformed so that the diameter in the pressing direction is shortened, that is, flattened. If the depression is formed, the contact portion between the wire and the terminal becomes larger, which is preferable because more sufficient bonding can be achieved. Therefore, the terminal is preferably made of a material having an appropriate elastic modulus capable of giving a reaction force to the wire at the time of pressing so that a depression is easily formed and the cross-sectional shape of the wire is deformed. Is preferably 10 ⁸ to 10 ⁹ Pa. Claim 2 corresponds to this preferred embodiment, wherein the terminal has a surface conductive layer and a plastic layer having a bulk modulus of 10 ⁸ to 10 ⁹ Pa. A fine joining method is provided.

  A wire is a coil terminal or the like, which is a minute linear metal joined to a coil module or the like for forming a circuit or the like. When the wire is covered with an insulating film such as enamel, the wire including the insulating film is also called a wire.

  Examples of the metal constituting the wire include Cu and Al, but are not limited thereto, and those made of other metals are also used. Moreover, the thing which consists of 2 or more types of metals, for example, the Al wire etc. which were coat | covered with Cu, is also used.

  The diameter of the wire to be used is not particularly limited, but a wire having a diameter of 50 μm or less, preferably 35 μm or less is usually used to form a fine circuit. In the case of Cu wire, when the thickness is 30 μm or less, the effect of the present invention over the prior art, that is, the effect that sufficient conduction can be achieved and no short circuit between the circuits occurs is particularly remarkable.

  After the wire is placed on the terminal and the composite tape for joining is placed on the wire, the composite tape for joining is pressed from above by the heating head, that is, from the side opposite to the terminal or the wire side. Is done. As a result, the wire is also pressed to the terminal side, and the cross-sectional shape of the wire is deformed so that the diameter in the pressing direction is shortened, that is, flattened. As a result, the lower portion of the wire comes into contact with the terminal over a wide area, and when this contact portion is joined by solder as described later, the joining strength is improved and excellent conduction is achieved. In particular, as the cross-sectional shape of the wire is deformed, the terminal is elastically deformed, and a depression due to the wire is formed on the upper surface of the terminal, so that the contact portion between the wire and the terminal becomes larger, thereby achieving more sufficient joining. It is preferable because it is possible. Since the depression of the terminal is elastic deformation, it almost disappears when the pressure is released after bonding, but if the pressure is released after sufficient bonding has already been achieved by solidification of the solder, the bonding strength is increased. It will not be affected.

  As a magnitude | size of deformation | transformation of the cross-sectional shape of a wire, the range in which the diameter of the pressing direction after pressing becomes 0.6 to 0.8 times the diameter of the pressing direction before pressing is preferable. Claim 3 corresponds to this preferred embodiment, and is the fine joining method described above, wherein the wire has a cross-sectional shape whose diameter in the pressing direction after pressing is 0.6 to 0. 0 of the diameter in the pressing direction before pressing. The present invention provides a fine joining method characterized by being deformed to be 8 times.

  The composite tape for joining used in the fine joining method of the present invention has a conductive metal substrate layer (A) and a solder layer (B). The conductive metal substrate layer (A) is a layer that is energized by the electrode of the heating head and generates heat at the energized portion. The solder layer (B) is a layer made of a brazing material having a melting point of less than 450 ° C., and has a function of conductively joining the members by melting and solidifying by heating.

  The composite tape for bonding and the wire are pressed by the heating head to deform the cross-sectional shape of the wire into a flat shape, and then the heating head is energized to melt the solder layer (B). The heating head has a pair of electrodes arranged with a minute gap therebetween, and has a structure in which the composite tape for bonding and the wire can be pressed by the electrodes. For example, a pair of electrodes may be arranged so as to form a V shape, but in order to easily deform the cross-sectional shape of the wire, a pair of electrodes that are easy to press a wire or the like are provided. Those arranged parallel to each other are preferred.

  When the heating head is energized, the portion of the conductive metal substrate layer (A) that is in contact with the pair of electrodes of the heating head is energized and generates heat. As a result, the solder layer (B) in contact with the energized portion of the conductive metal base layer (A) is heated and melted. The energized part that is in contact with the pair of electrodes of the heating head is the part that is pressed by the heating head. Therefore, the part of the solder layer (B) that is in contact with the energized part presses the wire and It is the part which is changing the cross-sectional shape of a wire. Accordingly, the melted solder moves from the bonding composite tape to between the deformed portion of the wire and the terminal (bonded portion), and by cooling and solidifying, the wire and the terminal at the bonded portion are bonded and conducted.

  In addition, although wires, such as a coil terminal, are normally covered with insulating films, such as an enamel, the insulating film of a wire is removed by thermal decomposition, sublimation, etc. by the heating in the case of joining. Claim 4 corresponds to this preferred embodiment, and is the fine joining method, wherein the wire is composed of a linear metal of a core part (coil core wire) and an insulating film covering the metal, and the insulating film is melted. The present invention provides a fine bonding method characterized by being decomposed and removed by heating with solder.

  The composite tape for joining used in the fine joining method of the present invention is characterized in that the solder layer (B) has a thickness of 0.1 to 2 μm. When the thickness exceeds 2 μm, in the case of forming a fine circuit such as a module or a sensor portion, a problem such as a short circuit between the circuits tends to occur. On the other hand, when the thickness is less than 0.1 μm, it is difficult to obtain sufficient conduction between the wire and the terminal. Moreover, it becomes easy to produce the joining failure between a wire and a terminal.

  The solder layer (B) may be formed on the conductive metal base layer (A), or on the heat-resistant resin layer (C) as will be described later, by plating or vapor deposition. it can. In particular, formation by sputtering is preferable.

  The composite tape for joining used in the fine joining method of the present invention preferably reinforces the tape in addition to the conductive metal base layer (A) and the solder layer (B), and joins the solder at the time of joining. Therefore, a heat resistant resin layer (C) is provided between the conductive metal base layer (A) and the solder layer (B). That is, the heat-resistant resin layer (C) has a function of reinforcing the conductive metal base layer (A) as a tape and a function of transferring most of the solder from the tape to the joint at the time of joining.

  Claim 5 of the present invention corresponds to this preferred embodiment, and is the fine joining method described above, wherein the heat-resistant resin layer (C) is interposed between the conductive metal substrate layer (A) and the solder layer (B). And a fine joining method characterized by using a composite tape for joining further comprising:

  As a method of forming the heat-resistant resin layer (C) on the conductive metal substrate layer (A), a separately formed heat-resistant resin film is bonded to the film forming the conductive metal substrate layer (A). A method of applying a resin solution or enamel varnish obtained by dissolving a heat-resistant resin with an organic solvent to a film forming the conductive metal substrate layer (A), and curing or removing the solvent. Is exemplified.

  The heat-resistant resin layer (C) can be formed by using a material for a flexible print substrate in which the heat-resistant resin layer (C) and the conductive metal substrate layer (A) are integrated. In this case, a solder layer (B) is formed on the heat-resistant resin layer (C) side of the flexible print substrate material or the like.

  The heat-resistant resin constituting the heat-resistant resin layer (C) is a resin that does not decompose or hardly decompose at the temperature at which the solder layer (B) melts, and heat-resistant enamel such as polyimide, polyamideimide, polyesterimide, and polyethersulfone. Although the material used for a varnish can be used preferably, the case where a main component is a polyimide is especially suitable. Claim 6 of the present invention corresponds to this preferred embodiment, and provides a fine joining method characterized in that the material of the heat-resistant resin layer (C) is mainly composed of polyimide.

  Solder often has poor adhesion to a heat-resistant resin such as a polyimide resin. Therefore, it is preferable to have a metal film (D) that adheres to both the solder layer (B) and the heat resistant resin layer (C) between the solder layer (B) and the heat resistant resin layer (C).

  The metal film (D) may be a single layer or a plurality of layers. The metal film (D) composed of a single layer can be formed, for example, by plating or vapor-depositing a metal constituting the metal film (D) on the heat resistant resin layer (C). When the metal film (D) is formed by plating, generally used electrolytic plating, electroless plating, hot dipping, etc. can be selected. However, when the metal film (D) is formed on the heat-resistant resin layer (C) by electrolytic plating, since the deposited portion is a resin, electroless plating or metal vapor deposition is required to impart conductivity to the resin. Conductive treatment (base treatment) is performed. Moreover, when forming a metal film (D) by vapor deposition, although a normal vapor deposition method can also be used, in order to improve adhesiveness, sputtering method is preferable. Ion plating can also be used.

  In the composite tape for joining used in the fine joining method of the present invention, the metal constituting the conductive metal substrate layer (A) on the opposite side of the solder layer (B) on the conductive metal substrate layer (A). It is preferable to further have a metal layer (E) composed of a metal having a lower density than the metal and / or a metal having a melting point lower than that of the metal constituting the conductive metal substrate layer (A). Insufficient contact between the electrode of the heating head and the composite tape for bonding may cause problems such as insufficient heat generation of the conductive metal base layer (A) due to energization. By providing E) on the conductive metal base layer (A), the metal layer (E) acts as a cushion to ensure sufficient contact between the heating head electrode and the composite tape for bonding. Can be prevented. Since the metal layer (E) covers the conductive metal substrate layer (A) and blocks contact with air, the metal layer (E) further has an effect of preventing oxidation of the conductive metal substrate layer (A).

  In order to further increase the bonding strength after bonding the wire and the terminal by the fine bonding method of the present invention, the bonding portion is preferably covered with a resin such as a photocurable resin. Claim 7 of the present invention corresponds to this preferred embodiment, and provides the fine joining method described above, wherein the joining portion is covered with resin after joining the wire and the terminal. is there.

  The present invention further provides a composite tape for joining that is suitably used in the above-described fine joining method. That is, Claim 8 provides the composite tape for joining which has an electroconductive metal base material layer (A) and a solder layer (B), and the thickness of this solder layer (B) is 0.1-2 micrometers. It is.

  As described above, in order to reinforce the tape and transfer the solder to the joining portion more sufficiently at the time of joining, heat resistance is provided between the conductive metal base layer (A) and the solder layer (B). It is preferable to have a resin layer (C). Claim 9 of the present invention corresponds to this preferred embodiment, and is the above-mentioned composite tape for bonding, wherein the heat resistant resin layer (C) is interposed between the conductive metal base layer (A) and the solder layer (B). The composite tape for bonding is further provided.

  According to the fine joining method of the present invention, even when the circuit formed by the wire and the terminal is very fine, there is no problem such as a short circuit between the circuits, and the wire and the terminal are reliably joined. And sufficient conduction can be achieved.

  FIG. 1 is a conceptual cross-sectional view showing each step of the fine joining method of the present invention. Although each process of an example of the fine joining method of this invention is demonstrated using this FIG. 1, the scope of the present invention is not limited to this form.

Fig.1 (a) is a cross-sectional conceptual diagram perpendicular | vertical to the length direction of a wire which shows arrangement | positioning of the terminal of a junction part, a wire, and the composite tape for joining before the process of joining. As shown to Fig.1 (a), the wire 6 is first arrange | positioned on the terminal 1, and the composite tape 7 for joining is arrange | positioned on it. The terminal 1 includes an elastic layer 22 made of a plastic layer having a bulk modulus of 10 ⁸ to 10 ⁹ Pa and a conductive metal layer 21 thereon. The wire 6 is formed by coating a coil core wire 4 made of Cu with an insulating coating 5 made of enamel. Moreover, the composite tape 7 for joining consists of an electroconductive metal base material layer (A) and a solder layer (B), and a solder layer (B) is arrange | positioned at the wire side. The thickness of the solder layer (B) is in the range of 0.1 to 2 μm.

  Next, the bonding composite tape 7 is pressed by the heating head 8 from the conductive metal base layer (A) side. As a result, the wire 6 is also pressed toward the terminal 1 side. FIG.1 (b) is a conceptual cross-sectional view of the length direction of a wire which shows arrangement | positioning of the terminal of a junction part, a wire, the composite tape for joining, and a heating head at the time of a press. As shown in FIG.1 (b), the wire 6 is going to be pressed on the terminal 1, and the terminal 1 and the wire 6 contact | adhere by press.

  FIG.1 (c) is a cross-sectional conceptual diagram perpendicular | vertical to the length direction of a wire which shows arrangement | positioning of the terminal of a junction part, a wire, the composite tape for joining, and a heating head after a press and electricity supply. The cross section in FIG. 1C is perpendicular to the cross section in FIG. As shown in FIG. 1C, the wire 6 is deformed into a flat shape, and a depression 11 due to the wire 6 is formed in the terminal 1. Thereafter, the heating head 8 is energized, the conductive metal base layer (A) is energized and generates heat, the solder layer (B) is heated and melted, and the solder moves between the wire 6 and the depression 11. As shown in FIG. 1B, the heating head 8 has a pair of electrodes arranged in parallel at a minute interval.

  FIG.1 (d) is a conceptual cross-sectional view perpendicular to the length direction of the wire, showing the state after the solder moves between the wire 6 and the depression 11 to cool and solidify, and then the pressure is released. The insulating coating 5 of the wire 6 is thermally decomposed and removed by heating. Further, the depression 11 disappears because the pressing is released. Due to the solidified solder, a bond is formed between the coil core wire 4 of the wire 6 and the terminal 1 to achieve conduction.

  Next, the bonding composite tape used in the fine bonding method of the present invention will be described with reference to the drawings. FIG. 2 is a conceptual cross-sectional view showing an example of the composite tape for bonding. The metal constituting the conductive metal base layer (A) is selected from metals that are easy to form into a tape and have good spreadability and have a higher melting point than the solder layer (B). Those having a melting point exceeding 1000 ° C. are preferred. The optimum material is exemplified by Cu or Cu alloy, which is a material that is rich in spreadability and relatively inexpensive.

  The thickness of the conductive metal substrate layer (A) is preferably thin for the purpose of use in fine work, and is usually preferably 35 μm or less. More preferably, it is 20 μm or less, but if it is too thin, the mechanical strength as a substrate and the properties as an electric conductor are impaired.

  As described above, the thickness of the solder layer (B) is in the range of 0.1 to 2 μm, and more preferably in the range of 0.2 to 1.0 μm. Further, as the solder constituting the solder layer (B), Pb-free solder is particularly preferable from the viewpoint of environmental problems. There are various Pb-free solders based on Sn to which a small amount of Ag, Cu, Sb, In, Bi, or the like is added.

  Among the methods used for forming the solder layer (B), electrolytic plating is possible as plating, and ordinary sputtering is used as vapor deposition. When the metal layer (E) described in detail later is not formed, or when the metal layer (E) is made of a material different from the solder layer (B), the plating for forming the solder layer (B) is performed on one side. It is plating and can be performed by electrolytic plating.

  FIG. 3 is a cross-sectional view showing the configuration of the composite tape for bonding of the present invention further comprising a heat-resistant resin layer (C), a metal film (D), and a metal layer (E). As a method of forming the heat-resistant resin layer (C) on the conductive metal substrate layer (A), a resin solution is applied to the film forming the conductive metal substrate layer (A), and curing or removal of the solvent is performed. The method of performing is preferably exemplified, and a thin heat-resistant resin layer can be formed by this method.

  Application | coating of a heat resistant resin solution is preferably performed continuously. The coating amount is determined by the concentration of the resin solution. Usually, since the target thickness is several tens of μm or less, the coating thickness is within several hundreds of μm even when the solvent is included. The method of curing or removing the solvent is not particularly limited, and examples thereof include methods such as heating and baking, and removing the solvent after curing with ultraviolet rays. In general, a method of baking by heating is often used. However, when polyimide is selected as the heat-resistant resin, removal of the solvent and curing of the resin are required, and thus a high temperature of 300 ° C. or more is required.

  When the total thickness of the conductive metal base layer (A) and the heat-resistant resin layer (C) is 50 μm or less, the composite tape for bonding is flexible, has sufficient strength during handling, and an input / output terminal. In this connection, it is possible to obtain a good follow-up to the irregularities of the input / output terminals. Although depending on the material constituting these layers, it is usually sufficient in terms of mechanical strength that the total thickness of the conductive metal base layer (A) and the heat resistant resin layer (C) is 35 μm.

  As described above, the metal film (D) may be composed of a single layer or a plurality of layers. However, as a material constituting the metal film (D) composed of a single layer, the metal film (D) may be formed with the solder layer (B). Those having good adhesion are preferred, and those having good adhesion to both the heat-resistant resin layer (C) and the solder layer (B) are particularly preferred, and examples thereof include Cu or Cu alloy, Fe or Fe alloy. Among these, monel alloy (Cu—Ni) and Cu alone are preferable.

  When the metal film (D) is composed of a plurality of layers, the layer in contact with the solder layer (B) is made of a metal having good adhesiveness to the solder, and the layer in contact with the heat resistant resin layer (C) is bonded to the heat resistant resin. It is preferable that it consists of a good metal. As a method of forming a metal film (D) composed of a plurality of layers, first, a heat-resistant resin and a metal layer having good adhesiveness are formed on the surface of the heat-resistant resin layer (B), and solder and good adhesiveness are formed thereon. A method of forming a metal layer by selecting a metal and depositing it by plating or vapor deposition is preferably exemplified.

  The material constituting the heat-resistant resin and the metal layer having good adhesion can be variously selected from the heat-resistant resin layer (B) and the metal having good adhesion and strong anchor effect. As for the thickness of the metal film (D), about 0.1 μm is sufficient when it is a single layer, and about 0.1 μm is sufficient for each layer even when the metal film (D) is composed of a plurality of layers. It is.

  Among the metals constituting the metal layer (E), examples of the metal having a lower density than the metal constituting the conductive metal substrate layer (A) include foam metal. Moreover, as a metal whose melting | fusing point is lower than the metal which comprises an electroconductive metal base material layer (A), solder with melting | fusing point less than 450 degreeC is illustrated. Among the solders, Pb-free solders as exemplified above are particularly preferable from the viewpoint of environmental problems. In particular, Pb-free solder having a melting point of less than 350 ° C. is preferable.

  The preferred range of the thickness of the metal layer (E) varies depending on the shape of the electrode, the state of the joined portion, and the intended use of the composite tape for joining, but usually a thickness of 2 μm or less is preferred, particularly preferably 0.2. The thickness is about 1.0 μm.

  The metal layer (E) is usually formed by plating the metal constituting the metal layer (E) on the opposite side of the solder layer (B) on the conductive metal substrate layer (A). As the plating used, hot dipping, electrolytic plating and the like are possible. Usually, electrolytic plating is preferably used. In particular, when the same metal as the material constituting the solder layer (B) is used as the metal constituting the metal layer (E), both can be plated at the same time, that is, both sides can be plated. It is advantageous and the manufacturing cost can be reduced.

  The total thickness of all the layers of the composite tape for bonding of the present invention is preferably 80 μm or less, more preferably 35 μm or less.

  The conductive metal film used for forming the conductive metal substrate layer (A) in the above production method, for example, a Cu film having a commercially available width of several tens of centimeters and a length of several tens to several hundreds of meters. Can be used. The film having the conductive metal substrate layer (A), the solder layer (B) and the like thus completed is cut into a required width to obtain a composite tape for bonding.

  In order to carry out the fine joining method of the present invention, an apparatus as described in FIGS. 1 and 2 of Patent Document 1 is preferably used. By using this apparatus, foreign matter such as flux generated at the joint portion and removal of debris from the insulating coating are excluded from the vicinity of the electrode, and the vicinity of the electrode can always be kept clean. And it can always repeat a connection using a new part, shifting a tape-like resistance heating element little by little.

  Further, as described above, it is preferable to cover the bonding portion with a resin after the wire and the terminal are bonded. As the resin, a photo-curable resin, particularly an ultraviolet curable adhesive is preferably used.

  Next, the present invention will be described more specifically with reference to examples. However, the examples do not limit the scope of the present invention.

Example 1
A polyimide varnish was applied and baked onto a commercially available electrolytic Cu foil (length 200 m, width 60 cm, thickness 18 μm, conductive metal substrate layer (A)). The polyimide resin layer (C) after baking was 13 μm. A Cu alloy was deposited on the polyimide resin layer (C) side of the composite film, and a Cu metal film (D) having a thickness of 0.1 μm was adhered. Thereafter, a solder layer (B) was formed on the Cu metal film (D) side by electroplating with a composition of Sn (97%) and Cu (3%) as Pb-free solder. The thickness of the solder layer (B) after plating was 0.5 μm. The completed composite foil was cut to a width of 0.5 mm to obtain a composite tape for bonding having a total thickness of about 32 μm.

Using the fine joining apparatus shown in FIG. 4, the obtained composite tape for joining was loaded on the reel 12 on the supply side of the fine joining apparatus. A model device 9 shown in FIG. 5 was placed on the base of the fine joining apparatus. On the model device 9, two terminals 10 having a terminal width of 400 and a terminal pitch of 400 μm are formed 50 μm apart from each other. A wire 6 (coil end) of 25 μm diameter Cu wire is placed on one side of the terminal 10, and the composite tape 7 for bonding is pressed from above with a heating head 8 with a weight of 7700 g weight, and at the same time the energization time under the condition of power 50 W Energized with pressure for 30 ms. The terminal 10 has a thickness 35 [mu] m, consists of tin plating thickness 0.1μm was formed on the flexible printed circuit board of the bulk modulus 10 ^9.

  As a result of microscopic observation of the bondability between the terminal 10 and the coil core wire 4 after energization, the contact portion between the coil core wire and the terminal and the periphery thereof are covered with a continuous Pb-free solder layer. The portion covered with the solder is only inside the terminal and does not spread outside the terminal. Therefore, there is no contact between the adjacent terminal and the Pb-free solder layer, and it has been shown that the short circuit problem does not occur. In addition, continuity between the terminal and the wire was examined by energizing between the terminal and the coil, and it was found that good continuity was achieved.

Examples 2-5, comparative example Except having changed the thickness of solder layer (B) into the thickness shown in Table 1, it carried out similarly to Example 1, formed the composite tape for joining, and formed the composite tape for joining formed. The terminal and the coil core wire were joined to each other, the joining property was observed with a microscope, and the conduction state was examined in the same manner as in Example 1. The results are shown in Table 1.

  In Table 1, for “terminal solder overhang”, for all samples, the case where the portion covered with Pb-free solder is only inside the terminal is ○, and for some samples, the outside of the terminal is less than 30 μm from the end of the terminal. The case of spreading to △, and the case of almost all the samples extending to the outside of the end of the terminal are marked with ×. The greater the outward spread (protrusion), the greater the possibility that adjacent terminals and the Pb-free solder layer will come into contact with each other and cause a short circuit problem. As for the bonding state, ◯ indicates that the bonding is sufficient and conduction is good for all the samples, and △ indicates that the conduction is poor for some samples.

  The results in Table 1 show that if the thickness of the solder layer is within the scope of the present invention, there will be no or less protrusion than the terminal of the solder transferred to the terminal, while sufficient conduction will be achieved. ing.

It is a cross-sectional conceptual diagram which shows the process of an example of the fine joining method of this invention. It is sectional drawing which shows an example of the composite tape for joining of this invention. It is sectional drawing which shows the other example of the composite tape for joining of this invention. It is the schematic which shows the fine joining apparatus used in the Example. It is a top view which shows the outline of the model device used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10 Terminal 11 Depression 12 Reel 21 Conductive metal layer 22 Elastic layer 4 Coil core wire 5 Insulation coating 6 Wire 7 Joining composite tape 8 Heating head 9 Model device (A) Conductive metal base material layer (B) Solder layer ( C) Heat resistant resin layer (D) Metal film (E) Metal layer

Claims (9)

  A wire is arranged on the terminal, and has a conductive metal base layer (A) and a solder layer (B) on the wire, and the thickness of the solder layer (B) is 0.1 to 2 μm. A composite tape is disposed so that the solder layer (B) is on the wire side, and the composite tape for bonding and the wire are pressed from the conductive metal substrate layer (A) side by a heating head, After deforming the cross-sectional shape of the wire so that the diameter in the pressing direction of the wire is shortened, the soldering layer (B) is melted by energizing the heating head, and the wire and the terminal are melted by the molten solder. A fine joining method characterized by joining. 2. The fine joining method according to claim 1, wherein the terminal has a surface conductive layer and a plastic layer having a bulk modulus of 10 ⁸ to 10 ⁹ Pa. 3.   The cross-sectional shape of the wire is deformed so that the diameter in the pressing direction after pressing is 0.6 to 0.8 times the diameter in the pressing direction before pressing. The fine joining method described in 1.   4. The wire according to claim 1, wherein the wire comprises a linear metal in the core and an insulating film covering the metal, and the insulating film is decomposed and removed by heating with molten solder. The fine joining method according to any one of the above.   The bonding composite tape further comprises a heat resistant resin layer (C) between the conductive metal base layer (A) and the solder layer (B). The method of fine joining as described in the above.   6. The fine joining method according to claim 5, wherein the material of the heat resistant resin layer (C) is mainly composed of polyimide.   The fine joining method according to any one of claims 1 to 6, wherein the joining portion is covered with a resin after joining the wire and the terminal.   The composite tape for joining which has an electroconductive metal base material layer (A) and a solder layer (B), and the thickness of this solder layer (B) is 0.1-2 micrometers. The composite tape for bonding according to claim 8, further comprising a heat-resistant resin layer (C) between the conductive metal substrate layer (A) and the solder layer (B).

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