JP4849253B2 - Joining method - Google Patents

Description

  The present invention relates to a joining method for joining joined members by heating and firing in a state where metal nanoparticles are held at predetermined positions between the joined members.

Conventionally, various methods such as soldering, bonding, and welding have been used as methods for joining members together. On the other hand, in consideration of the fact that in recent years, further consideration for environmental pollution has been demanded and depending on the nature of the members to be joined, these conventional joining methods may be inappropriate. Different bonding techniques using metal nanoparticles have been used.
By the way, the joining technique using metal nanoparticles involves applying a paste-like joining material containing metal nanoparticles coated with an organic protective film and a binder to a predetermined position of the members to be joined. In this state, the members to be bonded and the bonding material are heated and pressed to fire the bonding members, thereby bonding the members to be bonded to each other (see, for example, Patent Document 1). According to such a joining method, a strength of 48 to 85 MPa is obtained with a joining strength value obtained by a tensile shear test (test equipment: autograph made by Shimadzu, maximum thrust 10 kN, test speed: 6.0 m / min).

JP 2004-130371 A

  In the joining method using the metal nanoparticles, after the joining material is applied to a predetermined position of the member to be joined, the joining material is dried, and then the work to stack the members to be joined is performed. However, in the case of conventional rosin substitute binder (flux for solder), the bonding material is likely to be peeled off from the bonded member when the bonding material is dried and the bonded member is assembled. (Peeling resistance is about pencil hardness 6B). If the joining member is peeled off from the joined member, the joining strength between the joined members is greatly reduced. Therefore, in order to prevent the joining material from being peeled off, the assembly work of the joined member is carefully performed. Had to be done. In addition, when peeling occurs in the bonding material, it is necessary to clean the member to be bonded and then restart the bonding process, which may reduce work efficiency.

Therefore, it is also conceivable to use a strong material that is resistant to peeling as the binder contained in the bonding material. However, it is difficult to obtain the necessary bonding strength with a binder having strong properties that can be used at the present time. For example, when a resin binder (epoxy, acrylic, ester, etc.) is used, the peeling resistance of the bonding material is 2H to 6B in pencil hardness, but the bonding strength is 4 to 8.2 MPa. End up. When a rosin binder (rosin + solvent + activator) is used, the peeling resistance of the bonding material is 2B to 6B in pencil hardness, but the bonding strength is 5 to 15 MPa. Furthermore, even when a mixture of a conventional rosin substitute binder and an epoxy binder is used, the peeling resistance of the bonding material is a pencil hardness of 6B, and the bonding strength is 24 to 34 MPa.
The present invention has been made in view of the above problems, and the purpose of the present invention is to join at the time of joining work without reducing the joining strength of the joining material when using joining technology using metal nanoparticles. The problem is to solve the problem of material peeling.

In order to solve the above-described problems, the bonding method of the present invention is a method in which a bonding material containing metal nanoparticles is heated and fired while being held in a predetermined position between two bonded members. When the members are joined together, the surface of the joining material is covered with a surface coating material, thereby ensuring the surface strength of the joining material that does not cause peeling during the joining operation.

(Aspect of the Invention)
The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each item does not limit the technical scope of the present invention. Therefore, the technical aspects of the present invention also apply to those in which some of the constituent elements in each section are replaced, deleted, or other constituent elements are added while referring to the best mode for carrying out the invention. It can be included in the range.

(1) A joining method for joining joined members by heating and firing a joining material containing metal nanoparticles in a state of being held at a predetermined position between two joined members, Of the two members to be joined, the joining material is applied only to the necessary range of one joining surface, and the surface of the joining material is secured to ensure surface strength that does not cause peeling during joining operations. Then, after applying a surface coating material made of a material capable of ensuring the necessary hardness depending on its own strength, at least in a range where the bonding material is applied, the two members to be bonded are overlapped, and the bonding is performed. A joining method in which the members to be joined are pressurized while being heated so that the material has a temperature equal to or higher than the joining temperature (Claim 1).
In the joining method described in this section, the joining material is applied only to the necessary range of one joining surface of the two members to be joined, and the surface of the joining material does not peel off during the joining operation. By applying a surface coating material made of a material capable of ensuring the necessary hardness according to its own strength to ensure surface strength, the surface of the bonding material is applied at least in a range where the bonding material is applied. Cover with a surface coating material. Then, the strength of the surface coating material itself ensures that the bonding material has a surface strength that does not cause peeling during the bonding operation. Thereafter, the two members to be joined are overlapped with each other, and the members to be joined are joined to each other by pressurizing the members to be joined while heating so that the joining material becomes equal to or higher than the joining temperature.

(2) In the item (1), after the bonding material is applied only to a necessary range of one bonding surface, the bonding material is dried, and the surface of the bonding material is peeled off during the bonding operation. A surface coating material made of a material capable of ensuring the necessary hardness according to its own strength for ensuring the surface strength that does not occur is applied at least in a range where the bonding material is applied, and then applied to the surface. And a step of drying the coating material.
In the bonding method described in this section, the solvent is evaporated from the bonding material by applying the bonding material only to a necessary range of one bonding surface and then drying the bonding material. In addition, at least a surface coating material made of a material that can secure the necessary hardness by its own strength to secure the surface strength so that peeling does not occur during the joining operation on the surface of the joining material. After the material is applied over the coated area, the surface coating material is dried to dry the solvent contained in the surface coating material. Therefore, the problem that the solvent is gasified between the members to be bonded during the heating / pressurizing process and the bonding material is blown away from between the members to be bonded by the pressure does not occur.

(3) The hardness necessary for the surface of the bonding material according to (1) or (2) above to ensure the surface strength that does not cause peeling during the bonding operation. In the step of applying the surface coating material made of a material that can be secured, the surface coating material is applied more widely than the range in which the bonding material is applied.
In the bonding method described in this section, by applying the surface coating material wider than the range in which the bonding material is applied, the peripheral edge of the bonding member that is relatively easily peeled is reliably covered with the surface coating material. This improves the strength against peeling. In addition, high accuracy is not required for the application range of the surface coating material.

(4) An activity that cleans the surface of the other member to be bonded to the surface coating material and activates the surface coating material to improve the bondability between the member to be bonded and the other bonding material. A joining method to which an agent is added (Claim 2).
In the joining method described in this section, two members to be joined are overlapped with each other, and when the members to be joined are pressed while being heated so that the joining material is equal to or higher than the joining temperature, they adhere to the surface coating material. The surface of the other member to be bonded can be cleaned with an activator added to the surface coating material, and the bondability between the member to be bonded and the other bonding material can be improved.
Examples of the activator include carboxylic acid, adipic acid, amine and the like. Further, when a rosin flux is used for the surface coating material, the flux itself has an active action.

  Since the present invention is configured as described above, it is possible to solve the problem of peeling of the bonding material at the time of bonding work without reducing the bonding strength of the bonding material when using the bonding technique using metal nanoparticles. Become.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the part which is the same as that of a prior art, or an equivalent part, and detailed description is abbreviate | omitted.
FIG. 1 schematically shows a joining procedure for joining members to be joined together using metal nanoparticles according to an embodiment of the present invention. Each process is as follows.
(I) Bonding material application step: The bonding material 12 is applied to the bonding surface of the member to be bonded 10 (10A). The bonding material 12 is a mixture of metal nanoparticles coated with an organic protective film, a binder, and a solvent. In the illustrated example, the member to be joined 10 is a copper plate. The metal nanoparticles are optimally silver nanoparticles, but metal nanoparticles made of, for example, gold, palladium, copper, or other metals can also be used. In the illustrated example, a resin flux for solder is used for the binder, and alcohol is used for the solvent.
(Ii) Bonding material drying step: The bonding material 12 applied to the bonding surface of the member to be bonded 10 in the applying step (i) is dried, and the solvent contained in the bonding material 12 is evaporated.
(Iii) Surface coating material application step: From a material that can secure the necessary hardness by its own strength to ensure the surface strength of the bonding material 12 so as not to peel off during the bonding operation. The surface coating material 14 to be formed is stacked and applied so as to have a constant thickness. At this time, as shown in an enlarged view in FIG. 2, the surface coating material 14 is applied wider than the area where the bonding material 12 is applied, and the periphery of the bonding material 12 is completely covered with the surface coating material 14. It is desirable.
Note that a resin-based coating material (epoxy-based, enamel-based, acrylic-based, hydrocarbon-based) is used for the surface coating material 14. Further, if necessary, the surface coating material 14 is cleaned with the surface of the other bonded member 10B in close contact with the surface coating material 14 so that the bonding property between the bonded member 10A and the other bonding material 10B is improved. An activator is added that activates to improve. Examples of the activator include rosin flux, carboxylic acid, adipic acid, amine, and the like.
(Iv) Surface coating material drying step: The surface coating material 14 applied to the bonding material 12 in the coating step (iii) is dried, and the solvent contained in the surface coating material 14 is evaporated. The surface coating material 14 is in a liquid state, and the application work can be performed by spraying.

(V) Assembly process: The member to be bonded 10 (10B) on which the bonding material 12 is applied is overlapped with the member to be bonded 10 (10B), and the two bonding members 10 (10A, 10B) 12 is pinched.
(Vi) Heating / pressurizing step: The two members to be bonded 10 (10A, 10B) are pressurized while being heated so that the bonding material 12 has a temperature equal to or higher than the bonding temperature. A press die can be used for the heating and pressing operation.
(Vii) Joining step (joining completion step): Applying pressure to obtain the required joining strength to the member to be joined 10 (10A, 10B) in a state where the joining material 12 is maintained at the joining temperature or higher. Thus, the members 10 (10A, 10B) to be joined are joined together.

According to the embodiment of the present invention configured as described above, the following operational effects can be obtained.
First, in the embodiment of the present invention, (i) in the bonding material application step, the bonding material 12 is applied only to the necessary range of the bonding surface of one of the two members 10 (10A, 10B). . (Iii) In the surface coating material application step, the surface coating material 14 made of a material capable of ensuring the necessary hardness on the surface of the bonding material 12 is applied so as to overlap at least the range where the bonding material 12 is applied. The surface of the bonding material 12 can be covered with the surface coating material 14. The surface strength of the bonding material 12 can be ensured by the strength of the surface coating material 14 itself so as not to peel off during the bonding operation.

Therefore, in the assembling step (v), when the joining material 12 and the member to be joined 10 are assembled, the joining member 12 is prevented from being peeled off without being handled with care as in the conventional case. can do. Further, since it is more reliably avoided that the joining member 12 is peeled off, unnecessary work such as cleaning the member to be joined when the joining member 12 is peeled off and starting the post-joining process from the beginning is avoided. Therefore, it becomes possible to prevent a decrease in work efficiency. Then, the two members to be bonded 10 (10A, 10B) are overlapped, and (vi) in the heating / pressurizing step, the members to be bonded are added while heating so that the bonding material 12 becomes equal to or higher than the bonding temperature. By pressing, it becomes possible to firmly join the members to be joined 10 (10A, 10B) to each other by the joining material 12 in which a necessary amount is applied in a necessary range.
In the surface coating material application step (iii), by applying the surface coating material 14 wider than the range in which the bonding material 12 is applied, the peripheral portion of the bonding member 12 that is relatively easily peeled off is covered with the surface coating material 14. It is possible to reliably cover and improve the strength against peeling of the bonding material 12.

Further, (iii) in the surface coating material application step, if an activator is added to the surface coating material 14, (v) the two members to be joined 10 (10A, 10B) in the assembly step (Vi) In the heating and pressurizing step, the surface coating material 14 is applied when the members to be bonded 10 (10A, 10B) are pressed while being heated so that the bonding material 12 has a temperature equal to or higher than the bonding temperature. The surface of the other member to be bonded 10 (10B) that is in close contact with the surface is cleaned with an activator added to the surface coating material 14, thereby improving the bondability between the bonding material 12 and the member to be bonded 10 (10B). Can do.

FIG. 3 shows the relationship between the coating amount Q (μg / mm ² ) of the surface coating material 14 and the bonding strength I (MPa). In the figure, each point indicated by INV represents the implementation of the present invention. It is a value according to the form. For comparison, the value when the surface coating material 14 is not applied to the bonding material 12 is PA1, and the value when the rosin paste is mixed and used for the bonding material 12 is PA2. Further, L1 is the minimum amount of the surface coating material 14 that does not peel even if the peeling test of the bonding material 12 shown in FIG. 4 is repeated 10 times, and L2 is the member 10 (10A, 10B) ) Target joint strength.
Note that the peeling test of the bonding material 12 shown in FIG. 4 is performed by applying the bonding material 12 (5 × 5 mm square) to the test piece 10 (10C) of the member to be bonded, and further according to the embodiment of the present invention. Further, the surface coating material 14 is further applied to the test piece, placed on the member 10 (10A), and a weight 16 (300 g) is placed on the test piece 10 (10C) to apply a load. The method of sliding 10 mm parallel to the member 10 (10A) to be joined is adopted.

As is apparent from FIG. 3, the value INV according to the embodiment of the present invention can obtain a sufficient bonding strength I while ensuring the peeling resistance. Moreover, it is not necessary that the coating amount of the surface coating material 14 is large. By making the coating amount of the surface coating material 14 around 0.5 μg / mm ² (about 1 to ² μm in thickness), the bonding strength I can be increased. It will be understood that it is the highest.
When a resin-based coating material (epoxy-based, enamel-based, acrylic-based, hydrocarbon-based) is used for the surface coating material 14, the surface coating material 14 has a peeling resistance of about 2H to 6H pencil hardness, The strength I is about 32 to 42 MPa. On the other hand, when a rosin flux is used for the surface coating material 14, the peeling resistance of the surface coating material 14 is about 2H pencil hardness, and the bonding strength I is about 55.2-76.2 MPa.

On the other hand, the value PA1 when the surface coating material 14 is not applied to the bonding material 12 is much higher than the target bonding strength value of the bonding strength I, but the necessary peeling resistance cannot be ensured. In addition, the case where the rosin paste is mixed with the bonding material 12 is used in a case where the surface coating material 14 is mixed with the bonding material 12 and used. Therefore, although the value PA2 uses the surface coating material 14 in an amount of use (application amount) that is insignificantly larger than the value INV according to the embodiment of the present invention, the bonding strength I slightly exceeds the target bonding strength. Stay around.
As described above, according to the embodiment of the present invention, it is possible to solve the problem of peeling of the bonding material during the bonding operation without reducing the amount of the surface coating material used and reducing the bonding strength of the bonding material. It will be understood that this is possible.

It is a schematic diagram which shows the procedure which joins to-be-joined members using metal nanoparticle based on embodiment of this invention. It is an enlarged view of the surface coating material application | coating process of FIG. It is a figure which shows the relationship between the application quantity of a surface coating material, and the joint strength of to-be-convenient members. It is explanatory drawing of the peeling test method of a joining material.

  10, 10A, 10B: To-be-joined member, 12: Joining material, 14: Surface coating material

Claims (2)

It is a joining method for joining members to be joined by heating and firing in a state where a joining material containing metal nanoparticles is held at a predetermined position between two members to be joined,
To apply the bonding material only to the necessary range of one of the two members to be bonded, and to ensure the surface strength of the bonding material so that no peeling occurs during the bonding operation. The surface coating material made of a material capable of ensuring the necessary hardness depending on its own strength is applied to overlap at least the range where the bonding material is applied, and then the two members to be bonded are overlapped, A joining method, wherein the members to be joined are pressurized while being heated so that the joining material has a temperature equal to or higher than the joining temperature. An activator is added to the surface coating material, which is activated to clean the surface of the other bonded member that is in close contact with the surface coating material and to improve the bondability between the bonded member and the other bonding material. The bonding method according to claim 1, wherein the bonding method is used.

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