CN110640292A - Method for making electrodes using ultrasonic welding process - Google Patents

Abstract

The present application provides a method for making electrodes by using an ultrasonic welding process, comprising the following steps: providing molten solder between a first surface of a substrate and a first welding head; At least one applies ultrasonic waves to the molten solder, which after cooling adheres to the first surface of the substrate as a first electrode. In the method provided by the present application, by applying ultrasonic waves on the solder, the surface tension of the solder can be reduced and the wettability of the solder on the surface of the base material can be enhanced without flux, so as to improve the adhesion.

Description

Method for making electrodes using ultrasonic welding process

technical field

The present application generally relates to a method for fabricating electrodes using an ultrasonic welding process, and more particularly, to a method for fabricating electrodes on metal oxide varistors.

Background technique

Varistor is a common electronic device whose resistance value changes with voltage within a certain current and voltage range. Varistors are usually made of semiconductor materials. Materials commonly used today for varistors include, for example, metal oxide varistors (MOVs). For example, "zinc oxide" (ZnO)" varistors are now widely used.

A varistor is a voltage-limiting protection device. When an overvoltage occurs between the two electrodes of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value due to the nonlinear characteristics of the varistor, thereby realizing the protection of the subsequent circuit.

SUMMARY OF THE INVENTION

At least one object of the present application is to provide a method for fabricating electrodes using an ultrasonic welding process, which can fabricate electrodes on a metal oxide varistor substrate without the need for flux.

According to an embodiment of the present application, there is provided a method for making electrodes by using an ultrasonic welding process, comprising the following steps:

providing molten solder between the first surface of the substrate and the first solder tip;

ultrasonic waves are applied to the molten solder through at least one of the substrate and the first solder tip,

The molten solder is attached to the first surface of the substrate as a first electrode after cooling.

In at least one embodiment, the step of providing molten solder between the first surface of the substrate and the first solder tip includes heating at least one of the substrate and the first solder tip to cause Solder melted.

In at least one embodiment, the step of providing molten solder between the first surface of the substrate and the first solder tip comprises:

The substrate and the first solder tip are immersed in molten solder to provide molten solder between the first surface of the substrate and the first solder tip.

In at least one embodiment, a wire is placed in the molten solder,

After the molten solder is cooled, the metal wire as a first lead is fixed on the first surface of the substrate by solder, and is electrically connected to the substrate through the solder.

In at least one embodiment, the substrate further has a second surface opposite the first surface,

Wherein, the method also includes the following steps:

providing molten solder between the second surface of the substrate and the second solder tip;

ultrasonic waves are applied to the molten solder through at least one of the substrate and the second solder tip,

The molten solder is attached to the second surface of the substrate as a second electrode after cooling.

In at least one embodiment, the step of providing molten solder between the second surface of the substrate and the second solder tip comprises:

At least one of the substrate and the second solder tip is heated to melt the solder.

In at least one embodiment, the step of providing the molten solder between the second surface of the substrate and the second solder tip comprises:

The substrate and the second solder tip are immersed in molten solder to provide molten solder between the second surface of the substrate and the second solder tip.

In at least one embodiment, further comprising the step of: placing a wire in the molten solder,

After the molten solder is cooled, the metal wire as a second lead is fixed on the second surface of the base by the solder, and is electrically connected to the base through the solder

In at least one embodiment, the first welding head and the second welding head are different welding heads, and the process of using the first welding head to form the first electrode on the first surface is the same as using the first welding head. The process of forming the second electrode on the second surface by the second welding head is performed simultaneously.

In at least one embodiment, the first surface has a metallization layer thereon, and the first electrode is attached to the metallization layer of the first surface.

In at least one embodiment, the second surface has a metallization layer thereon, and the second electrode is attached to the metallization layer of the second surface.

In at least one embodiment, the material of the metallization layer is selected from one of the group consisting of the following materials and their alloys: gold, silver, copper, aluminum, zinc.

In at least one embodiment, the substrate is a metal oxide varistor.

In at least one embodiment, the material comprising the solder is one selected from the group consisting of gold, silver, copper, tin, aluminum, zinc, and alloys thereof.

In at least one embodiment, the substrate is immersed in molten solder under the grip of a jig.

In at least one embodiment, an ultrasonic source applies ultrasonic waves to the substrate through the fixture.

In at least one embodiment, further comprising the step of moving the first solder tip along the first surface to distribute the molten solder on the first surface.

In at least one embodiment, further comprising the step of moving the second solder tip along the second surface to distribute the molten solder on the second surface.

In the method for making electrodes by using the ultrasonic welding process provided by the present application, by applying ultrasonic waves on the solder, the surface tension of the solder can be reduced and the wettability of the solder on the surface of the base material can be reduced without flux, so that the solder can be It is evenly distributed on the surface of the base material and improves the welding strength. In addition, the method provided by the present application can be implemented in a low-cost manner, has high efficiency, is easy to implement, and is suitable for automated production.

Description of drawings

The above-mentioned characteristics, technical features, advantages and implementation manners of the present application will be further described below in a clear and easy-to-understand manner through the description of the preferred embodiments and in conjunction with the accompanying drawings. The following drawings are only intended to illustrate and explain the present application schematically, and do not limit the scope of the present application. in:

1a-1d illustrate steps of an exemplary method according to Embodiment 1 of the present application;

2a-2b illustrate steps of an exemplary method according to Embodiment 2 of the present application;

3a-3d illustrate steps of an exemplary method according to Embodiment 3 of the present application;

4a-4d illustrate steps of an exemplary method according to Embodiment 4 of the present application;

5a-5b illustrate steps of an exemplary method according to Embodiment 5 of the present application;

6a-6b illustrate steps of an exemplary method according to Embodiment 6 of the present application;

7a-7b illustrate steps of an exemplary method according to Embodiment 7 of the present application.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present application, the specific embodiments of the present application will now be described with reference to the accompanying drawings.

A varistor generally includes a wafer-like base material, upper and lower electrodes on the upper and lower surfaces, respectively, and leads welded to the upper and lower electrodes, respectively. The leads are usually soldered to the electrodes by soldering or the like.

In existing soldering methods, flux is usually used. Flux can be used to reduce the surface tension of the solder and enhance the wettability of the solder, so that the solder can be evenly distributed on the surface of the base material and can improve the solder strength. However, residual flux can have many adverse effects on solder joints. Therefore, it is necessary to carry out the step of cleaning the flux after the soldering is completed. But the flux is usually an organic substance that is harmful to the environment, such as trichloroethylene, etc., so it can cause serious pollution.

At least one object of the present application is to provide a method of making electrodes using an ultrasonic welding process, which can make electrodes on a metal oxide varistor substrate (with or without a metallization layer) without the need for flux.

Another object of the present application is to provide a method for making electrodes by using an ultrasonic welding process, which can directly make electrodes composed of solder (such as tin) on a bare metal oxide varistor (without a metallization layer), There is no need to pre-deposit a metallization layer on the die of the metal oxide varistor.

According to the first embodiment of the present application, a method for fabricating electrodes using an ultrasonic welding process is provided, as shown in FIGS. 1 a to 1 d , including the following steps:

a) As shown in Figure 1a, a solid tin solder 30 is attached to the already heated solder tip 21, which is also connected to an ultrasonic source (not shown in the figure);

b) As shown in FIG. 1b, the solder tip 21 is brought into contact with the first surface 11 of the substrate 10 of the metal oxide sub-varistor (for example, made of zinc oxide material), so that the molten tin solder 31 on the solder tip 21 is applied to the On the first surface 11 , ultrasonic waves are introduced from the ultrasonic source into the molten tin solder 31 through the welding head 21 , so that at least a part of the area of the molten tin and solder 31 (especially the area between the welding head 21 and the first surface 11 is introduced into the molten tin and solder 31 ). ) to apply ultrasonic waves. Under the action of ultrasonic waves, the surface tension of the molten tin solder 31 is reduced, and its wettability with the first surface 11 is enhanced, so that the molten tin solder 31 especially in the area between the solder tip 21 and the first surface 11 is enhanced. is attached to the first surface 11 with enhanced wettability;

c) As shown in Fig. 1c, the soldering tip 21 is moved along the first surface 11 (as shown by the dashed arrow in Fig. 1c), so that the molten tin solder 31 is attached and distributed on the first surface with enhanced wettability on a larger area of surface 11;

d) As shown in FIG. 1 d , remove the solder tip 21 from the substrate 10 , and cool the substrate 10 and the molten tin solder 31 thereon, and the molten tin solder 31 is cooled and attached to the first surface 11 to form the first surface of the substrate 10 . An electrode 41 .

The substrate 10 also has a second surface 12 opposite the first surface 11 . A second electrode may be formed on the second surface using a method comprising steps a)-d) above.

After the electrodes are formed, processes such as dip soldering, hot air soldering, selective wave soldering, etc. can be used to realize the soldering of the electrodes 41 and the leads.

In the method provided by the above embodiment, the surface tension of the solder is reduced and the wettability of the solder on the surface of the base material is enhanced by applying ultrasonic waves to the solder without flux. Therefore, in this way, it is possible to have high solder strength even without flux. In addition, ultrasonic waves can remove the oxide layer on the surface of the base material, thereby further enhancing the wettability of the solder on the surface of the base material. Due to the enhanced wettability of the solder on the surface of the base material, the solder can be uniformly distributed in a larger area (much larger than the area of the traditional soldered solder joint). Therefore, it can be directly applied to the metal oxide varistor Solder is used as electrodes on the die without pre-depositing a metallization layer on the metal oxide varistor die.

It should be noted that, in the method provided according to the present application, ultrasonic waves are introduced and applied to the solder through the solder tip. However, in other embodiments, ultrasonic waves may also be introduced through the substrate and applied to the solder, ie the substrate is connected to the ultrasonic source.

Figures 2a-2b illustrate steps of an exemplary method according to Embodiment 2 of the present application. The steps of the method in the second embodiment are basically the same as those in the first embodiment, and the difference is only in the manner of providing the molten solder. In the method provided in the first embodiment, the solid solder 30 is first attached to the heated solder head 21 and then supplied to the first surface 11 . In the method provided in the second embodiment, as shown in FIG. 2 a , the solid solder 30 is first provided to the substrate 10 , and the solid solder 30 is melted by heating the substrate 10 . Then, as shown in FIG. 2b , ultrasonic waves are introduced into the molten tin solder 31 using the solder tip 21 .

3a-3d illustrate steps of an exemplary method according to Embodiment 3 of the present application. The steps of the method in the third embodiment are basically the same as those in the first embodiment, the only difference is that the two welding heads (the first welding head 21 and the second welding head 22 ) Electrodes are formed on the first surface 11 and the second surface 12), respectively. The exemplary method according to the third embodiment of the present application includes the following steps:

a) As shown in Fig. 3a, the solid tin solder 30 is attached to the heated first welding head 21 and the second welding head 22, respectively, which are also connected to the ultrasonic source (not shown in the figure);

b) As shown in FIG. 3b, the solid tin solder 30 is melted by the heated first soldering head 21 and the second soldering head 22, and the first soldering head 21 and the second soldering head 22 are respectively connected with the metal oxide sub-sensitivity resistor The first surface 11 and the second surface 12 of the substrate 10 (constructed of the zinc oxide material) are in contact, so that the molten tin solder 31 on the first soldering head 21 and the second soldering head 22 is applied to the first surface 11 and the second soldering head 22. On the two surfaces 12, ultrasonic waves are introduced from the ultrasonic source into the molten tin solder 31 through the first welding head 21 and the second welding head 22 at the same time, so that at least part of the region (especially the first welding head 21 and the first welding head 21 and the molten tin and solder 31) The region between the first surface 11, the region between the second horn 22 and the second surface 12) applies ultrasonic waves. Under the action of ultrasonic waves, the surface tension of the molten tin solder 31 is reduced, and its wettability with the first surface 11 and the second surface 12 is enhanced, so that, especially between the first welding head 21 and the first surface 11, The molten tin solder 31 in the region between the second solder head 22 and the second surface 12 is attached to the first surface 11 and the second surface 12 respectively with enhanced wettability;

c) As shown in Fig. 3c, the first soldering head 21 and the second soldering head 22 are moved along the first surface 11 and the second surface 12 respectively (as shown by the dashed arrows in Fig. 3c), so as to melt the tin solder 31 are attached and distributed over a larger area of the first surface 11 and the second surface 12, respectively, with enhanced wettability;

d) As shown in FIG. 3d, the first solder tip 21 and the second solder tip 22 are removed from the substrate 10, and the substrate 10 and the molten tin solder 31 thereon are cooled, and the molten tin solder 31 is attached to the first surface after cooling 11 and the second surface 12, a first electrode 41 and a second electrode 42 of the substrate 10 are formed (not shown in FIG. 3d due to the occlusion of the substrate 10).

With the method provided in the third embodiment, electrodes can be formed on two opposite surfaces of the substrate at the same time, thereby improving the efficiency.

4a-4d illustrate steps of an exemplary method according to Embodiment 4 of the present application. The steps of the method in the second embodiment are basically the same as those in the third embodiment, and the difference is only in the manner of providing the molten solder. In the method provided in the second embodiment, as shown in FIG. 4b, the substrate 10 and the solder head are immersed in the molten tin solder liquid 91 contained in the solder tank 90, so that the molten tin solder is provided on the surface of the substrate and the solder head between. The exemplary method according to the fourth embodiment of the present application includes the following steps;

a) As shown in Fig. 4a, using a fixture (not shown in Fig. 4a) to put the substrate 10 into the molten tin solder liquid 91 contained in the solder tank 90;

b) As shown in FIG. 4b, put the first soldering head 21 and the second soldering head 22 into the molten tin solder liquid 91 contained in the solder tank 90, and pass the first soldering head 21 and the second soldering head 22 at the same time Ultrasonic waves are introduced into the molten tin solder liquid 91 from an ultrasonic source, so that at least part of the region in the molten tin solder liquid 91 (especially the region between the first soldering head 21 and the first surface 11, the second soldering head 22 and the The area between the two surfaces 12) is applied with ultrasonic waves. Under the action of ultrasonic waves, the surface tension of the molten tin solder 32 in the area around the first soldering head 21 and the second soldering head 22 is reduced, and its wettability with the first surface 11 and the second surface 12 is enhanced, so that the In particular, the molten tin solder 32 in the regions between the first solder tip 21 and the first surface 11 and between the second solder tip 22 and the second surface 12 is attached to the first surface 11 and the second surface 12 with enhanced wettability, respectively. on the second surface 12;

c) As shown in Fig. 4c, the first soldering head 21 and the second soldering head 22 are moved along the first surface 11 and the second surface 12 respectively (as shown by the dashed arrows in Fig. 4c), so as to melt the tin solder 32 are attached and distributed over a larger area of the first surface 11 and the second surface 12, respectively, with enhanced wettability;

d) as shown in FIG. 4d, remove the first solder tip 21 and the second solder tip 22 from the substrate 10, and take out the substrate 10 from the molten tin solder liquid 91 to cool the substrate 10 and the molten tin solder 32 thereon, The molten tin solder 32 adheres to the first surface 11 and the second surface 12 after cooling. The molten tin solder 32 adhering to the sidewall of the substrate 10 between the first surface 11 and the second surface 12 is removed to isolate the first surface 11 and the second surface 12 from each other. The molten tin solder 32 left on the first surface 11 and the second surface 12 forms the first electrode 41 and the second electrode 42 of the substrate 10 (not shown in FIG. 4d due to the occlusion of the substrate 10).

The method of the fourth embodiment provides a method for providing molten solder between the substrate and the solder tip by immersion in a molten solder liquid. In this way, the solder can be more evenly distributed in the substrate, greatly improving the area and quality of the electrodes.

It should be noted that, in the method provided according to the present application, ultrasonic waves are introduced and applied to the solder through the solder tip. However, in other embodiments, the ultrasonic waves may also be introduced and applied to the solder through the substrate, ie the substrate is connected to the ultrasonic source, eg the substrate is connected to the ultrasonic source through a clamp.

5a-5b illustrate steps of an exemplary method according to Embodiment 5 of the present application. The steps of the method in the fifth embodiment are basically the same as those in the first embodiment, the only difference is that the electrodes 41 and the leads 51 are welded together while the electrodes 41 are formed. In the exemplary method of the fifth embodiment, as shown in FIG. 5 a , before the solder is provided to the first surface 11 of the substrate 10 , metal wires 51 are provided on the first surface 11 . Then, as shown in FIG. 5 b , the heated solder tip 21 is used to apply molten tin solder 31 to the first surface 11 , and the wire 51 is wrapped by the molten tin solder 31 . At the same time, ultrasonic waves are introduced into the molten tin solder 31 from an ultrasonic source through the horn 21, thereby applying ultrasonic waves to at least a part of the molten tin solder 31 (especially the area between the horn 21 and the first surface 11).

Similar to the method provided in the first embodiment, the molten tin solder 31 is cooled and attached to the first surface 11 to form the first electrode 41 of the substrate 10 , and the metal wire 51 is fixed into the first electrode 41 to form the first lead 51 .

According to the method provided in the fifth embodiment, the electrodes and the leads can be fabricated on the surface of the substrate at the same time, without the need for an additional step of fixing the leads on the electrodes.

According to the methods provided by other embodiments of the present application, the molten tin solder 31 can also be applied to the first surface 11 first, and then the metal wire 51 is inserted into the molten tin solder 31 to place the metal wire 51 in the molten tin solder 31 .

6a-6b illustrate steps of an exemplary method according to Embodiment 6 of the present application. The steps of the method in the sixth embodiment are basically the same as those in the fifth embodiment, the only difference is that the two welding heads (the first welding head 21 and the second welding head 22 ) Electrodes and leads are formed on one surface 11 and the second surface 12), respectively. Through the method provided in the sixth embodiment, the first electrode 41 and the first lead 51 can be simultaneously formed on the first surface 11 and the second electrode 42 and the second lead 52 can be simultaneously formed on the second surface 12 .

7a-7d illustrate steps of an exemplary method according to Embodiment 7 of the present application. The steps of the method in the seventh embodiment are basically the same as those in the sixth embodiment, and the difference is only in the manner of providing the molten solder. In the method provided in the seventh embodiment, as shown in FIG. 7b, the substrate 10, the leads 51, 52 and the soldering heads 21, 22 are immersed in the molten tin solder liquid 91 contained in the solder tank 90, so as to melt the molten tin solder Provided between the surface of the substrate and the horn.

The exemplary method according to the seventh embodiment of the present application includes the following steps;

a) As shown in FIG. 7a, use a clamp (not shown in FIG. 7a) to put the substrate 10, the first metal wire 51 and the second metal wire 52 into the molten tin solder liquid 91 contained in the solder tank 90;

b) As shown in FIG. 7b, put the first soldering head 21 and the second soldering head 22 into the molten tin solder liquid 91 contained in the solder tank 90, and pass the first soldering head 21 and the second soldering head 22 at the same time Ultrasonic waves are introduced into the molten tin solder liquid 91 from an ultrasonic source, so that at least part of the region in the molten tin solder liquid 91 (especially the region between the first soldering head 21 and the first surface 11, the second soldering head 22 and the The area between the two surfaces 12) is applied with ultrasonic waves. Under the action of ultrasonic waves, the surface tension of the molten tin solder 32 in the area around the first soldering head 21 and the second soldering head 22 is reduced, and its wettability with the first surface 11 and the second surface 12 is enhanced, so that the In particular, the molten tin solder 32 in the regions between the first solder tip 21 and the first surface 11 and between the second solder tip 22 and the second surface 12 is attached to the first surface 11 and the second surface 12 with enhanced wettability, respectively. on the second surface 12 .

After that, the substrate 10 is taken out from the molten solder liquid 91 , the substrate 10 and the molten solder 32 thereon are cooled, and the molten solder 32 is cooled and adhered to the first surface 11 and the second surface 12 . The molten tin solder 32 adhering to the sidewall of the substrate 10 between the first surface 11 and the second surface 12 is removed to isolate the first surface 11 and the second surface 12 from each other. The molten tin solder 32 remaining on the first surface 11 and the second surface 12 forms the first electrode 41 and the second electrode 42 of the substrate 10 . And the first metal wire 51 and the second metal wire 52 are respectively fixed to the first electrode 41 and the second electrode 42 to form the first lead wire 51 and the second lead wire 52 .

In other embodiments according to the present invention, the solder is not limited to tin, but can also be other materials. The material constituting the solder may be selected from the group consisting of gold, silver, copper, tin, aluminum, zinc, and their alloys.

In other embodiments according to the present invention, a metallization layer may be pre-deposited on the first surface and the second surface of the substrate, the first electrode and the second electrode are attached on the metallization layer, and contact the substrate through the metallization layer Material. The material of the metallization layer can be selected from one of the group consisting of the following materials and their alloys: gold, silver, copper, aluminum, zinc. With the methods provided herein, solder can be attached to the metallization layer with enhanced wettability. In addition, ultrasonic waves can remove the oxide layer on the surface of the metallization layer, thereby further enhancing the wettability of the solder on the surface of the metallization layer material.

It should be understood that although this specification is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

The above descriptions are only illustrative specific embodiments of the present application, and are not intended to limit the scope of the present application. Any equivalent changes, modifications and combinations made by any person skilled in the art without departing from the concept and principles of the present application shall fall within the protection scope of the present application.

Claims (18)

1. A method of making an electrode using an ultrasonic welding process, comprising the steps of:

providing molten solder between a first surface of a substrate and a first soldering tip;

applying ultrasonic waves to the molten solder through at least one of the substrate and the first soldering tip,

the molten solder, after cooling, is attached as a first electrode to the first surface of the substrate.

2. The method of claim 1, wherein the step of providing molten solder between the first surface of the substrate and the first soldering tip comprises: at least one of the substrate and the first soldering tip is heated to melt the solder.

3. The method of claim 1, wherein providing molten solder between the first surface of the substrate and the first soldering tip comprises:

immersing the substrate and the first soldering tip in a molten solder liquid to provide molten solder between the first surface of the substrate and the first soldering tip.

4. The method of claim 1, further comprising the step of: placing a wire in the molten solder,

after the molten solder is cooled, the wire is fixed as a first lead on the first surface of the substrate by the solder and is electrically connected to the substrate through the solder.

5. The method of claim 1, the substrate further having a second surface opposite the first surface,

wherein the method further comprises the steps of:

providing molten solder between the second surface of the substrate and the second soldering tip;

applying ultrasonic waves to the molten solder through at least one of the substrate and the second soldering tip,

the molten solder, after cooling, is attached as a second electrode to the second surface of the substrate.

6. The method of claim 5, wherein the step of providing molten solder between the second surface of the substrate and the second soldering tip comprises:

at least one of the substrate and the second soldering tip is heated to melt the solder.

7. The method of claim 5, wherein providing the molten solder between the second surface of the substrate and the second soldering tip comprises:

immersing the substrate and the second soldering tip in a molten solder liquid to provide molten solder between the second surface of the substrate and the second soldering tip.

8. The method of claim 5, further comprising the steps of: placing a wire in the molten solder,

after the molten solder is cooled, the wire is fixed as a second lead on the second surface of the substrate by the solder and is electrically connected to the substrate through the solder.

9. The method of claim 5, wherein the first bonding tool and the second bonding tool are different bonding tools, and wherein the process of fabricating a first electrode on the first surface with the first bonding tool is performed simultaneously with the process of fabricating a second electrode on the second surface with the second bonding tool.

10. The method of claim 1, wherein the first surface has a metallization layer thereon, and the first electrode is attached to the metallization layer of the first surface.

11. The method of claim 5, wherein the second surface has a metallization layer thereon, and the second electrode is attached to the metallization layer of the second surface.

12. The method according to claim 10 or 11, wherein the material of the metallization layer is selected from one of the group consisting of: gold, silver, copper, aluminum, zinc.

13. The method of claim 1, wherein the substrate is a metal oxide varistor.

14. The method of claim 1, wherein the solder is comprised of a material selected from the group consisting of: gold, silver, copper, tin, aluminum, zinc.

15. A method according to claim 3 or 7, wherein the substrate is immersed in the molten solder liquid under the grip of a jig.

16. The method of claim 15, wherein an ultrasonic source applies ultrasonic waves to the substrate through the fixture.

17. The method of claim 1, further comprising the steps of: moving the first soldering tip along the first surface to distribute the molten solder over the first surface.

18. The method of claim 1, further comprising the steps of: moving the second soldering tip along the second surface to distribute the molten solder over the second surface.

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