Power inductor and manufacturing method thereof

Abstract

The invention discloses a power inductor and a manufacturing method thereof.The coil of the power inductor comprises at least two electrode composite layers, each electrode composite layer is provided with a double-face Cu layer, the at least two electrode composite layers are connected in a laminated mode through a solder layer, a Ni layer and an Au layer are sequentially arranged on the Cu layer at the connecting position of every two adjacent electrode composite layers, and the Ni layer and the Au layer are arranged on the connecting position of the two adjacent electrode composite layers. And the two Au layers are in laminated connection through the solder layer. According to the invention, a new plating layer structure of the electrode composite layer is adopted, the Ni layer and the Au layer are added, the wettability of Au is good, and the adhesiveness of Au and copper is improved through the Ni layer, so that the wettability of the surface of the electrode can be improved, molten solder can be fully spread on the surface of the electrode in the subsequent welding process, the bubble cavity generation area in the welding process is reduced, and the welding quality is improved. And the interlayer binding force is increased, so that the contact reliability of the product is improved.

Description

Technical Field

[0001] The invention relates to a power inductor and a manufacturing method thereof. Background Art

[0002] With the continuous progress of the communications industry, the application of 5G has become popular, and the research and development of 6G is also underway. More miniaturized inductor components have become a development trend. In order to meet the higher performance requirements of inductor components, such as electrical properties and reliability, it is particularly important to carefully design the internal electrode structure and composition of the inductor components.

[0003] In the prior art, the internal coils of some power inductor structures are connected together by printing solder paste reflow soldering using a single-layer electrode composite layer (FPC, flexible circuit board) prepared by a subtractive method. However, it is found in practice that a large number of bubbles and cavities are generated at the solder joints during the reflow soldering process, causing the inter-layer electrode bonding force to deteriorate, affecting the contact reliability of subsequent products. Summary of the invention

[0004] The embodiment of the present application provides a power inductor and a method for manufacturing the same, thereby reducing the proportion of bubble void area at the junction of the electrode composite layer.

[0005] To this end, an embodiment of the present application provides a power inductor, wherein the coil of the power inductor includes at least two electrode composite layers, the electrode composite layer has a double-sided Cu layer, and the at least two electrode composite layers are stacked and connected by a solder layer, wherein a Ni layer and an Au layer are sequentially arranged on the Cu layer at the connection between two adjacent electrode composite layers, and the two Au layers are stacked and connected by the solder layer.

[0006] In some embodiments, the invention also has the following technical features:

[0007] The electrode composite layer has multiple layers which are laminated and pressed together by welding.

[0008] The Ni layer has a thickness of 0.5-3 μm.

[0009] The thickness of the Au layer is 20-300 nm.

[0010] The solder layer is a tin-containing solder layer, and the thickness thereof is 30 μm to 100 μm.

[0011] The present invention also proposes a method for manufacturing a power inductor, comprising the following steps: S1: sequentially forming a Ni layer and an Au layer on a Cu layer of a single electrode composite layer that needs to be connected to each other; S2: forming a solder layer on the Au layer to obtain a symmetrically distributed structure of Cu layer / Ni layer / Au layer / solder layer / Sn layer / Ni layer / Au layer, and pressing at least two electrode composite layers together through a welding process to obtain a coil sample; S3: insulating and coating the coil sample in S2; S4: hot pressing, insulating and coating, dicing, and terminally electrode-forming the coated coil sample and magnetic material to prepare the power inductor.

[0012] In some embodiments, the invention also has the following technical features:

[0013] In step S1, the electrode composite layer is obtained by a subtractive process; and the welding process in step S2 refers to reflow welding.

[0014] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0015] The inventors have found that the poor wettability of the copper electrode surface to molten solder (such as solder paste) after oxidation is one of the reasons for the generation of a large number of bubbles and voids at the solder joints during the welding process. To this end, the present invention adopts a new electrode composite layer structure, and sequentially adds a Ni layer and an Au layer on the Cu layer. The wettability of Au is better, and the adhesion between Au and copper is improved by the Ni layer, thereby improving the wettability of the electrode surface. In the subsequent welding process, the molten solder (such as solder paste) can be fully spread on the electrode surface, reducing the area of ​​bubble void generation during the welding process, increasing the interlayer bonding force, and thereby improving the contact reliability performance of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a three-dimensional schematic diagram of a power inductor according to an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of the cross-sectional structure of an electrode unit of a coil of a power inductor in the prior art;

[0018] Figure 3 This is a schematic diagram of the cross-sectional structure of an electrode unit of the coil of the power inductor according to an embodiment of the present application.

[0019] In the figure, 1 is a Cu layer, 2 is a dielectric material layer, 3 is a solder layer, 4 is a Ni layer, 5 and 6 are lead-out electrodes, 7 is an Au layer, 10 is a connection point, and 11 is a connection hole. DETAILED DESCRIPTION

[0020] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] like Figure 1 As shown, it is a structural diagram of the coil of the power inductor of the present invention, the power inductor includes a coil and lead-out terminal electrodes 5 and 6 connected to the coil, the coil of the power inductor includes at least two layers of electrode composite layers, the electrode composite layer is a component of the coil in the power inductor, and the electrode composite layer has a double-sided Cu layer (for example, Figure 2 As shown, the electrode composite layer includes a dielectric material layer 2, and Cu layers 1 (also called Cu electrodes) respectively arranged on the upper and lower surfaces of the dielectric material layer, the Cu layers 1 on the upper and lower surfaces are connected through a connecting hole 11, and the at least two electrode composite layers are laminated and connected through a solder layer 3, wherein, Figure 3 As shown, a Ni layer 4 and an Au layer 7 are sequentially arranged on the Cu layer 1 at the connection of two adjacent electrode composite layers, and the two Au layers are laminated and connected through the solder layer 3 (in this example, the solder layer is a tin-containing solder layer composed of the following three metals in mass fractions: Sn 96%, Ag 3.5%, and Cu 0.5%). Figure 1 As shown, 10 is a connection point when the layers are connected); wherein, two adjacent electrode composite layers connected together are called an electrode unit, and the coil is composed of n such electrode units.

[0022] In some embodiments, the electrode composite layer has multiple layers, which are laminated and pressed together by welding (eg, reflow soldering).

[0023] In some embodiments, the Ni layer has a thickness of 0.5-3 μm.

[0024] In some embodiments, the Au layer has a thickness of 20-300 nm.

[0025] In some embodiments, the solder layer is a tin-containing solder layer, and the thickness thereof is 30 μm to 100 μm.

[0026] In some embodiments, after the two Au layers are laminated and connected via the solder layer, an intermetallic compound is formed between the Au layer and the solder layer.

[0027] like Figure 2 As shown, the internal coil of the partial power inductor structure in the prior art is a single electrode composite layer (flexible circuit board) prepared by a subtractive method and connected together by reflow soldering through printing solder paste (i.e. solder layer 3), and the mass fractions of Sn, Ag, and Cu in the solder paste are respectively: Sn 96%, Ag 3.5%, and Cu 0.5%. However, this circuit has the aforementioned disadvantages. The following embodiments of the present invention have made improvements on this.

[0028] like Figure 3As shown, in this embodiment, after a single electrode composite layer is prepared by a subtractive method, a certain thickness of Ni (nickel) and Au (gold) are electroplated on the Cu (copper) layer 1 of the single electrode composite layer, and then at least two electrode composite layers are stacked together by reflow soldering.

[0029] The specific steps are as follows:

[0030] Step 1: After the single electrode composite layer required for the power inductor sample is prepared by the subtractive method, Ni (1.5 μm) and Au (50 nm) are electroplated on the Cu layer 1 of the single electrode composite layer to be connected to each other in sequence;

[0031] Step 2: forming a tin-containing solder layer on the Au layer on the electrode composite layer in step 1 to obtain a symmetrically distributed structure of Cu layer / Ni layer / Au layer / tin-containing solder layer / Au layer / Ni layer / Cu layer, and laminating the layers together by reflow soldering to obtain a coil sample; the reflow soldering process is the same as the prior art; wherein, during the reflow soldering lamination process, an intermetallic compound is formed at the interface between the Au layer and the solder layer;

[0032] Step 3: The electrode composite layer coil sample in step 2 is insulated and coated with an insulating material, and the insulating material is the same as that in the prior art;

[0033] Step 4: The coated coil sample and magnetic material are hot pressed, insulated and coated, cut and terminated to prepare the finished product.

[0034] The power inductor manufactured by the above method has a coil structure of Cu / Ni / Au / solder layer / Au / Ni / Cu symmetrically distributed.

[0035] The power inductor structure manufactured by the above method has an internal coil electrode structure of Cu / Ni / Au / (Sn, Ag, Cu) / Au / Ni / Cu symmetrically distributed, that is, two composite metal electrodes of the same structure: Cu / Ni / Au are combined together by printing solder paste (mainly composed of Sn, Ag, Cu), and its composition can be scanned and analyzed by EDS.

[0036] Internal coil electrode of power inductor: The shape and size of Cu electrode are designed according to the electrical properties of the product. The thickness of Ni layer is 0.5-3.0μm and the thickness of Au layer is 20nm-300nm.

[0037] After testing, the performance parameters of the product made by the above method (hereinafter referred to as Model 3) and the prior art product (i.e., not plated with Ni and Au, hereinafter referred to as Model 1) are compared as follows:

[0038] Table 2 Comparison of performance parameters of different models

[0039] sample L / nH DCR / mΩ Isat / A Solder joint void area percentage Model 1 482 18 6.5 25 Model 3 485 18 6.5 5

[0040] As can be seen from the table above, the electrical properties of the samples in the embodiment, such as inductance L, DCR, and saturation current Isat, are comparable to those of the original structure products, and no degradation has occurred. At the same time, metallographic section analysis of the product shows that the proportion of bubble void area at the junction of the coil layers in the embodiment has decreased.

[0041] Experiments show that adding a Ni-Au plating layer to the original electrode structure can improve the wettability of the electrode surface (the wettability of the sample can be quantified using a wetting balance balance). In the subsequent reflow soldering process, the molten solder paste can be fully spread on the electrode surface, reducing the area of ​​bubble void generation during the reflow soldering process, increasing the interlayer bonding strength, and thereby improving the contact reliability of the product.

[0042] The technical solution in the above-mentioned embodiment of the present application has at least the following technical effects or advantages: the use of a new FPC coil electrode plating structure can improve the wettability of the coil electrode surface, reduce the area ratio of bubbles and holes between electrode layers after sample reflow soldering, and improve the contact reliability performance of the product.

[0043] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0044] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A power inductor, wherein the coil of the power inductor comprises at least two electrode composite layers, the electrode composite layer has a double-sided Cu layer, and the at least two electrode composite layers are laminated and connected by a solder layer, characterized in that: A Ni layer and an Au layer are sequentially arranged on the Cu layer at the connection point of two adjacent electrode composite layers, and the two Au layers are laminated and connected through the solder layer.

2. The power inductor according to claim 1, characterized in that: The electrode composite layer has multiple layers which are laminated and pressed together by welding.

3. The power inductor according to claim 1, characterized in that: The Ni layer has a thickness of 0.5-3 μm.

4. The power inductor according to claim 1, characterized in that: The thickness of the Au layer is 20-300 nm.

5. The power inductor according to claim 2, characterized in that: The solder layer is a tin-containing solder layer, and the thickness thereof is 30 μm to 100 μm.

6. The power electronic device according to claim 1, characterized in that: After the two Au layers are laminated and connected via the solder layer, an intermetallic compound is formed between the Au layer and the solder layer.

7. A method for manufacturing a power inductor, characterized in that: The steps include: S1: sequentially forming a Ni layer and an Au layer on the Cu layer of a single electrode composite layer that needs to be connected to each other; S2: forming a solder layer on the Au layer to obtain a symmetrically distributed structure of Cu layer / Ni layer / Au layer / solder layer / Sn layer / Ni layer / Au layer, and pressing at least two electrode composite layers together through a welding process to obtain a coil sample; S3: Insulate and coat the coil sample in S2; S4: hot pressing, insulating and coating, dicing and terminal electrode are performed on the coated coil sample and magnetic material to prepare the power inductor.

8. The method according to claim 7, characterized in that In step S1, the electrode composite layer is obtained by a subtractive process; and the welding process in step S2 refers to reflow welding.

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