CN101145434A - A terminal electrode of a chip ferrite inductor and its preparation method - Google Patents

Abstract

A terminal electrode for chip ferrite inductors and a preparation method thereof are provided, which belongs to the technical field of chip ceramic electronic components. The terminal electrode for chip ferrite inductors has a two-layered structure and is prepared by firstly forming an autologous electrode on the terminal surface of a chip ferrite inductor to increase the surface electronic conductivity of the terminal ferrite of the chip ferrite inductor, to reduce the resistivity less than 10<4> Ohm*m and to allow the ferrite on the terminal surface semi-conductive even metallized; then electroplating Ni on the autologous electrode as a conductive seed layer to form a metal Ni layer; and finally electroplating Sn or Sn-Pb alloy on the Ni layer to obtain a Ni/Sn or Sn-Pb two-layered electrode. The invention has the advantages of no use of precious metal paste in the prior preparation process of terminal electrode in chip ferrite inductor, reduced production cost, reduced consumption of precious metals, and simplified production process.

Description

A terminal electrode of a chip ferrite inductor and its preparation method

technical field

The invention belongs to the technical field of chip ceramic electronic components, in particular to a terminal electrode of a chip ferrite inductor and a preparation method thereof.

Background technique

The terminal electrode preparation of chip ceramic electronic components is now generally using three-layer electrode technology, that is, firstly use a coating machine to dip precious metal paste, such as silver paste, on both ends of the chip ceramic component body, and then sinter it at high temperature. Form the bottom electrode, then electroplate a layer of nickel as a barrier layer, and finally electroplate a layer of tin or tin-lead alloy layer as a solderable layer, that is, form a three-layer electrode structure of silver/nickel/tin or tin-lead [D.A.Bem, C.J.Feltz, R.Haynes, and S.C.Pinault, Statistical Determination of Plating Process Variables for Multilayer Ceramic Chip Capacitors, Journal of the American Ceramic Society 72(12), 2279-2281(1989)]. The preparation of terminal electrodes requires the use of two different technologies, high-temperature sintering and electroplating, and the investment and use of two different sets of equipment, the process is cumbersome and the process is complicated. As international non-ferrous metal prices continue to rise, the cost of precious metal materials continues to increase as a proportion of total production costs, causing great pressure on the environment and metal resources. And as the size of chip components decreases, the end-coating process needs to use a higher-precision end-coating machine.

Contents of the invention

The object of the present invention is to provide a novel terminal electrode of a chip ferrite inductor and a preparation method thereof. The molar percentage of iron element in the ferrite material is 10-40%. The present invention eliminates the use of terminal noble metal electrodes and terminal coating machines, and uses one electroplating line to complete the preparation process of terminal electrodes.

The terminal electrode of the chip ferrite inductor provided by the present invention has a two-layer structure. Firstly, the self-body electrode formed on the surface of the chip inductor terminal, that is, through the action of atomic hydrogen, improves the ferrite surface of the chip inductor terminal. The electronic conductivity of the surface (resistivity less than 10 ⁴ Ω·m) makes the ferrite on the surface of the terminal semiconductive or even metallized, and then uses the self-body electrode as a conductive seed layer to electroplate nickel to form a layer of metallic nickel (2 ~20μm), and then electroplate a tin or tin-lead alloy layer (2~20μm) on the nickel layer to form a nickel/tin or tin-lead two-layer electrode structure.

The concrete preparation method of terminal electrode of the present invention is as follows:

First, mix the chip ferrite inductor and a dispersed conductive medium such as steel balls together, and then place them together in an aqueous electrolyte solution (electrolyte concentration 5 g/L-500 g/L), such as sodium sulfate aqueous solution, etc., in The purpose of adding electrolyte to the water is to increase the conductivity of the aqueous solution, and then use the conductive medium as the cathode to electrolyze the aqueous solution to treat the inductor with atomic hydrogen, and vibrate or stir the conductive medium and the chip inductor during the electrolysis of the aqueous solution. Conductance increase effect, cathode current density 0.1-5 amps/dm2, electrolyte aqueous solution temperature 0-80 ℃, atomic hydrogen is generated on the outcrop of the inner electrode of the chip inductor, and hydrogen migrates to the ferrite near the outcrop of the inner electrode On the surface, through the conductance modification of atomic hydrogen, the electron conductance of the ferrite surface at the end of the inductor is greatly increased, semiconducting or even metallization occurs, and the resistivity is less than 10 ⁴ Ω.m. With the prolongation of atomic hydrogen treatment time, the conductance-modified region grows along the edge of the ceramic surface with the inner electrode outcrop as the center, and the area of the conductance-modified region increases to form a self-electrode. Then take out the chip inductor and the conductive medium, clean it with deionized water, and use the vibration plating method to electroplate the nickel layer on the end of the chip inductor. Due to the large electronic conductivity of the self-electrode, the metal nickel can be directly deposited during the nickel plating process. Electrons are obtained and deposited on this self-electrode. Then take out the chip inductor and the conductive medium, clean it with deionized water, and electroplate tin or tin-lead alloy layer on the nickel layer by vibration electroplating or barrel plating to make a terminal electrode with a complete structure.

The advantages of the present invention are: eliminating the use of precious metal paste in the preparation of terminal electrodes of chip ferrite inductors, reducing production costs and saving precious metal resources; eliminating the end coating process, eliminating the high temperature sintering process of precious metal paste, High-temperature sintering tail gas emission; equipment investment for end-coating machines and high-temperature furnaces is eliminated, and the production process is simplified; since the self-electrodes of chip ferrite inductors are prepared by electrochemical atomic hydrogen treatment, electroplating equipment can be used, so the use of A set of electroplating lines can complete the preparation of terminal electrodes of chip components. Since the size of the self-electrode has a clear corresponding relationship with the electrochemical treatment time, the growth progress of the self-electrode can be precisely controlled by time, so the present invention is also suitable for the preparation of terminal electrodes of small-sized chip components, eliminating the need for high-precision coating Terminal use.

The invention is suitable for preparing terminal electrodes of chip ferrite components.

Description of drawings

Figure 1 is a schematic diagram of the structure of terminal electrodes of chip components commonly used at present. Among them, the chip component 1 , the noble metal electrode 2 on the terminal, the nickel layer 3 , and the tin or tin-lead layer 4 .

Fig. 2 is a schematic diagram of the structure of the terminal electrode of the present invention. Among them, the self-body electrode 5 on the end.

Detailed ways

Example 1

Select 100 pieces of sintered nickel-copper-zinc ferrite chip multilayer inductor (MLCI) blanks, the size is 0402 (0.04 inches × 0.02 inches), and the ferrite composition is Ni _0.3 Zn _0.5 Cu _0.2 Fe ₂ O ₄ , the molar percentage of iron element is 28.6%. Put the chip inductor and the steel ball with a diameter of 0.5mm in the hanging basket, immerse the hanging basket in the sodium sulfate aqueous solution, use the titanium basket as the anode, electrolyze the aqueous solution under vibration conditions, and perform electrochemical atomic hydrogen on the chip inductor. Conductivity modification treatment to prepare the self-body electrode of the chip inductor. The process parameters are as follows:

Sodium sulfate (Na ₂ SO ₄ ) aqueous solution 50 g/L

Cathode current density 2 amps/square decimeter

temperature room temperature

After 0.5 hours, take out the hanging basket, clean the hanging basket, chip inductors and steel balls with deionized water, then place the hanging basket in the electroplating nickel plating solution, and use the vibration electroplating method for nickel plating, the electroplating nickel process The parameters are as follows:

Nickel sulfamate 400 g/l

Nickel Chloride 20 g/L

Boric acid 40 g/L

pH 4

Temperature 50℃

Cathode current density 2 amps/square decimeter

Next, take out the hanging basket, clean the hanging basket, chip inductors and steel balls with deionized water, then place the hanging basket in the electroplating tin plating solution, and use the vibration electroplating method for tinning. The electroplating tinning process parameters are as follows:

Stannous chloride 60 g/L

Citric acid 30 g/L

Ammonium bifluoride 50 g/L

Polyethylene glycol 20 g/L

pH 6

temperature room temperature

Cathode current density 1 ampere/square decimeter

Finally, take the chip inductor out of the hanging basket, clean it with deionized water, and then bake it at 150°C for 2 hours. The resulting terminal electrode has good bonding force and solderability.

Example 2

Select 100 sintered planar hexagonal Co2Z ferrite chip inductor blanks, the size is 0603 (0.06 inches × 0.03 inches), the ferrite composition is Ba ₃ Co ₂ Fe ₂₄ O ₄₁ , and the molar percentage of iron element is 34.3%. Put the chip inductor and the steel ball with a diameter of 1mm in the hanging basket, immerse the hanging basket in the sodium sulfate aqueous solution, use the titanium basket as the anode, electrolyze the aqueous solution under vibration conditions, and perform electrochemical atomic hydrogen conductance on the chip inductor. Modification treatment to prepare the self-body electrode of the chip inductor. The process parameters are as follows:

Sodium sulfate (Na ₂ SO ₄ ) aqueous solution 200 g/L

Cathode current density 0.5 ampere/square decimeter

Temperature 50℃

After 0.5 hours of treatment, take out the hanging basket, clean the hanging basket, chip inductors and steel balls with deionized water, then place the hanging basket in the electroplating nickel plating solution, and use the method of vibration electroplating for nickel plating, electroplating nickel process The parameters are as follows:

Nickel sulfate (NiSO ₄ 7H ₂ O) 250 g/L

Nickel chloride (NiCl ₂ 6H ₂ O) 50 g/L

Boric acid 40 g/l

Saccharin 1 g/L

pH 4.3

Temperature 50℃

Cathode current density 2 amps/square decimeter

Then take out the hanging basket, clean the hanging basket, chip inductors and steel balls with deionized water, place the chip inductors and steel balls in a barrel plating drum for electroplating, use the barrel plating method for tin plating, and the process parameters are the same as in the embodiment 1. Finally, take the chip inductor out of the hanging basket, clean it with deionized water, and then bake it at 150°C for 2 hours. The resulting terminal electrodes have good bonding force and solderability.

Claims (5)

1. a terminal electrode of a chip ferrite inductor, the iron element mole percentage content is 10～40% in the ferrite material, it is characterized in that, has nickel/tin or tin-lead two-layer electrode structure, at first in A self-electrode is formed on the surface of the terminal of the chip inductor. Through the action of atomic hydrogen, the ferrite on the surface of the terminal is semiconducted or even metallized. The resistivity is less than 10 ⁴ Ω·m, and then the self-electrode is used as a conductive seed layer Electroplating nickel to form a layer of metallic nickel, and then electroplating a layer of tin or tin-lead alloy on the nickel layer to form a nickel/tin or tin-lead two-layer electrode structure. 2. The terminal electrode according to claim 1, wherein the thickness of the metal nickel layer is 2-20 μm; the thickness of the tin or tin-lead alloy layer is 2-20 μm; 3. A method for preparing the terminal electrodes of the chip ferrite inductor claimed in claim 1, wherein the preparation process is: (1) Mix the chip ferrite inductor and the steel ball of the dispersed conductive medium together, and then place them together in the aqueous electrolyte solution; (2) With the conductive medium as the cathode, the electrolytic aqueous solution is used to treat the inductor with atomic hydrogen, the cathode current density is 0.1-5 amperes/dm2, the temperature of the aqueous electrolyte solution is 0-80°C, and the outcrop of atomic hydrogen on the inner electrode of the chip inductor Hydrogen migrates to the ferrite surface near the outcrop of the inner electrode, and through the conductance modification of atomic hydrogen, the electronic conductance of the ferrite surface at the inductor end increases, semiconducting or even metallizing occurs, and the resistivity is less than 10 ⁴ Ω·m; with the prolongation of the atomic hydrogen treatment time, the conductance modification area grows along the edge of the ceramic surface with the electrode outcrop as the center, and the area of the conductance modification area increases to form a self-body electrode; (3) Take out the chip inductor and the conductive medium, clean it with deionized water, and use the vibration plating method to electroplate the nickel layer on the end of the chip inductor. During the nickel plating process, the nickel ions are directly deposited on the self-electrodes by obtaining electrons. Then take out the chip inductor and conductive medium, clean them with deionized water, and use vibration plating or barrel plating to electroplate tin or tin-lead alloy layer on the nickel layer to make a terminal electrode with a complete structure. 4. The method according to claim 3, wherein the aqueous electrolyte solution is an aqueous solution of sodium sulfate, and the electrolyte concentration of the aqueous electrolyte solution is 5 g/L to 500 g/L. 5. The method according to claim 3, characterized in that, during the electrolysis of the aqueous solution, the conductive medium and the chip inductor are vibrated or stirred to increase the conductance modification effect.

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