TWI737568B - Leadless stacked ceramic capacitors - Google Patents

Abstract

The present invention provides a leadless stacked ceramic capacitor, which is interspersed with a plurality of internal electrodes alternately arranged in each capacitor body of a plurality of multilayer ceramic capacitors, and the two ends of the capacitor body are respectively provided with internal electrode terminals The part forms an electrical connection to the external electrodes, and a plurality of multilayer ceramic capacitors are stacked in a vertical direction, and the two adjacent external electrodes are cured to form a bonding interface by polymer conductive adhesive, and the polymer conductive adhesive The glue contains 75%~85% metal powder and 15%~25% viscose to provide support strength and conductive channels. This capacitor stack structure can eliminate the trouble of using metal leads and TLPS paste that requires high temperature heating and sintering. In addition to In addition to simplifying the manufacturing process, the operating temperature of the non-soldering operation of the polymer conductive adhesive is relatively low, and the process variation factors are relatively reduced.

Description

Leadless stacked ceramic capacitors

The present invention provides a leadless stacked ceramic capacitor, in particular, that the external electrodes of a plurality of stacked ceramic capacitors are adhered and fixed by conductive adhesive.

According to the fact that the production of electronic components is gradually required to be developed in multiple tasks to meet the complex signal transmission and operation between high-end electronic components, and to enable the capacitors of passive components to be miniaturized, high capacitance, and better stability. The trend of sex is moving forward, and traditional capacitors have also been transformed into multilayer ceramic capacitors manufactured in chip type. Together with the refinement of production equipment and continuous breakthroughs in process technology, not only can their size be greatly reduced, but also the production cost can be reduced, but they are usually also taught. With high capacity and high reliability product requirements.

The multi-layer ceramic capacitor (MLCC) in ceramic capacitors has a capacitance value proportional to the surface area of the product and the number of layers of ceramic film stacked, and the MLCC can be directly adhered through the surface mount technology (SMT) process , The production speed is faster, and it has the advantages of easy wafering, small size and good frequency characteristics, and it has become the mainstream product of the capacitor industry. Its disadvantage is that the capacitance value is small, but with the technological advancement of ceramic film stacking, The higher the content of its capacitance value, it can gradually replace the market applications of medium and low capacitance (such as electrolytic capacitors and mass capacitors, etc.), so that relevant MLCC manufacturers are more actively engaged in research and development for the improvement of capacitance values.

Furthermore, in order to form a high-capacity ceramic capacitor and assemble it on a circuit board, a stacked structure is usually formed in the form of metal leads or a lead frame. Please refer to the conventional multilayer ceramic capacitor stack as shown in Figure 6. The two outer electrode ends A1 of the multilayer ceramic capacitor A are formed by solder B to form a joint, and are welded to the joint surface C1 on the opposite inner side of the two lead frames C to form a stack structure, and then the outer leads C2 of the lead frame C are welded to On the circuit board, the two lead frames C can provide support strength and conductive channels at the same time, so that the total capacitance is worth increasing. However, the temperature required for the soldering process is mostly higher than 300°C. If the heating rate during the soldering process is too fast, It will cause the multilayer ceramic capacitor A to heat up quickly and cause cracks or damages, resulting in an increase in the defect rate. If the welding temperature is too slow, it will still need to be cleaned after the flux is used, which will also cause a lot of trouble and trouble. .

In addition, in recent years, transient liquid phase sintering (Transient-Liquid-Phase-Sintering, TLPS), such as copper (Cu)-tin (Sn) solder, has been changed to provide a more novel stacked ceramic capacitor without relying on metal leads. The improved method is to add two different metal materials, a high melting point and a low melting point, to the solder used at the same time, and form a stacked junction on the outer electrode end of each ceramic capacitor, so that multiple ceramic capacitors are stacked and supported each other like building blocks. It will not collapse, and the junction will also form a conductive path. Because the lead frame is not used for mounting, it must be able to resist the stress damage caused by the bending of the substrate, and it cannot even cause the ceramic capacitor stacking position or junction to occur to an unexpected degree. Stress failure.

In addition, TLPS paste as a bonding material needs to rely on high-temperature heating and sintering to easily form intermetallic compounds. Although it has the advantage of improving mechanical strength, high-temperature heating and phase change processes will increase the process variation factors. The microstructure is easy to form hard and brittle intermetallic compounds, even after the phase change is formed at the stacking position or the surface of the bonding point Microcracks or micro gaps after volume changes, even if they have sufficient support strength, ultimately cannot effectively provide toughness that can resist bending or vibration of the repetitive slab. On the contrary, they will cause stress concentration to form a source of structural damage or rupture, which makes product applications suffer. Many limitations are also due to the fact that the TLPS paste cannot be filled with nickel or tin plating after sintering, and it is difficult to react with the electroplating solution to form a uniform and detailed electroplating surface. Therefore, the problem of micro cracks or micro gaps cannot be improved. , Which is the direction that those engaged in this industry want to study and improve.

Therefore, in view of the above-mentioned deficiencies, the inventor collected relevant information, evaluated and considered from many parties, and with years of experience in this industry, continued to trial and modify, and designed this type of leadless stacked ceramic capacitor invention patent. Born.

The main purpose of the present invention is to change the external electrodes of a plurality of multilayer ceramic capacitors to use polymer conductive adhesive as the bonding material, and after curing, the bonding interface can be formed to provide support strength and conductive channels, so that the plurality of multilayer ceramic capacitors The external electrodes can be stacked in the vertical direction through the interface to be electrically connected and form a series combination. The total capacitance value is also proportional to the number of capacitors stacked, and the polymer conductive adhesive contains 75%-85% The metal powder and 15%~25% viscose can make the bonding interface have sufficient supporting adhesive strength, and the toughness required to absorb the bending or vibration energy of the board, and resist the mechanical damage caused by the repeated bending of the board or the vibration environment. It can eliminate the trouble of using metal leads and TLPS paste to heat and sinter at high temperatures, simplifying the process, and the operating temperature of the solderless operation of the polymer conductive adhesive is relatively low, and the process variation factors are relatively reduced.

The secondary purpose of the present invention is that the outside of the bonding interface where the external electrodes are stacked between a plurality of multilayer ceramic capacitors can be electroplated, and the electroplating is formed by nickel plating and tin plating in sequence. The first plating layer and the second plating layer of the strengthening layer, because the polymer conductive adhesive used in the interface interface contains sufficient metal powder, it can react with the plating solution to form a uniform and fine plating surface, causing any micro cracks or cracks on the interface interface. After electroplating, the micro gap will be filled by the electroplating strengthening layer to avoid the formation of cracked nuclei. It can also extend the flat side surface together on each interface and the outer electrode of the multilayer ceramic capacitor, so that the electroplating strengthening layer can completely cover multiple build-up layers The outer electrode of the ceramic capacitor strengthens the mechanical strength of the interface.

100: Multilayer ceramic capacitor

110: Capacitor body

111: Dielectric layer

120: inner electrode

130: External electrode

131: Burning copper layer

200: then interface

210: Polymer conductive adhesive

220: Electroplating strengthening layer

221: first coating

222: second coating

A: Multilayer ceramic capacitor

A1: The end of the outer electrode

B: Solder

C: Lead frame

C1: Joint surface

C2: External lead

[Figure 1] is a perspective view of a preferred embodiment of the present invention.

[Figure 2] is an exploded perspective view of a preferred embodiment of the present invention.

[Figure 3] is a cross-sectional side view of a preferred embodiment of the present invention.

[Figure 4] is a side sectional view of another preferred embodiment of the present invention.

[Figure 5] is the data table of the lateral push experiment of the present invention.

[Figure 6] is a schematic cross-sectional side view of a conventional multilayer ceramic capacitor stack.

In order to achieve the above-mentioned purposes and effects of the present invention, the technical means and structure adopted by the present invention are illustrated in detail below to illustrate the structure and functions of the preferred embodiments of the present invention for a complete understanding.

Please refer to Figures 1 to 3, which are respectively a three-dimensional appearance view, a three-dimensional exploded view and a side cross-sectional view of a preferred embodiment of the present invention. It can be clearly seen from the figures that the leadless stacked ceramic capacitor of the present invention It includes a plurality of multilayer ceramic capacitors 100 stacked in a direction perpendicular to each other. The multilayer ceramic capacitor 100 includes a capacitor body 110 and is connected to each capacitor body A plurality of dielectric layers 111 are stacked in each of the two adjacent dielectric layers 111, and a plurality of internal electrodes 120 arranged face to face in a staggered manner are inserted between each two adjacent dielectric layers 111, and the ends of the internal electrodes 120 are respectively exposed to The two ends of the capacitor body 110 are respectively provided with an external electrode 130 which is electrically connected to the end of the internal electrode 120, wherein the external electrode 130 includes directly burned copper or silver on the dielectric layer 111 The innermost layer of the formed outer electrode is preferably implemented by sintering the copper layer 131, which is electrically connected to the end of the inner electrode 120, and the outer electrodes 130 of each two adjacent multilayer ceramic capacitors 100 pass through each other. The polymer conductive adhesive 210 is adhered and fixed in a temperature range of 150° C. to 200° C. to form a bonding interface 200 without welding.

In this embodiment, two multilayer ceramic capacitors 100 are vertically stacked up and down, and the outer electrodes 130 of each multilayer ceramic capacitor 100 are adhered and fixed to each other by a polymer conductive adhesive 210 to form a bonding interface 200. The whole The structure is a stack of multiple multilayer ceramic capacitors 100. The method of stacking is to first apply the polymer conductive adhesive 210 to the outer electrode 130 of the first multilayer ceramic capacitor 100 or the upper surface of the burned copper layer 131, and Continue to press the outer electrode 130 of the second multilayer ceramic capacitor 100 or the lower surface of the burned copper layer 131 on the polymer conductive adhesive 210, and at the same time make the outer electrode 130 or the lower surface of the second multilayer ceramic capacitor 100 The burned copper layer 131 corresponds to the outer electrode 130 of the second multilayer ceramic capacitor 100 or the burned copper layer 131 at the same position and stacked on top of it, and then performs low-temperature operation within the temperature range of about 150~200℃ Without welding, after curing the polymer conductive adhesive 210, each two adjacent external electrodes 130 can be adhered and fixed to form a bonding interface 200 with supporting strength and as a conductive channel for two adjacent external electrodes 130, so that two The multilayer ceramic capacitor 100 can be electrically conductive and form a series combination, and its total capacitance value is higher than that of a single multilayer ceramic capacitor 100, and because the capacitor stack structure does not require high-temperature heating and sintering to form a bond, except In addition to the fewer variation factors in the manufacturing process, the damage to the capacitor body can also be minimized. Therefore, the following descriptions in this case are all explained together, and they are all explained.

In the present invention, the outer electrodes 130 of a plurality of multilayer ceramic capacitors 100 are changed to use the polymer conductive adhesive 210 as the bonding material, and after curing, the bonding interface 200 can be formed to provide support strength and conductive channels, and the polymer conductive adhesive 210 The composition includes 75%~85% metal powder and 15%~25% viscose, wherein the metal powder is selected from any group consisting of silver (Ag), copper (Cu) and nickel (Ni), The adhesive uses polymer resin and has special viscous strength. The better specification is the polymer conductive adhesive of H926 commercially available product specifications, such as resin silver glue. It can also be based on polymer (generally also called (Polymer) resin type, fluidity or conductivity, etc., adjust the appropriate ratio, or adjust the appropriate ratio according to different types of multilayer ceramic capacitors 100 specifications and the number of stacks, for example, the polymer resin can contain 75 %~85% of the metal powder does not affect the purpose of the present invention, but it is not limited to this. Graphene can also be added to the polymer resin, and the different compositions of the metal powder, graphene and polymer resin can be further adjusted. The ratio makes the polymer conductive adhesive 210 more excellent in conductivity. Because the adhesive interface 200 formed by the resin silver glue has the strong and tough characteristics of polymer materials, it can provide sufficient support for the capacitor stack structure after the resin is cured. Adhesive strength, and the polymer component contained in the resin can give the toughness required to absorb the bending or vibration energy of the board, and it can effectively resist the mechanical damage caused by the repeated bending of the board or the vibration environment.

In addition, the number of multilayer ceramic capacitors 100 that can be stacked in the above-mentioned capacitor stack structure is not fixed, and two or more multilayer ceramic capacitors can be stacked according to the specifications (such as volume and weight) of different types of multilayer ceramic capacitors 100, which is better. The implementation is between two to four, and the bonding interface 200 can still provide sufficient support strength without collapsing, and the bonding interface 20 0 The composition of the polymer conductive adhesive 210 used can be adjusted to a suitable ratio according to the different multilayer ceramic capacitors 100 and the number of stacks, and in order to make the metal powder more uniformly and finely dispersed in the polymer resin to produce more For a stable conductive channel, the selected metal powder particle size can also be between 0.3 and 5.0 μm; in addition, when the number of stacked capacitors is greater, the closer to the bottom of the multilayer ceramic capacitor 100, the greater the load, in order to avoid high The molecular (generally referred to as polymer) resin collapses during the curing process. The higher the weight-bearing polymer resin, the higher the viscosity coefficient, or the higher the strength of the adhesive interface 200 after curing, to form It can bear the supporting force of multiple multilayer ceramic capacitors 100.

As shown in Figure 4, in this embodiment, the external electrodes 130 of the stacked ceramic capacitors 100 are applied with a polymer conductive adhesive 210 to adhere and cure to form the bonding interface 200. The electroplating process is performed to form the first plating layer 221 and the second plating layer 222 of the electroplating strengthening layer 220 by nickel plating and tin plating. Since the polymer conductive adhesive 210 contains 75% to 85% of sufficient metal powder, it can be combined with The electroplating solution reacts to form a uniform and detailed electroplating surface, so that any micro cracks or micro gaps on the interface 200 will be filled by the electroplating strengthening layer 220 after electroplating to avoid the formation of crack nuclei, but it is not limited to this. It is also possible to coextensively form the flat side surface of the electroplating strengthening layer 220 on each bonding interface 200 and the outer electrode 130 of the multilayer ceramic capacitor 100, and the electroplating strengthening layer 220 can completely cover the outer electrodes 130 of the multilayer ceramic capacitor 100, thereby Strengthen the mechanical strength of the bonding interface 200, or enable each external electrode 130 at one end of a plurality of multilayer ceramic capacitors 100 to be covered by the same continuous and uninterrupted surface electroplating strengthening layer 220, so as to achieve simultaneous The special external terminal electrodes with the effect of multiple ceramic capacitors in series can also be covered by the electroplating strengthening layer 220 to cover multiple stacks on top and bottom, and use the polymer conductive adhesive 210 to form the adhesive interface 200. The outer electrode 130 of the multilayer ceramic capacitor 100. This kind of leadless stacked ceramic capacitor can remove the use of metal leads, and the TLPS paste as a bonding material requires high temperature heating and sintering and many process restrictions. In addition to simplifying the process, the polymer conductive adhesive 210 has no soldering operation. The curing temperature is relatively low, so that the variation factors of the manufacturing process are relatively reduced, so as to achieve the purpose of improving the product yield and reducing the cost.

Please refer to Figures 5~6, which can be learned from the data sheet of the side push experiment of the leadless stacked ceramic capacitor (without Lead Frame) of the present invention and the conventional multilayer ceramic capacitor stack (with Lead Frame) as a comparison group , The average lateral thrust (AVG) measured by the comparison group is about 166.7N. f, the range of the minimum (MIN) and maximum (MAX) lateral thrust is between 120~180N. Between f, it is the mechanical strength level of the multilayer ceramic capacitors with Lead Frame on the market.

Specifically, even if the leadless stacked ceramic capacitors of the experimental group of the present invention remove the metal leads (without Lead Frame), the actual measured average lateral thrust (AVG) is about 165.228N. f, the range of the minimum (MIN) and maximum (MAX) lateral thrust is between 133.28~176.4N. Between f, the overall lateral push strength value performance is not inferior to multilayer ceramic capacitors with metal leads, but the production process is far more simplified than the above comparison group, even if metal leads and circuit boards are not used for surface mounting ( SMT) operation can still have the toughness required to absorb plate bending or vibration energy, and will not cause unpredictable stress damage to the stacking position of the multilayer ceramic capacitor 100 or the interface 200, and it can effectively resist the repeated plate bending or vibration environment. The mechanical damage caused.

The above detailed description is only for a preferred and feasible embodiment of the present invention, but the embodiment is not intended to limit the scope of the patent application of the present invention, unless otherwise deviated from the present invention. All equal changes and modifications made under the spirit of the technique disclosed in the Ming Dynasty shall be included in the scope of patents covered by the present invention.

In summary, the leadless stacked ceramic capacitor of the present invention can indeed achieve its efficacy and purpose when used. Therefore, the present invention is truly an invention with excellent practicability. The review committee granted this case as soon as possible to protect the inventor’s hard work. If the review committee has any doubts, please feel free to write instructions. The inventor will do his best to cooperate.

100: Multilayer ceramic capacitor

110: Capacitor body

111: Dielectric layer

120: inner electrode

130: External electrode

131: Burning copper layer

200: then interface

210: Polymer conductive adhesive

Claims (12)

A leadless stacked ceramic capacitor includes: a plurality of stacked multilayer ceramic capacitors in a direction perpendicular to each other. The terminal parts are respectively exposed on the two ends of the capacitor body, and the two ends of the capacitor body are respectively provided with external electrodes that are electrically connected to the internal electrode ends; and the external electrodes of the multilayer ceramic capacitors pass a height between each other Molecular conductive adhesive is a bonding interface formed by curing without soldering, and the polymer conductive adhesive contains 75%-85% of metal powder and 15%-25% of adhesive. A leadless stacked ceramic capacitor includes: a plurality of stacked multilayer ceramic capacitors, and a plurality of internal electrodes interlaced with each other are inserted into the capacitor main body of the multilayer ceramic capacitors, so that the ends of the internal electrodes are respectively inserted The two ends of the capacitor body are exposed, and the two ends of the capacitor body are respectively provided with external electrodes that are electrically connected to the internal electrode ends; wherein the external electrodes include a plurality of burned copper layers and electroplating strengthening layers, and the electroplating The strengthening layer is located outside the outer electrodes and covers the burnt copper layers, and the burnt copper layers are respectively located inside the outer electrodes and cover the ends of the inner electrodes; wherein the burnt copper layers The layers are connected to each other through the polymer conductive adhesive, and the polymer conductive adhesive contains 75%-85% of metal powder and 15%-25% of the adhesive. The leadless stacked ceramic capacitor according to claim 1 or 2, wherein a plurality of dielectric layers are stacked in the capacitor body of the multilayer ceramic capacitor, and the internal electrodes are interspersed between the dielectric layers. The leadless stacked ceramic capacitor according to claim 1 or 2, wherein the polymer conductive adhesive is operated at a low temperature in the temperature range of 150°C to 200°C without soldering, and the multilayer ceramic capacitors are each two Adjacent external electrodes are adhered and fixed to form the bonding interface for providing support strength and conductive channels. The leadless stacked ceramic capacitor according to claim 1 or 2, wherein the metal powder of the polymer conductive adhesive is any one selected from the group consisting of silver, copper and nickel. The leadless stacked ceramic capacitor according to claim 5, wherein the particle size of the metal powder is between 0.3 and 5.0 μm. The leadless stacked ceramic capacitor according to claim 1 or 2, wherein a polymer resin is used for the adhesive of the polymer conductive adhesive. The leadless stacked ceramic capacitor according to claim 7, wherein the polymer resin further contains graphene. The leadless stacked ceramic capacitor according to claim 1 or 2, wherein the multilayer ceramic capacitors are respectively formed with electroplating strengthening layers outside the bonding interface of the external electrode stacking position between each other. The leadless stacked ceramic capacitor according to claim 9, wherein the electroplating strengthening layer is formed on the outside of the bonding interfaces, and the first plating layer and the second plating layer are sequentially formed by electroplating. The leadless stacked ceramic capacitor according to claim 10, wherein the first plating layer and the second plating layer are nickel plating and tin plating, respectively. The leadless stacked ceramic capacitor according to claim 9, wherein the plating strengthening layer is a continuous uninterrupted surface and is located outside each of one end of the multilayer ceramic capacitors

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