A piezoelectric stack interdigitated electrode structure and method of forming the same

Abstract

The application provides a piezoelectric stack interdigital electrode structure and a forming method thereof, which comprises forming a first open slot on an electrode line on one side of the stack with slots being spaced apart, forming a first electrode line with the remaining electrode lines, and arranging the first electrode line and the first open slot apart from each other, and filling the first open slot with insulating glue. The technical scheme of the application has high electrode lead-out efficiency, good consistency of device electrical performance, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramic preparation technology, and more specifically, to a piezoelectric stacked interdigitated electrode structure formed by a slotting method and its formation method. Background Technology

[0002] In the 1980s, piezoelectric actuators developed rapidly as a new type of driving element for microelectromechanical systems (MEMS) and were widely used in the fields of mechanics, biomedicine, optics, and sensing both domestically and internationally.

[0003] Piezoelectric ceramic actuators utilize the inverse piezoelectric effect of piezoelectric ceramics to convert electrical energy applied to them into mechanical energy. Stacked piezoelectric ceramics are created by stacking multiple piezoelectric ceramic sheets together, with interlayers connected by a colloid. For the same total thickness, the smaller the thickness of the ceramic sheets, the more numerous they are, resulting in a greater overall displacement.

[0004] Stacked piezoelectric actuators are rigid ceramics with high output force and good controllability, making them suitable for precision driving applications. However, their production process is lengthy and involves many factors, which can lead to problems such as poor ceramic density, moisture absorption, cracks, and porosity. These issues often exacerbate the physicochemical effects of moisture and other impurities in the air on the ceramic devices, causing the devices' electrical properties to age and eventually fail.

[0005] There are various methods for leading out the internal electrodes of a piezoelectric stack. Currently, the most common method is to form interdigitated electrodes. Traditionally, a method of leaving edges during electrode printing is used, resulting in staggered positive and negative electrodes after stacking. This method has several problems: if the edges are too narrow, the device is prone to breakdown under an electric field, requiring high stacking neatness; if the edges are too wide, the device size is large but the usable effective area is small, resulting in poor economic efficiency. Furthermore, devices fabricated using this method have poor electrical performance consistency and reliability. In the fabrication of piezoelectric stacks, the method of leading out the internal electrodes directly affects whether the device's electrical performance meets the application requirements and is a key factor affecting device reliability. Summary of the Invention

[0006] In view of the problems in the prior art, the purpose of this invention is to provide a simple and easy-to-implement piezoelectric stacked interdigital electrode structure and its formation method.

[0007] According to one aspect of the present invention, a piezoelectric stacked interdigital electrode structure is provided, comprising at least three stacked piezoelectric ceramic sheets, with electrodes distributed between adjacent piezoelectric ceramic sheets, and a plurality of first electrode lines and a plurality of first opening slots provided on one side of the piezoelectric stack, wherein the first electrode lines are located between adjacent piezoelectric ceramic sheets, the first opening slots are located between adjacent piezoelectric ceramic sheets, the first electrode lines and the first opening slots are spaced apart from each other, and insulating adhesive is provided in the first opening slots.

[0008] Preferably, the other side of the piezoelectric stack is provided with a plurality of second electrode lines and a plurality of second opening slots, the second electrode lines are located between two adjacent piezoelectric ceramic sheets, the second opening slots are located between two adjacent piezoelectric ceramic sheets, the second electrode lines and the second opening slots are spaced apart from each other, and the second opening slots are provided with insulating adhesive.

[0009] Preferably, the first electrode line on one side of the piezoelectric stack corresponds to the second opening slot on the other side, and the first opening slot on one side of the piezoelectric stack corresponds to the second electrode line on the other side.

[0010] Preferably, the depth and width of the first opening groove are the same as the depth and width of the second opening groove.

[0011] Preferably, the depth of the first opening groove and the second opening groove is 0.3 to 0.7 mm, and the width of the groove is 0.2 to 0.5 mm.

[0012] Preferably, the insulating adhesive is an epoxy resin adhesive.

[0013] Preferably, the thickness of the piezoelectric ceramic sheet is 0.7 to 0.9 mm.

[0014] According to another aspect of the present invention, a method for forming the above-described piezoelectric stacked interdigital electrode structure is provided, comprising the following steps:

[0015] Step 1: Stack at least three piezoelectric ceramic sheets together to form a stack, with electrodes distributed between two adjacent piezoelectric ceramic sheets, and electrode lines formed between two adjacent piezoelectric ceramic sheets on the side of the stack.

[0016] Step 2: Spacing is made on the electrode wires on one side of the stack to form the first opening slot, and the remaining electrode wires form the first electrode wires;

[0017] Step 3: Fill the first opening groove with insulating glue.

[0018] Preferably, step 2 further includes: forming a second opening groove by slotting at intervals on the electrode lines on the other side of the stack, and forming a second electrode line with the remaining electrode lines; the second opening groove corresponds to the first electrode line, and the second electrode line corresponds to the first opening groove.

[0019] Step 3 also includes filling the second opening groove with insulating adhesive.

[0020] Preferably, the thickness of the grooving blade in step 2 is 0.1 to 0.4 mm.

[0021] Compared with existing technologies, the piezoelectric stacked tank obtained by the present invention, after being sealed with potting compound, forms an interdigitated electrode structure by connecting the remaining electrode lines on opposite sides of the stack. The resulting stacked device is reliable and robust, the internal electrodes are easy to extract, and the electrical performance parameters of the device are highly consistent. In addition, the method in the present invention is simple, easy to implement, and widely applicable. Attached Figure Description

[0022] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic diagram of one side of the piezoelectric stack structure in Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram of the piezoelectric stack structure with a slot on one side according to Embodiment 3 of the present invention;

[0025] Figure 3 This is a schematic diagram of the piezoelectric stack structure with staggered slots on opposite sides in Embodiment 3 of the present invention;

[0026] Figure 4 This is a schematic diagram of the piezoelectric stack structure after slotting on both sides and filling with epoxy resin according to Embodiment 1 of the present invention. Detailed Implementation

[0027] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0028] In an embodiment of the invention, a piezoelectric stacked interdigitated electrode structure includes at least three stacked piezoelectric ceramic sheets, with electrodes distributed between adjacent piezoelectric ceramic sheets. That is, by stacking multiple piezoelectric ceramic sheets and connecting them with a colloid, a stacked piezoelectric ceramic (also known as a piezoelectric stack) is fabricated.

[0029] On one side of the piezoelectric stack, that is, on one side of the piezoelectric stack, there are several first electrode lines and several first opening slots. The first electrode lines are located between two adjacent piezoelectric ceramic sheets, and the first opening slots are located between two adjacent piezoelectric ceramic sheets. The first electrode lines and first opening slots are arranged alternately, and insulating adhesive is provided in the first opening slots. That is, the first opening slots replace the original electrode lines, forming alternately spaced first electrode lines and first opening slots on one side of the piezoelectric stack. In this way, spaced electrode lines can be formed on one side of the piezoelectric stack.

[0030] The first slot replaces the original electrode wire, blocking the electrode connection at this point. The increased spacing between the first electrode wires results in a larger safe working distance under the electric field. Each electrode wire of both the positive and negative electrodes is clearly visible. Any unconnected electrode wires can be directly observed and resolved promptly, demonstrating high electrode extraction efficiency. Therefore, embodiments of the present invention readily yield devices with good electrical performance consistency, significantly enhancing the reliability of the device during use.

[0031] In an embodiment of the invention, preferably, a plurality of second electrode lines and a plurality of second opening slots are provided on the other side of the piezoelectric stack, that is, on the side opposite to one side. The second electrode lines are located between two adjacent piezoelectric ceramic sheets, and the second opening slots are located between two adjacent piezoelectric ceramic sheets. The second electrode lines and the second opening slots are spaced apart from each other, and insulating adhesive is provided in the second opening slots.

[0032] Preferably, the first electrode line on one side of the piezoelectric stack corresponds to the second opening slot on the other side, and the first opening slot on one side of the piezoelectric stack corresponds to the second electrode line on the other side, thus forming a symmetrical two-sided staggered slot structure. The electrode lines are staggered and spaced on the two opposite sides of the piezoelectric stack, and the electrodes on both sides are connected to form an interdigitated electrode structure.

[0033] The positive and negative electrodes are led out from two sides of the stack, respectively, without interfering with each other. For example, it is preferable to lead out the first electrode line from one side of the piezoelectric stack and connect them together as the positive electrode, and lead out the second electrode line from the other side of the piezoelectric stack and connect them together as the negative electrode. The interdigitated electrode structure formed by the staggered slotting method results in a reliable and robust stacked device with easy-to-lead-out internal electrodes and good consistency of device electrical performance parameters.

[0034] In an embodiment of the present invention, the method for forming a piezoelectric stacked interdigital electrode structure includes the following steps:

[0035] Step 1: Stack at least three piezoelectric ceramic sheets together to form a stack, with electrodes distributed between two adjacent piezoelectric ceramic sheets, and electrode lines formed between two adjacent piezoelectric ceramic sheets on the side of the stack.

[0036] The preferred electrode is a silver electrode, and the electrode wire is a silver electrode wire.

[0037] Step 2: Spacing is made on the electrode wires on one side of the stack to form the first opening slot, and the remaining electrode wires form the first electrode wires;

[0038] Step 3: Fill the first opening groove with insulating glue.

[0039] Preferably, a groove is first cut on the silver electrode line on the first side of the piezoelectric stack.

[0040] The first face is located on one side of the piezoelectric stack.

[0041] The first groove is cut at intervals of one silver electrode line.

[0042] In an embodiment of the present invention, depending on the size of the piezoelectric ceramic stack, the groove depth is preferably 0.3 to 0.7 mm and the groove width is 0.2 to 0.5 mm.

[0043] After slotting, potting compound is filled into the slot to achieve insulation. Therefore, the slot must have a certain depth and width. However, while removing the silver electrode, slotting also removes a small portion of the ceramic sheet in the piezoelectric stack. Removing too much ceramic can weaken the overall robustness of the piezoelectric stack (tensile strength under an electric field). Therefore, the depth and width of the slot should not be too large. If the slot depth and width are too small, it is difficult to pot the insulating compound, which can easily lead to insufficient density after the compound cures. Insufficient compound usage also means a decrease in the breakdown strength under an electric field, resulting in reduced device reliability.

[0044] Due to the limited thickness of the ceramic sheets that make up the stack, it is preferable to control the thickness of the removed ceramic sheets to within 20% of the thickness of the ceramic sheets. Since the groove is located on the silver electrode line at the junction of the two ceramic sheets, it is preferable that the width of the groove is less than 40% of the sum of the thicknesses of the two piezoelectric ceramic sheets.

[0045] For example, if the thickness of a single ceramic sheet is 0.9 mm, the groove width is preferably 0.3 mm. After grooving, the thickness of each ceramic sheet is reduced by about 0.15 mm, resulting in a smaller area of ​​ceramic damage, which is feasible relative to the 0.9 mm thickness of the ceramic sheet.

[0046] Furthermore, it is preferable to use a dicing machine for grooving, and it is preferable that the thickness of the blade used for dicing is 0.1 to 0.4 mm.

[0047] The blade thickness determines the grooving width. With a blade thickness of 0.1mm, if the actual grooving width is greater than 0.1mm after cutting, this is due to edge chipping within the acceptable range for ceramics or blade vibration during the cutting process causing insufficient cutting depth. Therefore, for grooving widths ranging from 0.2 to 0.5mm, a blade thickness of 0.1 to 0.4mm is optimal.

[0048] Water is preferred as the grooving coolant for the dicing machine.

[0049] During the operation of internal and external diameter cutting machines, the blade speed typically ranges from several thousand to 30,000 rpm. Sparks are continuously generated at the contact points of the ceramic blades during cutting, producing a significant amount of instantaneous heat, necessitating continuous cooling with coolant. While cooling oil or oil-water mixtures offer good cooling, cleaning the ceramic and residual oily coolant in the groove after cutting is difficult. Residual oil directly reduces device reliability. Therefore, with proper control of the coolant flow rate, water is the preferred coolant.

[0050] The preferred grooving speed of the dicing machine is 1-3 mm / s.

[0051] The grooving rate, or the speed at which the blade advances along the ceramic silver electrode wire during cutting, is related to the hardness of the ceramic sample. Higher ceramic hardness necessitates a matching cutting rate to minimize blade wear or damage. Excessive cutting speed can cause the groove width to exceed the acceptable range, compromising cutting accuracy. Conversely, lower cutting speeds significantly reduce efficiency. Furthermore, lower cutting rates often lead to ceramic chipping, resulting in uneven groove edges, noticeable burrs, and substantial ceramic damage. Additionally, lower speeds mean the blade spends a relatively long time at the same position on the ceramic, increasing the risk of microcracks within the ceramic and reducing stack reliability. Experiments have shown that a suitable grooving rate for the piezoelectric stack in this embodiment of the invention is 1–3 mm / s.

[0052] After the first groove is cut, it is preferable to cut a groove on the silver electrode line on the opposite side of the piezoelectric stack.

[0053] The slots on the other side are also staggered. For example, if one side has slots on odd-numbered silver electrode lines (1st, 3rd, 5th...), then the opposite side has slots on even-numbered silver electrode lines (2nd, 4th, 6th...). The slot depth and width are preferably the same. This staggered slotting on opposite sides forms the basis for the interdigitated electrode structure.

[0054] After grooving is completed on both sides, insulating adhesive is poured into the open grooves on both sides of the stack and preferably heated and cured.

[0055] The preferred potting insulating adhesive is epoxy resin, with a curing temperature of 100-130℃ and a curing time of 1-3 hours.

[0056] Encapsulating the grooves with insulating adhesive provides insulation and prevents breakdown of the stacked devices when operating under an electric field. Generally, epoxy resin adhesives offer relatively high insulation, moisture resistance, and voltage breakdown strength. The curing temperature and time depend on the curing parameters of the epoxy adhesive. Furthermore, the curing temperature of the adhesive should be significantly lower than the Curie temperature of the ceramic to prevent depolarization of the ceramic portion at higher temperatures. However, room-temperature curing adhesives are not recommended, as they typically exhibit lower strength after curing, and parameters such as hardness and tensile strength do not meet the application requirements. Therefore, epoxy resin adhesives with a curing temperature of 100–130℃ are preferred for potting.

[0057] In addition, in this embodiment of the invention, the thickness of a single ceramic sheet constituting the piezoelectric stack is preferably 0.7 to 0.9 mm.

[0058] Example 1

[0059] like Figure 1 As shown, the dimensions of the piezoelectric ceramic stack are 5mm×5mm×38mm, and the thickness of each individual ceramic sheet that makes up the stack is 0.9mm.

[0060] like Figure 4 As shown, grooving is performed on two symmetrical sides of a 5mm × 38mm stack using a dicing machine. The coolant is water, the grooving rate is 3mm / s, the blade thickness is 0.2mm, the groove depth is 0.7mm, and the groove width is 0.3mm.

[0061] After stacking, grooving, and cleaning, epoxy resin is poured in and cured. The curing temperature is 110℃, and the curing time is 2.5 hours.

[0062] Example 2

[0063] The dimensions of the piezoelectric ceramic stack are 5mm×5mm×38mm, and the thickness of each individual ceramic sheet that makes up the stack is 0.9mm.

[0064] Grooves were cut on two symmetrical sides of a 5mm×38mm stack using a dicing machine. Water was used as the coolant. The grooving speed was 2mm / s. The blade thickness was 0.4mm, the groove depth was 0.5mm, and the groove width was 0.5mm.

[0065] After stacking, grooving, and cleaning, epoxy resin is poured in and cured. The curing temperature is 130℃, and the curing time is 2 hours.

[0066] Example 3

[0067] like Figure 2 and 3 As shown, the dimensions of the piezoelectric ceramic stack are 10mm×10mm×52mm, and the thickness of each individual ceramic sheet that makes up the stack is 0.7mm.

[0068] like Figure 3As shown, grooving was performed on two symmetrical sides of a 10mm × 52mm stack using a dicing machine, with water as the coolant. The grooving rate was 2mm / s, the blade thickness was 0.2mm, the groove depth was 0.4mm, and the groove width was 0.3mm.

[0069] After stacking, grooving, and cleaning, epoxy resin is poured in and cured. The curing temperature is 100℃, and the curing time is 3 hours.

[0070] Example 4

[0071] The dimensions of the piezoelectric ceramic stack are 10mm×10mm×52mm, and the thickness of each individual ceramic sheet that makes up the stack is 0.7mm.

[0072] Grooves were cut on two symmetrical sides of a 10mm×52mm stack using a dicing machine. Water was used as the coolant. The grooving speed was 1mm / s. The blade thickness was 0.2mm, the groove depth was 0.3mm, and the groove width was 0.3mm.

[0073] After stacking, grooving, and cleaning, epoxy resin is poured in and cured. The curing temperature is 110℃, and the curing time is 2 hours.

[0074] In summary, the piezoelectric stack obtained by the embodiments of the present invention has high internal electrode extraction efficiency, good consistency of device electrical performance, and strong reliability.

[0075] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A piezoelectric stacked interdigital electrode structure, characterized in that, The device comprises at least three stacked piezoelectric ceramic sheets, with electrodes distributed between adjacent piezoelectric ceramic sheets. One side of the piezoelectric stack has a plurality of first electrode lines and a plurality of first opening slots, with the first electrode lines and first opening slots located between adjacent piezoelectric ceramic sheets. The first electrode lines and first opening slots are spaced apart from each other, and insulating adhesive is provided in the first opening slots. The other side of the piezoelectric stack has a plurality of second electrode lines and a plurality of second opening slots, with the second electrode lines and second opening slots located between adjacent piezoelectric ceramic sheets. The second electrode lines and second opening slots are spaced apart from each other, and insulating adhesive is provided in the second opening slots. The first electrode lines on one side of the piezoelectric stack correspond to the second opening slots on the other side, and vice versa.

2. The piezoelectric stacked interdigital electrode structure according to claim 1, characterized in that: The depth and width of the first opening groove are the same as those of the second opening groove.

3. The piezoelectric stacked interdigital electrode structure according to claim 2, characterized in that: The depth of the first and second opening grooves is 0.3 to 0.7 mm, and the width of the grooves is 0.2 to 0.5 mm.

4. The piezoelectric stacked interdigital electrode structure according to claim 1, characterized in that: The insulating adhesive is epoxy resin adhesive.

5. The piezoelectric stacked interdigital electrode structure according to claim 1, characterized in that: The thickness of the piezoelectric ceramic sheet is 0.7–0.9 mm.

6. The method for forming a piezoelectric stacked interdigital electrode structure according to claim 1, characterized in that: Includes the following steps: Step 1: Stack at least three piezoelectric ceramic sheets together to form a stack, with electrodes distributed between two adjacent piezoelectric ceramic sheets, and electrode lines formed between two adjacent piezoelectric ceramic sheets on the side of the stack. Step 2: Spacing is made on the electrode wires on one side of the stack to form the first opening slot, and the remaining electrode wires form the first electrode wires; Step 3: Fill the first opening groove with insulating glue.

7. The method for forming a piezoelectric stacked interdigital electrode structure according to claim 6, characterized in that: Step 2 further includes: creating a second opening groove by slotting at intervals on the electrode lines on the other side of the stack, and forming a second electrode line with the remaining electrode lines; the second opening groove corresponds to the first electrode line, and the second electrode line corresponds to the first opening groove. Step 3 also includes filling the second opening groove with insulating adhesive.

8. The method for forming a piezoelectric stacked interdigital electrode structure according to claim 7, characterized in that: In step 2, the thickness of the cutting blade used for grooving is 0.1 to 0.4 mm.

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