阅读说明：本技术 集成于pcb上的压电致动微驱动器的制备方法 (Method for preparing piezoelectric actuating micro driver integrated on PCB ) 是由 王令 王文斌 李涛 邹光南 于 2020-11-23 设计创作，主要内容包括：本发明涉及微流体机械技术领域,具体是集成于PCB上的压电致动微驱动器的制备方法,所述制备方法包括对PCB泵体进行清洗,去除泵体上的杂质；对泵体的上下表面进行图形化处理；在泵体上刻蚀有沉孔,并将该沉孔的底部进行截切打磨,形成泵腔；从泵腔的截切面向下刻蚀有两个通孔,分别作为进液口和出液口；再次对开凿后的泵体进行清洗,并保持干燥；在位于泵腔外沿的泵体表面固定有一层圆环形焊盘；在圆盘形焊盘上方焊接有相应的圆盘形压电单晶执行器；将压电单晶执行器的负极与系统电源地相连,将压电陶瓷表面通过导线引出与系统电源正极相连。本发明所制备的压电致动微驱动器经过PCB电装工艺焊接而成,构成的腔室与流道密封性好。(The invention relates to the technical field of microfluid machinery, in particular to a preparation method of a piezoelectric actuating micro-driver integrated on a PCB (printed Circuit Board), which comprises the steps of cleaning a PCB pump body and removing impurities on the pump body; carrying out graphical processing on the upper surface and the lower surface of the pump body; etching a counter bore on the pump body, and cutting and polishing the bottom of the counter bore to form a pump cavity; two through holes are etched downwards from the truncation surface of the pump cavity and respectively used as a liquid inlet and a liquid outlet; cleaning the cut pump body again and keeping the pump body dry; a layer of annular bonding pad is fixed on the surface of the pump body positioned on the outer edge of the pump cavity; a corresponding disc-shaped piezoelectric single crystal actuator is welded above the disc-shaped bonding pad; the cathode of the piezoelectric single crystal actuator is connected with a system power ground, and the surface of the piezoelectric ceramic is led out through a lead to be connected with the anode of the system power. The piezoelectric actuating micro-driver prepared by the invention is formed by welding through a PCB (printed circuit board) electric fitting process, and the formed cavity has good sealing performance with a flow channel.)

1. A method for preparing a piezoelectric actuating micro-driver integrated on a PCB is characterized in that: the preparation method comprises the following steps:

cleaning the PCB pump body to remove impurities on the PCB pump body;

carrying out graphical processing on the upper surface and the lower surface of the PCB pump body, and forming a mask pattern of the counter bore and a mask pattern of the through hole;

etching a counter bore on the PCB pump body according to the mask pattern of the counter bore, and cutting and polishing the bottom of the counter bore to form a pump cavity;

according to the mask pattern of the through holes, two through holes are etched downwards from the truncated surface of the pump cavity and are respectively used as a liquid inlet and a liquid outlet;

cleaning the cut PCB pump body again to remove impurities on the PCB pump body and keeping the PCB pump body dry;

a layer of disc-shaped bonding pad is fixed on the surface of the PCB pump body positioned on the outer edge of the pump cavity;

a disc-shaped piezoelectric single crystal actuator with a corresponding size is welded above the disc-shaped bonding pad;

the cathode of the piezoelectric single crystal actuator is connected with a system power ground, and the surface of the piezoelectric ceramic is led out through a lead to be connected with the anode of the system power.

2. The method for manufacturing a piezoelectric actuating micro-driver integrated on a PCB of claim 1, wherein: the step of carrying out graphical processing on the upper surface and the lower surface of the PCB pump body and forming a mask pattern of a counter bore and a mask pattern of a through hole comprises the following steps:

coating photoresist on the upper surface and the lower surface of the PCB pump body;

and photoetching the photoresist, etching a mask pattern of the counter bore on the upper surface, and etching a mask pattern of the through hole on the lower surface.

3. The method for manufacturing a piezoelectric actuating micro-driver integrated on a PCB of claim 1, wherein: the disc-shaped piezoelectric single crystal actuator welded above the disc-shaped bonding pad and having a corresponding size comprises:

cutting a copper substrate with the size consistent with that of the disc-shaped bonding pad;

fixing the copper substrate by adopting a clamp, and heating the surface of the copper substrate by laser radiation;

welding the copper substrate on the disc-shaped bonding pad in a laser spot welding mode by controlling laser pulse parameters, and releasing welding stress by a loading method;

plating silver electrode slurry on the surface of the piezoelectric ceramic, and sintering at high temperature;

and connecting the copper substrate and the sintered piezoelectric ceramic in a welding mode.

Technical Field

The invention relates to the technical field of microfluid machinery, in particular to a piezoelectric actuating micro-driver integrated on a PCB (printed Circuit Board) and a preparation method thereof.

Background

The micro driver is used as a power part of the low-orbit satellite microfluidic system, and plays a role in controlling the flow and the flow direction of fluid in a micro channel, so that the capability of controlling the performance of a propulsion system and a liquid cooling system is achieved.

At present, the drive mode of the micro-fluidic system generally adopts an external micro-driver to drive, needs the power line of the external micro-driver and a pipeline for conveying coolant, so that the integration level of the whole system is lower, and the pipeline has larger pressure loss, so that the drive force and the control capability of the micro-driver are reduced, and the micro-fluidic system cannot be applied to the low-orbit satellite micro-fluidic system. In order to solve these problems, researchers at home and abroad mainly study the driving mode, the processing technology and the structural design of the micro-actuator. The driving method of the micro-actuator is classified into a piezoelectric driving method, an electrostatic driving method, an electromagnetic driving method, a thermopneumatic driving method, and the like. The piezoelectric actuating micro-driver based on the inverse piezoelectric effect not only has the capability of driving liquid by taking microliter as a unit, but also has the advantages of simple structure, large driving force and weak electromagnetic interference, and is suitable for realizing integration with other parts of a microfluidic system. Some researchers have started to research the micro actuator manufacturing process to reduce the volume of the micro actuator, which is divided into silicon processing technology, glass and quartz processing, and high polymer processing. Although the volume of the micro-actuator formed by silicon and high molecular polymer is smaller than that of a micro-actuator processed by metal, a liquid cooling system still needs to be provided with a pipeline and is difficult to integrate with other parts of a microfluidic system, and the problems of weak control capability and low integration level of the micro-actuator are not solved. The chinese patent application 200810069378.1 discloses a micro-actuator with active precise control capability, which can achieve very low flow and very high control precision, but does not discuss the processing technology and integration method of the micro-actuator.

So far, there is an effective solution for how to integrate the micro-actuator with other microfluidic components, and the micro-actuator still has the problems of poor control capability and low integration degree in the system. Chinese patent application 2019111079950 proposes a piezoelectric actuated fluid pump integrated on a PCB; the structure adopts a pumping unit and at least two piezoelectric actuating fluid pumps, and a plurality of piezoelectric single crystal actuators are arranged above the pumping unit, so that the structure is complex and the integration level is very low.

The patent with application number 202010044191.7 provided by the unit successfully solves the problem of integration level, and the piezoelectric actuating micro-driver comprises a PCB pump body and a piezoelectric single crystal actuator, wherein the PCB pump body is processed by PCB, the piezoelectric single crystal actuator comprises piezoelectric ceramics and a copper substrate, and the piezoelectric ceramics are bonded above the copper substrate; the PCB pump body is provided with a counter bore downwards in the middle, the copper substrate welding is in on the PCB pump body, the counter bore of the PCB pump body with the copper substrate constitutes the pump chamber, the PCB pump body has inlet and liquid outlet, inlet and liquid outlet with the pump chamber intercommunication, the lower bottom surface slope of pump chamber sets up, the inlet is highly higher than the liquid outlet in vertical side.

However, the application does not discuss the processing technology and integration method of the piezoelectric actuating micro-driver, it is unclear how the micro-driver is prepared, and when preparing the piezoelectric single crystal actuator, the copper substrate and the epoxy glue are required to be adhered by using the epoxy glue; the difference between the thermal expansion coefficients of the copper substrate and the epoxy glue is large, and the thermal expansion coefficient of the epoxy glue is 54 multiplied by 10^{- 6}in/in/° C, the coefficient of thermal expansion of the copper substrate is 17.5 x 10^-6in/in/° C; the deformation difference of the two is large under the condition of higher temperature, and certain deformation stress can be generated; the deflection of the integral piezoelectric single crystal actuator is influenced; is not beneficial to pumping in and out of the fluid.

Disclosure of Invention

The invention aims to provide a preparation method of a piezoelectric actuating micro-driver integrated on a PCB (printed circuit board), which can reduce the difficulty of integrating the piezoelectric actuating micro-driver with other parts of a micro-fluidic system, so that the micro-driver directly acts on a micro-channel, and the control capability of the micro-driver and the integration degree of the system are improved.

Specifically, the technical scheme adopted by the invention comprises a preparation method of the piezoelectric actuating micro-driver integrated on the PCB.

In a first aspect of the present invention, the present invention provides a method for manufacturing a piezoelectric actuating micro-driver integrated on a PCB, the method comprising:

cleaning the PCB pump body to remove impurities on the PCB pump body;

carrying out graphical processing on the upper surface and the lower surface of the PCB pump body, and forming a mask pattern of the counter bore and a mask pattern of the through hole;

etching a counter bore on the PCB pump body according to the mask pattern of the counter bore, and cutting and polishing the bottom of the counter bore to form a pump cavity;

according to the mask pattern of the through holes, two through holes are etched downwards from the truncated surface of the pump cavity and are respectively used as a liquid inlet and a liquid outlet;

cleaning the cut PCB pump body again to remove impurities on the PCB pump body and keeping the PCB pump body dry;

a layer of annular bonding pad is fixed on the surface of the PCB pump body positioned on the outer edge of the pump cavity;

a disc-shaped piezoelectric single crystal actuator with a corresponding size is welded above the disc-shaped bonding pad;

the cathode of the piezoelectric single crystal actuator is connected with a system power ground, and the surface of the piezoelectric ceramic is led out through a lead to be connected with the anode of the system power.

Further, the step of performing patterning processing on the upper surface and the lower surface of the PCB pump body and forming a mask pattern of the counterbore and a mask pattern of the through hole includes:

coating photoresist on the upper surface and the lower surface of the PCB pump body;

and photoetching the photoresist, etching a mask pattern of the counter bore on the upper surface, and etching a mask pattern of the through hole on the lower surface.

The invention has the following advantages:

1. the preparation method of the piezoelectric actuating micro-driver provided by the invention can easily obtain the micro-driver meeting the conditions without preparing the micro-driver by a complex chemical method;

2. the piezoelectric actuating micro-driver prepared by the invention is welded by a PCB (printed circuit board) electric fitting process, the formed cavity has good sealing property with a flow channel, an electronic element is not in direct contact with liquid, and the problem of electronic element failure caused by liquid leakage is solved;

3. the piezoelectric actuating micro-driver prepared by the invention has the advantages that the surface of the piezoelectric ceramic is plated with a metal layer; through the intervention of the middle metal layer, the high-temperature deformation stress caused by the epoxy adhesive is solved, the connection temperature and pressure can be reduced, and meanwhile, the effect of restraining and changing a joint product can be achieved.

Drawings

FIG. 1 is a flow chart of a method for fabricating a PCB integrated piezo-actuated micro-actuator of the present invention;

FIG. 2 is a flow chart of a method of making a mask according to the present invention;

fig. 3 is a flow chart of a method for welding a disc-shaped piezoelectric single crystal actuator according to the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 shows a control method of a piezo-actuated micro-driver integrated on a PCB, the control method comprising:

101. cleaning the PCB pump body to remove impurities on the PCB pump body;

firstly, selecting a PCB processing plate with proper thickness, and forming a PCB pump body after processing the PCB processing plate; the PCB pump body is cleaned mainly for removing impurities on the surface of the PCB pump body, a semi-water cleaning mode of an organic solvent and deionized water is mainly adopted in the embodiment, and a certain amount of cleaning agent consisting of an active agent and an additive is added in the process to clean the PCB; after removing impurities on the surface of the PCB, the PCB pump body needs to be dried to keep dry.

102. Carrying out graphical processing on the upper surface and the lower surface of the PCB pump body, and forming a mask pattern of the counter bore and a mask pattern of the through hole;

as for the process of forming the mask, as shown in fig. 2, the process includes the following:

201. coating photoresist on the upper surface and the lower surface of the PCB pump body, pre-baking the photoresist, exposing the photoresist by adopting electron beam irradiation, and developing the exposed photoresist;

202. and photoetching the developed photoresist, etching a mask pattern of the counter bore on the upper surface, and etching a mask pattern of the through hole on the lower surface.

In the embodiment, on the basis of providing the PCB pump body, the upper surface and the lower surface of the PCB pump body are both provided with the mask material layers; patterning the mask material layer; forming a pattern area and a shielding area adjacent to the pattern area, forming at least one through hole penetrating through the mask material layer in the pattern area, and taking the rest of the patterned mask material layer as a mask pattern layer for a subsequent process; of course, in the present invention, two through holes are required to be formed as the liquid inlet and outlet.

103. Etching a counter bore on the PCB pump body according to the mask pattern of the counter bore, and cutting and polishing the bottom of the counter bore to form a pump cavity;

etching a counter bore on the PCB pump body according to the mask pattern of the counter bore in a corrosion mode, wherein the counter bore is much larger than the through hole and is used as a liquid storage device in a subsequent PCB pump body; the invention adopts a dry-wet combination method to corrode the PCB pump body, and polishes the bottom of the counter bore according to the mask pattern.

104. According to the mask pattern of the through holes, two through holes are dug and etched downwards from the truncation surface of the pump cavity and are respectively used as a liquid inlet and a liquid outlet;

similar to the previous embodiment, the embodiment also uses the dry-wet combination method to etch the PCB pump body, and continues to etch the bottom of the pump cavity according to the mask pattern of the through hole.

105. Cleaning the cut PCB pump body again to remove impurities on the PCB pump body and keeping the PCB pump body dry;

the embodiment adopts the ultrasonic cleaning machine for cleaning, the ultrasonic cleaning machine generates cavitation effect by utilizing the action of converting ultrahigh frequency into kinetic energy in a liquid medium, countless micro-bubbles are formed, and then the cavitation effect impacts the surface of an object to enable dirt on the surface to fall off, so that the cleaning effect is achieved. The time for washing was set to 15 minutes.

106. A layer of disc-shaped bonding pad is fixed on the surface of the PCB pump body positioned on the outer edge of the pump cavity;

the disc-shaped bonding pad is widely used in regularly arranged single-sided and double-sided printed boards, and the disc-shaped bonding pad in the invention can be a part of a PCB pump body directly or a part designed independently; in this embodiment, in order to facilitate subsequent welding, the disc-shaped bonding pad and the PCB pump body in the present invention are an integral structure, and the surface of the integral structure is a flat structure.

107. A disc-shaped piezoelectric single crystal actuator with a corresponding size is welded above the disc-shaped bonding pad;

the structure of the piezoelectric ceramic and the copper substrate of the piezoelectric single crystal actuator is utilized to form a stable solid supporting edge structure on the copper layer, the tin layer and the pad layer.

In a preferred embodiment, in order to reduce the stress effect between the epoxy glue and the copper substrate, the connection mode of the copper substrate and the piezoelectric ceramic is improved, as shown in fig. 3, the invention provides the following improvement modes:

701. cutting a copper substrate with the size consistent with that of the disc-shaped bonding pad;

in this embodiment, in order to secure the copper substrate to the copper substrate, the copper substrate may be slightly smaller than the land, but larger than the piezoelectric ceramic.

702. Fixing the copper substrate by adopting a clamp, and heating the surface of the copper substrate by laser radiation;

the surface of the workpiece is heated through laser radiation, surface heat is diffused inwards through heat conduction, and most of stress can be released as far as possible.

703. Welding the copper substrate on the disc-shaped bonding pad in a laser spot welding mode by controlling laser pulse parameters, and releasing welding stress by a loading method;

in the embodiment, parameters such as the width, the energy, the peak power and the repetition frequency of the laser pulse are controlled to melt the workpiece to form a specific molten pool. The laser beam is guided by the flexible optical fiber and then projected onto the weld by the welding head. The laser welding belongs to non-contact welding, the operation process does not need pressurization, and inactive protective gas can be used for preventing molten pool oxidation.

704. Plating silver electrode slurry on the surface of the piezoelectric ceramic, and sintering at high temperature;

in the embodiment, the silver electrode paste can be used, and can form good coupling with the piezoelectric ceramic, so that the contact resistance in the piezoelectric ceramic is small, and in addition, the silver electrode paste can be sintered for 30min at about 800 ℃ in an inert gas atmosphere.

705. And connecting the copper substrate and the sintered piezoelectric ceramic in a welding mode.

After the treatment, the high-temperature deformation stress caused between the epoxy glue and the metal layer is avoided, and the bonding joint is easy to generate larger residual stress due to the difference between the thermal expansion coefficient and the elastic modulus of the piezoelectric ceramic and the metal, so that the performance of the joint is reduced, and the performance of the piezoelectric ceramic is changed by adopting a metal film plated intermediate layer mode. Due to the intervention of the middle layer, the residual stress of the joint can be relieved, the connection temperature and pressure can be reduced, and the effect of inhibiting and changing joint products can be achieved.

At the moment, the copper substrate and the sintered piezoelectric ceramic can be directly welded and fixed by the method, so that a solid supporting edge structure of a bonding pad, a tin layer, a copper layer, a tin layer and a silver coating layer is formed; because the tin layer and the silver coating both have conductivity and the ductility of the silver coating is very good, the piezoelectric actuating micro-driver prepared by the invention not only has larger deformation, but also is well connected with the electrode; but also can inhibit the deformation stress caused by different materials and enhance the deflection characteristic of the piezoelectric single crystal actuator; the pumping efficiency of the pump body is improved.

108. The cathode of the piezoelectric single crystal actuator is connected with a system power ground, and the surface of the piezoelectric ceramic is led out through a lead to be connected with the anode of the system power.

Because the surface of the piezoelectric single crystal actuator is plated with the silver layer, the invention can directly lead out the lead from the silver layer without recoating the conductive adhesive to lead out the lead.

The invention realizes the self-injection, pumping in and pumping out of the fluid by driving the ordered action of the disc-shaped piezoelectric single crystal actuator to provide periodic signals. Fluid flows into the pump cavity through the liquid inlet and finally flows out of the liquid outlet, and flows in the PCB all the time without directly contacting with the electronic element, so that the problem of failure of the electronic element caused by liquid leakage is solved.

It can be understood that, in the present invention, the corresponding features of the piezoelectric actuating microdriver integrated on the PCB and the preparation and control methods thereof can be cited mutually, and the present invention is not described in detail.

In the description of the present invention, it is to be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "other end", "upper", "one side", "top", "inner", "outer", "front", "center", "both ends", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "disposed," "connected," "fixed," "rotated," and the like are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; the terms may be directly connected or indirectly connected through an intermediate, and may be communication between two elements or interaction relationship between two elements, unless otherwise specifically limited, and the specific meaning of the terms in the present invention will be understood by those skilled in the art according to specific situations.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.