Inverted MEMS force sensor chip

Abstract

The utility model discloses an inverted MEMS force sensor chip which is characterized in that the inverted MEMS force sensor chip comprises a stress layer, a sensitive film and a supporting frame, and the two opposite faces of the stress layer and the sensitive film are connected with the upper surface and the lower surface of the supporting frame; at least one force transmission column is arranged in a containing space formed among the stress layer, the sensitive film and the supporting frame, and the at least one force transmission column is connected with the two opposite faces of the sensitive film and the stress layer. The chip is fixed, the electric signal leading-out surface is separated from the stress surface, and the reliability of the device is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of MEMS chip structures, in particular to a flip-chip MEMS force sensor chip. Background Art

[0002] However, with the in-depth and rapid development of MEMS technology research, as well as the diversity and complexity of MEMS devices themselves, MEMS packaging still faces many new problems that need to be solved, such as stress release in device packaging, standardization of packaging and interfaces, and reliability and reliability evaluation of packaging performance.

[0003] In order to protect the electrical signal lead wires from being damaged, traditional upright MEMS force sensor chips usually place force-sensitive resistors and metal pads on the front of the chip. This will result in the height of the electrical signal lead wires being higher than the force-bearing surface of the MEMS force sensor when the electrical signals of the MEMS chip are brought out by wire bonding. In order to protect the metal leads, it is necessary to bond a layer of bosses higher than the metal leads to the force-bearing surface of the MEMS force sensor to extend the force-bearing surface, which leads to a sharp increase in the difficulty of the process. Utility Model Content

[0004] In view of the above problems, the purpose of the present invention is to provide a flip-chip MEMS force sensor chip to solve the problems existing in the prior art.

[0005] According to one aspect of the utility model, a flip-chip MEMS force sensor chip is provided, which includes a force-bearing layer, a sensitive film and a support frame, wherein the two opposite surfaces of the force-bearing layer and the sensitive film are connected to the upper and lower surfaces of the support frame; at least one force transmission column is arranged in the accommodating space formed between the force-bearing layer, the sensitive film and the support frame, and the at least one force transmission column is connected to the opposite surfaces of the sensitive film and the force-bearing layer.

[0006] In some embodiments, at least one through hole is provided on the surrounding surfaces of the support frame that are not connected to the stress-bearing layer and the sensitive film.

[0007] In some embodiments, at least one limiting column is arranged in the accommodating space, the lower end of the at least one limiting column is connected to the surface of the sensitive film facing the stress-bearing layer, and there is a gap between the upper end of the at least one limiting column and the surface of the stress-bearing layer facing the sensitive film.

[0008] In some embodiments, the at least one limiting column is located around the at least one force transfer column.

[0009] In some embodiments, the at least one force transfer column is located around the at least one limiting column.

[0010] In some embodiments, at least one force-sensitive resistor is disposed on the surface of the sensitive film facing away from the force-bearing layer.

[0011] In some embodiments, a heavily doped region and at least one metal lead are provided on the surface of the sensitive film facing away from the stress-bearing layer, the at least one force-sensitive resistor is connected to the heavily doped region, and the heavily doped region is connected to the at least one metal lead.

[0012] In some embodiments, a metal pad is disposed on the surface of the sensitive film facing away from the stress-bearing layer, and the at least one metal lead is coupled to the metal pad.

[0013] In some embodiments, at least one solder ball is disposed on the surface of the sensitive film facing away from the stress-bearing layer, and the at least one solder ball is located at four vertices and / or a center position on the surface of the sensitive film facing away from the stress-bearing layer.

[0014] In some embodiments, a PCB board is provided on the surface of the sensitive film on which the metal pad is provided, and the at least one solder ball is connected to the metal pad, and the at least one solder ball is connected to the surface of the PCB board facing the sensitive film.

[0015] In the inverted MEMS force sensor chip provided by the utility model, the force applied to the force-bearing surface is transmitted to the sensitive film through the force transmission column, and the force on the upper surface of the force-bearing surface is led to the back side, so as to realize the separation of the sensitive film and the force-bearing surface. At the same time, a limit column is designed to control the deformation of the force-bearing layer to improve the overload resistance of the device. The chip surface pad is electrically connected to the bottom PCB board by implanting solder balls and flip-chip welding. At the same time, the solder balls provide fixed support for the chip and space for the sensitive film to move. The purpose of the utility model is to realize the fixation of the chip and the separation of the electrical signal lead-out surface and the force-bearing surface, thereby improving the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments are briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present application, but are not intended to limit the present application, wherein:

[0017] Figure 1 A cross-sectional view of a flip-chip MEMS force sensor chip provided according to the first embodiment of the utility model;

[0018] Figure 2 A top view of a flip-chip MEMS force sensor chip with a force-bearing layer hidden according to the first embodiment of the utility model;

[0019] Figure 3 A cross-sectional view of a sensitive film of a flip-chip MEMS force sensor chip provided according to an embodiment of the utility model;

[0020] Figure 4 A bottom view of a flip-chip MEMS force sensor chip provided with solder balls according to an embodiment of the utility model;

[0021] Figure 5 A cross-sectional view of a flip-chip MEMS force sensor chip connected to a PCB according to a first embodiment of the utility model;

[0022] Figure 6 A typical assembly diagram of a flip-chip MEMS force sensor chip connected to a PCB according to the first embodiment of the utility model;

[0023] Figure 7 A cross-sectional view of a flip-chip MEMS force sensor chip with a through hole provided in a support frame according to a second embodiment of the present utility model;

[0024] Figure 8 A typical assembly diagram of a flip-chip MEMS force sensor chip provided in a support frame with through holes to hide the force-bearing layer according to the second embodiment of the utility model;

[0025] Fig. 9 It is a cross-sectional view of a flip-chip MEMS force sensor chip in which the limiting pillars are located around the force transmission pillars according to an embodiment of the utility model;

[0026] Fig.10 The bottom view of another flip-chip MEMS force sensor chip provided with solder balls according to an embodiment of the utility model. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] In the drawings, the shapes and dimensions may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like components.

[0029] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons of ordinary skill in the field to which this application belongs. The words "first", "second" and similar words used in the patent application specification and claims of this application do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one", "one" or "the" do not indicate a quantitative limitation, but indicate the existence of at least one. Words such as "include" or "comprise" and similar words mean that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalents, and do not exclude other elements or objects. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] In the following description, words such as center, thickness, height, length, front, back, rear, left, right, top, bottom, upper, lower, etc. are defined relative to the structure shown in the drawings. In particular, "height" is equivalent to the dimension from top to bottom, "width" is equivalent to the dimension from left to right, and "depth" is equivalent to the dimension from front to back. They are relative concepts and may change accordingly according to their different positions and different usage states. Therefore, these or other directions should not be interpreted as restrictive terms.

[0031] Terms related to attachment, coupling, and the like (eg, "connected" and "attached") refer to either a fixed or attached relationship between structures, either directly or indirectly, and either movable or rigid attachments or relationships, unless expressly stated otherwise, of the structures to one another through intermediate structures.

[0032] The specific implementation of the utility model is further described in detail below in conjunction with the drawings and embodiments.

[0033] Figure 1 It is a cross-sectional view of a flip-chip MEMS force sensor chip provided according to the first embodiment of the utility model.

[0034] refer to Figure 1A flip-chip MEMS force sensor chip 100 of the present application includes a stress-bearing layer 101, a force transmission column 103 and a sensitive film 105. The stress-bearing layer 101 is responsible for bearing the externally applied force. The force transmission column 103 is connected to the two opposite surfaces of the sensitive film 105 and the stress-bearing layer 101. The external force applied to the stress-bearing layer 101 is transmitted to the sensitive film 105 through the force transmission column 103. A force-sensitive resistor 105b is arranged on the sensitive film 105, which is responsible for responding to the force transmitted from the stress-bearing layer 101 to the sensitive film 105. At least one solder ball 106 is arranged at the four corners and the center of the surface of the sensitive film 105 facing away from the stress-bearing layer 101. The solder ball 106 is responsible for realizing the electrical signal connection between the sensitive film 105 and the external PCB board 200, and at the same time plays the role of fixing and supporting the sensitive film 105, and provides the sensitive film 105 with space for deformation under stress. The flip-chip MEMS force sensor chip is also provided with a support frame 104, which is a hollow structure. The opposite sides of the force-bearing layer 101 and the sensitive film 105 are connected to the upper and lower surfaces of the support frame 104, and the force transfer column 103 is arranged in the accommodating space formed by the force-bearing layer 101, the sensitive film 105 and the support frame 104. A limiting column 102 is also arranged in the accommodating space. In the direction where the sensitive film 105 is facing the stress-bearing layer 101, the lower end of the limiting column 102 is connected to the sensitive film 105, and there is a gap between the upper end of the limiting column 102 and the stress-bearing layer 101. The actual size of the gap is determined according to the film thickness, the measuring range and the operating conditions. When the external force applied to the stress-bearing layer 101 exceeds the designed measuring range and the deformation of the stress-bearing layer 101 is greater than the gap between the limiting column 102, the stress-bearing layer 101 will contact the limiting column 102, thereby limiting the deformation of the stress-bearing layer 101 and the excessive deformation of the sensitive film 105, thereby improving the stiffness of the stress-bearing layer 101 and the overload resistance of the sensitive film 105.

[0035] For example, in the embodiment of the utility model, the PCB board 200 is a support body for electronic components (such as MEMS devices and ASIC devices), and is also a carrier for the electrical connection of electronic components. For example, a copper layout design is performed on the PCB substrate to serve as a connecting wire. The substrate 1 is a circuit board based on a multi-layer copper layout design to serve as a connecting wire, for example, it can include a substrate layer, a metal layer and a solder mask layer.

[0036] The technical solution provided by the utility model aims to transfer the force applied to the stress-bearing layer 101 to the sensitive film 105 through the force transfer column 103, implant the solder ball 106 on the surface of the sensitive film 105, and electrically connect it to the bottom PCB board 200 in a flip-chip manner. At the same time, the solder ball 106 provides a fixed support for the sensitive film 105 and ensures the space for the sensitive film 105 to move, thereby fixing the sensitive film 105 and leading out the electrical signal. Such a structural design realizes the separation of the force transfer column 103 and the sensitive film 105, and at the same time, the limit column 102 limits the excessive deformation of the stress-bearing layer 101 and the sensitive film 105, thereby improving the reliability of the device.

[0037] In some embodiments, reference Figure 1 In this embodiment, the force transmission column 103, the limiting column 102 and the support frame 104 are all made of hard materials, and the hard materials can be metal, plastic, etc.

[0038] Figure 2 It is a top view of a flip-chip MEMS force sensor chip with a force-bearing layer hidden according to the first embodiment of the utility model.

[0039] In some embodiments, reference Figure 2 The force transmission pillars 103 are typically four in number, and are located between the limiting pillars 102 and the support frame 104. To ensure the force transmission effect, their specific positions are adjusted according to the chip size, the size of the support frame 104, and the deformation of the force-bearing layer 101. The force transmission pillars 103 are connected to the force-bearing layer 101 by bonding. To ensure the bonding strength between the force transmission pillars 103 and the force-bearing layer 101 and achieve stable force transmission, the support frame 104 and the force transmission pillars 103 can be connected by structures such as beams and blocks to increase the bonding area.

[0040] Figure 3 It is a cross-sectional view of a sensitive film of a flip-chip MEMS force sensor chip provided according to an embodiment of the utility model.

[0041] In some embodiments, reference Figure 3 The sensitive film 105 includes a sensitive film substrate 105a, a force-sensitive resistor 105b, a heavily doped region 105c, a metal lead 105d, and a metal pad 105e. The material of the sensitive film substrate 105a is silicon, which will deform when subjected to the force transmission column 103, and stress will be generated inside. The force-sensitive resistor 105b is formed by doping silicon, and the resistance value of the force-sensitive resistor 105b will change under the action of stress. An ohmic contact is formed between the heavily doped region 105c and the metal lead 105d, and the force-sensitive resistor 105b and the metal lead 105d are interconnected. A solder ball 106 is implanted on the surface of the metal pad 105e, and the metal pad 105e is interconnected with the metal lead 105d, and finally the electrical connection between the force-sensitive resistor 105b and the solder ball 106 is realized.

[0042] Figure 4 A bottom view of a flip-chip MEMS force sensor chip provided with solder balls according to an embodiment of the utility model; Fig. 9 It is a cross-sectional view of a flip-chip MEMS force sensor chip in which the limiting pillars are located around the force transmission pillars according to an embodiment of the utility model; Fig.10 The bottom view of another flip-chip MEMS force sensor chip provided with solder balls according to an embodiment of the utility model.

[0043] In some embodiments, reference Figure 1 and Figure 4 The force transfer column 103 is located around the limiting column 102. At this time, the limiting column 102 is located at the center of the sensitive film 105. Solder balls 106 are arranged at the four vertices and the center of the surface of the sensitive film 105 facing away from the force-bearing layer 101. The typical number of solder balls 106 is 5.

[0044] In other embodiments, reference Fig. 9 , the limit column 102 is located around the force transmission column 103. At this time, the force transmission column 103 is located at the center of the sensitive film 105. The limit column 102 is changed from the original middle limit to the surrounding limit. The limit column 102 is changed from one to four, and the force transmission column 103 is moved to the middle position. Fig.10 At this time, the solder ball 106 is no longer set at the center position of the surface of the sensitive film 105 facing away from the stress-bearing layer 101, and the solder balls 106 are only set at the four vertex positions on the surface of the sensitive film 105 facing away from the stress-bearing layer 101. The number of solder balls 106 is changed from 5 to 4, ensuring that the force transfer column 103 located at the center position of the sensitive film 105 can transfer the force from the stress-bearing layer 101 to the sensitive film 105.

[0045] Figure 5 A cross-sectional view of a flip-chip MEMS force sensor chip connected to a PCB according to a first embodiment of the utility model; Figure 6 This is a typical assembly diagram of a flip-chip MEMS force sensor chip connected to a PCB according to the first embodiment of the utility model.

[0046] In some embodiments, the flip-chip MEMS force sensor chip 100 and the PCB board 200 are welded and assembled via the solder balls 106 and the metal pads 201 to realize the extraction of electrical signals of the force sensor chip 100 .

[0047] Figure 7 A cross-sectional view of a flip-chip MEMS force sensor packaging structure with a through hole provided in a support frame according to a second embodiment of the present utility model; Figure 8This is a typical assembly diagram of a flip-chip MEMS force sensor packaging structure in which a through hole is provided in a support frame to hide the force-bearing layer according to the second embodiment of the utility model.

[0048] In other embodiments, reference Figure 7 and Figure 8 At least one through hole 107 is provided on the surrounding surfaces of the support frame 104 that are not connected to the stress-bearing layer 101 and the sensitive film 105. The through hole 107 is used to maintain the balance between the internal air pressure and the external air pressure to avoid measurement errors caused by changes in the external atmospheric pressure. Providing through holes 107 on the surrounding surfaces that are not connected to the stress-bearing layer 101 and the sensitive film 105 can avoid damaging the integrity of the bottom sensitive film 105.

[0049] Furthermore, the through hole 107 can be etched simultaneously when etching the limiting pillar 102 , or can be processed on the surrounding surfaces of the support frame 104 that are not connected to the stress-bearing layer 101 and the sensitive film 105 by machining or the like.

[0050] The embodiments of the present invention are described above, and these embodiments do not describe all the details in detail, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modifications based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flip-chip MEMS force sensor chip, characterized in that: The flip-chip MEMS force sensor chip comprises a force-bearing layer, a sensitive film and a support frame, and the two opposite surfaces of the force-bearing layer and the sensitive film are connected to the upper and lower surfaces of the support frame; At least one force transmission column is arranged in the accommodation space formed between the stress-bearing layer, the sensitive film and the support frame, and the at least one force transmission column is connected to the opposite surfaces of the sensitive film and the stress-bearing layer.

2. The MEMS force sensor chip according to claim 1, characterized in that: At least one through hole is provided on the surrounding surfaces of the support frame which are not connected to the stress-bearing layer and the sensitive film.

3. The MEMS force sensor chip according to claim 1, characterized in that: At least one limiting column is arranged in the accommodating space, the lower end of the at least one limiting column is connected to the surface of the sensitive film facing the stress-bearing layer, and there is a gap between the upper end of the at least one limiting column and the surface of the stress-bearing layer facing the sensitive film.

4. The MEMS force sensor chip according to claim 3, characterized in that: The at least one limiting column is located around the at least one force transmission column.

5. The MEMS force sensor chip according to claim 3, characterized in that: The at least one force transmission column is located around the at least one limiting column.

6. The MEMS force sensor chip according to claim 1, characterized in that: At least one force-sensitive resistor is disposed on the surface of the sensitive film facing away from the force-bearing layer.

7. The MEMS force sensor chip according to claim 6, characterized in that: A heavily doped region and at least one metal lead are provided on the surface of the sensitive film facing away from the stress-bearing layer, the at least one force-sensitive resistor is connected to the heavily doped region, and the heavily doped region is connected to the at least one metal lead.

8. The MEMS force sensor chip according to claim 7, characterized in that: A metal pad is disposed on the surface of the sensitive film facing away from the stress-bearing layer, and the at least one metal lead is coupled to the metal pad.

9. The MEMS force sensor chip according to claim 8, characterized in that: At least one solder ball is disposed on the surface of the sensitive film facing away from the stress-bearing layer, and the at least one solder ball is located at four vertices and / or a center position on the surface of the sensitive film facing away from the stress-bearing layer.

10. The MEMS force sensor chip according to claim 9, characterized in that: A PCB board is provided on the surface of the sensitive film on which the metal pad is provided, and the at least one solder ball is connected to the metal pad, and the at least one solder ball is connected to the surface of the PCB board facing the sensitive film.

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