CN113184797A

CN113184797A - Sensor packaging structure

Info

Publication number: CN113184797A
Application number: CN202110612904.XA
Authority: CN
Inventors: 缪建民; 张金姣; 王刚
Original assignee: Maigan Microelectronics Shanghai Co ltd
Current assignee: Sv Senstech Wuxi Co ltd
Priority date: 2021-06-02
Filing date: 2021-06-02
Publication date: 2021-07-30

Abstract

The invention discloses a sensor packaging structure, comprising: a MEMS chip and an ASIC chip, the MEMS chip and the ASIC chip are mounted on the same PCB board, the PCB board has a blind hole, and the MEMS chip is located in the blind hole , and the ASIC chip adopts a flip-chip method, a part is located on the upper surface of the PCB board, and the other part is located on the MEMS chip, and the MEMS chip and the flip-chip ASIC chip are directly connected by solder balls. The electrical interconnection between the ASIC chip and the MEMS chip is directly connected by solder balls, without gold wire bonding, which reduces the cost of raw materials, improves the reliability of the connection, reduces the size of the device, and improves production efficiency.

Description

Sensor packaging structure

Technical Field

The embodiment of the invention relates to the technical field of sensor packaging, in particular to a sensor packaging structure.

Background

At present, the MEMS sensor packaging mode generally realizes electrical connection through gold wire bonding. The gold wire bonding process is a bottleneck process in the traditional chip on board (chip on board) packaging, and because the gold wire is used, the packaging material cost is higher; some products even have dozens of gold wires bonded on each chip, so that the equipment is limited by the output Per Hour (Unit Per Hour, UPH), and the process efficiency is low; and gold wires with millimeter-scale length are needed to be connected between the bonding pads, which is a hidden danger for reliability.

Disclosure of Invention

The invention provides a sensor packaging structure, which is used for realizing the electrical interconnection between an ASIC chip and an MEMS chip, namely, the ASIC chip and the MEMS chip are directly connected by welding through a tin ball without adopting gold wire bonding, thereby reducing the cost of raw materials, improving the reliability, reducing the volume of a device and improving the production efficiency.

In order to achieve the above object, the present invention provides a sensor package structure, including:

the MEMS chip is positioned below the ASIC chip, and the MEMS chip is directly connected with the ASIC chip through solder balls. Wherein, the MEMS chip includes the vibrating membrane of 0.5 ~ 1um thickness, the ASIC chip is flip-chip ASIC chip.

Specifically, the top surface of the MEMS chip is provided with a first bonding pad, the top surface of the ASIC chip is provided with a second bonding pad, the ASIC chip is mounted and attached in an inverted mode, and the first bonding pad is directly connected with the second bonding pad through a first solder ball.

Specifically, the sensor package structure further includes: the PCB board, the PCB board is provided with the blind hole, the MEMS chip sets up in the blind hole, the ASIC chip adopts the mode of flip-chip, and partly be located on the upper surface of PCB board, another part is located MEMS chip's higher authority.

Specifically, a first through hole is formed in the PCB, a third bonding pad is arranged on the top surface of the ASIC chip, a fourth bonding pad is arranged on the upper surface of the PCB above the first through hole, and the third bonding pad and the fourth bonding pad are directly connected through a second solder ball, wherein the ASIC chip is mounted and attached in an inverted manner; and a fifth bonding pad is connected to the bottom of the PCB below the first through hole, and the fifth bonding pad is connected with a circuit of the PCB.

Specifically, the top surface of the MEMS chip is as flush as possible with the top surface of the blind hole.

Specifically, the vertical projection of the ASIC chip on the PCB board covers the vertical projection of the MEMS chip on the PCB board entirely.

Specifically, the sensor package structure further includes: the edge of the metal shell is connected with the edge of the PCB, the metal shell is provided with a first opening, and the vertical projection of the first opening on the PCB is in the vertical projection of the ASIC chip on the PCB.

Specifically, the bottom of the blind hole is provided with a second opening, and the vertical projection of the second opening on the PCB is in the vertical projection of the MEMS chip on the PCB.

Specifically, the MEMS chip with the thickness of 0.5-1 um is bonded in the blind hole.

Specifically, the first through hole is filled with a conductive metal.

According to the sensor package structure provided by the invention, the sensor package structure comprises: the MEMS chip with 0.5 ~ 1um thickness vibrating diaphragm and make the ASIC chip behind the metal bump, the MEMS chip is located with the below of the ASIC chip of flip-chip mode dress subsides, MEMS chip and flip-chip the pad between the ASIC chip passes through tin ball lug connection. Therefore, the direct welding connection between the ASIC chip and the MEMS chip is realized through the tin ball, the gold wire bonding mode is not needed to connect the electric signals of the two chips, the raw material cost is reduced, the connection reliability is improved, the device volume is reduced, and the production efficiency is improved.

Drawings

Fig. 1 is a schematic structural diagram of a sensor package structure according to an embodiment of the present invention;

FIG. 2 is an enlarged schematic view of portion A of FIG. 1;

fig. 3 is a schematic structural diagram of a sensor package structure according to an embodiment of the present invention;

FIG. 4 is an enlarged schematic view of portion B of FIG. 3;

FIG. 5 is a schematic structural diagram of a sensor package structure according to another embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a sensor package structure according to yet another embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a sensor package structure according to yet another embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a sensor package structure according to another embodiment of the present invention;

FIG. 9 is a schematic structural diagram of a sensor package structure according to yet another embodiment of the present invention;

FIG. 10 is a schematic structural diagram of a sensor package structure according to yet another embodiment of the present invention;

FIG. 11 is a schematic structural diagram of a sensor package structure according to another embodiment of the present invention;

fig. 12 is a flowchart illustrating an ASIC chip in a sensor package structure according to an embodiment of the present invention to dispose metal bumps.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 1 is a schematic structural diagram of a sensor package structure according to an embodiment of the present invention. As shown in fig. 1, the sensor package structure 100 includes:

MEMS chip 101 and ASIC chip 102, wherein, MEMS chip 101 includes 0.5 ~ 1um thick vibrating membrane 120 and backplate 121, MEMS chip 101 is located ASIC chip 102's below, MEMS chip 101 with through the tin ball direct connection between the ASIC chip 102.

The ASIC chip 102 is mounted in an inverted manner after RDL (rewiring is performed in advance, and the contact positions of the originally designed chip circuit are changed by a wafer-level metal wiring process and a bump process, so that the chip can be applied to different packaging forms), bump soldering, solder ball planting and other processes (RDL, bump soldering, solder ball planting and other processes are bump processes) are completed.

As shown in fig. 12, a pad 130 is provided on the ASIC chip 102, and a copper pillar 132 and a solder 133 are provided through a passivation layer 134 and a photoresist 131, and finally a metal bump is formed on the ASIC chip 102.

Specifically, fig. 2 is an enlarged schematic view of a portion a in fig. 1. As shown in fig. 1 and 2, a first pad 104 is disposed on a top surface of the MEMS chip 101, a second pad 105 is disposed on a top surface of the ASIC chip 102, wherein the ASIC chip 102 is mounted in an inverted manner, the first pad 104 and the second pad 105 are directly connected through a first solder ball 103, the ASIC chip 102 and the MEMS chip 101 cannot touch a vibrating membrane when being soldered, and the first solder ball 103 is a metal bump made in bump process. Therefore, the use of gold wires between the ASIC chip 102 and the MEMS chip 101 is avoided, the raw material cost is reduced, the connection reliability is improved, and the device volume is reduced.

The MEMS (micro-electro mechanical system) chip 101 is a micro-electromechanical system, and may be a capacitive sensor. The device consists of a vibrating film with the thickness of only 0.5-1 um and a back plate, and is used for detecting sound or micro-flow airflow. An asic (application specific integrated circuit) chip 102 is an application specific integrated circuit. The MEMS chip 101 is used to detect an external signal, transmit the detection result to the ASIC chip 102, process the signal by the ASIC chip 102, and transmit the processed signal to other electrical components.

Specifically, fig. 3 is a schematic structural diagram of a sensor package structure according to an embodiment of the present invention. As shown in fig. 3, the sensor package structure 100 further includes: the PCB 106 is provided with a blind hole 1061, the MEMS chip 101 is arranged in the blind hole 1061, and the ASIC chip 102 is flipped, one part of which is located on the upper surface of the PCB 106, and the other part of which is located above the MEMS chip 102. .

The ASIC chip 102 is above the MEMS chip 101, and the ASIC chip 102 partially overlaps the MEMS chip 101, such that the second bonding pad 105 of the ASIC chip 102 after flip-mounting is exactly aligned with the first bonding pad 104 of the MEMS chip 101, and further, a first solder ball 103 may be disposed between the first bonding pad 104 and the second bonding pad 105, such that the ASIC chip 102 and the MEMS chip 101 are electrically connected, such that gold wire bonding is not required between the ASIC chip 102 and the MEMS chip 101, thereby reducing the cost of raw materials and improving the connection reliability.

By providing blind holes 1061 in the PCB 106, placing the MEMS chip 101 in the blind holes 1061, and placing the ASIC chip 102 on the upper surface of the PCB 106, the thickness of the entire sensor package 100 is reduced in a direction perpendicular to the ASIC chip 102 along the PCB 106, and the MEMS chip partially overlaps the ASIC chip 102, which reduces the width of the entire sensor package 100.

Specifically, as shown in fig. 3, the top surface of the MEMS chip 101 is flush with the top surface of the blind via 1061. That is, the depth of the blind hole 1061 is as same as the height of the MEMS chip 101 as possible, so that the flatness of the ASIC chip 101 is ensured, and the distance between the MEMS chip 101 and the ASIC chip 102 is shortened, so that the distance between the second pad 105 of the ASIC chip 102 and the first pad 104 of the MEMS chip 101 is shortest, thereby improving the reliability. Wherein, the distance between the top surface of the MEMS chip 101 and the top surface of the blind hole 1061 is between-20 um and 20 um.

Specifically, the MEMS chip 101 is bonded within the blind hole 1061. That is, the lower end of the MEMS chip 101 is bonded within the blind hole 1061, wherein the MEMS chip 101 can be bonded within the blind hole 1061 by glue. The glue may be silica gel. The MEMS chip 101 is then fixed within the blind hole 1061.

Specifically, fig. 4 is an enlarged schematic view of a portion B in fig. 3. As shown in fig. 3 and 4, a first through hole 1063 is formed in the PCB 106, a third pad 107 is formed on the top surface of the ASIC chip 102, a fourth pad 108 is formed on the upper surface of the PCB 106 above the first through hole 1063, and the third pad 107 and the fourth pad 108 are directly connected through a second solder ball 109; the ASIC chip is mounted in a flip-chip manner, a fifth pad 110 is connected to the bottom of the PCB 106 below the first through hole 1063, and the fifth pad 110 is connected to a circuit of the PCB 106.

Specifically, the first via 1063 is filled with a conductive metal.

The third pad 107 on the ASIC chip 102 and the fourth pad 108 on the upper surface of the PCB 106 are directly connected through the second solder ball 109, the first through hole 1063 is disposed in the PCB 106, the first through hole 1063 is aligned with the fourth pad 108, and the first through hole 1063 is filled with a conductive metal, so that a signal processed by the ASIC chip 102 can be transmitted to an external component, because the fifth pad 110 is connected to the lower side of the first through hole 1063, and the fifth pad 110 is connected to the circuit of the PCB 106, further, an electrical signal in the circuit of the PCB 106 can be transmitted to the ASIC chip 102 through the first through hole 1063, and the first through hole 1063 is a bridge for the ASIC chip 102 to communicate with an external component. Similarly, the ASIC chip 102 and the PCB 106 are directly connected by the second solder ball 109, which avoids connecting a gold wire between the ASIC chip 102 and the PCB 106, saves the cost of raw materials, and reduces the thickness of the whole sensor package structure 100. Since the first through hole 1063 is directly formed in the PCB 106, a gold wire is also prevented from being bonded between the ASIC chip 102 and the circuit in the PCB 102, i.e., a gold wire does not need to be bonded around the outside of the PCB 106, thereby further reducing the thickness and width of the entire sensor package structure 100.

Specifically, fig. 5 is a schematic structural diagram of a sensor package structure according to another embodiment of the present invention. As shown in fig. 5, the vertical projection of the ASIC chip 102 on the PCB board 106 entirely covers the vertical projection of the MEMS chip 101 on the PCB board 106.

That is, in a direction in which the ASIC chip 102 is directed perpendicularly to the PCB board 106, the perpendicular projection of the MEMS chip 101 on the PCB board 106 is within the perpendicular projection of the ASIC chip 102 on the PCB board 106, thus further reducing the width of the entire sensor package 100.

Specifically, fig. 6 is a schematic structural diagram of a sensor package structure according to yet another embodiment of the present invention. Fig. 7 is a schematic structural diagram of a sensor package structure according to still another embodiment of the invention. As shown in fig. 6 and 7, the sensor package structure 100 further includes: a metal shell 111, an edge of the metal shell 111 is connected to an edge of the PCB 106, the metal shell 111 is provided with a first opening 112, and a vertical projection of the first opening 112 on the PCB 106 is within a vertical projection of the ASIC chip 102 on the PCB 106.

Wherein a vertical projection of the first opening 112 on the PCB 106 is within a vertical projection of the ASIC chip 102 on the PCB 106. That is, the first opening 112 is provided only above the ASIC chip 102, avoiding being provided above the MEMS chip 101, and dust or the like is prevented from falling from the first opening 112 onto the MEMS chip 101, so that the MEMS chip detection sensitivity is lowered. The edge of the metal shell 111 may be bonded (or welded) to the edge of the PCB 106 by glue, the metal shell 111 is provided with a first opening 112, and the sensor package 100 may be applied to a silicon microphone product (front sound structure), that is, a MEMS acoustic sensor package.

The metal shell 111 has a sound inlet (first opening 112) and is sealed at other positions to form a front cavity and a back cavity. These two cavity structures are necessary for the microphone to work. The working principle is as follows: when sound is emitted from the outside, a sound pressure signal is sensed by a high-sensitivity vibrating film with the thickness of 0.5-1 um in the MEMS chip 101 through a sound inlet hole, so that the distance between the vibrating film in the MEMS chip 101 and a back plate in the MEMS chip 101 is changed, and accordingly capacitance change is formed. The MEMS chip 101 is connected to a CMOS amplifier in the ASIC chip 102 to convert capacitance change into a change of a voltage signal, and then the change is amplified and output.

Specifically, fig. 8 is a schematic structural diagram of a sensor package structure according to another embodiment of the present invention. Fig. 9 is a schematic structural diagram of a sensor package structure according to yet another embodiment of the present invention. As shown in fig. 8 and 9, the bottom of the blind hole 1061 is provided with a second opening 113, and a vertical projection of the second opening 113 on the PCB 106 is within a vertical projection of the MEMS chip 101 on the PCB 106.

That is, the second opening 113 is disposed at the bottom of the blind hole 1061 in the PCB 106, wherein no opening is disposed on the metal shell 111, and the sensor package 100 can be applied to a silicon microphone product (rear sound structure), that is, a MEMS acoustic sensor package.

By providing the second opening 113, the other locations are sealed, forming a front chamber and a back chamber. These two cavity structures are necessary for the microphone to work. The working principle is as follows: when sound is emitted from the outside, a sound pressure signal is sensed by a high-sensitivity vibrating film with the thickness of 0.5-1 um in the MEMS chip 101 through a sound inlet hole, so that the distance between the vibrating film in the MEMS chip 101 and a back plate in the MEMS chip 101 is changed, and accordingly capacitance change is formed. The MEMS chip 101 is connected to a CMOS amplifier in the ASIC chip 102 to convert capacitance change into a change of a voltage signal, and then the change is amplified and output. Fig. 10 is a schematic structural diagram of a sensor package structure according to still another embodiment of the invention. Fig. 11 is a schematic structural diagram of a sensor package structure according to another embodiment of the present invention. As shown in fig. 10 and 11, a first opening 112 is formed in the metal shell 111, a second opening 113 is formed at the bottom of the blind hole 1061, and the sensor package structure 100 is applied to an electronic cigarette sensor, that is, a MEMS micro-flow airflow sensor package structure. An air flow path is formed by providing an air hole in each of the PCB 106 and the metal case 111.

The working principle is as follows: in a smoking state, airflow enters the sensor cavity from the smoke gun to the air inlet hole (the first opening 112) of the metal shell 111, the vibrating diaphragm of the built-in MEMS chip 101 deforms to generate capacitance change, and the capacitance change is output to the ASIC chip 102 to be processed and converted into a control signal, so that the atomizer is directly driven. When the smoking state is small in air flow, the deformation quantity of the vibrating diaphragm of the MEMS chip 101 is small, the variation quantity of the output capacitance is small, and the atomization power converted by the ASIC chip 102 is low and the smoke output is small; similarly, when the cigarette is smoked, the air flow is large, and the cigarette output is large.

Specifically, this sensor packaging structure 100 need not to adopt the gold thread bonding, reduces raw and other materials cost, need not the routing, improves and connects the reliability, and thickness is thinner after the encapsulation, reduces one gold thread bonding process, reduces the processing cost, and the space of gold thread bonding on the former PCB board alright saves, reduces product space occupation rate, satisfies customer's miniaturized demand.

Specifically, the manufacturing method of the sensor package structure 100 includes steps of making welding bumps on a wafer of the ASIC chip 102, cutting the wafer into single chips after the solder balls are implanted, then attaching the MEMS chip 101 to the blind hole 1061 in the PCB 106, and fixing the MEMS chip with glue, wherein the ASIC chip 102 is attached by a flip chip process, the solder balls are respectively overlapped with the solder pads of the MEMS chip 101 and the PCB 106, reflow soldering is performed on the PCB 106 having the attached chips, reflow soldering is performed on the metal shell 111 by mounting the surface mount device by using SMT, and finally cutting the product.

The thickness of the high-sensitivity vibration film in the MEMS chip 101 is between 0.5 and 1um, and after the MEMS chip is manufactured, the film is damaged by any action on the film, so that processes such as RDL (radio description language) or ball planting cannot be performed on the MEMS chip, only processes such as RDL and welding salient points can be performed on a wafer of the ASIC chip 102, and after the processes such as tin ball planting are completed, the high-sensitivity vibration film is connected with a bonding pad on the MEMS chip 101 through reflow soldering, and the vibration film on the MEMS chip cannot be damaged due to no touch on the vibration film on the MEMS chip in the process. In addition, the lower end of the MEMS chip 101 and the PCB 106 are fixed by glue and are in a closed state, so that the air sealing of the acoustic cavity is ensured.

In summary, the sensor package structure provided by the present invention includes: MEMS chip and ASIC chip, wherein, the MEMS chip includes the thick vibrating membrane of 0.5 ~ 1um, and wherein, the ASIC chip is with the flip-chip mode dress subsides, the MEMS chip is located make the below of the ASIC chip behind the metal bump technology, the MEMS chip with the flip-chip through tin ball lug connection between the ASIC chip. Therefore, the direct welding connection between the ASIC chip and the MEMS chip is realized through the tin ball without gold wire bonding, thereby reducing the cost of raw materials, improving the reliability and the production efficiency and reducing the volume of devices.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A sensor package structure, comprising:

MEMS chip and ASIC chip, the MEMS chip is located the below of ASIC chip, the MEMS chip with through tin ball lug connection between the ASIC chip, wherein, the MEMS chip includes the thick vibrating membrane of 0.5 ~ 1um, the ASIC chip is flip-chip ASIC chip.

2. The sensor package structure of claim 1, wherein the top surface of the MEMS chip is provided with first pads and the top surface of the ASIC chip is provided with second pads, wherein the ASIC chip is flip-chip mounted and the first pads and the second pads are directly connected by first solder balls.

3. The sensor package structure of claim 2, further comprising: the PCB board, the PCB board is provided with the blind hole, the MEMS chip sets up in the blind hole, the ASIC chip adopts the mode of flip-chip, and partly be located on the upper surface of PCB board, another part is located MEMS chip's higher authority.

4. The sensor package structure of claim 3, wherein a first through hole is formed in the PCB, a third bonding pad is formed on the top surface of the ASIC chip, a fourth bonding pad is formed on the upper surface of the PCB above the first through hole, and the third bonding pad and the fourth bonding pad are directly connected through a second solder ball, wherein the ASIC chip is mounted in a flip-chip manner; and a fifth bonding pad is connected to the bottom of the PCB below the first through hole, and the fifth bonding pad is connected with a circuit of the PCB.

5. The sensor package structure of claim 3, wherein a top surface of the MEMS chip is as flush as possible with a top surface of the blind via.

6. The sensor package structure of claim 3, wherein a vertical projection of the ASIC chip on the PCB board entirely covers a vertical projection of the MEMS chip on the PCB board.

7. The sensor package structure of claim 3, further comprising: the edge of the metal shell is connected with the edge of the PCB, the metal shell is provided with a first opening, and the vertical projection of the first opening on the PCB is in the vertical projection of the ASIC chip on the PCB.

8. The sensor package structure according to claim 3 or 7, wherein the bottom of the blind hole is provided with a second opening, and a perpendicular projection of the second opening on the PCB is within a perpendicular projection of the MEMS chip on the PCB.

9. The sensor package structure of claim 3, wherein the MEMS chip having a vibrating membrane with a thickness of 0.5-1 um is bonded in the blind hole.

10. The sensor package structure of claim 4, wherein the first via is filled with a conductive metal.