TW201606947A - Electric connection structure between front and back surfaces of chip and manufacturing method thereof - Google Patents

Abstract

The present invention provides an electric connection structure between front and back surfaces of chip and manufacturing method thereof, which comprises a chip and a flexible printed circuit (FPC). The front surface of the chip is configured with multiple die pads and at least one active area, such as fingerprint recognition sensor active area. The flexible printed circuit has a first surface and a second surface. The first surface is configured with multiple first connection pads corresponding to the die pads. The second surface is configured with multiple second connection pads correspondingly connected with each of the first connection pads on the first surface, respectively. The second connection pads are used to be correspondingly connected with each contact of the predetermined circuit on a printed circuit board, so that the chip may be mounted on a printed circuit board and achieved with electric connection through the second connection pads. During manufacturing, the flexible printed circuit is used to correspondingly and electrically connect each of the first connection pads disposed on the first surface with each die pad on the front surface of the chip; then bending and extending the flexible printed circuit to detour a side edge of the chip to be attached on the back surface of the chip. Thus, each of the second connection pads disposed on the second surface of the flexible printed circuit may be electrically connected and mounted on a printed circuit board, and thus the active areas disposed on the front surface of the chip may be cooperated with the printed circuit board to achieve the function of the active area, so as to achieve a simplified manufacturing process and cost benefit.

Description

Positive and back electrical connection structure of wafer and manufacturing method thereof

The present invention relates to a positive and negative electrical connection structure of a wafer and a manufacturing method thereof, and more particularly to a method of bending and extending from a front side of a wafer by a flexible circuit board and adhering to one side of the wafer to adhere to the wafer. a back surface of the wafer so that the die pads provided on the front surface of the wafer can be electrically connected to the back surface of the wafer by the circuit of the flexible circuit board to be electrically connected and mounted on a printed circuit board, thereby The active area provided on the front side of the wafer can cooperate with the printed circuit board to achieve the function of using the active area.

Using a surface mount technology (SMT) to electrically connect a wafer in a flip-chip manner and mount it on a printed circuit board (PCB) is a common configuration and conventional technique for current wafers. A plurality of die pads disposed on the front surface of the chip face the printed circuit board (PCB) and are electrically connected to respective preset contacts of the circuit layer disposed on the surface of the printed circuit board. .

However, when a positive area is provided on the front side of a wafer in addition to a plurality of die pads, it cannot be electrically connected and mounted in a flip-chip manner. On the circuit board (PCB). Here, a fingerprint identification wafer such as the wafer 10 shown in FIG. 2 is taken as an example, but is not intended to limit the present invention. The front surface 11 of the wafer 10 is provided with a plurality of die pads 110 and an active area (active). Area) 111 such as a fingerprint active area (sensor active area), The sensing area 111 is configured to externally sense a fingerprint image (such as pressing a finger on the surface of the active area 111) and convert it into an electronic signal, and then transmit the electronic signal to the electrical property through the die pad 110. Connected printed circuit boards for identification or related work. Since the active area 111, such as the fingerprint recognition sensing area, is externally sensed, the surface of the active area 111 must face the opposite side of the printed circuit board, otherwise it will be hidden by the printed circuit board, so that the front side of the wafer 10 is 11 A plurality of die pads 110 are not electrically connected and mounted on a printed circuit board (PCB) in a flip-chip manner.

Although a plurality of bonding pads 110 and a printed circuit board (PCB) on the front surface 11 of the wafer 10 may be electrically connected by other bonding methods, such as a wire bond method, The wire used is drawn from the surface of the die pad 110 to the printed circuit board (PCB) at the back side 12 of the wafer 10, so that the highest point of the wire is relatively higher than the front side of the wafer 10. Or a pad of the die pad 110 at a distance, and the periphery of the wire is generally applied as an insulating outer cover to cover and protect the wires so that the wires (the wires) The difference between the wire or its outer sheath relative to the sensing surface of the active area 111 is increased, as illustrated by FIG. 1 , which is like the second surface 22 in FIG. 1 and the active area. The difference between the sensing surface of 111 (such as the front side 11 of the wafer 10), but the actual drop will be larger than 50 μm as shown in Fig. 1, causing the difference and unevenness between the surface of the active area 111 and the surrounding surface, and the relative influence. The action area 111, for example, identifies the sensing function and the use effect of the sensing area. In addition, as in the package of the wafer 10, electrical conductive vias are arranged between the front side 11 and the back side 12. The design of such via holes is common in chip packaging and related prior art, but the process is relatively cumbersome and complicated, and does not conform to Cost-effectiveness.

As can be seen from the above, a plurality of die pads and others are simultaneously provided on one front side. In the case of an active area such as a chip for fingerprint identification of a sensor active area, the structure and/or process of the prior art in the prior art is difficult to meet the requirements of actual use, and therefore There is still a need for further improvement in the field.

The main object of the present invention is to provide a positive and negative electrical connection structure of a wafer and a manufacturing method thereof, which are formed by bending a front surface of a wafer by a flexible circuit board and sticking around one side edge of the wafer. The back surface of the wafer is such that the die pads provided on the front surface of the wafer can be electrically connected to the back surface of the wafer by the circuit of the flexible circuit board for electrical connection and mounting on a printed circuit board. Therefore, the active area provided on the front surface of the wafer can cooperate with the printed circuit board to achieve the function of using the active area.

In order to achieve the above object, the positive and negative electrical connection structure of the wafer of the present invention comprises a wafer and a flexible printed circuit (FPC), and a plurality of die pads are disposed on the front surface of the wafer. And at least one active area, such as a fingerprint active area; the flexible circuit board has a first surface and a second surface, and the first surface is provided with a plurality of first connection pads for Corresponding to each of the die pads disposed on the front surface of the wafer; the second surface is provided with a plurality of second connection pads for electrically connecting with the first connection pads on the first surface, respectively. The second connection pads are respectively connected to the exposed contacts of the connection circuit preset on the printed circuit board used together, so that the chip can be provided with the second connection pads by the flexible circuit board. It is mounted on a printed circuit board and electrically connected.

In order to achieve the above object, the manufacturing method of the electrical connection structure between the front and the back of the wafer of the present invention comprises the following steps:

Step 1: providing a wafer having a plurality of die pads on the front side of the wafer And at least one active area.

Step 2: providing a flexible circuit board having a first surface and a second surface, the first surface being provided with a plurality of first connection pads for respectively corresponding to the die pads The second surface is provided with a plurality of second connection pads respectively electrically connected to the first connection pads on the first surface by the circuit design of the flexible circuit board, and the second connection pads are used for Correspondingly connected to the exposed contacts of the connection line preset on a printed circuit board.

Step 3: Correspondingly, each of the first connection pads disposed on the first surface of the flexible circuit board is electrically connected to each of the crystal pads on the front surface of the chip.

Step 4: bending and extending the flexible circuit board and bypassing one side edge of the wafer to adhere to the back surface of the wafer, thereby enabling each of the second connection pads disposed on the second surface of the flexible circuit board Facing outward, the electrical connection can be electrically connected and mounted on a phase-matched printed circuit board so that the active area provided on the front side of the wafer can be used in conjunction with the printed circuit board to achieve the use of the active area. Features.

In an embodiment of the invention, the active area is a sensor active area, and a high transmittance medium layer is further disposed on the sensing area for protection. The sensing area.

In an embodiment of the present invention, the high transmittance dielectric layer disposed on the sensor active area is electrically connected to the flexible circuit board in each of the first connection pads. The height after the pads on the front side is flush, that is, the same height as the top surface (second surface) of the flexible circuit board.

10‧‧‧ wafer

11‧‧‧ positive

12‧‧‧ Back

110‧‧‧ crystal pad

111‧‧‧Action area

20‧‧‧Soft circuit board

21‧‧‧ first surface

210‧‧‧First connection pad

22‧‧‧ second surface

220‧‧‧Second connection pad

30‧‧‧Chemical Nickel Gold (ENIG)

40‧‧‧Adhesive layer

50‧‧‧High transmittance dielectric layer

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing an embodiment of an electrical connection structure between a front side and a back side of a wafer of the present invention.

Figure 2 is a top plan view of an embodiment of the wafer of the present invention.

3A to 3E are schematic flow charts showing a method of manufacturing the electrical connection structure between the front and the back of the wafer of the present invention.

Fig. 4 is a cross-sectional view showing a dielectric layer of high transmittance provided on the front surface of the sensing region provided on the front surface of the wafer of the present invention in Fig. 1.

Figure 5 is a cross-sectional view showing the height of the high transmittance dielectric layer in flush with the height of the flexible circuit board in Fig. 4.

In order to make the present invention more clear and detailed, the preferred embodiment and the following drawings are used to describe the structure and technical features of the present invention as follows: Referring to FIG. 1, the positive and negative electrical connections of the wafer of the present invention are described. The structure includes a wafer 10 and a flexible printed circuit (FPC) 20. The wafer 10 can be a fingerprint identification chip and the active area can be a sensor active area (sensor active area). However, it is not intended to limit the invention. The front surface 11 of the wafer 10 is provided with a plurality of die pads 110 and at least one sensor active area 111 (such as a fingerprint identification sensing area) as shown in FIG. In FIG. 2, four sides of the wafer 10 are provided with four die pads 110 and arranged in a row, but are not intended to limit the present invention. Therefore, only one die pad 110 is shown in FIG. However, it is not intended to limit the invention. Taking the wafer 10 of FIG. 2 as an example, the wafer 10 is a fingerprint identification chip, and the active area 111 is a fingerprint active area, which occupies a large area on the front surface 11 of the wafer 10. It is used to externally sense a fingerprint image, such as pressing a finger on the surface of the active area 111, converting it into an electronic signal, and then transmitting the die pad 110. The electronic signal is transmitted to the connected printed circuit board (not shown) for identification function related work.

The wafer 10 and the flexible circuit board 20 of FIG. 2 are taken as an example, but the dimensions and proportions shown in FIG. 2 are not intended to limit the present invention. The flexible circuit board 20 can be designed to form a long rectangular flexible circuit board and used. There is a predetermined circuit design having a first surface 21 and a second surface 22; a portion of the flexible circuit board 20 is dropped on the front surface 11 of the wafer 10, and is bent by the front surface 11 of the wafer 10 and Extending around one edge of the wafer 10 and extending and adhering to the back surface 12 of the wafer 10, wherein the flexible circuit board 20 covers the back surface 12 of the wafer 10 as shown in FIG. To limit the invention, that is, the flexible circuit board 20 also covers a portion of the back surface 12 of the wafer 10 (not shown) as needed for design. The first surface 21 is provided with a plurality of first connection pads 210 for respectively corresponding to a plurality of die pads 110 disposed on the front surface 11 of the wafer 10; the second surface 22 is provided with a plurality of The two connection pads 220 are respectively connected to the first connection pads 210 disposed on the first surface 21 by the circuit of the flexible circuit board 20, and the plurality of second connection pads 220 are connected to the plurality of first connections The corresponding connection relationship between the pads 210 is based on the circuit design of the flexible circuit board 20. For the present invention, it can be achieved by using the existing circuit board circuit design technology, and therefore will not be described herein.

Taking the wafer 10 and the flexible circuit board 20 of FIG. 2 as an example, the plurality of first connection pads 210 disposed on the first surface 21 are separated from the plurality of second connection pads 220 disposed on the second surface 22. A distance is located near the opposite ends of the long rectangular flexible circuit board 20, but is not intended to limit the present invention, so that one portion of the flexible circuit board 20 can be dropped on the front surface 11 of the wafer 10, and The flexible circuit board 20 can be bent from the front side 11 of the wafer 10 and bypassed the side edge of the wafer 10 to extend to the back side 12 of the wafer 10 such that the second surface 22 can be adhesively attached to the back On the face 12. The plurality of second connection pads 220 are connected to the exposed contacts of the connection circuit preset on a printed circuit board (not shown) for use in conjunction with the arrow A in FIG. The second connection pads 220 are respectively connected to the exposed contacts of the connection lines preset on a printed circuit board (not shown) in the direction indicated by the arrow A, so that the wafer 10 can borrow the flexible circuit. The second connection pads 220 disposed on the board 20 are mounted on a printed circuit board (not shown) and electrically connected. As for the design of the printed circuit board or the corresponding connection method such as flip chip method, it is regarded as a conventional technique in the present invention, and therefore will not be further described.

In addition, taking the structure shown in FIG. 2 as an example, a plurality of first connection pads 210 disposed on the first surface 21 of the flexible circuit board 20 and a plurality of crystal pads disposed on the front surface 11 of the wafer 10 ( Before the die pad 110 is connected, an electroless nickel/immersion gold (ENIG) 30 may be disposed on the surface of each die pad 110, but is not intended to limit the present invention; the chemical nickel gold The layer (ENIG) 30 prevents oxidation of the die pad 110 and improves the solder joint connection efficiency between the first connection pad 210 and the die pad 110.

In addition, taking the structure shown in FIG. 2 as an example, an adhesive layer 40 such as a double-sided adhesive can be preset on the first surface 21 of the flexible circuit board 20, but is not used to limit the present invention, so that the flexible circuit When the front surface 11 of the wafer 10 is bent around the edge of the wafer 10 and extends to the back surface 12 of the wafer 10, the first surface 21 of the flexible circuit board 20 can be adhered by the adhesive layer 40. Covered on the back side 12.

The method for manufacturing the electrical connection structure between the front and the back of the wafer of the present invention comprises the following steps:

Step 1: providing a wafer 10 as shown in FIG. 3A, the front surface 11 of the wafer 10 is provided with a plurality of die pads 110 and at least one active area 111; and each of the crystal pads 110 An electroless nickel/immersion gold (ENIG) 30 may be preset as shown in FIG. 3B.

Step 2: providing a flexible circuit board 20 as shown in FIG. 3C, the flexible circuit board 20 has a first surface 21 and a second surface 22, and the first surface 21 is provided with a plurality of first connection pads 210 for respectively Corresponding to the die pads 110, the second surface 22 is provided with a plurality of second connection pads 220 for respectively connecting the first connection pads 210 on the first surface 21 by the circuit of the flexible circuit board 20. Correspondingly, the second connection pads 220 are connected to the exposed contacts of the connection circuit preset on the printed circuit board for use; wherein the second surface 22 of the flexible circuit board 20 is A double-sided adhesive layer 40 can be pre-applied as shown in Fig. 3D.

Step 3: Correspondingly, each of the first connection pads 210 disposed on the first surface 21 of the flexible circuit board 20 is electrically connected to each of the crystal pads 110 on the front surface 11 of the wafer 10 or an electroless nickel gold layer (ENIG) 30 thereof. This is shown in Figures 3C and 3D.

Step 4: As shown in FIG. 3E, the flexible circuit board 20 is bent and bypassed on one side edge of the wafer 10 to extend onto the back surface 12 of the wafer 10 and adhered (eg, using the adhesive layer 40). The second connecting pad 220 disposed on the second surface 22 of the flexible circuit board 20 can face outward (as indicated by an arrow A in FIG. 1) for electrical connection by subsequent operations. And mounted on a phase-matched printed circuit board (not shown) such that the active area 111 provided on the front side 11 of the wafer 10 can be used in conjunction with the printed circuit board to achieve the function of the wafer 10, such as a fingerprint identification wafer. Fingerprint identification function.

In addition, as shown in FIG. 4, a surface of the active area 111 is further provided with a high transmittance dielectric layer 50 for protecting the active area 111 without affecting its function; as shown in FIG. The dielectric layer 50 is disposed on the front surface 11 of the wafer 10 for comprehensively shielding the active area 111, but each of the die pad 110 and/or the chemical nickel gold layer (ENIG) 30 provided on each of the die pads 110 is exposed.

In addition, the height of the high transmittance dielectric layer 50 disposed on the inductive active region 111 in FIG. 4 is further the height of the flexible circuit board 20 falling on the front surface 11 of the wafer 10 (ie, in FIGS. 4 and 5). The surface of the second surface 22 of the flexible circuit board 20 is flush as shown in FIG. 5 such that the front side 11 of the wafer 10 is formed in the same plane, thereby conforming to the assembly requirements of the wafer 10 such as a fingerprint identification wafer in practical applications.

The above is only the preferred embodiments of the present invention, and is intended to be illustrative, and not restrictive, and it is understood by those of ordinary skill in the art that Many changes, modifications, and even equivalents may be made without departing from the scope of the invention.

10‧‧‧ wafer

11‧‧‧ positive

12‧‧‧ Back

110‧‧‧ crystal pad

111‧‧‧Action area

20‧‧‧Soft circuit board

21‧‧‧ first surface

210‧‧‧First connection pad

22‧‧‧ second surface

220‧‧‧Second connection pad

30‧‧‧Chemical nickel/immersion gold (ENIG)

40‧‧‧Adhesive layer

Claims (8)

An electrical connection structure between a front and a back of a wafer, comprising: a wafer having a plurality of die pads and at least one active area on the front surface; and a flexible circuit board (FPC) The first surface and the second surface are provided with a plurality of first connecting pads respectively corresponding to the respective crystal pads provided on the front surface of the wafer, and the second surface is provided with a plurality of The two connection pads are respectively connected to the first connection pads on the first surface, wherein the second connection pads are used for externally connecting the preset connection lines on the printed circuit board used together a point corresponding connection, so that the chip can be mounted on the printed circuit board and electrically connected by the second connection pads provided on the flexible circuit board; wherein the flexible circuit board is bent and wound by the front surface of the chip Extending to one side of the wafer and extending to the back surface of the wafer and adhesively adhering to the back surface, so that the crystal pads provided on the front surface of the wafer can be displaced to the back surface of the wafer by the circuit connection of the flexible circuit board and Externally connected to the power supply and installed on the print Circuit board. The positive and negative electrical connection structure of the wafer according to claim 1, wherein the wafer is a fingerprint identification chip and a fingerprint identification sensing area is disposed on the front surface thereof. The positive and negative electrical connection structure of the wafer according to claim 1, wherein a chemical nickel gold layer (ENIG) is disposed on the surface of each of the crystal pads disposed on the front surface of the wafer. The positive-to-back-side electrical connection structure of the wafer of claim 2, wherein the first surface of the flexible circuit board is provided with an adhesive layer such that the flexible circuit board is bent from the front surface of the wafer and bypasses the When the edge of one side of the wafer extends to the back side of the wafer, the adhesive layer can be adhered to the back surface. The electrical connection structure between the front and the back of the wafer according to claim 1, wherein the upper surface of the active region disposed on the front surface of the wafer is further provided with a high transmittance dielectric layer. The positive and negative electrical connection structure of the wafer according to claim 5, wherein the high transmittance dielectric layer is disposed on the front surface of the wafer and completely shields the active region but exposes each of the crystal pads. The positive and negative electrical connection structure of the wafer according to claim 5, wherein the height of the high transmittance dielectric layer disposed on the active region is further equal to the height of the flexible circuit board falling on the front surface of the wafer. Flat so that the front faces of the wafers form the same plane. A method for manufacturing an electrical connection structure between a front and a back surface of a wafer, comprising the steps of: providing a wafer having a plurality of crystal pads and at least one active region on a front surface thereof; and step 2: providing a softness a circuit board, the flexible circuit board has a first surface and a second surface, and the first surface is provided with a plurality of first connection pads respectively corresponding to the respective crystal pads disposed on the front surface of the wafer, the first a plurality of second connecting pads are respectively disposed on the two surfaces for respectively corresponding to the first connecting pads on the first surface, wherein the plurality of second connecting pads are used for connection with a preset connection on a printed circuit board Each of the exposed contacts of the circuit is correspondingly connected; Step 3: electrically connecting each of the first connection pads disposed on the first surface of the flexible circuit board to each of the crystal pads disposed on the front surface of the flexible circuit; Step 4: The flexible circuit board is bent and wound around one side edge of the wafer to extend onto the back surface of the wafer and adhered to the back surface, thereby providing the second connection pads disposed on the second surface of the flexible circuit board. Can face the printed circuit board outward .