CN1452229A - Secondary half-etching preparation method and packaging structure of image sensor single-layer lead frame - Google Patents

Abstract

The image sensor single-layer lead frame secondary half-etching preparation method and its packaging structure, the packaging structure includes sensing chip, single-layer lead frame and glass cover plate, the wire sets up chip carrier and pin, the pin inboard surrounds the circumference of chip carrier and the outside welds with the pin of external printed circuit board, the sensing chip sticks to the top surface of chip carrier and connects the inside top surface of each pin with the metal wire in order to transmit the electrical signal, the glass cover plate covers over the sensing chip, capsulate three as an organic whole by the plastic material; the preparation method comprises the following steps: semi-etching the chip seat and the position and the shape of each pin on the top surface of the flat conductor substrate; half-etching concave structures at the bottom of the chip holder and the bottom of the inner side of each pin, and performing plastic pre-mold embedding and electrical isolation; electroplating the etched lead frame and embedding the lead frame in a plastic pre-mold; the sensing chip is glued on the top surface of the chip base, the wires are welded between the top surfaces of the inner sides of the pins, the sensing chip is coated by the glass cover plate stuck on the top surface of the plastic pre-mold convex wall, the processing time is saved, and the product quality is good.

Description

Secondary half-etching preparation method and packaging structure of image sensor single-layer lead frame

technical field

The invention relates to an image sensor, in particular to a method for preparing a single-layer lead frame of an image sensor with a two-time half-etching preparation method and a packaging structure thereof for manufacturing a three-dimensional structure of a chip holder and pins.

Background technique

Referring to FIGS. 6 to 9 , they are the existing image sensor (Image sensor) packaging technology, and the existing lead frame (Lead frame) manufacturing method is stamping or stacking. Among them, the stamping method is to etch the position and shape of the die pad 71 and each lead 72 on the flat conductor substrate, and then punch the die pad 71 from the bottom to make it float out. pin 72 plane. In addition, the stamping method also has the method of directly stamping the conductor plate, and directly punching out the three-dimensional structure of the chip holder 71 and each pin 72, but both of these methods need to be processed by mechanical stamping, and it is not easy to achieve accurate dimensional accuracy. It is suitable for the packaging requirements of modern image sensor chips with a small area and a large number of pins; moreover, it is not easy to control the flatness of the pin 72 in the stamping process, and it is usually necessary to cooperate with the alignment process of the pin 72, which is suitable for today's high-density, high-pixel It is indeed difficult to adapt to the technical requirements of image sensor chip packaging, and it is not easy to make products of good quality.

As shown in Figure 7, another existing stacking manufacturing method is to make two upper and lower layers of lead frame templates 81 and 82 respectively in two procedures. The upper template 81 includes a chip holder 83 and each pin 84, and the lower template 82 only includes each pin 85; after the upper and lower templates 81 and 82 are stacked, the bottom of the chip holder 83 is recessed relative to the bottom surface of the pin 85, and is electrically isolated through plastic packaging. The overall packaging process is shown in Figure 8 and Figure 9 . However, this stacking method involves the dimensional accuracy of the upper and lower layers of templates 81, 82. For image sensor chip packaging with a small area, a large number of pins 84, 85, delicate pins, and high precision requirements, this preparation The process is also difficult, and it is not easy to ensure good product quality; moreover, the contact resistance of the two lead frame templates 81, 82 is also a problem, and it is not easy to control it to a uniform level, which will affect the effect of micro-sensing signal transmission. The need for improvement.

Contents of the invention

In order to overcome the above-mentioned shortcomings of the existing product preparation methods, the present invention provides a method for preparing a single-layer lead frame of an image sensor by half-etching twice and its packaging structure. Difficulties, because the three-dimensional structure of the lead frame is made by two half-etching preparation processes, the precision can reach the micron level of the integrated circuit, so the welding with the sensor chip signal contact can have better precision, so it can be applied to today's high-density , high-pixel image sensing chip packaging technology requirements, can ensure good product quality; in addition, the present invention twice half-etching process is a chemical process, the precision can reach the molecular level, while avoiding the mechanical stamping process, so it can be better Controlling the flatness of the pins does not need to cooperate with the pin alignment program at all, and also solves the problem of contact resistance in the stacking method, and the manufacturing accuracy and speed are completed at one time; moreover, the subsequent wire bonding packaging process can also be guaranteed Better trust in quality; in addition, the two half-etching processes can be completely completed on the same machine, eliminating the cost of transporting the lead frame to another place for stamping, saving processing time and increasing output, and the practical effect is ideal.

The technical solution adopted by the present invention to solve its technical problems is:

The second half-etching (Etching) preparation method of the single-layer lead frame of the image sensor of the present invention is characterized in that the preparation method comprises: a first step: half-etching the chip holder ( die pad) and the position and shape of each pin (lead), and etched several through holes at appropriate positions to facilitate the inlay and fixation of the subsequent plastic pre-mold; the second step: halfway on the bottom surface of the flat conductor substrate Etching method, etch the concave structure at the bottom of the chip holder and the inner bottom of each pin to inlay and electrically isolate the plastic pre-mold; the third step: the lead frame (lead frame) that is etched in the first and second steps Electroplating treatment is carried out, and then embedded in the plastic pre-mold by injection, the plastic pre-mold forms a convex wall around the chip holder; then the sensing chip (chip) is glued on the top surface of the chip holder, and the sensing chip Wire bonding to the inner top surface of each pin, and finally stick a glass cover plate on the top surface of the convex wall of the plastic pre-mold to cover the sensing chip and complete the packaging process.

The aforementioned single-layer lead frame secondary half-etching (Etching) preparation method of the aforementioned image sensor is characterized in that the chip seat is etched with several through holes, so that the plastic pre-mold injection process forms several holes on the top surface of the chip seat. Bumps, to control the horizontal angle of the sensing chip paste, to prevent the sensing chip from tilting and affect the quality of the bonding wire.

The aforementioned single-layer lead frame secondary half-etching (Etching) preparation method of the image sensor is characterized in that anchor holes are etched out at the appropriate positions of the pins, and the anchor holes of each pin are used as plastic during the injection process of the plastic pre-mold. The pre-mold is fixed on the base of the lead frame, and the bonding between the plastic pre-mold and each lead is strengthened, and the quality of the package is improved.

The aforementioned single-layer lead frame secondary half-etching (Etching) preparation method of the aforementioned image sensor is characterized in that the inside of each pin is defined as an inner lead around the periphery of the chip seat, which serves as a lead for connecting the sensing chip. The signal contact, each pin extending from the outside to the lower edge of the package is defined as an out lead, which is used as an SMT pin for soldering an external printed circuit board.

The package structure of the single-layer lead frame secondary half-etching (Etching) preparation method of the image sensor of the present invention includes a sensing chip, a lead frame and a glass cover plate; it is characterized in that the lead frame is a single-layer lead frame, which has A chip seat and several pins, the inner side of each pin surrounds the periphery of the chip seat, and the outer side of each pin extends to the lower edge of the package body to be welded with the SMT pins of the external printed circuit board; the sensing chip is pasted on the top surface of the chip seat , and connect the inner top surface of each pin with a metal wire to transmit electrical signals; the glass cover plate covers the sensor chip, and the above three are packaged as one by plastic material.

The beneficial effect of the present invention is that it can solve the problems caused by the mechanical stamping preparation process of the existing lead frame, thereby providing a single-layer lead frame secondary half-etching preparation method and packaging structure, because the three-dimensional structure of the lead frame 2 is based on Made in two half-etching processes, the precision can reach the micron level of the integrated circuit, so the welding with the signal contact of the sensor chip 1 can have better precision. For today's high-density, high-pixel image sensor chip packaging, it is really The preferred method, easy to ensure good product quality. Secondly, the twice half-etching process of the present invention belongs to chemical processing, the precision can reach the molecular level, and at the same time, the mechanical stamping process is avoided, so the flatness of the pin 22 can be better controlled, and there is no need to cooperate with the pin 22 at all. The positive procedure also solves the problem of contact resistance in the stacking method, and the manufacturing accuracy and speed are completed at one time. Furthermore, the quality of the subsequent wire-bonding package is guaranteed. In addition, the two half-etching processes can be completely completed on the same machine, eliminating the cost of transporting the lead frame 2 to other places for stamping, saving processing time, increasing output, and achieving ideal practical effects.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic side view of the half-etched top surface of the conductor substrate of the present invention.

Fig. 2 is a schematic side view of the half-etched bottom surface of the conductor substrate of the present invention.

Fig. 3 is a schematic diagram of the electroplating of the lead frame of the present invention.

FIG. 4 is a schematic top view of the lead frame of the present invention in an etching-completed state.

FIG. 5 is a schematic diagram of the completion of the sensing chip package of the present invention.

FIG. 6 is a schematic diagram showing the completion of encapsulation in the conventional manufacturing method of stamping type lead frame.

FIG. 7 is a schematic side view of a conventional stacked lead frame.

FIG. 8 is a schematic diagram of the existing stacked lead frame plastic pre-mold inlay.

FIG. 9 is a schematic diagram of the completion of encapsulation in the conventional stacked lead frame manufacturing method.

Explanation of symbols in the figure

Part of prior art: 71 chip holders, 72 pins, 81 upper model, 82 lower model, 83 chip holders, 84 pins, 85 pins;

Parts of the present invention: 1 sensing chip, 11 metal wire, 2 single-layer lead frame, 21 chip seat, 22 pins, 221 inner pins, 222 outer pins, 23 through holes, 24 anchor holes, 25 recessed structure, 3 plastic pre-molds, 31 convex grains, 32 convex walls, 4 glass cover plates.

Detailed ways

Referring to FIG. 1 to FIG. 5 , the present invention relates to a method for preparing a single-layer lead frame of an image sensor by secondary half-etching and its packaging structure.

As shown in Figure 5, the structure of the image sensor of the present invention includes: a sensing chip 1, a single-layer lead frame 2 and a glass cover plate 4; the lead frame is provided with a chip holder 21 and several pins 22, each pin 22. The inner side surrounding the periphery of the chip holder 21 is defined as an inner lead 221, which is used to connect the signal contact of the sensor chip 1. The outer side of each pin 22 extending to the lower edge of the package is defined as an outer lead (outlead). 222, which is an SMT pin used for welding an external printed circuit board to transmit electrical signals; the sensor chip 1 is pasted on the top surface of the chip holder 21, and is connected to the top surface of each inner pin 221 with a metal wire 11, and the The signal contacts of the sensing chip 1 are connected to external signal pins to facilitate communication between the sensing chip 1 and the outside world; the glass cover 4 covers the sensing chip 1 to protect the sensing chip 1 and facilitate light Penetrate to the sensing chip 1; the above three are packaged as a whole with plastic materials, and the main preparation procedures are as follows:

The first step: as shown in FIG. 1, the position and shape of the chip holder 21 and each pin 22 are etched out by half-etching on the top surface of the flat conductive substrate, and several through-holes are etched at appropriate positions. 23. Anchor holes 24; wherein, the through holes 23 will form several bumps 31 on the top surface of the chip holder 21 during the subsequent injection process of the plastic pre-mold 3, so as to control the horizontal angle when the sensing chip 1 is attached to the chip holder 21 , to prevent the sensing chip 1 from tilting, which affects the quality of the subsequent welding wires. On the other hand, it also strengthens the bonding of the plastic pre-mold 3 and the chip holder 21; The injection process will serve as the basis for fixing the plastic pre-mold 3 to the lead frame 2, strengthen the bonding between the plastic pre-mold 3 and each lead 22, and increase the reliability of the overall packaging quality.

The second step: as shown in Figure 2, on the bottom surface of the flat conductor base material, etch the concave structure 25 at the bottom of the chip holder 21 and the bottom of each inner pin 22 in a half-etching manner, so as to facilitate the plastic pre-mold 3 Inlaid and electrically isolated, after two half-etching processes, as shown in FIG. 2 and FIG. 4 , the three-dimensional structure of the overall lead frame 2 has been formed.

The third step: as shown in Figure 3, the lead frame 2 etched in the first and second steps is subjected to electroplating treatment; then as shown in Figure 5, the lead frame 2 is embedded in the plastic pre-mold 3 by injection, And form the convex wall 32 around the plastic pre-mold 3 and the chip holder 21, then the sensing chip 1 is glued on the top surface of the chip holder 21 with silver glue, and between the sensing chip 1 and the top surface of each inner pin 221 Weld the metal wires 11 to facilitate electrical signal transmission; then paste the glass cover plate 3 with UV glue on the top surface of the convex wall 32 of the plastic pre-mold 3 to cover the sensing chip 1 and complete the packaging process.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to within the scope of the technical solutions of the present invention.

Claims (5)

1. A method for preparing a single-layer lead frame of an image sensor by half-etching twice. The position and shape of the pins; the second step: half-etching the bottom surface of the flat conductor substrate, etching the concave structure at the bottom of the chip holder and the inner bottom of each pin, and performing the inlay and electrical isolation of the plastic pre-mold ; The third step: electroplating the lead frame etched in the first and second steps, and then inserting it into the plastic pre-mold by injection, and the plastic pre-mold forms a convex wall around the chip seat; then the sensing chip Glue on the top surface of the chip seat, and weld wires between the sensing chip and the inner top surface of each pin, and finally paste a glass cover on the top surface of the plastic pre-molded convex wall to cover the sensing chip to complete the packaging process . 2. The method for preparing a single-layer lead frame of an image sensor by secondary half-etching according to claim 1, wherein a plurality of through holes are etched out in the chip holder, so that the injection process of the plastic pre-mold is formed on the top surface of the chip holder. Several bumps are used to control the horizontal angle of the sensing chip sticking, preventing the sensing chip from tilting and affecting the quality of the bonding wire. 3. The method for preparing a single-layer lead frame of an image sensor by secondary half-etching according to claim 1, characterized in that each pin is etched with an anchor hole, and the anchor hole of each pin is formed during the injection process of the plastic pre-mold. As the basis for fixing the plastic pre-mold to the lead frame, it strengthens the bonding between the plastic pre-mold and each lead, and improves the quality of the package. 4. The method for preparing a single-layer lead frame of an image sensor by secondary half-etching according to claim 1, wherein the inner side of each pin is defined as an inner pin around the periphery of the chip holder, which is used as a connection to the sensing chip. The signal contacts, the outer pins extending to the lower edge of the package are defined as external pins, which are used as SMT pins for soldering the external printed circuit board. 5. A packaging structure of a method for preparing a single-layer lead frame by secondary half-etching for an image sensor, including a sensing chip, a lead frame and a glass cover; it is characterized in that the lead frame is a single-layer lead frame, which has a Chip holder and several pins, the inner side of each pin surrounds the periphery of the chip holder; the sensing chip is pasted on the top surface of the chip holder, and is connected to the inner top surface of each pin with a metal wire to transmit electrical signals; the glass cover plate Covering above the sensing chip, the above three are packaged as one by plastic material.

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