TWI876682B - Carbon dioxide laser cutting method - Google Patents

Abstract

A carbon dioxide laser cutting method includes the following steps: providing a flexible substrate that has a plurality of dicing lanes set on a surface and a plurality of wafers divided by the dicing lanes; forming an outer metal frame and an inner metal frame around the wafer, wherein the outer metal frame is arranged along one side of the dicing lane away from the wafer, the inner metal frame is arranged along one side of the dicing lane near to the wafer, thereby a gap is formed between the outer metal frame and the inner metal frame to expose part of each dicing lane; and irradiating by a carbon dioxide laser beam along the dicing lanes exposed from the gap, so that the flexible substrate is divided into a plurality of independent wafers along the gap. The invention utilizes the carbon dioxide laser with the wavelength that is less absorbed by the metal surface so that the laser could only act on the gap between the two metal frames to improve the cutting accuracy of the wafer.

Description

CO2 Laser Cutting Method

The present invention relates to the technical field of laser cutting, and in particular to a carbon dioxide laser cutting method capable of improving cutting accuracy.

In recent years, flexible electronic technology and product applications have developed into the mainstream of scientific and technological research and development, and have also driven the continuous innovation of related processes. Since flexible electronics is a technology that builds components or materials on a flexible substrate, it is a complex multi-layer structure. In the traditional mechanical cutting process, the flexible substrate is easily affected by the concentration of mechanical forces, resulting in positioning errors or panel deformation, which can easily affect the overall characteristics of the panel and components. In addition, modern flexible electronic products emphasize the trend of being thin, short, and flexible, and the requirements for process accuracy are also strict, resulting in the guarantee of product yield being severely tested.

Compared with the traditional mechanical cutting process, the laser cutting process has the advantages of non-contact processing, high processing accuracy, low processing cost and high processing efficiency, and will become the development trend of the industry in the future. Among them, the carbon dioxide laser cutting process is significantly better than the traditional mechanical cutting process in the cutting quality of soft substrates, and can be used as one of the solutions for cutting soft substrates. However, the existing carbon dioxide laser cutting accuracy still has room for improvement. Please refer to Figure 1A and Figure 1B. Figure 1A is a schematic diagram of the chip image after setting the cutting, and Figure 1B is a schematic diagram of the chip shape cut into inconsistent sizes due to poor carbon dioxide laser cutting accuracy. During the CO2 laser cutting process, the high temperature generated by the laser energy acting on the cutting path 12 will cause the edge of the substrate 10 adjacent to the cutting path 12 to melt, thereby affecting the cutting accuracy and causing the size of the chip 20 to become inconsistent after cutting. For example, the distances d1, d2, d3 and d4 from the active area to the edge of the chip 20 in FIG. 1B are all different, which will affect the subsequent bonding process and reduce the product yield.

Therefore, how to improve the carbon dioxide laser cutting method to solve the various deficiencies of the above-mentioned previous technologies has become a topic that the relevant industry players are eager to research and develop.

In view of this, the main purpose of the present invention is to provide a carbon dioxide laser cutting method. By taking advantage of the fact that the metal surface is less likely to absorb the wavelength of the carbon dioxide laser, two metal frames are set on the inner and outer sides of the cutting path, and a gap is sandwiched between the two metal frames, so that the laser can only act in the gap between the two metal frames, thereby effectively improving the cutting accuracy of the chip and further achieving the purpose of improving the process yield.

To achieve the above-mentioned purpose, the present invention provides a carbon dioxide laser cutting method, the steps of which include: (1) providing a flexible substrate, the flexible substrate having a plurality of cutting paths set on the surface and a plurality of chips divided by the cutting paths; (2) forming an outer metal frame and an inner metal frame around each chip, wherein the outer metal frame is arranged along a side of the cutting path away from each chip, and the inner metal frame is arranged along a side of the cutting path close to each chip, and a gap is sandwiched between the outer metal frame and the inner metal frame to expose a portion of each cutting path; and (3) using a carbon dioxide laser beam to irradiate along the cutting path exposed to the gap, thereby dividing the flexible substrate into multiple independent chips along the gap.

According to an embodiment of the present invention, the material of the outer metal frame and the inner metal frame is aluminum (Al), silver (Ag) or gold (Au).

According to an embodiment of the present invention, the width of the gap is greater than or equal to the wavelength of the CO2 laser beam.

According to an embodiment of the present invention, the wavelength of the carbon dioxide laser beam is in the range of 9.2 to 9.7 microns or 10.2 to 10.7 microns.

According to the embodiment of the present invention, the aforementioned carbon dioxide laser cutting method meets the following conditions: Wherein, LW is the line width of the internal metal frame; is the accuracy of laser cutting equipment; S is the gap width.

According to an embodiment of the present invention, the aforementioned 50 to 200 microns.

According to an embodiment of the present invention, each of the aforementioned chip surfaces includes an active area and a frame area surrounding the active area, an outer metal frame is arranged on the cutting path and extends along the outer side of the frame area, and an inner metal frame is arranged on the frame area and extends along the inner side of the cutting path.

According to an embodiment of the present invention, the aforementioned carbon dioxide laser cutting method further includes, in step (2), forming a sensing electrode layer and a metal circuit layer in the active area and the frame area respectively, wherein the metal circuit layer is electrically connected to the sensing electrode layer.

According to an embodiment of the present invention, the aforementioned carbon dioxide laser cutting method further includes forming a plurality of connection pads in the frame area in step (2), wherein the connection pads electrically connect the metal circuit layer and the sensing electrode layer.

According to an embodiment of the present invention, the aforementioned carbon dioxide laser cutting method further includes forming a plurality of ground pads in the frame area in step (2), wherein the ground pads are electrically connected to the inner metal frame so that the inner metal frame serves as a ground wire.

According to an embodiment of the present invention, the component material of the aforementioned flexible substrate includes polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyamide (PA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyether sulphate (PES), polyprotoethylene (PNB), polyether ether ketone (PEEK), polyethylene naphthalate (PEN), cycloolefin polymer (COP) or cycloolefin copolymer (COC).

Compared with the prior art, the present invention has the following advantages: (1) The present invention overcomes the problem that the existing carbon dioxide laser cutting process causes edge melting of the substrate, thereby affecting the cutting accuracy and causing a decrease in product performance and process yield. (2) The present invention can break through the accuracy limitation of the laser cutting equipment itself by setting two metal frames on the inner and outer sides of the cutting path and using the gap between the two metal frames to limit the range of action of the carbon dioxide laser beam, thereby achieving the ability to have high cutting accuracy, thereby improving the overall yield and production capacity.

The above description is only used to illustrate the problems to be solved by the present invention, the technical means for solving the problems, and the effects produced, etc. The specific details of the present invention will be introduced in detail in the following implementation methods and related drawings.

The embodiments of the present invention will be further explained below in conjunction with the relevant drawings. As much as possible, the same reference numerals in the drawings and the specification represent the same or similar components. In the drawings, shapes and thicknesses may be exaggerated for simplicity and convenience, and some details may not be fully drawn to simplify the drawings. It is understood that the components not specifically shown in the drawings or described in the specification are in the form known to those with ordinary knowledge in the relevant technical field. Those with ordinary knowledge in this field can make various changes and modifications based on the content of the present invention.

The technical solutions adopted in the embodiments of the present invention are used to more clearly illustrate the technical solutions of the present invention, and are therefore only used as examples. Unless otherwise specified, they should not be used to limit the scope of protection of the present invention. In the description of the specification, many specific details are provided in order to enable readers to have a more complete understanding of the present invention; however, the present invention may still be implemented on the premise of omitting some or all of the specific details. In addition, well-known steps or components are not described in the details to avoid unnecessary restrictions on the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be arbitrarily combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those with ordinary knowledge in the field to which the present invention belongs.

As described in the previous technology, the currently known carbon dioxide laser cutting method will cause edge melting on the substrate, resulting in poor cutting accuracy, which in turn leads to reduced product performance and process yield. In order to solve the above technical problems, the basic idea of the present invention is to provide a carbon dioxide laser cutting method, which can break through the accuracy limitation of the laser cutting equipment itself and achieve the ability of high cutting accuracy, thereby improving the overall yield and production capacity by setting two metal frames on the inner and outer sides of the cutting path and using the gap between the two metal frames to limit the range of action of the carbon dioxide laser beam.

Please refer to Figures 2 to 4. Figure 2 is a flow chart of the carbon dioxide laser cutting method provided by the embodiment of the present invention; Figures 3A to 3D are structural schematic diagrams corresponding to each step of the carbon dioxide laser cutting method provided by the embodiment of the present invention; Figure 4 is a partial enlarged view of the laser irradiation process of Figure 3C.

The carbon dioxide laser cutting method provided by the present invention is suitable for cutting a flexible substrate into multiple chips. In the embodiment of the present invention, the material of the flexible substrate can be a polymer film. For example, the component material of the flexible substrate includes polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyamide (PA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyether sulphate (PES), polyprotoethylene (PNB), polyether ether ketone (PEEK), polyethylene naphthalate (PEN), cycloolefin polymer (COP) or cycloolefin copolymer (COC), but is not limited to this. In the embodiment of the present invention, the chip can be a sensing chip with a metal grid or an ITO metal conductive film. The following is a detailed description of each step in the carbon dioxide laser cutting method of the embodiment of the present invention.

First, see step S10 , as shown in FIG. 3A , the aforementioned flexible substrate 30 is provided. The flexible substrate 30 has a plurality of scribe lines 32 disposed on the surface and a plurality of chips 40 divided by the scribe lines 32 .

Next, see step S20, as shown in FIG. 3B, an outer metal frame 50 and an inner metal frame 52 are formed around each chip 40, wherein the outer metal frame 50 is arranged along a side of the cutting path 32 away from each chip 40, and the inner metal frame 52 is arranged along a side of the cutting path 32 close to each chip 40, and a gap 56 is sandwiched between the outer metal frame 50 and the inner metal frame 52 to expose a portion of each cutting path 32.

Finally, in step S30, as shown in FIG. 3C and FIG. 4, the carbon dioxide laser beam 1 is irradiated along the cutting path 32 exposed to the gap 56, and the flexible substrate 30 is divided along the gap 56 into a plurality of independent chips 40 as shown in FIG. 3D.

As shown in FIG. 3D , each chip 40 used in the embodiment of the present invention may define an active area A1 and a frame area A2 surrounding the active area A1 on the surface, an external metal frame 50 is disposed on the cutting path 32 and extends along the outer side of the frame area A2, and an internal metal frame 52 is disposed on the frame area A2 and extends along the inner side of the cutting path 32. Please further refer to FIG. 5A and FIG. 5B , which are respectively a schematic diagram and a partial enlarged diagram of the specific structure of the chip manufactured in the embodiment of the present invention. In the embodiment of the present invention, in step S20, a sensing electrode layer 42 may be formed in the active area A1 on the surface of each chip 40. The sensing electrode layer 42 may be a metal grid or an ITO transparent conductive film. Then, a metal circuit layer (omitted in the figure to clearly present the technical features of the present invention) is formed in the frame area A2. The metal circuit layer is electrically connected to the sensing electrode layer 42. In step S20, the embodiment of the present invention also forms a plurality of connection pads 46 in the frame area A2. These connection pads 46 are electrically connected to the metal circuit layer and the sensing electrode layer 42. In step (2), the embodiment of the present invention further forms a plurality of ground pads 48 in the frame area A2. These ground pads 48 are electrically connected to the inner metal frame 52, so that the inner metal frame 52 serves as a ground line to eliminate electrostatic interference. In the embodiment of the present invention, the patterning of the outer metal frame 50 and the inner metal frame 52 can be completed at the same time as the patterning of the metal circuit layer, the connection pad 46, and the ground pad 48.

In addition, in step S30, the wavelength of the CO2 laser beam 1 used in the embodiment of the present invention is approximately between 9.2 and 9.7 microns and between 10.2 and 10.7 microns, and the representative wavelengths are 9.3, 9.6, and 10.6 microns. The present embodiment uses the CO2 laser beam 1 with a wavelength of 10.6 microns. In step S20, the outer metal frame and the inner metal frame formed by the present invention do not absorb the wavelength of the CO2 laser beam because the metal material does not absorb the wavelength of the CO2 laser beam. Therefore, the edge of the soft substrate will not melt due to the high temperature generated by the laser, and the gap width between the outer metal frame and the inner metal frame must be greater than or equal to the wavelength of the CO2 laser beam, so that the CO2 laser beam can fully act in the gap to perform cutting. As shown in FIG. 8, it is the absorption of different metals to related wavelengths. As shown in the figure, aluminum (Al), silver (Ag), and gold (Au) have the best absorption rate for carbon dioxide laser (wavelength 10.6 microns), followed by copper (Cu), molybdenum (Mo), iron (Fe), and stainless steel. In the embodiment of the present invention, the external metal frame and the internal metal frame can be made of various metal materials, such as aluminum (Al), silver (Ag), gold (Au), copper (Cu), molybdenum (Mo), iron (Fe), stainless steel, etc., among which aluminum (Al), silver (Ag), and gold (Au) are preferred, and their absorption rates for the wavelength of carbon dioxide laser are close to 0, and they almost do not absorb the wavelength of the carbon dioxide laser beam.

According to the carbon dioxide laser cutting method provided by the present invention, the metal surface is less likely to absorb the wavelength of the carbon dioxide laser beam, and an inner metal frame and an outer metal frame are provided on the inner and outer sides of the cutting path respectively, and the gap between the outer metal frame and the inner metal frame is used to limit the effective range of the carbon dioxide laser beam. The shape of the chip finally cut can be very close to the design drawing (the cutting accuracy is less than 10 microns), which can break through the accuracy limitation of the laser cutting equipment itself and achieve the ability of high cutting accuracy, thereby improving the overall yield and production capacity.

Next, please refer to FIG. 6A and FIG. 6B, which are schematic diagrams of the cutting conditions of the CO2 laser beam with different laser focal spot sizes in the CO2 laser cutting method provided by the embodiment of the present invention. FIG. 6A and FIG. 6B show the preset laser focal spot position of the CO2 laser beam 1 and the maximum laser focal spot offset position P2. Among them, the preset laser focal spot position P1 is determined by the wafer outline drawing defined by the laser cutting equipment grabbing drawing, and the maximum laser focal spot offset position P2 is determined according to the laser cutting equipment accuracy A, so that no matter how large the offset is, the gap 56 between the outer metal frame 50 and the inner metal frame 52 can be cut. In addition, FIG. 6A and FIG. 6B use a CO2 laser beam 1 with a smaller laser focal spot size and a larger laser focal spot size, respectively. Since the cutting path of the CO2 laser beam 1 must be able to cover the offset accuracy, if the laser focal spot size is too small, multiple CO2 laser beams 1 can be used to perform multiple cuts to achieve the same cutting effect.

To further illustrate, in step S30, the carbon dioxide laser cutting method provided by the embodiment of the present invention preferably satisfies the following conditions: Where LW is the line width of the internal metal frame (metal frame line width); is the accuracy of laser cutting equipment; S is the gap width.

For example, the accuracy of laser cutting equipment If the gap width S is set to ±100 microns (μm) and the gap width S is set to 30 μm, the line width of the inner metal frame can be set to 185 μm.

The present invention uses the gap between the outer metal frame and the inner metal frame to define the shape of the chip after cutting. The cutting accuracy of the chip shape depends on the design accuracy of the outer metal frame and the inner metal frame. Therefore, the line width LW and the gap width S of the inner metal frame can be set according to actual needs and are not particularly restricted. The cutting accuracy of the traditional carbon dioxide laser cutting process depends on the accuracy of the laser cutting equipment. However, the accuracy of laser cutting equipment The level of the laser cutting equipment used in the present invention is closely related to the price cost. The present invention can use general-grade and cheap laser cutting equipment to achieve the technical effect of high cutting accuracy. Compared with the traditional method, the present invention has a very large technical advantage. The laser cutting equipment used in the embodiment of the present invention has a high precision. The precision of the cutting process is 50 to 200 microns. Of course, the present invention is not limited to this in practice, and a laser cutting device with higher precision can also be used, but its price is relatively high.

Please refer to FIG. 7A and FIG. 7B, which are respectively the surface appearance pictures of the metal circuit 60 irradiated by the carbon dioxide laser cutting method provided by the present invention before and after surface cleaning. The carbon dioxide laser beam is irradiated along the cutting path P on the surface of the flexible substrate 30. The results show that the carbon dioxide laser beam used in the present invention will not damage the metal circuit 60 before surface cleaning (see FIG. 7A) and after surface cleaning (see FIG. 7B). It can be seen that the design of the external metal frame and the internal metal frame can effectively limit the scope of action of the carbon dioxide laser beam and obtain a higher cutting accuracy.

In summary, the carbon dioxide laser cutting method provided by the present invention is suitable for cutting a soft substrate into multiple chips, and can overcome the problem that the existing carbon dioxide laser cutting method causes edge melting of the substrate, resulting in poor cutting accuracy, and leading to reduced product performance and process yield. According to the carbon dioxide laser cutting method provided by the present invention, by taking advantage of the characteristic that the metal surface is less likely to absorb the wavelength of the carbon dioxide laser beam, an internal metal frame and an external metal frame are provided on the inner and outer sides of the cutting path, respectively, and the gap between the external metal frame and the internal metal frame is used to limit the range of action of the carbon dioxide laser beam. In this way, the present invention can break through the accuracy limitation of the laser cutting equipment itself, and can use general-grade and inexpensive laser cutting equipment to achieve the ability to have high cutting accuracy, which can avoid chip size defects, thereby improving the overall yield and production capacity. In addition, the present invention can further design the internal metal frame left after laser cutting into a grounding structure without adding additional process steps, thereby achieving process simplification and cost saving.

However, the above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications based on the features and spirit described in the scope of the present invention should be included in the scope of the patent application of the present invention.

1: CO2 laser beam 10: Substrate 12: Cutting path 20: Chip 30: Substrate 32: Cutting path 40: Chip 42: Sensing electrode layer 46: Connection pad 48: Ground pad 50: External metal frame 52: Internal metal frame 56: Gap 60: Metal line A: Laser cutting equipment accuracy A1: Action area A2: Frame area d1, d2, d3, d4: Distance LW: Line width of internal metal frame P: Cutting path P1: Default laser focus position P2: Maximum laser focus offset position S: Gap width S10: Step S20: Step S30: Step

FIG. 1A is a schematic diagram of a wafer after setting the cutting. FIG. 1B is a schematic diagram of a wafer with inconsistent size due to poor cutting accuracy in a prior art CO2 laser cutting method. FIG. 2 is a flow chart of the CO2 laser cutting method provided by an embodiment of the present invention. FIG. 3A to FIG. 3D are structural schematic diagrams corresponding to each step of the CO2 laser cutting method provided by an embodiment of the present invention. FIG. 4 is a partial enlarged diagram of the laser irradiation process of FIG. 3C. FIG. 5A and FIG. 5B are respectively a schematic diagram and a partial enlarged diagram of the specific structure of the wafer produced by the embodiment of the present invention. FIG. 6A and FIG. 6B are schematic diagrams of the cutting situation using a CO2 laser beam with different laser focal spot sizes in the CO2 laser cutting method provided by an embodiment of the present invention. Figures 7A and 7B are respectively the surface appearance images of the metal circuits irradiated before and after the surface cleaning using the carbon dioxide laser cutting method provided by the present invention. Figure 8 is a schematic diagram of the absorption of related wavelengths by different metals.

S10: Step

S20: Step

S30: Step

Claims (9)

A carbon dioxide laser cutting method comprises the following steps: (1) providing a flexible substrate having a plurality of cutting paths set on the surface and a plurality of chips divided by the cutting paths; (2) forming an outer metal frame and an inner metal frame around each of the chips, the outer metal frame being arranged along a side of the cutting paths away from each of the chips, the inner metal frame being arranged along a side of the cutting paths close to each of the chips, and a gap being sandwiched between the outer metal frame and the inner metal frame to expose a portion of each of the cutting paths; and (3) A carbon dioxide laser beam is used to irradiate along the cutting paths exposed to the gap, and the flexible substrate is divided into independent chips along the gap. The carbon dioxide laser cutting method, wherein each chip surface includes an active area and a frame area surrounding the active area, the outer metal frame is arranged on the cutting paths and extends along the outer side of the frame area, and the inner metal frame is arranged on the frame area and extends along the inner side of the cutting paths. In the step (2), a plurality of ground pads are formed in the frame area, and the ground pads are electrically connected to the inner metal frame, so that the inner metal frame serves as a ground wire. A carbon dioxide laser cutting method as described in claim 1, wherein the material of the outer metal frame and the inner metal frame is aluminum (Al), silver (Ag) or gold (Au). A carbon dioxide laser cutting method as described in claim 1, wherein the gap width is greater than or equal to the wavelength of the carbon dioxide laser beam. A carbon dioxide laser cutting method as described in claim 1, wherein the wavelength of the carbon dioxide laser beam is in the range of 9.2 to 9.7 microns or 10.2 to 10.7 microns. The carbon dioxide laser cutting method as described in claim 1 satisfies the following conditions: Wherein, LW is the line width of the inner metal frame; is the accuracy of the laser cutting equipment; S is the width of the gap. The carbon dioxide laser cutting method as described in claim 5, wherein the 50 to 200 microns. The carbon dioxide laser cutting method as described in claim 1, wherein in the step (2), it further includes forming a sensing electrode layer and a metal circuit layer in the active area and the frame area respectively, and the metal circuit layer is electrically connected to the sensing electrode layer. The carbon dioxide laser cutting method as described in claim 7, wherein in the step (2), it further includes forming a plurality of connection pads in the frame area, and the connection pads electrically connect the metal circuit layer and the sensing electrode layer. A carbon dioxide laser cutting method as described in claim 1, wherein the component material of the flexible substrate includes polyethylene terephthalate (PET), polypropylene (PP), polyimide (PI), polyamide (PA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyether sulphate (PES), polyprotoethylene (PNB), polyether ether ketone (PEEK), polyethylene naphthalate (PEN), cycloolefin polymer (COP) or cycloolefin copolymer (COC).