A method, device, apparatus and system for through-hole drilling of a circuit board to avoid hole blockage

Abstract

The present invention relates to a method, device, apparatus and system for through-hole drilling of a circuit board to avoid hole blockage. The method includes: S1, using a first laser beam to process and remove the i-th layer of material layer to expose the (i + 1)-th layer of material layer, forming a first blind hole; S2, using a second laser beam to process and remove the (i + 1)-th layer of material layer in the first blind hole to expose the (i + 2)-th layer of material layer, forming a second blind hole; S3, setting i = i + 2, returning to S1, and repeatedly executing with S1 and S2 as a loop body until a through-hole is formed on the circuit board; wherein, the diameter of the laser processing spot of the first laser beam is less than 30 microns, and the diameter of the laser processing spot of the second laser beam is greater than 50 microns; the peak power density of the spot of the second laser beam is less than the laser cutting damage threshold of the odd-numbered material layer and greater than the laser removal damage threshold of the even-numbered material layer. The present invention can solve the problem of laser through-hole drilling of multi-layer circuit board materials containing various different insulating materials.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly relates to a method, device, apparatus and system for drilling through-holes in a circuit board to avoid hole blockage. Background Art

[0002] The laminated structure of the double-sided copper foil of a flexible printed circuit board (FPC) is generally "copper foil - polyimide film - copper foil". Common copper foil thicknesses are 12 μm, 18 μm, etc., and common polyimide film thicknesses are 12 μm, 20 μm, 25 μm, etc. After laser through-hole drilling of the double-sided copper foil of the FPC, residual glue substances (polyimide materials or their high-temperature denatured organic materials) will be left at the hole openings (entrance and exit) and inside the holes. These residual glue substances are the products of the ablation of polyimide in the flexible copper foil by the laser. When laser through-hole drilling a circuit board, since the processing of copper materials requires a relatively high peak power density, a relatively small focused processing spot is generally designed, and the spot is much smaller than the diameter of the through-hole to be drilled. Generally, a rotary cutting method is adopted. Due to the small laser focus spot, generally, the laser focus moves along the circumference of the through-hole on the copper foil surface to engrave grooves, and there are isolated islands in the middle of the grooves. Once the grooves penetrate through the circuit board material, the isolated island material in the middle of the through-hole finally leaks down from the inside of the through-hole. When the laser engraves grooves and drills holes by rotary cutting, the insulating material in the grooves is easily heated due to poor laser focusing characteristics, and the polyimide material denatures into residual glue. These residual glues will, at a certain time, stick the isolated island material in the hole, making the isolated island in the hole (residues of copper foil and insulator in the hole) unable to fall off. The material after the denaturation of polyimide has adhesive properties, and the laser cannot cut off these substances in the hole at this time, resulting in hole blockage during drilling. Hole blockage during drilling is a chronic problem in the field of laser through-hole drilling of flexible printed circuit boards, which is very troublesome and affects production capacity and yield. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method, device, apparatus and system for drilling through-holes in a circuit board to avoid hole blockage, which can solve the problem of laser through-hole drilling of multi-layer circuit board materials containing various different insulating materials.

[0004] In a first aspect, the present invention provides a method for drilling through-holes in a circuit board to avoid hole blockage. The method for drilling through-holes in a circuit board is used to drill through-holes in a circuit board. The circuit board is composed of n material layers stacked, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers;

[0005] The method for drilling through-holes in a circuit board includes the following steps,

[0006] S1. Use a first laser beam to process and remove the i-th layer of material on the circuit board, exposing the (i + 1)-th layer of material, and forming a first blind hole with the (i + 1)-th layer of material as the bottom; where the initial value of i is 1, i is an odd number, and i = 1, 3, …, n;

[0007] S2. Use a second laser beam to process and remove the (i + 1)-th layer of material in the first blind hole formed in S1, exposing the (i + 2)-th layer of material, and forming a second blind hole with the (i + 2)-th layer of material as the bottom;

[0008] S3. Let i = i + 2, return to S1, and loop and execute with S1 and S2 as the loop body until a through hole is formed on the circuit board;

[0009] Among them, the laser processing spot diameter of the first laser beam is less than 30 microns, and the laser processing spot diameter of the second laser beam is greater than 50 microns; the peak power density of the spot of the second laser beam is less than the laser cutting damage threshold of the odd material layer and greater than the laser removal damage threshold of the even material layer.

[0010] In a second aspect, the present invention provides a circuit board through-hole drilling device for avoiding hole blockage, and the circuit board through-hole drilling device is applied to the above-mentioned circuit board through-hole drilling method for avoiding hole blockage;

[0011] The circuit board through-hole drilling device includes a first laser emitter for emitting a first laser beam and a second laser emitter for emitting a second laser beam, and further includes a laser beam combiner and a galvanometer scanning and flat-field focusing device. The emission end of the first laser emitter and the emission end of the second laser emitter are both optically connected to the receiving end of the laser beam combiner, the output end of the laser beam combiner is optically connected to the input end of the galvanometer scanning and flat-field focusing device, and the output end of the galvanometer scanning and flat-field focusing device is used to output a combined laser beam;

[0012] The combined laser beam is used to drill a through hole in the circuit board. The circuit board is composed of n layers of material layers stacked, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers;

[0013] Specifically, the combined laser beam includes a first laser beam and a second laser beam;

[0014] The first laser beam in the combined laser beam is used to process and remove the i-th layer of material on the circuit board, exposing the (i + 1)-th layer of material, and forming a first blind hole with the (i + 1)-th layer of material as the bottom; where the initial value of i is 1, i is an odd number, and i = 1, 3, …, n;

[0015] The second laser beam in the combined laser beam is used to process and remove the (i + 1)-th layer of material in the first blind hole, exposing the (i + 2)-th layer of material and forming a second blind hole with the (i + 2)-th layer of material as the bottom;

[0016] The first laser beam and the second laser beam in the combined laser beam are used for layer-by-layer processing on the circuit board according to their respective functions until a through hole is formed on the circuit board;

[0017] Among them, the laser processing spot diameter of the first laser beam in the combined laser beam is less than 30 microns, and the laser processing spot diameter of the second laser beam in the combined laser beam is greater than 50 microns; in the combined laser beam, the peak power density of the spot of the second laser beam is less than the laser cutting damage threshold of the odd-numbered material layer and greater than the laser removal damage threshold of the even-numbered material layer.

[0018] In a third aspect, the present invention provides a circuit board through-hole drilling device for avoiding hole blockage, including a processor, a memory, and a computer program stored in the memory and operable on the processor. When the computer program runs, it implements the circuit board through-hole drilling method for avoiding hole blockage as described above.

[0019] In a fourth aspect, the present invention provides a circuit board through-hole drilling system for avoiding hole blockage. The circuit board through-hole drilling system includes a machine platform, and further includes the circuit board through-hole drilling device for avoiding hole blockage and the circuit board through-hole drilling equipment for avoiding hole blockage as described above. The circuit board through-hole drilling device is electrically connected to the circuit board through-hole drilling equipment;

[0020] The machine platform is used to carry the circuit board to be processed;

[0021] The circuit board through-hole drilling equipment is used to output a combined laser beam;

[0022] The circuit board through-hole drilling device is used to control the combined laser beam output by the circuit board through-hole drilling equipment to execute the circuit board through-hole drilling method for avoiding hole blockage as described above, and complete the through-hole drilling process of the circuit board placed on the machine platform.

[0023] The beneficial effects of the present invention are as follows: In a method, device, apparatus, and system for drilling through-holes in a circuit board to avoid hole blockage according to the present invention, the laser spot of the first laser beam for laser processing is relatively small (a certain laser peak power density is required to vaporize the metal), and the peak power is high, which can efficiently solve the problem of removing the material of the conductive material layer; if the first laser beam is used to remove the second insulating material layer, it will definitely directly penetrate the third material layer and cannot completely remove the insulating material inside the through-hole (a large spot is needed for cleaning). The second laser beam can be designed with a relatively large spot to efficiently remove the insulating material inside the through-hole of the circuit board, so that when the first laser beam removes the conductive material layer at the bottom of the second blind hole to form a through-hole, there is no insulating material inside the hole, and the material in the conductive material layer will not be adhered to the inside or the orifice of the hole, and there is no possibility of insulating material residues existing in the hole or at the orifice, perfectly solving the industry pain point of hole blockage in drilling through-holes of circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic structural diagram of a circuit board composed of three material layers;

[0025] Figure 2 FIG. is a schematic structural diagram formed after drilling the first material layer of the circuit board by a conventional method, where (a) is a top view and (b) is a cross-sectional view;

[0026] Figure 3 FIG. is a schematic structural diagram formed after drilling the second material layer of the circuit board by a conventional method, where (a) is a top view and (b) is a cross-sectional view;

[0027] Figure 4 FIG. is a schematic structural diagram formed after drilling the third material layer of the circuit board by a conventional method, where (a) is a top view and (b) is a cross-sectional view;

[0028] Figure 5 FIG. is a flowchart of a method for drilling through-holes in a circuit board to avoid hole blockage according to the present invention;

[0029] Figure 6 FIG. is a schematic structural diagram formed after drilling the first material layer of the circuit board by the through-hole drilling method of the present invention, where (a) is a top view and (b) is a cross-sectional view;

[0030] Figure 7 FIG. is a schematic structural diagram formed after drilling the second material layer of the circuit board by the through-hole drilling method of the present invention, where (a) is a top view and (b) is a cross-sectional view;

[0031] Figure 8Schematic diagram of the structure formed after drilling the third material layer of the circuit board using the through-hole drilling method of the present invention. Among them, (a) is a top view, and (b) is a cross-sectional view;

[0032] Figure 9 Block diagram of the structure of a circuit board through-hole drilling device for avoiding hole blockage according to the present invention;

[0033] Figure 10 Block diagram of the structure of a circuit board through-hole drilling system for avoiding hole blockage according to the present invention.

[0034] In the attached drawings, the list of components represented by each reference numeral is as follows:

[0035] 1. First material layer, 2. Second material layer, 3. Third material layer, 4. Slot hole, 5. Isolated island, 11. First blind hole, 21. Second blind hole, 31. Through hole. Detailed implementation manners

[0036] The principles and features of the present invention will be described below with reference to the attached drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0037] Traditional circuit boards are generally multi-layer structures formed by alternately stacking multiple conductive material layers and multiple insulating material layers. Assuming that the circuit board is formed by stacking n material layers, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers.

[0038] Figure 1 Schematic diagram of the structure of a circuit board composed of three material layers. In the circuit board, from top to bottom, there are the first material layer 1, the second material layer 2, and the third material layer 3 in sequence; among them: the first material layer 1 is a conductive material layer, specifically a copper foil with a thickness of 12 micrometers; the second material layer 2 is an insulating material layer, specifically a polyimide film with a thickness of 25 micrometers; the third material layer 3 is also a conductive material layer, specifically a copper foil with a thickness of 12 micrometers.

[0039] When drilling through holes in the Figure 1 shown circuit board, traditional laser through-hole drilling uses rotary cutting drilling. The laser focus rotates to form a circular slot hole. As shown in Figure 2 shown, during the process of the laser focus rotating on the first material layer 1, a slot hole 4 and an isolated island 5 are formed. At this time, the isolated island 5 includes the first material layer 1; the laser focus continues to rotate in the Figure 2 shown slot hole 4, and the slot hole 4 will deepen to form a structure as shown in Figure 3 shown. At this time, the isolated island 5 includes the first material layer 1 and the second material layer 2; the laser continues to rotate in Figure 3The slot 4 shown in the figure is cut inwardly, and after the slot 4 is penetrated, the island 5 loses its support and falls down, and then the slot 4 forms a through hole, forming a Figure 4 The structure shown. Figures 3 to 4 In the processing shown, once the insulating material in the slot 4 is thermally denatured, the island 5 will adhere to the hole, forming a hole blockage.

[0040] In actual through-hole drilling applications, there are often several blocked holes among tens of thousands of through holes, which requires all holes to be peeled several times more times, greatly reducing the through-hole drilling efficiency. This is a temporary situation where drilling production can be carried out under the premise that the laser focusing of the laser drilling machine is in good condition. In short, when the equipment is in good condition, increasing the number of peeling turns can solve some through-hole drilling blockages to a certain extent, but it also greatly reduces production efficiency, and the blockage will reappear at any time (the laser mode is getting worse and worse, the second layer of material is more and more severely denatured after heating, forming a sticky glue, the adhesion continues to increase and eventually the hole is blocked, and increasing the number of peeling turns does not work).

[0041] In the actual roll-to-roll through-hole drilling application, the unwinder is equipped with a copper foil coil, which is connected to the rewinder. The middle part is located on the working table of the laser drilling machine. When the laser drilling machine drills holes, the copper foil is adsorbed on the table to drill holes. After the drilling is completed, the table adsorption is released, and the rewinder rolls up the copper foil, finally forming a roll with holes drilled. In the actual through-hole drilling application, Figure 4 The island 5 shown in the figure, although it leaves its original position and forms a through hole, the copper foil of the island 5 that has been leaked often adheres to the vicinity of the through hole outlet. During the process of the coiler reeling the material, the copper foil of these islands 5 is also pressed into the coil, forming indentations. These indentations are a great defect for subsequent circuit plating and are not allowed. The copper foil indentation of the coiler is a stubborn problem of laser through-hole drilling. So far, there is no good solution. One or two adhesive rollers can only be added in front of the coiler to adhere the copper foil debris on the coil to the adhesive roller to reduce the indentation of the copper foil coiled material. So far, the indentation of the copper foil coiled material cannot be avoided.

[0042] In actual through-hole drilling applications, due to Figure 4 The residual insulating material in the slot 4 and the insulating material in the island 5 shown will partially adhere to the inside or the opening of the through hole and even the surface of the first layer material layer 1 and the third layer material layer 3, so adding plasma cleaning is generally a standard process after laser through hole drilling.

[0043] Based on the various defects caused by the conventional laser through-hole drilling described above, the present invention provides a circuit board through-hole drilling method, equipment, device and system that avoids hole blockage.

[0044] Embodiment 1:

[0045] A method for drilling through-holes in a circuit board to avoid hole blockage. The method for drilling through-holes in the circuit board is used to drill through-holes in the circuit board. The circuit board is composed of n stacked material layers, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers. A first laser beam and a second laser beam are used to perform laser through-hole drilling on the circuit board. Among them, the diameter of the laser processing spot of the first laser beam is less than 30 microns, and the diameter of the laser processing spot of the second laser beam is greater than 50 microns. The peak power density of the spot of the second laser beam is less than the laser cutting damage threshold of the odd material layer and greater than the laser cleaning damage threshold of the even material layer.

[0046] As Figure 5 shown, the method for drilling through-holes in the circuit board includes the following steps.

[0047] S1. Use the first laser beam to process and remove the i-th material layer of the circuit board, expose the (i + 1)-th material layer, and form a first blind hole with the (i + 1)-th material layer as the bottom. Among them, the initial value of i is 1, i is an odd number, and i = 1, 3,..., n.

[0048] S2. Use the second laser beam to process and remove the (i + 1)-th material layer in the first blind hole formed in S1, expose the (i + 2)-th material layer, and form a second blind hole with the (i + 2)-th material layer as the bottom.

[0049] S3. Let i = i + 2, return to S1, and execute S1 and S2 as a loop body in a loop until a through-hole is formed on the circuit board.

[0050] When n = 3, the process executed in the loop body is S1; when n = 5, the process executed in the loop body is S1 → S2 → S1; when n = 7, the process executed in the loop body is S1 → S2 → S1 → S2 → S1. That is to say, every time two more material layers are added to the circuit board, the loop process of S2 → S1 will be added once in the loop body.

[0051] In this specific embodiment, the specific steps for processing the Figure 1 shown circuit board using the method of the present invention are as follows:

[0052] The first step. Use the first laser beam to process and remove the first material layer 1 of the circuit board, expose the second material layer 2, and form a first blind hole with the second material layer 2 as the bottom.

[0053] The second step. Use the second laser beam to process and remove the exposed second material layer 2 in the first blind hole, expose the third material layer 3, and form a second blind hole with the third material layer 3 as the bottom.

[0054] In the third step, the third layer of material layer 3 exposed in the second blind hole is processed and removed by using the first laser beam to form a through hole.

[0055] In this embodiment, the first layer of material layer 1 is a conductive material layer, specifically a copper foil with a thickness of 12 micrometers; the second layer of material layer 2 is an insulating material layer, specifically a polyimide film with a thickness of 25 micrometers; the third layer of material layer 3 is also a conductive material layer, specifically a copper foil with a thickness of 12 micrometers.

[0056] In this embodiment, the first laser beam has a wavelength of 355 nanometers, a frequency of 100 kilohertz, an average laser power of 15 watts on the circuit board surface, a pulse width of 30 nanoseconds, and a focused spot of 20 micrometers.

[0057] In this embodiment, the second laser beam has a wavelength of 355 nanometers, a frequency of 100 kilohertz, an average laser power of 8 watts on the circuit board surface, a pulse width of 28 nanoseconds, and a laser spot of 100 micrometers on the circuit board surface.

[0058] The first laser beam Figure 1 mills a 100-micrometer hole in the first layer of material layer 1 of the shown circuit board to expose the second layer of material layer 2, forming a first blind hole 11 with the second layer of material layer 2 as the bottom. The specific structure after processing is as Figure 6 shown.

[0059] The second laser beam Figure 6 cleans and processes the second layer of material layer 2 at the bottom of the first blind hole 11 in [reference]. The second laser beam performs punching or rotary cutting scanning processing in the first blind hole 11 to obtain a second blind hole 21, exposing the third layer of material layer 3. The specific structure after processing is as Figure 7 shown.

[0060] The first laser beam Figure 7 performs rotary cutting processing on the bottom of the second blind hole 21 in [reference] to obtain a through hole 31. The specific structure after processing is as Figure 8 shown.

[0061] The core point of the present invention is to achieve non-blocked through-hole drilling by means of blind-hole drilling, ensuring that there is no insulating material in the blind hole before the through-hole is formed. Without insulating material, through-hole blockage will not occur. "If the skin is gone, where can the hair attach?" Single-layer pure copper foil laser spinning will not cause through-hole blockage, while for the copper foil of flexible printed circuit board with a sandwich structure containing an insulating layer, laser through-hole drilling is very likely to cause blockage, and the laser equipment needs to be in very good condition. The important reason is that the flexible printed circuit board copper foil contains insulating materials, and these insulating materials are thermally deformed when the copper foil is laser-spun and not fully carbonized, thus forming a gel-like substance and causing blockage. A small laser spot is very easy to penetrate the circuit board, and the insulating materials that are not vaporized by the laser are very likely to remain at the hole opening and inside the hole. It is difficult for a small-spot high-peak-power laser to remove the insulating substances inside the hole, and large-spot cleaning is required to efficiently remove the insulating materials at the bottom of the hole. Therefore, the present invention uses a first laser beam (small spot with high peak power density) to remove the material of the first conductive layer, and specifically designs blind-hole processing first during the laser through-hole drilling process. A second laser beam (large spot with low peak power density) removes the insulating material at the bottom of the blind hole without penetrating the formed blind hole, ensuring that there is no insulating material residue inside the blind hole, and then the first laser beam continues to complete the through-hole processing to achieve non-blocked laser through-hole drilling.

[0062] In other embodiments, the circuit board may have more than three layers of materials. The circuit board further has a fourth material layer and a fifth material layer. The fourth material layer is an insulating material layer, and the fifth material layer is a conductive material layer. The method of the present invention further includes the following steps:

[0063] After the first laser beam finishes processing the third material layer, the fourth material layer is exposed, forming a third blind hole with the fourth material layer as the bottom.

[0064] The second laser beam processes and removes the fourth material layer inside the third blind hole, forming a fourth blind hole with the fifth material as the bottom.

[0065] The first laser beam processes and removes the fifth material layer inside the fourth blind hole, forming a through-hole.

[0066] The peak power density of the laser processing spot of the second laser beam is less than the laser damage threshold of the fifth material layer and greater than the laser damage threshold of the fourth material layer.

[0067] If the circuit board has more structural layers, the processing is carried out by analogy until a through-hole is formed.

[0068] By using the method of the present invention, non-blocked laser through-hole drilling of more-layer circuit boards can be achieved.

[0069] Preferably, when the first laser beam processes and removes the odd-numbered material layers, it also partially removes the even-numbered material layers of the corresponding next layer; wherein, the partial removal is incomplete removal.

[0070] Since the ultimate goal is through-hole drilling, the first laser beam can pass through the second layer of material (insulating material layer) as long as the third layer of material does not peel off, providing conditions for the second laser beam in the second step to thoroughly clean the insulating layer material and form the second blind hole. If the blind hole conditions are not provided, the residue in the hole may leak to the through-hole outlet and block the hole opening, and the second laser beam will be powerless to remove the residue at the through-hole outlet. Specifically, the essence of the first blind hole is the "barrel" of a "gun" or "cannon" in the form of a "blind hole". The insulating layer material (the second layer of material 2) inside the "first blind hole" is equivalent to "gunpowder". The second laser beam has no damaging effect on the metal part of the first blind hole acting as the "barrel", but can vaporize and ignite the insulating material (the second layer of material 2) to form a plasma. Due to the effect of the "barrel", the spraying direction of this plasma is from the bottom of the first blind hole to the hole opening direction until the second blind hole is formed. There is no insulating material left in the second blind hole, and it is all vaporized clean by the second laser beam. This is why the technical solution of the present invention must form a blind hole. When removing the insulating material inside the blind hole, the metal bottom of the blind hole must exist. This is completely different from the traditional laser through-hole drilling. The traditional laser through-hole drilling cuts from the first layer of material to the third layer of material until it is cut through, and makes the isolated island 5 inside the cutting trajectory move away from its original position to form a through-hole.

[0071] Another embodiment of the method of the present invention is also introduced below.

[0072] In the first step, the first laser beam, with a laser focus diameter of 15 microns, a laser pulse repetition frequency of 60 KHz, a laser average power of 6 watts, a wavelength of 355 nm, and a pulse width of 25 nanoseconds, is used to perform rotary cutting on the first layer of material layer, removing the material (conductive material copper) in the first layer of material layer, with a hole opening diameter of 30 microns, forming the first blind hole and exposing the second layer of material layer (dielectric polyimide film).

[0073] In the second step, the second laser beam, with a spot diameter of 100 microns where the laser focus falls on the first blind hole, a laser pulse repetition frequency of 100 KHz, a laser average power of 8 watts, a wavelength of 355 nm, and a pulse width of 30 nanoseconds, directly punches at the first blind hole for 100 microseconds to form the second blind hole and expose the third layer of material layer (copper foil). The so-called punching means that the laser beam does not move relative to the copper foil and directly emits light to impact the area to be processed on the circuit board.

[0074] In the third step, the first laser beam directly performs rotary cutting and piercing on the bottom of the second blind hole according to the parameters for processing the first layer of material to form a through-hole.

[0075] At present, the production process of flexible printed circuit boards generally includes laser through-hole drilling, plasma cleaning, micro-etching, and other subsequent processes. Among them, plasma cleaning is very troublesome and costly, and has always been a headache in the field of flexible printed circuit boards. Since there is no residual polyimide film material in the second blind hole during the second step, and no colloidal substances will be generated during the processing of the copper foil in the third step, this method of through-hole drilling will not cause blockage of the holes, and at the same time, clean drilling is completed, and the laser cleaning is very clean.

[0076] Preferably, the second laser beam also participates in the processing process of the first laser beam at the same time. After the first laser beam partially removes the even material layer, the second laser beam completely removes the even material layer.

[0077] In order to completely remove the insulating material in the second blind hole, the second laser beam can melt and process the material at the bottom of the second blind hole. Since the through-hole is finally formed, the molten material at the bottom of the second blind hole will also be cut off.

[0078] Preferably, the conductive material in the conductive material layer contains copper, and the insulating material in the insulating material layer contains polyimide and / or glue.

[0079] This is the most common and most used double-sided copper foil material for flexible boards, and it is also relatively easy for this material to have blockage during laser through-hole drilling. By using the method of the present invention, the effect of non-blocking laser through-hole drilling of these materials can be achieved.

[0080] Preferably, the first laser beam and the second laser beam form a combined laser beam. In the combined laser beam, the dispersion degree of the laser processing spot of the first laser beam and the laser processing spot of the second laser beam is within a preset range (coincident or basically coincident); the through-hole drilling of the circuit board is carried out by controlling the light emission timing of the first laser beam and the second laser beam.

[0081] In the combined laser focus, the dispersion degree of the laser focus of the first laser beam and the laser focus of the second laser beam in the plane perpendicular to the beam transmission direction is less than 30 mm. Preferably, the center of the spot of the first laser beam is concentric or basically concentric with the center of the spot of the second laser beam. In this way, when processing the same hole position, the switching of the light emission and processing of the beam is more efficient and accurate.

[0082] For the technical solution of the present invention, the first blind hole and the second blind hole need to be processed first, and the combined laser focus can more easily and efficiently implement the present technical solution.

[0083] Specifically, when the first laser beam mills the first layer of material, the second laser beam can heat the first layer of material to improve the absorption rate and absorption stability of the first layer of material to the first laser beam. More specifically, the first laser beam performs grooving on the first layer of material, such as Figure 2 the shown slot hole 4. The second laser beam scans along the slot hole 4. After the material outside the slot hole 4 is heated, the heat is conducted away through the surface layer of the first layer of material. However, after the material inside the slot hole 4 is heated, the heat cannot dissipate. Coupled with the impact of the laser plasma in the slot hole 4, the first blind hole 11 can be efficiently formed.

[0084] Specifically, when the first laser beam performs tangential cutting on the bottom of the third layer of material at the bottom of the second blind hole 21, the second laser beam can heat the third layer of material to improve the absorption rate and absorption stability of the third layer of material to the first laser beam. Furthermore, the second laser beam synchronously performs laser cleaning on the first layer of material at the orifice of the through hole and the third layer of material at the bottom of the second blind hole, thoroughly ensuring the achievement of laser clean drilling.

[0085] Embodiment 2:

[0086] Based on the above method for drilling through holes in a circuit board to avoid blockage, the present invention also provides a device for drilling through holes in a circuit board to avoid blockage.

[0087] The device for drilling through holes in a circuit board to avoid blockage is applied to the above method for drilling through holes in a circuit board to avoid blockage;

[0088] As Figure 9 shown, the device for drilling through holes in a circuit board includes a first laser emitter for emitting a first laser beam and a second laser emitter for emitting a second laser beam, and also includes a laser beam combiner and a galvanometer scanning and flat-field focusing device. The emission ends of the first laser emitter and the second laser emitter are both optically connected to the receiving end of the laser beam combiner. The output end of the laser beam combiner is optically connected to the input end of the galvanometer scanning and flat-field focusing device. The output end of the galvanometer scanning and flat-field focusing device is used to output a combined laser beam;

[0089] The combined laser beam is used to perform through hole drilling on the circuit board. The circuit board is composed of n layers of material layers stacked, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers;

[0090] Specifically, the combined laser beam includes a first laser beam and a second laser beam;

[0091] The first laser beam in the combined laser beam is used to process and remove the i-th layer of material on the circuit board, exposing the (i + 1)-th layer of material and forming a first blind via with the (i + 1)-th layer of material as the bottom; where the initial value of i is 1, i is an odd number, and i = 1, 3, …, n;

[0092] The second laser beam in the combined laser beam is used to process and remove the (i + 1)-th layer of material in the first blind via, exposing the (i + 2)-th layer of material and forming a second blind via with the (i + 2)-th layer of material as the bottom;

[0093] The first laser beam and the second laser beam in the combined laser beam are used for layer-by-layer processing on the circuit board according to their respective functions until a through hole is formed on the circuit board;

[0094] Among them, the laser processing spot diameter of the first laser beam in the combined laser beam is less than 30 microns, and the laser processing spot diameter of the second laser beam in the combined laser beam is greater than 50 microns; in the combined laser beam, the peak power density of the second laser beam spot is less than the laser cutting damage threshold of the odd-numbered material layer and greater than the laser removal damage threshold of the even-numbered material layer.

[0095] In the present invention, the first laser beam and the second laser beam are combined by laser, and after being focused by the same set of galvanometer scanning and flat-field focusing devices, a combined laser focus is constructed.

[0096] Preferably, when the first laser beam in the combined laser beam is used to process and remove the odd-numbered material layer, it is also used to partially remove the corresponding even-numbered material layer in the next layer; where the partial removal is incomplete removal;

[0097] Or / and,

[0098] The second laser beam in the combined laser beam is also used to participate in the processing process of the first laser beam at the same time. When the first laser beam partially removes the even-numbered material layer, the second laser beam is specifically used to completely remove the even-numbered material layer.

[0099] The preferred solution of the equipment of the present invention can improve the processing efficiency of the first laser beam on the conductive material of the circuit board. The second laser beam can have a heating effect on the conductive material. The absorption of the first laser beam by the high-temperature conductive layer will be more stable and the absorption efficiency will also be higher. In order to completely remove the insulating material in the second blind via, the second laser beam can melt-process the material at the bottom of the second blind via. Since a through hole is finally formed, the molten material at the bottom of the second blind via will also be cut off.

[0100] Example three:

[0101] Based on the above method for drilling through-holes in a circuit board to avoid blockage, the present invention also provides a device for drilling through-holes in a circuit board to avoid blockage, including a processor, a memory, and a computer program stored in the memory and operable on the processor. When the computer program runs, it implements the above method for drilling through-holes in a circuit board to avoid blockage.

[0102] Embodiment 4:

[0103] Based on the above device and apparatus for drilling through-holes in a circuit board to avoid blockage, the present invention also provides a system for drilling through-holes in a circuit board to avoid blockage.

[0104] As Figure 10 shown, a system for drilling through-holes in a circuit board to avoid blockage includes a machine table, and also includes the above-mentioned device for drilling through-holes in a circuit board to avoid blockage and the above-mentioned apparatus for drilling through-holes in a circuit board to avoid blockage. The apparatus for drilling through-holes in a circuit board is electrically connected to the device for drilling through-holes in a circuit board;

[0105] The machine table is used to carry the circuit board to be processed;

[0106] The device for drilling through-holes in a circuit board is used to output a combined laser beam;

[0107] The apparatus for drilling through-holes in a circuit board is used to control the combined laser beam output by the device for drilling through-holes in a circuit board to perform the above-mentioned method for drilling through-holes in a circuit board to avoid blockage, and complete the through-hole drilling process of the circuit board placed on the machine table.

[0108] Specifically, the system for drilling through-holes in a circuit board to avoid blockage may further include necessary photographing devices, displacement devices, optical path devices, etc. for alignment.

[0109] The technical solution of the present invention for through-hole drilling without blockage has the following advantages compared with the traditional rotary cutting and grooving through-hole drilling:

[0110] 1. Avoid blockage

[0111] Before completing the through-hole drilling, the present invention first forms a first blind hole, and uses a second laser beam to thoroughly remove the insulating material in the first blind hole to form a second blind hole. When the first laser beam cuts through the second blind hole to form a through-hole, there is no adhesive material in the hole, thus avoiding the blockage phenomenon of the traditional through-hole drilling method.

[0112] 2. Clean drilling

[0113] There is no insulating material in the second blind hole of the present invention. When the first laser beam finishes rotary cutting the second blind hole, both the inside and the orifice of the through-hole are clean, and plasma cleaning is no longer required, reducing the plasma cleaning process with a very high cost in the traditional flexible board production process.

[0114] 3. High-efficiency drilling

[0115] When the first laser beam rotates and cuts the third material layer in the present invention, the second material layer has been avoided. In traditional laser through-hole drilling, the phenomenon that copper foil scraps adhere to the inner orifice of the through-hole in the second material layer no longer exists. It is not necessary to add several extra turns to ensure that all holes are drilled through. Therefore, the solution of the present invention can significantly improve the drilling efficiency.

[0116] 4. Avoiding coil indentation

[0117] When the first laser beam rotates and cuts the third material layer in the present invention, the second material layer has been avoided. In traditional laser through-hole drilling, the phenomenon that copper foil scraps adhere to the surface of the copper foil coil no longer exists, thus avoiding the chronic problem of coil indentation in roll-to-roll processing.

[0118] 5. Reducing the requirements for the focusing quality of the drilling laser

[0119] In traditional laser through-hole drilling, if the focusing quality of the drilling laser deteriorates, it will directly increase Figure 4 the degree of laser heating of the insulating material (the second material layer 2) on the inner and outer sides of the middle slot hole 4, resulting in a large number of blocked holes and the phenomenon that the through-hole cannot be drilled through. For the present invention, when the first laser beam has a deteriorated focusing quality, there is no insulating material during the processing of the first material layer, so the first material layer 1 can be effectively processed to form the first blind hole 11 without obstacles; when the second laser beam removes and vaporizes the insulating material (the second material layer 2) inside the first blind hole 11, since the cleaning and processing threshold of the insulating material is low, the requirements for the focusing quality of the second laser beam are not high, so the second blind hole 21 is also very easy to be processed and completed; when the second laser beam processes the material (the third material layer 3) at the bottom of the second blind hole 21, since there is also no insulating material, the third material layer 3 at the bottom of the second blind hole 21 can be effectively processed to form the through-hole 31 without obstacles. It can be seen from this that when the first laser beam processes the first material layer 1 and the third material layer 3, the second material layer 2 (insulating material) does not participate in the interaction between the laser and the substance, so there is no heating of the insulating material inside the through-hole to be processed by the first laser beam. Therefore, the requirements for the focusing quality of the first laser beam are reduced, greatly extending the maintenance cycle of the laser drilling machine and reducing the maintenance cost of the laser drilling machine.

[0120] Readers should understand that in the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0121] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for drilling through-holes in a circuit board to avoid hole blockage, characterized in that: The method for drilling through-holes in the circuit board is used to drill through-holes in the circuit board, and the circuit board is composed of n material layers stacked, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers; The method for drilling through-holes in the circuit board includes the following steps, S1. Use the first laser beam to process and remove the i-th material layer of the circuit board, expose the (i + 1)-th material layer, and form a first blind hole with the (i + 1)-th material layer as the bottom; where the initial value of i is 1, i is an odd number, and i = 1, 3, …, n; S2. Use the second laser beam to process and remove the (i + 1)-th material layer in the first blind hole formed in S1 without grooving, expose the (i + 2)-th material layer, and form a second blind hole with the (i + 2)-th material layer as the bottom; The second laser beam vaporizes and ignites the insulating material to form a plasma jet from the bottom of the first blind hole towards the hole opening until the second blind hole is formed, and there is no insulating material in the second blind hole; S3. Let i = i + 2, return to S1, and execute in a loop with S1 and S2 as the loop body until a blind hole with the last material layer as the bottom is formed; S4. Use the first laser beam to process and remove the last material layer of the circuit board in the blind hole with the last material layer as the bottom to form a through-hole on the circuit board, and the through-hole is a through hole; Among them, the laser processing spot diameter of the first laser beam is less than 30 microns, and the laser processing spot diameter of the second laser beam is greater than 50 microns; the peak power density of the spot of the second laser beam is less than the laser cutting damage threshold of the odd material layer and greater than the laser removal damage threshold of the even material layer; When the first laser beam processes and removes the odd material layer, it also partially removes the corresponding even material layer of the next layer; where the partial removal is incomplete removal.

2. The method for drilling through-holes in a circuit board to avoid hole blockage according to claim 1, characterized in that: The second laser beam also participates in the processing process of the first laser beam at the same time. After the first laser beam partially removes the even material layer, the second laser beam completely removes the even material layer.

3. The method for drilling through-holes in a circuit board to avoid hole blockage according to claim 1 or 2, characterized in that: The conductive material in the conductive material layer contains copper, and the insulating material in the insulating material layer contains polyimide.

4. The method for drilling through-holes in a circuit board to avoid hole blockage according to claim 1 or 2, characterized in that: The first laser beam and the second laser beam form a combined laser beam. In the combined laser beam, the dispersion degree between the laser processing spot of the first laser beam and the laser processing spot of the second laser beam is within a preset range; the through-hole drilling process of the circuit board is carried out by controlling the light output timing of the first laser beam and the second laser beam.

5. The method for drilling through-holes in a circuit board to avoid hole blockage according to claim 4, characterized in that: The discreteness between the laser processing spot of the first laser beam and the laser processing spot of the second laser beam is less than 30 microns.

6. A through-hole drilling device for a circuit board to avoid hole blockage, characterized in that: The through-hole drilling device for the circuit board is applied to the through-hole drilling method for the circuit board to avoid hole blockage according to any one of claims 1 to 5; The through-hole drilling device for the circuit board includes a first laser emitter for emitting a first laser beam and a second laser emitter for emitting a second laser beam, and also includes a laser beam combiner and a galvanometer scanning and flat-field focusing device. The emission ends of the first laser emitter and the second laser emitter are both optically connected to the receiving end of the laser beam combiner. The output end of the laser beam combiner is optically connected to the input end of the galvanometer scanning and flat-field focusing device. The output end of the galvanometer scanning and flat-field focusing device is used to output a combined laser beam; The combined laser beam is used for through-hole drilling of the circuit board. The circuit board is composed of n stacked material layers, where n is an odd number greater than or equal to 3, and the odd material layers of the circuit board are conductive material layers, and the even material layers of the circuit board are insulating material layers; Specifically, the combined laser beam includes a first laser beam and a second laser beam; The first laser beam in the combined laser beam is used to process and remove the i-th material layer of the circuit board, expose the (i + 1)-th material layer, and form a first blind hole with the (i + 1)-th material layer as the bottom; where the initial value of i is 1, i is an odd number, and i = 1, 3,..., n; The second laser beam in the combined laser beam is used to process and remove the (i + 1)-th material layer in the first blind hole without grooving, expose the (i + 2)-th material layer, and form a second blind hole with the (i + 2)-th material layer as the bottom; The second laser beam vaporizes and ignites the insulating material to form a plasma jet from the bottom of the first blind hole towards the hole opening until the second blind hole is formed, and there is no insulating material in the second blind hole; The first laser beam and the second laser beam in the combined laser beam are processed layer by layer on the circuit board according to their respective functions until a blind hole with the last material layer as the bottom is formed; The first laser beam in the combined laser beam processes and removes the last material layer of the circuit board in the blind hole with the last material layer as the bottom to form a through hole on the circuit board, and the through hole is a through hole; Among them, the diameter of the laser processing spot of the first laser beam in the combined laser beam is less than 30 microns, and the diameter of the laser processing spot of the second laser beam in the combined laser beam is greater than 50 microns; In the combined laser beam, the peak power density of the spot of the second laser beam is less than the laser cutting damage threshold of the odd material layer and greater than the laser cleaning damage threshold of the even material layer; When the first laser beam processes and removes the odd material layer, it also partially removes the corresponding even material layer of the next layer; where the partial removal is incomplete removal.

7. The through-hole drilling device for a circuit board to avoid hole blockage according to claim 6, characterized in that: The second laser beam in the combined laser beam is also used to simultaneously participate in the processing process of the first laser beam. After the first laser beam partially removes the even material layer, the second laser beam is specifically used to completely remove the even material layer.

8. A through-hole drilling device for a circuit board to avoid hole blockage, characterized in that: It includes a processor, a memory, and a computer program stored in the memory and running on the processor. When the computer program runs, it implements the through-hole drilling method for a circuit board to avoid hole blockage according to any one of claims 1 to 5.

9. A through-hole drilling system for a circuit board to avoid hole blockage, characterized in that: It includes a machine table, and also includes the through-hole drilling device for a circuit board to avoid hole blockage according to claim 6 or 7 and the through-hole drilling device for a circuit board to avoid hole blockage according to claim 8. The through-hole drilling device for a circuit board is electrically connected to the through-hole drilling device for a circuit board; The machine table is used to carry the circuit board to be processed; The through-hole drilling device for a circuit board is used to output a combined laser beam; The through-hole drilling device for a circuit board is used to control the combined laser beam output by the through-hole drilling device for a circuit board to execute the through-hole drilling method for a circuit board to avoid hole blockage according to any one of claims 1 to 5, and complete the through-hole drilling process of the circuit board placed on the machine table.

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