A method for manufacturing a circuit board laser drilling

Abstract

The application discloses a kind of manufacturing methods of circuit board laser drilling, first laser drilling processing is carried out using single-beam laser, and center hole is formed;The center hole is drilled and reamed by laser;The laser drilling and reaming processing is carried out using the same drilling and reaming laser beam as the aperture diameter and energy of the single-beam laser, according to the hole edge track of the center hole, and intersects with the center hole, and is uniformly distributed 6 times drilling, and laser aperture can be calculated by algorithm;The processing is carried out using the same aperture diameter laser beam full laser drilling method, first drilling center hole, then drilling surrounding reaming, can form energy highly consistent, form the drilling effect that the overlap ratio can completely cover center hole, high processing efficiency, algorithm is simple and reliable, can effectively prevent the problem that the hole wall roughness produced by mechanical processing is too large, the precision control of blind hole shape, depth and the like is insufficient.

Description

Technical Field

[0001] This invention relates to the field of circuit board design and manufacturing, and in particular to a method for manufacturing circuit boards using laser drilling. Background Technology

[0002] With the development of circuit board technology, the requirements for wiring density and circuit board integration are getting higher and higher. For high-density interconnect circuit boards, there are more and more types of blind via designs and more and more diversified processing methods.

[0003] Since blind holes are generally small-diameter holes, they are currently typically processed using laser drilling, which involves using a laser beam to ablate the substrate and create blind holes.

[0004] For blind holes with a large diameter (diameter > 0.25 mm), a single laser beam cannot meet the processing requirements of large holes. Currently, mechanical drilling with controlled depth is generally used for processing blind holes. However, mechanical drilling of blind holes is prone to problems such as excessive hole wall roughness and insufficient precision control of hole shape and depth, which affects subsequent processing and product quality. Furthermore, controlled depth drilling of blind holes has very high requirements for depth control precision. Generally, mechanical drilling is prone to problems of over-drilling or under-drilling.

[0005] Alternatively, a combination of mechanical drilling with controlled-depth drilling and laser finishing can be used. However, this method is essentially still mechanical drilling and is limited by the processing capabilities of laser processing. Considering the errors caused by misalignment during processing, this method is generally only suitable for making blind holes with a diameter of 0.1mm to 0.25mm. For blind holes with a diameter > 0.25mm, problems such as large processing deviations and irregular hole shapes are likely to occur.

[0006] Therefore, there is a need to provide a method for manufacturing blind holes with larger diameters using laser drilling, thereby providing high-quality blind hole circuit board products. Summary of the Invention

[0007] This invention aims to solve the problems of excessive hole wall roughness and insufficient hole precision control in existing technologies that use mechanical drilling or laser drilling combined with mechanical drilling to create large-diameter blind holes. It proposes a method for laser drilling circuit boards, characterized by the following steps: first, a single-beam laser is used for laser drilling to form a center hole; then, the center hole is enlarged using laser drilling. The enlargement process involves using a laser beam with the same aperture diameter as the single-beam laser, drilling six times at equal intervals along the edge trajectory of the center hole and intersecting with it. The aperture diameter is calculated as follows:

[0008]

[0009] In the formula:

[0010] D represents the aperture diameter of a single laser beam;

[0011] d represents the maximum hole radius in laser drilling and reaming.

[0012] A represents the distance that needs to be compensated on one side in laser drilling and enlarging processes;

[0013] p represents the overlap ratio between laser drilling, enlargement, and the center hole.

[0014] Furthermore, the algorithm for the maximum hole radius d is as follows:

[0015]

[0016] In the formula:

[0017] S represents the distance between the laser aperture of a laser drilling and enlarging process and the center of the laser aperture of the central hole.

[0018] Furthermore, the algorithm for the porosity p is as follows:

[0019]

[0020] Furthermore, the porosity p is 0.2 to 0.25.

[0021] Furthermore, the distance A that needs to be compensated on one side is between 1.5 mil and 3.0 mil.

[0022] Furthermore, the waveform of the laser is a Tophat waveform.

[0023] Furthermore, the aperture diameter of the laser is between 1.1 mm and 4.3 mm.

[0024] Furthermore, the energy of the laser is from 1.0 mJ to 18 mJ.

[0025] Furthermore, before performing laser drilling with a single laser beam, the circuit board is patterned. The patterning process involves applying dry film → exposure → development → etching → film removal to remove the copper layer of the circuit within the area to be formed by laser drilling.

[0026] Furthermore, the insulating dielectric layer material of the circuit board is epoxy resin glass fiber material, and the adhesive content of the epoxy resin glass fiber material is 50% to 65%.

[0027] This invention employs a full laser drilling method, using laser beams of the same aperture diameter to first drill the central hole, followed by the surrounding enlarged hole area. This results in highly consistent energy and a drilling effect where the overlap rate completely covers the central hole. Furthermore, using a laser of the same aperture diameter to process both the central hole and the enlarged holes eliminates the need for laser switching, effectively improving processing efficiency. The method utilizes one laser drilling of the central hole and six laser drilling of the enlarged holes, achieving optimal overlap rate consistency. Given the overlap rate, the maximum final hole diameter, and single-sided compensation, the appropriate laser aperture can be precisely calculated. This method significantly improves processing efficiency and effectively prevents problems such as excessive hole wall roughness and insufficient precision control of blind hole shape and depth caused by mechanical machining. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the machining structure for large-diameter blind holes using existing mechanical drilling methods;

[0030] Figure 2 This is a schematic diagram of the machining structure for processing large-diameter blind holes using an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram illustrating the laser aperture coverage effect during the processing of one central hole and six laser-expanded holes according to an embodiment of the present invention.

[0032] Figure 4 This is a schematic diagram illustrating the laser aperture coverage effect when using one central hole and seven laser-enlarged holes.

[0033] Figure 5 This is a schematic diagram illustrating the laser aperture coverage effect of processing one central hole and six laser-expanded holes according to another embodiment of the present invention.

[0034] Explanation of icon numbers:

[0035] label name label name 100X Existing technology drill bit 420 Internal stacked hole area 200X Existing technology circuit copper layer 110 Hole-enlarging laser beam 210X Existing technology insulating dielectric layer 300 blind hole 300X Existing technology blind holes 300A central hole 100 Center hole drilling laser beam D Aperture diameter of a single laser beam 200 copper layer of circuit d Maximum hole radius in laser drilling and enlargement 210 Insulating dielectric layer A Distance that needs to be compensated on one side 310 equilateral triangle p Overlap ratio of laser drilling, enlargement, and center hole 410 Peripheral stacked hole area S The distance between the center of one aperture laser aperture and the center aperture laser aperture

[0036] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0039] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] Please see Figure 1 ; Figure 1 This is a schematic diagram of the machining structure for processing large-diameter blind holes using existing technology with mechanical drilling.

[0041] In existing technologies, the fabrication of blind holes >0.25mm is generally achieved using a 100X drill bit for mechanical depth control drilling. Figure 1 As shown in Figure a, during processing, the copper layer 200X of the existing circuit can be drilled away directly without removing it, along with the insulating dielectric layer 210X, to form a blind via 300X. Figure 1 As shown in b.

[0042] Existing mechanical deep drilling methods for blind holes are prone to problems such as excessive hole wall roughness and insufficient precision control over the shape and depth of the blind hole.

[0043] Please see Figure 2 ; Figure 2 This is a schematic diagram of the machining structure for processing large-diameter blind holes using an embodiment of the present invention.

[0044] According to the embodiments of the present invention, the method for manufacturing a circuit board using laser drilling is as follows: first, the circuit board is patterned by applying dry film → exposure → development → etching → film removal; then, the copper layer of the circuit within the area to be laser-drilled is removed; and finally, a single-beam laser is used for laser drilling to form a center hole. Figure 2 a to Figure 2 As shown in b, the central hole drilling laser beam 100 is used to drill and ablate the insulating dielectric layer 210; then, the central hole is further drilled and enlarged using a laser drilling laser beam 110, as shown in Figure b. Figure 2 c to Figure 2 As shown in d.

[0045] Furthermore, the insulating dielectric layer material of the circuit board is epoxy resin glass fiber material, and the adhesive content of the epoxy resin glass fiber material is 50% to 65%. The insulating dielectric layer material with a higher adhesive content has better uniformity in blind hole processing and can reduce the problem of different ablation depths caused by the glass fiber in the material and the epoxy resin due to inconsistent melting points during laser drilling and ablation.

[0046] Of course, this embodiment can also be applied to laser drilling of other insulating dielectric materials, such as polyimide, polytetrafluoroethylene, PET, nano-ceramic powder composite epoxy resin, etc.; by adjusting the laser drilling parameters, it can be adapted to drilling of different materials.

[0047] Please see Figure 3 , Figure 3 This is a schematic diagram illustrating the laser aperture coverage effect of processing one central hole and six laser-expanded holes according to an embodiment of the present invention.

[0048] The laser drilling and enlargement process involves using an enlargement laser beam 110 with the same aperture diameter and energy as the central hole drilling laser beam 100. The laser beam 110 follows the edge trajectory of the central hole 300A and intersects with the central hole 300A, performing six drilling operations at equal and uniform intervals.

[0049] It should be noted that, after testing, using the same aperture diameter and energy of the center hole drilling laser beam 100 and the hole enlargement laser beam 110 can effectively achieve simultaneous processing of the center hole drilling and hole enlargement using the same laser beam parameters. There is no need to switch laser parameters in the middle (from center hole drilling to hole enlargement), which can effectively improve processing efficiency and improve the uniformity of laser drilling.

[0050] If the aperture diameter and energy of the expanding laser beam 110 are greater or less than those of the central hole drilling laser beam 100, the energy density of the expanding laser beam 110 will be either too low or too high when superimposed. This will make it difficult to match the energy uniformity with the central hole drilling laser beam 100, resulting in poor hole shape. Adjusting the expanding laser beam 110 may cause the drilling area to not completely cover the central hole or cover too much of the central hole, resulting in insufficient safety distance on one side of the covered area and poor hole shape. This will increase the number of times the parameters of the expanding laser beam 110 and the central hole drilling laser beam 100 are adjusted, which may easily lead to complex and erroneous parameter adjustments or omissions, and will also reduce processing efficiency.

[0051] When processing is done using a method where the aperture diameter and energy of the expanding laser beam 110 are equal to the aperture diameter and energy of the center hole drilling laser beam 100, the influence of the laser energy itself on the uniformity of drilling can be omitted, and only the relationship between the stacking density during the drilling process can be considered.

[0052] Based on the above rules, after testing, the method of drilling six holes at equal distances can form the simplest, most energy-efficient, and most efficient processing method of center hole drilling + enlargement drilling.

[0053] When the aperture diameter and energy of the expanding laser beam 110 are equal to those of the central hole drilling laser beam 100, the laser drilling and expanding process adopts a 6-stage drilling method with equal and uniform spacing. This can form an equilateral triangle 310 by connecting the centers of the apertures of one expanding laser beam 110, any adjacent expanding laser beam 110, and the central hole drilling laser beam 100. This ensures that the stacking rate of the central hole drilling laser beam 100 and the expanding laser beam 110 is equal, guaranteeing the consistency of drilling energy in the stacking area between adjacent expanding laser beams 110.

[0054] Please see Figure 4 , Figure 4 This is a schematic diagram of the laser aperture coverage effect when using one central hole and seven laser-expanded holes.

[0055] If one additional aperture-expanding laser beam 110 is added, it can be seen that the outer stacked hole area 410 formed by it is larger than the inner stacked hole area 420, that is, the density of the stacked holes on the periphery is greater than the density of the stacked holes on the inside (conversely, if the aperture-expanding laser beam 110 is reduced, the outer stacked hole area 410 will be smaller than the inner stacked hole area 420, which will result in poor uniformity of laser drilling, causing unevenness and deformation of the hole shape in both the longitudinal and transverse directions, thus affecting the drilling quality.

[0056] Please refer to it again. Figure 3Laser drilling and enlargement is performed using a 6-drilling method with equal and uniform spacing. The algorithm for calculating the stacking rate p is as follows:

[0057] ... (Equation 1)

[0058] p represents the overlap ratio between laser drilling and the center hole;

[0059] S represents the distance between the laser aperture of a laser drilling and enlarging process and the center of the laser aperture of the central hole;

[0060] D represents the aperture diameter of a single laser beam.

[0061] When the overlap ratio is large, the overlapping area of ​​adjacent laser beams is greater, and the ablation formed by the drilling will be deeper. Conversely, when the overlap ratio is small, the overlapping area of ​​adjacent laser beams is smaller, and the ablation formed by the drilling will be shallower.

[0062] After testing, it was found that for the processing of large blind holes on general circuit boards, the hole shape and drilling uniformity are best when the stacking ratio p is between 0.2 and 0.25. When the stacking ratio is large, the drilling is prone to over-burning. When the stacking ratio is large, the drilling will be under-burned, resulting in "plum blossom" shaped holes. The overlapping areas between the "petals" of the "plum blossom" are under-burned.

[0063] Please continue reading. Figure 3 ,Depend on Figure 3 The algorithm for determining the maximum hole radius d can be derived as follows:

[0064] ... (Equation 2)

[0065] d represents the maximum hole radius in laser drilling and enlargement.

[0066] Through testing, it was found that in the actual processing, there will be unavoidable precision shift problems in laser drilling, resulting in a certain degree of error in the size and distance of laser drilling. Therefore, it is necessary to design a certain unilateral compensation distance A to avoid the problem of laser drilling deviation and distortion caused by precision shift error.

[0067] It should be noted that in actual processing, the distance A that needs to be compensated on one side is generally selected to be between 1.5 mil and 3.0 mil, which can meet the tolerance range of accuracy shift error.

[0068] Based on Equations 1 and 2 above, and the distance A that needs to be compensated on one side in actual testing, the algorithm for the aperture diameter of the drilling laser can be obtained as follows:

[0069] ... (Equation 3)

[0070] A represents the distance that needs to be compensated on one side in laser drilling and enlarging processes;

[0071] p represents the overlap ratio between laser drilling, enlargement, and the center hole.

[0072] For example, when a blind hole with a maximum radius of 18.5 mil needs to be processed, and the stacking rate p is 0.25, and the distance A that needs to be compensated on one side is 2.5 mil, it can be calculated according to Equation 3 that a drilling laser with an aperture diameter of 12 mil is required for processing.

[0073] Please see Figure 5 , Figure 5 This is a schematic diagram illustrating the laser aperture coverage effect of processing one central hole and six laser-expanded holes according to another embodiment of the present invention.

[0074] It can be seen that by using a hole-expanding laser beam 110 with the same aperture diameter and energy as the central hole drilling laser beam 100, and following the hole edge trajectory of the central hole 300A and intersecting with the central hole 300A, six holes are drilled at equal distances. By adjusting the stacking ratio p, blind holes with different maximum hole radii d can be produced. The processing rules still follow the above algorithm process; however, it is necessary to adjust the stacking ratio p, as well as the aperture diameter and laser energy of the laser beam, to form the optimal drilling method.

[0075] In the process of laser drilling on circuit boards, the drilling effect is generally controlled by controlling the energy density and the laser beam. The energy density is generally adjusted by the distance between the collimator and the lens. The laser beam is generally adjusted by adjusting the size of the grating blockage. The two can be combined to adjust the laser beam that is most suitable for product processing.

[0076] In this embodiment, the aperture diameter of the laser is 1.1 mm to 4.3 mm, preferably 2.0 mm, 2.2 mm, 2.5 mm, 3.2 mm, or 3.8 mm; the energy of the laser is 1.0 mJ to 18 mJ, preferably 1.2 mm, 1.8 mm, 2.0 mm, 2.7 mm, 3.5 mm, 4.8 mm, 8.2 mm, 12.4 mm, or 17.0 mm.

[0077] Laser drilling equipment has different designs and working principles. In circuit board processing, the laser waveforms of commonly used laser drilling equipment are divided into Gauss waveform and Tophat waveform. The Tophat waveform is modified by a beam adjuster to transform the sharp wave shape of the Gauss waveform into the flat wave shape of the Tophat waveform, which can effectively improve the uniformity of energy density distribution. In this embodiment, the laser waveform is the Tophat waveform.

[0078] It can be seen that using this embodiment to process blind holes with a diameter > 0.25mm has comprehensive advantages such as high processing accuracy, high efficiency, good hole shape, and low energy consumption.

[0079] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing circuit boards using laser drilling, characterized in that, The manufacturing method is as follows: First, a single-beam laser is used for laser drilling to form a center hole; Before using a single-beam laser for laser drilling, the circuit board is patterned by applying dry film → exposure → development → etching → film removal to remove the copper layer of the circuit within the area to be formed for laser drilling. The central hole is then subjected to laser drilling and enlargement. The laser drilling and enlargement process involves using an enlargement laser beam with the same aperture diameter and energy as the single laser beam, drilling six times at equal intervals along the hole edge trajectory of the central hole and intersecting with the central hole. The algorithm for the aperture diameter is as follows: ， In the formula: D represents the aperture diameter of a single laser beam; d represents the maximum hole radius in laser drilling and reaming. A represents the distance that needs to be compensated on one side in laser drilling and enlarging processes; p represents the overlap ratio between laser drilling and the center hole; The formula for calculating the aperture diameter can be derived from the following formula. The algorithm for the maximum hole radius d is as follows: ， In the formula: S represents the distance between the laser aperture of a laser drilling and enlarging process and the center of the laser aperture of the central hole. The algorithm for the porosity p is as follows: ， The porosity p is 0.2 to 0.25; The distance A that needs to be compensated on one side is between 1.5 mil and 3.0 mil.

2. The method for manufacturing a circuit board using laser drilling as described in claim 1, characterized in that, The waveform of the laser is a Tophat waveform.

3. The method for manufacturing a circuit board using laser drilling as described in claim 1, characterized in that, The aperture diameter of the laser is between 1.1 mm and 4.3 mm.

4. The method for manufacturing a circuit board by laser drilling as described in claim 1, characterized in that, The energy of the laser is from 1.0 mJ to 18 mJ.

5. The method for manufacturing a circuit board by laser drilling as described in claim 1, characterized in that, The insulating dielectric layer material of the circuit board is epoxy resin glass fiber material, and the adhesive content of the epoxy resin glass fiber material is 50% to 65%.

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