A method for removing plated process leads with a laser

Abstract

The application discloses a method for removing electroplating process wires by laser, comprising the following steps: step (1), according to the state of the existing process wires after electroplating, designing reasonable half-cut laser processing path and hot-pressing laser processing path; step (2), according to the half-cut laser path, cutting the metal layer of the process wires by laser, and basically not damaging the underlying substrate; step (3), according to the hot-pressing laser processing path, using the thermal effect of laser to heat the process wires, and then reducing the adhesion between the process wires and the substrate, and meanwhile, a certain positive pressure blowing or / and negative pressure suction is used to make the process wires separate from the substrate. The method does not need traditional manual picking to remove the process wires, does not need secondary etching, has no protective material coating process, and can adopt laser direct stripping to remove the process wires; the method is accurate in positioning, has no burr on the edge, has no side etching, is good in consistency, is high in processing efficiency, is low in cost, and is simple in operation, and is low in skill requirement for employees.

Description

Technical Field

[0001] This invention relates to the field of laser manufacturing of electronic circuits, specifically a method for removing electroplated wires using a laser. Background Technology

[0002] In the electroplating industry (here, electroplating refers to traditional electroplating with cathodes and anodes, excluding electroless electroplating of the chemical type), different components have different surface characteristic requirements. Some components require plating characteristics on all parts, which is called bulk electroplating. Other components require plating characteristics on some parts and substrate characteristics on others; this is called selective electroplating. In selective electroplating, if the parts requiring plating characteristics are continuous, within a current network, and this current network can be easily connected to the cathode clamping point, then selective electroplating can be easily performed by connecting the cathode. However, if the parts requiring plating characteristics are discontinuous, containing many networks, and many of these networks cannot be connected to the cathode clamping point, there are usually two solutions: one is to perform bulk electroplating first, followed by selective etching; the other is to use process leads to connect all the networks and then converge them to the cathode clamping point. Clearly, the first method requires more plating metal, and the cost is high if precious metals are used. The second method uses less plating metal and reduces electroplating time, but it brings another problem: the process wires connecting the network need to be removed after electroplating. Early methods for removing process wires involved manually picking them out with a knife. However, this method was inefficient, required a large workforce, and was prone to scratches. Furthermore, the removal of the wire's graphic ends was inaccurate, resulting in low yield and poor product consistency for precision components. Later, some manufacturers used a secondary etching method to remove process traces, mainly PCB manufacturers. This involves selectively gold-plated products (including gold-plated connectors) undergoing a second dry film coating, exposure, development, and etching. This method improves consistency and, for large batches, is more efficient than manual etching. However, this method is essentially double-sided board manufacturing, resulting in high costs. Furthermore, the expansion and contraction of the substrate or film can cause inaccurate positioning of the trace ends, and side etching can lead to uneven etching surfaces. The added length of the process can also damage already processed areas. Therefore, this method is unsuitable for some high-requirement products or results in very low yields (such as high-frequency microwave boards). Additionally, the secondary etching method uses chemical solutions for different processes like development, etching, and film removal, which contradicts the national green and environmentally friendly principles. FPC manufacturers typically choose to add a first-pass etching step for process traces, but this method leaves some traces on the product. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for removing electroplated process wires using a laser. This method eliminates the need for traditional manual removal of process wires, secondary etching, and protective material coating. It directly removes the process wires using a laser, employing a completely dry process that is environmentally friendly. It avoids chemical processes and manual removal of process wires, thus preventing damage from human intervention. This method offers precise positioning, burr-free edges, no side etching, good consistency, high processing efficiency, and low cost. It is suitable for both small-batch production and large-scale factory use; moreover, the operation is simple and requires minimal employee skills.

[0004] A method for removing electroplated wires using a laser, the specific steps of which are as follows:

[0005] (1) Based on the state of the existing process wires after electroplating, design the half-cut laser processing path and the hot stamping laser processing path;

[0006] (2) By using the half-cut laser path in step (1), the beginning and end of the process wire are half-cut to separate the metal layer of the process wire from the surrounding metal layer and reduce the damage to the substrate of the lower layer.

[0007] (3) Following the hot-stamping laser processing path, the thermal effect of the laser is used to heat up the process wires and reduce their bonding force with the substrate. At the same time, positive pressure blowing and / or negative pressure suction are used to detach the process wires from the substrate.

[0008] Preferably, in the laser processing path design stage of step (1), the overall distribution of the process wire is automatically decomposed into single process wires without intersection by software, and the precision end half-cutting processing path and the rough end half-cutting processing path of the single process wire are defined according to the characteristics of the beginning and end of the single process wire and the required processing accuracy. Then, the following three hot stamping laser paths are generated on the single process wire according to the characteristics of the single process wire: a) a single hot stamping laser path from the precision end to the rough end; b) a single hot stamping laser path from the rough end to the rough end; c) a double hot stamping laser path from the precision ends at both ends to the middle position of the length direction of the process wire.

[0009] Preferably, the precision end half-cutting processing path generated in step (1) is characterized by being located at the midpoint of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide, moving a certain distance towards the process guide. This certain distance is half the diameter of the light spot, or any value between 0 and 10 light spot diameters. Its length is characterized by being the length of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide minus the reduction amount of etching, and then adding the length of the R-angle radius formed after etching to both ends. The reduction amount of etching and the R-angle radius need to be determined according to the thickness of the metal layer and the process capability of the etching line. When the line connecting the intersection is a straight line and perpendicular to the process guide, the length of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide is the width of the process guide.

[0010] Preferably, the rough end-half-cutting processing path generated in step (1) has the following characteristics: the rough end-half-cutting processing path is not displayed on the final product graphic after the process wire is removed; the half-cutting laser processing path is outside the product outline or in the middle of the through-cut inner groove or large hole; its length characteristics are: after intersecting with a single process wire, each end is extended by a certain length, and the certain length is any value within 0-10mm.

[0011] Preferably, the hot stamping laser processing path generated in step (1), if it is of the type from precision end to coarse end, has the following position characteristics: the midpoint of the laser path half-cut at the precision end moves a certain distance toward the process guide, which is half the diameter of the spot or any value within 0-0.5mm; the position characteristics of the coarse end are: the midpoint of the laser path half-cut at the coarse end moves a certain distance toward the precision end (i.e., the negative direction) or away from the precision end (i.e., the positive direction), which is any value within -0.2-100mm.

[0012] Preferably, the hot heat laser processing path generated in step (1), if it is of the type from coarse end to coarse end, has the following positional characteristics of the two coarse ends: the midpoint of the half-cut laser path at the coarse end moves a certain distance in the direction of the midpoint of the process guide length, i.e., the negative direction or away from the midpoint, i.e., the positive direction. This certain distance is any value within the range of negative 0.2-100mm.

[0013] Preferably, if the hot stamping laser processing path generated in step (1) is of the precision end-to-precision end type, then two hot stamping laser paths are generated. Both paths start from their respective precision ends and end at a certain position in the middle of the process guide along the centerline of the process guide. The positional characteristics of the two precision ends are that the midpoint of the half-cut laser path of each precision end moves a certain distance in the direction of the process guide. This certain distance is half the spot diameter, or any value within 0-0.5mm. The endpoints of the two hot stamping laser paths are a certain distance to the left and right of the midpoint of the process guide centerline, or a certain distance to the left and right of a point moved a certain length before or after the midpoint. The distance between the two hot stamping paths is such that they do not intersect, and the distance is equal to the diameter of a laser spot, or any value within 0-1mm. This "fixed length" refers to the fact that the lengths of the two hot stamping paths may not be equal, and can be any value from 0 to the length of the process guide. If it is 0 or the length of the process guide, then the two hot stamping paths are actually one hot stamping laser path. The length of the end of the two hot stamping laser paths and the line connecting the beginning and end are continuous straight lines, or broken lines with a certain angle to the two outwards. This "fixed length" is any value within 0-10mm, and the "fixed angle" is such that the vertical length of the two endpoints after the angle from the nearest edge of the process guide is any value within 0.25-0.5 times the width of the process guide.

[0014] Preferably, in step (2), the process wire half-cutting stage is performed, especially for the precision end processing. The laser temperature needs to be controlled at a low temperature so that the laser can penetrate the process wire without burning through the substrate. This low temperature refers to the low temperature process when cutting the upper metal layer. According to the characteristics of the material, a lower wavelength, lower pulse width, lower duty cycle, higher interval time, and lower power are selected for the laser output. The lower wavelength range is any value within 1064nm-0nm, the lower pulse width range is any value within 100ns-10fs, and the lower duty cycle range is 0.5%-0.1pp. Any value within the range of m, with a higher interval time range of 0-10s and a lower power range of 0.05-100W; the laser penetration process means that the upper metal layer is cut through without burning through the substrate, thus reducing damage to the substrate. A suitable light source must be selected based on the characteristics of the material being processed. Given the high absorption rate of the upper metal layer and the low absorption rate of the lower substrate, a suitable process must be chosen, such as using low power and multiple passes for half-cuts. When the substrate layer is reached, the laser machine detects the change in cutting speed and reduces the power or stops processing.

[0015] Preferably, in step (2), the process guide semi-cutting stage is characterized by the following positioning method: using the positioning points designed in step (1) for overall positioning, and using the semi-cutting path generated in step (1) for continuous processing of the whole board; or using the positioning points designed in step (1) for overall positioning, and then each single process guide is positioned again; the positioning sequence is: first, determine the position of the fine end path, and the coarse end automatically follows; the positioning of the fine end is determined by human eye positioning or equipment edge-finding positioning; in equipment edge-finding positioning, the equipment CCD automatically finds the boundary between the metal and the substrate according to the different colors of the metal and the substrate, and according to the process guide The initial start and end points of the precision end cutting path are found at the two intersection points of the two boundary straight lines and the two boundary straight lines or curves of the product graphic. Then, based on the measured radius of the two ends of the R-angle, after a certain correction, the initial start and end points are extended to the second start and end points. The current entire path is then translated a certain distance in the direction of the process guide with the midpoint as the reference, which is used as the actual precision end half-cutting path. The certain correction of the R-angle radius is any value between -0.5R-angle radius and +0.5R-angle radius. The certain distance that the midpoint is translated in the direction of the process guide is half the spot diameter, or any value within 0-0.5mm. This calculation process is automatically completed by the equipment driving software.

[0016] Preferably, in step (3), the hot-heat laser processing stage is characterized by the need to control the laser temperature to be high so that the laser heats the process wires without melting the process wires and substrate. The high temperature refers to the use of the laser's thermal effect in the selection of the laser and the selection of process parameters. The laser parameters are selected according to the characteristics of the material, including: a longer wavelength, a larger pulse width, a higher duty cycle, and a stronger power. The higher wavelength is any value within the range of 355nm-10640nm, the longer pulse width is any value within the range of 10ps-10μs, the higher duty cycle is any value within the range of 1ppm-100%, and the stronger power is any value within the range of 0.1W-1000W. The fact that the process wires and substrate are not melted means that the metal layer heats up and expands after absorbing heat, but cannot melt. Therefore, the power density of the heat-heating laser needs to be selected according to the type and thickness of the material. The goal is to make the temperature rise of the metal layer as high as possible to increase the expansion tension, while preventing it from melting and softening and losing tension.

[0017] Preferably, in step (3), during the hot stamping laser processing stage, the laser spot diameter should be close to the width of the process wire; this closeness is any value ranging from 0.5 to 1.2 times the width of the process wire; if the spot diameter is too small, it will cause uneven heating in the width direction of the process wire and the expansion tension will be constrained; while if the spot diameter is too large, it will cause the substrate on both sides of the process wire to be burned; for process wires of different widths, the spot diameter should be adjusted manually or automatically by the equipment to a suitable size.

[0018] The advantages and technical effects of the method for removing electroplated wires using a laser according to the present invention mainly include the following:

[0019] 1. High precision: The machining accuracy of precision-end components is typically within 10μm. Equipped with a high-resolution CCD, it is easy to achieve 5μm, and this precision will continue to improve with future hardware advancements. This increased precision has made many high-frequency, high-speed products that were previously unmanufacturable possible.

[0020] 2. High yield rate and good consistency of laser processing. Once the first sample is qualified, the consistency of subsequent processed products is very high, resulting in a high yield rate. This is better than the uncertainty of manual picking and also better than the uncertainty caused by the instability of temperature, pressure and concentration of chemicals in each process of secondary etching.

[0021] 3. High efficiency: Laser removal of conductive lines operates on one or two consecutive machines, resulting in a short process flow. This is unlike the lengthy process of secondary etching, which involves film application, alignment, exposure, development, etching, and film removal. Therefore, the overall efficiency is high, and it is even more efficient than manual removal.

[0022] 4. Low cost: Due to the high yield rate, high processing efficiency, and short process flow of laser-based wire removal, the overall cost of laser-based wire removal is relatively low.

[0023] 5. Environmentally friendly: Compared with secondary etching, laser removal of wires does not involve a large amount of acid and alkali treatment, which is beneficial to improving the working environment for employees and is in line with the national concept of green development.

[0024] 6. Reduced operational difficulty: Both manual picking and secondary etching require a high level of skill from operators, including techniques for picking, direction, and force; control of numerous process parameters such as temperature and pressure of the secondary etching solution; control of process transfer; and techniques for reworking defective products. However, the original processing data for laser-guided wire removal is automatically generated by CircμitCAM software, and the positioning and cutting during the process are performed automatically by the laser equipment. Operators have minimal intervention, resulting in lower skill requirements. Attached Figure Description

[0025] Figure 1 The pattern and wiring distribution of a conventional surface-gold plated microwave circuit board.

[0026] Figure 2 The laser processing paths for half-cutting and hot stamping are calculated using CircμitCAM software. Because the calculated laser paths overlap with the original graphic, the original data is displayed as outlines.

[0027] Figure 3 Enlarged detail view of area A, showing a single process conductor of precision-to-coarse end type.

[0028] Figure 4 The enlarged view of area B shows three individual process conductors: two are precision-to-coarse type, and one is coarse-to-coarse type.

[0029] Figure 5 Enlarged view of area C, precision end-to-precision type, dual heat transfer path.

[0030] Figure 6 The laser processing of half of area A is completed.

[0031] Figure 7 Hot heat laser processing completed in area A

[0032] Figure 8 The entire laser removal process for all wires has been completed, including 12 areas of precision to rough machining, 3 areas of rough machining, and 1 area of ​​precision to precision machining.

[0033] Figure 9 Distribution of process wires after gold plating of FR4 board gold plug

[0034] Figure 10 The CircμitCAM software automatically calculates the half-cut laser path and the hot-pressing laser path. To facilitate viewing the laser path, process guide lines are displayed using outlines.

[0035] Figure 11 Detailed magnified view of region D

[0036] Figure 12 Region D half-cut laser processing completed

[0037] Figure 13 Area D hot stamping laser processing completed

[0038] Figure 14 The entire laser removal process for wire fabrication is now complete. Detailed Implementation

[0039] To further understand the content, features, and effects of this invention, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings. It should be noted that these embodiments are descriptive, not limiting, and should not be construed as limiting the scope of protection of this invention.

[0040] The present invention discloses a method for removing electroplated process wires using a laser, illustrated as follows: Overall positioning holes 1 (four in total); outer conductive strip 2 (can be a copper-lay structure between single PCS in a multi-panel board, ultimately connecting to the cathode clamping point); product outer contour line 3; product inner contour line 4 (the final product is a ring structure); product conductive pattern 5 (including circular rings, square blocks, and rectangular strips without connecting middle sections); through-cut inner groove 6 (cut off in the final product, 7 locations in total); process wire 7 (4 entry points of the outer conductive strip in the figure); precision end half-cut path 8 (slightly longer than the width of the process wire); coarse end half-cut path 9 (can be longer than...). (The process guide is slightly longer); Hot stamping laser path 10 (from the precision end to the coarse end); Coarse end half-cut path 11 of a single process guide on the right (coinciding with the edge of the vertical process guide); Precision end half-cut path 12 of a single process guide on the left; Half-cut path 13 from vertical coarse to coarse process guide (only one); Precision end to precision end process guide 14; Double hot stamping laser path 15 (from both ends to the middle); Upper precision end half-cut path 16; Insulation strip after precision end half-cut processing 17; Insulation strip after coarse end half-cut processing 18; Process guide after end insulation 19; Gold fingers of FR4 product 20.

[0041] The present invention discloses a method for removing electroplated process wires using a laser, the overall steps of which are as follows: Step (1), based on the state of the existing process wires after electroplating, design a reasonable half-cut laser processing path and a hot-scalding laser processing path; Step (2), according to the half-cut laser path, use a laser to cut the metal layer at both ends of the process wires just enough to avoid damaging the underlying substrate; Step (3), according to the hot-scalding laser processing path, use the thermal effect of the laser to heat up the process wires and reduce their bonding force with the substrate, while simultaneously using a certain positive pressure blowing or / and negative pressure suction to detach the process wires from the substrate.

[0042] In addition, the preferred embodiment of the present invention, "half-cut" refers to a fixed-depth processing mode in which the metal layer is cut open but not completely cut through, and does not mean that the exact processing depth is 50% of the total depth of the material.

[0043] The detailed steps are as follows:

[0044] Step (1): Based on the state of the process wires after electroplating, design a reasonable half-cut laser processing path and a hot stamping laser processing path.

[0045] First, let's define two terms: Semi-cut laser processing refers to the process of cutting the surface metal along the width direction at both ends of a process guide using appropriate laser parameters and the laser's cutting function, while minimizing or completely avoiding damage to the underlying substrate. The path taken during semi-cut laser processing is called the semi-cut laser processing path. Hot-stamping laser processing refers to the process of heating the process guide from one end to the other using appropriate parameters and the laser's thermal effect, after semi-cut laser processing has broken off at both ends. The path taken during hot-stamping is called the hot-stamping laser path.

[0046] The path generation in this process is automatically generated using an existing PCB file with process traces on a PCB manufacturing software called CircuitCAM.

[0047] Since process leads typically connect one end to the metal pattern required for the product and the other end to the cathode clamping point, the end connecting to the metal pattern generally has higher requirements in terms of position, depth, length, and appearance. The end connecting to the cathode clamping point is usually not inside the finished product and is removed when the product is finally milled, milled with internal grooves, or drilled with large holes. Therefore, the requirements for this end are not high. Thus, this patent defines the end of the process lead connecting to the metal pattern required for the product as the precision end, and the end that is milled away or has lower requirements as the coarse end.

[0048] For a slightly more complex electroplating product, the overall process leads are usually networked and intersecting. CircuitCAM software can automatically divide the intersecting overall process leads into individual process leads that do not intersect each other. Based on the definition of precision end and coarse end, it can automatically configure the half-cut laser path of precision end and the half-cut laser path of coarse end. At the same time, it can automatically configure the hot stamping laser path with the direction from precision end to coarse end or from precision end at both ends to the middle.

[0049] The precision-end half-cut laser path is positioned at the root of the intersection of the process guide and the patterned metal, moving a certain distance towards the process guide. Theoretically, this distance is half the laser spot diameter, but it needs to be adjusted based on product precision requirements and equipment positioning capabilities, typically between 0 and 10 laser spot diameters. The length of the precision-end half-cut laser path is the length of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide, minus the etching reduction, and then adding the radius of the rounded corner formed after etching to both ends. The etching reduction and the rounded corner radius can be determined within a reasonably accurate range based on the metal layer thickness and the etching line's processing capabilities. In a special case, if the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide is a straight line perpendicular to the process guide, then this length is the width of the process guide. The semi-cut laser path at the precision end can be directly used with the path automatically generated by CircuitCAM software, or the path automatically generated by CircuitCAM software can be used as an approximate position. Based on the approximate positioning, the device's CCD can be used for secondary edge finding and positioning to generate a new semi-cut laser path at the precision end, or the start and end points of the original path can be modified to form a modified semi-cut laser path at the precision end.

[0050] The coarse-cut laser path is located outside the product's outline, inside the internal through-cut groove, or inside the non-metallized hole—basically, the part to be removed. Therefore, only the metal layer of the process conductor needs to be cut; damage to the underlying substrate has little impact, and cutting slightly at the top or bottom has minimal effect. Positional accuracy requirements are also lower. Therefore, the coarse-cut end is usually slightly wider than the width of the process conductor, for example, 1.1-1.5 times, to facilitate removal. Edge-finding positioning is not required for the coarse-cut end; the path automatically generated by CircuitCAM software can be used directly.

[0051] The hot stamping laser path is typically a straight line equidistant from the top and bottom edges of a long strip of process wire. The near-equidistant distance ensures the entire process wire is heated. If one side receives more heat than the other, the side receiving less or no heat may not detach, while the side receiving more heat may discolor the substrate. The processing direction of the hot stamping laser path is from the precision end to the coarse end. This is because the heating of the metal varies and gradually increases as the laser travels from the beginning to the end. The initial heating is entirely due to the continuous energy emitted by the laser beam. Part of this energy is used to heat the metal directly below the laser beam, and the rest is conducted towards the end. Since the semi-cutting process is completed during hot stamping, the individual metal process wire is disconnected from the surrounding metal. Therefore, the closer to the end, the more energy accumulates, increasing the probability of substrate burns. Because the coarse end has lower quality requirements, processing from the precision end to the coarse end is preferable. Furthermore, the precision end of the hot stamping path, i.e., the starting end, usually does not begin from the midpoint of the precision half-cut path. It must be separated by a certain distance, such as half the spot diameter to within 0.5mm. This is because if the hot stamping path intersects with the precision half-cut path, the energy at the intersection will definitely be greater than the energy of the half-cut laser, potentially causing discoloration of the patterned metal or the underlying substrate. The coarse end of the hot stamping laser path can intersect with the coarse half-cut path; this intersection allows for easier detachment.

[0052] A single process conductor, after being segmented by CircuitCAM, typically has one precision end and one coarse end, which is the most common form. Some conductors have coarse ends at both ends, which is the easiest to process. Others have precision ends at both ends, in which case a dual-path hot stamping system should be used. Specifically, two hot stamping paths start from the two precision ends and end in the middle, but the ends of the two paths do not overlap; they should be spaced a certain distance apart, or each should make a bend outwards beforehand. This method avoids damaging the substrate when the two hot stamping paths intersect. If the length of a single process conductor is not very long, the energy stored is not large, or the material to be processed has good heat resistance, and the quality of the precision end is acceptable, then a single hot stamping path can also be used.

[0053] By using the half-cut laser path in step (1), the beginning and end of the process wire are half-cut to separate the metal layer of the process wire from the surrounding metal layer, while not damaging or minimally damaging the underlying substrate.

[0054] The purpose of step (2) is to thermally isolate the single process wire to be processed from the surrounding metal, while ensuring that the metal pattern retained by the component is accurate in size, has smooth edges, and is basically undamaged or meets the requirements.

[0055] According to the current consensus in the laser industry, the effects of lasers on materials can be divided into two types: photothermal effect and photochemical effect.

[0056] The photothermal effect refers to the phenomenon where, when a material is exposed to light, photons interact with the crystal lattice, intensifying vibrations and raising the temperature, leading to changes in the material's properties. Examples include thermistors and thermocouples utilizing the photothermal effect, the changes in the three states of matter (gas, liquid, and solid) caused by the photothermal effect, and changes in hardness, odor, and light transmittance caused by the photothermal effect. The photothermal effect primarily affects the van der Waals forces between molecules.

[0057] Photochemical effects refer to the phenomenon of permanent chemical changes caused by the interaction of light and matter. The primary process mainly involves the chemical bonds within molecules. Different chemical bonds within a molecule have different bond energies. When encountering photons of similar energies, these bonds can be broken, causing large molecules to decompose into smaller atomic or ionic clusters. For example, organic macromolecules can be broken down into C, C2, C3, CH, C2H2, etc. The extent of the photochemical effect depends mainly on the wavelength of the laser and the substance being acted upon. Different wavelengths of laser light emit photons with different electron volt energies. For example, the electron volt of 1064nm infrared light is 1.17, 532nm green light is 2.34, 355nm ultraviolet light is 3.51, and 266nm deep ultraviolet laser photons have an energy of 4.68 electron volts. Different substances contain different chemical bonds; the table below shows the bond energies of common chemical bonds.

[0058] Table 1. Bond energy table of common chemical bonds.

[0059]

[0060]

[0061] It is generally believed that when the energy of photons emitted by a laser is close to or greater than that of a chemical bond within the molecules of the affected material, this bond can be broken, causing the molecule to break down into smaller fragments. Because this process directly involves interatomic forces rather than intermolecular forces, and does not rely on molecular vibrations caused by thermal effects to break the crystal lattice, but rather directly breaks chemical bonds, pure photochemical effects are generally considered to have little or no thermal effect. Therefore, laser processing utilizing photochemical effects is also known as cold processing. As shown in the table above, a 1064nm laser with a photon energy of 1.17 eV cannot directly open any chemical bonds, while green light with a photon energy of 2.34 eV can only directly open a few. Therefore, green and infrared lasers are generally considered to be used for thermal processing of most materials. However, for 355nm ultraviolet light, with a photon energy of 3.51 eV, a considerable number of chemical bonds can be directly opened, especially those abundant in nature such as CC, CO, CS, CO, CO, CO, CO, CH, and CS. Deep ultraviolet lasers with a photon energy of 4.68 eV can open even more chemical bonds. Laser cold processing of a substance does not require breaking all chemical bonds. The chemical bonds between atoms are like ropes of varying thicknesses; by breaking only a portion of the thinner bonds, the molecule is transformed into ions or ion clusters and cut. Therefore, cold processing generally refers to ultraviolet or deep ultraviolet laser processing. The advantages of cold processing are a small processing interface, minimal impact on surrounding and underlying layers, and slight oxidation, blackening, or discoloration.

[0062] Lasers have two important characteristic parameters: wavelength (mentioned above) and pulse width, which is the duration of a laser pulse. Common sense tells us that the longer the laser pulse lasts, the more heat is transferred to the surrounding environment. Therefore, with similar duty cycles, a shorter laser pulse duration results in a smaller thermal effect—this is the macroscopic reason. There is another microscopic reason, generally explained in the industry as relaxation time. Relaxation time, in this context, can be understood as the time it takes for an atom to return from a high-energy state to an equilibrium state after absorbing laser photon energy, including the longitudinal equilibrium time and spin equilibrium time. Within a relaxation cycle, an atom exists in a state where heat transfer to surrounding atoms is most efficient. This state might be characterized by the closest proximity to a neighboring atom (shortest bond length and highest bond energy), a specific angle between the electromagnetic field and the atom (e.g., 90 degrees), or the highest electron cloud overlap. In short, this state exists within each relaxation cycle. However, if the pulse width of the laser is shorter than the material's relaxation time, the atom may not reach this state after receiving the photon, or a portion of the pulse may prevent the atom from reaching the ideal heat transfer state. The energy transfer efficiency of these pulses is low, thus reducing the thermal effect. Studies have shown that the relaxation time of most materials is between 100 femtoseconds and 10 picoseconds. Based on this data, if the laser pulse duration is less than 10 picoseconds, the thermal effect will decrease. Industry application experience has indeed verified this conclusion; the thermal effect of picosecond or femtosecond lasers is far less than that of continuous pulse, millisecond QCW, or nanosecond long-pulse lasers.

[0063] In summary, when selecting a laser for the partial cutting of process leads, it is best to choose a short-pulse-width ultraviolet or deep ultraviolet laser with a wavelength less than 355nm. This is because partial cutting of process leads involves slicing the metal layer, and the cut interface of the metal layer should ideally not oxidize or discolor, while also minimizing damage to the underlying substrate or causing carbonization and discoloration. Therefore, the laser should ideally have high absorption rates for the metal and low absorption rates for the substrate, while also considering the requirements of the processed product and choosing a relatively low-cost option. For example, some PI-based digital flexible circuit boards do not have very high requirements for metal layer cutting, but the underlying PI is very thin. A low-power infrared pulsed laser can be used because PI absorbs almost no infrared light, and the substrate will not be damaged after the metal layer is cut. Another example is some flexible circuit boards containing transparent PET substrates. When the metal layer is partially cut, the absorption rate of ultraviolet picosecond lasers is very high, and ultraviolet nanosecond lasers can also be used for processing. However, for this type of substrate, ultraviolet picosecond lasers can easily cut through, while ultraviolet nanosecond lasers absorb almost no light. Therefore, this type of material is more suitable for partial cutting using ultraviolet nanosecond lasers.

[0064] In terms of process selection, semi-cutting can use a low-power, multi-pass mode, or increase the interval between passes when performing multi-pass processing. A major difference between laser cutting and traditional mechanical drilling and milling is the chip removal method. Traditional drilling and milling uses active chip removal, which occurs simultaneously with processing. However, laser processing uses passive chip removal. High-power infrared lasers remove chips by blowing air after the metal has completely melted, while short-wave ultrafast lasers rely more on the natural volatilization of ion gas (the volatilization rate can be accelerated to some extent by adding air blowing and suction). As ion gas accumulates above the processing interface, it not only prematurely absorbs photons, reducing the effective efficiency of the laser, but also increases the carbonization ratio of the ion gas. Carbon particles falling around the processed surface increase insulation performance and improve appearance quality. Low-power processing reduces the amount of ion gas produced per pass, facilitating rapid removal. Increasing the interval between passes increases chip removal time, allowing the processed surface to be fully exposed to the laser. Of course, some materials, such as high-temperature metals, have strong oxidation resistance and can be processed at high power. However, low-power processing should be used near the bottom of the metal layer to avoid significant damage to the underlying substrate.

[0065] In terms of positioning, the workpiece is first fixed securely on the laser machine table. Depending on the product's positioning accuracy requirements, it can be positioned and processed in one continuous operation based on the path generated by CircuitCAM, or it can be positioned as a whole using CircuitCAM data, with each individual process wire precisely positioned and processed one by one. Precise positioning here refers to the equipment's CCD automatically finding the boundary between the metal and substrate based on their different colors, while the software calculates the position and length of the precision cutting path. For coarse cutting, the requirements are not high, and the original CircuitCAM data is generally used.

[0066] Step (3): Following the hot stamping laser processing path, the heat effect of the laser is used to heat up the process wires and reduce their bonding force with the substrate. At the same time, a certain positive pressure blowing or / and negative pressure suction is used to detach the process wires from the substrate.

[0067] Laser hot stamping utilizes the thermal effect of laser light. Under heat, the metal strip on the surface of the conductive wire separates from the underlying insulating substrate. The main reasons for this are as follows: 1. The coefficient of thermal expansion of the metal is generally greater than that of the insulating substrate (e.g., the coefficient of thermal expansion of commonly used FR4 is between 10-15 ppm / ℃, while that of commonly used copper is 17-20 ppm / ℃); 2. The temperature rise of the metal after heating is generally greater than that of the insulating substrate (e.g., the thermal conductivity of most insulating materials is between 0.12-0.35 W / mK, while copper has excellent thermal conductivity, with a thermal conductivity of 390-420 W / mK. Thus, when a laser is irradiated onto the surface of the copper metal layer, most of the energy is absorbed by the copper layer and converted into heat, causing the copper temperature to rise rapidly, while the insulating material has a slower heat transfer and a slower temperature rise); 3. After being partially cut, the metal layer is unconstrained and can freely expand under heat, while the small substrate perpendicular to the metal layer, although also having some... The temperature rises, but the expansion is limited by the surrounding and unheated substrate, making it difficult to expand and contract; 4. There is usually a certain thickness of adhesive layer between the metal layer and the insulating substrate. When the hot heat laser irradiates the metal layer, the instantaneous temperature usually reaches about 200℃, while the Tg temperature of commonly used adhesives is mostly below 100℃ (for example, the temperature of commonly used acrylic adhesive is 40-70℃). Even if some products do not have an adhesive layer between the metal layer and the lower organic insulating layer, the glass transition temperature of the organic insulating layer is usually below 200℃ (for example, the Tg temperature of epoxy resin in rigid board is usually 120-180℃). Under the irradiation of the hot heat laser, the adhesive between the metal layer and the lower organic dielectric layer or the upper resin of the dielectric layer will soften to a certain extent, the adhesion will decrease, the constraint of thermal expansion of the metal layer will be smaller, and it will be easier to detach from the dielectric layer; 5. While the metal layer and the dielectric layer are detached or partially detached, a certain pressure of blowing and / or suction is applied to make the strip-shaped metal layer quickly peel off the lower substrate.

[0068] When choosing a laser for thermal laser treatment, it's crucial to select one with a high thermal effect ratio. From a wavelength perspective, infrared and visible light (such as green light) are best. From a pulse width perspective, longer pulse widths are superior to shorter ones. Another key characteristic is that shorter pulse width lasers have a smaller duty cycle. For example, an infrared fiber laser with a pulse width of 100 nanoseconds typically operates at around 40 kHz, with a duty cycle of 0.4%, while a green disk laser with a pulse width of 10 picoseconds typically operates at around 400 kHz, with a duty cycle of 0.0004%. The shorter pulse duration and smaller duty cycle of the former make it more difficult for the thermal effect to accumulate on the metal. In simpler terms, after the first 10 picosecond pulse hits the metal, it takes 25,000 10 picosecond pulses before the next 10 picosecond pulse can strike, by which time the heat from the previous pulse has already dissipated. Therefore, in practical applications, people usually choose infrared or green light with a pulse width in the nanosecond range as the laser type for hot stamping. Nanosecond ultraviolet light can also be used, but it must be combined with certain process conditions.

[0069] From a process perspective, the purpose of thermal laser processing is to cause the metal layer of the process conductor to absorb heat and expand, not to melt. Therefore, the power density for heat absorption has a suitable range. If the power density is too high, local melting may occur; if it is too low, the temperature rise will be too low and the expansion tension will be too small. To control the power density, after selecting the laser (wavelength, pulse width, total power, etc.), it is crucial to control the appropriate power percentage, processing speed, and actual spot diameter. The actual spot diameter is controlled by a combination of factors, including the magnification of the beam expander, the focal length of the field lens, and the amount of defocusing. A key point here is that the actual spot diameter should be close to the width of the process conductor. This ensures uniform heating throughout the entire width direction during processing, facilitating detachment from the substrate. This "close" range is 0.5-1.1 times the width of the process conductor. Too small a diameter results in uneven heating, while too large a diameter can easily damage the substrate on both sides. For process conductors of different widths, different parameters must be adjusted to use different spot diameters.

[0070] The positioning of the hot stamping laser processing follows that of the semi-cutting laser. If the hot stamping laser processing and the semi-cutting laser processing are not performed on the same equipment, the positioning correction data of the actual semi-cutting laser processing needs to be transmitted to the hot stamping laser processing equipment.

[0071] Overall, the core characteristics of laser removal of electroplated wires are "cold" and "hot." The initial and final cutting of the metal wires relies heavily on cold processing, using a cold laser source, a cold air gun, low power, and intermittent processing. The laser cuts through the metal layer without damaging or minimally damaging the underlying substrate. The hot stamping process of the metal wires, on the other hand, emphasizes heat processing. The heat is applied without melting, increasing the expansion tension without melting the metal.

[0072] In summary, the laser removal process of this method involves the sequential peeling of individual metal strips from the substrate through alternating hot and cold temperatures and tension-relaxation interactions.

[0073] To more clearly illustrate the specific embodiments of the present invention, several examples are provided below:

[0074] Example 1

[0075] A method for laser removal of conductive lines on PTFE microwave gold-plated circuit boards. Microwave boards require precise patterning because they function not merely as conductors but as waveguides. Pattern accuracy has a significant nonlinear impact on frequency offset, power attenuation, waveguide velocity, and filtering accuracy, with the impact increasing at higher frequencies.

[0076] The processing steps in this embodiment are as follows:

[0077] Step 1: According to the requirements of the PCB file, the engineering department adds process guides, generates panelization files, and outputs drawings, programs, etc. for each production process.

[0078] Step two: The production line first performs drilling, hole metallization electroplating, dry film lamination on both sides, alignment, exposure, development, etching and other processes to complete the processing of conductive patterns.

[0079] Step 3: According to the process requirements, use process leads to complete the soft gold plating on both sides. See... Figure 1 .

[0080] Step four: Based on the distribution of the process guide wires, use CircuitCAM software to segment them into individual process guide wires and generate reasonable half-cut laser processing paths and hot-pressing laser processing paths. See... Figure 2 .

[0081] Step 5: After gold plating, the product is securely fixed on the dual-head laser processing system. Overall positioning is achieved using the four corner positioning holes. Each precision end is then precisely positioned using a CCD and the edge-finding positioning function of the equipment driver software. Finally, a UV picosecond laser head performs a half-cutting process on both the precision and coarse ends of each individual process wire. The half-cutting can be performed immediately after positioning one precision end, or it can be performed after all ends are positioned, depending on the positioning correction mode of the equipment driver software. Figure 6 This image shows the state of a single process wire after a partial laser cut, typically of the most precise-to-coarse type, with the single process wire to be removed and the surrounding metal insulation. To ensure processing quality at the bottom of the cut while improving efficiency, the precision end is processed using a high-power-first, then low-power approach.

[0082] The machining parameters for the precision end are:

[0083] First part:

[0084] 355nm 10ps 20μm 15w 400kHz 400mm / s 2 times

[0085] Later

[0086] 355nm 10ps 20μm 3w 400kHz 800mm / s 2 times

[0087] The machining parameters for the roughing end are:

[0088] 355nm 10ps 20μm 15w 400kHz 100mm / s 1 time

[0089] Step six: After the process wires are partially cut, an infrared nanosecond fiber laser is used to heat-process the path. With the help of blowing and suction, each process wire is peeled off from the substrate and collected from the suction port into the dust collection tray of the vacuum cleaner. Figure 7 This demonstrates the state of a single process wire after hot-stamping laser processing, which is the most common type of precision-to-coarse end-to-precision process wire. The single process wire to be removed has detached from the substrate, and some conductive structure outside the outline may remain. Figure 8 This shows the state of the entire product after removing a single process wire.

[0090] Processing parameters of hot stamping laser

[0091]

[0092] Step 7: In accordance with the full process requirements of the product, perform the inner groove through-cutting process (7 in total for this product), inner contour line processing, and outer contour line processing in sequence to complete the entire process of the product manufacturing.

[0093] Example 2

[0094] Laser removal of the conductive wires after gold plating on traditional FR4 board gold connectors. Gold plating on FR4 board gold connectors, also known as gold-plated fingers, typically uses cobalt gold to give the connector oxidation resistance and wear resistance, while also reducing the contact resistance between the connector and the socket. This type of product does not have very high requirements for the dimensions of the metal layer (not the milled external dimensions), but it does have high requirements for appearance because the connectors are mostly external.

[0095] The processing steps in this embodiment are as follows:

[0096] Step 1: According to the requirements of the PCB file, the engineering department adds process guides, generates panelization files, and outputs drawings, programs, etc. for each production process.

[0097] Step two: The production line completes all processes before nickel-gold electroplating according to the process requirements.

[0098] Step 3: Use gold-plated wires to complete the nickel-gold plating at the plug. See... Figure 9 .

[0099] Step four: Using CircuitCAM software, the portion within the outline of the process guide network is divided into individual process guides, and reasonable half-cut laser processing paths and hot-pressing laser processing paths are generated. See Figure 10 The software roughly determines the half-cut path to be on the same straight line and automatically generates a complete path, reducing laser jumps and switching delays and improving processing efficiency. Figure 10 First, a magnified view of a local detail.

[0100] Step 5: After the gold-plated product is fixed in place on the ultraviolet nanosecond laser machine, it is positioned as a whole using the four corner positioning holes. The ultraviolet nanosecond laser head is used to perform half-cut processing on the precision end and rough end of each individual process wire. Figure 10 The second image shows the state of one of the fingers (precision end to coarse end type) after a half-cut laser processing, with the single process wire to be removed and the surrounding metal insulation.

[0101] The machining parameters for the precision end are:

[0102] 355nm 20ns 20μm 15w 30kHz 400mm / s 2 times

[0103] The machining parameters for the roughing end are:

[0104] 355nm 20ns 20μm 30w 30kHz 100mm / s 1 time

[0105] Step six: After the process wire is partially cut, the ultraviolet nanosecond laser is still used to change the parameters for hot stamping path processing. Figure 10 The third image shows the state of a single finger after the process wire has been removed. Figure 10 The fourth section shows the state of the entire product after removing a single process wire.

[0106] Processing parameters of hot stamping laser

[0107]

[0108] Step seven: Following the product's overall process requirements, proceed with subsequent character printing and shape processing.

[0109] Finally, any parts of this invention not described herein utilize existing mature products and technologies.

[0110] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for removing electroplated wires using a laser, characterized in that, The specific steps of this method are as follows: (1) Based on the state of the existing process wires after electroplating, design the half-cut laser processing path and the hot stamping laser processing path; (2) By using the half-cut laser path in step one, the beginning and end of the process wire are half-cut to separate the metal layer of the process wire from the surrounding metal layer and reduce the damage to the substrate of the lower layer. (3) According to the hot heat laser processing path, the heat effect of the laser is used to heat up the process wire and reduce the bonding force with the substrate. At the same time, positive pressure blowing and / or negative pressure suction are used to make the process wire detach from the substrate. In the laser processing path design stage of step (1), the software automatically decomposes the process wires into single process wires without intersections based on the overall distribution of the process wires. The precision end half-cutting processing path and the rough end half-cutting processing path of the single process wire are defined according to the characteristics of the beginning and end of the single process wire and the required processing accuracy. Then, the following three hot stamping laser paths are generated on the single process wire according to the characteristics of the single process wire: a) a single hot stamping laser path from the precision end to the rough end; b) a single hot stamping laser path from the rough end to the rough end; c) a double hot stamping laser path from the precision ends at both ends to the middle position of the length direction of the process wire. The precision end half-cutting processing path generated in step (1) has the following positional characteristics: it is located at the midpoint of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide, and moves a certain distance in the direction of the process guide. This certain distance is half the diameter of the light spot, or any value between 0 and 10 light spot diameters. Its length characteristics are as follows: the length of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide is minus the reduction amount of etching, and then the length of the R-angle radius formed after etching is added to both ends; the reduction amount of etching and the R-angle radius need to be determined according to the metal layer thickness and the process capability of the etching line; when the line connecting the intersection is a straight line and perpendicular to the process guide, the length of the line connecting the intersection of the formal metal pattern of the product to be processed and the process guide is the width of the process guide; The rough end-half-cutting processing path generated in step (1) has the following positional characteristics: the rough end-half-cutting processing path is not displayed on the final product graphic after the process wire is removed; the half-cutting laser processing path is outside the product outline or in the middle of the through-cut inner groove or large hole; its length characteristics are: after intersecting with a single process wire, each end is extended by a certain length, and the certain length is any value within 0-10mm. The hot stamping laser processing path generated in step (1), if it is of the type from precision end to coarse end, has the following positional characteristics: the midpoint of the laser path half-cut at the precision end moves a certain distance toward the process guide, which is half the diameter of the laser spot or any value within 0-0.5mm; the positional characteristics of the coarse end are: the midpoint of the laser path half-cut at the coarse end moves a certain distance toward the precision end (i.e., the negative direction) or away from the precision end (i.e., the positive direction), which is any value within -0.2-100mm. If the hot heat laser processing path generated in step (1) is of the type from coarse end to coarse end, the positional characteristics of its two coarse ends are that the midpoint of the half-cut laser path at the coarse end moves a certain distance in the direction of the midpoint of the process guide length, i.e., the negative direction or away from the midpoint, i.e., the positive direction. This certain distance is any value within the range of negative 0.2-100mm. If the hot stamping laser processing path generated in step (1) is of the precision end-to-precision end type, then two hot stamping laser paths are generated. Both paths start from their respective precision ends and end at a certain position in the middle of the process guide along the centerline of the process guide. The positional characteristics of the two precision ends are that the midpoint of the half-cut laser path at each precision end moves a certain distance in the process guide direction. This certain distance is half the spot diameter, or any value within 0-0.5mm. The endpoints of the two hot stamping laser paths are a certain distance to the left and right of the midpoint in the process guide centerline length direction, or a certain distance to the left and right of a point moved a certain length before or after the midpoint. The two hot stamping paths do not intersect, and the distance between them is a spot diameter or any value within 0-1mm. This "fixed length" refers to the fact that the lengths of the two hot stamping paths may not be equal, and can actually be any value from 0 to the length of the process guide. If it is 0 or the length of the process guide, then the two hot stamping paths are actually one hot stamping laser path. The length of the end of the two hot stamping laser paths and the line connecting the beginning and end are continuous straight lines, or broken lines with a certain angle to the two outwards. This "fixed length" is any value within 0-10mm, and the "fixed angle" means that the vertical length of the two endpoints after the angle from the nearest edge of the process guide is any value within 0.25-0.5 times the width of the process guide. In step (2), the process wire half-cutting stage is performed. Especially for the processing of precision ends, the laser temperature needs to be controlled at a low temperature so that the laser can penetrate the process wire without burning through the substrate. This low temperature refers to the low temperature process when cutting the upper metal layer. According to the characteristics of the material, a lower wavelength, lower pulse width, lower duty cycle, higher interval time, and lower power are selected for the laser output. The lower wavelength range is any value within 1064nm-0nm, the lower pulse width range is any value within 100ns-10fs, and the lower duty cycle range is 0.5%-0.1ppm. Any value within the range, with higher interval time ranging from 0-10s and lower power ranging from 0.05-100W; the laser penetration process means that the upper metal layer is cut through without burning through the substrate, thus reducing substrate damage; a suitable light source needs to be selected based on the characteristics of the material to be processed. Given the high absorption rate of the upper metal layer and the low absorption rate of the lower substrate, a suitable process needs to be selected, such as using low power and multiple passes for half-cutting. When the substrate layer is cut, the laser machine collects the change in cutting speed and reduces the power or stops processing accordingly; In step (2), the process guide semi-cutting stage is performed. The positioning method is characterized by using the positioning points designed in step (1) for overall positioning, and using the semi-cutting path generated in step (1) for continuous processing of the whole board; or using the positioning points designed in step (1) for overall positioning, and then each single process guide is positioned again; the positioning sequence is as follows: first, determine the position of the fine end path, and the coarse end automatically follows; the positioning of the fine end is determined by human eye positioning or equipment edge-finding positioning; in equipment edge-finding positioning, the equipment CCD automatically finds the boundary between the metal and the substrate according to the different colors of the metal and the substrate, and according to the process guide The initial start and end points of the precision end cutting path are found at the two intersection points of the two boundary straight lines and the product graphic boundary straight line or curve. Then, based on the measured radius of the two ends, after a certain correction, the initial start and end points are extended to the second start and end points. The current entire path is then translated a certain distance in the process guide direction with the midpoint as the reference, which is taken as the actual precision end half-cutting path. The certain correction of the radius ... In step (3), the hot-heat laser processing stage is characterized by the need to control the laser temperature to be high so that the laser heats the process wires without melting the process wires and substrate. The high temperature refers to the use of the laser's thermal effect in the selection of the laser and the selection of process parameters. The laser parameters are selected according to the characteristics of the material, including: longer wavelength, larger pulse width, higher duty cycle and stronger power. The higher wavelength is any value within the range of 355nm-10640nm, the longer pulse width is any value within the range of 10ps-10μs, the higher duty cycle is any value within the range of 1ppm-100%, and the stronger power is any value within the range of 0.1W-1000W. The fact that the process wires and substrate do not melt means that the metal layer heats up and expands after absorbing heat, but cannot melt. Therefore, the power density of the heat-heating laser needs to be selected according to the type and thickness of the material. The goal is to make the temperature rise of the metal layer as high as possible to increase the expansion tension, while preventing it from melting and softening and losing tension. In step (3), during the hot stamping laser processing stage, the size of the laser spot diameter should be close to the width of the process wire; this closeness is any value ranging from 0.5 to 1.2 times the width of the process wire; if the spot diameter is too small, it will cause uneven heating in the width direction of the process wire and the expansion tension will be constrained; while if the spot diameter is too large, it will cause the substrate on both sides of the process wire to be burned; for process wires of different widths, the spot diameter should be adjusted manually or automatically by the equipment to a suitable size.

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