Laser repair process using spectral components of light induced and emitted during repair to control electronic circuit

Abstract

A method includes directing a laser beam to irradiate a section of a substrate to remove a layer formed on the section. At least a spectral component indicative of layer material removed from the layer is detected from light emitted from the section in response to the irradiating laser beam. Based on the detected spectral component, the laser beam irradiation of the section is controlled or stopped.

Description

Technical Field

[0001] This invention generally relates to the production of electronic products, and more specifically, to a method and system for controlling a laser repair process for electronic circuits. Background Technology

[0002] Various techniques have been developed for controlling processes, such as laser-based repair of electronic circuits.

[0003] For example, U.S. Patent Application Publication No. 2005 / 0226287 describes a laser processing system comprising a femtosecond laser, frequency conversion optics, beam manipulation optics, target motion control, a processing chamber, a diagnostic system, and a system control module. This laser processing system allows for unique thermal control in micromachining and features greater output beam stability, continuously variable repetition rates, and unique time-dependent beam shaping capabilities.

[0004] U.S. Patent Application Publication No. 2007 / 0092128 describes an apparatus and method for automatically inspecting and repairing printed circuit boards (PCBs). The apparatus includes an inspection function for automatically inspecting the PCB and providing machine-readable instructions for areas on the PCB that require repair. The automatic repair function uses these machine-readable instructions to repair the PCB at certain areas that require repair. An automatic repair re-inspection function automatically re-inspects the PCB after the initial automatic repair operation and provides re-inspection machine-readable instructions for the areas on the PCB that require repair. Summary of the Invention

[0005] The embodiments of the invention described herein provide a method comprising guiding a laser beam to irradiate a segment of a substrate to remove a layer formed on the segment. At least a spectral component of the layer material to be removed from the layer is detected from light emitted from the segment in response to the irradiating laser beam. Based on the detected spectral component, the irradiation of the segment by the laser beam is controlled or stopped.

[0006] In some embodiments, guiding the laser beam includes a guide pulse laser beam. In other embodiments, the substrate includes a printed circuit board (PCB) with a laminate and the layer includes copper defects. In yet another embodiment, the method includes detecting additional spectral components of the light emitted from the segment, which indicate substrate material removed from the substrate.

[0007] In one embodiment, controlling or stopping the laser beam involves setting a stop time based on both the spectral component and the additional spectral component. In another embodiment, in response to detecting that both the spectral component and the additional spectral component are above a predefined threshold, the laser beam is redirected to irradiate the layer within the segment.

[0008] In some embodiments, controlling or stopping the laser beam includes performing at least one operation selected from a list of operations: (i) blocking the laser beam, (ii) turning off the laser beam, and (iii) directing the laser beam to a subsequent segment of the substrate. In other embodiments, detecting at least the spectral components includes detecting one or more spectral emissions selected from a list of spectral emissions: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) laser-induced breakdown spectroscopy (LIBS).

[0009] According to an embodiment of the present invention, an additional system is provided, comprising an optical assembly, a detection assembly, and a processor. The optical assembly is configured to guide a laser beam to irradiate a segment of a substrate, and the laser beam is configured to remove a layer formed on the segment. The detection assembly is configured to detect spectral components of layer material removed from the layer from light emitted from the segment in response to the irradiating laser beam. The processor is configured to control or stop the laser beam from irradiating the segment based on the detected spectral components.

[0010] In some embodiments, the optical assembly includes at least one of an acousto-optic modulator (AOM), a scanning mirror, and a focusing optics.

[0011] The invention will be more fully understood from the following detailed description of embodiments of the invention, taken in conjunction with the accompanying drawings, wherein: Attached Figure Description

[0012] Figure 1 This is a block diagram of a system for repairing electronic circuits using a laser, according to an embodiment of the present invention.

[0013] Figure 2A , 2B And 2C is a graph illustrating the spectral components of the emitted light from copper removed from the substrate according to an embodiment of the present invention; and

[0014] Figure 3 This is a flowchart illustrating, according to an embodiment of the present invention, a method for controlling the removal of defects from electronic circuits using spectral components of light emitted from defects during the process. Detailed Implementation

[0015] Overview

[0016] Sometimes, various types of defects can occur during the manufacturing process of electronic components or modules in printed circuit boards (PCBs). For example, when a pattern of copper traces is formed on the laminate of a PCB, defects, including unwanted copper layers, can appear between the copper traces. It is important to remove these defects without damaging the laminate that is normally underneath the copper to maintain the functionality of the PCB.

[0017] The embodiments of the invention described below provide improved techniques for repairing electronic modules (e.g., PCBs) by removing defects that occur during the manufacturing process of the PCB. For example, removing defects including those resulting in unwanted copper layers formed between traces of a designed copper pattern on a laminate of the PCB.

[0018] In principle, an iterative process can be used to remove defects from a section of the PCB by ablation of a portion of the defect, followed by inspection of the section, and the process can be repeated until the entire defect is removed. This iterative process reduces the risk of damaging the PCB laminate; however, each inspection step is time-consuming and reduces the throughput of the defect removal process.

[0019] In some embodiments, a system for repairing a PCB by removing defects using laser ablation includes an optical assembly, one or more detection assemblies, and a processor. The optical assembly is configured to guide a laser beam to irradiate a segment of the PCB substrate. The laser beam is configured to ablate unwanted or excessive copper layers to remove defects formed in the segment. In the context of this invention and in the claims, the term "copper layer" refers to any kind of unwanted copper defect, such as (but not limited to) excessive copper segments, copper residue, copper spatter, excessive copper patterns, separated copper defects, or a combination of copper and foreign matter, or any other type of defect including copper.

[0020] In some embodiments, one or more detection assemblies are configured to detect the spectral components of copper removed from defects from light induced and emitted from the segment in response to an irradiated laser beam.

[0021] It should be noted that the interaction between the laser beam and the excess copper in the defect induces light emitted from the defect at certain sections. Therefore, in the context of this invention and in the claims, the term "emitted light" refers to light induced in response to a laser beam irradiating the copper, such that the induced light is emitted from the ablated copper.

[0022] Furthermore, in the context of this invention and in the claims, the term "spectral component" refers to one or more spectral lines of the copper and / or other element of interest to be detected. For example, the spectral component of copper may include one or more of the following spectral lines having wavelengths of about 5700 angstroms (Å), about 5782 Å, about 6000 Å, and about 6150 Å, or any other suitable wavelength.

[0023] The term spectral component can also refer to the spectral components emitted by the laminate or any other material of interest.

[0024] Attention should be paid to the presence of copper defects on the PCB substrate, which constitutes the spectral components, and the fingerprints of the ablation process used to remove unwanted copper defects.

[0025] In some embodiments, using the disclosed techniques to remove defects has several advantages, such as (but not limited to): (a) defect identification – detecting one or more spectral components emitted during ablation indicates the presence of a defect, and the intensity of the detected signal varies independently of, for example, attributable to geometric factors (e.g., surface roughness or the shape of the defect); (b) accurate spatial monitoring – the same laser beam is used for both the emission of the ablation and induced light and the detected spectral components, thus eliminating optical aiming line errors and ensuring that the detected spectral components are emitted from the actual location of the ablation; and (c) real-time indication and control – the detection assembly receives in real time one or more spectral components emitted in response to each pulse of the laser beam irradiating the defective section, thus enabling real-time control and adjustment of the ablation process, which is described in detail herein.

[0026] In some embodiments, the processor is configured to control the laser beam (e.g., to reduce laser power and / or change the scan rate, and / or adjust the beam profile and / or spot size and / or control any other suitable parameters of the laser beam).

[0027] In other embodiments, the processor is configured to: (i) set a stop time for the laser beam based on the detected spectral components, and subsequently or simultaneously, (ii) stop the laser beam irradiation segment at the set stop time. In the context of this invention and the claims, the term stop time is also referred to herein as the “end point” of the ablation of the copper defect.

[0028] In some embodiments, the optical assembly may include an acousto-optic modulator (AOM) configured to: (a) block or allow (on / off) the laser beam to reach the PCB, (b) control the intensity of the laser beam, and (c) control the number of pulses of the laser beam passing through the AOM and illuminating the surface of the PCB.

[0029] In some embodiments, the processor is configured to stop the laser beam from irradiating the surface of a PCB segment by controlling the AOM or other components of the optical assembly.

[0030] In some embodiments, (i) the detection assembly may include a rapid spectrometer configured for detection from emitted light, at least one additional spectral component, and / or (ii) the system may include one or more additional detection assemblies. The detection assembly (e.g., a rapid spectrometer) and / or one or more additional detection assemblies are configured to detect additional spectral components of substrate material (e.g., laminate) removed from the PCB segment during the ablation process from light induced and emitted during the ablation process.

[0031] In some embodiments, in response to receiving a signal indicating lamination spectral components from an additional detection assembly, the processor is configured to set a stop point based on the lamination spectral components.

[0032] In some embodiments, the system may include a camera assembly configured to acquire images of a PCB segment prior to ablation (e.g., to accurately guide a laser beam to the defect), and / or, after ablation, (e.g., to verify that the entire defect has been removed and the laminate has not been damaged).

[0033] In some embodiments, after the removal of defects from a segment is completed, the processor is configured to move the PCB relative to the optical assembly to position the optical assembly to remove subsequent defects located in subsequent segments of the PCB.

[0034] The disclosed technology, with necessary modifications, can be applied to repair other types of electronic components and modules, such as (but not limited to) flat panel displays (FPDs).

[0035] Furthermore, the disclosed technology reduces the cycle time of PCBs and other electronic components and modules and improves the accuracy of repair processes, thereby reducing production costs and improving the quality of PCBs and electronic products.

[0036] System Description

[0037] Figure 1 This is a block diagram of a system 11 for repairing the electronic circuitry of sample 21 according to an embodiment of the present invention. In this example, sample 21 includes a printed circuit board (PCB), but in other embodiments, sample 21 may include any other suitable type of component or module on an electronic product, as described below.

[0038] In some embodiments, system 11 includes an optical assembly 13 having a laser source (referred to herein as laser 12) configured to emit a laser beam 25. In this example, laser 12 is configured to emit pulses of green laser light with a wavelength of 532 nm, but in other embodiments, laser 12 may be configured to emit any other suitable type and wavelength of laser beam, such as (but not limited to) 1064 nm or 266 nm.

[0039] In the context of this invention and in the claims, the terms “laser beam 25”, “beam 25” and “laser beam” are used interchangeably and refer to a beam emitted from laser 12 toward sample 21 and manipulated by components of optical assembly 13 of system 11, which is described in detail herein.

[0040] In some embodiments, the optical assembly 13 includes an acousto-optic modulator (AOM) 16, a scanner 18, and a focusing optics 24, which are described in detail below. In some embodiments, the light beam 25 is configured to pass through the optical assembly 13 and is directed to the sample 21 to repair electronic circuitry generated on the surface of the sample 21.

[0041] In some embodiments, the optics 14 is configured to shape and focus the beam 25 before it enters the AOM 16, the AOM 16 being configured to (a) block or allow (on / off) the laser beam 25 toward the sample 21, (b) control the intensity of the beam 25, and (c) control the number of pulses of the beam 25 passing toward the sample 21.

[0042] In some embodiments, scanner 18 may include a scanning mirror or any other suitable type of scanner configured to direct beam 25 to illuminate a segment of sample 21 to remove a layer (e.g., copper) formed on the corresponding segment of sample 21. Scanner 18 is further configured to scan beam 25 across the intended location on the surface of sample 21 using any scanning scheme (interlaced scanning, helical scanning, or any other type of scanning scheme) at any suitable scanning rate (e.g., typical scanning rates are between (but not limited to) about 10 mm / s and about 1000 mm / s).

[0043] In the context of this invention, the terms “about” or “approximately” used for any numerical value or range indicate suitable dimensional tolerances that allow a collection of parts or components to function for their intended purpose.

[0044] In some embodiments, focusing optics 24 are configured to focus a beam 25 directed to a desired location on the surface of sample 21. For example... Figure 1 As shown, the optical assembly 13 is configured to scan the laser beam 25 to illuminate the desired section of the sample 21.

[0045] It should be noted that during beam scanning, the first beam 25 can illuminate the first segment of the sample 21 at approximately a right angle, and the second beam 25 can illuminate the surface of the second different segment at any suitable angle other than a right angle.

[0046] Referring now to illustration 19, which shows the surface of a segment of sample 21. In this embodiment, the segment of sample 21 includes a layer 22 patterned on a substrate 23 (e.g., the laminate of the aforementioned PCB) having copper or a copper alloy. Sometimes, a defect 17 may occur during PCB manufacturing (in this example, an unwanted excess pattern of copper). Excess copper patterning can cause, for example, electrical short circuits between traces of layer 22, which can impair the functionality of the PCB.

[0047] Now return to reference Figure 1A general view. In some embodiments, system 11 is configured to repair such defects 17 appearing in segments of sample 21 by irradiating the surface of the corresponding segment with a guide beam 25 to remove defects 17 using a laser ablation process. In response to irradiating the laser beam 25, light is emitted from the surface of sample 21. In this example, some beams (referred to herein as beam 30, which is a coaxial beam) are approximately perpendicular to sample 21; and other beams (referred herein as beam 32, which is an off-axis beam) are at other angles to sample 21, such as... Figure 1 As shown in the image.

[0048] Detection indicates the spectral components of copper removed from the substrate

[0049] In some embodiments, system 11 includes detection assemblies (DAs) 34 and 44 configured to detect beams 30 and 32, respectively. It should be noted that beam 30 is detected as it passes through focusing optics 24, and therefore typically (but not necessarily) contains more and different information than the information received from beam 32. It should be noted that beam 32 does not pass through focusing optics 24, and therefore has less interference compared to beam 30. Thus, the combination of beams 30 and 32 provides complementary light induced and emitted from sample 21.

[0050] In some embodiments, system 11 includes a beam splitter (BS) 29 configured to direct beam 30 to DA 34. In some embodiments, DA 34 is configured to detect from beam 30 a spectral component of copper indicating a defect 17 removed from substrate 23 of sample 21 during an ablation process.

[0051] In some embodiments, DA 34 includes one or more filters 37 configured to pass through one or more respective spectral components of copper (also referred to herein as copper spectral components) and block other spectral components of the light beam 30. DA 34 further includes (i) an optics 36 configured to focus the emitted light, which includes one or more copper spectral components (SC) passing through one or more filters 37, and (ii) one or more detectors 35 configured to detect copper SC.

[0052] In some cases, at least a portion of the laser beam 25 may be reflected and / or scattered from the surface of the sample 21, and may cause saturation of one or more detectors 35, thus ignoring the spectral components of interest.

[0053] In some embodiments, at least one of filters 37 and 47 may further include a repulsion filter configured to attenuate or block laser light reflected and / or scattered from sample 21.

[0054] In the context of this invention, the detected spectral components constitute the presence of unwanted copper and ablation fingerprints indicating the presence of defects 17 that are not expected to form on the surface of substrate 23.

[0055] In some embodiments, the DA 44, configured to detect an off-axis beam (e.g., beam 32), includes a filter 47 configured to pass through the copper SC and block other spectral components of the beam 30. The DA 44 further includes (i) an optics 46 configured to focus and shape the copper SC through one or more filters 47, and (ii) one or more detectors 45 configured to detect one or more copper SCs.

[0056] In some embodiments, DA 34 and 44 are configured to detect any suitable type of spectral emission, such as one or more spectral emissions selected from the following list of spectral emissions: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) laser-induced breakdown spectroscopy (LIBS).

[0057] In some embodiments, system 11 includes processor 33 configured to receive signals from Da 34 and 44 indicating the detection of copper SC. Based on the received signals, processor 33 is configured to set a stop time for guiding laser beam 25 to the defect 17 in the section of sample 21, and to stop the beam 25 from irradiating the section at a set stop time (also referred to herein as the end point) of the laser ablation process.

[0058] In some embodiments, the processor 33 is configured to control the active components of the optical assembly 13 (e.g., but not limited to, laser 12, AOM 16, and scanner 18) to stop the beam 25 from illuminating the aforementioned section of the sample 21. Figure 1 In one example, system 11 includes a controller 46 configured to control AOM 16 and a controller 48 configured to control scanner 18. In other embodiments, processor 33 is configured to directly control at least one of AOM 16 and scanner 18. Similarly, system 11 may include a controller (not shown) configured to control laser 12. All of the above controllers are configured to exchange control signals and other types of data with processor 33.

[0059] In some embodiments, processor 33 is configured to synchronize the operation of DAs 34 and 44 with the illumination of a segment of sample 21 by laser beam 25. For example, processor 33 is configured to “turn on” at least one of DAs 34 and 44 to detect emitted light only after a predefined time delay (e.g., a few microseconds) following the illumination of defect 17 by one or more pulses of laser beam 25. It should be noted that the emission of spectral components can be time-dependent; therefore, controlling the detection timing can improve the signal-to-noise ratio (SNR) of the detected spectral components.

[0060] In some embodiments, laser 12 includes any suitable laser, such as (but not limited to) a passive Q-switched microlaser supplied by Teem Photonics in Grenoble, France, configured to emit pulses of laser beam 25. In such embodiments, processor 33 is configured to control AOM 16 to stop or pass beam 25, and to set the intensity and number of pulses of beam 25 applied to sample 21 by laser 12.

[0061] In other embodiments, in addition to laser 12, system 11 may include an ultraviolet (UV) laser that is optically aligned with laser 12 and configured to guide a UV beam onto sample 21 at the same location as the laser beam 25 guided by laser 12.

[0062] In some embodiments, DAs 34 and 44, or additional DAs, are configured to detect the spectral response emitted from sample 21. It should be noted that the detected spectral response is enhanced by the UV beam, and the DAs are configured to generate a signal with an improved SNR (attributed to the presence of the UV beam), indicating one or more detected spectral components of copper emitted from defect 17.

[0063] In some embodiments, the processor 33 holds one or more segments of a sample 21 having defects 17 to be removed by laser ablation. The processor 33 is configured to control the repair process of defects 17 at corresponding segments by controlling a scanner 18 for scanning laser beams 25 over one or more corresponding segments of the sample 21.

[0064] In some embodiments, system 11 includes an additional beam splitter (referred to herein as BS 15) and a camera assembly (CA) 20 configured to acquire images of sample 21. Images acquired by camera module 20 may be used, for example, to examine the target segment before and / or after the removal of defect 17 by laser beam 25, or for other purposes, such as navigating system 11 to the segment of sample 21 with defect 17.

[0065] In some embodiments, CA20 includes a camera optics assembly (COA) (not shown) configured to guide a beam of light to illuminate sample 21, and a camera (not shown) configured to receive a beam of light 28 reflected from sample 21 via BS 15. CA 20 is configured to transmit the acquired image to processor 33.

[0066] In some embodiments, the processor 33 is configured to prevent optical aiming line errors that may occur between the CA20 and the laser beam 25 at a desired location on the surface of the sample 21.

[0067] In other embodiments, because the processor 33 is configured to set the stop time for guiding the laser beam 25 to the sample 21, visual verification that the defect 17 has been removed from the sample 21 is not required, and therefore CA20 can be omitted from the configuration of the system 11.

[0068] In some embodiments, system 11 includes cables 40 configured to transmit signals received from DA 34 and 44 and control signals exchanged between processor 33, active components of system 11 (e.g., laser 12, AOM 16, and scanner 18) and camera assembly 20.

[0069] Typically, processor 33 includes a general-purpose processor programmed in software to implement the functions described herein. The software may be downloaded to the processor electronically, for example, via a network, or alternatively or additionally, it may be provided and / or stored on a non-transitory tangible medium (e.g., magnetic, optical, or electronic memory). Similarly, the aforementioned controller includes a general-purpose controller programmed in software to implement the functions described herein.

[0070] Detection indicates the spectral components of the substrate material removed from the substrate.

[0071] In some cases, for example, when the laser beam 25 is (intentionally or unintentionally) directed to the sidewall of the defect 17 located in the aforementioned section of the sample 21, the laser beam 25 can simultaneously irradiate the defect 17, which includes an excess pattern of copper, and the substrate 23.

[0072] In some embodiments, system 11 includes one or more additional detection assemblies (not shown) configured to detect additional spectral components from beams 30 and 32 indicating additional substrate material (e.g., laminate) removed from substrate 23 during ablation.

[0073] In some embodiments, DA34 and 44 may include additional filters (not shown) configured to pass through spectral components of the laminate that are inadvertently removed from the substrate 23 during ablation. These additional filters are configured to block other spectral components of the beams 30 and 32 (rather than those of the laminate).

[0074] In some embodiments, for example, additional filters may be mounted on DA 34 and 44 in addition to filters 37 and 47. In alternative embodiments, at least one of filters 37 and 47 is configured to allow both the spectral components of the copper and the laminate to pass through.

[0075] In some embodiments, when the laser beam 25 simultaneously irradiates the defect 17 and the substrate 23, copper and the laminate can be ablated from the sample 21. In response to ablation, the processor 33 can receive signals from DAs 34 and 44, or from one or more additional DAs, indicating both the spectral components of the copper and the spectral components of the laminate. In such embodiments, the processor 33 can (i) stop the laser beam 25 from irradiating the aforementioned sidewalls of the corresponding segment of the sample 21, and (ii) redirect the laser beam 25 to irradiate only the defect 17 to ablate the copper from the defect 17 without ablated the laminate or any other material from the substrate 23.

[0076] In other embodiments, at least one of DAs 34 and 44 may include a spectrometer configured to detect spectral components of copper from at least one of beams 30 and 32 and generate a signal indicating the detected spectral components of copper. In embodiments, the spectrometer may include a multi-element line sensor / detector based spectrometer from Ocean Insight, Rochester, New York, USA.

[0077] In some embodiments, the spectrometer may also be configured to simultaneously detect and generate signals indicating the spectral components of both the copper and the laminate, such that in response to receiving such signals, the processor 33 may stop the laser beam 25 from irradiating the substrate 23.

[0078] In some embodiments, at least one of detectors 35 and 45 and / or at least one of the aforementioned spectrometers may include rapid detection capabilities to shorten detection time and enhance real-time monitoring and control of the ablation process. In such embodiments, at least one of detectors 35 and 45 may include a fast photodiode supplied by, for example, Thorlabs Inc. of New Jersey, USA, and / or a fast spectrometer manufactured by, for example, Ocean Optics of Rochester, New York, USA.

[0079] In an alternative embodiment, system 11 may include a suitable combination of a DA and / or spectrometer and / or any other suitable subsystems configured to detect spectral components of copper and / or other foreign matter constituting defect 17 on substrate 23.

[0080] In some embodiments, processor 33 may receive a defect file from a defect inspection system (not shown) including the coordinates of first and second defects 17 located in first and second corresponding segments of sample 21. In some embodiments, processor 33 may control a motion control subsystem (not shown) to position the first segment close to optical assembly 13 to remove the first defect using laser beam 25, as described above. In some embodiments, after the ablation of the first defect is completed (e.g., by setting a stop time and stopping the laser beam 25 from irradiating the first segment at the set stop time), processor 33 is configured to control optical assembly 13 to guide laser beam 25 to the second segment to remove the second defect. For example, processor 33 may control AOM 16 to block laser beam 25 from irradiating the first segment and further control (e.g.) the aforementioned motion control subsystem to move sample 21 and laser 12 relative to each other to perform ablation of the second defect at the second segment. Alternatively, in cases where the first and second defects are very close to each other, after the removal of the first defect is completed, the processor 33 may control the scanner 18 to redirect the laser beam 25 to the second defect without using a motion control system.

[0081] As described above, after removing one or more defects 17 from the first and second segments of sample 21, processor 33 is configured to control the motion control subsystem to move sample 21 relative to system 11 to perform verification of the defects removed from the first and second segments.

[0082] In some embodiments, the system 11 is configured to ablate other types of defects occurring on other types of surfaces, such that the defects include surfaces containing materials other than copper and / or materials other than laminates.

[0083] For example, polymer defects may occur in sections with copper design patterns, such as during a soldering shielding process. In such embodiments, optical assembly 13 is configured to guide laser beam 25 to the polymer defect, and at least one of DAs 34 and 44 is configured to detect one or more spectral components induced by the laser beam 25 irradiating the defect. One or more spectral components are emitted from the polymer defect as components of beams 30 and 32 and are detected by at least one of DAs 34 and 44.

[0084] In such embodiments, processor 33 is configured to control the ablation process based on detected spectral components of at least polymer defects and copper patterns. Therefore, when the detected signal indicates one or more spectral components of copper, and / or when no spectral component of polymer defects is present in the detected signal, processor 33 is configured to control optical assembly 13 to stop the laser beam from irradiating the segment including the polymer defects, or to control the optical assembly to control the parameters of laser beam 25 to, for example, attenuate laser beam 25.

[0085] This particular configuration of system 11 is shown as an example to illustrate certain problems solved by embodiments of the invention and to demonstrate the application of these embodiments in enhancing the performance of this system. However, embodiments of the invention are by no means limited to this particular type of exemplary system, and the principles described herein can be similarly applied to other types of defect repair systems.

[0086] Figure 2A This is a graph 70 illustrating the detection of one or more copper spectral components 72 of light emitted from sample 21 over time during the ablation of defect 17 according to an embodiment of the present invention. The vertical axis specifies the intensity of one or more copper spectral components and the horizontal axis specifies the time axis.

[0087] exist Figure 2A In this example, defect 17 comprises a copper layer with a thickness of 18 μm. Dual-axis 76 illustrates the ablation time of defect 17, while markers 78 and 79 indicate the start time of the laser beam and the stop time of the spectral components emitted from the copper layer, respectively. Figure 2A In this example, the ablation time is approximately 85 milliseconds. Figure 70 also shows the detected noise 74. Note that after marker 79, the copper spectral component 72 is not present in Figure 70 because defect 17 has been removed. It should be noted that once the copper spectral component disappears, the laser will be switched off to avoid or minimize unwanted damage to the underlying laminate.

[0088] In some embodiments, processor 33 is configured to use any suitable technique to set the ablation stop time. For example, processor 33 may set a threshold for the signal intensity of the copper spectral component 72. In this example, when the signal intensity falls below the threshold within a predefined time interval, processor 33 controls, for example, AOM 16 and scanner 18 to stop the laser beam 25 from irradiating the segment with defect 17 at the set stop time indicated by label 79. In other embodiments, processor 33 may use any other suitable technique to set the ablation stop time.

[0089] Figure 2B This is a graph 80 showing the copper spectral components 82 of light emitted from sample 21 over time during the ablation of defect 17 according to an embodiment of the present invention. The vertical axis specifies the intensity of the copper spectral components and the horizontal axis specifies the time axis.

[0090] exist Figure 2B In this example, defect 17 comprises a copper layer with a thickness of 12 μm. Dual-headed shaft 86 illustrates the ablation time of defect 17, while markers 88 and 89 indicate the start and stop times of the ablation, respectively. Figure 2B In the example, the ablation time was approximately 45 milliseconds, generally lower than the above. Figure 2AThe ablation time. Figure 80 also shows the noise 84 of the copper spectral component. Note that after mark 89, the copper spectral component 82 does not appear in Figure 80 because defect 17 has been removed.

[0091] In some embodiments, processor 33 is configured to use any suitable technique to set the ablation stop time indicated by marker 89, as described above. Figure 2A As described in the text.

[0092] Figure 2C This is a graph 90 showing the copper spectral components 92 of light emitted from sample 21 over time during the ablation of defect 17 according to an embodiment of the present invention. The vertical axis specifies the intensity of the copper spectral components and the horizontal axis specifies the time axis.

[0093] exist Figure 2C In this example, defect 17 comprises a copper layer with a thickness of 7 μm. Dual-axis 96 illustrates the ablation time of defect 17, while markers 98 and 99 indicate the start and stop times of the ablation, respectively. Figure 2C In the examples, the ablation time was approximately 20 milliseconds, generally lower than the above. Figure 2A and 2B The ablation time. Figure 90 also shows the noise 94 of the copper spectral component. Note that after mark 99, the copper spectral component 92 does not appear in Figure 90 because defect 17 has been removed.

[0094] In some embodiments, processor 33 is configured to use any suitable technique to set the ablation stop time indicated by marker 99.

[0095] Referring now to the general views in Figures 2A, 2B, and 2C, which are based on experiments (e.g.) conducted by the inventors of the present invention to demonstrate the disclosed concepts. In some embodiments, the processor 33 is configured to set a stop time based on the detected spectral components of the copper in defect 17. Figures 2A, 2B, and 2C show similar start times by corresponding labels 78, 88, and 98, and different stop times by corresponding labels 79, 89, and 99. As described above, the stop times are set by the processor 33 for the corresponding copper thicknesses of 18 μm, 12 μm, and 7 μm attributed to defect 17.

[0096] In other embodiments, system 11 may include one or more additional DAs configured to detect spectral components of any other material of the laminate or substrate 23 ablated by laser beam 25. In such embodiments, the laminate spectral components are not detected by DAs 34 and 44, and therefore are not used by processor 33 to set the stop time for the ablation process used to remove defect 17.

[0097] In this example, in the examples in Figures 2A, 2B, and 2C, the copper spectral components can be detected solely by DA 34.

[0098] In other embodiments, processor 33 is configured to maintain a threshold for detecting the spectral components of the laminate. In such embodiments, when a signal including the spectral components of the laminate is received from one or more additional DAs at a level above the threshold, processor 33 is configured to set a stop time and control (e.g.) AOM 16 and / or scanner 18 to stop the laser beam 25 from illuminating the segment with defect 17.

[0099] As mentioned above Figure 1 As described, processor 33 can control AOM 16 to block laser beam 25 from irradiating the corresponding segment. Alternatively, processor 33 can control scanner 18 and / or the aforementioned motion control subsystem to move sample 21 relative to laser 12 to guide laser beam 25 to irradiate another segment of sample 21 to remove another defect 17 appearing on substrate 23.

[0100] Figure 3 This is a flowchart illustrating, according to an embodiment of the present invention, a method for controlling the removal of defect 17 from sample 21 using the spectral components of light emitted from defect 17 during the process.

[0101] The method begins with a laser guidance step 100, in which a laser beam 25 is guided to irradiate a segment of the substrate 23 of the sample 21 to remove the copper layer of defects 17 appearing in the segment. In this embodiment, the sample 21 includes a PCB having a substrate 23 containing a laminate.

[0102] At detection step 102, the spectral component of copper removed from sample 21 is detected in response to light emitted from a segment of sample 21 by at least one of the irradiating laser beams 25, DA 34, and 44.

[0103] It should be noted that the detected spectral components constitute fingerprints of non-desired copper layers and their ablation processes on the surface of substrate 23.

[0104] At step 104, processor 33, which maintains predefined thresholds for the emission levels of one or more spectral components (SCs), checks whether the detected SCs exceed the thresholds. For example, on the one hand, ablation is not yet complete when the detected copper SCs exceed the copper SC threshold. On the other hand, ablation must be stopped or at least adjusted when no copper SCs are present in the detected signal, or when the detected copper SCs are below the copper SC threshold, to prevent damage to the laminate segment. Therefore, if the detected copper SCs exceed the threshold, the method loops back to step 100 to continue ablating the copper layer in defect 17.

[0105] If the detected copper SC is below the copper SC threshold, the method proceeds to ablation control step 104, terminating the method. At ablation control step 104, processor 33 controls or stops laser beam 25 based on one or more detected SCs. For example, in the absence of copper SCs, the processor can set a stop time for laser beam 25 (shown as labels 79, 89, and 99 in graphs 70, 80, and 90, respectively). As described above... Figure 1 As described in section 2, the stopping time is based on the detected copper spectral component of the light emitted from the ablation defect 17 (e.g., beams 30 and 32). Process 33 is further configured to stop the laser beam 25 from irradiating a segment of sample 21 at a set stopping time.

[0106] In other embodiments, for example, when copper SC is still detected but below the copper SC threshold, the processor 33 is configured to control the optical assembly used to adjust the laser beam 25 to prevent or minimize damage to the laminate material (e.g., the aforementioned PCB) of the sample 21.

[0107] As mentioned above Figure 1 As described herein, in other embodiments, at least one of DA 34 and 44 is configured to detect spectral components of another material of the laminate or PCB. In such embodiments, at detection step 102, DA 34 and 44 may detect, in addition to the copper spectral component, the spectral components indicating the laminate removed from sample 21.

[0108] Furthermore, in such embodiments, in decision step 104, the processor is configured to check whether one or more SCs (e.g., laminated SCs) other than the copper SC have been detected by one or more of DA34 and 44. If not, the method loop returns to step 100 to continue ablation as described above.

[0109] If one or more laminated SCs have been detected, the method proceeds to step 104 to control or stop the laser beam 25. For example, the irradiation position of the laser beam 25 is controlled to ablate the defect 17 without damaging the laminate, or the laser beam 25 is stopped from irradiating the corresponding section, and thus, damage to the laminate is prevented.

[0110] While the embodiments described herein primarily address the removal of copper defects occurring on PCBs, the methods and systems described herein can also be used in other applications, such as using laser ablation to remove any type of defect from any type of substrate, and in other laser-based processes for producing electronic circuits, such as (but not limited to) controlled drilling and / or vias through copper layers, where stopping laser drilling is important to prevent damage to layers and / or laminates adjacent to the designed holes / vias.

[0111] Therefore, it will be understood that the above embodiments are cited by way of example, and the invention is not limited to the content specifically shown and described above. Rather, the scope of the invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereto that would occur to those skilled in the art upon reading the foregoing description and that are not disclosed in the prior art.

[0112] Documents incorporated herein by reference shall be considered an integral part of this application, except where such incorporated documents define any term in a manner that conflicts with the express or implied definitions in this specification, in which case only the definitions in this specification shall be considered.

Claims

1. A method comprising: A laser beam is guided to irradiate a section of a substrate to remove a layer formed on the section; Simultaneously detect at least a spectral component of the layer material removed from the layer and an additional spectral component of the substrate material removed from the substrate from the light emitted from the segment in response to the irradiation of the laser beam; and Based on the detected spectral components, the laser beam is controlled or stopped from illuminating the segment.

2. The method of claim 1, wherein guiding the laser beam comprises guiding a pulsed laser beam.

3. The method of claim 1, wherein the substrate comprises a printed circuit board (PCB) having a laminate and the layer comprises copper defects.

4. The method of claim 1, wherein controlling or stopping the laser beam comprises setting a stop time based on both the spectral component and the additional spectral component.

5. The method of claim 1, wherein in response to detecting that both the spectral component and the additional spectral component are above a predefined threshold, the laser beam is redirected to irradiate the layer within the segment.

6. The method of claim 1, wherein controlling or stopping the laser beam comprises performing at least one operation selected from a list of operations consisting of: (i) blocking the laser beam, (ii) turning off the laser beam, (iii) adjusting the power, and (iv) directing the laser beam to a subsequent segment of the substrate.

7. The method of claim 1, wherein detecting at least the spectral components comprises detecting one or more spectral emissions selected from a list of spectral emissions consisting of: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) laser-induced breakdown spectroscopy (LIBS).

8. A system comprising: An optical assembly configured to guide a laser beam to irradiate a segment of a substrate, wherein the laser beam is configured to remove a layer formed on the segment; A detection assembly configured to simultaneously detect spectral components of layer material indicating removal from the layer from light emitted from the segment in response to an irradiating laser beam; An additional detection assembly configured to detect additional spectral components of substrate material removed from the substrate by light emitted from the segment, wherein the spectral components and the additional spectral components are detected simultaneously; and A processor configured to control or stop the laser beam from illuminating the segment based on detected spectral components.

9. The system of claim 8, wherein the optical assembly is configured to guide a pulsed laser beam.

10. The system of claim 8, wherein the optical assembly comprises at least one of an acousto-optic modulator (AOM), a scanning mirror, and a focusing optics.

11. The system of claim 8, wherein the substrate comprises a printed circuit board (PCB) having a laminate and the layer comprises copper defects.

12. The system of claim 8, wherein the processor is configured to set the stop time based on both the spectral component and the additional spectral component.

13. The system of claim 8, wherein in response to detecting that both the spectral component and the additional spectral component are above a predefined threshold, the processor is configured to redirect the laser beam to irradiate the layer within the segment.

14. The system of claim 8, wherein the processor is configured to control or stop the laser beam by performing at least one operation selected from a list of operations consisting of: (i) blocking the laser beam, (ii) turning off the laser beam, (iii) adjusting the power, and (iv) directing the laser beam to a subsequent segment of the substrate.

15. The system of claim 8, wherein the detection assembly is configured to detect one or more spectral emissions selected from a list of spectral emissions consisting of: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) laser-induced breakdown spectroscopy (LIBS).

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