KR20230107364A - Controlling the laser repair process of electronic circuits using the spectral components of the light induced and emitted during repair - Google Patents

Abstract

The method includes directing a laser beam to impinge on a section of a substrate to remove a layer formed on the section. From the light emitted from the section in response to the colliding laser beam, at least a spectral component representative of the layer material removed from the layer is detected. Based on the detected spectral components, the laser beam is controlled or the laser beam is stopped from impinging on the section.

Description

Controlling the laser repair process of electronic circuits using the spectral components of the light induced and emitted during repair

The present invention relates generally to the manufacture of electronic products, and specifically to methods and systems for controlling the laser repair process of electronic circuits.

Various techniques have been developed to control processes such as laser-based repair of electronic circuits.

For example, US Patent Application Publication No. 2005/0226287 describes a laser processing system having a femtosecond laser, frequency conversion optics, beam manipulation optics, target motion control, processing chamber, diagnostic system and system control modules. The laser machining system enables the utilization of heat control inherent in micromachining, and the system has greater output beam stability, continuously variable repetition rate and unique temporal beam shaping capabilities.

US Patent Application Publication No. 2007/0092128 discloses an apparatus and method for automatically inspecting and repairing a printed circuit board that includes an inspection function that automatically inspects the printed circuit board and provides a machine-readable indication of areas requiring repair. described The automatic repair function uses machine readable indicia to repair printed circuit boards in some of the areas requiring repair. The auto-repair reconstruction function automatically re-inspects the printed circuit boards after an initial auto-repair operation and provides the auto-repair function with a reconstructed machine-readable indication of areas requiring repair.

Embodiments of the invention described herein provide a method comprising directing a laser beam to impinge on a section of a substrate to remove a layer formed on the section. From the light emitted from the section in response to the colliding laser beam, at least a spectral component representative of the layer material removed from the layer is detected. Based on the detected spectral components, the laser beam is controlled or the laser beam is stopped from impinging on the section.

In some embodiments, directing the laser beam includes directing a pulsed laser beam. In other embodiments, the substrate includes a printed circuit board (PCB) with a laminate and the layer includes copper defects. In yet other embodiments, the method includes detecting, from light emitted from the section, an additional spectral component indicative of substrate material removed from the substrate.

In an embodiment, controlling or stopping the laser beam includes setting a stopping 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 exceed a predefined threshold, the laser beam is redirected to impinge on a layer within the section.

In some embodiments, controlling or stopping the laser beam includes: (i) blocking the laser beam, (ii) switching off the laser beam, and (iii) directing the laser beam to a subsequent section of the substrate. and performing at least one operation selected from an operation list consisting of the requested operation. In other embodiments, detecting at least the spectral component includes: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) Laser Induced Breakdown Spectroscopy (LIBS). ) and detecting one or more spectral emissions selected from a list of spectral emissions consisting of.

According to an embodiment of the present invention, a system including an optical assembly, a detection assembly and a processor is further provided. The optical assembly is configured to direct a laser beam to impinge on a section of the substrate, and the laser beam is configured to remove a layer formed on the section. The detection assembly is configured to detect, from light emitted from the section in response to the impinged laser beam, a spectral component indicative of the layer material removed from the layer. The processor is configured to control the laser beam or stop the laser beam from impinging on the section based on the detected spectral components.

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

The invention will be more fully understood from the following detailed description of embodiments of the invention, taken in conjunction with the drawings.

1 is a block diagram of a system for repairing electronic circuits using a laser, in accordance with an embodiment of the present invention;
2A, 2B and 2C are graphs illustrating spectral components of emitted light representing copper removed from a substrate, according to an embodiment of the present invention; and
3 is a flow diagram schematically illustrating a method for process control using spectral components of light emitted from a defect during the process of removing a defect from an electronic circuit, according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION From time to time, various types of defects may occur, such as during the manufacturing process of an electronic component or module within a printed circuit board (PCB). For example, when forming a pattern of copper traces on a laminated board of a PCB, a defect including an unwanted copper layer between the copper traces may occur. In order to maintain the functionality of the PCB, it is important to remove defects without damaging the laminate, which is typically underneath the copper.

Embodiments of the present invention described below provide improved techniques for repairing an electronic module such as a PCB by eliminating defects generated during manufacture of the PCB. Defects including, for example, undesirable copper layers formed between traces of a designed copper pattern formed on a laminate of a PCB are eliminated.

In principle, it is possible to remove defects from a section of a PCB by using an iterative process that excises a portion of the defect, then inspects the section, and repeats the process until the entire defect is removed. However, while this iterative process reduces the risk of damaging the PCB laminates, each inspection step is time consuming and reduces the throughput of the defect removal process.

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 direct the laser beam impinging on a section of the PCB substrate. The laser beam is configured to remove defects formed on the section, using the impinged laser beam to ablate unwanted or excess copper layers. In the context of the present disclosure and claims, the term “copper layer” refers to any class of undesirable copper defects, including but not limited to excess copper sections, or residual copper, or copper splashes, or excess copper patterns, or segregation. Refers to a copper defect, or a combination of copper and foreign matter, or any other class of defect that includes copper.

In some embodiments, the one or more detection assemblies are configured to detect a spectral component indicative of copper removed from the defect from light directed to and emitted from the section in response to the impinged laser beam.

Note that the interaction between the laser beam and the excess copper in the defect leads to light emitted from the defect in the section. Accordingly, in the context of the present disclosure and claims, the term "emitted light" refers to light that is directed in response to a laser beam impinging on the copper, such that the guided light is emitted from the ablated copper.

Also, in the context of this disclosure and claims, the term “spectral component” refers to one or more spectral lines and/or other elements of copper that are of interest to be detected. For example, a spectral component of copper may have one or more of the following spectral lines having wavelengths of about 5700 Angstroms (A), about 5782 A, about 6000 A, and about 6150 A, and any other suitable wavelength. can include

The term spectral component may also refer to the spectral component emitted by the laminate or any other material of interest.

Note that the spectral components constitute a fingerprint for the presence of copper defects on the substrate of the PCB and for the ablation process to remove unwanted copper defects.

In some embodiments, using the disclosed techniques for removing a defect has several advantages, including but not limited to: (a) Defect Identification - Detecting one or more spectral components emitted during ablation is the presence of a defect. and is independent of the intensity of the detected signal, which may vary due to geometric factors such as, for example, surface roughness or shape of the defect, (b) accurate spatial monitoring - the same laser beam is used for ablation and emission of light and for deriving the detected spectral components, so that optical aiming errors may not occur and the detected spectral components are emitted from the actual position being ablated, and (c) real-time display and control - detection As the assemblies receive in real time one or more spectral components emitted in response to each pulse of the laser beam impinging on the defective section, enabling real-time control and adjustment of the ablation process detailed herein.

In some embodiments, the processor controls the laser beam, eg, reduces laser power, and/or changes scan speed, and/or adjusts beam profile, and/or beam spot size; and and/or to control any other suitable parameter of the laser beam.

In other embodiments, the processor: (i) sets a break time for the laser beam based on the detected spectral component, and subsequently or simultaneously (ii) causes the laser beam to impinge on the section at the set break time. configured to stop In the context of the present disclosure and claims, the term downtime is also referred to herein as the “end-point” of ablating copper defects.

In some embodiments, the optical assembly can include an acousto-optic modulator (AOM), which: (a) blocks or passes (on/off) the laser beam from reaching the PCB; (b) blocks the laser beam from reaching the PCB; and (c) control the number of pulses of the laser beam that pass through the AOM and impinge on the surface of the PCB.

In some embodiments, the processor is configured to stop the laser beam from impinging on the surface of the PCB section by controlling the AOM or other components of the optical assembly.

In some embodiments, (i) the detection assemblies may include high-speed spectrometers configured to detect, from the emitted light, at least one additional spectral component, and/or (ii) the system includes one or more additional detection assemblies. can do. The detection assemblies (eg, high-speed spectrometers) and/or one or more additional detection assemblies provide additional spectra, from light directed and emitted during the ablation process, representative of the substrate material, eg, laminate, removed from the PCB section during ablation. configured to detect the component.

In some embodiments, in response to receiving a signal representative of the laminate spectral component from the additional detection assembly, the processor is configured to establish a stopping point based on the laminate spectral component.

In some embodiments, the system may be used prior to ablation, eg, to accurately direct a laser beam to a defect, and/or to verify, eg, that the entire defect has been removed and no damage has occurred to the laminate; After ablation, it may include a camera assembly configured to acquire images of the PCB section.

In some embodiments, after finishing defect removal from a section, the processor is configured to move the PCB relative to the optical assembly to position the optical assembly to remove a subsequent defect located in a subsequent section of the PCB.

The disclosed techniques are applicable with modifications necessary to repair other types of electronic components and modules, such as but not limited to flat panel displays (FPD).

Further, the disclosed technology reduces cycle time and increases accuracy of repair processes of PCBs and other electronic components and modules, thereby reducing production cost and improving quality of PCBs and electronic products.

system description

1 is a block diagram of a system 11 for repairing electronic circuits of a sample 21, in accordance with an embodiment of the present invention. In this example, sample 21 includes a printed circuit board (PCB), but in other embodiments, sample 21 can be any other suitable type of component or module on an electronic product, as described below. can include

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

In the context of the present disclosure and claims, the terms "laser beam 25", "beam 25" and "laser beam" are used interchangeably and are emitted from the laser 12 towards the sample 21 and the system refers to the beam manipulated by the components of the optical assembly 13 of (11), which are described in detail herein.

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

In some embodiments, optics 14 are configured to shape and focus beam 25 prior to entering AOM 16 and (a) block laser beam 25 directed at sample 21 . or pass (on/off), (b) control the intensity of the beam 25, and (c) control the number of pulses of the beam 25 passing towards the sample 21.

In some embodiments, scanner 18 may include a scanning mirror or any other suitable type of scanner, which may be used to remove a layer, such as copper, formed on each section of sample 21 . configured to direct the beam 25 to impinge on a section of the Scanner 18 uses any scanning scheme (interleaved scanning scheme, or helical scanning scheme, or any other class of scanning scheme) over intended locations on the surface of sample 21 at any suitable scan rate. (For example, but not limited to, typical scan speeds are from about 10 mm/sec to about 1000 mm/sec).

In the context of this disclosure, the term “about” or “approximately” for any numerical values or ranges refers to a suitable dimensional tolerance that enables a portion or collection of components as described herein to function for its intended purpose. indicate

In some embodiments, focusing optics 24 are configured to focus beam 25 directed to intended locations on the surface of sample 21 . As shown in FIG. 1 , optical assembly 13 is configured to scan laser beam 25 to impinge on a desired section of sample 21 .

During beam scanning, a first beam 25 may impinge on a first section of sample 21 at approximately a right angle, and a second beam 25 may impinge on a surface of a second section that differs at any suitable angle other than a right angle. Be aware that phases may collide.

Reference is now made to inset 19 showing the surface of a section of sample 21 . In this example, a section of sample 21 includes a layer 22 comprising copper or copper alloy patterned on a substrate 23, such as a laminate of a PCB described above. Occasionally, defects 17 in the copper, in this example, an unwanted excess pattern, may occur during the creation of the PCB. Excessive patterning of copper can cause, for example, electrical shorts between the traces of layer 22, which can impair the functionality of the PCB.

Reference is now made again to the general view of FIG. 1 . In some embodiments, system 11 directs beam 25 to impinge on the surface of each section to remove defect 17 using a laser ablation process, thereby removing sample 21. It is configured to repair such a defect 17 that occurred on a section of . In response to the colliding laser beam 25, light is emitted from the surface of the sample 21. In this example, as shown in FIG. 1 , a portion of the light (referred to herein as beam 30, which is an axial beam) is approximately orthogonal from sample 21, and other beams of light (herein beams 32) are , which are off-axis beams) come from the sample 21 at different angles.

Detection of spectral components representing copper removed from the substrate

In some embodiments, system 11 includes detection assemblies (DAs) 34 and 44 configured to detect beams 30 and 32 , respectively. Compared to beam 32, beam 30 is detected as it passes through focusing optics 24, and thus typically (but not necessarily) has more information than is received from beam 32, as well as Note that it contains different information. Note that beams 32 do not pass through focusing optics 24 and thus have less interference compared to beam 30 . Accordingly, the combination of beams 30 and 32 provides complementary light directed and emitted from sample 21 .

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 representative of the copper in defect 17 removed from substrate 23 of sample 21 during the ablation process.

In some embodiments, DA 34 has one or more components configured to pass one or more respective spectral components representative of copper (also referred to herein as copper spectral components) and to block other spectral components of beam 30. It includes a filter (37). DA 34 includes (i) optics 36 configured to focus emitted light comprising one or more copper spectral components (SCs) that pass through one or more filters 37, and (ii) copper SCs. It further includes one or more detectors 35 configured to detect.

In some cases, at least a portion of the laser beam 25 may reflect and/or scatter from the surface of the sample 21, causing saturation of one or more detectors 35, thereby rendering the spectral component of interest invisible. can

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

In the context of the present disclosure, the detected spectral components constitute a fingerprint indicative of the presence of unwanted copper and ablation of defects 17 formed undesirably on the surface of the substrate 23 .

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

In some embodiments, DAs 34 and 44 can emit any suitable type of spectral emission, such as (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (E) LIBS. (Laser Induced Breakdown Spectroscopy) is configured to detect one or more spectral emissions selected from a list of spectral emissions.

In some embodiments, system 11 includes processor 33 configured to receive signals from DAs 34 and 44 indicative of a detected copper SC. Based on the received signals, the processor 33 sets a stop time for directing the laser beam 25 to the defect 17 on the section of the sample 21 and sets the stop time of the laser ablation process (herein also referred to as the end point at ) to stop the beam 25 from impinging on the section.

In some embodiments, processor 33 may use active components, such as but not limited to, of optical assembly 13 to stop beam 25 from impinging on the aforementioned section of sample 21 . It is configured to control the laser 12, the AOM 16 and the scanner 18. In the example of FIG. 1 , system 11 includes controller 46 configured to control AOM 16 , and 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 controllers described above are configured to exchange control signals and other types of data with the processor 33.

In some embodiments, processor 33 is configured to synchronize operation of DAs 34 and 44 with laser beam 25 impinging on a section of sample 21 . For example, processor 33 may be configured to detect light emitted only at a predefined time delay (e.g., several microseconds) after one or more pulses of laser beam 25 impinge on defect 17. configured to “open” at least one of DAs 34 and 44 for Note that, as the emission of spectral components can be time dependent, controlling the detection timing can improve the signal-to-noise ratio (SNR) of the detected spectral components.

In some embodiments, laser 12 is any suitable laser configured to emit pulses of laser beam 25, such as, but not limited to, a passive Q-switched micro laser supplied by Teem Photonics, Grenoble, France. include In these embodiments, processor 33 is used to stop or pass beam 25 applied to sample 21 by laser 12 and to set the intensity and number of pulses of beam 25. configured to control the AOM 16 for

In yet other embodiments, system 11 is coupled with laser 12 - to the same location on sample 21 that is aligned with the optical path of laser 12 and from which laser 12 directs laser beam 25. It may include an ultraviolet (UV) laser - configured to direct a UV beam.

In some embodiments, DAs 34 and 44 or additional DAs are configured to detect the spectral response emitted from sample 21 . that the detected spectral response is enhanced by the UV beam and the DAs are configured to produce a signal with improved SNR (due to the presence of the UV beam) representative of the detected one or more spectral components of the copper emitted from defect 17 Note that

In some embodiments, processor 33 holds one or more sections of sample 21 having defect 17 to be removed by laser ablation. Processor 33 is configured to control the process of repairing defects 17 in each section by controlling scanner 18 to scan laser beam 25 through one or more respective sections of sample 21 .

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. do. Images acquired by the camera module 20 are taken, for example, to review the target section before and/or after the removal of the defect 17 by the laser beam 25, or the sample 21 with the defect 17. ) can be used for other purposes, such as navigating the system 11 to sections of .

In some embodiments, CA 20 includes a camera optical assembly (COA) (not shown) configured to direct a light beam to illuminate sample 21 , and light reflected from sample 21 . and a camera (not shown) configured to receive beam 28 through BS 15 . CA 20 is configured to transmit acquired images to processor 33 .

In some embodiments, processor 33 is configured to prevent optical aiming errors that may occur between CA 20 and laser beam 25 to a desired location on the surface of sample 21 .

In other embodiments, visual verification that defect 17 has been removed from sample 21 is required because processor 33 is configured to set a pause time for directing laser beam 25 to sample 21 . may not be, and thus the CA 20 may be omitted from the configuration of the system 11.

In some embodiments, system 11 uses signals received from DAs 34 and 44 and processor 33, active components of system 11 (e.g., laser 12, AOM). and electrical cables 40 configured to conduct control signals exchanged between (16) and scanner (18), and camera assembly (20).

Typically, processor 33 includes a general purpose processor programmed with software to perform the functions described herein. The software may be downloaded to the processor in electronic form, for example over a network, or alternatively or additionally may be provided and/or stored on a non-transitory tangible medium such as magnetic, optical, or electronic memory. Similarly, the controllers described above include general purpose controllers programmed with software to perform the functions described herein.

Detection of spectral components representing substrate material removed from the substrate

In some cases, the laser beam 25 is directed (intentionally or unintentionally) to the sidewall of a defect 17 located in the aforementioned section of the sample 21, for example when the laser beam 25 is directed. , on the defect 17 containing the excess pattern of copper, and on the substrate 23 simultaneously.

In some embodiments, system 11 includes one or more additional detection assemblies configured to detect from beams 30 and 32 an additional spectral component representative of substrate material, eg, a laminate, removed from substrate 23 during ablation. not shown).

In some embodiments, DAs 34 and 44 may include additional filters (not shown) configured to pass spectral components of the laminate that are inadvertently removed from substrate 23 during ablation. These additional filters are configured to block other (non-laminated) spectral components of beams 30 and 32.

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

In some embodiments, when beam 25 impinges on both defect 17 and substrate 23 simultaneously, copper and laminate may be ablated from sample 21 . In response to the ablation, processor 33 may receive signals representative of both the copper spectral components and the laminate spectral components from DAs 34 and 44 or from one or more additional DAs described above. In these embodiments, processor 33 directs (i) laser beam 25 to sample 21 to ablate copper from defect 17 without ablating any other material from laminate or substrate 23. and (ii) redirect the laser beam 25 to impinge only on the defect 17.

In other embodiments, at least one of the DAs 34 and 44 is a spectrometer configured to detect a spectral component of copper from at least one of the beams 30 and 32 and to generate a signal indicative of the detected spectral component of the copper. can include In an embodiment, the spectrometer may include a multi-element line sensor/detector based spectrometer from Ocean Insight of Rochester, NY, USA.

In some embodiments, the spectrometer may also be configured to simultaneously detect and generate signals representative of spectral components of both copper and laminate, such that in response to receiving these signals, processor 33 generates laser beam 25 The impact on the substrate 23 can be stopped.

In some embodiments, at least one of detectors 35 and 45 and/or at least one of the foregoing spectrometers have high-speed detection capability to shorten detection time and enhance real-time monitoring and control of the ablation process. can include In such embodiments, at least one of the detectors 35 and 45 is a high-speed photodiode, eg, provided by Thorlabs Inc., Newton, NJ, and/or an Ocean, eg, Rochester, NY. It can include high-speed spectrometers produced by Insight.

In alternative embodiments, system 11 may be configured with DAs and/or spectrometers and/or any other device configured to detect spectral components of copper and/or other foreign material constituting defect 17 on substrate 23. Any suitable combination of suitable subsystems may be included.

In some embodiments, processor 33 obtains, from a defect inspection system (not shown) the coordinates of first and second defects 17 located in first and second respective sections of sample 21 . You can receive a defect file containing In some embodiments, processor 33 motion controls to position the first section proximate optical assembly 13 to remove the first defect using laser beam 25, as described above. subsystems (not shown). In some embodiments, after terminating the ablation of the first defect, for example by setting a stop time and stopping the laser beam 25 from impinging on the first section at the set stop time, the processor 33 is configured to control the optical assembly 13 to direct the laser beam 25 to the second section to remove the second defect. For example, the processor 33 controls the AOM 16 to block the laser beam 25 from impinging on the first section, and to perform ablation of the second defect in the second section, the sample ( 21) and the laser 12 relative to each other, for example, may also control the motion control subsystem described above. Additionally or alternatively, if the first and second defects are close to each other, after finishing the removal of the first defect, the processor 33 directs the laser beam 25 to the second defect without using the motion control system. The scanner 18 can be controlled to redirect to .

As described above, after completing the removal of one or more defects 17 from the first and second sections of sample 21, the processor 33 performs verification of the defect removal from the first and second sections. To perform, it is configured to control the motion control subsystem to move the sample 21 relative to the system 11 .

In some embodiments, system 11 is configured to ablate another class of defects occurring on a surface comprising a material other than laminate, and/or other classes of surfaces such that the defect comprises a material other than copper. .

For example, polymer defects may occur in sections with designed patterns of copper, eg during solder mask processing. In such embodiments, the optical assembly 13 is configured to direct the laser beam 25 to the polymer defect, and at least one of the DAs 34 and 44 is affected by the laser beam 25 impinging on the defect. configured to detect one or more spectral components from which it is derived. One or more spectral components are emitted from the polymer defect as components of light beams 30 and 32 and are detected by at least one of DAs 34 and 44 .

In these embodiments, the processor 33 is configured to control the ablation process based on at least the polymer defect and the detected spectral components of the copper pattern. Accordingly, when the detected signals represent one or more spectral components of copper and/or in the absence of a spectral component of a polymer defect in the detected signals, the processor 33 causes the laser beam to impinge on the section containing the polymer defect. or control the optical assembly to control parameters of the laser beam 25, for example for attenuation of the laser beam 25.

This specific configuration of system 11 is shown as an example to illustrate specific problems addressed by embodiments of the present invention, and to demonstrate application of such embodiments in improving the performance of such a system. However, embodiments of the present invention are in no way limited to this particular class of exemplary system, and the principles described herein may be similarly applied to other classes of defect repair systems.

2A is a graph 70 showing the detection of one or more copper spectral components 72 of light emitted over time from a sample 21 during ablation of a defect 17, in accordance with an embodiment of the present invention. The vertical axis represents the intensity of one or more copper spectral components, and the horizontal axis represents the time axis.

In the example of FIG. 2A , the defect 17 comprises copper having a thickness of 18 μm. Biaxial axis 76 shows the ablation time of defect 17, while markers 78 and 79 show the start time of the laser and the stop time of the spectral component emitted from the copper layer, respectively. In the example of FIG. 2A , the ablation time is about 85 milliseconds. Graph 70 also shows the noise 74 of the detection. Note that after marker 79, since defect 17 has been removed, copper spectral component 72 does not appear in graph 70. Note that when the copper spectral component disappears, the laser is turned off to avoid or minimize unwanted damage to the underlying laminate layer.

In some embodiments, processor 33 is configured to set the ablation stop time using any suitable technique. For example, the processor 33 may set a threshold for the signal strength of the copper spectral component 72 . In this example, when the signal strength is lower than the threshold over a predefined time interval, the processor 33 determines that, at the set stop time indicated by the marker 79, the laser beam 25 has a defect 17. Controls, for example, AOM 16 and scanner 18 to stop crashing onto sections. In other embodiments, processor 33 may use any other suitable technique to set the ablation stop time.

2B is a graph 80 showing the detection of the copper spectral component 82 of light emitted from a sample 21 over time during ablation of a defect 17, in accordance with an embodiment of the present invention. The vertical axis represents the intensity of copper spectral components, and the horizontal axis represents the time axis.

In the example of FIG. 2B , the defect 17 comprises copper having a thickness of 12 μm. Biaxial axis 86 shows the ablation time of defect 17, while markers 88 and 89 show the start time and stop time of ablation, respectively. In the example of FIG. 2B , the ablation time is about 45 milliseconds, which is significantly lower than the ablation time of FIG. 2A described above. Graph 80 also shows the noise 84 of the copper spectral component. Note that after marker 89, since defect 17 has been removed, copper spectral component 82 does not appear in graph 80.

In some embodiments, processor 33 is configured to set the ablation stop time indicated by marker 89 using any suitable technique, as described in FIG. 2A above.

2C is a graph 90 showing the detection of the copper spectral component 92 of light emitted from sample 21 over time during ablation of defect 17, in accordance with an embodiment of the present invention. The vertical axis represents the intensity of copper spectral components, and the horizontal axis represents the time axis.

In the example of FIG. 2C , the defect 17 includes copper having a thickness of 7 μm. Biaxial axis 96 shows the ablation time of defect 17, while markers 98 and 99 show the start time and stop time of ablation, respectively. In the example of FIG. 2C , the ablation time is about 20 milliseconds, which is significantly lower than the ablation times of FIGS. 2A and 2B described above. Graph 90 also shows noise 94 of copper spectral components. Note that after marker 99, since defect 17 has been removed, copper spectral component 92 does not appear in graph 90.

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

Reference is now made to the general view of graphs 2a, 2b and 2c based on experiments performed by the inventors of the present invention, for example, to demonstrate the disclosed concept. In some embodiments, processor 33 is configured to set the stop time based on the detected spectral component of copper in defect 17 . Graphs 2a, 2b and 2c show similar start times by respective markers 78, 88 and 98, and different stop times by respective markers 79, 89 and 99. As explained above, the shutdown times are set by processor 33 due to the respective thicknesses of copper of defect 17 (18 μm, 12 μm, and 7 μm).

In other embodiments, system 11 may include one or more additional DAs configured to detect the spectral component of the laminate or any other material of substrate 23 that is ablated by laser beam 25 . In these embodiments, the laminate spectral component is not detected by DAs 34 and 44 and is therefore not used by processor 33 to set the downtime of the ablation process to remove defect 17. don't

In this example, in the examples of Graphs 2a, 2b and 2c, the copper spectral component can only be detected by DA 34.

In other embodiments, processor 33 is configured to retain a threshold for detection of a laminate spectral component. In these embodiments, upon receiving a signal from one or more of the additional DAs described above, including a level of the laminated spectral component at a level higher than the threshold, the processor 33 causes the stop time to be set and the laser beam 25 to It is configured to control, for example, the AOM 16 and/or the scanner 18 to stop crashing on the section with the defect 17 .

As described in FIG. 1 above, the processor 33 may control the AOM 16 to block the laser beam 25 from colliding on each section. Alternatively, the processor 33 directs the laser beam 25 to impinge on another section of the sample 21 to remove another defect 17 generated on the substrate 23, the sample ( 21) to move relative to laser 12 and/or the motion control subsystem described above.

3 is a flow diagram schematically illustrating a method for controlling the process using the spectral components of light emitted from defects 17 during the process of removing defects 17 from a sample 21 according to an embodiment of the present invention. am.

The method includes a laser directing step 100 in which a laser beam 25 is directed to impinge on a section of a substrate 23 of a sample 21, to remove the copper layer of defects 17 generated on the section. It begins. In this example, sample 21 comprises a PCB having a substrate 23 comprising a laminate.

In the detection step 102, in response to the colliding laser beam 25, at least one of the DAs 34 and 44 detects the removed copper from the sample 21 from the light emitted from the section of the sample 21. Detect the spectral components that represent

Note that the detected spectral components constitute a fingerprint for the presence of an unwanted copper layer on the surface of the substrate 23 and for its ablation process.

In decision step 104 the processor 33, which has a predefined threshold for the emitted level of one or more spectral components SC, checks whether the detected SC exceeds the threshold. For example, on the one hand, when the detected SC of copper exceeds the copper SC threshold, the ablation is not complete. On the other hand, in the absence of copper SC in the detected signals, or when the level of copper SC detected is below the copper SC threshold, ablation should be stopped or at least adjusted to avoid damage to the laminate layer of the section. Accordingly, if the detected SC of copper exceeds the threshold, the method returns to step 100 to continue ablation of the copper layer at defect 17 .

If the detected SC of copper is less than the copper SC threshold, the method proceeds to ablation control step 104, and the method ends. In 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 a copper SC, the processor may set a stop time (shown as markers 79, 89 and 99 of graphs 70, 80 and 90, respectively) for laser beam 25. . As described in FIGS. 1 and 2 above, the stop time is based on the detected copper spectral component of the light (e.g., beams 30 and 32) emitted from the ablated defect 17. The process 33 is also configured to stop the laser beam 25 from impinging on the section of the sample 21 at the set stop time.

In other embodiments, for example, when the copper SC is still detected but at a level lower than the copper SC threshold, the processor 33 determines the value of the laminate material of the sample 21 (e.g., the PCB described above). It is configured to control the optical assembly to steer the laser beam 25 to prevent or minimize damage.

As described in FIG. 1 above, in other embodiments, at least one of the DAs 34 and 44 is configured to detect a spectral component of a laminate of a PCB or other material. In such embodiments, in detection step 102, in addition to the copper spectral component, DAs 34 and 44 may detect a spectral component representative of the laminate removed from sample 21.

Also in these embodiments, in decision step 104, the processor checks whether one or more SCs other than copper SCs, eg laminated SCs, have been detected by one or more of DAs 34 and 44. It consists of If not, the method returns to step 100 to proceed with ablation as described above.

In case more than one laminate SC is detected, the method proceeds to step 104 to control or stop the laser beam 25 . For example, control the impingement position of the laser beam 25 to ablate the defect 17 without damaging the laminate, or stop the laser beam 25 from impinging on each section, thereby cutting the laminate. prevent damage

While the embodiments described herein primarily address the removal of copper defects generated on a PCB, the methods and systems described herein also use laser ablation to remove any type of defect from any type of substrate. drilling holes and/or vias through the copper layer, and where it is important to stop laser drilling to avoid damaging layers and/or laminates located close to designed holes/vias. other laser-based processes for creating electronic circuits, such as, but not limited to, controlling a laser beam.

Accordingly, it will be understood that the embodiments described above are cited as examples, and that the present invention is not limited to that specifically shown and described above. Rather, the scope of the present invention is intended to cover both combinations and subcombinations of the various features described above, as well as modifications and variations thereof that may occur to those skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Also includes

Documents incorporated by reference in this patent application are such that any terms in such incorporated documents are defined in such a way as to conflict with definitions explicitly or implicitly made herein, so that only the definitions herein are to be considered. Except for the scope, it is to be considered an integral part of this application.

Claims (17)

As a method,
directing a laser beam to impinge on a section of the substrate to remove a layer formed on the section;
detecting from light emitted from the section in response to the impinged laser beam at least a spectral component representative of the layer material removed from the layer; and
based on the detected spectral component, controlling the laser beam or stopping the laser beam from impinging on the section. The method of claim 1 , wherein directing the laser beam comprises directing a pulsed laser beam. The method of claim 1 , wherein the substrate comprises a printed circuit board (PCB) having a laminate and the layer comprises a copper defect. The method of claim 1 including detecting from light emitted from the section an additional spectral component indicative of substrate material removed from the substrate. 5. The method of claim 4, wherein controlling or stopping the laser beam includes setting a stopping time based on both the spectral component and the additional spectral component. 5. The method of claim 4, wherein in response to detecting that both the spectral component and the additional spectral component exceed a predefined threshold, redirecting the laser beam to impinge on the layer in the section. . The method of claim 1, wherein controlling or stopping the laser beam comprises: (i) blocking the laser beam, (ii) switching off the laser beam, (iii) adjusting power, and (iv) performing at least one action selected from a list of actions consisting of directing the laser beam to a subsequent section of the substrate. The method of claim 1 , wherein detecting at least the spectral components includes: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) LIBS ( and detecting one or more spectral emissions selected from a list of spectral emissions consisting of Laser Induced Breakdown Spectroscopy. As a system,
an optical assembly configured to direct a laser beam impinging on a section of the substrate, the laser beam configured to ablate a layer formed on the section;
a detection assembly configured to detect, from light emitted from the section in response to the impinged laser beam, a spectral component indicative of layer material removed from the layer; and
and a processor configured to control the laser beam or stop the laser beam from impinging on the section based on the detected spectral component. 10. The system of claim 9, wherein the optical assembly is configured to direct a pulsed laser beam. 10. The system of claim 9, wherein the optical assembly includes at least one of an acousto-optic modulator (AOM), a scanning mirror, and focusing optics. 10. The system of claim 9, wherein the substrate comprises a printed circuit board (PCB) having a laminated plate, and wherein the layer comprises copper defects. 10. The system of claim 9 including an additional detection assembly configured to detect additional spectral components indicative of substrate material removed from the substrate from light emitted from the section. 14. The system of claim 13, wherein the processor is configured to set a stop time based on both the spectral component and the additional spectral component. 14. The method of claim 13, wherein in response to detecting that both the spectral component and the additional spectral component exceed a predefined threshold, the processor redirects the laser beam to impinge on the layer in the section. system, which is configured. 10. The method of claim 9, wherein the processor: (i) blocks the laser beam, (ii) switches off the laser beam, (iii) adjusts power, and (iv) controls the laser beam and to control or stop the laser beam by performing at least one action selected from a list of actions consisting of directing to a subsequent section of the substrate. 10. The method of claim 9, wherein the detection assembly is configured to obtain from a spectral emission list consisting of: (a) fluorescence, (b) plasma, (c) Raman, (d) infrared thermal radiation, and (e) Laser Induced Breakdown Spectroscopy (LIBS). and configured to detect the selected one or more spectral emissions.

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