Laser slotted hole processing method for thin solder mask substrate

Abstract

The invention relates to a laser slotted hole processing method for a thin solder mask substrate, which comprises the following steps of: setting a preset laser power value, a preset transmitting value and a preset hole shape shade value for a laser machine, and setting a plurality of different galvanometer partition values and galvanometer jumping speed values according to the preset slotted hole size; a plurality of different galvanometer partition values are combined with a plurality of different galvanometer jumping speed values to form a plurality of different first test groups; performing laser processing on different positions of the first test substrate based on the parameters of the plurality of first test groups, and forming a plurality of slotted holes; and taking out the first test substrate which is processed for multiple times, and performing appearance inspection. According to the method, the galvanometer partition value and the galvanometer jumping speed value are combined, the laser drilling test is carried out on the unique test substrate, proper optimal parameters are selected, and the laser slotted hole of the thin solder mask substrate is manufactured in mass production by means of a laser processing method.

Description

Technical Field

[0001] This invention relates to a circuit board processing method, and more particularly to a laser slotting method for thin solder resist substrates. Background Technology

[0002] The description in this section provides only background information related to the disclosure of this invention and does not constitute prior art.

[0003] A novel type of circuit board with a thin solder resist substrate is available. In some applications, the thin solder resist substrate needs to be slotted to facilitate copper filling later. Currently, the industry commonly uses a developing process to create the opening in the solder resist, but this method has limited accuracy and resolution. Traditional developing processes require repeated adjustments to multiple parameters such as solution concentration, spray pressure, and conveyor speed, making the process cumbersome, time-consuming, and prone to inter-parameter interference, resulting in inconsistent stability. Furthermore, the developing process requires testing on a whole-board basis, necessitating the fabrication of a new sample for each parameter adjustment, leading to low efficiency.

[0004] In some scenarios, laser drilling is also considered. However, laser drilling relies on high-precision laser ablation and contour control technology. The processing objects are mostly thicker or have different structures and compositions of the medium layer. It does not involve the precision slot processing of ultra-thin solder resist layers.

[0005] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a laser slotting method for thin solder resist substrates. By combining the galvanometer partition value and the galvanometer runout speed value, laser drilling test is performed on a unique test substrate, and suitable optimal parameters are selected. Laser slots on thin solder resist substrates can then be manufactured in mass production using laser processing methods.

[0007] To achieve the above objectives, the present invention discloses a method for laser-grooving holes in a thin solder resist substrate, the method comprising: Obtain the preset slot size; The first test substrate was placed on the table, and the processing area was evacuated. The laser machine is set with preset laser power value, emission value, and aperture mask value, and multiple different galvanometer partition values ​​and galvanometer runout speed values ​​are set according to the preset slot size. The absolute value of the difference between each of the galvanometer partition values ​​is within a first preset range, and the absolute value of the difference between each of the galvanometer runout speed values ​​is within a second preset range. Multiple different galvanometer partition values ​​are combined with multiple different galvanometer runout velocity values ​​to form multiple different first test groups; Based on the parameters of multiple first test groups, the first test substrate is laser-processed at different positions to form multiple slots; The first test substrate, after undergoing multiple processing steps, was removed and subjected to visual inspection.

[0008] As a further description of the above technical solution, in the step of "taking out the first test substrate after multiple processing and performing visual inspection", it is determined whether each of the slots has dimensional deviation, bottom copper dissolution, or solder mask floating. Finally, the first test group without dimensional deviation, bottom copper dissolution, or solder mask floating is selected as the first screening group, and the corresponding galvanometer partition value and galvanometer runout speed value are set for use in this batch of mass production laser processing.

[0009] As a further description of the above technical solution, after the step of "determining whether each of the slots has dimensional deviation, bottom copper dissolution, or solder resist detachment, and finally selecting the first test group without dimensional deviation, bottom copper dissolution, or solder resist detachment as the first screening group", the second test substrate is subjected to multiple laser processing based on the parameters of the screening group. Each slot of the second test substrate after laser processing was individually plasma cleaned. In the cleaning step, multiple different nitrogen, oxygen, carbon tetrafluoride, argon, cleaning power, and plasma time values ​​are set. The absolute value of the difference between the nitrogen values ​​is within a third preset range, the absolute value of the difference between the oxygen values ​​is within a fourth preset range, the absolute value of the difference between the carbon tetrafluoride values ​​is within a fifth preset range, the absolute value of the difference between the argon values ​​is within a sixth preset range, the absolute value of the difference between the cleaning power values ​​is within a seventh preset range, and the absolute value of the difference between the plasma time values ​​is within an eighth preset range. Multiple different values ​​of nitrogen, oxygen, carbon tetrafluoride, argon, cleaning power, and plasma time are combined to form multiple different second test groups; Each of the second test groups corresponds to a slot on the second test substrate, and each slot is individually plasma cleaned; after cleaning, the second test substrate is visually inspected.

[0010] As a further description of the above technical solution, in the step of "performing a visual inspection on the second test substrate after cleaning", it is determined whether the slots on the second substrate have solder resist surface filler, horizontal etching at the bottom of the hole, or micro-pits on the solder resist surface. Finally, the second test group without solder resist surface filler, horizontal etching at the bottom of the hole, or micro-pits on the solder resist surface is selected as the second screening group, and the corresponding nitrogen value, oxygen value, carbon tetrafluoride value, argon value, cleaning power value, and plasma time value are set for use in this batch of mass-produced plasma cleaning.

[0011] As a further description of the above technical solution, the galvanometer partition value is set to 15*15mm, and the galvanometer runout speed value is set to 5000mm / s.

[0012] As a further description of the above technical solution, the nitrogen value is set to 200 sccm, the oxygen value is set to 1600 sccm, the carbon tetrafluoride value is set to 80 sccm, the argon value is set to 200 sccm, the cleaning power value is set to 20 kW, and the plasma time value is set to 5 min.

[0013] As a further description of the above technical solution, in the step of "setting preset laser power value, emission value, and aperture mask value for the laser machine, and setting multiple different galvanometer partition values ​​and galvanometer runout speed values ​​according to the preset slot size", the twelve major areas sampled from the first test substrate are set as thickness measurement areas. Thick areas and thin areas are distinguished according to the thickness measurement data, and different sets of process parameters including laser power value, emission value, aperture mask value, galvanometer partition value, and galvanometer runout speed value are set for the thin areas and the thick areas.

[0014] As a further description of the above technical solution, in the step of "determining whether there are solder resist surface fillers, horizontal etching at the bottom of the hole, or micro-pits on the solder resist surface in the slots on the second substrate, and finally selecting the second test group without solder resist surface fillers, horizontal etching at the bottom of the hole, or micro-pits on the solder resist surface as the second screening group", the slots on the second substrate corresponding to the second screening group are checked for water droplet angle using a water droplet angle measuring instrument. If the water droplet angle is controlled within 10-30°, it is considered qualified.

[0015] As a further description of the above technical solution, the laser machine is configured as a green laser machine with a wavelength of 515nm.

[0016] As a further description of the above technical solution, the waveform of the laser machine is set to a flat-top light.

[0017] By employing the above technical solutions, the beneficial effects of the present invention are as follows: The laser-grooved hole processing method for thin solder resist substrates of the present invention can combine galvanometer partition values ​​and galvanometer runout speed values, perform laser drilling tests on a single test substrate, select suitable optimal parameters, and then use laser processing to fabricate laser-grooved holes in thin solder resist substrates during mass production. Specifically, this application selects the laser drilling method for thin solder resist substrates. Compared with the method of creating patterned openings using development, it only requires a single first test substrate to screen for optimal mass production parameters during the testing phase. The laser processing method of the present invention can perform parameter experiments in different areas on the same test substrate and observe the processing effect in real time, quickly obtaining the optimal parameters, greatly improving testing efficiency and reducing development and verification costs.

[0018] To further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a laser testing schematic diagram of a laser slotting method for a thin solder resist substrate provided in the embodiments of this specification; Figure 2 This is a cleaning test diagram of a laser slotting method for a thin solder resist substrate provided in the embodiments of this specification. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0022] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Furthermore, the accompanying drawings of the present invention are for simple illustrative purposes only and are not depictions of actual dimensions; this is stated in advance. The following embodiments will further describe the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0023] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the related listed items.

[0024] Please see Figure 1 This embodiment describes a laser slotting method for a thin solder resist substrate, wherein the laser slotting method for the thin solder resist substrate includes: Obtain the preset slot size; The first test substrate was placed on the table, and the processing area was evacuated. The laser machine is set with preset laser power value, emission value, and aperture mask value, and multiple different galvanometer partition values ​​and galvanometer runout speed values ​​are set according to the preset slot size. The absolute value of the difference between each of the galvanometer partition values ​​is within a first preset range, and the absolute value of the difference between each of the galvanometer runout speed values ​​is within a second preset range. Multiple different galvanometer partition values ​​are combined with multiple different galvanometer runout velocity values ​​to form multiple different first test groups; Based on the parameters of multiple first test groups, the first test substrate is laser-processed at different positions to form multiple slots; The first test substrate, after undergoing multiple processing steps, was removed and subjected to visual inspection.

[0025] Specifically, based on the above method, a 515nm green laser machine, model DRD3060III-2GN, can be selected to perform slot processing on solder resist ink with a thickness ≤10μm. The purpose is to achieve precise processing of slots with a width <50um and a length <100um on PSR-800 AUS SR1 ink.

[0026] Before using the laser machine, it needs to be calibrated. This involves automatic CCD and galvanometer calibration, with one CCD calibration point and at least three calibration cycles, controlled within 5µm. The galvanometer calibration points are set to 100, with one calibration cycle, controlled within 3µm, to improve the testing accuracy to a preset level. Afterward, the first test substrate is loaded and a vacuum is applied to fix it on the processing table, ensuring flatness and preventing vibration and displacement. After processing multiple first test groups, multiple slots are formed on the first test substrate. The table vacuum is then closed, and the first test substrate is removed. Each slot is then checked for dimensional deviations, bottom copper dissolution, and solder mask detachment. The first test group without dimensional deviations, bottom copper dissolution, or solder mask detachment is selected as the first screening group. The corresponding galvanometer partition values ​​and galvanometer runout speed values ​​are then set for use in this batch of mass-produced laser processing. The specific test results are as follows: Figure 1 ,in Figure 1 In test group 5, no dimensional deviations, bottom copper melting, or solder mask detachment were observed, and the slot condition was good, making it a suitable candidate for the first screening group. Specifically, based on the first screening group, in subsequent mass production, the galvanometer partition value can be set to 15*15mm, and the galvanometer runout speed value can be set to 5000mm / s.

[0027] In other words, in the above-mentioned processing, laser drilling tests can be performed on a single test substrate by combining the galvanometer partition values ​​and galvanometer runout speed values, and suitable optimal parameters can be selected. Laser processing methods can then be used to fabricate laser-cut slots in thin solder resist substrates during mass production. Specifically, this application selects laser drilling for thin solder resist substrates. Compared to methods that use development to create patterned openings, this method only requires a single first test substrate to screen for optimal mass production parameters during the testing phase. The laser processing method described in this invention allows for parameter testing in different areas on the same test substrate, with real-time observation of the processing effect, quickly obtaining optimal parameters, greatly improving testing efficiency and reducing development and verification costs.

[0028] However, after laser drilling is applied to thin solder resist substrates, plasma cleaning is performed. Due to the extremely small material thickness, the following defects are prone to occur during testing: exposure of the solder resist surface filler, leading to increased surface roughness and decreased adhesion; formation of micro-pits on the surface, affecting the flatness and electrical insulation performance of the circuit layer; and excessive lateral etching of the slot walls, resulting in hole deformation or dimensional deviation. To address these specific problems, this invention also provides a similar post-drilling processing testing method. After the step of "determining whether each slot exhibits dimensional deviation, bottom copper dissolution, or solder resist detachment, and finally selecting the first test group without dimensional deviation, bottom copper dissolution, or solder resist detachment as the first screening group", the second test substrate is subjected to multiple laser processing operations based on the parameters of the screening group. Each slot of the laser-processed second test substrate is then individually plasma cleaned. During the cleaning step, multiple different nitrogen, oxygen, carbon tetrafluoride, argon, cleaning power, and plasma time values ​​are set. The absolute value of the difference between the nitrogen values ​​is within a third preset range, and the absolute value of the difference between the oxygen values ​​is within a third preset range. The absolute values ​​of the differences are within a fourth preset range, the absolute values ​​of the differences of the various carbon tetrafluoride values ​​are within a fifth preset range, the absolute values ​​of the differences of the various argon values ​​are within a sixth preset range, the absolute values ​​of the differences of the various cleaning power values ​​are within a seventh preset range, and the absolute values ​​of the differences of the various plasma time values ​​are within an eighth preset range. Multiple different nitrogen, oxygen, carbon tetrafluoride, argon, cleaning power, and plasma time values ​​are combined to form multiple different second test groups. Each second test group corresponds to a slot on a second test substrate, and each slot is individually plasma cleaned. After cleaning, the second test substrate is visually inspected. Specifically, during visual inspection, it is determined whether the slots on the second substrate exhibit solder resist surface filler, transverse etching at the bottom of the hole, or micro-pits on the solder resist surface. Finally, the second test group without solder resist surface filler, transverse etching at the bottom of the hole, or micro-pits on the solder resist surface is selected as the second screening group. The corresponding nitrogen, oxygen, carbon tetrafluoride, argon, cleaning power, and plasma time values ​​are set for use in this batch of mass-produced plasma cleaning. Its detailed structure is as follows... Figure 2 As shown. Among them. Figure 2 In test group 5, no issues were observed with solder resist surface filler, transverse etching at the bottom of the hole, or micro-pits on the solder resist surface, indicating good cleaning condition. This group can be selected as the second screening group. Specifically, based on the second screening group, in subsequent mass production, the nitrogen value can be set to 200 sccm, the oxygen value to 1600 sccm, the carbon tetrafluoride value to 80 sccm, the argon value to 200 sccm, the cleaning power value to 20 kW, and the plasma time value to 5 min.

[0029] During the cleaning of the second test substrate described above, the amount of etching can be tested. A 10*10cm PP substrate is used, and the difference in weight before and after etching is used to control the etching amount within 0-2g to ensure compliance with quality requirements. Simultaneously, in specific steps, the second test substrate can be fixed using upper and lower gripper fixtures. The trolley is pushed into the cavity, and it is confirmed that the second test substrate does not touch the electrodes before the complete cleaning operation is performed. After cleaning, the water droplet angle of the slots on the second substrate corresponding to the second screening group is checked using a water droplet angle meter. A water droplet angle controlled within 10-30° is considered acceptable; 10-30° is a commonly used optimal adhesion window range in industry. Specifically, if necessary, monitoring of solder resist surface filler, transverse etching at the bottom of the holes, and whether the micro-pits on the solder resist surface meet specifications is also required.

[0030] In another embodiment, the method further includes a step of partitioning the experimental board, where twelve major areas sampled from the first test substrate are designated as thickness measurement areas, and thick and thin areas are distinguished based on the thickness measurement data. Subsequently, process distinctions are made based on the thick and thin areas, resulting in a more refined processing effect.

[0031] Specifically, the thin area was set to single-layer processing, with the laser power set to 2W, the number of shots set to 12, the aperture mask value set to 30µm, the galvanometer partition value adjusted to 15*15mm, and the galvanometer runout speed set to 5000mm / s. Additionally, a flat-top beam mode was used for the waveform.

[0032] Similarly, the thick area is set to be processed in two layers. The first layer is set with a laser power of 2W, a firing value of 10 shots, an aperture mask value of 30µm, a galvanometer partition value of 15*15mm, and a galvanometer runout speed of 5000mm / s. The second layer is set with a laser power of 1.5W, a firing value of 8 shots, an aperture mask value of 30µm, a galvanometer partition value of 15*15mm, and a galvanometer runout speed of 5000mm / s.

[0033] Based on the above solution, in another embodiment, during the initial operation phase, the machine's air blowing function is activated when working on thin areas, with the air blowing volume set to 20 m / s, and the air blowing function is deactivated when working on thick areas.

[0034] When the blowing function is activated, the gas is CDA (clean dry air). The side-mounted nozzle is at an adjustable angle of 30°-45° to the processing surface. It utilizes shear flow to enhance dust removal from the hole wall, improving dust removal efficiency by more than 11 times compared to vertical jet. At the same time, it dynamically adjusts the airflow according to the laser processing parameters, and uses forced airflow convection to quickly remove local heat inside the hole, inhibiting resin melting and adhesion and the expansion of the heat-affected zone. The blown dust is removed in real time by the dust extraction device. The dust extraction filter bag adopts a folded structure, which increases the filtration area by 30% in the same installation space, reduces airflow resistance, ensures stable dust extraction negative pressure, and forms efficient convection with the blowing system, further shortening the residence time of dust in the processing area and reducing the impact of secondary heat absorption on the hole.

[0035] The process described in the above embodiments effectively solves the industry pain point of uneven solder resist substrate thickness. It mainly addresses the issues of easy carbonization due to energy overload in thin areas and easy residue due to insufficient energy in thick areas by performing zoned processing, thus avoiding the aforementioned problems.

[0036] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention specification and drawings are included in the scope of the patent application of the present invention.

[0037] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0038] Although this application has been described by way of examples, those skilled in the art will know that this application has many modifications and variations without departing from the spirit of this application, and it is intended that the appended embodiments include these modifications and variations without departing from this application.

Claims

1. A method of laser slot hole processing of a thin solder mask substrate, characterized by, The laser slot hole processing method of the thin solder mask substrate comprises the following steps: Obtaining a preset slot hole size; Placing a first test substrate on a table and vacuumizing the processing area; Setting a preset laser power value, a number of values, a hole shape mask value on a laser machine, and setting a plurality of different galvanometer partition values and galvanometer jump speed values according to the preset slot hole size, wherein the absolute value of the difference of each galvanometer partition value is within a first preset range, and the absolute value of the difference of each galvanometer jump speed value is within a second preset range; Combining a plurality of different galvanometer partition values with a plurality of different galvanometer jump speed values to form a plurality of different first test groups; Based on the parameters of a plurality of first test groups, laser processing is performed on different positions of the first test substrate, and a plurality of slot holes are formed; After the first test substrate after multiple processing is taken out, appearance inspection is performed.

2. The method of laser slot hole processing of a thin solder mask substrate of claim 1, wherein: In the step of "taking out the first test substrate after multiple processing and performing appearance inspection", it is judged whether each slot hole has size deviation, copper dissolution at the bottom, and solder mask floating, and finally a group of first test groups without size deviation, copper dissolution at the bottom, and solder mask floating is selected as a first screening group, and the corresponding galvanometer partition value and galvanometer jump speed value are set for use in the batch production laser processing.

3. The method of claim 2, wherein: After the step of "judging whether each slot hole has size deviation, copper dissolution at the bottom, and solder mask floating, and finally selecting a group of first test groups without size deviation, copper dissolution at the bottom, and solder mask floating as a first screening group", laser processing is performed on a plurality of positions of the second test substrate based on the parameters of the screening group; Each slot hole of the second test substrate after laser processing is respectively and individually plasma cleaned; In the cleaning step, a plurality of different nitrogen values, oxygen values, carbon tetrafluoride values, argon values, cleaning power values, and plasma time values are set, wherein the absolute value of the difference of each nitrogen value is within a third preset range, the absolute value of the difference of each oxygen value is within a fourth preset range, the absolute value of the difference of each carbon tetrafluoride value is within a fifth preset range, the absolute value of the difference of each argon value is within a sixth preset range, the absolute value of the difference of each cleaning power value is within a seventh preset range, and the absolute value of the difference of each plasma time value is within an eighth preset range; Combining a plurality of different nitrogen values, oxygen values, carbon tetrafluoride values, argon values, cleaning power values, and plasma time values to form a plurality of different second test groups; Each second test group corresponds to a slot hole on the second test substrate, and each slot hole is respectively and individually plasma cleaned; after cleaning, appearance inspection is performed on the second test substrate.

4. The method of claim 3, wherein: In the step "appearance inspection of the second test substrate after the cleaning is completed", whether the via holes on the second substrate have solder mask, via bottom horizontal etching, and solder mask micro-pit hole is determined, and finally a group of the second test groups without solder mask, via bottom horizontal etching, and solder mask micro-pit hole is selected as the second screening group, and the corresponding nitrogen value, oxygen value, carbon tetrafluoride value, argon value, cleaning power value, and plasma time value are set for use in the batch production of the plasma cleaning.

5. The method of claim 2, wherein: The oscillating mirror partition value is set to 15*15 mm, and the oscillating mirror jumping speed value is set to 5000 mm / s.

6. The method of claim 4, wherein: The nitrogen value is set to 200 sccm, the oxygen value is set to 1600 sccm, the carbon tetrafluoride value is set to 80 sccm, the argon value is set to 200 sccm, the cleaning power value is set to 20 kw, and the plasma time value is set to 5 min.

7. The method of claim 1, wherein: In the step "setting the preset laser power value, number of shots, and hole shape mask value of the laser machine, and setting a plurality of different oscillating mirror partition values and oscillating mirror jumping speed values according to the preset via hole size", the twelve large areas of the first test substrate sample are set as thickness measurement areas, the thick areas and thin areas are distinguished according to the thickness measurement data, and different process parameter groups including the laser power value, number of shots, hole shape mask value, oscillating mirror partition value, and oscillating mirror jumping speed value are set for the thin areas and the thick areas.

8. The method of claim 4, wherein: In the step "determining whether the via holes on the second substrate have solder mask, via bottom horizontal etching, and solder mask micro-pit hole, and finally selecting a group of the second test groups without solder mask, via bottom horizontal etching, and solder mask micro-pit hole as the second screening group", the via holes on the second substrate corresponding to the second screening group are measured by a water drop angle measuring instrument to obtain the water drop angle number, and the via holes are qualified if the water drop angle is within 10-30°.

9. The method of claim 1, wherein: The laser machine is set to a green laser machine with a wavelength of 515 nm.

10. The method of claim 1, wherein: The waveform of the laser machine is set to flat-top light.

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