Micro blind hole laser alignment method and system

Abstract

The present invention discloses a method and system for laser alignment of micro blind holes, the method comprising the following steps: removing the surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target of the printed circuit board by a laser machine, and the alignment target is covered with a second resin medium layer of the second set thickness; according to the second resin medium layer, the alignment target position is captured by an exposure machine and a blind hole opening image is produced; according to the blind hole opening image, the second resin medium layer is ablated by a laser machine to obtain a blind hole consistent with the blind hole opening image. The present invention achieves accurate positioning of the blind hole by aligning according to the alignment target position when producing the blind hole opening image; at the same time, after the blind hole is developed, it only needs to be ablated on the second resin medium layer by small energy to form a hole, which will not make the blind hole diameter too large, thereby ensuring the quality of the blind hole.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, and in particular to a micro blind hole laser alignment method and system. Background Art

[0002] With the development trend of electronic products towards small size and high performance, the blind holes of PCB printed circuit boards are designed to be smaller and smaller. When the blind holes are very small, it is very difficult to achieve both good hole quality and high hole position accuracy. The same problem also occurs in SiP and heterogeneous integration.

[0003] Conventional LDD laser direct hole forming method, although the blind hole produced has high position accuracy, the quality is very poor; this is mainly because although the LDD process first ablates the surface copper and dielectric layer on the alignment target during laser, identifies the alignment pad on the lower pattern, and achieves the alignment consistency of the laser and the lower pattern, that is, the laser and the lower pattern are the same alignment system; but the laser machine uses a high-energy large spot to ablate the 3-6um surface copper, and then uses low energy to ablate the resin dielectric layer below it to form a blind hole. The high heat thermal ablation effect when ablating the surface copper also affects the resin dielectric layer under the surface copper around the blind hole opening, and a relatively large gap or excessive resin damage is generated between the surface copper and the resin dielectric layer around the blind hole opening. On the one hand, even if the surface copper blind hole opening size meets the requirements, the actual size of the resin hole wall at the blind hole opening actually exceeds the specification requirements; on the other hand, the excessive gap between the base copper and the resin around the blind hole opening affects the reliability of copper plating and blind holes. Therefore, although the LDD hole-forming process can achieve precise alignment between the laser and the underlying pattern, the high-heat laser makes it difficult to obtain the required blind hole size and good blind hole quality, resulting in the blind hole size not meeting the requirements or the blind hole quality being poor.

[0004] Another blind hole alignment method is to use the CFM (mask-forming hole) process. The blind hole opening pattern is first produced by an exposure machine, and then the surface copper at the blind hole opening is etched away. Although the surface copper does not need to be ablated during laser irradiation, the resin can be directly ablated with low energy to form a micro blind hole with better quality. However, when producing the blind hole opening pattern, the exposure machine cannot grasp the alignment target Pad of the lower layer through the surface copper, and can only use the through hole on the PCB board for alignment (another alignment system). In this way, the blind hole opening pattern cannot be accurately aligned with the lower layer pattern, resulting in the inability to achieve accurate positioning of the micro blind hole. Summary of the invention

[0005] In view of the above technical problems, the purpose of the present invention is to provide a micro blind hole laser alignment method and system to solve the problem that the blind hole size produced by the traditional blind hole alignment method does not meet the requirements, or the blind hole quality is poor, or it cannot be accurately positioned.

[0006] The present invention adopts the following technical solutions:

[0007] A micro blind hole laser alignment method comprises the following steps:

[0008] The surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target of the printed circuit board are removed by a laser machine, and the alignment target is covered with a second resin medium layer of the second set thickness;

[0009] According to the second resin medium layer, an exposure machine is used to capture the alignment target position and produce a blind hole opening image;

[0010] According to the blind hole opening image, the second resin medium layer is ablated by a laser machine to obtain a blind hole consistent with the blind hole opening image.

[0011] Optionally, when the second resin medium layer is ablated by a laser machine, the laser energy emitted by the laser machine does not ablate the surface copper around the second resin medium layer.

[0012] Optionally, the laser machine is an ultraviolet laser machine, and the laser wavelength emitted by the laser machine is 355nm.

[0013] Optionally, the diameter of the blind hole is less than 50 um.

[0014] Optionally, based on the second resin medium layer, the alignment target position is captured by an exposure machine and a blind hole opening image is produced, including: aligning the alignment target through the second resin medium layer, attaching a dry film at the alignment target position, and developing a blind hole opening image.

[0015] Optionally, after the step of developing the blind hole opening image, the step further includes: cleaning and drying the dry film residue at the blind hole.

[0016] A micro blind hole laser alignment system, comprising a laser machine and an exposure machine;

[0017] The laser machine is used to remove the surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target of the printed circuit board, and the alignment target is covered with a second resin medium layer of the second set thickness;

[0018] The exposure machine is used to capture the alignment target position and produce a blind hole opening image according to the second resin medium layer; and ablate the second resin medium layer according to the blind hole opening image to obtain a blind hole consistent with the blind hole opening image.

[0019] Optionally, when the laser energy emitted by the laser machine ablates the second resin medium layer, it does not ablate the surface copper around the second resin medium layer.

[0020] Optionally, the laser machine is an ultraviolet laser machine, and the laser wavelength emitted by the laser machine is 355nm.

[0021] Optionally, the diameter of the blind hole is less than 50 um.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The micro blind hole laser alignment method of the present invention uses a laser machine to remove the surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target of the printed circuit board, and the alignment target is covered with a second resin medium layer of the second set thickness; according to the second resin medium layer, the alignment target position is captured by an exposure machine and a blind hole opening image is produced; according to the blind hole opening image, the second resin medium layer is ablated by a laser machine to obtain a blind hole consistent with the blind hole opening image; when producing the blind hole opening image, alignment is performed according to the alignment target position to produce the blind hole opening image, thereby achieving accurate positioning of the blind hole; at the same time, after the blind hole is developed, it is only necessary to form a hole by low-energy ablation on the second resin medium layer. Since the low-energy ablation will not ablate the copper surface around the alignment target, the blind hole aperture will not be enlarged, the size requirements of the blind hole aperture can be met, and the blind hole quality is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a process flow of a micro blind hole laser alignment method provided by an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a printed circuit board used in a micro blind hole laser alignment method provided in an embodiment of the present invention, wherein: 1. Alignment target. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form a new embodiment:

[0027] Embodiment 1:

[0028] The professional name of the present invention is explained below:

[0029] Blind via: A through hole that connects the surface layer and the inner layer, and does not penetrate the entire board.

[0030] Microvia: In printed circuit boards, holes with a diameter less than 6 mm (150 microns) are called microvias.

[0031] Exposure machine: refers to a machine that transfers the image information on film or other transparent objects to the surface coated with photosensitive material by turning on the light to emit UVA wavelength ultraviolet rays.

[0032] Laser machines use laser beams to etch or permanently mark the surfaces of various materials. The specific principle is to expose the deeper materials through the evaporation of the surface materials, thereby carving holes or patterns.

[0033] Please refer to Figure 1 and 2 As shown, Figure 1 A micro blind hole laser alignment method of the present invention is shown. Figure 2 A schematic diagram of a printed circuit board used in a micro blind hole laser alignment method provided by an embodiment of the present invention is shown. The micro blind hole laser alignment method comprises the following steps:

[0034] Step S1: removing the surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target 1 of the printed circuit board by a laser machine, and the alignment target 1 is covered with a second resin medium layer of the second set thickness;

[0035] In this embodiment, the laser machine is an ultraviolet laser machine, and the laser wavelength emitted by the laser machine is 355nm.

[0036] In the above implementation process, an ultraviolet laser machine is used to remove the surface copper on the inner layer alignment target 1 of the board making and the first resin medium layer of the first set thickness. Before removing the surface copper on the inner layer alignment target 1 of the board making and the first resin medium layer of the first set thickness, the printed circuit board surface does not need to be laser pre-treated (browning), and the surface copper layer can be directly ablated.

[0037] Step S2: According to the second resin medium layer, the position of the alignment target 1 is captured by an exposure machine and a blind hole opening image is produced;

[0038] Optionally, based on the second resin medium layer, the position of the alignment target 1 is captured by an exposure machine and a blind hole opening image is produced, including: aligning the alignment target 1 through the second resin medium layer, attaching a dry film at the position of the alignment target 1, and developing a blind hole opening image.

[0039] Optionally, after the step of developing the blind hole opening image, the step further includes: cleaning and drying the dry film residue at the blind hole.

[0040] Step S3: According to the blind hole opening image, a second resin medium layer is ablated by a laser machine to obtain a blind hole consistent with the blind hole opening image.

[0041] In this embodiment, when the second resin medium layer is ablated by a laser machine, the laser energy emitted by the laser machine does not ablate the surface copper around the second resin medium layer.

[0042] In this embodiment, the diameter of the blind hole is less than 50 um.

[0043] In the existing technology, there are bottlenecks in the production of micro blind holes below 50um, which are mainly reflected in the position accuracy of the sub-blind holes and the quality of the blind holes. Through the LDD (laser direct hole forming process) laser direct ablation of the copper surface, the blind hole diameter is too large and the quality of the blind hole is too poor, which does not meet the requirements of the micro blind hole process; through the CFM hole forming process (mask hole forming process), the blind hole is easy to deviate and the alignment accuracy is too poor.

[0044] In this embodiment, the present invention first removes the surface copper and a certain thickness of the resin dielectric layer at the position of the board surface alignment target 1, and retains a certain thickness of the dielectric layer, through which the lower layer alignment target 1 can be seen; in the CFM mask production process, the LDI exposure machine grabs the lower layer alignment target 1Pad through the remaining dielectric layer for alignment, and produces a micro blind hole opening pattern, so as to accurately locate the position of the micro blind hole and the size of the micro blind hole opening; then in the laser process, the laser machine still grabs the lower layer alignment target 1Pad for alignment, and ablates the resin dielectric layer at the micro blind hole opening position, so as to achieve accurate positioning and high-quality hole formation of the micro blind hole.

[0045] The following is a detailed comparison of the traditional process flow and the process flow of the method of the present invention, as shown in the following table:

[0046] 1) Traditional process flow: LDD (laser direct hole forming process) alignment description is shown in Table 1:

[0047]

[0048] Table 1: LDD (Laser Direct Drilling) Alignment Description

[0049] Among them, the advantage of the LDD (laser direct drilling process) alignment method is that the laser directly refers to the underlying pattern for alignment, and the blind hole position has high accuracy. The disadvantage is that the laser directly ablates the copper surface, the blind hole diameter is relatively large, and the blind hole quality is too poor, which does not meet the requirements of the micro blind hole process.

[0050] 2) Traditional process flow: CFM hole forming (mask hole forming process) alignment description is shown in Table 2:

[0051]

[0052] Table 2: CFM hole forming (mask hole forming process) alignment description

[0053] Among them, the advantage of the CFM hole forming (mask hole forming process) alignment method is that the surface copper at the blind hole opening is removed in advance, and then the laser machine can use small energy to drill holes on the resin medium layer. The quality of the blind hole is better, but the disadvantage is obvious. The blind hole is easy to deviate and the alignment accuracy is too poor.

[0054] 3) The laser alignment method of the present invention uses a UV laser machine to cut off the surface copper on the alignment pad, and then make a blind hole opening pattern. The alignment description is shown in Table 3:

[0055]

[0056] Table 3: Laser alignment description of the present invention

[0057] From the process flow point of view, the invention has a simple additional process, which only processes the lower layer alignment pad, takes a short time, and has a small cost increase. Compared with the realization of the micro blind hole process, the increased processing time and cost are negligible. Moreover, the alignment method of the invention combines the advantages of LDD hole forming and CFM hole forming processes, avoids the shortcomings of the two processes through the new alignment method, and satisfies the micro blind hole position accuracy and blind hole quality very well.

[0058] In the above implementation process, the micro blind hole laser alignment method of the present invention, when making a blind hole opening image, adopts alignment according to the position of the alignment target 1 to produce a blind hole opening image, thereby achieving precise positioning of the blind hole; at the same time, after the blind hole is developed, it is only necessary to form a hole on the second resin medium layer through low-energy ablation. Since low-energy ablation will not ablate the copper surface around the alignment target 1, the blind hole aperture will not be enlarged, thereby ensuring the quality of the blind hole.

[0059] Embodiment 2:

[0060] A micro blind hole laser alignment system of the present invention comprises a laser machine and an exposure machine;

[0061] The laser machine is used to remove the surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target 1 of the printed circuit board, and the alignment target 1 is covered with a second resin medium layer of the second set thickness;

[0062] The exposure machine is used to capture the position of the alignment target 1 and produce a blind hole opening image according to the second resin medium layer; and ablate the second resin medium layer according to the blind hole opening image to obtain a blind hole consistent with the blind hole opening image.

[0063] Optionally, when the laser energy emitted by the laser machine ablates the second resin medium layer, it does not ablate the surface copper around the second resin medium layer.

[0064] Optionally, the laser machine is an ultraviolet laser machine, and the laser wavelength emitted by the laser machine is 355nm.

[0065] Optionally, the diameter of the blind hole is less than 50 um.

[0066] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for laser alignment of micro blind holes, characterized in that: The diameter of the blind hole is less than 50um, and the method comprises the following steps: The surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target of the printed circuit board are removed by a laser machine, and the alignment target is covered with a second resin medium layer of the second set thickness; According to the second resin medium layer, an exposure machine is used to capture the alignment target position and produce a blind hole opening image; According to the blind hole opening image, a second resin medium layer is ablated by a laser machine to obtain a blind hole consistent with the blind hole opening image; when the second resin medium layer is ablated by the laser machine, the laser energy emitted by the laser machine does not ablate the surface copper around the second resin medium layer; according to the second resin medium layer, the alignment target position is captured by an exposure machine and a blind hole opening image is produced, including: through the second resin medium layer, aligning the alignment target, attaching a dry film at the alignment target position, and developing the blind hole opening image.

2. The method for laser alignment of micro blind holes according to claim 1, characterized in that: The laser machine is an ultraviolet laser machine, and the laser wavelength emitted by the laser machine is 355nm.

3. The method for laser alignment of micro blind holes according to claim 1, characterized in that: After the step of developing the blind hole opening image, the method further includes: cleaning and drying the dry film residue at the blind hole.

4. A micro blind hole laser alignment system, characterized in that: Including laser machine and exposure machine; The laser machine is used to remove the surface copper and the first resin medium layer of the first set thickness on the inner layer alignment target of the printed circuit board, and the alignment target is covered with a second resin medium layer of the second set thickness; The exposure machine is used to capture the alignment target position and produce a blind hole opening image according to the second resin medium layer; and according to the blind hole opening image, ablate the second resin medium layer by a laser machine to obtain a blind hole consistent with the blind hole opening image; the laser energy emitted by the laser machine does not ablate the surface copper around the second resin medium layer when ablating the second resin medium layer.

5. The micro blind hole laser alignment system according to claim 4, characterized in that: The laser machine is an ultraviolet laser machine, and the laser wavelength emitted by the laser machine is 355nm.

6. The micro blind hole laser alignment system according to claim 4, characterized in that: The diameter of the blind hole is less than 50 um.

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