Cross-level laser drilling method using UV laser and carbon dioxide laser

Abstract

The invention discloses a cross-level laser drilling method utilizing UV laser and carbon dioxide laser, and belongs to the technical field of printed circuit boards. The cross-level laser drilling method utilizing the UV laser and the carbon dioxide laser burns through a required penetrating layer with a copper layer through high-energy UV laser drilling; the dielectric layer on the reserved layer bottom copper is burnt out and subjected to hole finishing by adopting carbon dioxide laser drilling, so that no adhesive residue is ensured under the condition that the hole bottom is not burnt through, the conduction connection performance of the printed circuit board is ensured, the processing quality stability of the printed circuit board is improved, and the production cost is reduced. And the problems of burning through and burning loss of a bottom copper layer caused by high energy of UV laser can be well improved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, and in particular to a cross-layer laser drilling method using UV laser and carbon dioxide laser. Background Art

[0002] As the technological revolution and industrial transformation are emerging, printed circuit boards, as basic components of electronic equipment, are developing towards dense arrangement, ultra-thin and ultra-small. Traditional mechanical drilling can no longer meet the complex connection methods of printed circuit boards. Laser drilling has become a new processing method to meet the complex circuits that have been developed so far.

[0003] UV laser drilling is a technology used in the process of printed circuit board processing. It mainly uses ultraviolet laser to accurately drill holes in PCB materials. The mechanism of UV laser drilling is mainly photochemical ablation. The photons of short-wavelength lasers have high energy and can destroy the long molecular chains of organic materials, turning them into particles and detaching them from the processing materials. Under the action of continuous external UV laser, the substrate material continues to escape to form micropores. In the process of UV laser direct cross-layer drilling, the UV light source has high energy and can directly burn through the copper layer between layers, but the difficult-to-control technical state will also cause the bottom copper layer to be burned through by the laser. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a cross-layer laser drilling method using UV laser and carbon dioxide laser, which can effectively avoid the phenomenon of burning through and burning the underlying copper layer.

[0005] The cross-layer laser drilling method using UV laser and carbon dioxide laser according to an embodiment of the present invention includes:

[0006] Step 1: Laminating the multilayer substrate material and the copper foil by heat and pressure to form a multilayer board;

[0007] Step 2: According to the required drilling positions, punch out the alignment holes for the laser drilling process on the plate;

[0008] Step 3: Use high-energy UV laser drilling to burn through the required penetration layer with the copper layer;

[0009] Step 4: Use carbon dioxide laser drilling to burn clean and complete the dielectric layer on the bottom copper of the retention layer;

[0010] Step 5: Deposit a layer of copper on the hole wall by electroplating to achieve electrical connection between the hole and the interlayer copper foil.

[0011] The cross-layer laser drilling method using UV laser and carbon dioxide laser according to the embodiment of the present invention has at least the following beneficial effects: the cross-layer laser drilling method using UV laser and carbon dioxide laser burns through the required penetration layer with the copper layer through high-energy UV laser drilling, and then uses carbon dioxide laser drilling to burn and fill the hole for the dielectric layer on the bottom copper of the retained layer, so that the bottom of the hole is guaranteed to have no residual glue without burning through, thereby ensuring the conductive connection performance of the printed circuit board, improving the quality stability of the printed circuit board processing, and can well improve the problem of high energy of UV laser burning through and burning the bottom copper layer.

[0012] According to some embodiments of the present invention, in step 1, the multiple layers of substrate materials are bonded by placing a prepreg between the multiple layers of substrate materials.

[0013] According to some embodiments of the present invention, the temperature, pressure and time of lamination are controlled so that the prepreg is completely cured and firmly bonded between the multi-layer substrate materials.

[0014] According to some embodiments of the present invention, before step 5, it is detected whether there is residual glue or burn-through at the bottom of the blind hole.

[0015] According to some embodiments of the present invention, an automatic optical inspection device is used to scan the bottom of the blind hole to identify whether there is residual glue or burn-through in the blind hole.

[0016] According to some embodiments of the present invention, the automatic optical inspection equipment identifies and marks defective products, and picks out the defective products for repair or elimination.

[0017] According to some embodiments of the present invention, in step 3, the path and energy of UV laser drilling are adjusted according to the thickness of the plate and the thickness of the copper layer.

[0018] According to some embodiments of the present invention, a real-time monitoring system is included in the UV laser drilling process to monitor the drilling depth and the copper layer burn-through condition so as to dynamically adjust the laser energy.

[0019] According to some embodiments of the present invention, in step 5, the hole wall is pretreated before electroplating, and the pretreatment includes chemical cleaning or mechanical grinding to remove the oxide layer or residue on the hole wall.

[0020] According to some embodiments of the present invention, in step 4, the hole wall is cooled after the carbon dioxide laser drilling to reduce the heat affected area.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 It is a flow chart of a cross-layer laser drilling method using UV laser and carbon dioxide laser according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0025] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0026] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0027] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0028] refer to Figure 1 A cross-layer laser drilling method using a UV laser and a carbon dioxide laser according to an embodiment of the present invention is described.

[0029] like Figure 1 As shown, the cross-layer laser drilling method using UV laser and carbon dioxide laser according to an embodiment of the present invention includes:

[0030] Step 1: Laminating the multilayer substrate material and the copper foil by heat and pressure to form a multilayer board;

[0031] Step 2: According to the required drilling positions, punch out the alignment holes for the laser drilling process on the plate;

[0032] Step 3: Use high-energy UV laser drilling to burn through the required penetration layer with the copper layer;

[0033] Step 4: Use carbon dioxide laser drilling to burn clean and complete the dielectric layer on the bottom copper of the retention layer;

[0034] Step 5: Deposit a layer of copper on the hole wall by electroplating to achieve electrical connection between the hole and the interlayer copper foil.

[0035] like Figure 1 As shown, the multi-layer substrate material is first laminated, and the different circuit layers are bonded together through the prepreg to form a multi-layer board structure. During the lamination process, the temperature, pressure and time need to be precisely controlled to ensure that the prepreg is fully cured and the layers are firmly bonded. After lamination, the preliminary structure of the multi-layer board is obtained, which is ready for the subsequent drilling process.

[0036] Punching target holes on the laminated sheets is a key step to provide accurate alignment for the laser drilling process. In this step, mechanical punching or precision molds are used to punch small holes at designated locations on the PCB. These small holes will serve as alignment marks for laser drilling. The accuracy of the punching target holes directly affects the accuracy of subsequent laser drilling, so the positioning and dimensional accuracy during the punching process need to be strictly controlled.

[0037] After the target holes are punched, the next step is UV laser drilling. UV laser drilling uses a high-energy ultraviolet laser beam to penetrate the PCB layers and burn through the copper layer. Because the UV laser has high energy and a short wavelength, it can accurately remove material while reducing the thermal impact on the surrounding materials. In this step, the UV laser moves along a predetermined path to burn through the required layer while avoiding damage to the underlying copper layer.

[0038] After the UV laser drilling is completed, the next step is to use a carbon dioxide laser to burn out and fill the hole with the dielectric layer on the bottom copper of the retention layer. Carbon dioxide laser drilling uses the thermal effect of infrared lasers to heat treat the hole wall and remove the residual dielectric material on the hole wall to ensure that the hole wall is smooth and free of residual glue. This step is crucial to ensure the quality of the hole and the reliability of the PCB.

[0039] After drilling is completed, the bottom of the blind hole is scanned with automatic optical inspection equipment to check for residual glue, burn-through or other defects. AOI equipment can automatically identify and mark defective products for subsequent repair or elimination.

[0040] Copper plating is the process of metallizing blind holes. A layer of copper is deposited on the hole wall by electroplating to achieve electrical connection between the hole and the interlayer copper foil. This step is crucial to ensure the conductivity of the PCB. After copper plating is completed, the blind hole is filled and leveled, ready for subsequent electroplating and pattern transfer processes.

[0041] Therefore, in this cross-layer laser drilling method using UV laser and carbon dioxide laser, high-energy UV laser drilling is used to burn through the required penetration layer with the copper layer, and then carbon dioxide laser drilling is used to burn and fill the hole on the dielectric layer on the bottom copper of the retained layer, so that there is no residual glue at the bottom of the hole without burning through, thereby ensuring the conductive connection performance of the printed circuit board, improving the quality stability of the printed circuit board processing, and can well improve the problem of high energy of UV laser burning through and burning the bottom copper layer.

[0042] In step 1, the multi-layer substrate materials are bonded by placing a prepreg between the multi-layer substrate materials. The temperature, pressure and time of the lamination are controlled so that the prepreg is completely cured and firmly bonded between the multi-layer substrate materials.

[0043] Before step 5, check whether there is residual glue or burn-through at the bottom of the blind hole. Use automatic optical inspection equipment to scan the bottom of the blind hole to identify whether there is residual glue or burn-through in the blind hole. The automatic optical inspection equipment identifies and marks defective products, and picks out the defective products for repair or elimination.

[0044] In step 3, the path and energy of UV laser drilling are adjusted according to the thickness of the plate and the thickness of the copper layer. The UV laser drilling process includes a real-time monitoring system to monitor the drilling depth and the copper layer burn-through to dynamically adjust the laser energy.

[0045] In step 5, the hole wall is pretreated before electroplating to improve the bonding strength between the copper layer and the hole wall. The pretreatment includes chemical cleaning or mechanical grinding to remove the oxide layer or residue on the hole wall.

[0046] In step 4, the hole wall is cooled after the CO2 laser drilling to reduce the heat affected area. The cooling process is achieved by spraying coolant or using cooling gas.

[0047] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A cross-layer laser drilling method using UV laser and carbon dioxide laser, characterized in that: include: Step 1: Laminating the multilayer substrate material and the copper foil by heat and pressure to form a multilayer board; Step 2: According to the required drilling positions, punch out the alignment holes for the laser drilling process on the plate; Step 3: Use high-energy UV laser drilling to burn through the required penetration layer with the copper layer; Step 4: Use carbon dioxide laser drilling to burn clean and complete the dielectric layer on the bottom copper of the retention layer; Step 5: Deposit a layer of copper on the hole wall by electroplating to achieve electrical connection between the hole and the interlayer copper foil.

2. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 1, characterized in that: In step 1, multiple layers of substrate materials are bonded by placing a prepreg between the multiple layers of substrate materials.

3. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 2, characterized in that: The temperature, pressure and time of lamination are controlled to fully cure the prepreg and firmly bond between the multi-layer substrate materials.

4. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 1, characterized in that: Before step 5, check whether there is residual glue or burn-through at the bottom of the blind hole.

5. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 4, characterized in that: Automatic optical inspection equipment is used to scan the bottom of the blind hole to identify whether there is residual glue or burn-through in the blind hole.

6. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 5, characterized in that: Automated optical inspection equipment identifies and marks defective products, and selects them for repair or elimination.

7. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 1, characterized in that: In step 3, the path and energy of the UV laser drilling are adjusted according to the thickness of the board and the thickness of the copper layer.

8. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 7, characterized in that: The UV laser drilling process includes a real-time monitoring system to monitor the drilling depth and copper layer burn-through to dynamically adjust the laser energy.

9. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 1, characterized in that: In step 5, the hole wall is pretreated before electroplating. The pretreatment includes chemical cleaning or mechanical grinding to remove the oxide layer or residue on the hole wall.

10. The cross-layer laser drilling method using UV laser and carbon dioxide laser according to claim 7, characterized in that: In step 4, the hole wall is cooled after CO2 laser drilling to reduce the heat affected zone.

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