Method for laser processing of titanium-copper blind hole

Abstract

The invention discloses a titanium-copper blind hole laser processing method, which comprises the following steps of: 1, selecting a proper titanium-copper plate as a substrate, and fixing the titanium-copper plate on a workbench of a laser punching machine; 2, a short-pulse and high-repetition-frequency pulse laser or optical fiber laser system is adopted, and the focus point of a laser head is adjusted to the surface of the substrate; thirdly, MARK points are grabbed for alignment, it is ensured that the focus point of laser is consistent with the position of the pre-punched blind hole, and the hole is deepened step by step in a multi-time laser scanning mode till machining of the blind hole is completed; 4, filling copper into the processed blind hole by using an electroplating process to form a conductive channel; and fifthly, the electroplated blind hole is polished and cleaned. According to the method for laser processing of the titanium-copper blind hole, the one-time forming blind hole processing method is optimized, the processing flow is reduced, the cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of blind hole processing, and in particular to a method for laser titanium copper blind hole processing. Background Art

[0002] Laser titanium copper blind hole process is an advanced microelectronic packaging technology, mainly used to realize the blind hole production in high-density interconnected printed circuit boards. The existing blind hole processing technology is to process the blind hole by image transfer etching and then laser one-time forming. However, the conventional laser processing method has a long process and high cost. In addition, when processing titanium copper blind holes, since the thickness of the titanium copper layer is about 30um, the conventional laser processing method is inefficient and easy to break through the pad copper, resulting in functional abnormalities. Summary of the invention

[0003] In order to overcome the above shortcomings, the purpose of the present invention is to provide a method for laser titanium copper blind hole, which reduces the processing flow, reduces the cost and improves the production efficiency.

[0004] Technical solution: The present invention discloses a method for laser blind vias in titanium copper, comprising the following steps:

[0005] Step 1: Select a suitable titanium copper plate as the substrate and fix it on the workbench of the laser punching machine;

[0006] Step 2: Using a short-pulse, high-repetition-rate pulse laser or fiber laser system, adjust the focus of the laser head to the surface of the substrate;

[0007] Step 3: Grab the MARK point and align it to ensure that the focus of the laser is consistent with the position of the pre-drilled blind hole. Use multiple laser scans to gradually deepen the hole until the blind hole processing is completed;

[0008] Step 4: Use electroplating to fill copper into the processed blind holes to form a conductive channel;

[0009] Step 5: Grind and clean the blind holes after electroplating.

[0010] Furthermore, in step one, the substrate is also pre-treated to clean the titanium coating of the substrate to remove oil and dust.

[0011] Furthermore, in step one, the substrate is fixed on a workbench using a vacuum suction cup or a mechanical clamp.

[0012] Furthermore, in step three, when the blind hole is processed by multiple laser scans, auxiliary gas is also used to reduce oxidation of the substrate and cool the substrate to reduce thermal effects.

[0013] Furthermore, in the process of machining the blind hole, GCAL precision correction and SCAL precision correction are also included. The automatic correction frequency of the GCAL precision correction is 24 hours / time, and the automatic correction frequency of the SCAL precision correction is 30 minutes / time.

[0014] Furthermore, in step three, the blind hole position is located using mapping software and converted into a processing program recognizable by the laser punching machine to align the focus of the laser with the blind hole.

[0015] Furthermore, in step 2, the power of the pulse laser is 11W, the frequency range is 40KHZ-90KHZ, and the light path spot is 15um.

[0016] The beneficial effects of the present invention are:

[0017] (1) The use of a short-pulse, high-repetition-frequency laser processing system can avoid the breakdown of the copper pad during one-time processing of blind holes, and can better control the heat-affected area around the blind holes, prevent material deformation, and reduce material splashing and thermal damage;

[0018] (2) During the processing, auxiliary gas is used to help reduce oxidation and improve the processing quality of blind holes;

[0019] (3) Using multiple laser scans to gradually deepen the hole can accurately control the depth and shape of the blind hole and reduce thermal effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only for illustration purposes and are used to help understand the present invention. They do not specifically limit the shapes and proportional dimensions of the components of the present invention. Under the guidance of the present invention, those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to specific circumstances. In the drawings:

[0021] Figure 1 This is a flow chart of the laser titanium copper blind hole method of the present invention;

[0022] Figure 2 It is a schematic diagram of blind hole processing of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0024] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The following describes an implementation method of the present invention based on its overall structure.

[0025] like Figure 1 and 2 As shown, the present invention discloses a method for laser titanium copper blind hole, comprising the following steps:

[0026] Step 1: Select a suitable titanium copper plate as the substrate and fix it on the workbench of the laser punching machine;

[0027] Step 2: Using a short-pulse, high-repetition-rate pulse laser or fiber laser system, adjust the focus of the laser head to the surface of the substrate;

[0028] Step 3: Grab the MARK point and align it to ensure that the focus of the laser is consistent with the position of the pre-drilled blind hole. Use multiple laser scans to gradually deepen the hole until the blind hole processing is completed;

[0029] Step 4: Use electroplating to fill copper into the processed blind holes to form a conductive channel;

[0030] Step 5: Grind and clean the blind holes after electroplating.

[0031] According to the above steps, if Figure 1 and Figure 2As shown, technicians in this field select high-purity, corrosion-resistant titanium copper plates as substrates to ensure that they have good mechanical properties and conductivity, and fix the side with the titanium-gold coating upward on the workbench of the laser punching machine to ensure its stability. In addition, laser equipment preferably uses pulsed lasers or fiber laser systems with short pulses and high repetition rates. This laser system has excellent focusing performance and is suitable for micro-machining. Before processing the blind hole, ensure that the surface of the substrate is flat and free of impurities again, and then adjust the focus of the laser head to ensure that it is perpendicular to the surface of the substrate, and place the focus on the surface of the substrate or slightly below the surface to achieve the best processing effect. Mark multiple reference MARK points on the substrate, and monitor them in real time through the camera system to ensure the consistency of the laser focus point with the preset blind hole position. Due to the high hardness and strong thermal conductivity of titanium copper materials, the laser energy may be quickly dispersed and it is not easy to concentrate on one point to form a high-quality blind hole. In addition, the high temperature generated during the laser processing may cause material deformation or melt sputtering, which is particularly unfavorable for high-precision blind hole processing. Therefore, during the blind hole processing, multiple scanning techniques are used to gradually deepen the holes. Technicians can set the processing depth and speed to avoid material damage caused by overheating. After the blind hole processing is completed, pre-electroplating treatment is carried out to ensure that the inner surface of the hole is smooth and conducive to the adhesion of copper. DC electroplating can be used to electroplate in a specific electrolyte to ensure that the copper layer is uniform and has strong adhesion to form a good conductive channel. After the electroplating is completed, the blind hole is polished with a grinder to remove the excess copper layer to ensure the accuracy and conductivity of the blind hole. Finally, it is cleaned and dried to ensure that the product meets the technical requirements and usage standards.

[0032] Specifically, in step 2, the power of the pulsed laser is 11W, the frequency range is 40KHZ-90KHZ, and the optical path spot is 15um. The power of 11W and the frequency range of 40kHz-90kHz can achieve faster drilling speed, reduce processing time, and improve overall efficiency. The 15um spot diameter enables the laser to more accurately control the aperture during the processing process to ensure that the size and shape of the blind hole meet the design requirements. Shorter pulses and high frequencies can effectively reduce heat input and reduce the heat-affected zone of the material around the substrate, thereby reducing deformation and oxidation and improving the quality of the blind hole. Precise laser processing can reduce burrs and surface roughness, thereby improving the surface quality after electroplating and enhancing the performance of the conductive channel.

[0033] In this embodiment, step 1 also includes pretreatment of the substrate, cleaning the titanium coating on the surface of the substrate, and using ultrasonic cleaning to remove oil, dust and other contaminants. After the pretreatment, a vacuum suction cup or a mechanical clamp is used to firmly fix the substrate on the workbench of the laser punching machine. Among them, the vacuum suction cup is suitable for a flat surface, while the mechanical clamp is suitable for a substrate with a complex shape. The fixing device can ensure that the substrate will not be displaced during the processing, thereby ensuring the accuracy of the blind hole position.

[0034] In this embodiment, in step three, multiple laser scans are used to deepen the holes. During this process, the use of auxiliary gas (such as nitrogen) can effectively reduce the oxidation reaction on the surface of the substrate and help cool the substrate to reduce thermal deformation caused by thermal effects. The flow rate and pressure of the auxiliary gas can be adjusted according to the specific processing conditions to achieve the best effect.

[0035] The present invention also includes precision calibration. In the process of processing blind holes, GCAL and SCAL precision calibration are important links to ensure processing accuracy. GCAL stands for "Gain Calibration", which is mainly used to calibrate the amplification factor of the laser machine signal. In the process of receiving and processing signals by the laser machine, it is necessary to amplify the weak signal to a suitable degree for measurement and processing. GCAL is to ensure the accuracy of the amplification process. For example, when the laser machine is used to detect weak reflected light signals, the signal can be accurately amplified through gain calibration, so that the subsequent system can correctly identify and process it. SCAL stands for "Scale Calibration", which focuses on calibrating the proportional relationship between the measured value of the laser machine and the actual physical quantity, ensuring that the measurement result displayed by the laser machine is accurately corresponding to the real physical quantity. For example, when the laser machine is used to measure distance, the scale calibration must ensure that the displayed distance value is strictly corresponding to the actual distance. GCAL focuses on whether the amplification factor of the signal is correct, which is a calibration of the signal processing link; while SCAL focuses on whether the ratio between the measurement result and the actual physical quantity is accurate, which is a calibration of the entire measurement accuracy. The automatic calibration frequency of GCAL precision calibration is set to once every 24 hours, while SCAL precision calibration is set to once every 30 minutes. These two calibrations are monitored in real time by high-precision sensors, and the processing parameters of the equipment are adjusted in time to ensure the stability and consistency of each processing.

[0036] Before processing the blind hole, it is necessary to use drawing software (such as CAD software) to accurately locate the position of the blind hole and convert the design drawing into a processing program that can be recognized by the laser punching machine. By importing the program, ensure that the focus point of the laser is aligned with the position of the blind hole to avoid deviation.

[0037] Preferably, in step 4, after the blind hole processing is completed, the hole needs to be electroplated. The electroplating process needs to maintain a constant current density to ensure uniform deposition of the copper layer. After the electroplating is completed, polishing and cleaning are performed to remove excess copper layer and impurities on the surface to ensure that the product meets the conductivity and appearance requirements.

[0038] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for laser blind vias in titanium copper, characterized in that: The following steps are involved: Step 1: Select a suitable titanium copper plate as the substrate and fix it on the workbench of the laser punching machine; Step 2: Using a short-pulse, high-repetition-rate pulse laser or fiber laser system, adjust the focus of the laser head to the surface of the substrate; Step 3: Grab the MARK point and align it to ensure that the focus of the laser is consistent with the position of the pre-drilled blind hole. Use multiple laser scans to gradually deepen the hole until the blind hole processing is completed; Step 4: Use electroplating to fill copper into the processed blind holes to form a conductive channel; Step 5: Grind and clean the blind holes after electroplating.

2. The method for laser titanium copper blind via according to claim 1, characterized in that: In step one, the substrate is also pre-treated to clean the titanium cover layer of the substrate to remove oil and dust.

3. The method for laser titanium copper blind via according to claim 1, characterized in that: In step one, the substrate is fixed on a workbench using a vacuum chuck or a mechanical clamp.

4. The method for laser titanium copper blind via according to claim 1, characterized in that: In step three, when the blind hole is processed by multiple laser scans, auxiliary gas is also used to reduce substrate oxidation and cool the substrate to reduce thermal effects.

5. The method for laser titanium copper blind via according to claim 1, characterized in that: The process of machining blind holes also includes GCAL precision correction and SCAL precision correction. The automatic correction frequency of the GCAL precision correction is 24 hours / time, and the automatic correction frequency of the SCAL precision correction is 30 minutes / time.

6. The method for laser titanium copper blind via according to claim 1, characterized in that: In step three, the blind hole position is located using mapping software and converted into a processing program that can be recognized by the laser punching machine to align the laser focus point with the blind hole.

7. The method for laser titanium copper blind via according to claim 1, characterized in that: In step 2, the power of the pulse laser is 11W, the frequency range is 40KHZ-90KHZ, and the light path spot is 15um.

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