A high-reliability hole copper control method for an automobile circuit board

Abstract

The application discloses a high-reliability hole copper control method for an automobile circuit board. The hole diameter and the thickness-diameter ratio are used to adjust the drilling parameters, and the hole wall roughness is improved by optimizing the drilling process, so that the copper thickness of the hole wall after copper plating meets the production requirements. In the application, the hole wall roughness after optimizing the drilling process is less than or equal to 25 um, and the copper thickness of the hole wall after electroplating is greater than or equal to 25 um.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, specifically to a method for controlling high-reliability via copper in automotive circuit boards. Background Technology

[0002] Currently, there are three major technical bottlenecks in the copper hole process for automotive circuit boards: 1. Poor adaptability to thickness-to-diameter ratio: In traditional processes, the uniformity of copper in the holes drops sharply (range > 8μm) when the thickness-to-diameter ratio is > 10:1. 2. Unstable borehole wall quality: Conventional drilling parameters cause Ra fluctuations (20-35μm); 3. Insufficient process compatibility: It is difficult to cover the 0.3-4.6mm aperture range with the same parameters.

[0003] According to a certain automotive manufacturer's standard, the thinnest point thickness of the copper in the via should be ≥25µm, and the wall roughness Ra should be ≤25µm. However, actual product measurements show that the thinnest point thickness of the copper in the via is 18-22µm, and the wall roughness Ra is 28-35µm, both of which do not meet the standard requirements. The pass rate for circuit boards with a thickness-to-diameter ratio of 15:1 is approximately 67%, indicating a low product pass rate.

[0004] Therefore, it is necessary to provide a new process to improve the reliability of through-hole copper. Summary of the Invention

[0005] The purpose of this invention is to provide a high-reliability hole copper control method for automotive circuit boards, which improves hole wall roughness by optimizing the drilling process, so that the copper thickness of the hole wall after copper plating meets production requirements.

[0006] The technical solution of the present invention is as follows: A method for controlling high-reliability via copper in automotive circuit boards, characterized by comprising the following steps: Drilling parameters are adjusted according to the hole diameter and thickness-to-diameter ratio, as follows: When the finished hole diameter is 0.3-0.5mm, use a drill bit with a diameter of 0.25-0.45mm: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n1 = 140k r / min (140,000r / min), and the feed rate F1 = 2.0mm / min; if the thickness-to-diameter ratio is >8:1, the drill bit speed is 0.9*n1, and the feed rate is 0.8*F1. When the hole diameter is 0.9-1.3mm, use a drill bit with a diameter of 0.85-1.25mm: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n2=55k r / min and the feed rate F2=2.8mm / min; if the thickness-to-diameter ratio is >8:1, drill according to the parameters for a thickness-to-diameter ratio ≤8:1 and then perform helical milling. When the finished hole diameter is 1.4-1.8mm, use a drill bit with a diameter of 1.35-1.75mm and adopt a layered cutting method for drilling: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n3=35k r / min and the feed rate F3=2.8mm / min; if the thickness-to-diameter ratio is >8:1, the drill bit speed n3=35k r / min and the feed rate per layer is reduced by 30%. When the completed hole diameter is 3-4.6mm, use a drill bit with a diameter of 2.95-4.55mm, and use a layer cutting method for drilling. The drill bit speed n4=22 kr / min and the feed rate of each layer F4=0.25mm / min. Electroplating, also known as copper plating, forms a copper plating layer inside the hole.

[0007] Furthermore, the copper plating process employs segmented chemical deposition to control the deposition rate within the holes, with a deposition rate of 1.2 μm / min at the hole opening and 0.8 μm / min at the bottom of the hole, resulting in a backlight rating of ≥9.5 after copper plating.

[0008] Furthermore, the copper plating solution includes the following components: CuSO4·5H2O 12-15g / L, EDTA-Na2 35-40g / L, formaldehyde 8-10mL / L, 2-mercaptobenzothiazole 0.5-1ppm.

[0009] Furthermore, the temperature of the copper immersion solution was 28.5±0.5℃.

[0010] Furthermore, the copper plating was performed under ultrasonic vibration conditions at a frequency of 40 kHz.

[0011] Furthermore, the electroplating process employs pulse electroplating, and the electroplating process parameters are as follows: Forward current density: 15 ASF, pulse width: 50 ms; Reverse current density: 5 ASF, pulse width: 10 ms.

[0012] Furthermore, the electroplating solution includes the following components: Cu²⁺ 22±0.5g / L, H₂SO₄ 200g / L, Cl⁻ 60ppm, Additive EP-3000A 4mL / L.

[0013] Compared with existing technologies, the high-reliability via copper control method for automotive circuit boards provided by this invention has the following advantages: The present invention provides a high-reliability hole copper control method for automotive circuit boards. By adjusting the drilling process parameters according to the hole diameter and thickness-to-diameter ratio, the hole wall roughness is improved to ≤25um. Furthermore, by optimizing the copper plating and electroplating process parameters, the uniformity of copper thickness inside the hole is improved, so that the thinnest point of the copper in the hole after electroplating is ≥25um, which meets the process production requirements and improves the quality of the circuit board and the pass rate of high thickness-to-diameter ratio circuit boards.

[0014] II. The high-reliability via copper control method for automotive circuit boards of the present invention results in circuit boards with high reliability, which is particularly suitable for the manufacture of high-density interconnect (HDI) boards for new energy vehicles and can meet the automotive-grade reliability requirements of IATF 16949.

[0015] Specific implementation party To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0016] It should be noted that the descriptions of these embodiments are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] A method for controlling high-reliability via copper in automotive circuit boards includes the following steps: Drilling parameters are adjusted according to the hole diameter and thickness-to-diameter ratio, as follows: When the finished hole diameter is 0.3-0.5mm, use a drill bit with a diameter of 0.25-0.45mm: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n1=140k r / min, and the feed rate F1=2.0mm / min; if the thickness-to-diameter ratio is >8:1, the drill bit speed is 0.9*n1, and the feed rate is 0.8*F1. When the hole diameter is 0.9-1.3mm, use a drill bit with a diameter of 0.85-1.25mm: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n2=55k r / min and the feed rate F2=2.8mm / min; if the thickness-to-diameter ratio is >8:1, drill according to the parameters for a thickness-to-diameter ratio ≤8:1 and then perform helical milling. When the finished hole diameter is 1.4-1.8mm, use a drill bit with a diameter of 1.35-1.75mm and adopt a layered cutting method for drilling: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n3=35k r / min and the feed rate F3=2.8mm / min; if the thickness-to-diameter ratio is >8:1, the drill bit speed n3=35k r / min and the feed rate per layer is reduced by 30%. When the completed hole diameter is 3-4.6mm, use a drill bit with a diameter of 2.95-4.55mm, and use a layer cutting method for drilling. The drill bit speed n4=22 kr / min and the feed rate of each layer F4=0.25mm / min. Copper plating is performed using segmented chemical deposition to control the deposition rate within the holes, with a deposition rate of 1.2 μm / min at the hole opening and 0.8 μm / min at the bottom of the holes. After copper plating, the backlight rating is ≥9.5. The copper plating solution includes the following components: CuSO4·5H2O 12-15g / L, EDTA-Na2 35-40g / L, formaldehyde 8-10mL / L, 2-mercaptobenzothiazole 0.5-1ppm.

[0018] The temperature of the copper plating solution is 28.5±0.5℃. Preferably, the copper plating is carried out under ultrasonic vibration conditions with an ultrasonic frequency of 40kHz. Pulse electroplating, electroplating process parameters are as follows: Forward current density: 15 ASF, pulse width: 50 ms; Reverse current density: 5 ASF, pulse width: 10 ms.

[0019] The electroplating solution includes the following components: Cu²⁺ 22±0.5g / L, H₂SO₄ 200g / L, Cl⁻ 60ppm, Additive EP-3000A 4mL / L.

[0020] The method of the present invention will be described in detail below through specific embodiments.

[0021] Example 1: High Aspect Ratio Microhole Machining A method for controlling high-reliability via copper in automotive circuit boards includes the following steps: Drilling: plate thickness 3.2mm, hole diameter 0.3mm, thickness-to-diameter ratio 10.7:1. Drilling parameters: use a 0.25mm diameter drill bit, drill bit speed 126k r / min, feed rate 1.6mm / min. Copper plating was performed using segmented chemical deposition to control the deposition rate within the holes, with a deposition rate of 1.2 μm / min at the hole opening and 0.8 μm / min at the bottom of the holes. The resulting backlight rating was ≥9.5. The copper plating solution contained the following components: CuSO4·5H2O 12g / L, EDTA-Na2 36g / L, formaldehyde 8mL / L, 2-mercaptobenzothiazole 0.8ppm.

[0022] The temperature of the copper immersion solution was 28.5 ± 0.5℃; Pulse electroplating, electroplating process parameters are as follows: Forward current density: 15 ASF, pulse width: 50 ms; Reverse current density: 5 ASF, pulse width 10 ms; The electroplating solution includes the following components: Cu²⁺ 22±0.5g / L, H₂SO₄ 200g / L, Cl⁻ 60ppm, additive EP-3000A 4mL / L.

[0023] Through cross-section analysis, the hole wall roughness Ra of Example 1 is 24.3 μm (28.7 μm in the traditional process), and the copper thickness of the hole is 26.5 μm (25.1 μm at the thinnest point), which meets the standard requirements. Example 2: Machining of Extra-Large Holes A method for controlling high-reliability via copper in automotive circuit boards includes the following steps: Drilling was performed to achieve a hole diameter of 4.6 mm. A 4.55 mm diameter drill bit was used, and layered cutting (3 layers) was employed. The drill bit speed was 22 kr / min, and the feed rate for each layer was 0.25 mm / min. Copper plating was performed using segmented chemical deposition to control the deposition rate within the holes, with a deposition rate of 1.2 μm / min at the hole opening and 0.8 μm / min at the bottom of the holes. The resulting backlight rating was ≥9.5. The copper plating solution contained the following components: CuSO4·5H2O 12g / L, EDTA-Na2 36g / L, formaldehyde 8mL / L, 2-mercaptobenzothiazole 0.8ppm.

[0024] The copper plating solution temperature was 28.5±0.5℃, and the copper plating was carried out under ultrasonic vibration conditions with an ultrasonic frequency of 40kHz. Pulse electroplating, electroplating process parameters are as follows: Forward current density: 15 ASF, pulse width: 50 ms; Reverse current density: 5 ASF, pulse width 10 ms; The electroplating solution includes the following components: Cu²⁺ 22±0.5g / L, H₂SO₄ 200g / L, Cl⁻ 60ppm, additive EP-3000A 4mL / L.

[0025] Through cross-section analysis, the taper of the hole wall in Example 2 was <0.05mm, and the uniformity of the copper thickness in the hole was ±1.2μm.

[0026] The high-reliability via copper control method for automotive circuit boards of the present invention, compared with traditional processes, has the following technical advantages: ; Reliability tests were conducted on circuit boards manufactured using the method of this invention and circuit boards manufactured using conventional processes. 1. Thermal shock test (-40℃~125℃, 1000 cycles), the test results are as follows: This invention: No cracking in the copper holes; Traditional process: 17% of samples showed microcracks; 2. Current load test (50A for 24 hours), the test results are as follows: This invention: Temperature rise < 8℃; Traditional process: Temperature rise of 15-20℃.

[0027] Therefore, the method of the present invention is particularly suitable for the manufacture of high-density interconnect (HDI) boards for new energy vehicles, and can meet the IATF 16949 automotive-grade reliability requirements.

[0028] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for controlling high-reliability via copper in automotive circuit boards, characterized in that, Includes the following steps: Drilling parameters are adjusted according to the hole diameter and thickness-to-diameter ratio, as follows: When the finished hole diameter is 0.3-0.5mm, use a drill bit with a diameter of 0.25-0.45mm: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n1=140k r / min, and the feed rate F1=2.0mm / min; if the thickness-to-diameter ratio is >8:1, the drill bit speed is 0.9*n1, and the feed rate is 0.8*F1. When the hole diameter is 0.9-1.3mm, use a drill bit with a diameter of 0.85-1.25mm: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n2=55k r / min and the feed rate F2=2.8mm / min; if the thickness-to-diameter ratio is >8:1, drill according to the parameters for a thickness-to-diameter ratio ≤8:1 and then perform helical milling. When the finished hole diameter is 1.4-1.8mm, use a drill bit with a diameter of 1.35-1.75mm and adopt a layered cutting method for drilling: if the thickness-to-diameter ratio is ≤8:1, the drill bit speed n3=35k r / min and the feed rate F3=2.8mm / min; if the thickness-to-diameter ratio is >8:1, the drill bit speed n3=35k r / min and the feed rate per layer is reduced by 30%. When the completed hole diameter is 3-4.6mm, use a drill bit with a diameter of 2.95-4.55mm, and use a layer cutting method for drilling. The drill bit speed n4=22 kr / min and the feed rate of each layer F4=0.25mm / min. Electroplating, also known as copper plating, forms a copper plating layer inside the hole.

2. The method for controlling high-reliability via copper in automotive circuit boards according to claim 1, characterized in that, The copper plating process uses segmented chemical deposition to control the deposition rate inside the hole, with a deposition rate of 1.2 μm / min at the hole opening and 0.8 μm / min at the bottom of the hole. After copper plating, the backlight level is ≥9.

5.

3. The method for controlling high-reliability via copper in automotive circuit boards according to claim 1, characterized in that, The copper plating solution includes the following components: CuSO4·5H2O 12-15g / L, EDTA-Na2 35-40g / L, formaldehyde 8-10mL / L, 2-mercaptobenzothiazole 0.5-1ppm.

4. The method for controlling high-reliability via copper in automotive circuit boards according to claim 3, characterized in that, The temperature of the copper plating solution was 28.5±0.5℃.

5. The method for controlling high-reliability via copper in automotive circuit boards according to claim 4, characterized in that, The copper plating was performed under ultrasonic vibration conditions at a frequency of 40 kHz.

6. The method for controlling high-reliability via copper in automotive circuit boards according to claim 1, characterized in that, The electroplating process uses pulse electroplating, and the electroplating process parameters are as follows: Forward current density: 15 ASF, pulse width: 50 ms; Reverse current density: 5 ASF, pulse width: 10 ms.

7. The method for controlling high-reliability via copper in automotive circuit boards according to claim 6, characterized in that, The electroplating solution includes the following components: Cu²⁺ 22±0.5g / L, H₂SO₄ 200g / L, Cl⁻ 60ppm, Additive EP-3000A 4mL / L.