Printed circuit board (PCB) processing technology for printing multi-layer stepped thick gold plating

Abstract

The invention discloses a PCB processing technology for printing multi-layer stepped thick gold plating, and belongs to the field of multi-layer PCB processing. The PCB processing technology for printing multi-layer stepped thick gold plating comprises the following steps: designing a PCB, and carrying out hierarchical planning; overlapping and laminating the insulating material and the copper foil layer according to the design, and performing interlayer alignment by using an optical alignment system; laser drilling equipment is adopted to drill holes in the laminated plate for electrical connection and hole penetrating; a chemical nickel-copper plating process is used, and plating is carried out in the hole wall; forming a circuit pattern on the surface of the plating layer by using a photoetching technology; redundant materials are removed by using an etching technology; plating thick gold on the copper layer by using an electroplating technology; and measuring the thickness of the gold-plated layer, assembling the processed PCB, and carrying out electrical test. In the laminating process, the optical alignment system is used for carrying out interlayer alignment, so that the alignment precision is ensured, and the problems of signal transmission loss, short circuit or open circuit and the like are avoided.

Description

Technical Field

[0001] The invention belongs to the field of multi-layer PCB processing, and in particular relates to a PCB processing technology for printing multi-layer stepped thick gold plating. Background Art

[0002] As electronic products develop towards higher integration and miniaturization, multi-layer step thick gold plating technology is also constantly improving, and the demand for high-frequency and high-speed applications is increasing. For example, the demand for multi-layer step thick gold plating PCBs in fields such as 5G communications, automotive electronics, and high-performance computing continues to grow. Modern PCB manufacturing processes use advanced gold plating technologies, such as electroless gold plating and electroplated gold, to improve the thickness and uniformity of the gold plating layer.

[0003] The manufacture of multi-layer PCBs requires higher precision inter-layer alignment and insulation, as well as more complex plating and de-plating processes. These technological advances enable PCBs to withstand higher current density and more complex electrical signal transmission.

[0004] In the manufacturing process of multi-layer PCB, each layer needs to be precisely aligned. If it cannot be precisely aligned, problems such as signal transmission loss, short circuit or open circuit will occur. For this reason, a PCB processing technology for printing multi-layer stepped thick gold plating is proposed. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a PCB processing technology for printing multi-layer stepped thick gold plating, which solves the problems in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The PCB processing technology for printing multi-layer stepped thick gold plating includes the following steps:

[0008] S1, design PCB and perform hierarchical planning;

[0009] S2, laminating the insulating material and the copper foil layer according to the design, and using an optical alignment system to align the layers;

[0010] S3, using laser drilling equipment to drill holes on the laminated board for electrical connections and through holes;

[0011] S4, using chemical nickel-copper plating process, the coating is carried out inside the hole wall;

[0012] S5, using photolithography to form circuit patterns on the surface of the coating; and using etching to remove excess material

[0013] S6, thick gold is plated on the copper layer using electroplating technology;

[0014] S7, measure the thickness of the gold-plated layer, and assemble the processed PCB for electrical testing.

[0015] Furthermore, the step of laminating the insulating material and the copper foil layer comprises:

[0016] S21, select insulation material and copper foil;

[0017] S22, cutting the insulating material and copper foil into designed sizes and cleaning each layer of material;

[0018] S23, using a coating machine to evenly coat the laminating adhesive on the surface of the insulating material;

[0019] S24, aligning and stacking the adhesive-coated insulating material and the copper foil according to the designed sequence.

[0020] Further, the step of performing interlayer alignment using the optical alignment system includes:

[0021] S241, capturing an image of the layer using a CCD camera;

[0022] S242, uses a Gaussian filter to remove image noise and adjusts image contrast to make features more obvious;

[0023] S243, using the Canny edge detection algorithm to extract edge information of the image and mark key feature points;

[0024] S244, comparing the current image with a pre-stored template image, finding similar regions using a normalized cross-correlation matching algorithm, and matching image feature points using a SIFT algorithm;

[0025] S245, analyzing the matching results, calculating the deviation between the actual image feature points and the target position, and estimating the geometric transformation required to correct the deviation;

[0026] S246, adjusting the image position or aligning the layers according to the calculated deviation and transformation estimation result;

[0027] S247, check the adjusted image to confirm whether the alignment error is within the allowable range.

[0028] Furthermore, the steps of extracting image edge information using the Canny edge detection algorithm are:

[0029] 1) Convert the image to a grayscale image to reduce processing complexity and computational effort;

[0030] 2) Apply a Gaussian filter to the grayscale image to remove noise and details;

[0031] 3) Calculate the gradient magnitude and direction of the image;

[0032] Gradient in the horizontal (G x ) and vertical (G y ) direction calculation formula:

[0033]

[0034] In the formula, G x (x,y) and G y (x, y) are the gradients in the horizontal and processing directions, respectively. blurred (x,y) is the image after Gaussian filtering,

[0035] The gradient magnitude M(x,y) is:

[0036]

[0037] The gradient direction θ(x,y) is:

[0038]

[0039] 4) Check edge points along the gradient direction, compare the gradient magnitude of each pixel with its neighboring value in the gradient direction, and retain the local maximum value;

[0040] 5) Use dual thresholds to distinguish strong edges, weak edges, and non-edges; if the gradient magnitude M(x, y) is greater than the high threshold T high , then the point is a strong edge; if it is less than the low threshold T low If it is between two thresholds, it is a weak edge and needs to be connected to a strong edge to be retained;

[0041] 6) Represent the edge information as a binary image, with white representing the edge and black representing the non-edge, and save it.

[0042] Furthermore, the steps of finding similar regions using the normalized cross-correlation matching algorithm are:

[0043] 1) Calculate the mean μ of the template image T T and standard deviation σ T :

[0044]

[0045] Where N is the total number of template pixels, T(i) is the gray value of the i-th pixel in the template image;

[0046] 2) Calculate the mean μ of the target image I I (x,y) and standard deviation σ I (x,y):

[0047]

[0048] Where m is the number of pixels in the region of a given template position (x, y);

[0049] 3) Calculate the normalized cross-correlation coefficient NCC(x,y) for each position (x,y):

[0050]

[0051] 4) In the calculated normalized mutual correlation coefficient image, find the point with the largest correlation coefficient as the template matching position.

[0052] Furthermore, the steps of matching image feature points using the SIFT algorithm are:

[0053] 1) First, construct a Gaussian pyramid to generate images at different scales; then calculate the DoG images between images of different scales and detect local extreme points as potential feature points;

[0054] 2) Calculate the gradient direction and magnitude in the area around the feature point to generate a feature descriptor, which represents the local features of the area around the feature point;

[0055] 3) Calculate the Euclidean distance between the descriptors of each feature point and use the nearest neighbor method or the two-way matching method to find the most similar descriptor pair;

[0056] 4) Perform RANSAC algorithm on the matched feature points to remove false matches.

[0057] Furthermore, in S245, the Euclidean distance between the actual image feature point and the target position is calculated to obtain the deviation between the two.

[0058] Furthermore, in the etching technology, the etching solution includes a FeCl3 solution with a concentration of 20%-40%, the pH value of the etching solution is between 1.5-2.5, the etching time is 10-20 minutes, and the etching temperature is 35-50°C.

[0059] Furthermore, when plating thick gold, the current distribution is adjusted to ensure uniformity of the plating layer; the current distribution adjustment includes:

[0060] 1) Adjust the shape, position and quantity of electrodes;

[0061] 2) Adjustment of the current channel shape design.

[0062] PCB processing system for printing multi-layer step thick gold plating, including:

[0063] Design planning module: design PCB and perform hierarchical planning;

[0064] Alignment lamination module: laminate the insulating material and copper foil layer according to the design, and use the optical alignment system to align the layers;

[0065] Laser drilling module: laser drilling equipment is used to drill holes on the laminated board for electrical connections and through holes;

[0066] Hole wall plating module: Use chemical nickel-copper plating process to plate inside the hole wall;

[0067] Photolithography and Etching Module: Use photolithography to form circuit patterns on the surface of the coating; and use etching technology to remove excess material

[0068] Thick gold plated module: Use electroplating technology to plate thick gold on the copper layer;

[0069] And, the test module: measures the thickness of the gold-plated layer, and assembles the processed PCB for electrical testing.

[0070] Beneficial effects of the present invention:

[0071] 1. The present invention uses an optical alignment system to perform inter-layer alignment during the lamination process in the PCB processing technology, thereby ensuring alignment accuracy and avoiding problems such as signal transmission loss, short circuit or open circuit.

[0072] 2. The present invention ensures the uniformity of the coating by adjusting the current distribution.

[0073] 3. The present invention adjusts the electroplating parameters to avoid metal migration that may cause weak areas or holes in the plating layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0075] Figure 1 It is a PCB processing process flow chart of the present invention. DETAILED DESCRIPTION

[0076] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0077] like Figure 1As shown in the figure, the PCB processing technology for printing multi-layer stepped thick gold plating includes the following steps:

[0078] S1, design PCB and perform hierarchical planning;

[0079] Determine the number of layers, interlayer structure and signal distribution of the PCB, and use high-precision design software to define the signal routing, vias and power supply of each layer; the high-precision design software is Allegro or Altium Designer.

[0080] S2, laminating the insulating material and the copper foil layer according to the design, and using an optical alignment system to align the layers;

[0081] Use a laminator for lamination. The lamination temperature of the laminator is 160-180℃ and the pressure is 6-8MPa. The lamination process is as follows:

[0082] S21, choose high-quality insulating materials (such as FR-4 or high-frequency materials) and copper foil;

[0083] S22, cutting the insulating material (sheet material) and copper foil into the designed size; cleaning each layer of material to remove surface oil and dust, using an ultrasonic cleaner or chemical cleaning agent;

[0084] S23, using a coating machine to evenly coat the laminating adhesive on the surface of the insulating material;

[0085] S24, stacking the adhesive-coated insulating material and the copper foil according to a designed sequence;

[0086] During the stacking process, an optical alignment system is used to achieve precise alignment between layers to avoid misalignment; the specific steps are as follows:

[0087] S241, capturing an image of the layer using a CCD (charge coupled device) camera;

[0088] S242, using a Gaussian filter to remove image noise and improve image quality; and adjusting image contrast to make features more obvious;

[0089] S243, using the Canny edge detection algorithm to extract edge information of the image; and marking key feature points (hole positions, line intersections, etc.);

[0090] The steps to extract image edge information using the Canny edge detection algorithm are:

[0091] 1) Convert the image to a grayscale image to reduce processing complexity and computational effort;

[0092] 2) Apply a Gaussian filter to the grayscale image to remove noise and details;

[0093] 3) Calculate the gradient magnitude and direction of the image to detect edges;

[0094] Gradient in the horizontal (G x ) and vertical (G y ) direction calculation formula:

[0095]

[0096] In the formula, G x (x,y) and G y (x, y) are the gradients in the horizontal and processing directions, respectively. blurred (x,y) is the image after Gaussian filtering,

[0097] The gradient magnitude M(x,y) is:

[0098]

[0099] The gradient direction θ(x,y) is:

[0100]

[0101] 4) Check edge points along the gradient direction, compare the gradient magnitude of each pixel with its neighboring value in the gradient direction, retain the local maximum value and suppress other values;

[0102] 5) Use dual thresholds to distinguish strong edges, weak edges, and non-edges;

[0103] If the gradient magnitude M(x,y) is greater than the high threshold T high , then the point is a strong edge; if it is less than the low threshold T low If it is between the two thresholds, it is a weak edge and needs to be connected to a strong edge to be retained; the specific formula is:

[0104]

[0105] Where Edge(x,y) represents the edge point classification result.

[0106] 6) Represent the edge information as a binary image, with white representing the edge and black representing the non-edge, and save it.

[0107] S244, comparing the current image with a pre-stored template image, finding similar regions using a normalized cross-correlation matching algorithm, and matching image feature points using a SIFT algorithm;

[0108] The steps to find similar regions using the normalized cross-correlation matching algorithm are:

[0109] 1) Calculate the mean μ of the template image T T and standard deviation σT ;

[0110]

[0111] Where N is the total number of template pixels, T(i) is the gray value of the i-th pixel in the template image;

[0112] 2) Calculate the mean μ of the target image I I (x,y) and standard deviation σ I (x,y);

[0113]

[0114] Where m is the number of pixels within the region of a given template location (x, y).

[0115] 3) Calculate the normalized cross-correlation coefficient NCC(x,y) for each position (x,y);

[0116]

[0117] 4) In the calculated normalized mutual correlation coefficient image, find the point with the largest correlation coefficient as the template matching position.

[0118] The steps to match image feature points using the SIFT algorithm are:

[0119] 1) Detect feature points in the image and use Gaussian pyramid and difference of Gaussian (DoG) to detect extreme points in the scale space; specifically: first construct a Gaussian pyramid to generate images at different scales; then calculate the DoG images between images of different scales and detect local extreme points as potential feature points;

[0120] 2) Calculate the gradient direction and magnitude in the area around the feature point to generate a feature descriptor, which is a high-dimensional vector that represents the local features of the area around the feature point;

[0121] 3) Calculate the Euclidean distance between the descriptors of each feature point and use the nearest neighbor method or the two-way matching method to find the most similar descriptor pair;

[0122] 4) Perform RANSAC (Random Sampling Consensus) algorithm on the matched feature points to remove false matches and improve the matching accuracy.

[0123] S245, analyzing the matching results, calculating the deviation between the actual image feature points and the target position, and estimating the geometric transformation required to correct the deviation;

[0124] The Euclidean distance between the actual image feature points and the target position is calculated to obtain the deviation between the two.

[0125] S246, adjusting the image position or aligning the layers according to the calculated deviation and transformation estimation result;

[0126] S247, check the adjusted image to confirm whether the alignment error is within the allowable range.

[0127] S3, precision drilling of holes in the laminated board for electrical connections and through-holes;

[0128] In this embodiment, laser drilling technology is used to improve the accuracy and consistency of the holes.

[0129] S4, uses a chemical nickel-copper plating process to plate inside the hole wall, ensuring good electrical connection and preventing signal interference.

[0130] S5, using photolithography to form a circuit pattern on the surface of the coating; and using etching technology to remove excess material;

[0131] The etching solution includes a FeCl3 solution with a concentration of 20%-40%, the pH value of the etching solution is between 1.5-2.5, the etching time is 10-20 minutes, and the etching temperature is 35-50°C.

[0132] S6, thick gold is plated on the copper layer using electroplating technology;

[0133] Ensure uniformity of the coating by adjusting the current distribution; and adjust the electroplating parameters to avoid weak coatings or holes caused by metal migration;

[0134] Among them, the current distribution adjustment includes:

[0135] 1) Adjust the shape, position and quantity of electrodes;

[0136] 2) Adjustment of current trough shape design;

[0137] Electroplating parameter adjustments include:

[0138] 1) Current density adjustment: During the electroplating process, the current density can be adjusted within a certain range to obtain the best coating quality; in this embodiment, the current density adjustment range of gold electroplating is 0.5-5A / dm 2 , adjusted according to the characteristics of the plating solution and workpiece.

[0139] 2) Adjust the electroplating time; according to the thickness requirements of the workpiece and the current density setting, control the electroplating time to ensure uniform coating thickness; during the electroplating process, the electroplating time needs to be adjusted according to the real-time monitoring results to ensure the consistency of the coating.

[0140] S7, use microscopes and other inspection tools to measure the thickness of the gold-plated layer, and assemble the finished PCB for electrical testing to check the integrity of signal transmission, insulation between layers, and electrical performance to ensure there is no inter-layer interference.

[0141] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0142] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. The PCB processing technology for printing multi-layer stepped thick gold plating is characterized by: The following steps are involved: S1, design PCB and perform hierarchical planning; S2, laminating the insulating material and the copper foil layer according to the design, and using an optical alignment system to align the layers; S3, using laser drilling equipment to drill holes on the laminated board for electrical connections and through holes; S4, using chemical nickel-copper plating process, the coating is carried out inside the hole wall; S5, using photolithography to form a circuit pattern on the surface of the coating; and using etching technology to remove excess material; S6, thick gold is plated on the copper layer using electroplating technology; S7, measure the thickness of the gold-plated layer, and assemble the processed PCB for electrical testing.

2. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 1 is characterized in that: The steps of laminating the insulating material and the copper foil layer include: S21, select insulation material and copper foil; S22, cutting the insulating material and copper foil into designed sizes and cleaning each layer of material; S23, using a coating machine to evenly coat the laminating adhesive on the surface of the insulating material; S24, aligning and stacking the adhesive-coated insulating material and the copper foil according to the designed sequence.

3. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 2 is characterized in that: The steps for inter-layer alignment using an optical alignment system include: S241, capturing an image of the layer using a CCD camera; S242, uses a Gaussian filter to remove image noise and adjusts image contrast to make features more obvious; S243, using the Canny edge detection algorithm to extract edge information of the image and mark key feature points; S244, comparing the current image with a pre-stored template image, finding similar regions using a normalized cross-correlation matching algorithm, and matching image feature points using a SIFT algorithm; S245, analyzing the matching results, calculating the deviation between the actual image feature points and the target position, and estimating the geometric transformation required to correct the deviation; S246, adjusting the image position or aligning the layers according to the calculated deviation and transformation estimation result; S247, check the adjusted image to confirm whether the alignment error is within the allowable range.

4. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 3 is characterized in that: The steps to extract image edge information using the Canny edge detection algorithm are: 1) Convert the image to a grayscale image to reduce processing complexity and computational effort; 2) Apply a Gaussian filter to the grayscale image to remove noise and details; 3) Calculate the gradient magnitude and direction of the image; Gradient in the horizontal (G x ) and vertical (G y ) direction calculation formula: In the formula, G x (x,y) and G y (x, y) are the gradients in the horizontal and processing directions, respectively. blurred (x,y) is the image after Gaussian filtering, The gradient magnitude M(x,y) is: The gradient direction θ(x,y) is: 4) Check edge points along the gradient direction, compare the gradient magnitude of each pixel with its neighboring value in the gradient direction, and retain the local maximum value; 5) Use dual thresholds to distinguish strong edges, weak edges, and non-edges; if the gradient magnitude M(x, y) is greater than the high threshold T high , then the point is a strong edge; if it is less than the low threshold T low It is non-marginal; If it is between the two thresholds, it is a weak edge and needs to be connected to a strong edge to be retained; 6) Represent the edge information as a binary image, with white representing the edge and black representing the non-edge, and save it.

5. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 3 is characterized in that: The steps to find similar regions using the normalized cross-correlation matching algorithm are: 1) Calculate the mean μ of the template image T T and standard deviation σ T : Where N is the total number of template pixels, T(i) is the gray value of the i-th pixel in the template image; 2) Calculate the mean μ of the target image I I (x,y) and standard deviation σ I (x,y): Where m is the number of pixels in the region of a given template position (x, y); 3) Calculate the normalized cross-correlation coefficient NCC(x,y) for each position (x,y): 4) In the calculated normalized mutual correlation coefficient image, find the point with the largest correlation coefficient as the template matching position.

6. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 5 is characterized in that: The steps to match image feature points using the SIFT algorithm are: 1) First, construct a Gaussian pyramid to generate images at different scales; then calculate the DoG images between images of different scales and detect local extreme points as potential feature points; 2) Calculate the gradient direction and magnitude in the area around the feature point to generate a feature descriptor, which represents the local features of the area around the feature point; 3) Calculate the Euclidean distance between the descriptors of each feature point and use the nearest neighbor method or the two-way matching method to find the most similar descriptor pair; 4) Perform RANSAC algorithm on the matched feature points to remove false matches.

7. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 3 is characterized in that: In S245, the Euclidean distance between the actual image feature point and the target position is calculated to obtain the deviation between the two.

8. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 1 is characterized in that: In the etching technology, the etching solution includes a FeCl3 solution with a concentration of 20%-40%, the pH value of the etching solution is between 1.5-2.5, the etching time is 10-20 minutes, and the etching temperature is 35-50°C.

9. The PCB processing technology for printing multi-layer stepped thick gold plating according to claim 1 is characterized in that: When plating thick gold, the current distribution is adjusted to ensure uniformity of the plating layer; the current distribution adjustment includes: 1) Adjust the shape, position and quantity of electrodes; 2) Adjustment of the current channel shape design.

10. A PCB processing system for printing multi-layer stepped thick gold plating, characterized in that: include: Design planning module: design PCB and perform hierarchical planning; Alignment lamination module: laminate the insulating material and copper foil layer according to the design, and use the optical alignment system to align the layers; Laser drilling module: laser drilling equipment is used to drill holes on the laminated board for electrical connections and through holes; Hole wall plating module: Use chemical nickel-copper plating process to plate inside the hole wall; Photolithography and Etching Module: Use photolithography to form circuit patterns on the surface of the coating; and use etching technology to remove excess material Thick gold plated module: Use electroplating technology to plate thick gold on the copper layer; And, the test module: measures the thickness of the gold-plated layer, and assembles the processed PCB for electrical testing.

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