Manufacturing method of precise hole circuit board with high bearing capacity and large thickness-diameter ratio

Abstract

The invention discloses a manufacturing method of a high-bearing-capacity large-thickness-diameter-ratio precise type hole circuit board, and the method comprises the steps: carrying out the thickness reduction processing of an insulating dielectric layer of a prepreg and an insulating dielectric layer of a copper-clad plate, carrying out the processing till a pressing process, forming a first pressed plate, manufacturing a first via hole in the first pressed plate, manufacturing a first surface circuit on a first surface, and forming a first sub-plate; a thickening layer is manufactured to be stacked and laminated with the first sub-board, a second via hole is manufactured, the diameter of the first via hole is smaller than that of the second via hole, a surface circuit is manufactured, a copper layer contained in the thickening layer is manufactured to form a second surface circuit, the first surface circuit is the same as the second surface circuit, and the whole board forms the circuit board; through redesign of the structure of the circuit board, the thickness of the thinning prepreg and the thickness of the thinning copper-clad plate are adjusted under the condition that the overall thickness is not changed, so that thinning of the first pressing plate is achieved, the thickness-diameter ratio is effectively reduced, and the machining precision of electroplating hole machining is improved.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit board manufacturing, and particularly to a manufacturing method for high-load large aspect ratio precision via-hole circuit boards. Background Art

[0002] For a type of circuit board applied to new energy vehicles or industrial control equipment, its design requirements are more stringent compared to traditional application scenarios. Generally, it is required to have a relatively thick board thickness to provide stronger load-bearing capacity and fixed stability, ensuring that other electronic components can be effectively soldered or plugged in, and can be firmly fixed at the designated position by methods such as screws, preventing problems such as bending and loosening during actual application.

[0003] With the accelerating development speed of new energy vehicles and the automation field, the requirements for circuit boards have also changed from basic functionality to high precision. This trend has also promoted an increase in the design demand for circuit boards with a large aspect ratio (i.e., the ratio of the thickness of the finished board body to the diameter of the finished hole). These circuit boards are required to not only have a thicker board body but also a smaller hole diameter to meet the high-performance and miniaturization requirements of modern electronic products.

[0004] Currently, the methods for manufacturing such large aspect ratio circuit boards mainly include "manufacturing each layer of core board → multi-layer lamination → drilling → electroplating → via-hole plugging (if required) → secondary electroplating → manufacturing surface circuit patterns → post-processing".

[0005] However, for circuit boards with a relatively large aspect ratio (generally greater than or equal to 12:1, especially greater than or equal to 15:1), whether it is electroplating the via-hole copper or performing via-hole plugging processing, due to the small hole diameter and large depth, it is easy to cause incomplete electroplating, resulting in problems such as no copper in the hole or insufficiently full via-hole copper; during the via-hole plugging process, there may be a phenomenon that the ink cannot fully fill the holes or there are air bubbles hidden in the holes; particularly, when the circuit board needs to support flip-chip soldering and is designed with dense BGA pads with "via-in-pad", its manufacturing difficulty will be further increased.

[0006] Therefore, for this type of circuit board with the characteristics of a relatively large board body thickness and a small hole diameter, a manufacturing method is needed that can reduce the processing difficulty while improving the quality and reliability of the circuit board. Summary of the Invention

[0007] The present invention aims to solve the comprehensive problems such as low processing accuracy and high processing difficulty of high-load large aspect ratio printed circuit boards in the prior art, and proposes a manufacturing method for high-load large aspect ratio precision via printed circuit boards. The printed circuit board is processed according to design data, and the maximum aspect ratio in the design data is ≥12:1. The printed circuit board is designed with a forming line. The area within the forming line is the effective area within the board, and the area outside is the board edge tooling area. The printed circuit board is composed of a surface copper layer, a prepreg, and a copper clad laminate. The manufacturing method includes the following steps: S10: Thinning the thickness of the prepreg and the thickness of the insulating dielectric layer of the copper clad laminate to form a thinned prepreg and a thinned copper clad laminate. Making an inner layer circuit pattern on the thinned copper clad laminate, and then proceeding to the lamination process to form a first laminated board. S20: Making a first via hole in the first laminated board, and then making a first surface circuit on one side to form a first sub-board. S30: Making a thickening layer; Stacking the thickening layer and the first sub-board, with the first surface circuit corresponding to the thickening layer, and then performing a second lamination to form a second laminated board. S40: Making a second via hole in the second laminated board and making a surface circuit. A second surface circuit is formed on the surface of the thickening layer, and the entire board forms the printed circuit board; The first surface circuit is the same as the second surface circuit; The diameter of the first via hole is smaller than the diameter of the second via hole.

[0008] Further, the thinning process is to replace the standard type of the prepreg to form the thinned prepreg, and replace the standard type of the copper clad laminate to form the thinned copper clad laminate, thereby achieving the thinning process.

[0009] Further, the thickening layer is a single-sided thinned copper clad laminate or composed of a stack of several thinned prepregs and a single-layer copper foil stacked. The first surface circuit corresponds to the insulating dielectric layer of the single-sided thinned copper clad laminate or the stacked thinned prepregs; The copper layer of the single-sided thinned copper clad laminate or the single-layer copper foil is used to make the second surface circuit.

[0010] Further, forming the first sub-board includes: filling the first via hole to form a filled board, then polishing and electroplating the filled board in sequence, and then making a first surface circuit on the first side to form the first sub-board.

[0011] Further, the maximum aspect ratio of the first laminated board is ≤12:1.

[0012] Further, the second lamination includes, in the cooling stage of lamination, after cooling the board body to less than or equal to 60 °C, continuing the lamination for 20 min to 30 min.

[0013] Further, the inner layer circuit pattern includes a target pattern distributed in the board edge tool area and several drilling measurement patterns; each of the drilling measurement patterns includes a first drilling measurement pattern, a second drilling measurement pattern to an Nth drilling measurement pattern arranged in parallel, where N is greater than or equal to 3; the first drilling measurement pattern, the second drilling measurement pattern to the Nth drilling measurement pattern are each composed of several independent circular patterns with gradually decreasing sizes; Fabricating the second via hole includes using an X-ray device to detect the target pattern for positioning, fabricating a positioning hole, then drilling corresponding to the first drilling measurement pattern with the positioning hole as a reference to form a first measurement hole, and then using an X-ray device to detect and measure the relative position between the first drilling measurement pattern and the first measurement hole, and then adjusting the drilling parameters to form the first drilling parameters; After that, it is fabricated according to the following steps: S410: Drill the second drilling measurement pattern according to the first drilling parameters to form a second measurement hole, and use an X-ray device to detect and measure the relative position between the second drilling measurement pattern and the second measurement hole, and then adjust the first drilling parameters to form the second drilling parameters; S420: Process with reference to S410 until drilling the Nth drilling measurement pattern, and then process to form the Nth drilling parameters, and fabricate the second via hole according to the Nth drilling parameters.

[0014] Further, the adjacent independent circular patterns of the first drilling measurement pattern, the second drilling measurement pattern to the Nth drilling measurement pattern have the same size.

[0015] Further, cross-shaped etching lines are fabricated at the centers of the first drilling measurement pattern and the second drilling measurement pattern.

[0016] Further, the drilling measurement patterns are fabricated on the first surface circuit.

[0017] The beneficial effects of the technical solution of the present invention mainly include: (1) By redesigning the structure of the circuit board and adjusting the standard models of the thinned prepreg and the thinned copper clad laminate, the thinning treatment of the first press plate is realized, effectively reducing the aspect ratio, making processes such as electroplated via hole copper and via hole plugging, which were originally difficult in the production of large aspect ratio circuit boards, easier to carry out, reducing the occurrence of processing problems such as no copper in the hole, insufficient copper in the hole, via hole plugging ink not entering the hole, and via hole hiding air bubbles, and significantly improving the accuracy of hole processing.

[0018] (2)A second lamination is carried out by adding an additional thickening layer. The thickness of the formed second laminated board is the same as that of the original circuit board before improvement, ensuring that the overall thickness of the circuit board remains unchanged and meets the application requirements. Also, the first surface circuit and the second surface circuit are made the same. The first vias are made corresponding to the circuit patterns of each original layer, and the added circuit layer corresponds to the effect of the first surface circuit, resulting in the surface circuit pattern remaining unchanged, meeting the single-sided soldering requirements of the first vias, and also meeting the through-layer conduction requirements or the component insertion soldering requirements of the second vias.

[0019] (3)Due to the change in the circuit board structure, the processing of the first vias and the second vias is further divided into two steps. The drill measurement PAD is used to measure and analyze at different stages, from the shrinkage and expansion after the first lamination to after the second lamination, and then the drilling parameters are adjusted. The drill measurement PAD made after the first lamination provides the initial data and reference for subsequent drill measurements, making the matching degree between the second drilling and the first drilling higher, ensuring the accuracy and consistency of parameters such as the relative position and hole diameter between each drill, providing a good consistency basis for subsequent soldering of components, avoiding soldering difficulties, poor contact and other situations caused by problems such as drill position deviation, and ensuring the smooth progress of the entire circuit board in subsequent processing links, improving production efficiency and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0021] Figure 1 It is a cross-sectional schematic diagram of a circuit board in the prior art; Figure 2 It is a process flow schematic diagram of an embodiment of the present invention; Figure 3 It is a cross-sectional schematic diagram of the first laminated board of an embodiment of the present invention; Figure 4 It is a plan view of the pattern-thinned copper clad laminate of an embodiment of the present invention; Figure 5 It is a cross-sectional schematic diagram of the first sub-board of an embodiment of the present invention; Figure 6 It is a cross-sectional schematic diagram of the second laminated board of an embodiment of the present invention; Figure 7 It is a plan view of the drill measurement pattern of an embodiment of the present invention; Figure 8Schematic plan view of a solid drilling measurement pattern according to an embodiment of the present invention; Figure 9 Schematic plan view of a drilling measurement pattern with a cross-shaped etching line according to an embodiment of the present invention; Figure 10 For Figure 7 Design data schematic diagram; Figure 11 Cross-sectional schematic view of a circuit board according to an embodiment of the present invention; Figure 12 For Figure 11 Metallurgical microscope structure diagram of the physical object of

[0022] Explanation of reference numerals: 10, circuit board with large thickness-diameter ratio of the prior art; 1010a, first copper layer; 1010b, second copper layer; 1020X, prepreg; 1030X, copper clad laminate; 1020, thinned prepreg; 1030, pattern-thinned copper clad laminate; 20, first pressing plate; 2010a, target pattern; 2010b, drilling measurement pattern; 2011, first drilling measurement pattern; 2012, second drilling measurement pattern; 2010c, forming line; 30, first sub-board; 3010, first via hole; 3020, first surface circuit; 40, thickening layer; 50, second pressing plate; 5010, measurement hole; 5010a, first measurement hole; 5010b, second measurement hole; 60, circuit board; 6010, second via hole; 6020, second surface circuit.

[0023] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that all directional indications (such as up, down, left, right, front, back, inside, outside,...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0026] In addition, in the present invention, descriptions such as "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0027] In addition, the technical solutions between various embodiments of the present invention can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] Please refer to Figure 1 , Figure 1 which is a schematic cross-sectional view of a circuit board in the prior art.

[0029] The circuit board 10 with a large thickness-to-diameter ratio in the prior art is composed of a surface copper layer (including: a first copper layer 1010a and a second copper layer 1010b), a prepreg 1020X, and a copper clad laminate 1030X. Its maximum thickness-to-diameter ratio ≥ 12:1 (i.e., the ratio of the thickness of the finished board body to the diameter of the finished hole ≥ 12:1). Especially when ≥ 15:1, the processing difficulty is great. Especially in processes such as electroplating hole copper and plugging holes, situations such as no copper in the hole, insufficient copper filling in the hole, the plugging hole ink not entering the hole, and air bubbles hidden in the plugging hole are likely to occur, seriously affecting the quality and performance of the circuit board.

[0030] Please refer to Figure 2 , Figure 2 which is a schematic process flow diagram of an embodiment of the present invention.

[0031] Based on processing requirements and processing demands, this embodiment makes a new invention and creation based on the circuit board 10 with a large thickness-to-diameter ratio in the prior art; therefore, the circuit board 10 with a large thickness-to-diameter ratio in the prior art is processed according to design data, and the maximum thickness-to-diameter ratio in the design data ≥ 12:1. The circuit board 10 with a large thickness-to-diameter ratio in the prior art is designed with a forming line 2010c. The area within the range of the forming line 2010c is the effective area inside the board, and the area outside is the tool area at the board edge; the circuit board 10 with a large thickness-to-diameter ratio in the prior art is composed of a surface copper layer (including: a first copper layer 1010a and a second copper layer 1010b), a prepreg 1020X, and a copper clad laminate 1030X.

[0032] The manufacturing process of the embodiment of the present invention includes using Figure 2 in each step process to achieve. The following will further explain each step process in Figure 2 step by step.

[0033] Please refer to Figure 3And Figure 4 , Figure 3 is a schematic cross-sectional view of the first pressing plate according to an embodiment of the present invention; Figure 4 is a schematic plan view of the pattern-thinned copper clad laminate according to an embodiment of the present invention.

[0034] S10: Thinning the thickness of the prepreg 1020X and the thickness of the insulating dielectric layer of the copper clad laminate 1030X to form a thinned prepreg 1020 and a thinned copper clad laminate, fabricating an inner layer circuit pattern on the copper layer of the thinned copper clad laminate to form a pattern-thinned copper clad laminate 1030, and then processing it to the pressing process to form a first pressing plate 20.

[0035] By thinning the prepreg 1020X, the maximum thickness-diameter ratio of the first pressing plate 20 is ≤12:1, which can significantly reduce the processing difficulty. Specifically, in the electroplating processing step, a pulse electroplating line was originally required to cope with the processing problems brought by the large thickness-diameter ratio. When the maximum thickness-diameter ratio of the first pressing plate 20 is ≤12:1, an electroplating line with a normal current can be directly used for processing without relying on a pulse electroplating line; that is, the maximum thickness-diameter ratio processing ability of the electroplating line of the normal circuit is within the range of ≤12:1. Therefore, in this embodiment, by controlling the thickness-diameter ratio of the first pressing plate 20, the processing flow is simplified to a certain extent, the processing cost is greatly reduced, and the processing quality and the first-pass qualification rate are improved.

[0036] Furthermore, the thinning process is as follows: replacing the standard model of the prepreg 1020X to form the thinned prepreg 1020, and replacing the standard model of the copper clad laminate 1030X to form the thinned copper clad laminate to achieve the thinning process.

[0037] By adjusting their standard models, while keeping the thickness of the total copper layer (the first copper layer 1010a, the second copper layer 1010b, and the copper layer of the thinned copper clad laminate) unchanged, the overall stack-up thickness is reduced, thereby reducing the thickness-diameter ratio, making it easier for the electroplating solution to be evenly distributed in the holes, and the ink is also easier to fill during hole plugging, thus reducing the processing difficulty of subsequent electroplating through-hole copper and hole plugging.

[0038] Please refer to Figure 5 , Figure 5 is a schematic cross-sectional view of the first daughter board according to an embodiment of the present invention.

[0039] S20: Fabricating a first via hole 3010 in the first pressing plate 20, and then fabricating a first surface circuit 3020 on one side to form a first daughter board 30.

[0040] Optionally, forming the first daughter board 30 includes: filling the first via hole 3010 to form a filled board, then grinding and electroplating the filled board in sequence, and then fabricating a first surface circuit 3020 on the first side to form a first daughter board 30.

[0041] Optionally, the holes are filled with resin plugs.

[0042] It should be noted that when there are "via-in-pad" designs for some circuit boards, the above process can be used to form "via-in-pad". Since the thickness of the first press plate 20 is reduced and the thickness-diameter ratio is reduced, the difficulty of filling the first via hole 3010 is also reduced, effectively avoiding problems such as poor plugging and incomplete filling, and improving processing problems such as difficult control of the processing accuracy of dense BGA pads.

[0043] Please refer to Figure 6 , Figure 6 , which is a cross-sectional schematic diagram of the second press plate of the embodiment of the present invention.

[0044] S30: Fabricate the thickening layer 40; stack the thickening layer 40 and the first sub-board 30, with the first surface circuit 3020 corresponding to the thickening layer 40, and then perform a second press to form the second press plate 50; Optionally, the thickening layer 40 is a single-sided thinned copper clad laminate or composed of a stack of thinned prepregs and a single-layer copper foil stacked, then the first surface circuit 3020 corresponds to the insulating dielectric layer of the single-sided thinned copper clad laminate or the thinned prepregs of the stack. Correspondingly, in step S40, the copper layer of the single-sided thinned copper clad laminate or the single-layer copper foil forms the second surface circuit 6020 in the subsequent process.

[0045] Furthermore, the thickness of the second press plate 50 is equal to the thickness of the large thickness-diameter ratio circuit board 10 in the prior art, that is, the thickness of the thickening layer 40 is equal to the thickness of the large thickness-diameter ratio circuit board 10 in the prior art minus the thickness of the first press plate 20.

[0046] In the previous process, the thickness-diameter ratio during the processing of the first via hole 3010 is reduced through thinning treatment, reducing the difficulty of processing procedures such as electroplating hole copper and plugging holes. At this time, the thinned part is compensated by the thickness of the thickening layer 40. This not only achieves the purpose of reducing processing difficulty but also keeps the thickness of the circuit board unchanged through the thickening layer 40 and the second press process, without affecting the actual application performance of the circuit board.

[0047] Furthermore, the second press includes, in the press cooling stage, after cooling the board body to less than or equal to 60 °C, continue to press for 20 min to 30 min.

[0048] Due to the "asymmetric" plate structure of the second pressing plate 50, the plate is prone to bowing and warping problems after pressing. According to the standard, the bowing and warping rates need to be controlled within 0.5%. In this embodiment, a slow cooling method is adopted. After the plate is cooled to below 60°C, it is pressed for another 20 to 30 minutes to appropriately extend the pressing during the cooling stage, allowing each part of the plate to have sufficient time to shrink evenly, fully release the internal stress of the plate, reduce the stress difference, ensure the flatness of the circuit board, which is beneficial to subsequent processing and use, and avoid the problem that rapid cooling will cause the internal stress of the plate not to be fully released, resulting in deformation problems such as bowing and warping of the plate.

[0049] Optionally, further, during the re-pressing and cooling stage, a slow cooling method (optionally using 2.5°C / min to 5°C / min) is adopted to appropriately extend the pressing during the cooling stage, providing more sufficient conditions for the release of the internal stress of the plate during the cooling to room temperature stage.

[0050] The parameter conditions of the pressing process (including: temperature, pressure, time) are listed in Table 1 below. Among them, the 1st, 2nd, 3rd, 4th, and 5th stages are the pressing heating stages, the 6th and 7th stages are the constant pressure pressing stages at the highest temperature, and the 8th, 9th, and 10th stages are the pressing cooling stages.

[0051] Table 1:

[0052] Please refer to Figures 7 to 10 , Figure 7 which is a schematic plan view of the drilling measurement pattern of the embodiment of the present invention; Figure 8 which is a schematic plan view of the drilling measurement pattern with a solid drilling measurement pattern of the embodiment of the present invention; Figure 9 which is a schematic plan view of the drilling measurement pattern with a cross-shaped etching line of the embodiment of the present invention; Figure 10 is Figure 7 the design data schematic diagram.

[0053] S40: Make the second via hole 6010 in the second pressing plate 50, and make the surface circuit. The second surface circuit 6020 is formed on the surface of the thickening layer 40, and the whole board forms the circuit board 60; the first surface circuit 3020 is the same as the second surface circuit 6020; the diameter of the first via hole 3010 is smaller than the diameter of the second via hole 6010.

[0054] The first surface circuit 3020 is made to be the same as the second surface circuit 6020, so that the first via hole 3010 is made corresponding to the original circuit pattern of each layer, and the added circuit layer corresponds to the effect of the first surface circuit 3020, forming the effect that the surface layer circuit pattern remains unchanged, meeting the single-sided welding requirements of the first via hole 3010, and meeting the requirements of each layer conduction or plug-in welding of the second via hole 6010.

[0055] Please refer to again Figure 4 。

[0056] Furthermore, the formed pattern of the inner layer circuit pattern in the previous process thins the copper clad laminate 1030, including the target pattern 2010a distributed in the board edge tool area outside the forming line 2010c and several drilling measurement patterns 2010b; a single drilling measurement pattern 2010b includes a first drilling measurement pattern 2011, a second drilling measurement pattern 2012 to an Nth drilling measurement pattern arranged side by side, where N is greater than or equal to 3; the first drilling measurement pattern 2011, the second drilling measurement pattern 2012 to the Nth drilling measurement pattern are each composed of several independent circular patterns with gradually decreasing sizes.

[0057] Manufacturing the second via hole 6010 includes using an X-ray device to detect the target pattern 2010a for positioning, manufacturing a positioning hole, and then drilling corresponding to the first drilling measurement pattern 2011 based on the positioning hole to form the first measurement hole 5010a. After that, use an X-ray device to detect and measure the relative position between the first drilling measurement pattern 2011 and the first measurement hole 5010a, and then adjust the drilling parameters to form the first drilling parameters.

[0058] After that, it is manufactured according to the following steps: S410: Drill the second drilling measurement pattern 2012 according to the first drilling parameters to form the second measurement hole 5010b, and use an X-ray device to detect and measure the relative position between the second drilling measurement pattern 2012 and the second measurement hole 5010b, and then adjust the first drilling parameters to form the second drilling parameters; S420: Refer to S410 for processing until drilling the Nth drilling measurement pattern, then process and form the Nth drilling parameters, and manufacture the second via hole 6010 based on the Nth drilling parameters.

[0059] Since this embodiment makes changes to the circuit board structure, and changes the method of drilling after one-time lamination used in the prior art's large aspect ratio circuit board 10 to a process of two-time lamination and two-time drilling. During the second lamination, the first laminated board 20 may have phenomena such as board body expansion, shrinkage, and offset. Therefore, by setting the drilling measurement pattern 2010b and measuring and comparing the expansion, shrinkage, and offset of the board body through the drilling measurement hole 5010, the drilling coefficient is adjusted, effectively avoiding problems such as misalignment between the second drilling and the first drilling, and with the surface circuit pattern, and ensuring the processing accuracy of the second drilling.

[0060] Further, the drilling measurement pattern 2010b is made on the first surface circuit 3020. Since the offset mainly occurs between the thickening layer 40 and the first lamination board 20, it is necessary to measure and compare the second surface circuit 6020 specifically. Since the first surface circuit 3020 and the second surface circuit 6020 are the same, when performing secondary drilling, the same requirements for drilling accuracy are imposed. Moreover, after the second lamination, the first surface circuit 3020 becomes the sub-outer layer of the second lamination board 50, and the error comparison effect between adjacent copper layers will be better, which can further strengthen the measurement effect.

[0061] Optionally, drilling measurement patterns 2010b are made on each layer of the first lamination board 20. This method can increase the selectivity of detection and measurement. Through multi-layer comparison, the drilling accuracy can be measured and adjusted more precisely. However, this method has certain defects, that is, after lamination, the thickness of the position where the drilling measurement pattern 2010b is located is superimposed, and the surface will bulge compared with the copper-free area, resulting in a decrease in the flatness of the board surface. When the copper thickness is relatively thick, it may be unfavorable for subsequent drilling and measurement work, bringing certain obstacles to the entire circuit board manufacturing process.

[0062] Optionally, the diameter size of a single drilling measurement pattern 2010b is 0.2 mm to 3.0 mm. Using a smaller size for the measurement pattern can effectively match the measurement and comparison accuracy of micro-holes.

[0063] Further, the adjacent independent circular pattern sizes of the first drilling measurement pattern 2011, the second drilling measurement pattern 2012 to the Nth drilling measurement pattern are the same.

[0064] By setting drilling measurement patterns 2010b with the same sizes of multiple adjacent independent circular patterns, measurement and comparison can be carried out at multiple positions, which is equivalent to increasing the number of measurement samples, reducing the uncertainty brought by single-pattern measurement, thereby improving the measurement accuracy, greatly increasing the accuracy rate of measuring drilling expansion and shrinkage and offset, and providing reliable data support for subsequent precise adjustment of drilling parameters.

[0065] Please refer to again Figure 7 and Figure 8 。

[0066] Optionally, the first drilling measurement pattern 2011 and the second drilling measurement pattern 2012 are hollow graphic PADs (as shown in Figure 7 ), or solid graphic PADs (as shown in Figure 8 ).

[0067] Optionally, the diameters of the drilling measurement patterns 2010b in each column decrease linearly, and there are circular pads with etched lines around them, providing a clear reference system for measuring the offset, expansion, and contraction of the drill holes. If the drill holes are offset, by observing the relative position changes between the drill holes and the drilling measurement patterns 2010b with different diameters, the offset amount can be more accurately quantified, providing an accurate basis for subsequent adjustment of the drill tape parameters and improving the drilling accuracy.

[0068] Please refer again to Figure 9 。

[0069] Optionally, cross-shaped etched lines are made at the centers of the first drilling measurement pattern 2011 and the second drilling measurement pattern 2012, providing a clearer contrast indication line for measuring the holes 5010 and improving the contrast accuracy between the measured holes 5010 and the drilling measurement patterns 2010b.

[0070] The traditional method for adjusting the second drilling parameters is to measure the target pattern 2010a using a two-dimensional measurement device or a three-dimensional measurement device, then calculate the expansion and contraction coefficient from the measured values, adjust the second drilling parameters based on this coefficient, and then test and re-measure with test holes to determine the second drilling parameters. However, two-dimensional or three-dimensional devices are special equipment, and the entire process of measurement, calculation, adjustment, and re-measurement is complex and cumbersome, not only consuming a large amount of manpower but also taking a long time. In contrast, the technical solution of the present invention directly compares the measured holes 5010 with the drilling measurement patterns 2010b, and the X-ray device itself is configured in the drilling process, having the significant advantages of directness, convenience, and high efficiency, and can greatly improve the efficiency of determining the comparison and adjusting the second drilling parameters.

[0071] It is worth noting that the first copper layer 1010a in the present invention is electroplated three times. To effectively control the copper thickness of the overall circuit board, when the first lamination is performed, a relatively thin copper foil (for example, 10 μm) is selected for the first copper layer 1010a; when the first electroplating is performed, a relatively thin copper thickness (for example, 10 μm) is electroplated, and at the same time, the hole copper thickness needs to be ensured to be qualified, and pulse electroplating is preferably used; when the second electroplating is performed, normal electroplating is carried out, and then copper reduction processing by grinding is performed.

[0072] Please refer again to Figure 1 and Figure 11 ; Figure 11 is a cross-sectional schematic diagram of a circuit board according to an embodiment of the present invention. Embodiment

[0073] The overall board thickness requirement for the large aspect ratio circuit board 10 of the prior art is 3.3 mm.

[0074] Among them, the prepreg 1020X is formed by combining the standard models of 7628 (thickness 0.175 mm) + 1080 (thickness 0.075 mm) + 7628 (thickness 0.115 mm), with a total thickness of 0.425 mm. There are a total of 4 groups of prepreg 1020X used in the entire circuit board, and the total thickness of the prepreg 1020X is 0.425 mm × 4 = 1.7 mm.

[0075] The copper thickness of the copper clad laminate 1030X is 0.035 mm, and the copper thickness of the surface layer of the circuit board is also 0.035 mm. There are a total of 8 layers of copper in the entire circuit board (including the first copper layer 1010a and the second copper layer 1010b). Therefore, the total copper thickness of the entire circuit board is 0.035 × 8 = 0.28 mm.

[0076] The thickness of the insulating dielectric layer of the copper clad laminate 1030X is 0.3 mm, and there are 3 layers in total. The total thickness of the insulating dielectric layer is 0.3 mm × 3 = 0.9 mm.

[0077] Adding up the total thicknesses of the above materials, the overall board thickness is calculated as: 1.7 mm + 0.28 mm + 0.9 mm = 3.3 mm.

[0078] Calculation of the thickness-diameter ratio: Given that the completed diameter of the hole of the BGA is 0.15 mm, compared with the overall board thickness, the total thickness-diameter ratio is 3.3:0.15 = 22:1.

[0079] This thickness-diameter ratio is relatively large, and the processing difficulty is relatively high.

[0080] The large-thickness-diameter-ratio circuit board 10 of the above prior art is manufactured and calculated according to the manufacturing method of this embodiment.

[0081] Thinning treatment is performed on the prepreg 1020X and the copper clad laminate 1030X: The thickness calculation is as follows: For the thinned prepreg 1020, a thinned prepreg with the standard model of 2116 (thickness 0.115 mm) is selected, and there are 4 layers in total. The total thickness is 0.115 mm × 4 = 0.46 mm.

[0082] For the thinned copper clad laminate, a thinned copper clad laminate with an insulating dielectric layer thickness of 0.2 mm is selected, and there are 3 layers in total. The total thickness of the insulating dielectric layer of the thinned copper clad laminate is 0.2 mm × 3 = 0.6 mm.

[0083] Copper layer: The copper thickness of each layer and the total copper thickness remain unchanged, which is 0.035 mm × 8 = 0.28 mm as described above.

[0084] Adding up the total thicknesses of the above materials, the overall board thickness after thinning is calculated as: 0.6 mm + 0.46 mm + 0.28 mm = 1.34 mm.

[0085] Aspect ratio calculation: Given that the completed hole diameter of the BGA is 0.15 mm, the aspect ratio after thinning is 1.34:0.15 = 8.93:1.

[0086] This aspect ratio is significantly reduced, and the processing difficulty is greatly reduced.

[0087] Furthermore, since the overall board thickness requirement of 3.3 mm cannot be changed, and the board body thickness after thinning is 1.34 mm, the thickness of the thickening layer 40 needs to be 3.3 mm - 1.34 mm = 1.96 mm.

[0088] For the 1.96 mm thickening layer 40, there are three options: (1) A single-sided thinned copper clad laminate with a thickness of 2.0 mm can be selected. After lamination, its thickness is approximately 1.96 mm, achieving the effect of thickening to close to the overall board thickness required by the customer. (2) Thinned prepregs with a standard model of 7628 can be selected, a total of 11 sheets, plus a single layer of copper foil with a thickness of 0.035 mm. The total thickness is: 0.175 mm × 11 + 0.035 mm = 1.96 mm. (3) Thinned prepregs with a standard model of (7628 + 2116 + 7628) can be selected, a total of 4 groups, and then a single thinned prepreg with a standard model of 1080 is set separately, plus a single layer of copper foil with a thickness of 0.035 mm. The overall thickness is (0.175 mm + 0.075 mm + 0.175 mm) × 4 + 0.115 mm + 0.035 mm = 1.97 mm. After lamination, the thickness is approximately equal to 1.96 mm, meeting the overall thickness control and tolerance requirements.

[0089] Please refer to Figure 12 , Figure 12 for Figure 11 the metallographic microscope structure diagram of the physical object.

[0090] It can be seen that the interlayer structure of the large aspect ratio precision hole circuit board formed by this embodiment is well arranged, and the overall structure has good reliability.

[0091] The above are only the preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the protection scope of the present invention.

Claims

1. A manufacturing method of a high-load-bearing precision via hole circuit board with a large thickness-to-diameter ratio, where the maximum thickness-to-diameter ratio of the circuit board is ≥ 12:

1. The circuit board is designed with a forming line. The area within the range of the forming line is the effective area inside the board, and the area outside is the tool area at the board edge. The circuit board is composed of a surface copper layer, a prepreg, and a copper clad laminate, and is characterized in that, The manufacturing method includes the following steps: S10: Thinning the thickness of the prepreg and the insulating dielectric layer of the copper clad laminate to form a thinned prepreg and a thinned copper clad laminate. Making an inner layer circuit pattern on the thinned copper clad laminate, and then following the processing to the lamination process to form a first laminated board; S20: Making a first via hole in the first laminated board, and then making a first surface circuit on one side to form a first sub-board; S30: Making a thickening layer; Stacking the thickening layer and the first sub-board, with the first surface circuit corresponding to the thickening layer, and then performing a second lamination to form a second laminated board; S40: Making a second via hole in the second laminated board, and making a surface circuit. A second surface circuit is formed on the surface of the thickening layer, and the whole board forms the circuit board; The first surface circuit is the same as the second surface circuit; The diameter of the first via hole is smaller than the diameter of the second via hole.

2. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board as described in claim 1, characterized in that, The thinning process is to replace the standard model of the prepreg to form the thinned prepreg, and replace the standard model of the copper clad laminate to form the thinned copper clad laminate, so as to achieve the thinning process.

3. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board as described in claim 1, wherein The thickening layer is a single-sided thinned copper clad laminate or composed of a stack of several thinned prepregs and a single-layer copper foil stacked; The first surface circuit corresponds to the insulating dielectric layer of the single-sided thinned copper clad laminate or to the stacked thinned prepregs; The copper layer of the single-sided thinned copper clad laminate or the single-layer copper foil is made to form the second surface circuit.

4. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board according to claim 1, wherein Forming the first sub-board includes: Filling the first via hole to form a filled board, and then successively grinding and electroplating the filled board, and then making a first surface circuit on the first side to form the first sub-board.

5. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board according to claim 1, characterized in that, The maximum thickness-to-diameter ratio of the first laminated board ≤ 12:

1.

6. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board as described in claim 1, wherein, The second lamination includes, in the stage of cooling during lamination, after cooling the board body to less than or equal to 60 °C, continuing to laminate for 20 min to 30 min.

7. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board according to claim 3, characterized in that, The inner layer circuit pattern includes a target pattern distributed in the board edge tool area and several drilling measurement patterns; A single drilling measurement pattern includes a first drilling measurement pattern, a second drilling measurement pattern to an Nth drilling measurement pattern distributed side by side, and N is greater than or equal to 3; The first drilling measurement pattern, the second drilling measurement pattern to the Nth drilling measurement pattern are each composed of several independent circular patterns with gradually decreasing sizes; Making the second via hole includes, Using an X-ray device to detect the target pattern for positioning, making a positioning hole, and then drilling corresponding to the first drilling measurement pattern with the positioning hole as a reference to form a first measurement hole. Then using an X-ray device to detect and measure the relative position between the first drilling measurement pattern and the first measurement hole, and then adjusting the drilling parameters to form the first drilling parameters; Then make it according to the following steps: S410: Drill the second drilling measurement pattern according to the first drilling parameters to form a second measurement hole, and use an X-ray device to detect and measure the relative position between the second drilling measurement pattern and the second measurement hole, and then adjust the first drilling parameters to form the second drilling parameters; S420: Process according to S410 until drilling the Nth drilling measurement pattern, then process further and form the Nth drilling parameter, and fabricate the second via hole according to the Nth drilling parameter.

8. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board according to claim 7, characterized in that, The sizes of adjacent independent circular patterns among the first drilling measurement pattern, the second drilling measurement pattern to the Nth drilling measurement pattern are the same.

9. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board according to claim 7, characterized in that Cross-shaped etching lines are fabricated at the centers of both the first drilling measurement pattern and the second drilling measurement pattern.

10. The manufacturing method of a high-load-bearing and large thickness-diameter ratio precision via-hole circuit board according to claim 7, characterized in that, The drilling measurement pattern is fabricated on the first surface circuit.

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