PCB manufacturing method suitable for local crimping blind hole design and PCB

Abstract

The invention discloses a PCB manufacturing method suitable for local crimping blind hole design and a PCB, and belongs to the technical field of printed circuit boards, and the manufacturing method comprises the steps: carrying out the pretreatment of a daughter board: forming a through hole in the daughter board, and enabling the hole diameter of the through hole to be larger than the designed hole diameter of a finished crimping blind hole; electroplating treatment: electroplating the daughter board, and forming a copper layer on the hole wall of the through hole; filling treatment, wherein the through holes are filled with copper paste; pressing treatment: pressing the daughter board and a preset laminated material into a mother board, and synchronously sintering the copper paste at high pressing temperature in the pressing process; and drilling treatment, including positioning the through hole in the mother board and performing deep drilling to form the crimping blind hole. Through innovative daughter board pre-drilling, copper paste filling and mother board deep drilling processes, the problems of poor hole site precision, liquid medicine residues, insufficient hole copper and the like in the prior art are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board technology, and in particular to a PCB manufacturing method and PCB suitable for partial press-fit blind via design. Background Technology

[0002] As electronic products develop towards higher density and higher precision, PCB crimp-fit ​​blind via technology faces severe challenges. Existing technologies for manufacturing crimp-fit ​​blind vias suffer from the following prominent problems: Differences in hole position accuracy: In traditional processes, the processing of blind holes and through holes requires multiple pressing and drilling operations. Due to the misalignment of the blind hole and through hole alignment systems, hole position offset is difficult to control.

[0003] Insufficient copper in the hole: For this type of crimped blind hole product, due to its high thickness-to-diameter ratio, traditional blind hole plating processes are difficult to meet its copper requirements. If the process involves filling the hole with thick copper-plated resin and then drilling, insufficient copper in the hole may occur due to the hole position plate. This is especially true for some power connectors, where excessively thin copper in the hole can lead to high single-point resistance and overheating, affecting the reliability of the electrical connection.

[0004] Chemical residue: Due to the complex structure of blind holes, chemical residues inside are difficult to clean thoroughly, easily leading to oxidation and corrosion, and reducing product lifespan. For example, in traditional electroplating processes, resin residue easily remains at the bottom of blind holes, causing cracks at high temperatures.

[0005] Existing solutions such as laser drilling and back drilling can partially improve the problem, but they still have drawbacks such as blind spots in processing or insufficient precision. For example, the problem of residual resin on the hole wall caused by back drilling deviation is a concern. Laser drilling equipment can only clean the bottom of the hole, but cannot clean the resin on the hole wall, which poses a risk of hole wall insulation. Therefore, there is an urgent need for a manufacturing method to solve the above pain points. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a PCB manufacturing method and PCB suitable for local crimping blind via design. By filling the blind via area that needs to be crimped with copper paste and combining it with the motherboard deep drilling process, the hole position accuracy of the blind via is significantly improved, the risk of chemical residue in the blind via is eliminated, and sufficient copper in the blind via is ensured.

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a PCB manufacturing method suitable for partial press-fit blind via design, comprising: Sub-plate pretreatment includes opening through holes on the sub-plate, wherein the diameter of the through holes is larger than the design diameter of the finished crimped blind holes; Electroplating process, including electroplating the sub-board to form a copper layer on the wall of the through hole; The filling process includes filling the through holes with copper paste; The pressing process includes pressing the sub-board and the preset laminating material into a master board, and simultaneously sintering the copper paste at high pressing temperature during the pressing process; The drilling process includes locating the through hole on the motherboard and performing deep drilling to form a crimped blind hole.

[0008] Optionally, the diameter of the through hole is greater than or equal to the design diameter of the finished crimped blind hole by 0.1 mm to 0.3 mm.

[0009] Optionally, the copper layer formed by the electroplating process has a thickness greater than or equal to 10 μm and a uniformity deviation of less than or equal to ±5%.

[0010] Optionally, filling the through hole with copper paste includes: Choose an electrical conductivity greater than or equal to 1.0 × 10⁻⁶. 6 The conductive copper paste with a density of S / m is used to fill the through-holes via a screen printing process.

[0011] Optionally, the conductive copper paste is a transient liquid-phase sintered copper paste.

[0012] Optionally, the copper paste filling of the through hole further includes using a vacuum degassing device to ensure that the through hole is completely filled without any gaps.

[0013] Optionally, the step of locating the through hole on the mother plate and performing deep drilling to form a crimping blind hole includes: The position of the through hole is captured by a CCD optical imaging system. According to the location, the through hole is drilled to a depth using the G83 pecking cycle method, with a step-by-step drilling depth ratio of 10%-40%, forming a crimped blind hole.

[0014] Optionally, the simultaneous sintering of the copper paste at high pressing temperature during the pressing process satisfies the following: The sintering temperature is 200℃ to 350℃, the pressure is 2MPa to 15MPa, and the time is 1min to 30min.

[0015] Optionally, the PCB manufacturing method further includes: Before lamination, the sub-board is patterned according to design requirements; After lamination, the motherboard is drilled, electroplated, and etched according to design requirements. After drilling, the motherboard undergoes surface treatment to obtain the final PCB.

[0016] Secondly, the present invention provides a PCB with press-fit blind vias, which is manufactured using the PCB manufacturing method described above.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention provides a PCB manufacturing method and PCB suitable for partial press-fit blind via design. Through innovative sub-board pre-drilling, copper paste filling, and deep drilling of the motherboard, it effectively solves problems such as poor hole position accuracy, chemical residue, and insufficient copper in existing technologies. For example, by gripping the through-holes of the motherboard for positioning, the accuracy of blind and through-hole positions is ensured, solving the problem of deviation in the through-hole / blind-hole positioning system; copper paste filling completely seals the blind vias, preventing chemical entry and eliminating chemical residue; the conductivity of the copper paste sintering layer is close to that of electroplated copper, and the entire hole is completely filled with copper paste. Within the back-drilling offset range, there will be no problem of insufficient copper, resolving reliability risks and ensuring sufficient and reliable copper in the holes; there is no problem of resin residue on the hole walls, eliminating the need for additional laser drilling equipment for cleaning residue inside the holes. This method is applicable to HDI boards, automotive electronics, communication equipment, and other fields, significantly improving PCB reliability and production efficiency, and has broad industrial application prospects. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a PCB manufacturing method for partial press-fit blind via design provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the sub-board before preprocessing provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the pre-processed sub-board provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the electroplated sub-board provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the sub-plate after filling treatment provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the sub-board after graphic processing provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the mother plate obtained after the pressing process provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the motherboard after drilling, provided in an embodiment of the present invention. Figure 9 This is a schematic diagram of the electroplated motherboard after processing, provided in an embodiment of the present invention. Figure 10 This is a schematic diagram of the motherboard after image etching, provided in an embodiment of the present invention. Figure 11 This is a schematic diagram of a mother plate for forming a crimped blind hole through drilling, as provided in an embodiment of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0021] Example 1:

[0022] like Figure 1 As shown, this invention provides a PCB manufacturing method suitable for partial press-fit blind via design, including the following steps: 1. Sub-plate pretreatment, including opening through holes on the sub-plate, the diameter of which is larger than the design diameter of the blind hole for crimping in the finished product.

[0023] The through-holes here specifically refer to holes prepared for subsequent crimping of blind holes. For ease of distinction, conventional blind holes opened in the original processing steps are referred to as second through-holes, and the opening of second through-holes is completed simultaneously during the sub-board pretreatment process. For example... Figure 2 and Figure 3 The image shows a schematic diagram of the sub-board before and after preprocessing.

[0024] Specifically, in this embodiment, the diameter of the through hole is greater than or equal to the designed diameter of the finished crimped blind hole by 0.1 mm to 0.3 mm. For example, when the diameter of the finished crimped blind hole is 0.6 mm, the diameter of the through hole is 0.9 mm.

[0025] 2. Electroplating treatment, including electroplating the sub-board to form a copper layer on the hole wall of the through hole.

[0026] Specifically, in this embodiment, the copper layer formed by electroplating has a thickness greater than or equal to 10 μm and a uniformity deviation of less than or equal to ±5%, which meets the conductivity requirements.

[0027] like Figure 4 As shown, the electroplating process not only forms a copper layer on the wall of the through hole, but also forms a copper layer on the wall of the second through hole.

[0028] 3. Filling treatment, including filling the through holes with copper paste.

[0029] Specifically, in this embodiment, filling the through hole with copper paste includes: Choose an electrical conductivity greater than or equal to 1.0 × 10⁻⁶. 6The conductive copper paste with a strength of S / m is used to fill the through-holes through a screen printing process, while a vacuum degassing device is used to ensure that the through-holes are completely filled without any gaps.

[0030] Conductive copper paste, such as transient liquid-phase sintered copper paste, contains nano-sized copper particles (d90=400nm, d10=150nm) and micron-sized copper particles, with a conductivity close to that of electroplated copper (1.68×10⁻⁶). -6 Ω·cm).

[0031] like Figure 5 As shown, the filling process not only fills the through-hole with copper paste, but also plugs the second through-hole with resin.

[0032] 4. Sub-board pattern processing, including pattern etching of the sub-board according to design requirements.

[0033] like Figure 6 The image shown is a schematic diagram of the sub-board after graphic processing.

[0034] 5. Pressing process, including pressing the sub-board and the preset laminating material into a master board, and simultaneously sintering the copper paste through high pressing temperature during the pressing process.

[0035] The pre-installed laminating material is usually a prepreg. Since there is already copper paste inside the through-hole, there will be no problem of prepreg flowing into the hole; therefore, a normal prepreg can be used to solve the limitation of conventional low-flow prepreg.

[0036] Specifically, in this embodiment, the copper paste is simultaneously sintered at high temperature during the pressing process to achieve the following: The sintering temperature is 200℃ to 350℃, the pressure is 2MPa to 15MPa, and the time is 1min to 30min.

[0037] like Figure 7 The image shown is a schematic diagram of the motherboard obtained after the pressing process.

[0038] 6. Motherboard processing, including drilling, electroplating and pattern etching of the motherboard according to design requirements, to ensure the accuracy of the outer layer circuitry.

[0039] like Figures 8 to 10 The diagram shows the motherboard after drilling, electroplating, and image etching.

[0040] 7. Drilling process, including positioning through holes on the motherboard and drilling deep holes to form crimping blind holes.

[0041] Specifically, in this embodiment, positioning through holes on the motherboard and drilling deep holes to form crimping blind holes includes: The location of the through hole is captured by a CCD optical imaging system. Depending on the location, the through hole is drilled to a depth using a G83 pecking cycle method (CNC drilling machine), with a step-by-step drilling depth ratio of 10%-40%, forming a crimped blind hole.

[0042] The positioning accuracy requirement is less than or equal to ±0.03mm, and the drilling depth error requirement is less than or equal to ±0.01mm.

[0043] like Figure 11 The diagram shown is a schematic of a motherboard with a drilled hole forming a crimped blind hole.

[0044] 8. Surface treatment, including surface treatment of the motherboard to obtain the final PCB.

[0045] Taking a 28-layer blind hole plate as an example, the implementation process of the present invention will be described in detail: (1) Core board fabrication: Core board material: EM892K substrate, thickness 0.1mm.

[0046] Core board graphic fabrication: Using laser DI equipment, the graphic is transferred to the core board according to the design data.

[0047] (2) Sub-board making: Lamination process: According to the design requirements, the core board and P-sheet are placed in sequence and then laminated and pressed together.

[0048] Drilling parameters: Drill bit speed 80kr / min, feed rate 20mm / s.

[0049] Electroplating: Acidic copper sulfate system, current density 2A / dm², copper thickness 18μm, uniformity deviation ±3%.

[0050] Resin plugging: Thermosetting resin is selected, and vacuum brushing is performed. The plugging depth is <15um.

[0051] (3) Copper paste filling: Copper paste selection: TLPS nano copper paste (Heraeus C100 series), with a conductivity of 1.8×10^6 S / m and a nanoparticle content of 30%.

[0052] Printing parameters: screen thickness 120μm, squeegee pressure 3N / cm, speed 50mm / s. Vacuum degassing is performed after filling to ensure no pores.

[0053] Sintering: Temperature 220℃, pressure 8MPa, time 5 minutes, nitrogen protection. After sintering, the copper paste shrinkage rate is <5%, and the bond strength is 32MPa.

[0054] (4) Mother plate pressing: Lamination: lamination temperature 180℃, pressure 4MPa, time 60 minutes. Positioning pins and CCD optical alignment are used, and interlayer misalignment is ≤±0.015mm.

[0055] (5) Mother plate processing: Drilling: Outer layer through hole diameter 0.5mm, positioning accuracy ±0.02mm.

[0056] plating.

[0057] Graphic design.

[0058] (6) Depth drilling: Positioning system: CCD optical imagery is used to capture the center coordinates of the through-hole, and the blind hole position is determined after compensation for deviation. Positioning accuracy is ±0.018mm.

[0059] Drilling parameters: target depth 1.2mm, G83 cycle, step drilling depth (30%, 60%, 100%), coolant pressure 6MPa, rotation speed 50kr / min, feed rate 36mm / s. Hole wall roughness Ra≤2μm after drilling.

[0060] Example 2:

[0061] This invention provides a PCB with press-fit blind vias, manufactured using the PCB fabrication method described in Embodiment 1 above. This PCB possesses the beneficial effects of the printed circuit board fabrication methods described in any of the embodiments of this invention, which will not be elaborated further here.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A PCB fabrication method suitable for partial press-fit blind via design, characterized in that, include: Sub-plate pretreatment includes opening through holes on the sub-plate, wherein the diameter of the through holes is larger than the design diameter of the finished crimped blind holes; Electroplating process, including electroplating the sub-board to form a copper layer on the wall of the through hole; The filling process includes filling the through holes with copper paste; The pressing process includes pressing the sub-board and the preset laminating material into a master board, and simultaneously sintering the copper paste at high pressing temperature during the pressing process; The drilling process includes locating the through hole on the motherboard and performing deep drilling to form a crimped blind hole.

2. The PCB fabrication method for partial press-fit blind via design according to claim 1, characterized in that, The diameter of the through hole is greater than or equal to the design diameter of the finished crimped blind hole by 0.1 mm to 0.3 mm.

3. The PCB fabrication method for partial press-fit blind via design according to claim 1, characterized in that, The copper layer formed by the electroplating process has a thickness greater than or equal to 10 μm and a uniformity deviation of less than or equal to ±5%.

4. The PCB fabrication method for partial press-fit blind via design according to claim 1, characterized in that, The process of filling the through hole with copper paste includes: Choose an electrical conductivity greater than or equal to 1.0 × 10⁻⁶. 6 The conductive copper paste with a density of S / m is used to fill the through-holes via a screen printing process.

5. The PCB fabrication method for partial press-fit blind via design according to claim 4, characterized in that, The conductive copper paste is a transient liquid-phase sintered copper paste.

6. The PCB fabrication method for partial press-fit blind via design according to claim 4, characterized in that, The copper paste filling of the through hole also includes using a vacuum degassing device to ensure that the through hole is completely filled without any gaps.

7. The PCB fabrication method for partial press-fit blind via design according to claim 1, characterized in that, The step of locating the through hole on the mother plate and drilling a deep hole to form a crimping blind hole includes: The position of the through hole is captured by a CCD optical imaging system. According to the location, the through hole is drilled to a depth using the G83 pecking cycle method, with a step-by-step drilling depth ratio of 10%-40%, forming a crimped blind hole.

8. The PCB fabrication method for partial press-fit blind via design according to claim 1, characterized in that, The copper paste is simultaneously sintered at high temperature during the pressing process to achieve the following: The sintering temperature is 200℃ to 350℃, the pressure is 2MPa to 15MPa, and the time is 1min to 30min.

9. The PCB fabrication method for partial press-fit blind via design according to claim 1, characterized in that, The PCB manufacturing method also includes: Before lamination, the sub-board is patterned according to design requirements; After lamination, the motherboard is drilled, electroplated, and etched according to design requirements. After drilling, the motherboard undergoes surface treatment to obtain the final PCB.

10. A PCB with press-fit blind vias, characterized in that, It is manufactured using the PCB manufacturing method described in any one of claims 1-9.

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