A stepped gold finger circuit board with a protective structure

Abstract

This utility model relates to a stepped gold finger circuit board with a protective structure, including a first sub-board and a second sub-board. The first and second sub-boards are connected by stacking and pressing at least two PP layers. One edge of the second sub-board protrudes from the corresponding edge of the first sub-board to form a stepped groove. A gold finger area is provided on the outer side of the stepped groove. A conformal coating is applied to the area between the gold finger area and the first sub-board on the upper surface of the stepped groove. This utility model effectively prevents oxidation and moisture absorption of the circuit and the sub-board substrate by applying a conformal coating in a specific area within the stepped groove. Furthermore, the conformal coating is based on the stepped groove structure formed after pressing, at which point the first and second sub-boards have achieved stable pressing through the PP layers. The conformal coating does not need to undergo the high temperature and high pressure during the pressing process, thus avoiding delamination at the step-gold finger interface.

Description

Technical Field

[0001] This utility model relates to the field of PCB board manufacturing, specifically to a stepped gold finger circuit board with a protective structure. Background Technology

[0002] In the PCB manufacturing industry, stepped gold fingers, as a key structure for realizing electrical connections between circuit modules, are widely used in various electronic terminal products such as communication equipment, consumer electronics, and industrial control. Their performance directly determines the signal transmission stability and service life of the equipment.

[0003] The protection of the stepped gold finger area often employs a process of "pre-coating solder resist ink before lamination": that is, before laminating the sub-boards, solder resist ink is first applied to the stepped area to temporarily protect the gold finger circuitry and the underlying sub-board substrate, and then the sub-board is stacked and laminated with the PP layer and another sub-board to form a multilayer board. However, this process has the following technical defects:

[0004] The chemical compatibility between solder resist ink and PP material used for lamination is poor. Their molecular structures and physical properties are significantly different. During the high-temperature and high-pressure lamination process, the interface between the solder resist ink and the PP layer and the sub-board substrate is prone to micro-gap due to insufficient adhesion, which in turn leads to delamination. The defects of the above-mentioned existing technology directly result in low production yield and insufficient reliability of stepped gold finger circuit boards, making it difficult to meet the requirements of high-end electronic devices for long life and high stability.

[0005] The above problems are worth solving. Utility Model Content

[0006] To address the problem that traditional stepped gold finger circuit boards, which use solder resist ink for protection in the stepped area, are prone to delamination at the step junction due to adhesion failure during the lamination process, this utility model provides a stepped gold finger circuit board with a protective structure.

[0007] The technical solution of this utility model is as follows:

[0008] A stepped gold finger circuit board with a protective structure includes a first sub-board and a second sub-board. The first sub-board and the second sub-board are connected by stacking and pressing at least two PP layers. One side edge of the second sub-board protrudes from the corresponding edge of the first sub-board to form a stepped groove. A gold finger area is provided on the outer side of the stepped groove. A conformal coating is provided on the upper surface of the stepped groove between the gold finger area and the first sub-board. The conformal coating is used to cover and protect the sub-board substrate and the circuit connecting the gold fingers below.

[0009] As a preferred embodiment of this utility model, the PP layer adjacent to the second sub-board has a 0.2mm gap with the edge of the stepped groove.

[0010] As a preferred technical solution of this utility model, the gold finger area includes at least one of ordinary gold fingers, graded gold fingers, or long and short gold fingers.

[0011] As a preferred embodiment of this utility model, the conformal coating covers the sidewall of the first sub-plate.

[0012] As a preferred technical solution of this utility model, the thickness of the conformal coating is not less than 15 μm.

[0013] As a preferred embodiment of this utility model, both the first sub-board and the second sub-board are bare core boards, or both the first sub-board and the second sub-board are core boards with at least one layer of PP and copper foil laminated on them.

[0014] As a preferred technical solution of this utility model, the first sub-board and the second sub-board are provided with through holes or blind holes that connect the two, and the through holes or blind holes are provided with copper plating layers.

[0015] As a preferred embodiment of this utility model, the through hole or blind hole is filled with resin.

[0016] The advantages of this utility model based on the above solution are as follows:

[0017] This invention uses a conformal coating applied to a specific area within the stepped groove to cover and protect the underlying sub-board substrate and the circuitry connecting the gold fingers. This effectively prevents oxidation and moisture absorption of the circuitry and the sub-board substrate. This invention eliminates the need for traditional solder resist inks, and the conformal coating is based on the stepped groove structure formed after lamination. At this point, the first and second sub-boards have been stably laminated through the PP layer. The conformal coating does not need to undergo the high temperature and pressure during the lamination process, thus avoiding delamination at the interface between the stepped gold fingers. While ensuring the functionality of the gold fingers, this significantly improves the structural stability and service life of the circuit board. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of this utility model;

[0019] Figure 2 This is a top-view diagram of the stepped groove section.

[0020] In the diagram,

[0021] 1. First sub-board; 2. Second sub-board; 3. Step groove; 4. PP layer; 5. Gold finger area; 6. Conformal coating. Detailed Implementation

[0022] To better understand the purpose, technical solution, and technical effects of this utility model, the following description, in conjunction with the accompanying drawings and embodiments, will provide further explanation. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need further definition and explanation in subsequent drawings. It is also stated that the embodiments described below are only for explaining this utility model and are not intended to limit it.

[0023] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is referred to as "connected to" another component, it can be directly connected to the other component or there may be an intermediate component.

[0024] The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product is usually placed when in use, or the orientation or positional relationship in which a person skilled in the art would normally understand it, or the orientation or positional relationship in which the product is usually placed when in use. It is only for the purpose of facilitating the description of this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0025] The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or specifying the number of technical features. “Several” means two or more, unless otherwise expressly and specifically defined.

[0026] like Figure 1 and Figure 2 As shown, a stepped gold finger circuit board with a protective structure includes a first sub-board 1 and a second sub-board 2. The first sub-board 1 and the second sub-board 2 are connected by stacking and pressing at least two PP layers 4. One side edge of the second sub-board 2 protrudes from the corresponding edge of the first sub-board 1 to form a stepped groove 3. A gold finger area 5 is provided on the outer side of the stepped groove 3. A conformal coating 6 is provided on the area between the gold finger area 5 on the upper surface of the stepped groove 3 and the first sub-board 1. The conformal coating 6 is used to cover and protect the sub-board substrate and the circuit connecting the gold fingers below, effectively solving the delamination problem caused by poor compatibility between solder resist ink and PP layer in traditional stepped gold finger circuit boards.

[0027] From the structural design of this utility model, the step groove 3 formed by the protrusion of the edge of the second sub-plate 2 from the first sub-plate 1 provides an independent installation space for the gold finger area 5. The conformal coating 6 covers a specific area on the upper surface of the step groove 3, and directly corresponds to the sub-plate substrate and the circuit connecting the gold fingers below it. This structural design eliminates the need for the conformal coating 6 to be pre-coated before pressing, but rather to be coated based on the stable structure formed after pressing. This avoids direct contact with the PP layer 4 under high temperature and high pressure, fundamentally eliminating the bonding failure and stress concentration problems caused by poor material compatibility, and preventing delamination in the step junction area.

[0028] Meanwhile, the conformal coating 6, as an insulating protective layer, can adhere tightly to the surface of the stepped groove 3 to form a continuous protective film, effectively blocking water vapor, oxygen and other corrosive substances from eroding the sub-board substrate and circuits, reducing circuit oxidation and substrate moisture absorption, and significantly improving the structural stability and service life of the circuit board while ensuring that the conductivity of the gold finger area 5 is not affected.

[0029] In this invention, the PP layer 4 adjacent to the second sub-board 2 is spaced d with respect to the edge of the stepped groove 3, where d = 0.2 mm. This spacing refers to the fact that when the first sub-board 1 and the second sub-board 2 are stacked and pressed together, the edge of the PP layer 4 near the second sub-board 2 is recessed by 0.2 mm relative to the final processed edge of the stepped groove 3. This ensures that even if the PP layer 4 slightly softens or flows during the high-temperature and high-pressure pressing process, it will not overflow or flow onto the surface of the area where the stepped groove 3 is located. By reserving a 0.2 mm margin, the edge overflow problem caused by the material flow characteristics of the PP layer 4 tightly attached to the second sub-board 2 during pressing is avoided, ensuring that the stepped groove 3 area remains a clean substrate surface after pressing. On the other hand, this spacing physically isolates the PP layer 4 from the edge of the stepped groove 3, reducing stress concentration in the step junction area caused by material compression during pressing, further enhancing the bonding stability between the first sub-board 1 and the second sub-board 2. Combined with the protection of the stepped groove 3 by the conformal coating 6, this provides double protection for the circuit board's anti-delamination ability and reliability during long-term use from a structural perspective.

[0030] In a preferred embodiment, the conformal coating 6 covers the bottom of the sidewall of the first sub-board 1. This embodiment extends the protective area of ​​the conformal coating 6 from the upper surface of the stepped groove 3 to the vertical sidewall, forming a three-dimensional protective structure for the exposed substrate and circuitry around the stepped groove 3. The bottom of the sidewall of the first sub-board 1, as the interface between the stepped groove 3 and the sub-board substrate, is directly exposed to the external environment and easily accumulates moisture and impurities, making it a high-risk area for circuit oxidation and substrate corrosion. In this case, the conformal coating 6 is applied from top to bottom along the sidewall of the first sub-board 1 to a specific height, such as 0.3-0.5 mm, effectively preventing external corrosive substances from penetrating into the sub-board, especially protecting the interface between the bottom of the sidewall of the first sub-board 1 and the PP laminate.

[0031] In one specific embodiment, the thickness of the conformal coating 6 is not less than 15 μm, ensuring that the conformal coating 6 can form a sufficient film thickness so that the conformal coating 6 can fully cover the fine gaps of complex structures such as the upper surface and bottom of the side wall of the stepped groove 3. Especially in the step junction area between the first sub-plate 1 and the second sub-plate 2, the uniform thickness of the protective layer fills the micro-defects at the interface, further enhancing the structural sealing and resistance to environmental erosion in this area.

[0032] In this invention, the gold finger area 5 can adopt various structural forms. It can be a regular gold finger with uniform length and height, a graded gold finger with stepped height distribution, or a gold finger of different lengths. One or more of these can be selected and combined according to actual needs.

[0033] In this utility model, the structure of the first sub-board 1 and the second sub-board 2 can be either a bare core board without additional PP layer 4 and copper foil lamination, or a composite core board with at least one layer of PP material and copper foil already laminated on the core board. The appropriate sub-board structure can be selected according to the number of layers and functional requirements of the circuit board.

[0034] In this utility model, the first sub-board 1 and the second sub-board 2 are processed with through holes (not shown in the figure) that penetrate through both of them, or blind holes (not shown in the figure) that extend from the surface of one sub-board to the interior of the other sub-board. The inner walls of the through holes or blind holes are plated with copper layers. The electrical connection between the first sub-board 1 and the second sub-board 2 is realized by utilizing the conductivity of copper.

[0035] In addition to the copper plating layer on the inner wall, the inside of the through hole or blind hole is filled with resin material. This does not affect the electrical connection function achieved by the copper plating layer, and the resin filling can enhance the structural strength of the hole, preventing deformation or damage to the through hole or blind hole due to its own hollow structure during subsequent processing or use.

[0036] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] The above embodiments only illustrate several implementation methods of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A stepped gold finger circuit board having a protective structure, characterized by, The device includes a first sub-board and a second sub-board. The first sub-board and the second sub-board are connected by stacking and pressing at least two PP layers. One side edge of the second sub-board protrudes from the corresponding edge of the first sub-board to form a stepped groove. A gold finger area is provided on the outer side of the stepped groove. A conformal coating is provided on the area between the gold finger area on the upper surface of the stepped groove and the first sub-board. The conformal coating is used to cover and protect the sub-board substrate and the circuit connecting the gold fingers below.

2. The stepped gold finger printed circuit board with a protective structure according to claim 1, wherein, The PP layer adjacent to the second sub-board has a 0.2mm gap with the edge of the stepped groove.

3. The stepped gold finger printed circuit board with a protective structure according to claim 1, wherein, The gold finger area includes at least one of ordinary gold fingers, graded gold fingers, or long and short gold fingers.

4. The stepped gold finger printed circuit board with a protective structure according to claim 1, wherein, The conformal coating extends to the bottom of the sidewall of the first sub-board.

5. The stepped gold finger printed circuit board with a protective structure according to claim 1, wherein, The thickness of the conformal coating is not less than 15 μm.

6. A stepped gold finger circuit board with a protective structure according to claim 1, characterized in that, Both the first sub-board and the second sub-board are bare core boards, or both the first sub-board and the second sub-board are core boards with at least one layer of PP and copper foil laminated on them.

7. The stepped gold finger printed circuit board with a protective structure according to claim 1, wherein, The first and second sub-boards are provided with through holes or blind holes that connect the two, and the through holes or blind holes are provided with copper plating layers.

8. The stepped gold finger printed circuit board having a protective structure according to claim 7, wherein, The through holes or blind holes are filled with resin.

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