A multilayer circuit board with a depth-controlled drilling interconnection structure with air guide holes

Abstract

This utility model relates to a multilayer circuit board with a controlled-depth drilling interconnect structure featuring vent holes. The board comprises multiple stacked circuit layers and has a first and second surface layer arranged opposite each other. The multilayer circuit board includes mechanical blind vias and vent holes. The mechanical blind vias penetrate from the first surface layer to a predetermined Nth layer and extend into a predetermined depth of the N+1th layer. The vent holes penetrate from the second surface layer to the mechanical blind vias, with a diameter smaller than that of the mechanical blind vias, and the center of the vent hole is offset from the center of the mechanical blind vias by a predetermined amount. The walls of both the mechanical blind vias and the vent holes are covered with an electroplated layer. This utility model, by adding a vent hole below the controlled-depth drilling mechanical blind vias, improves the flow of plating solution during electroplating of the mechanical blind vias. This allows for the completion of the stacked structure in a single lamination process within the multilayer circuit board, eliminating the need for additional copper paste for plugging, thus shortening the processing cycle and saving manufacturing costs.

Description

Technical Field

[0001] This utility model relates to the field of circuit board processing technology, specifically to a multilayer circuit board with a deep drilling interconnection structure with air guide holes. Background Technology

[0002] In high-multilayer PCB interconnection technology, the traditional solution for interconnecting specified layers involves two lamination processes. Taking a 48L (layer) product as an example, to achieve conductivity between layers 1-48L and 1-10L, the specific steps are as follows: For the conductivity requirement of 1-10L, the 1-10L circuit layers are first laminated to form a preliminary stacked structure. After lamination, mechanical drilling is performed on this structure to open the connection channels between layers 1-10L. Subsequently, an electroplating process is used to form a conductive plating layer inside the holes, achieving conductivity between 1-10L. Then, to meet the conductivity requirement of 1-48L, the structure with completed 1-10L conductivity is laminated a second time with the 11-48L circuit layers to form an overall 1-48L stacked structure. After lamination, mechanical drilling is performed again to open the connection channels between layers 1-48L, and another electroplating process is used to form a conductive plating layer inside the holes, ultimately achieving conductivity between 1-48L. It is evident that this traditional solution requires two lamination, two drilling, and two electroplating processes, which greatly prolongs the PCB manufacturing process, leading to a significant increase in processing costs and hindering delivery time, thus failing to meet the demand for rapid delivery. In addition, the copper thickness uniformity of the L1 layer decreases due to the two electroplating processes.

[0003] To address these shortcomings, researchers attempted a combination of one-time lamination, controlled-depth drilling, and copper paste filling. For the same 48L product, all circuit layers from 1 to 48L were first laminated in one step to form a complete stacked structure. After lamination, through-holes were machined using controlled-depth drilling. For the conductivity requirements of layers 1-10L, controlled-depth drilling was required to penetrate all layers, while conductivity for layers 1-48L was achieved using conventional through-hole machining. However, due to the limited internal space of the mechanically blind vias in layers 1-10L, the electroplating solution flow was impeded, resulting in insufficient copper thickness in the vias. This necessitated the use of copper paste to address the insufficient copper thickness, undoubtedly increasing the cost of copper paste filling. Furthermore, copper paste is expensive, costing up to 5000 RMB / 500g, thus this solution has poor cost advantages. Utility Model Content

[0004] To address the problem of substandard copper plating in existing one-step pressing and controlled-depth drilling combined with copper paste plugging processes, which suffer from poor flow of electroplating solution in mechanical blind holes and require the use of high-cost copper paste for plugging, this invention provides a multilayer circuit board with a controlled-depth drilling interconnect structure featuring venting holes.

[0005] The technical solution of this utility model is as follows:

[0006] A multilayer circuit board with a deep drilling interconnect structure with air guide holes is composed of multiple circuit layers stacked together and has a first surface layer and a second surface layer arranged opposite to each other. The multilayer circuit board is provided with mechanical blind holes and air guide holes. The mechanical blind holes penetrate from the first surface layer to a preset Nth layer and extend into a preset depth of the N+1th layer. The mechanical blind holes have a first aperture, where N is a positive integer.

[0007] The air guide hole extends from the second surface layer to the mechanical blind hole. The air guide hole has a second aperture, which is smaller than the first aperture. The center of the air guide hole is offset from the center of the mechanical blind hole by a predetermined amount.

[0008] The walls of both the mechanical blind hole and the air guide hole are covered with an electroplated layer.

[0009] As a preferred embodiment of this utility model, the second diameter of the air guide hole is 0.5 mm smaller than the first diameter of the mechanical blind hole.

[0010] As a preferred embodiment of this utility model, the first diameter of the mechanical blind hole is greater than 0.6 mm.

[0011] As a preferred embodiment of this utility model, the second diameter of the air guide hole is 0.15mm.

[0012] As a preferred technical solution of this utility model, the mechanical blind hole extends into the N+1th layer to a preset depth of 4mil.

[0013] As a preferred embodiment of this utility model, the center of the air guide hole and the center of the mechanical blind hole are offset by a preset amount greater than 0.3mm.

[0014] The advantages of this utility model based on the above solution are as follows:

[0015] This invention provides mechanical blind holes and vent holes in a first and second surface layer respectively. The mechanical blind holes penetrate from the first surface layer to a predetermined Nth layer and extend into a predetermined depth in the N+1th layer. The vent holes penetrate from the second surface layer to the mechanical blind holes and have a smaller diameter than the mechanical blind holes. The center of each vent hole is offset from the mechanical blind holes by a predetermined amount. The walls of both vent holes are covered with an electroplated layer. Thus, the addition of vent holes can improve the flow of the plating solution during the electroplating of the mechanical blind holes and solve the problem of insufficient copper in the holes caused by poor plating solution flow in traditional mechanical blind holes.

[0016] In addition, by adopting the air guide hole structure of this utility model, the reliance on an additional copper paste plugging structure can be eliminated to achieve one-time lamination of multilayer boards, which helps to shorten the processing cycle. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of this utility model;

[0018] Figure 2 for Figure 1 Enlarged view of section A.

[0019] In the diagram,

[0020] 1. Through hole; 2. Mechanical blind hole; 3. Vent hole; 4. Electroplating layer. Detailed Implementation

[0021] 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.

[0022] 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.

[0023] 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.

[0024] like Figure 1 and Figure 2 As shown, a multilayer circuit board with a vented through-hole controlled deep drilling interconnect structure is illustrated. Taking a 48-layer (L1-L48) high-multilayer PCB as an example, it is necessary to achieve conductivity between layers L1-L48 and L1-L10. This multilayer circuit board is formed by laminating 48 circuit layers in one step, where L1 is the first surface layer and L48 is the second surface layer. In this multilayer circuit board, via 1 is a conductive structure that penetrates the entire L1-L48 layers, and mechanical blind via 2 penetrates from the first surface layer (L1) to the preset 10th layer (L10) and extends into the 11th layer (L11). Here, N equals 10, N+1 equals 11, and the preset depth can be 4mil, ensuring that it does not penetrate the 11th layer.

[0025] In this invention, the vent 3 is drilled from the second surface layer (L48) toward the mechanical blind hole 2 until it penetrates into the mechanical blind hole 2, forming a connecting channel; and the center of the vent 3 is offset from the center of the mechanical blind hole 2 by a preset amount. Through the guiding effect of the vent 3, the mechanical blind hole 2 can, like the through hole 1, allow the electroplating solution to flow smoothly into the mechanical blind hole 2, ensuring that the electroplating layer 4 on the hole wall is uniformly covered, thus meeting the conductivity and reliability requirements without the need to fill the mechanical blind hole 2 with additional copper paste, achieving conductive interconnection of layers L1-L10 and L1-L48.

[0026] As can be seen, the multilayer circuit board of this utility model can be laminated into an integral stacked structure in one step, reducing the number of laminations. Then, on the basis of the integral stacked structure, the through holes 1 and mechanical blind holes 2 are electroplated simultaneously. The pre-processed air guide holes 3 ensure the smooth flow of electroplating solution in the mechanical blind holes 2, ensuring that the hole walls of the mechanical blind holes 2 can form a uniform and qualified electroplating layer 4, without the need for additional copper paste plugging process.

[0027] The second aperture of the vent 3 is 0.5 mm smaller than the first aperture of the mechanical blind via 2. On the one hand, the smaller aperture of the vent 3 ensures that the vent 3 has sufficient space to guide the electroplating solution into the mechanical blind via 2, improving the solution flow and ensuring uniform coverage of the electroplating layer 4 on the via wall. On the other hand, the 0.5 mm difference creates a reasonable size difference between the vent 3 and the mechanical blind via 2. This avoids a decrease in the strength of the via wall due to their similar sizes, and also prevents the vent 3 from weakening its drainage effect due to a large size difference. Thus, while ensuring the electroplating quality of the mechanical blind via 2, the overall compactness and stability of the circuit board structure are also taken into account.

[0028] In one optional embodiment, the first diameter of the mechanical blind via 2 is greater than 0.6 mm. The second diameter of the vent 3 is 0.15 mm. The larger diameter provides a more relaxed process window for the machining of the mechanical blind via 2, facilitating precise control of the drilling depth by the depth-controlled drilling equipment, reducing the risk of drill bit deviation or breakage due to insufficient diameter, and improving the yield of the drilling process. At the same time, a diameter greater than 0.6 mm provides sufficient flow space for the electroplating solution, avoiding solution stagnation or bubble accumulation due to narrow channels, ensuring that all areas of the hole wall can fully contact the electroplating solution, thereby forming a uniform and complete electroplating layer 4. The 0.15 mm diameter, while fulfilling the venting function, has minimal impact on the circuit layout of the second surface layer (L48 layer) of the circuit board, making it particularly suitable for the fine design requirements of high-density circuit boards.

[0029] In an optional embodiment, the preset offset between the center of the vent hole 3 and the center of the mechanical blind hole 2 is greater than 0.3mm. This ensures that the vent hole 3 and the mechanical blind hole 2 maintain a reasonable spatial distance, avoiding structural overlap or local thinning of the hole walls due to excessive proximity, thereby improving the integrity of the hole walls during drilling. At the same time, sufficient offset can prevent current interference caused by excessive proximity of the electroplated layers 4 of the two holes during electroplating, avoiding problems such as abnormal local copper thickness or short circuits between holes.

[0030] In summary, this invention, through the structure of controlled-depth drilling of mechanical blind holes and venting holes, enables the formation of a multilayer circuit board with only one lamination. With the specific size of the mechanical blind holes and venting holes, and the setting of a center offset of more than 0.3mm, it not only solves the problems of long process, high cost, and uneven copper thickness in the traditional two-lamination scheme, but also overcomes the defects of poor flow of electroplating solution in mechanical blind holes and the need to rely on expensive copper paste to plug the holes in a single lamination.

[0031] 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.

[0032] 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 multi-layer wiring board having a via interconnection structure with a depth controlled air hole, which is formed by stacking a plurality of wiring layers and has a first surface layer and a second surface layer disposed opposite to each other, characterized in that, The multilayer circuit board is provided with mechanical blind vias and vent holes. The mechanical blind vias penetrate from the first surface layer to a preset Nth layer and extend into a preset depth of the N+1th layer. The mechanical blind vias have a first aperture, where N is a positive integer. The air guide hole extends from the second surface layer to the mechanical blind hole. The air guide hole has a second aperture, which is smaller than the first aperture. The center of the air guide hole is offset from the center of the mechanical blind hole by a predetermined amount. The walls of both the mechanical blind hole and the air guide hole are covered with an electroplated layer.

2. The multilayer circuit board with a deep drilling interconnect structure and air guide hole as described in claim 1, characterized in that, The second diameter of the air guide hole is 0.5 mm smaller than the first diameter of the mechanical blind hole.

3. A multilayer circuit board with a deep drilling interconnect structure and air guide holes according to claim 1, characterized in that, The first diameter of the mechanical blind hole is greater than 0.6 mm.

4. A multilayer circuit board with a deep drilling interconnect structure and air guide holes according to claim 3, characterized in that, The second diameter of the air guide hole is 0.15 mm.

5. A multilayer circuit board with a deep drilling interconnect structure and air guide holes according to claim 1, characterized in that, The mechanical blind hole extends into the N+1th layer at a preset depth of 4 mil.

6. A multilayer circuit board with a deep drilling interconnect structure and air guide holes according to claim 1, characterized in that, The preset offset between the center of the air guide hole and the center of the mechanical blind hole is greater than 0.3mm.

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