Low-loss circuit board
By introducing a foamed resin layered dielectric layer into the circuit board, and using its multiple bubble structures to reduce the dielectric constant and dielectric loss, the problem of low signal transmission efficiency in the microwave band is solved, and more efficient signal transmission and lower signal loss are achieved.
Patent Information
- Application Number
- CN202421731238.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-22
- Publication Date
- 2025-05-27
- Estimated Expiration
- 2034-07-22
AI Technical Summary
The dielectric layer structure of existing circuit boards results in the inability to effectively reduce the dielectric constant and dielectric loss, affecting the transmission of high-frequency signals and high-speed signals, and increasing power consumption.
A foamed resin layer is used, which has a structure of multiple bubbles, and the dielectric constant and dielectric loss are reduced by the presence of bubbles, and the signal transmission speed and signal loss are improved.
It effectively reduces the dielectric constant and dielectric loss, improves signal transmission speed and reduces signal loss, and solves the problem of low signal transmission efficiency of traditional circuit boards in the microwave band.
Smart Images
Figure CN222916274U_ABST
Abstract
Description
Technical Field
[0001] This application relates to a circuit board, especially a low-loss circuit board. Background Art
[0002] Figure 3 The structure of an existing circuit board is schematically disclosed, which includes an initial dielectric layer 80, a plurality of circuit layers 81 disposed on opposite sides of the initial dielectric layer 80, and build-up dielectric layers 82 disposed between adjacent circuit layers 81. Solder mask layers 83 may be provided on the top and bottom surfaces of the existing circuit board. Among them, traditional dielectric layers are usually components made of organic resin materials. For example, the dielectric layer can be BT resin (Bismaleimide Triazine), epoxy resin, polyoxymethylene / polyphenylene ether (PPE / PPO), hydrocarbon, etc.
[0003] In applications in the microwave frequency band (1 - 100 GHz), it is better that the dielectric constant (Dk) and dielectric loss (Df) of the dielectric layer are smaller. The reason is that a larger dielectric constant (Dk) will reduce the electromagnetic wave propagation speed, and a larger dielectric loss (Df) will cause excessive signal loss, thus affecting the transmission of high-frequency signals and high-speed signals, and also increasing power consumption. However, the resin materials of traditional dielectric layers will produce the characteristics of dipole electrode polarization in the microwave frequency band, resulting in limitations of the dielectric constant (Dk) and dielectric loss (Df) of traditional dielectric layers and making it impossible to effectively reduce them. Summary of the Utility Model
[0004] In view of this, the main purpose of this application is to provide a low-loss circuit board to overcome the disadvantage that the dielectric constant and dielectric loss of the existing circuit board cannot be effectively reduced due to its dielectric layer structure.
[0005] The low-loss circuit board of this application includes:
[0006] An initial dielectric layer; and
[0007] A plurality of circuit layers disposed on at least one side of the initial dielectric layer, wherein a foamed resin build-up dielectric layer is provided between two adjacent circuit layers, and the foamed resin build-up dielectric layer has a structure with a plurality of bubbles.
[0008] The structure of the circuit board of the present application, through the setting of the foamed resin build-up dielectric layer, compared with the traditional build-up dielectric layer, the structure of the foamed resin build-up dielectric layer in the present application has bubbles inside, which is more than that of the traditional build-up dielectric layer. Therefore, the structure of the foamed resin build-up dielectric layer reduces its own dielectric constant through the bubbles inside to improve the signal transmission speed, and reduces its own dielectric loss to reduce signal loss, effectively overcoming the disadvantage that the dielectric constant and dielectric loss of the traditional build-up dielectric layer structure of the existing circuit board cannot be effectively reduced. In addition, when the present application can meet the requirements of the rigidity performance of the initial dielectric layer, the possibility of applying the foamed resin to the initial dielectric layer is not excluded. That is to say, the initial dielectric layer can be made of a component made of foamed resin and has a structure with multiple bubbles. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 is a schematic cross-sectional view of an embodiment of the low-loss circuit board of the present application.
[0010] Figures 2A to 2I is a schematic diagram of the manufacturing process of an embodiment of the low-loss circuit board of the present application.
[0011] Figure 3 is a schematic cross-sectional view of an existing circuit board. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0012] Please refer to Figure 1 , an embodiment of the low-loss circuit board of the present application includes an initial dielectric layer 10 and a plurality of circuit layers (for example, including a first circuit layer 21 and a second circuit layer 22). The initial dielectric layer 10 has opposite sides (for example, a top side and a bottom side). The plurality of circuit layers are disposed on at least one side of the initial dielectric layer 10. In the present application, an example is given in which a plurality of circuit layers are respectively provided on opposite sides of the initial dielectric layer 10. The following describes the structure of the low-loss circuit board of the present application with the aid of processes.
[0013] Please refer to Figure 2A , circuit layers (hereinafter defined as a first circuit layer 21) are respectively formed on opposite sides (for example, a top surface and a bottom surface) of an initial dielectric layer 10. The initial dielectric layer 10 can be an organic resin material layer, and the first circuit layer 21 can be a copper layer. The first circuit layers 21 located on opposite sides of the initial dielectric layer 10 can be electrically connected to each other through a via hole 11.
[0014] Please refer to Figure 2B , a copper pillar 30 is formed on each side of the initial dielectric layer 10. The position of the copper pillar 30 can correspond to the position of the via hole 11. The copper pillar 30 can electrically connect the via hole 11 and the first circuit layer 21.
[0015] Please refer to Figure 2C, an insulating layer 31 can be formed on the surfaces of each of the first circuit layers 21 and the initial dielectric layer 10. For example, the insulating layer 31 can be a high-density silicon nitride layer formed by a deposition method, and the deposition method can be sputtering or chemical vapor deposition (CVD).
[0016] Since the processes on the opposite sides of the initial dielectric layer 10 are corresponding, for simplicity of description, only the process on the top side of the initial dielectric layer 10 is taken as an example below, and the process on the bottom side of the initial dielectric layer 10 can be deduced by analogy.
[0017] Please refer to Figure 2D , a foamed resin layer 40 is formed on the top surface of the insulating layer 31, and the insulating layer 31 is completely covered by the foamed resin layer 40, and the insulating layer 31 is not exposed outside the foamed resin layer 40, wherein the foamed resin layer 40 generates a structure with a plurality of air bubbles 400 during forming. For example, the foamed resin layer 40 is a thermosetting foamed resin layer, such as the SAFB product of NIKKAN in Japan, but not limited thereto. By Figure 2C covering the surface of the first circuit layer 21 with the insulating layer 31, the first circuit layer 21 is not exposed outside the hollow structure of the air bubbles 400 of the foamed resin layer 40, avoiding the short-circuit phenomenon caused by copper migration due to the influence of the electric field on the metal atoms (copper atoms) of the first circuit layer 21.
[0018] Please refer to Figure 2E , grind the foamed resin layer 40 until the top of the copper pillar 30 is exposed, that is, the top surface of the foamed resin layer 40 can be flush with the top surface of the copper pillar 30. Among them, because the air bubbles 400 are distributed in the foamed resin layer 40, after grinding, some of the air bubbles 400 located on the top side will be exposed to form cavities 401.
[0019] Please refer to Figure 2F , perform a lamination process using a planarizing layer 50 and a copper foil layer 51. The material of the planarizing layer 50 can be pure resin. The planarizing layer 50 is disposed on the top surface of the foamed resin layer 40 and is laminated to fill the cavities 401 on the top surface of the foamed resin layer 40. The copper foil layer 51 is disposed on the planarizing layer 50 to achieve a planarizing effect for subsequent circuit manufacturing. As Figure 2F shown, the thickness D of the planarizing layer 50 can be only greater than or equal to 1.5 micrometers (μm) without affecting the overall dielectric constant and dielectric loss of the circuit board.
[0020] Please refer to Figure 2G, a blind hole 52 is drilled (e.g., by laser drilling) and desmear is performed at a position on the leveling layer 50 and the copper foil layer 51 corresponding to above the copper pillar 30, so that the top surface of the copper pillar 30 can be exposed from the blind hole 52, and then blind via metallization is performed to form a metal layer 53. The metal layer 53 can be formed on the wall surface of the blind hole 52 and electrically connect the copper pillar 30 and the copper foil layer 51.
[0021] Please refer to Figure 2H , another circuit layer (hereinafter defined as a second circuit layer 22) is fabricated on the copper foil layer 51. For example, the second circuit layer 22 can be fabricated by a photolithography process. When fabricating the second circuit layer 22, the conductive (metal) material can be filled into the blind hole 52 and connected to the metal layer 53 to form a via hole 54, so that the second circuit layer 22 can be electrically connected to the first circuit layer 21 through the via hole 54. That is to say, the via hole 54 is connected between the first circuit layer 21 and the second circuit layer 22. Wherein, the foamed resin layer 40 located between the second circuit layer 22 and the first circuit layer 21 can be defined as a foamed resin build-up dielectric layer 41.
[0022] And so on, according to the specification requirements of the circuit board product, the steps as described above Figures 2B to 2H are repeated for build-up, and then as Figure 2I shown, a solder mask process is performed to fabricate a solder mask layer 60, and thus the embodiment of the low-loss circuit board of the present application as Figure 1 shown is completed.
[0023] In summary, at least one side of the initial dielectric layer 10 is provided with a plurality of circuit layers. A copper pillar 30 is provided on the initial dielectric layer 10 to electrically connect a circuit layer (such as the first circuit layer 21) on the surface of the initial dielectric layer 10. The foamed resin build-up dielectric layer 41 is provided between adjacent upper and lower circuit layers. An insulating layer 31 is provided between one of the circuit layers (such as the first circuit layer 21) and the foamed resin build-up dielectric layer 41. A leveling layer 50 is provided between another circuit layer (such as the second circuit layer 22) and the foamed resin build-up dielectric layer 41, and the leveling layer 50 can fill the cavities 401 on the surface of the foamed resin build-up dielectric layer 41 (i.e., the foamed resin layer 40 as Figure 2F shown) to achieve a leveling effect; the via hole 54 is located in the foamed resin build-up dielectric layer 41, and the second circuit layer 22 and the first circuit layer 21 can be electrically connected to each other through the via hole 54.
[0024] According to the electromagnetic wave velocity formula (as shown in the following formula), it can be seen that the propagation velocity of the electromagnetic wave signal in the dielectric is affected by the dielectric constant, and the propagation velocity of the electromagnetic wave will be faster as the dielectric constant is smaller.
[0025]
[0026] Since the structure of the foamed resin build-up dielectric layer 41 in the circuit board of the present application itself has multiple air bubbles 400, that is to say, the present application uses the structure of a large number of bubbles 400 as the dielectric. Therefore, compared with traditional circuit boards, the present application can significantly reduce the dielectric constant and thus relatively improve the signal transmission speed. In addition, the electromagnetic wave is transmitted without loss in a vacuum. Under standard atmospheric pressure, the dielectric loss also approaches zero loss. Compared with traditional circuit boards, the present application uses the structure of a large number of bubbles 400 as the dielectric, which can reduce the dielectric loss to improve the performance of signal loss. And when the rigidity performance requirements of the initial dielectric layer 10 can be met, the possibility of using foamed resin in the initial dielectric layer 10 is not excluded, that is to say, the initial dielectric layer 10 can be made of a component made of foamed resin and have a structure with multiple bubbles.
[0027] On the other hand, in one embodiment, the foamed resin build-up dielectric layer 41 can be made of a thermosetting foamed resin. Based on the principle of thermal expansion and contraction, when the foamed resin build-up dielectric layer 41 is formed, the volume of the air in its bubbles 400 should be the largest. The operating temperature of other processes or the ambient temperature during the actual use of the circuit board product will be lower than the forming temperature of the foamed resin build-up dielectric layer 41, and the problem of the foamed resin build-up dielectric layer 41 bursting due to air expansion will not occur.
Claims
1. A low-loss circuit board, characterized in that: Include: an initial dielectric layer; and A plurality of circuit layers are arranged on at least one side of the initial dielectric layer, wherein a foamed resin build-up dielectric layer is arranged between two adjacent circuit layers, and the foamed resin build-up dielectric layer is a structure with a plurality of bubbles.
2. The low-loss circuit board according to claim 1, characterized in that: In the two adjacent circuit layers, an insulating layer is disposed between one of the circuit layers and the foamed resin build-up dielectric layer.
3. The low-loss circuit board according to claim 2, characterized in that: The insulating layer is a silicon nitride layer.
4. The low-loss circuit board according to claim 1, characterized in that: In the two adjacent circuit layers, a leveling layer is disposed between one of the circuit layers and the foamed resin build-up dielectric layer to fill in the concave holes on the surface of the foamed resin build-up dielectric layer.
5. The low-loss circuit board according to claim 1, characterized in that: The two adjacent circuit layers are respectively a first circuit layer and a second circuit layer, an insulating layer is provided between the first circuit layer and the foamed resin build-up dielectric layer, and a leveling layer is provided between the second circuit layer and the foamed resin build-up dielectric layer to fill the recesses on the surface of the foamed resin build-up dielectric layer.
6. The low-loss circuit board according to claim 5, characterized in that: The insulating layer is a silicon nitride layer.
7. The low-loss circuit board according to claim 1, characterized in that: The two adjacent circuit layers are electrically connected to each other through a via hole, and the via hole is located in the foamed resin build-up dielectric layer.
8. The low-loss circuit board according to any one of claims 1 to 7, characterized in that: A plurality of circuit layers are respectively disposed on opposite sides of the initial dielectric layer.
9. The low-loss circuit board according to any one of claims 1 to 7, characterized in that: A copper column is arranged on the initial dielectric layer to electrically connect a circuit layer on the surface of the initial dielectric layer.
10. The low-loss circuit board according to claim 8, characterized in that: A copper column is arranged on the initial dielectric layer to electrically connect a circuit layer on the surface of the initial dielectric layer.