Multilayer circuit board and method of manufacturing the same

Abstract

A multilayer circuit board and a method of manufacturing multilayer circuit board are provided. The multilayer circuit board includes a plurality of circuit structure layers, adhesive layers, and conductor pillars. The circuit structure layers are stacked each other, and each includes a line layer, at least one first recess, and at least one second recess. The first recesses and the second recesses extend in a direction from the line layer toward away from the line layer, and a width of the first recesses and the second recesses increases in a direction from the line layer toward away from the line layer, in which the first recesses and the second recesses of two adjacent circuit structure layers are connected to the other and formed cavities that increase lightness and help meet the demands of high-frequency applications.

Description

Technical Field

[0001] This invention relates to a circuit board, and more particularly to a multilayer circuit board and its manufacturing method. Prior Technology

[0002] The development of existing high-frequency and high-speed electronic products faces the challenge of the demand for thin, light, and compact consumer electronics (such as smartphones and tablets). Existing low-dielectric materials are also difficult to meet the requirements of current electronic products in high-frequency applications, thus limiting the design flexibility of electronic products. Summary of the Invention

[0003] At least one embodiment of the present invention provides a multilayer circuit board and a method for manufacturing the same, in order to meet the needs of existing electronic products in high-frequency applications.

[0004] At least one embodiment of the present invention provides a multilayer circuit board comprising multiple circuit structure layers, multiple adhesive layers, and multiple conductive pillars. These circuit structure layers are stacked on top of each other, and each includes a circuit layer, at least one first recess, and at least one second recess. The first and second recesses extend from the circuit layer in a direction away from the circuit layer, and the width of the first and second recesses increases from the circuit layer in a direction away from the circuit layer, wherein the first and second recesses of adjacent circuit structure layers are interconnected. The adhesive layers connect these stacked circuit structure layers. The conductive pillars are disposed within the second recesses and electrically connect to the circuit layers of these circuit structure layers.

[0005] At least one embodiment of the present invention provides a method for manufacturing a multilayer circuit board, comprising providing a plurality of composite boards. A circuit layer is disposed on each of these composite boards to form a plurality of initial circuit structure layers. At least one first groove and at least one second groove are formed within each of these initial circuit structure layers to form a plurality of circuit structure layers, wherein within the same circuit structure layer, the first groove and the second groove extend from the circuit layer toward a direction away from the circuit layer, and the width of both the first groove and the second groove increases from the circuit layer toward a direction away from the circuit layer. These circuit structure layers are connected and stacked using adhesive layers. During the connection and stacking of these circuit structure layers, the first grooves and second grooves of adjacent two of these circuit structure layers are connected to each other. A plurality of conductive pillars are formed within the second grooves and electrically connect the circuit layers of these circuit structure layers.

[0006] Based on the above, the multilayer circuit board forms cavities by connecting the first and second grooves of two adjacent circuit structure layers, and these cavities can be filled with air. Since it is difficult to achieve a lower dielectric constant with existing materials, forming air regions within the multilayer circuit board through these cavities can effectively reduce the overall dielectric constant of the product, improve high-frequency transmission performance, and contribute to the development trend of high-frequency applications. Simple Explanation of the Diagram

[0007] To make the above and other features, advantages and embodiments of the present invention more apparent and understandable, the detailed description of the accompanying drawings is as follows: Figure 1 is a cross-sectional schematic diagram of a multilayer circuit board according to at least one embodiment of the present invention. Figures 2A to 2C are cross-sectional schematic diagrams of a method for manufacturing the circuit structure layer of a multilayer circuit board according to at least one embodiment of the present invention. Figures 3A to 3D are cross-sectional schematic diagrams of a method for manufacturing the circuit structure layer of a multilayer circuit board according to at least one embodiment of the present invention. Figures 4A and 4B are cross-sectional schematic diagrams of a method for manufacturing the circuit structure layer of a multilayer circuit board according to at least one embodiment of the present invention. Figures 5A to 5C are cross-sectional schematic diagrams of a method for manufacturing the circuit structure layer of a multilayer circuit board according to at least one embodiment of the present invention. Figures 6A and 6B are cross-sectional schematic diagrams of a method for manufacturing the circuit structure layer of a multilayer circuit board according to at least one embodiment of the present invention. Figures 7A to 7C are cross-sectional schematic diagrams of the manufacturing method of a multilayer circuit board with multiple circuit structure layers—Figures 2C, 3D, 4B, 5C, and 6B—compressed together. Implementation

[0008] In the following text, to clearly present the technical features of this application, the dimensions (e.g., length, width, thickness, and depth) of the elements (e.g., layers, films, substrates, and regions) in the drawings will be enlarged proportionally, and the number of some elements may be reduced. Therefore, the description and explanation of the embodiments below are not limited to the number of elements in the drawings or the size and shape of the elements, but should cover the size, shape, and deviations from both caused by actual manufacturing processes and / or tolerances. For example, a flat surface shown in the drawings may have rough and / or non-linear characteristics, and an acute angle shown in the drawings may be rounded. Therefore, the elements presented in the drawings of this application are mainly for illustration and are not intended to accurately depict the actual shape of the elements, nor are they intended to limit the scope of the claims in this application.

[0009] Figure 1 is a cross-sectional schematic diagram of a multilayer circuit board 100 according to at least one embodiment of the present invention. Referring to Figure 1, the multilayer circuit board 100 includes a plurality of circuit structure layers 210, 220, 230, 240, 250, a plurality of adhesive layers 120, and a plurality of conductive pillars 126. These circuit structure layers 210, 220, 230, 240, and 250 are stacked on top of each other and include circuit layers 112, 113, 115, 117, and 119, wherein each of the circuit structure layers 210, 220, 230, 240, and 250 includes at least one first recess 114 and at least one second recess 116.

[0010] The first recesses 114 and second recesses 116 extend from the respective circuit layers 112, 113, 115, 117, and 119 in a direction away from the respective circuit layers 112, 113, 115, 117, and 119, and the width of the first recesses 114 and second recesses 116 increases from the respective circuit layers 112, 113, 115, 117, and 119 in a direction away from the respective circuit layers 112, 113, 115, 117, and 119. The first recesses 114 and second recesses 116 of adjacent circuit structure layers 210, 220, 230, 240, and 250 are interconnected. The first recesses 114 form cavities within the multilayer circuit board 100. The adhesive layers 120 connect the stacked circuit structure layers 210, 220, 230, 240, and 250. These conductive posts 126 are disposed in the second groove 116 and are electrically connected to the circuit layers 112, 113, 115, 117 and 119 of these circuit structure layers 210, 220, 230, 240 and 250.

[0011] The adhesive layer 120 can be made of thermoplastic liquid crystal polymer (LCP), which can be used as a low dielectric material due to its low dielectric constant. The conductive pillars 126 can be formed by electroplating or by plugging with metal paste, and the metal paste can be a conductive material such as copper paste, solder paste, or silver paste.

[0012] The multilayer circuit board 100 also includes a plurality of first insulating layers 130 and two second insulating layers 140. The first insulating layers 130 each cover the adhesive layers 120 and are stacked on top of each other. The two second insulating layers 140 each cover the circuit layers 117 and 119 not yet covered by the adhesive layers 120, and each includes at least one third recess 142 and a protective layer 144. The third recess 142 is disposed on the second insulating layer 140 and exposes the circuit layers 117 and 119. The protective layer 144 is disposed on the exposed circuit layers 117 and 119.

[0013] The first insulating layer 130 is a heat-resistant and high-rigidity LCP. The second insulating layer 140 is a photosensitive polyimide (PSPI), which possesses both photoresist and insulating protective material properties. Photosensitive polyimides can be positive or negative; for example, this embodiment uses a polyimide with positive photoresist properties. The first insulating layer 130 can be etched using an alkaline aqueous solution and is suitable for fabricating smaller through-holes. Furthermore, the second insulating layer 140 can also be a photocurable or thermocurable adhesive, and is not limited to these.

[0014] The multiple first grooves 114, second grooves 116, and third grooves 142 can be formed by laser ablation pattern opening (LAPO). Laser ablation openings can precisely create high-precision openings for the first grooves 114, second grooves 116, and third grooves 142, ensuring that these grooves are formed in the correct positions. The protective layer 144 can be formed by electroplating or chemical plating, but is not limited to these methods.

[0015] Figures 2A to 7C are cross-sectional schematic diagrams of a method for manufacturing a multilayer circuit board 100 according to at least one embodiment of the present invention. Figures 2A to 2C are cross-sectional schematic diagrams of a method for manufacturing a circuit structure layer 210. Figures 3A to 3D are cross-sectional schematic diagrams of a method for manufacturing a circuit structure layer 220. Figures 4A to 4B are cross-sectional schematic diagrams of a method for manufacturing a circuit structure layer 230. Figures 5A to 5C are cross-sectional schematic diagrams of a method for manufacturing a circuit structure layer 240. Figures 6A to 6B are cross-sectional schematic diagrams of a method for manufacturing a circuit structure layer 250. Figures 7A to 7C are cross-sectional schematic diagrams of a method for manufacturing a multilayer circuit board 100 formed by laminating Figures 2C (circuit structure layer 210), 3D (circuit structure layer 220), 4B (circuit structure layer 230), 5C (circuit structure layer 240), and 6B (circuit structure layer 250).

[0016] Referring to Figures 2A to 2C, the method for manufacturing the circuit structure layer 210 may include the following steps. First, a composite board 150 is provided. Next, circuit layers 112 are respectively disposed on the composite board 150 to form an initial circuit structure layer 212. Then, at least one first groove 114 and at least one second groove 116 are formed within the initial circuit structure layer 212 to form the circuit structure layer 210, wherein in the same circuit structure layer 210, the first groove 114 and the second groove 116 extend from the circuit layer 112 in a direction away from the circuit layer 112, and the width of both the first groove 114 and the second groove 116 increases from the circuit layer 112 in a direction away from the circuit layer 112. Then, a plurality of conductive posts 126 are formed within the second groove 116, and these conductive posts 126 are electrically connected to the circuit layer 112 of the circuit structure layer 210. The step of forming the circuit structure layer 210 further includes covering the first insulating layer 130 onto the adhesive layer 120 and stacking the first insulating layer 130, the adhesive layer 120 and the circuit layer 112 on top of each other.

[0017] The composite board 150 may be made of at least one of polyimide (PI), polytetrafluoroethylene (PTFE), and epoxy resin. Alternatively, the composite board 150 may be made of heat-resistant and high-rigidity LCP, similar to the first insulating layer 130, but is not limited thereto.

[0018] Referring to Figures 3A to 3D, a composite board 150 is provided. Next, circuit layers 113 are respectively disposed on the composite board 150 to form an initial circuit structure layer 223. Then, at least one first groove 114 and at least one second groove 116 are formed within the initial circuit structure layer 223 to form a circuit structure layer 220, wherein within the same circuit structure layer 220, the first groove 114 and the second groove 116 extend from the circuit layer 113 in a direction away from the circuit layer 113, and the width of both the first groove 114 and the second groove 116 increases from the circuit layer 113 in the direction away from the circuit layer 113. Then, a plurality of conductive posts 126 are formed within the second groove 116, and these conductive posts 126 are electrically connected to the circuit layer 113 of the circuit structure layer 220.

[0019] The step of forming the circuit structure layer 220 further includes covering the first insulating layer 130 onto the adhesive layer 120, and stacking the first insulating layer 130, the adhesive layer 120, and the circuit layer 113 on top of each other. With the first insulating layer 130 not covered on the adhesive layer 120, after covering the circuit layer 113 and the dielectric layer 154 of the composite board 150 with multiple adhesive layers 120, and before forming at least one first groove 114 and at least one second groove 116, a release film 160 is covered on the surface of the adhesive layer 120 not covered by the first insulating layer 130. After covering the adhesive layer 120 with the release film 160 and forming at least one first groove 114 and at least one second groove 116, the release film 160 is removed from the adhesive layer 120.

[0020] Release film 160 can be made of plastic films such as PET (polyethylene terephthalate), PP (polypropylene), and PE (polyethylene).

[0021] Referring to Figures 4A and 4B, a circuit layer 115 is disposed on the dielectric layer 154 to form an initial circuit structure layer 235. Subsequently, at least one first groove 114 and at least one second groove 116 are formed on the initial circuit structure layer 235 to form a circuit structure layer 230. The steps for forming the first groove 114 and the second groove 116 are similar to those in Figures 3A to 3D and will not be described again here. The difference from the aforementioned manufacturing methods for circuit structure layers 210 and 220 is that in Figures 4A and 4B, there are multiple adhesive layers 120 and two release films 160.

[0022] Referring to Figures 5A to 5C, a circuit layer 117 is disposed on the composite board 150 to form an initial circuit structure layer 247. Subsequently, at least one first groove 114 and at least one second groove 116 are formed within the initial circuit structure layer 247 to form a circuit structure layer 240. The steps for forming the first groove 114 and the second groove 116 are similar to those in Figures 2A to 2C and will not be described in detail here. The difference from the aforementioned manufacturing methods for circuit structure layers 210 and 220 is that Figure 5C does not have a first insulating layer 130 and an adhesive layer 120.

[0023] Referring to Figures 6A and 6B, a circuit layer 119 is disposed on the dielectric layer 154 to form an initial circuit structure layer 259. Subsequently, at least one first groove 114 and at least one second groove 116 are formed within the initial circuit structure layer 259 to form a circuit structure layer 250. The steps for forming the first groove 114 and the second groove 116 are the same as in Figures 3A to 3D, and will not be repeated here. The difference from the aforementioned manufacturing methods for circuit structure layers 210 and 220 is that the first insulating layer 130 and the adhesive layer 120 are not covered on the circuit layer 119.

[0024] Therefore, these circuit structure layers 210, 220, 230, 240, and 250 are formed by forming at least one first groove 114 and at least one second groove 116 within each of these initial circuit structure layers 212, 223, 235, 247, and 259. These initial circuit structure layers 212, 223, 235, 247, and 259 are formed by respectively setting circuit layers 112, 113, 115, 117, and 119. Therefore, the circuit structure layers 210, 220, 230, 240, and 250 have the same or similar structures.

[0025] Referring to Figures 7A to 7C, multiple adhesive layers 120 are used to connect and stack multiple circuit structure layers 210, 220, 230, 240, and 250, and the stacked circuit structure layers 210, 220, 230, 240, and 250 are pressed together. During the connection and stacking of these circuit structure layers 210, 220, 230, 240, and 250, the first grooves 114 and second grooves 116 of adjacent two circuit structure layers 210, 220, 230, 240, and 250 are interconnected. These first grooves 114 are interconnected to form cavities and are disposed between these circuit structure layers 210, 220, 230, 240, 250, adhesive layer 120, and first insulating layer 130.

[0026] Subsequently, conductive posts 126 are disposed within the second groove 116, wherein the conductive posts 126 are disposed between the circuit structure layers 210, 220, 230, 240, 250, the adhesive layers 120, and the protective layers 144, and electrically connect the circuit layers 112, 113, 115, 117, and 119 of the circuit structure layers 210, 220, 230, 240, and 250. Next, two second insulating layers 140 are each covered on the circuit layers 117 and 119, wherein the second insulating layers 140 cover the circuit layers 117 and 119 not yet covered by the adhesive layers 120. Next, at least one third groove 142 is provided on each of the second insulating layers 140, exposing the circuit layers 117 and 119. Finally, a protective layer 144 is provided on each of the exposed circuit layers 117 and 119.

[0027] In summary, in at least one embodiment of the multilayer circuit board 100 of the present invention, the multilayer circuit board 100 forms cavities by connecting adjacent first grooves 114 and second grooves 116 of the circuit structure layers 210, 220, 230, 240, and 250, wherein the cavities can be filled with air. Since it is difficult to achieve a lower dielectric constant with existing materials, forming air regions within the multilayer circuit board 100 through these cavities can effectively reduce the overall dielectric constant of the product and improve high-frequency transmission performance. Furthermore, the conductive pillars 126 are disposed within the second grooves 116 to improve electrical performance and help reduce thickness, realizing the trend of thinner and lighter designs for high-frequency applications.

[0028] While this application has disclosed various embodiments above, it is not intended to limit this application. The above outlines components of several embodiments to facilitate a better understanding of the inventive embodiments by those skilled in the art. Those skilled in the art should understand that they can design or modify other processes and structures based on the embodiments of this invention to achieve the same purpose and / or advantages as the embodiments described herein. Those skilled in the art should also understand that such equivalent processes and structures do not depart from the spirit and scope of this invention, and that various changes, substitutions, and replacements can be made without departing from the spirit and scope of this invention. Therefore, the scope of protection of this application shall be determined by the appended claims.

[0029] 100: Multilayer circuit board 210, 220, 230, 240, 250: Line structure layer 212, 223, 235, 247, 259: Initial circuit structure layer 112, 113, 115, 117, 119: Line Layer 114: First Groove 116: Second groove 120: Adhesive layer 126: Conductive column 130: First insulating layer 140: Second insulating layer 142: Third Groove 144: Protective layer 150: Composite board 154: Dielectric layer 160: Release film

Claims

1. A multilayer circuit board, comprising: Multiple circuit structure layers are stacked on top of each other, and each includes: a circuit layer; at least one first groove; and at least one second groove, wherein the first groove and the second groove extend from the circuit layer in a direction away from the circuit layer, and the width of the first groove and the second groove increases from the circuit layer in a direction away from the circuit layer, wherein the first grooves of adjacent two adjacent circuit structure layers are joined together; multiple adhesive layers connecting the multiple stacked circuit structure layers; and multiple conductive pillars disposed in the second grooves and electrically connected to the circuit layers of the multiple circuit structure layers.

2. The multilayer circuit board as described in claim 1 further includes: a plurality of first insulating layers, each covering the plurality of adhesive layers and stacked on top of each other; And two second insulating layers, each covering the circuit layer not yet covered by the plurality of adhesive layers, each comprising: At least one third groove is disposed on the second insulating layer and exposes the circuit layer; And a protective layer is disposed on the exposed line layer.

3. The multilayer circuit board as described in claim 2, wherein the two second insulating layers are photosensitive polyimide.

4. The multilayer circuit board as described in claim 2, wherein the plurality of conductive pillars are disposed between the plurality of circuit structure layers, the plurality of adhesive layers and the protective layer.

5. A method for manufacturing a multilayer circuit board, comprising: Multiple composite panels are available; Each of the multiple composite boards has a circuit layer set on it to form multiple initial circuit structure layers; At least one first groove and at least one second groove are formed within each of the plurality of initial circuit structure layers to form a plurality of circuit structure layers, wherein in the same circuit structure layer, the first groove and the second groove extend from the circuit layer toward a direction away from the circuit layer, and the width of both the first groove and the second groove increases from the circuit layer toward a direction away from the circuit layer; the plurality of circuit structure layers are connected and stacked using a plurality of adhesive layers; during the connection and stacking of the plurality of circuit structure layers, adjacent first grooves of two adjacent pairs of the plurality of circuit structure layers are bonded to each other; and a plurality of conductive pillars are formed in the second grooves and electrically connected to the circuit layers of the plurality of circuit structure layers.

6. The method of manufacturing a multilayer circuit board as claimed in claim 5, further comprising: covering each of the plurality of first insulating layers on the plurality of adhesive layers and stacking them on top of each other; covering each of the plurality of second insulating layers on the circuit layer not yet covered by the plurality of adhesive layers; providing at least one third groove on each of the second insulating layers and exposing the circuit layer; and providing each of the protective layers on the exposed circuit layer.

7. The method for manufacturing a multilayer circuit board as described in claim 6, further comprising: After covering the plurality of adhesive layers with a dielectric layer of the plurality of circuit layers and the plurality of composite boards, and before forming the at least one first groove and the at least one second groove, a release film is applied to the surface of each of the adhesive layers not covered by the first insulating layer.

8. The method for manufacturing a multilayer circuit board as described in claim 7, further comprising: After covering the release film onto the plurality of adhesive layers, forming the at least one first groove and the at least one second groove, the release film is removed from the plurality of adhesive layers.

9. A method of manufacturing a multilayer circuit board as described in claim 6, wherein the plurality of circuit structure layers stacked on top of each other are laminated before the two second insulating layers are disposed.

10. A method of manufacturing a multilayer circuit board as described in claim 5, wherein the plurality of first grooves are formed by laser ablation openings.

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