Circuit board and method of manufacturing the same

Abstract

This invention provides a circuit board comprising a first circuit board, a second circuit board, a bonding layer, an insulating film, and a strip-shaped slot. The first circuit board includes an insulating layer and a circuit layer disposed on the insulating layer, the circuit layer including at least one strip-shaped line. The second circuit board is disposed opposite to the first circuit board, the circuit layer being located between the insulating layer and the second circuit board. The bonding layer is disposed on the first circuit board and located between the first and second circuit boards. The insulating film is disposed on the second circuit board and located between the bonding layer and the second circuit board. The strip-shaped slot is disposed within the bonding layer and the insulating film, the strip-shaped line of the circuit layer being located inside the strip-shaped slot, and the strip-shaped line extending along the long axis of the strip-shaped slot. This reduces signal transmission loss of the strip-shaped line inside the strip-shaped slot.

Description

Technical Field

[0001] This invention relates to a circuit board, and more particularly to a multilayer circuit board. Background Technology

[0002] Traditional multilayer circuit board designs typically place dielectric materials between the circuit layers. However, this design suffers from transmission loss during signal transmission. Therefore, it is no longer adequate for the high-speed signal transmission requirements of modern products, such as AI servers, which demand reduced signal transmission loss. Summary of the Invention

[0003] Therefore, the present invention provides a circuit board to reduce signal transmission loss of the circuit board.

[0004] At least one embodiment of the present invention also provides a method for manufacturing the above-described circuit board.

[0005] At least one embodiment of the present invention provides a circuit board comprising a first circuit substrate, a second circuit substrate, a first bonding layer, a first insulating film, and a first strip-shaped slot. The first circuit substrate includes an insulating layer and a first circuit layer disposed on the insulating layer, and the first circuit layer includes at least one first strip-shaped circuit. A second circuit substrate is disposed opposite to the first circuit substrate, with the first circuit layer located between the insulating layer and the second circuit substrate. A first bonding layer is disposed on the first circuit substrate and located between the first circuit substrate and the second circuit substrate. A first insulating film is disposed on the second circuit substrate and located between the first bonding layer and the second circuit substrate. The first strip-shaped slot is disposed within the first bonding layer and the first insulating film, with the first strip-shaped circuit of the first circuit layer located inside the first strip-shaped slot, and the first strip-shaped circuit extending along the long axis of the first strip-shaped slot.

[0006] The present invention also provides a method for manufacturing a circuit board, comprising providing an initial circuit substrate, the initial circuit substrate including an insulating layer and a circuit layer disposed on the insulating layer, the circuit layer including at least one strip-shaped circuit; disposing at least one release material on the circuit layer, the release material covering the strip-shaped circuit; after disposing the release material on the circuit layer, bonding a bonding layer is attached to the initial circuit substrate, the bonding layer exposing the surface of the release material; after bonding the bonding layer on the initial circuit substrate, forming a metal layer on the bonding layer, the metal layer covering the bonding layer, the release material and the strip-shaped circuit, and the metal layer connecting to the surface of the release material; after forming the metal layer on the bonding layer, removing the metal layer and the release material to form at least one strip-shaped slot, the strip-shaped circuit being exposed inside the strip-shaped slot; disposing an insulating film on the bonding layer, the insulating film exposing the strip-shaped slot; and after disposing the insulating film, disposing a circuit substrate on the insulating film, the circuit substrate covering the strip-shaped slot, and the bonding layer being located between the insulating film and the circuit substrate.

[0007] Based on the above, a release material is used in the process to protect the space above the reserved strip slot. After lamination, the release material is removed, and then an insulating film with thermoplastic or low-flow properties is applied around the strip slot to form a space sufficient to accommodate the strip circuit. In this way, the signal transmission loss of the strip circuit inside the strip slot can be reduced. Attached Figure Description

[0008] The nature of the invention can be understood from the following detailed description and accompanying drawings. It should be noted that many features are not drawn to industry-standard scale. In fact, for clarity of discussion, the dimensions of various features may be arbitrarily increased or decreased.

[0009] Figure 1 A cross-sectional view of a circuit board according to at least one embodiment of the present invention is shown.

[0010] Figures 2A to 2F A cross-sectional view illustrating a circuit board manufacturing method according to at least one embodiment of the present invention is shown.

[0011] Figures 3A to 3B A cross-sectional view illustrating a circuit board manufacturing method according to at least one embodiment of the present invention is shown. Detailed Implementation

[0012] The present invention will be described in detail with reference to the following embodiments. It should be noted that the following description of the embodiments of the present invention is for illustrative purposes only and is not intended to disclose all embodiments exhaustively or to limit the specific embodiments of the invention. For example, the phrase "a first feature is formed on a second feature" in the description includes various implementations, covering both situations where the first and second features are in direct contact, and situations where an additional feature is formed between the first and second features so that they are not in direct contact. Furthermore, the same element symbols used in the drawings and specification will, as far as possible, represent the same or similar elements.

[0013] Spatially relative terms, such as "lower," "below," "below," "above," and "above," are used here to simply describe the relationship between an element or feature as shown in the figure and another element or feature. These spatially relative terms cover not only the orientation depicted in the figure but also different orientations when using or operating the device. Furthermore, when the element is rotatable (rotating 90 degrees or other angles), the spatially relative descriptive terms used here can also be interpreted accordingly.

[0014] Furthermore, when a number or a range of numbers is described using terms such as "approximately" or "about," the term is intended to encompass numbers within a reasonable range and must take into account the natural differences that would be understood by those skilled in the art during the manufacturing process. A range of numbers encompasses a reasonable range including the described number; for example, within + / - 10% of the described number is based on known manufacturing tolerances that relate to the characteristics of the manufacturing feature. For instance, a material layer with a thickness of "approximately 5 nanometers" could cover a size range from 4.25 nanometers to 5.75 nanometers, where a manufacturing tolerance of + / - 15% for depositing the material layer is known to those skilled in the art. Moreover, reference numerals and / or designations may be repeated in various examples. This repetition is for simplicity and clarity and is not intended to indicate any relationship between the various embodiments and / or configurations discussed herein.

[0015] At least one embodiment of the present invention provides a circuit board 100. Please refer to [reference needed]. Figure 1 The circuit board 100 includes a circuit board 110, a circuit board 120, a bonding layer 150, an insulating film 170, and a strip slot 190. The circuit board 110 includes an insulating layer 112, a circuit layer 114a, and a circuit layer 114b, wherein the insulating layer 112 is located between the circuit layers 114a and 114b. The circuit layer 114a is disposed on the insulating layer 112 and includes at least one strip line TR1. The circuit layer 114b is disposed on the insulating layer 112 and includes at least one strip line TR2.

[0016] It is worth mentioning that, in Figure 1 In the illustrated embodiment, the circuit board 110 is a multilayer board comprising multiple circuit layers (e.g., circuit layers 114a and 114b) and multiple insulating layers (e.g., insulating layer 112), and has six circuit layers, three insulating layers, and two bonding layers (e.g., bonding layer 116) located between the insulating layers. However, in various embodiments of the present invention, the number of circuit layers, the number of insulating layers, and the number of bonding layers of the circuit board 110 are not limited to the above. For example, the circuit board 110 may also be a double-sided board, and may only contain two circuit layers and one insulating layer disposed between the two circuit layers. Alternatively, in other embodiments, the circuit board 110 may also contain four circuit layers, two insulating layers, and one bonding layer.

[0017] The material of the insulating layer 112 may include, but is not limited to, materials with a coefficient of thermal expansion (CTE) of less than 10 ppm / ℃ (i.e., low coefficient of thermal expansion materials), such as polyphenylene oxide (PPO), polyphenylene ether (PPE), or similar materials. Alternatively, the insulating layer 112 may also be a resin or a similar insulating polymer material.

[0018] A circuit board 120 is disposed opposite to a circuit board 110, wherein a circuit layer 114a is located between an insulating layer 112 and a circuit board 120. In other words, the circuit layer 114a of the circuit board 110 is disposed facing the circuit board 120. On the other hand, a circuit board 130 is disposed opposite to a circuit board 110, wherein the circuit board 110 is located between the circuit boards 120 and 130. In this embodiment, the circuit boards 120 and 130 are double-sided boards. That is, the circuit board 120 includes an insulating layer 122 and circuit layers 124a and 124b located on opposite sides of the insulating layer 122, while the circuit board 130 includes an insulating layer 132 and circuit layers 134a and 134b located on opposite sides of the insulating layer 132.

[0019] A bonding layer 150 is disposed on the circuit board 110 and located between the circuit board 110 and the circuit board 120. Specifically, the bonding layer 150 is disposed on the circuit layer 114a of the circuit board 110 and covers a portion of the circuit layer 114a. In addition, the circuit board 100 also includes a bonding layer 160, which is disposed on the circuit board 110 and located between the circuit board 110 and the circuit board 130. The materials of the bonding layers 150 and 160 may include polypropylene (PP), epoxy resin, or similar bonding materials with a low coefficient of thermal expansion.

[0020] An insulating film 170 is disposed on the circuit board 120 and located between the bonding layer 150 and the circuit board 120. In addition, the circuit board 100 also includes an insulating film 180, which is disposed on the circuit board 130 and located between the bonding layer 160 and the circuit board 130. The insulating films 170 and 180 may contain thermoplastic polymers, such as polytetrafluoroethylene (PTFE) or similar insulating materials.

[0021] A strip-shaped slot 190 is disposed within the bonding layer 150 and the insulating film 170. The strip-shaped line TR1 of the circuit layer 114a is located inside the strip-shaped slot 190, and the strip-shaped line TR1 extends along the long axis direction (not shown) of the strip-shaped slot 190. Notably, this long axis direction is... Figure 1 The direction perpendicular to the drawing. Specifically, the strip-shaped slot 190 connects the opposite two end faces of the circuit board 100. Figure 1 Only one end face 100e is shown, while the strip line TR1 located inside the strip slot 190 can also connect the opposite two end faces of the circuit board 100.

[0022] In addition, the circuit board 100 also includes a strip slot 195, which is disposed within the bonding layer 160 and the insulating film 180. The strip line TR2 of the circuit layer 114b is located inside the strip slot 195 and extends along the long axis.

[0023] It is worth mentioning that the circuit board 100 also includes a gas GS, which is distributed inside the strip slots 190 and 195. The dielectric constant of the gas GS is 1 (or approximately 1), and the loss factor of the gas GS is 0 (or approximately 0). For example, the gas GS can be, for example, air or a gas containing a similar composition. Since a portion of strip lines TR1 and TR2 is covered by the gas GS, the loss of strip lines TR1 (and TR2) during signal transmission can be reduced.

[0024] In this embodiment, the circuit board 100 further includes an electronic component 102. This electronic component 102 is disposed on and electrically connected to the circuit substrate 120, which is located between the electronic component 102 and the insulating film 170. Specifically, the electronic component 102 may be an unpackaged die, but the invention is not limited thereto. In other embodiments, the electronic component 102 may also be a packaged chip. The electronic component 102 is electrically connected to the circuit layer 124a of the circuit substrate 120 via a plurality of soldering materials 104, wherein the soldering materials 104 may include, for example, solder paste, solder balls, or the like.

[0025] The circuit board 100 also includes a cover layer 106a, which is disposed on a circuit substrate 120, with the circuit substrate 120 located between the cover layer 106a and the bonding layer 150. On the other hand, the circuit board 100 also includes a cover layer 106b, which is disposed on a circuit substrate 130, with the circuit substrate 130 located between the cover layer 106b and the bonding layer 160. Specifically, in this embodiment, the cover layer 106a is disposed on the circuit layer 124a of the circuit substrate 120 and is located between the circuit layer 124a and the electronic component 102, while the cover layer 106b is disposed on the circuit layer 134b of the circuit substrate 130. The cover layers 106a and 106b can be solder masks, such as green varnish, to reduce solder contamination of the circuit layers 124a and 134b of the circuit substrate 120 during the soldering process.

[0026] The circuit board 100 may also include multiple conductive vias 103v, which may be conductive through-holes, conductive blind vias, or conductive buried vias. These conductive vias 103v are electrically connected to the circuit board 120. In addition, the circuit board 100 may also include multiple through-holes 105, which can be used to eliminate reflected signals and reduce signal transmission loss.

[0027] At least one embodiment of the present invention provides a method for manufacturing a circuit board. Taking circuit board 100 as an example, this manufacturing method may include the following: Figures 2A to 2F The steps are shown below. Please refer to the instructions. Figure 2A First, an initial circuit board 110' is provided. The formation step of the initial circuit board 110' includes: patterning a copper foil laminate (CCL) to make the initial circuit board 110' include an insulating layer and a circuit layer. One of the circuit layers is disposed on the insulating layer and includes at least one linear line. Specifically, one of the circuit layers of the initial circuit board 110' ( Figure 2A The upper circuit layer and the insulating layer are equivalent to the insulating layer 112 and the circuit layer 114a in the circuit substrate 110, and the strip line is equivalent to the strip line TR1 of the circuit layer 114a.

[0028] Please refer to Figure 2B At least one release material 252 is disposed on the circuit layer (i.e., circuit layer 114a of the circuit substrate 110'), and the release material 252 covers the strip-shaped circuit TR1. Please refer to Figure 2CIn this embodiment, the method of manufacturing the circuit board 100 further includes: providing another initial circuit substrate 210', wherein the structure of the initial circuit substrate 210' is similar to that of the initial circuit substrate 110', including an insulating layer and two circuit layers located on opposite sides of the insulating layer. It is particularly noteworthy that one of the circuit layers of the initial circuit substrate 210' ( Figure 2C The lower circuit layer in the circuit board 210 is equivalent to the circuit layer 114b in the circuit board 110, and the strip line of the initial circuit board 210' is equivalent to the strip line TR2 of the circuit layer 114b. In addition, the manufacturing method of the initial circuit board 210' is the same as that of the initial circuit board 110', so it will not be repeated here.

[0029] Alternatively, at least one release material 252 may be disposed on one of the circuit layers of the initial circuit substrate 210' (i.e., circuit layer 114b of the circuit substrate 110), and the release material 252 may cover the strip-shaped circuit TR2. Since the circuit substrate 110 of the circuit board 100 in this embodiment is a multilayer circuit board with three insulating layers, the manufacturing method of the circuit board 100 further includes: disposing an initial circuit substrate 115' between the initial circuit substrate 110' and the initial circuit substrate 210'.

[0030] Please refer to Figure 2D After the release material 252 is applied to the circuit layers (i.e., circuit layers 114a and 114b of the circuit substrate 110), a bonding layer 150 is bonded to the initial circuit substrate 110' by thermoforming. This bonding layer 150 exposes the surface 252s of the release material 252. On the other hand, this step also includes bonding a bonding layer 160 to the initial circuit substrate 210', which also exposes the surface 252s of the release material 252.

[0031] It is worth mentioning that, although not shown in the figure, the step of applying release material 252 to circuit layers 114a and 114b may include: first, applying a release material layer to circuit layers 114a and 114b, which may contain materials such as photosensitive polyimide (PSPI) or similar materials. Then, patterning the release material layer by exposure and development to form release material 252.

[0032] Figure 2DThe step further includes: after bonding the bonding layer 150 onto the initial circuit board 110', forming a metal layer 254a on the bonding layer 150 by, for example, thermoforming. The metal layer 254a covers the bonding layer 150, the release material 252, and the strip-shaped line TR1, and the metal layer 254a is connected to the surface 252s of the release material 252. On the other hand, this step also includes: forming a metal layer 254b on the bonding layer 160.

[0033] Metal layer 254b covers bonding layer 160, release material 252, and strip line TR2, and metal layer 254b connects to surface 252s of release material 252. Metal layers 254a and 254b may contain copper. Notably, in this step, initial circuit substrate 110', initial circuit substrate 210', and initial circuit substrate 115' can also be formed by providing bonding layer 116 between adjacent substrates and hot-pressing them together. Figure 1 The circuit board 110 shown.

[0034] Please refer to Figure 2E After forming a metal layer 254a on the bonding layer 150 and a metal layer 254b on the bonding layer 160, the metal layers 254a and 254b can be removed, for example, by etching. Alternatively, the release material 252 can be removed by stripping to form at least one strip-shaped groove. These strip-shaped grooves are equivalent to... Figure 1 The circuit board 100 has strip slots 190 and 195, and strip lines TR1 and TR2 are exposed inside the strip slots 190 and 195, respectively.

[0035] Next, an insulating film 170 can be formed on the bonding layer 150 by heat pressing, and this insulating film 170 exposes the strip groove 190. On the other hand, this step also includes forming an insulating film 180 on the bonding layer 160, and the insulating film 180 exposes the strip groove 195.

[0036] After the insulating films 170 and 180 are formed, circuit boards 120 and 130 can be formed on the insulating films 170 and 180 respectively by hot pressing. The circuit board 120 covers the strip-shaped slot 190, and the bonding layer 150 is located between the insulating film 170 and the circuit board 120. It is worth mentioning that although in this embodiment the insulating film 170 is formed on the bonding layer 150 and the insulating film 180 is formed on the bonding layer 160 after the metal layers 254a (and 254b) and the release material 252 are removed, the steps of forming the insulating film 170 (and the insulating film 180) in this invention are not limited to this order.

[0037] For example, please refer to Figures 3A to 3B Another embodiment. The difference between this embodiment and the above embodiment is that, before removing metal layer 254a (and metal layer 254b) and release material 252, an insulating film 170 can be formed on the bonding layer 150 by hot pressing, and an insulating film 180 can be formed on the bonding layer 160. In addition, Figures 3A to 3B The insulating film 170 and insulating film 180 can contain thermoplastic polymer materials such as polytetrafluoroethylene. Figures 2E to 2F The insulating film 170 and insulating film 180 materials may include polymer materials with low flow / mid flow at high temperatures, such as halogen-free epoxy resin film (prepreg) or epoxy resin pure rubber.

[0038] Please refer to Figure 2F The manufacturing method of circuit board 100 further includes: after setting circuit board 120 on insulating film 170 and circuit board 130 on insulating film 180, a plurality of conductive holes 103v are formed in bonding layer 150 and insulating film 170 by mechanical grinding, mechanical drilling and electroplating. Initial circuit board 110', initial circuit board 210' and initial circuit board 115' (in this step, initial circuit board 110', initial circuit board 210' and initial circuit board 115' have been formed by thermo-press bonding) can be electrically connected to circuit board 120 and circuit board 130 through these conductive holes 103v.

[0039] It is worth mentioning that the manufacturing method of the circuit board 100 in this embodiment may also include forming a plurality of through holes 105 in the circuit substrate 110, circuit substrate 120, and circuit substrate 130 by means of, for example, mechanical drilling. Thus, a circuit board 100 is substantially formed as shown below. Figure 1 The circuit board 100 is shown.

[0040] In summary, by using a release material in the process, the space above the pre-reserved strip slot is protected. After lamination, the release material is removed, and then an insulating film with thermoplastic or low-flow properties is applied around the strip slot to form a space sufficient to accommodate the strip circuit. Since the dielectric constant of the gas filling the strip slot is 1 (or approximately 1) and the loss factor is 0 (or approximately 0), the signal transmission loss of the strip circuit inside the strip slot can be reduced.

[0041] Although the embodiments of the present invention have been disclosed above, they are not intended to limit the embodiments of the present invention. Those skilled in the art can make some modifications and refinements without departing from the spirit and scope of the embodiments of the present invention. Therefore, the protection scope of the embodiments of the present invention shall be determined by the appended claims.

[0042] [Symbol Explanation]

[0043] 100: Circuit board

[0044] 102: Electronic Components

[0045] 103V: Conductive hole

[0046] 104: Welding materials

[0047] 105: Through hole

[0048] 106a, 106b: Covering layer

[0049] 110, 120, 130: Circuit board

[0050] 110', 210', 115': Initial circuit board

[0051] 112, 122, 132: Insulation layer

[0052] 114a, 114b, 124a, 124b, 134a, 134b: Line layers

[0053] 116, 150, 160: Bonding layer

[0054] 170, 180: Insulating film

[0055] 190, 195: Strip-shaped grooves

[0056] 252: Release material

[0057] 252s: Surface

[0058] 254a, 254b: Metal layers

[0059] GS: Gas

[0060] TR1, TR2: Strip lines.

Claims

1. A circuit board, characterized by, Include: The first circuit board includes: Insulating layer; as well as A first circuit layer is disposed on the insulating layer and includes at least one first strip-shaped circuit. A second circuit board is disposed opposite to the first circuit board, wherein the first circuit layer is located between the insulating layer and the second circuit board. A first bonding layer is disposed on the first circuit substrate and located between the first circuit substrate and the second circuit substrate; A first insulating film is disposed on the second circuit substrate and located between the first bonding layer and the second circuit substrate; as well as A first strip-shaped slot is disposed within the first bonding layer and the first insulating film, wherein the first strip-shaped line of the first circuit layer is located inside the first strip-shaped slot, and the first strip-shaped line extends along the long axis of the first strip-shaped slot.

2. The circuit board of claim 1, wherein Also includes: An electronic component is disposed on the second circuit substrate and electrically connected to the second circuit substrate, wherein the second circuit substrate is located between the electronic component and the first insulating film.

3. The circuit board of claim 1, wherein Also includes: The gas is distributed inside the first strip-shaped groove, and the dielectric constant of the gas is 1, while the loss factor of the gas is 0.

4. The circuit board of claim 1, wherein Also includes: A cover layer is disposed on the second circuit substrate, wherein the second circuit substrate is located between the cover layer and the first bonding layer.

5. The circuit board of claim 1, wherein The first insulating film comprises a thermoplastic polymer.

6. The circuit board of claim 1, wherein Also includes: A third circuit board is disposed opposite to the first circuit board, wherein the first circuit board is located between the second circuit board and the third circuit board. The first circuit board further includes: A second circuit layer is disposed on the insulating layer and includes at least one second strip-shaped circuit, wherein the insulating layer is located between the first circuit layer and the second circuit layer; The second bonding layer is disposed on the first circuit substrate and located between the first circuit substrate and the third circuit substrate; A second insulating film is disposed on the third circuit substrate and located between the second bonding layer and the third circuit substrate; A second strip-shaped slot is disposed within the second bonding layer and the second insulating film, wherein the second strip-shaped line of the second circuit layer is located inside the second strip-shaped slot and extends along the long axis direction.

7. A method of manufacturing a circuit board, characterized by, Include: An initial circuit board is provided, the initial circuit board comprising: Insulating layer; as well as A circuit layer is disposed on the insulating layer and includes at least one linear circuit. At least one release material is disposed on the circuit layer, wherein the release material covers the strip circuit; After the release material is applied to the circuit layer, a bonding layer is attached to the initial circuit substrate, wherein the bonding layer exposes the surface of the release material. After the bonding layer is attached to the initial circuit board, a metal layer is formed on the bonding layer, wherein the metal layer covers the bonding layer, the release material and the strip circuit, and the metal layer is connected to the surface of the release material; After the metal layer is formed on the bonding layer, the metal layer and the release material are removed to form at least one strip-shaped groove, and the strip-shaped line is exposed inside the strip-shaped groove. An insulating film is disposed on the bonding layer, and the insulating film exposes the strip-shaped slot; as well as After the insulating film is applied, a circuit board is applied on the insulating film, wherein the circuit board covers the strip slot, and the bonding layer is located between the insulating film and the circuit board.

8. The method of claim 7, wherein, Also includes: After the circuit board is disposed on the insulating film, a plurality of conductive holes are formed in the bonding layer and the insulating film, wherein the initial circuit board is electrically connected to the circuit board through the conductive holes.

9. The method of claim 7, wherein, After removing the metal layer and the release material, the insulating film is applied to the bonding layer.

10. The method of claim 7, wherein, Before removing the metal layer and the release material, the insulating film is disposed on the bonding layer, wherein the insulating film is located between the metal layer and the bonding layer.

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