CN112449512A - Multi-layer flexible circuit board and manufacturing method thereof - Google Patents
Multi-layer flexible circuit board and manufacturing method thereof Download PDFInfo
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- CN112449512A CN112449512A CN201910816939.8A CN201910816939A CN112449512A CN 112449512 A CN112449512 A CN 112449512A CN 201910816939 A CN201910816939 A CN 201910816939A CN 112449512 A CN112449512 A CN 112449512A
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/46—Manufacturing multilayer circuits
- H05K3/4611—Manufacturing multilayer circuits by laminating two or more circuit boards
- H05K3/4641—Manufacturing multilayer circuits by laminating two or more circuit boards having integrally laminated metal sheets or special power cores
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/03—Use of materials for the substrate
- H05K1/0313—Organic insulating material
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/11—Printed elements for providing electric connections to or between printed circuits
- H05K1/118—Printed elements for providing electric connections to or between printed circuits specially for flexible printed circuits, e.g. using folded portions
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/46—Manufacturing multilayer circuits
- H05K3/4611—Manufacturing multilayer circuits by laminating two or more circuit boards
- H05K3/4626—Manufacturing multilayer circuits by laminating two or more circuit boards characterised by the insulating layers or materials
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Abstract
The invention discloses a multilayer flexible circuit board and a manufacturing method thereof. The manufacturing method of the multilayer flexible circuit board comprises the following steps: forming at least one embedded circuit layer structure, wherein the step of forming the embedded circuit layer structure comprises: providing a bearing substrate which is provided with a bearing surface; forming a patterned circuit on the bearing surface; the patterning circuit comprises at least one solid copper column, at least one inner-layer conductive circuit electrically connected with the solid copper column, and at least one filling gap positioned between the solid copper column and the inner-layer conductive circuit; forming a liquid crystal polymer dielectric material layer on the patterned circuit; the liquid crystal polymer dielectric material layer is coated on the peripheries of the solid copper column and the inner layer conductive circuit and filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer. Therefore, the bonding force between the patterned circuit and the liquid crystal polymer dielectric material layer can be improved.
Description
Technical Field
The present invention relates to a flexible printed circuit board and a method for manufacturing the same, and more particularly, to a multi-layer flexible printed circuit board having an embedded circuit layer structure and a method for manufacturing the same.
Background
In recent years, as technologies related to 4G/5G high-speed transmission have become more and more mature, the design of related electronic products tends to be light, thin, short, and small, and printed circuit boards (FPCBs) used in these electronic products are also miniaturized and lightened compared to electronic components. In order to increase the wiring space inside the printed circuit board, many manufacturing techniques are used to stack a plurality of wiring layers to form a multi-layer wiring structure, and a conductive structure is disposed therein to connect the wiring of each layer, which is called a build-up method.
Furthermore, there are many improvements in the structure design and manufacturing method of the conventional flexible printed circuit board, which are aimed at making the flexible printed circuit board more suitable for the related electronic products with 4G/5G high-speed transmission.
However, the conventional flexible printed circuit board still has the defects of easy signal loss during transmission and poor reliability (e.g., the inner circuit is easily peeled from the substrate or the dielectric material).
The present inventors have considered that the above-mentioned drawbacks can be improved, and have made intensive studies and use of scientific principles, and finally have proposed the present invention which is designed reasonably and effectively to improve the above-mentioned drawbacks.
Disclosure of Invention
The present invention provides a multi-layer flexible printed circuit board and a method for manufacturing the same, which can effectively overcome the defects of the conventional flexible printed circuit board.
The embodiment of the invention discloses a method for manufacturing a multilayer flexible circuit board, which comprises the following steps: forming at least one embedded circuit layer structure, wherein the embedded circuit layer structure is formed by the following steps: providing a bearing substrate which is provided with a bearing surface; forming a patterned circuit on the bearing surface; the patterning circuit comprises at least one solid copper column, at least one inner-layer conductive circuit electrically connected with the solid copper column, and at least one filling gap positioned between the solid copper column and the inner-layer conductive circuit; forming a liquid crystal polymer dielectric material layer on the patterned circuit; the liquid crystal polymer dielectric material layer covers the solid copper column and the periphery of the inner layer conductive circuit and is filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
Preferably, in the step of forming the patterned circuit on the carrying surface, the patterned circuit is formed by: forming a patterned shield above the bearing surface; wherein a plurality of patterning gaps are formed on the inner side of the patterning shield in a surrounding manner; forming a plurality of conductive metals in the plurality of patterned gaps; and removing the patterned shield and forming a plurality of the conductive metals into the patterned lines.
Preferably, in the step of providing the carrier substrate, a metal seed layer is formed on the carrying surface of the carrier substrate and covers the carrying surface of the carrier substrate; in the step of forming the patterned mask, the patterned mask is formed directly on the metal seed layer and over the carrying surface; in the step of forming a plurality of conductive metals, the plurality of conductive metals are formed extending from the metal seed layer toward a direction opposite to the carrier substrate and filled in the plurality of patterned gaps; wherein a plurality of the conductive metals are formed by electroplating; and after removing the patterned shield, the manufacturing method of the multilayer flexible circuit board further comprises the following steps: etching the metal seed layer to remove portions of the metal seed layer not covered by the plurality of conductive metals, thereby forming a plurality of the conductive metals as the patterned lines.
Preferably, after the liquid crystal polymer dielectric material layer is formed on the patterned circuit, the method for manufacturing a multi-layer flexible circuit board further includes: removing the bearing substrate to enable the patterned circuit and the liquid crystal polymer dielectric material layer to form the embedded circuit layer structure together; in the embedded circuit layer structure, the bottom surface of the solid copper pillar is exposed out of the liquid crystal polymer dielectric material layer after the bearing substrate is removed, and is aligned with the bottom surface of the liquid crystal polymer dielectric material layer.
Preferably, before removing the carrier substrate, the method for manufacturing a multi-layer flexible circuit board further comprises: and forming an outer conductive metal layer on the surface of the liquid crystal polymer dielectric material layer on the side opposite to the bearing substrate, and electrically connecting the outer conductive metal layer with the inner conductive circuit embedded in the liquid crystal polymer dielectric material layer through the solid copper column.
Preferably, before removing the carrier substrate, the method for manufacturing a multi-layer flexible circuit board further comprises: forming an outer layer conductive metal on the surface of the liquid crystal polymer dielectric material layer on the side opposite to the bearing substrate; the outer layer conductive metal can be subjected to laser drilling and surface metallization in sequence to form a blind hole structure, so that the outer layer conductive metal can be electrically connected with the inner layer conductive circuit embedded in the liquid crystal polymer dielectric material layer through the blind hole structure.
Preferably, the number of the at least one embedded circuit layer structure is two, and the method for manufacturing the multi-layer flexible circuit board further comprises: stacking two embedded line layer structures together; and contacting the liquid crystal polymer dielectric material layer of one of the embedded circuit layer structures and directly adhering the liquid crystal polymer dielectric material layer of the other embedded circuit layer structure.
Preferably, the liquid crystal polymer dielectric material layers of the two embedded circuit layer structures are directly adhered together by heating, and are not indirectly adhered together by any additional adhesive material or adhesive colloid.
Preferably, the method for manufacturing a multilayer flexible circuit board further comprises: directly contacting and electrically connecting the solid copper pillar of one of the embedded circuit layer structures to the solid copper pillar of the other embedded circuit layer structure; the inner conductive wires of one of the embedded circuit layer structures are not directly contacted with the inner conductive wires of the other embedded circuit layer structure, and the inner conductive wires of the two embedded circuit layer structures are arranged at intervals through the liquid crystal polymer dielectric material layer.
Preferably, in each of the embedded circuit layer structures, the bottom surface of the solid copper pillar is aligned with the bottom surface of the inner-layer conductive circuit, and the height of the solid copper pillar is higher than that of the inner-layer conductive circuit, so that the solid copper pillar and the inner-layer conductive circuit are located in the same liquid crystal polymer dielectric material layer and form a height offset structure together.
The embodiment of the invention also discloses a multi-layer flexible circuit board, which comprises: at least one embedded circuit layer structure, comprising: the patterning circuit comprises at least one solid copper column, at least one inner-layer conductive circuit electrically connected with the solid copper column, and at least one filling gap positioned between the solid copper column and the inner-layer conductive circuit; and the liquid crystal polymer dielectric material layer is coated on the peripheries of the solid copper column and the inner layer conductive circuit and is filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
In summary, the multilayer flexible printed circuit board and the manufacturing method thereof disclosed in the embodiments of the present invention can improve the bonding force between the patterned circuit and the liquid crystal polymer dielectric material layer and effectively improve the signal loss during the transmission process by using the technical scheme that the liquid crystal polymer dielectric material layer covers the peripheries of the solid copper pillar and the inner conductive circuit and is filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
For a better understanding of the nature and technical content of the present invention, reference should be made to the following detailed description of the invention and the accompanying drawings, which are provided for illustration purposes only and are not intended to limit the scope of the invention in any way.
Drawings
FIG. 1 is a first embodiment of a method for manufacturing a flexible printed circuit board according to the present invention.
FIG. 2 is a schematic diagram of a manufacturing method of a flexible printed circuit board according to a first embodiment of the invention.
FIG. 3 is a third embodiment of a method for manufacturing a flexible printed circuit board according to the present invention.
FIG. 4 is a fourth embodiment of a method for manufacturing a flexible printed circuit board according to the present invention.
FIG. 5 is a schematic view (V) of a method for manufacturing a flexible printed circuit board according to a first embodiment of the present invention.
FIG. 6 is a schematic View (VI) of a method for manufacturing a flexible printed circuit board according to a first embodiment of the present invention.
FIG. 7 is a seventh embodiment of a method for manufacturing a flexible printed circuit board according to the present invention.
Fig. 8 is a schematic view (eight) of a method for manufacturing a flexible circuit board according to a first embodiment of the invention.
FIG. 9 is a diagram illustrating a final flexible printed circuit board according to a first embodiment of the present invention.
FIG. 10 is a schematic view of a manufacturing method of a flexible printed circuit board according to a second embodiment of the present invention.
FIG. 11 is a second embodiment of a method for manufacturing a flexible printed circuit board according to the present invention.
FIG. 12 is a third schematic view of a method for manufacturing a flexible printed circuit board according to a second embodiment of the present invention.
FIG. 13 is a diagram illustrating a final flexible printed circuit board according to a second embodiment of the present invention.
Fig. 14 is a diagram illustrating a structure of an embedded circuit layer according to a third embodiment of the invention.
Fig. 15 is a schematic diagram (two) illustrating an embedded circuit layer structure according to a third embodiment of the invention.
Detailed Description
The embodiments of the present invention disclosed herein are described below with reference to specific embodiments, and those skilled in the art will understand the advantages and effects of the present invention from the disclosure of the present specification. The invention is capable of other and different embodiments and its several details are capable of modification and various other changes, which can be made in various details within the specification and without departing from the spirit and scope of the invention. The drawings of the present invention are for illustrative purposes only and are not intended to be drawn to scale. The following embodiments will further explain the related art of the present invention in detail, but the disclosure is not intended to limit the scope of the present invention.
It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are used primarily to distinguish one element from another element or from one signal to another signal. In addition, the term "or" as used herein should be taken to include any one or combination of more of the associated listed items as the case may be.
The invention provides a multilayer flexible circuit board and a manufacturing method thereof. The multilayer flexible circuit board comprises: at least one embedded circuit layer structure. The embedded circuit layer structure comprises a patterned circuit and a liquid crystal polymer dielectric material layer. The patterned circuit comprises at least one solid copper column, at least one inner-layer conductive circuit electrically connected with the solid copper column, and at least one filling gap between the solid copper column and the inner-layer conductive circuit. The liquid crystal polymer dielectric material layer covers the solid copper column and the periphery of the inner layer conducting circuit and is filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
The general structure of the embedded circuit layer structure of the multi-layer flexible printed circuit board of the present invention is described above, and the detailed manufacturing method and the application method of the embedded circuit layer structure of the multi-layer flexible printed circuit board will be described in detail in the first to third embodiments of the present invention.
[ first embodiment ]
Referring to fig. 1 to 8, a multi-layer flexible circuit board and a method for manufacturing the same are provided according to a first embodiment of the present invention. The manufacturing method of the multilayer flexible circuit board comprises the following steps: at least one embedded wiring layer structure 100 is formed, and the embedded wiring layer structure 100 is formed through the following steps S110 to S140. It should be noted that the order of the steps and the actual operation manner carried out in the embodiment can be adjusted according to the requirement, and are not limited to the embodiment.
As shown in fig. 1, the step S110 includes: providing a carrying substrate C having a carrying surface C1. In the present embodiment, the carrier substrate C is mainly used to provide the patterned circuit 1 and the liquid crystal polymer dielectric material layer 2 formed on the carrier surface C1 as described below. After the patterned circuit 1 and the liquid crystal polymer dielectric material layer 2 are formed, the carrier substrate C can be selectively removed, so that the finally formed multi-layer flexible circuit board 1000 does not include any carrier substrate C. The material of the carrier substrate C may be at least one of Polyimide (PI), Polycarbonate (PC), polyethylene terephthalate (PET), and Polytetrafluoroethylene (PTFE), but the present invention is not limited thereto.
As shown in fig. 1 to 4, the step S120 includes: a patterned circuit 1 is formed on the carrying surface C1 (as shown in fig. 4). The patterned circuit 1 includes at least one solid copper pillar 11, at least one inner conductive trace 12 electrically connected to the solid copper pillar 11, and at least one filling gap 13 between the solid copper pillar 11 and the inner conductive trace 12.
In the present embodiment, the patterned circuit 1 is preferably formed on the carrying surface C1 of the carrying substrate C by a semi-additive process (SAP) method, but the invention is not limited thereto. For example, in the embodiment not shown in the present invention, the patterned circuit 1 may also be formed on the carrying surface C1 of the carrying substrate C, for example, by a subtractive method or a full additive method.
More specifically, in the step of forming the patterned circuit 1 on the carrying surface C1, taking the semi-additive method adopted in the present embodiment as an example, the patterned circuit 1 can be formed through the following steps S121 to S124.
As shown in fig. 1, the step S121 includes: a metal seed layer C2 is formed on the carrying surface C1 of the carrying substrate C to cover the whole surface. The metal seed layer C2 may be formed by electroless plating (electro plating) or sputtering (sputtering), for example, and the material of the metal seed layer C2 may be copper metal, for example, but the invention is not limited thereto.
As shown in fig. 2, the step S122 includes: a patterned mask M is formed on the carrier substrate C. More specifically, the patterned mask M is directly formed on the metal seed layer C2 and above the carrying surface C1 of the carrying substrate C. The patterned mask M can be formed by, for example, sequentially covering a photoresist (e.g., pressing a dry film photoresist, or coating a wet film photoresist), and exposing and developing the photoresist. Furthermore, a plurality of patterned gaps M1 are formed around the inner side of the patterned mask M, and the portions of the metal seed layer C2 not shielded by the patterned mask M are exposed to the plurality of patterned gaps M1, so as to provide a conductive metal E (e.g., electroplated copper) to be electroplated thereon.
As shown in fig. 3, the step S123 includes: in the patterned gaps M1, a plurality of conductive metals E are formed by electroplating. More specifically, a plurality of conductive metals E are formed extending from the metal seed layer C2 toward a direction opposite to the carrier substrate C and filled in the plurality of patterned gaps M1. It should be noted that, in the present embodiment, in order to make the conductive metals E have different heights to generate the structure of the step difference, different portions of the patterned mask M may also be designed to have different heights (as shown in fig. 2), so that the conductive metals E formed by the final electroplating have the step difference (e.g., the height of the solid copper pillar 11 in fig. 4 is higher than that of the inner conductive line 12), but the invention is not limited thereto. For example, in another embodiment of the present invention, the patterned mask M may also be designed to have substantially the same height, so that the conductive metals E formed by final electroplating have substantially the same height therebetween (not shown).
As shown in fig. 4, the step S124 includes: the patterned mask M is removed and a plurality of the conductive metals E are formed into a patterned line 1. More specifically, in order to form the conductive metal E into the patterned circuit 1, in the present embodiment, after removing the patterned shield M, the step S124 further includes: the metal seed layer C2 is etched (e.g., microetched, flash etched) to remove the portions of the metal seed layer C2 not covered by the conductive metals E, so that the conductive metals E are formed into the patterned circuit 1 (including the solid copper pillars 11 and the inner conductive lines 12). That is, the removed portion of metal seed layer C2 is the portion of metal seed layer C2 that was originally covered by patterned mask M.
As shown in fig. 5, the step S130 includes: a Liquid Crystal Polymer (LCP) dielectric material layer 2 is formed on the patterned circuit 1 and covers the periphery of the patterned circuit 1. More specifically, the liquid crystal polymer dielectric material layer 2 is disposed to cover the solid copper pillar 11 and the periphery of the inner conductive trace 12, and is filled in the filling gap 13, so that the patterned trace 1 is embedded in the liquid crystal polymer dielectric material layer 2.
The liquid crystal polymer dielectric material layer 2 may be formed, for example, by coating a liquid crystal polymer dielectric material in a flowing state on the patterned circuit 1 to form a wet film. In addition, the wet film can cover the peripheries of the solid copper pillar 11 and the inner layer conductive circuit 12 and fill the filling gap 13 in the coating process. Then, the wet film can be formed into the liquid crystal polymer dielectric material layer 2 through a curing process (e.g., a cooling curing process), and the patterned circuit 1 can be embedded in the liquid crystal polymer dielectric material layer 2 to have a good degree of adhesion with the liquid crystal polymer dielectric material layer 2.
Therefore, the thickness of the liquid crystal polymer dielectric material layer 2 can be accurately controlled by controlling the thickness of the wet film, and can be adjusted according to actual requirements. The liquid crystal polymer dielectric material layer 2 of the present invention is not limited to a wet coating method, but may be formed by laminating a dry film, for example.
As shown in fig. 6, the step S140 includes: on a surface of the liquid crystal polymer dielectric material layer 2 opposite to the carrier substrate C (e.g. the top surface of the liquid crystal polymer dielectric material layer 2 in fig. 6), an outer conductive metal 3 is formed, and the outer conductive metal 3 is electrically connected to an inner conductive trace 12 embedded in the liquid crystal polymer dielectric material layer 2 through a solid copper pillar 11. Alternatively, the outer conductive metal layer 3 may also be formed with a blind via structure 31 by, for example, laser drilling and surface metallization, so that the outer conductive metal layer 3 can be electrically connected to the inner conductive traces 12 embedded in the liquid crystal polymer dielectric material layer 2 through the blind via structure 31.
It should be noted that, in the present embodiment, in the process of forming the embedded circuit layer structure 100, the solid copper pillar 11 and the inner conductive trace 12 of the patterned circuit 1 are formed simultaneously, and the patterned circuit 1 and the outer conductive metal 3 are made of the same material and formed in the same manner (e.g., electroplated copper). Therefore, the patterned circuit 1 and the outer conductive metal 3 can have good bonding force, so that the finally formed multi-layer flexible circuit board 1000 has good reliability.
As shown in fig. 7, the step S150 includes: the carrier substrate C is removed, so that the patterned circuit 1, the liquid crystal polymer dielectric material layer 2, and the outer conductive metal 3 together form the embedded circuit layer structure 100. It should be noted that, in other embodiments of the present invention, the embedded circuit layer structure 100 may only include the patterned circuit 1 and the liquid crystal polymer dielectric material layer 2, but not include the outer conductive metal 3.
In the embodiment, in the embedded wiring layer structure 100, the bottom surface of the solid copper pillar 11 is exposed from the liquid crystal polymer dielectric material layer 2 after the carrier substrate C is removed, and is aligned with the bottom surface of the liquid crystal polymer dielectric material layer 2.
Furthermore, the top surface of the solid copper pillar 11 is also aligned with the top surface of the liquid crystal polymer dielectric material layer 2, but the invention is not limited thereto.
It should be noted that in the embedded circuit layer structure 100 of the present embodiment, the bottom surface of the solid copper pillar 11 is substantially aligned with the bottom surface of the inner conductive trace 12, that is, the bottom surface of the solid copper pillar 11 and the bottom surface of the inner conductive trace 12 are substantially on the same horizontal line, and the solid copper pillar 11 and the inner conductive trace 12 are located in the same liquid crystal polymer dielectric material layer 2.
Furthermore, the height H1 of the solid copper pillar 11 is higher than the height H2 of the inner conductive trace 12, so that the solid copper pillar 11 and the inner conductive trace 12 together form a step structure.
In an embodiment of the invention, the height H1 of the solid copper pillar 11 is between 150 microns and 250 microns, and the height H2 of the inner conductive trace 12 is not greater than 150 microns, but the invention is not limited thereto.
It should be noted that, although the embodiment is described as an example of a structure in which the solid copper pillar 11 and the inner layer conductive trace 12 form a step difference together, the invention is not limited thereto.
As shown in fig. 13, for example, in the following second embodiment of the present invention, the solid copper pillar 11 and the inner conductive trace 12 may have substantially the same height, and the liquid crystal polymer dielectric material layer 2 completely covers the top surface of the solid copper pillar 11, and only the bottom surface of the solid copper pillar 11 is aligned with the bottom surface of the liquid crystal polymer dielectric material layer 2.
The embedded circuit layer structure 100 formed according to the above-mentioned manufacturing method has at least the following advantages. For example: since the liquid crystal polymer dielectric material has the characteristics of low moisture absorption, low dielectric constant (Dk), low dielectric loss (Df), and the like, the finally formed multi-layered flexible printed circuit board 1000 has excellent electrical characteristics and reliability due to the liquid crystal polymer dielectric material layer 2 adopted in the embodiment, and the multi-layered flexible printed circuit board 1000 is particularly suitable for being applied to 4G/5G high-speed transmission related electronic products.
Furthermore, since the patterned circuit 1 is embedded in the liquid crystal polymer dielectric material layer 2, the patterned circuit 1 and the liquid crystal polymer dielectric material layer 2 have good bonding force and are not easily separated from each other.
Furthermore, in an embodiment of the present invention, in order to improve the problem of dielectric loss, the surface of the patterned circuit 1 is preferably a smooth surface. Generally, the smoother the surface of the patterned circuit, the poorer the bonding force between the patterned circuit and the dielectric layer. However, in the present embodiment, since the patterned circuit 1 and the liquid crystal polymer dielectric material layer 2 have an embedded structure therebetween, the patterned circuit 1 has a good bonding force despite a smooth surface.
As shown in fig. 8 and 9, the number of at least one of the embedded circuit layer structures 100, 100' is two. The two embedded wiring layer structures 100, 100' may be identical or different in structure. In this embodiment, one of the plurality of in-line layer structures 100 is configured with a blind via structure 31 (e.g., the upper in-line layer structure 100 of fig. 8), and the other of the plurality of in-line layer structures 100 'is configured without a blind via structure (e.g., the lower in-line layer structure 100' of fig. 8).
Moreover, the method for manufacturing the multi-layer flexible circuit board further comprises the following steps: stacking two embedded wiring layer structures 100, 100' on each other; and contacting the liquid crystal polymer dielectric material layer 2 of one of the embedded circuit layer structures 100 and directly adhering the liquid crystal polymer dielectric material layer 2 'of the other embedded circuit layer structure 100'.
More specifically, the liquid crystal polymer dielectric material layers 2, 2 'of the two embedded circuit layer structures 100, 100' can be directly adhered together, for example, by heating or thermal pressing, without being indirectly adhered together by any additional adhesive material or adhesive glue. That is, the two embedded circuit layer structures 100 and 100' can be directly adhered to each other by the self-adhesive property of the lc polymer dielectric material.
Referring to fig. 9, the method for manufacturing the multi-layer flexible printed circuit further includes: the solid copper pillar 11 of one of the embedded wiring layer structures 100 is directly contacted and electrically connected to the solid copper pillar 11 'of the other embedded wiring layer structure 100'. According to the above configuration, the patterned wires 1, 1 ' of the two embedded wire layer structures 100, 100 ' can be electrically connected to each other by contacting the two solid copper pillars 11, 11 '.
In addition, the inner conductive traces 12 of one of the embedded trace layer structures 100 are preferably not directly contacted with the inner conductive traces 12 ' of the other embedded trace layer structure 100 ', and the inner conductive traces 12, 12 ' of the two embedded trace layer structures 100, 100 ' are disposed at intervals via the liquid crystal polymer dielectric material layers 2, 2 ', but the invention is not limited thereto. For example, in an embodiment not shown in the present disclosure, the inner conductive traces 12, 12 'of the two embedded trace layer structures 100, 100' may be in contact with each other.
According to the above configuration, the multi-layered flexible circuit board 1000 of the present embodiment has two embedded wiring layer structures 100, 100' stacked on each other, thereby forming the flexible circuit board 1000 with a multi-layered wiring structure.
It should be noted that, in other embodiments of the present invention, the multi-layer flexible printed circuit board may also have, for example, three or more embedded circuit layer structures stacked in sequence, and the present invention is not limited thereto.
[ second embodiment ]
As shown in fig. 10 to 13, it is a second embodiment of the present invention. The present embodiment is substantially the same as the method for manufacturing the embedded circuit layer structure 100 of the above-described embodiment. The difference is that the multi-layer flexible circuit board 1000' of the present embodiment has only one embedded circuit layer structure 100, and the outer layer of the embedded circuit layer structure 100 is formed with the outer layer conductive traces 4 electrically connected to the inner layer conductive traces 12 by a semi-additive method.
More specifically, the multi-layer flexible printed circuit of the present embodiment is completed by the following steps: providing an embedded circuit layer structure 100 (as shown in fig. 10), wherein an outer conductive metal 3 and a blind via structure 31 are formed on the embedded circuit layer structure 100, and a carrier substrate C is disposed below the embedded circuit layer structure 100; next, forming an outer patterned mask M' on the outer conductive metal 3 (as shown in fig. 11); then, the outer conductive traces 4 are formed by sequentially performing steps of metal plating, outer patterned mask M' removal, etching, and the like (as shown in fig. 12), and the outer conductive traces 4 and the inner conductive traces 12 are electrically connected to each other; finally, the carrier substrate C is removed to form a flexible circuit board 1000' with a dual-layer circuit structure (see fig. 13).
[ third embodiment ]
As shown in fig. 14 and 15, a third embodiment of the present invention is provided. The present embodiment is substantially the same as the method for manufacturing the embedded circuit layer structure 100 of the above-described embodiment. The difference is that the embedded circuit layer structure 100 of the present embodiment can be further used to provide a copper foil substrate P laminated on the liquid crystal polymer dielectric material layer 2, so as to be beneficial to the application of the following different circuit board processes.
The copper clad substrate P may not be in contact with the patterned circuit 1 (as shown in fig. 14), or the copper clad substrate P may be in contact with the patterned circuit 1 (as shown in fig. 15), for example, which is not limited in the present invention.
[ advantageous effects of the embodiments ]
One of the benefits of the present invention is that the multilayer flexible printed circuit board and the manufacturing method thereof provided by the present invention can improve the bonding force between the patterned circuit and the liquid crystal polymer dielectric material layer and can effectively improve the signal loss problem during the transmission process by using the technical scheme that the liquid crystal polymer dielectric material layer is wrapped around the solid copper pillar and the inner layer conductive circuit and is filled in the filling gap so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
Furthermore, the liquid crystal polymer dielectric material has the characteristics of low moisture absorption, low dielectric constant (Dk), low dielectric loss (Df), and the like, so the finally formed multi-layer flexible printed circuit board has excellent electrical characteristics and reliability, and the multi-layer flexible printed circuit board is particularly suitable for being applied to related electronic products with 4G/5G high-speed transmission.
Furthermore, the present invention can make two independent embedded circuit layer structures directly adhered to each other through the liquid crystal polymer dielectric material layer by the self-adhesion property of the liquid crystal polymer dielectric material, and make the finally formed multi-layer flexible circuit board have an embedded circuit structure, such as: the solid copper pillar and the inner layer conductive circuit are embedded in the liquid crystal polymer dielectric material layer, and the bottom surface of the solid copper pillar and the bottom surface of the inner layer conductive circuit are located on the same horizontal line. According to the above configuration, the two independent embedded circuit layer structures can be directly adhered together without additional adhesive material or adhesive, thereby having the advantages of simple process and high process yield.
Because the lines between the layers of the multilayer flexible circuit board are connected through the solid copper columns, the solid copper columns and the lines are made of the same material, and the surfaces of the solid copper columns and the lines can be designed to be approximate to smooth surfaces (such as the surface with Rz less than or equal to 0.2 um), the problem of signal loss when the multilayer flexible circuit board transmits signals can be effectively solved, and the multilayer flexible circuit board is particularly suitable for being applied to related electronic products of 4G/5G high-speed transmission.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the scope of the present invention, which is defined by the appended claims.
Claims (11)
1. A method for manufacturing a multi-layer flexible printed circuit board is characterized by comprising the following steps:
forming at least one embedded circuit layer structure, wherein the embedded circuit layer structure is formed by the following steps:
providing a bearing substrate which is provided with a bearing surface;
forming a patterned circuit on the bearing surface; the patterning circuit comprises at least one solid copper column, at least one inner-layer conductive circuit electrically connected with the solid copper column, and at least one filling gap positioned between the solid copper column and the inner-layer conductive circuit; and
forming a liquid crystal polymer dielectric material layer on the patterned circuit; the liquid crystal polymer dielectric material layer covers the solid copper column and the periphery of the inner layer conductive circuit and is filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
2. The method as claimed in claim 1, wherein in the step of forming the patterned circuit on the carrying surface, the patterned circuit is formed by:
forming a patterned shield above the bearing surface; wherein a plurality of patterning gaps are formed on the inner side of the patterning shield in a surrounding manner;
forming a plurality of conductive metals in the plurality of patterned gaps; and
the patterned shield is removed and a plurality of the conductive metals are formed into the patterned lines.
3. The method as claimed in claim 2, wherein a metal seed layer is formed on the carrying surface of the carrying substrate during the step of providing the carrying substrate; in the step of forming the patterned mask, the patterned mask is formed directly on the metal seed layer and over the carrying surface; in the step of forming a plurality of conductive metals, the plurality of conductive metals are formed extending from the metal seed layer toward a direction opposite to the carrier substrate and filled in the plurality of patterned gaps; wherein a plurality of the conductive metals are formed by electroplating; and after removing the patterned shield, the manufacturing method of the multilayer flexible circuit board further comprises the following steps:
etching the metal seed layer to remove portions of the metal seed layer not covered by the plurality of conductive metals, thereby forming a plurality of the conductive metals as the patterned lines.
4. The method as claimed in claim 1, wherein after forming the LC polymer dielectric material layer on the patterned circuit, the method further comprises:
removing the bearing substrate to enable the patterned circuit and the liquid crystal polymer dielectric material layer to form the embedded circuit layer structure together; in the embedded circuit layer structure, the bottom surface of the solid copper pillar is exposed out of the liquid crystal polymer dielectric material layer after the bearing substrate is removed, and is aligned with the bottom surface of the liquid crystal polymer dielectric material layer.
5. The method as claimed in claim 4, further comprising, before removing the carrier substrate, the steps of:
and forming an outer conductive metal layer on the surface of the liquid crystal polymer dielectric material layer on the side opposite to the bearing substrate, and electrically connecting the outer conductive metal layer with the inner conductive circuit embedded in the liquid crystal polymer dielectric material layer through the solid copper column.
6. The method as claimed in claim 4, further comprising, before removing the carrier substrate, the steps of:
forming an outer layer conductive metal on the surface of the liquid crystal polymer dielectric material layer on the side opposite to the bearing substrate; the outer layer conductive metal can be subjected to laser drilling and surface metallization in sequence to form a blind hole structure, so that the outer layer conductive metal can be electrically connected with the inner layer conductive circuit embedded in the liquid crystal polymer dielectric material layer through the blind hole structure.
7. The method as claimed in any one of claims 1 to 6, wherein the number of at least one of the embedded circuit layer structures is two, and the method further comprises:
stacking two embedded line layer structures together; and
and contacting the liquid crystal polymer dielectric material layer of one of the embedded circuit layer structures and directly adhering the liquid crystal polymer dielectric material layer of the other embedded circuit layer structure.
8. The method as claimed in claim 7, wherein the liquid crystal polymer dielectric material layers of the two embedded circuit layer structures are directly bonded together by heating, and are not indirectly bonded together by any additional adhesive material or bonding glue.
9. The method of claim 7, further comprising:
directly contacting and electrically connecting the solid copper pillar of one of the embedded circuit layer structures to the solid copper pillar of the other embedded circuit layer structure;
the inner conductive wires of one of the embedded circuit layer structures are not directly contacted with the inner conductive wires of the other embedded circuit layer structure, and the inner conductive wires of the two embedded circuit layer structures are arranged at intervals through the liquid crystal polymer dielectric material layer.
10. The method as claimed in claim 7, wherein in each of the embedded circuit layer structures, the bottom surface of the solid copper pillar is aligned with the bottom surface of the inner conductive trace, and the height of the solid copper pillar is higher than the height of the inner conductive trace, so that the solid copper pillar and the inner conductive trace are located in the same lc polymer dielectric layer and together form a step structure.
11. A multi-layered flexible circuit board, comprising:
at least one embedded circuit layer structure, comprising:
the patterning circuit comprises at least one solid copper column, at least one inner-layer conductive circuit electrically connected with the solid copper column, and at least one filling gap positioned between the solid copper column and the inner-layer conductive circuit; and
and the liquid crystal polymer dielectric material layer is coated on the peripheries of the solid copper column and the inner layer conductive circuit and is filled in the filling gap, so that the patterned circuit is embedded in the liquid crystal polymer dielectric material layer.
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| CN201910816939.8A CN112449512A (en) | 2019-08-30 | 2019-08-30 | Multi-layer flexible circuit board and manufacturing method thereof |
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| CN201910816939.8A CN112449512A (en) | 2019-08-30 | 2019-08-30 | Multi-layer flexible circuit board and manufacturing method thereof |
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