Circuit board and method for manufacturing the same

A circuit board, with inbuilt protection against incoming and outgoing electromagnetic interference (EMI), includes an insulating adhesive portion, a first signal line, and a second signal line. The first signal line and the second signal line are surrounded and separated by an electromagnetic shielding film against EMI. The insulating adhesive portion fills a gap between the first signal line and the electromagnetic shielding film and a gap between the second signal line and the electromagnetic shielding film. External interference with signals in the circuit board is reduced, mutual interference between the first signal line and the second signal line is reduced, and electromagnetic radiation of the circuit board is also reduced. A method for manufacturing the circuit board is also disclosed.

The subject matter herein generally relates to circuit boards, and more particularly, to a circuit board and a method for manufacturing the circuit board.

BACKGROUND

5G antennas are used in electronic devices (such as 5G phones) that require high-frequency and high-speed signal transmission. Protection against electromagnetic interference during the signal transmission needs to be improved. Therefore, there is a room for improvement in the art.

DETAILED DESCRIPTION

Some embodiments of the present disclosure will be described in detail with reference to the drawings. If no conflict exists, the following embodiments and features in the embodiments can be combined with each other.

Referring toFIG.12, a method for manufacturing a circuit board100is provided in accordance with an embodiment. The method is provided by way of example, as there are a variety of ways to carry out the method. Referring toFIG.12, the method can begin at block1.

In block1, referring toFIG.1, a circuit substrate10is provided. The circuit substrate10includes a circuit layer13, a dielectric layer11, and a metal layer15stacked in sequence. A surface of the dielectric layer11facing away from the metal layer15is defined as a first surface111. A surface of the metal layer15facing away from the dielectric layer11is defined as a second surface150. The circuit layer13includes a first signal line131and a second signal line133spaced from each other along a first direction X. The first surface111includes an intermediate area111a. The intermediate area111ais disposed between the first signal line131and the second signal line133. The intermediate area111ais spaced apart from the first signal line131and the second signal line133.

The dielectric layer11can be made of polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). In the embodiment, the dielectric layer11is made of polyimide.

The metal layer15can be made of copper, silver, nickel, gold, or their alloys.

In the embodiment, the circuit substrate10is made from a double-sided copper-clad board.

In block2, referring toFIG.2, an insulating adhesive layer33is disposed on the first surface111except for the intermediate area111ato form an intermediate structure40. Along the first direction X, the intermediate structure40includes a first area41on a side of the intermediate area111aaway from the second signal line133and a second area43on a side of the intermediate area111aaway from the first signal line131. The first area41includes a first end410facing away from the second signal line133. The second area43includes a second end430facing away from the first signal line131.

The insulating adhesive layer33can be made of at least one of polypropylene, epoxy resin, polyurethane, phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, polyimide, and the like.

In the embodiment, as shown inFIG.2, the insulating adhesive layer33does not cover both surfaces of the first signal line131and the second signal line133facing away from the dielectric layer11. In some embodiments, the insulating adhesive layer33further covers at least one of the surfaces of the first signal line131and the second signal line133facing away from the dielectric layer11. For example, referring toFIG.3, the insulating adhesive layer33covers both the surfaces of the first signal line131and the second signal line133facing away from the dielectric layer11.

In block3, referring toFIGS.4and5, the first area41and the second area43of the intermediate structure40are bent, with the metal layer15facing outward, so that the first end410and the second end430are connected to the intermediate area111a. Thus, the metal layer15surrounds the first signal line131and the second signal line133to respectively form a first shielding structure151and a second shielding structure153.

Two opposite surfaces of the insulating adhesive layer33disposed opposite to each other in the first shielding structure151are pre-bonded to each other, and two opposite surfaces of the insulating adhesive layer33disposed opposite to each other in the second shielding structure153are pre-bonded to each other. Thus, the bent first area41and the bent second area43are pre-fixed. The bent first area41and the bent second area43are spaced apart from each other.

In the embodiment, referring toFIG.4, the first area41and the second area43are spaced apart from each other.

In some embodiments, referring toFIG.4, a relative position between the first signal line131and the second signal line133remains unchanged before and after the bending. In some embodiments, referring toFIG.5, before and after the bending, a relative position between the first signal line131and the second signal line133changes. For example, the first signal line131and the second signal line133are disposed on two opposite planes of the first surface111after bending.

In block4, referring toFIGS.6and7, an adhesive layer50is disposed between the bent first area41and the bent second area43to bond the first area41and the second area43together. Thereby, the bent first area41and the bent second area43are fixed.

The adhesive layer50may be made of an electrical insulating adhesive or a conductive adhesive. In the embodiment, the adhesive layer50is a conductive adhesive, so as to further enhance a shielding effect between the first signal line131and the second signal line133.

In block5, the intermediate structure40with the adhesive layer50is pressed to obtain the circuit board100. The pressed intermediate structure40has better structural stability and flat appearance. Furthermore, after pressing, the insulating adhesive layer33in the first shielding structure151is completely fused, and the insulating adhesive layer33in the second shielding structure153is completely fused, which further improves the structural stability of the intermediate structure40. Furthermore, deformation of the circuit board100caused by rebound stress at the bent position in the intermediate structure40is avoided, and shielding effect between the first signal line131and the second signal line133is maintained.

In some embodiments, before block5, referring toFIG.8, at least one covering film60is disposed on an outer surface of the intermediate structure40with the adhesive layer50.

Referring toFIG.8, two covering films60are disposed on opposite sides of the intermediate structure40. The two covering films60cover the second surface150and are connected to completely cover the outer surface of the intermediate structure40with the adhesive layer50, to protect the intermediate structure40. In some embodiments, referring toFIG.9, the two covering films60further extend away from the intermediate structure40at a junction of the two covering films60at the second surface150to form extending portions61. The extending portions61of the two covering films60are connected to each other. During the pressing in block5, the extending portions61are fused with each other, thereby further facilitating the structural stability of the intermediate structure40.

In some embodiments, referring toFIGS.10and11, the metal layer15of the circuit substrate10includes at least one connecting pad155electrically connected to the circuit layer13. The covering film60defines at least one opening601, to expose the connecting pads155.

In some embodiments, after the covering film60is disposed, at least one electronic component70is disposed on the connecting pads155.

In some embodiments, the circuit substrate10further includes other circuit layers (not shown) disposed between the circuit layer13and the metal layer15, and the other circuit layers are embedded in the dielectric layer11.

In some embodiments, the block4may be omitted.

The method in the present disclosure does not require a laser shielding hole, and the process is simple and easy to operate. The first shielding structure151and the second shielding structure153are formed by bending, the first shielding structure151surrounds the first signal line131and the second shielding structure153surrounds the second signal line133. External interference of signals in the circuit board100is reduced, and mutual interference between the first signal line131and the second signal line133is also reduced. At the same time, electromagnetic radiation of the circuit board100to the environment is reduced.

Referring toFIGS.13,14, and15, a circuit board100ais further provided. The circuit board100aincludes an electromagnetic shielding film20, an insulating adhesive portion30, a first signal line131, and a second signal line133. The electromagnetic shielding film20includes a first surface20aand a second surface20bopposite to each other. The second surface20bfaces outwards. The electromagnetic shielding film20includes a main portion201, a first bent portion203, and a second bent portion205integrally formed. The first signal line131and the second signal line133are disposed on the first surface20aand spaced apart from each other along the first direction X. The first bent portion203and the second bent portion205are connected to opposite sides of the main portion201along the first direction X. The first bent portion203cooperates with the main portion201to surround the first signal line131. The second bent portion205cooperates with the main portion201to surround the second signal line133. The first bent portion203and the second bent portion205separate the first signal line131from the second signal line133. The insulating adhesive portion30fills a gap between the first bent portion203and the main portion201, and a gap between the second bent portion205and the main portion201, thereby fixing the first bent portion203and the second bent portion205in place.

In some embodiments, referring toFIG.13, the first signal line131and the second signal line133are disposed on the main portion201. In some embodiments, the first signal line131is disposed on the first bent portion203, and/or the second signal line133is disposed on the second bent portion205. Referring toFIG.14, the first signal line131is disposed on the main portion201, and the second signal line133is disposed on the second bent portion205.

The insulating adhesive portion30can be made of at least one of polypropylene, epoxy resin, polyurethane, phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, polyimide, and the like.

In some embodiments, the electromagnetic shielding film20includes a dielectric layer11and a metal layer15stacked on the dielectric layer11. A surface of the dielectric layer11facing away from the metal layer15is defined as the first surface20a, and a surface of the metal layer15facing away from the dielectric layer11is defined as the second surface20b.

The dielectric layer11can be made of polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). In the embodiment, the dielectric layer11is made of polyimide.

The metal layer15can be made of copper, silver, nickel, gold, or their alloys.

In some embodiments, the first bent portion203and the second bent portion205are spaced apart from each other. The circuit board100afurther includes an adhesive layer50. The adhesive layer50is disposed between the first bent portion203and the second bent portion205and bonds the first bent portion203and the second bent portion205together, so as to further fix the first bent portion203and the second bent portion205.

The adhesive layer50may be made of an electrical insulating adhesive or a conductive adhesive. In the embodiment, the adhesive layer50is a conductive adhesive, so as to further enhance an effect of shielding between the first signal line131and the second signal line133.

In some embodiments, referring toFIGS.13and14, the circuit board100afurther includes at least one covering film60covering the second surface20b. Referring toFIG.14, two covering films60cover the second surface20b, and ends of the two covering films60are connected to each other, allowing the two covering films60to cooperatively surround the electromagnetic shielding film20. Referring toFIG.13, the two covering films60extend away from the electromagnetic shielding film20at a junction at the second surface20b, to form extending portions61. The extending portions61of the two covering films60are connected to each other, thereby further improving the stability of the circuit board.

In some embodiments, referring toFIG.15, the metal layer15includes at least one connecting pad155, and the at least one connecting pad155is electrically connected to the first signal line131or the second signal line133. When the covering film60is provided, the covering film60is provided with openings601to expose the connecting pads155.

The circuit board100afurther includes at least one electronic component70disposed on connecting pads155.

The circuit board100afurther includes other circuit layers (not shown) embedded in the dielectric layer11.

In the circuit board100aof the present disclosure, the first signal line131and the second signal line133are surrounded and separated by the electromagnetic shielding film20. Interference by external signals to signals in the circuit board100ais reduced, mutual interference between the first signal line131and the second signal line133is reduced, and at the same time, an electromagnetic radiation of the circuit board100ato the environment is reduced.