CN114641130A - Soft-hard combined circuit board structure and preparation process thereof - Google Patents

Abstract

The invention discloses a rigid-flexible circuit board structure, which comprises: hard circuit boards and flexible circuit boards; the hard circuit board is provided with a plurality of bonding pads; the flexible circuit board is provided with a conductive circuit, an insulating film and a plurality of welding lugs. The two sides of the conducting circuit are covered and connected with the insulating film; the welding lugs are electrically connected with the conductive circuit; and the welding tabs protrude outside the overlapping range of the insulating film and the conductive lines. And each welding lug is respectively and correspondingly electrically connected with each welding pad. In addition, the invention also discloses a preparation process of the structure, which comprises the following steps: firstly, processing a welding lug on a flexible circuit board; printing adhesive glue on the main connecting area and the auxiliary connecting area; then, pressing and connecting the flexible circuit board and the hard circuit board; and finally, correspondingly connecting a welding lug with each welding plate. The invention solves the technical problems of easy damage of the insulating film and low production efficiency in the prior art.

Description

Soft-hard combined circuit board structure and preparation process thereof

Technical Field

The invention relates to the technical field of circuit boards, in particular to a rigid-flexible circuit board structure and a preparation process thereof.

Background

With the increasing demand of terminal application products with the characteristics of light weight, thinness, shortness, smallness and the like such as 5G mobile phones, intelligent wearable equipment, medical equipment and the like and the technical development of flexible printed circuit boards (FPCs) and Rigid Printed Circuit Boards (PCBs), a brand new product of a Rigid-flexible printed circuit board (Rigid-Flex PCB) has been promoted nowadays The volume of the finished product is reduced, and the product performance is improved. Based on this, chinese patent CN214315750U discloses a flexible-rigid combined circuit board, which includes: the device comprises a hard board, a soft board and a fixing mechanism, wherein the hard board and the soft board are welded together through soldering tin; the fixing mechanism is installed on the hard board and used for fixing the soft board.

However, the rigid-flex circuit board has the technical problems that the flexible circuit board insulating film is easy to damage, the production efficiency is low and the like. Specifically, please refer to fig. 1 to 3; a connection structure between a hard wiring board and a soft wiring board in the related art is shown in fig. 1 to 3. As shown in fig. 1 to 3, the hard circuit board is disposed opposite to the flexible circuit board, and the hard circuit board is provided with a plurality of conductive circuit regions, and the flexible circuit board is provided with a plurality of lands corresponding to the conductive circuit regions; and the conductive circuit area is connected with the welding area in a tin melting connection mode, so that the hard circuit board is connected with the soft circuit board. Because of the large thickness difference between the hard circuit board and the flexible circuit board, solder much larger than the thickness of the flexible circuit board must be accumulated on a welding area provided on the flexible circuit board; therefore, the periphery of the land of the flexible wiring board must be heated at a high temperature for a long time so that the solder covers the land and the conductive wiring region, respectively. The insulating film coated on the surface of the flexible circuit board can be burnt due to long-time high-temperature heating, so that the product is defective and scrapped; in addition, the processing time required by the welding process also affects the production efficiency of the product, which is not favorable for large-scale production.

Disclosure of Invention

Therefore, it is necessary to provide a rigid-flex circuit board structure and a manufacturing process thereof to solve the technical problems in the prior art that the insulating film of the rigid-flex circuit board is easy to damage and the production efficiency is low.

A rigid-flex circuit board structure, comprising: hard circuit boards and flexible circuit boards; the hard circuit board and the soft circuit board are arranged oppositely. The hard circuit board is provided with a plurality of bonding pads; the flexible circuit board has a conductive circuit, an insulating film, and a plurality of welding tabs. The two sides of the conducting circuit are covered and connected with the insulating film; the welding lugs are electrically connected with the conductive circuit; and the welding tabs protrude out of the overlapping range of the insulating film and the conductive line. And each welding lug is respectively and correspondingly electrically connected with each welding pad.

Further, the flexible wiring board has a main connection area and an auxiliary connection area.

Further, the main connection region is provided at a middle portion of the flexible wiring board.

Furthermore, the auxiliary connection area is disposed around the welding tab corresponding to each welding tab.

Furthermore, welding points are arranged on the welding lugs; the welding points are arranged in the overlapping area of the welding lug and the welding pad.

In addition, the process for preparing the rigid-flex circuit board structure comprises the following steps:

s1: processing the welding lug on the flexible circuit board;

s2: printing adhesive glue on the main connecting area and the auxiliary connecting area arranged on the flexible circuit board;

s3: pressing and connecting the flexible circuit board and the hard circuit board;

s4: and correspondingly welding each welding lug to each welding pad.

Specifically, in step S1, the flexible circuit board is processed by a die cutting process to obtain the welding tab.

Specifically, the welding tab is coupled to the pad through a laser welding process or an ultrasonic welding process in step S4.

In summary, in the rigid-flex circuit board structure of the present invention, the flexible circuit board is provided with a plurality of welding tabs which are not covered with the insulation film; and electrically connecting the welding lug with the conductive circuit; the hard circuit board is provided with a plurality of welding pads corresponding to each welding lug; and the welding lug and the welding pad are connected by a laser welding or ultrasonic welding process. The welding lug has a flexible structure and extends out of the insulating film, so that the welding lug can be attached to the surface of the bonding pad for welding connection; that is, the welding lug and the welding pad are positioned on the same plane, so compared with the prior art, the welding process between the welding lug and the welding pad has the advantages of short tin soldering time, low heating value of a welding area, high production beat and the like, thereby solving the technical problems of easy damage of the soft and hard combination circuit board insulating film and low production efficiency in the prior art. Furthermore, the invention also discloses a preparation process of the soft and hard combined circuit board, which comprises the steps of firstly processing the soft circuit board through a die cutting process to obtain the welding lugs of which the two sides are not covered with the insulating film; then, uniformly printing adhesive glue on the main connecting area and the auxiliary connecting area arranged on the flexible circuit board; then, pressing and laminating the hard circuit board and the soft circuit board; and finally, the welding lug is connected with the welding pad by adopting the processes of laser welding, ultrasonic welding and the like. Therefore, the manufacturing process of the rigid-flex circuit board can avoid the technical defects that the connection quality is influenced and the like due to excessive molten tin accumulated in a welding area in the prior art.

Drawings

FIG. 1 is a schematic structural diagram of a prior art rigid-flex circuit board;

FIG. 2 is a schematic structural diagram of another direction of a rigid-flex circuit board in the prior art;

FIG. 3 is a schematic structural diagram of a prior art rigid-flex circuit board;

FIG. 4 is a schematic structural diagram of a rigid-flex circuit board structure according to the present invention;

FIG. 5 is a schematic structural view of a rigid-flex circuit board according to another embodiment of the present invention;

FIG. 6 is a schematic diagram of a partial structure of a rigid-flex circuit board structure according to the present invention;

FIG. 7 is a flow chart of a manufacturing process of a rigid-flex circuit board according to the present invention;

FIG. 8 is a schematic structural diagram of step S1 of a rigid-flex circuit board manufacturing process according to an embodiment of the present invention;

FIG. 9 is a schematic structural diagram of step S2 of a rigid-flex circuit board manufacturing process according to an embodiment of the present invention;

FIG. 10 is a schematic structural diagram of step S3 of a rigid-flex circuit board manufacturing process according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram of step S4 in the rigid-flex circuit board manufacturing process according to an embodiment of the invention.

a-hard circuit board, b-conductive circuit area, c-soft circuit board, d-welding area and e-soldering tin position.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

Please refer to fig. 4 to fig. 6; the invention relates to a soft and hard combined circuit board structure, which comprises: a hard wiring board 1 and a flexible wiring board 2; the hard circuit board 1 is disposed opposite to the flexible circuit board 2. The hard circuit board 1 is provided with a plurality of bonding pads 101; the flexible wiring board 2 has conductive traces 201, an insulating film 202, and a plurality of solder tabs 203. The insulating film 202 is connected to both sides of the conductive line 201 in a covering manner; the welding tabs 203 are electrically connected with the conductive circuit 201; also, the welding tab 203 protrudes outside the overlapping range of the insulating film 202 and the conductive line 201. Each of the welding tabs 203 is electrically connected to each of the pads 101.

Specifically, the four corners of the hard circuit board 1 may be respectively provided with one pad 101; the flexible circuit board 2 may be provided with one welding tab 203 in the vicinity of the pad 101; and each welding tab 203 is electrically connected to one of the corresponding bonding pads 101. More specifically, the flexible wiring board 2 may be a common flexible wiring board, which mainly includes a conductive wiring line 201 and an insulating film 202; the two sides of the conductive circuit 201 are covered and connected with the insulating film 202; the insulating film 202 can support and protect the conductive traces 201 located therein. Further, the welding tab 203 is provided outside the range where the insulating film 202 covers the conductive line path 201; the pad 101 is disposed in the vicinity of the position; the conductive traces 201 and the bonding pads 101 are connected to the solder tabs 203, respectively. Since the welding tab 203 extends out of the coverage area of the insulating film 202 and can flexibly cover the bonding pad 101, the welding tab 203 can be electrically connected to the bonding pad 101 through a process with low thermal influence, such as laser welding or ultrasonic welding, at this time, that is, the welding surface of the welding tab 203 and the hard circuit board 1 is on the same plane, so that the time of a soldering process can be reduced, the heating condition generated in the process of the connecting process can be reduced, the production tact can be accelerated, and the damage of the insulating film 202 caused by high heat can be reduced.

Further, the flexible wiring board 2 further has a main connection region 204 and an auxiliary connection region 205; the main connection region 204 is provided in the middle of the flexible wiring board 2; the auxiliary connection area 205 is arranged around the circumference of each welding tab 203. Specifically, in order to further enhance the connection stability between the flexible wiring board 2 and the hard wiring board 1, the main connection region 204 may be provided in the middle of the flexible wiring board 2; and the main connection region 204 is connected to the hard wiring board 1 by means of an adhesive, a double-sided tape, or the like. The main connection region 204 plays a main structural role in connection between the flexible wiring board 2 and the hard wiring board 1. In addition, an auxiliary connection region 205 may be correspondingly disposed near each welding tab 203; the auxiliary connection region 205 may also be connected to the hard circuit board 1 by means of an adhesive or a double-sided tape or the like. The auxiliary connection area 205 has a reinforcing and stabilizing effect on the connection between the welding tab 203 and the bonding pad 101, so that the welding tab 203 can be borne by the auxiliary connection area 205 when being subjected to a sudden pulling force, and the welding tab 203 is prevented from being damaged.

Further, the welding tab 203 is provided with a welding spot 203 a; the welding points 203a are disposed in an overlapping region of the welding tab 203 and the pad 101. Specifically, a user can connect the welding tab 203 with the welding pad 101 in the welding point 203a through the laser welding or ultrasonic welding process; thereby, a solder nugget 203b is formed on the side surface of the welding tab 203; the solder nuggets 203b connect the solder tabs 203 and the pads 101, respectively. Specifically, the solder nugget 203b may be formed on the side surface of the welded tab 203 by the laser welding or ultrasonic welding process; the solder nugget 203b contributes to further enhance the connection stability between the solder tab 203 and the solder pad 101.

Further, please continue to refer to fig. 7 to 11; fig. 7 is a flow chart of a manufacturing process of a rigid-flex circuit board according to the invention. As shown in fig. 7, the invention relates to a process for manufacturing a rigid-flex circuit board, which comprises the following steps:

s1: processing the welding tab 203 on the flexible circuit board 2;

s2: printing adhesive paste on the main connection area 204 and the auxiliary connection area 205 provided on the flexible circuit board 2;

s3: pressing and connecting the flexible circuit board 2 and the hard circuit board 1;

s4: and correspondingly welding each welding lug 203 to each welding pad 101.

Specifically, please continue to refer to fig. 8; fig. 8 is a schematic structural diagram of step S1 in the process for manufacturing a rigid-flex circuit board according to an embodiment of the invention. As shown in fig. 8, a welding tab 203 may be first processed corresponding to each of the pads 101 provided on the hard wiring board 1, and the end of the welding tab 203 is connected to the soft wiring board 2 without the insulating film 202 on both sides. Specifically, the flexible wiring board 2 includes a conductive line 201 and an insulating film 202; the material of the insulating film 202 may be PP, PET, PI, or LCP, which are commonly used thin film materials. Further, the conductive line 201 and the insulating layer 202 may be bonded by a composite process; the composite process is also commonly referred to as a lamination process. The composite process specifically comprises the following steps: the film materials with different properties are adhered together in a certain way and then sealed to play a role in protecting the contents. And the welding tab 203 may be obtained by separating the conductive line 201 in the insulation film 202 through a die cutting process. More specifically, the insulating film 202 covering both sides of the conductive traces 201 may be partially peeled off by a die cutting process, that is, a user may cut off the insulating film 202 by the die cutting process at an area where the welding tab 203 needs to be processed, and then peel off the cut portion of the insulating film 202 to expose the welding tab 203 covered therein. Since the welding tab 203 is partially cut out in the conductive circuit 201 by the die cutting process, that is, the end of the welding tab 203 extends from the conductive circuit 201, that is, the welding tab 203 is electrically connected to the conductive circuit 201. More specifically, the die cutting process is to combine a die cutting plate through a die cutting knife according to a pattern of a product design requirement; then, under the action of the pressure generated by the die cutting equipment, the film-shaped product is roll-cut into the required shape or cut mark. The die cutting process needs to be performed by a die cutter. The die cutting machine can also be called a beer machine, a cutting machine or a numerical control punching machine; the die cutting machine has the working principle that a template and the like carved by a die cutter, a steel knife, a hardware die, a steel wire or a steel plate are utilized, certain pressure is applied to a processed material through the stamping plate, and therefore the processed material is cut into a preset shape. The welded tab 203 shown in fig. 8 is an example of a welded tab manufactured by a die cutting machine using a die cutting process.

Specifically, please continue to refer to fig. 9; fig. 9 is a schematic structural diagram of step S2 in the rigid-flex circuit board manufacturing process according to an embodiment of the invention. As shown in fig. 9, the user can print adhesive paste uniformly on the main connection region 204 and the auxiliary connection region 205 provided to the flexible wiring board 2.

Specifically, please continue to refer to fig. 10; fig. 10 is a schematic structural diagram of step S3 in the rigid-flex circuit board manufacturing process according to an embodiment of the invention. As shown in fig. 10, a user can connect the hard circuit board 1 and the soft circuit board 2, which are prepared in advance and have the desired pads 101, together by press-fitting. Specifically, a predetermined pressure may be applied to the corresponding regions of the main connection region 204 and the auxiliary connection region 205 provided in the flexible circuit board 2, so that the adhesive paste printed in advance in the corresponding regions is sufficiently abutted against and connected to the corresponding regions of the hard circuit board 1.

Specifically, please continue to refer to fig. 11; fig. 11 is a schematic structural diagram of step S4 in the process for manufacturing a rigid-flex circuit board according to an embodiment of the invention. As shown in fig. 11, in step S4, the user may connect the welding tab 203 with the pad 101 through a process of laser welding or ultrasonic welding. In particular, laser welding can reduce the heat input to the required amount, so the metallurgical change range of the heat affected zone is small, and the deformation caused by heat conduction is also minimum. In addition, an electrode is not needed in the laser welding process, and the electrode is not polluted or damaged. In addition, the laser welding process is not a contact welding process, so that the wear and deformation of the machine tool can be minimized. Thus, the damage of the insulating film 202 or other parts due to long-term heating in the conventional solder joining process can be effectively prevented by the laser welding process. Further, the ultrasonic welding is a process of transmitting a high-frequency vibration wave to the surfaces of two objects to be welded and rubbing the surfaces of the two objects against each other under pressure to form fusion between the molecular layers. In step S4, the welding tab 203 and the pad 101 may be connected by an ultrasonic process, and the ultrasonic welding process may not melt the connection between the welding tab 203 and the pad 101, so that the metal characteristics thereof are not weakened; after ultrasonic welding, the welded tab 203 and the pad 101 have good electrical conductivity and extremely low resistivity. Above all, the ultrasonic welding process has short welding time and does not generate high temperature in the welding processing area.

In summary, in the rigid-flex circuit board structure of the present invention, a plurality of welding tabs 203 not covered with the insulating film 202 are disposed on the flexible circuit board 2; electrically connecting the welding tab 203 with the conductive circuit 201; a plurality of welding pads 101 are arranged on the hard circuit board 1 corresponding to each welding lug 203; the welding tab 203 and the welding pad 101 are connected by a laser welding or ultrasonic welding process. The welding tab 203 has a flexible structure and extends out of the insulating film 202, so that the welding tab 203 can be attached to the surface of the pad 101 for welding connection; that is, the welding tab 203 and the bonding pad 101 are located on the same plane, so compared with the prior art, the welding process between the welding tab 203 and the bonding pad 101 has the advantages of short soldering time, low heating value of a welding area, fast production cycle and the like, thereby solving the technical problems of easy damage of the soft and hard combined circuit board insulating film and low production efficiency in the prior art. Further, the invention also discloses a preparation process of the soft and hard combined circuit board, which comprises the steps of firstly processing the flexible circuit board 2 through a die cutting process to obtain the welding lug of which two sides are not covered with the insulating film 202; then, adhesive glue is uniformly printed on the main connecting area 204 and the auxiliary connecting area 205 arranged on the flexible circuit board 2; then, pressing and laminating the hard circuit board 1 and the soft circuit board 2; finally, the welding tab 203 is connected to the bonding pad 101 by laser welding or ultrasonic welding. Therefore, the manufacturing process of the rigid-flex circuit board can avoid the technical defects that the connection quality is influenced and the like due to excessive molten tin accumulated in a welding area in the prior art.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (8)

1. The utility model provides a rigid-flex circuit board structure which characterized in that, this rigid-flex circuit board structure includes: hard circuit boards and flexible circuit boards; the hard circuit board and the soft circuit board are arranged oppositely; the hard circuit board is provided with a plurality of bonding pads; the flexible circuit board is provided with a conductive circuit, an insulating film and a plurality of welding lugs; the two sides of the conducting circuit are covered and connected with the insulating film; the welding lugs are electrically connected with the conductive circuit; and the welding tabs protrude out of the overlapping range of the insulating film and the conductive circuit; and each welding lug is respectively and correspondingly electrically connected with each welding pad.

2. The rigid-flexible circuit board structure of claim 1, wherein: the flexible wiring board has a main connection area and an auxiliary connection area.

3. The soft-hard combined circuit board structure according to claim 2, wherein: the main connection area is disposed in a middle portion of the flexible circuit board.

4. A rigid-flexible circuit board structure according to claim 3, wherein: the auxiliary connecting area is arranged on the periphery of the welding lug corresponding to each welding lug.

5. The rigid-flexible circuit board structure of claim 1, wherein: the welding lug is provided with a welding spot; the welding points are arranged in the overlapping area of the welding lug and the welding pad.

6. A process for preparing a rigid-flex circuit board structure according to any one of claims 1 to 5, comprising the steps of:

s1: processing the welding lug on the flexible circuit board;

s2: printing adhesive glue on the main connecting area and the auxiliary connecting area arranged on the flexible circuit board;

s3: pressing and connecting the flexible circuit board and the hard circuit board;

s4: and correspondingly welding and connecting each welding lug with each welding pad.

7. The process for preparing a rigid-flex circuit board according to the claim, wherein: the flexible wiring board is processed by a die cutting process to obtain the welding tab in step S1.

8. The manufacturing process of a rigid-flex circuit board as claimed in claim, wherein: the welding tab is coupled to the pad through a laser welding process or an ultrasonic welding process in step S4.

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