CN115397096A

CN115397096A - Double-layer flexible circuit board, electronic product and conduction method

Info

Publication number: CN115397096A
Application number: CN202210980081.0A
Authority: CN
Inventors: 王定锋; 代宏信; 徐磊; 王晟齐; 夏鹏; 徐文红
Original assignee: Tongling Guozhan Electronic Co ltd
Current assignee: Tongling Guozhan Electronic Co ltd
Priority date: 2022-08-07
Filing date: 2022-08-07
Publication date: 2022-11-25

Abstract

The invention discloses a double-layer flexible circuit board, an electronic product and a conducting method, which comprise an intermediate insulating layer and metal circuit layers positioned on two sides of the intermediate insulating layer, wherein the surface of at least one metal circuit layer is provided with a point-shaped dent, the other surface of the metal circuit layer is provided with a point-shaped bulge corresponding to the point-shaped dent, the intermediate insulating layer is provided with a through hole corresponding to the point-shaped bulge, and the metal circuit layers on two sides realize contact conduction through the point-shaped bulge at the through hole position. The invention has simple manufacturing process, low cost and no environmental pollution, and realizes conduction without additionally adding a conductive medium.

Description

Double-layer flexible circuit board, electronic product and conduction method

Technical Field

The invention relates to the field of circuit boards, in particular to a double-layer flexible circuit board, an electronic product and a conduction method.

Background

The double-layer circuit board refers to a circuit board with circuit layers on the front surface and the back surface of the circuit board, and compared with a single-layer circuit board, the double-layer circuit board can be designed with more complex circuits, so that the double-layer circuit board is widely applied.

The double-layer circuit board of the traditional technology has the following conducting modes of the front layer and the back layer: (1) punching to make a through hole, forming a layer of conductive object on the hole wall, and then electroplating copper to form a conductive copper metal layer with the thickness of more than 10 microns on the hole wall; (2) punching to make a through hole, printing conductive ink or conductive adhesive in the through hole and at the edge of the through hole, and connecting the upper layer of metal and the lower layer of metal to form conduction; (3) punching to manufacture a via hole, printing solder paste, then performing reflow soldering, and welding an upper layer and a lower layer to form conduction; (4) and the element is utilized as an LED lamp bead, so that one part of welding feet of the element is welded on the front circuit layer, and the other part of the welding feet of the element is welded on the back circuit layer to form the conduction of the front circuit layer and the back circuit layer.

However, the above methods for connecting the front and back circuit layers all have drawbacks, and specifically, the method (1) requires chemical deposition of conductive material and copper electroplating, which not only complicates the process and increases the cost, but also causes environmental pollution; in the mode (2), the used conductive ink or conductive adhesive is chemical, so that the environment is polluted after the conductive ink or the conductive adhesive is manufactured and used; moreover, the conductive ink and the conductive adhesive are both provided with insulating resin, so that the resistance value is high, the conductivity is low, and the cost is high; in the mode (3), the reflow soldering conduction is carried out by using the solder paste, and because the tin is expensive and has high cost and chemical volatile matters in the solder paste, the reflow soldering causes pollution to the environment; in the method (4), the component is soldered by using the solder paste, and the conduction is performed by the over-reflow soldering, and as in the method (3), the cost is high, and the environmental pollution is also caused.

In short, in the conduction mode of the double-layer circuit board in the prior art, the via hole needs to be manufactured first, and then the conductive medium needs to be additionally arranged in the via hole to realize conduction, so that the manufacturing process is complicated, the pollution is heavy, and the cost is high.

Therefore, there is a need to improve and optimize the conduction mode of the existing double-layer circuit board.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides the double-layer flexible circuit board, the electronic product and the conduction method, the manufacturing process is simple, conduction is realized without additionally adding a conductive medium, the cost is low, and no environmental pollution is caused.

In a first aspect, an embodiment of the present invention provides a dual-layer flexible circuit board, including a middle insulating layer and metal circuit layers located on two sides of the middle insulating layer, where a dot-shaped dent is disposed on a surface of at least one of the metal circuit layers, a dot-shaped protrusion is disposed on another surface of the metal circuit layer corresponding to the dot-shaped dent, a through hole is disposed on the middle insulating layer corresponding to the dot-shaped protrusion, and the metal circuit layers on two sides are in contact conduction through the dot-shaped protrusion at the through hole.

Optionally, the circuit board has at least one conducting position, and at each conducting position, the number of the dot-shaped dents is more than 2.

Optionally, the dot-shaped dents are disposed on one of the metal circuit layers, or the dot-shaped dents are disposed on two metal circuit layers, and the dot-shaped protrusions are in contact conduction with the opposite metal circuit layer at the through hole.

Optionally, the two metal circuit layers are provided with dotted dents, and the dotted dents on the two metal circuit layers are arranged in a contraposition mode, or in a staggered mode, or in a partial contraposition mode, and in a partial staggered mode.

Optionally, a through hole is formed in part or all of the metal at the point-shaped dent, and the through hole penetrates through the metal circuit layer where the point-shaped dent is located; or the through holes penetrate through the two metal circuit layers, and the through holes on the two metal circuit layers are aligned.

Optionally, the punctiform protrusions at the perforation positions form an annular structure, and the metal of the annular structure is in contact conduction with the opposite metal circuit layer at the through hole positions.

Optionally, the middle insulating layer at the position of the through hole is hooped on the dot-shaped protrusion, and the dot-shaped protrusion and the opposite metal circuit layer form stable contact conduction.

Optionally, the opening width of the dot-shaped dent is less than or equal to 1.5mm.

Optionally, a solder mask is arranged on the metal circuit layer, a dot-shaped recess is arranged in the solder mask covering the metal circuit layer with the dot-shaped dent, and the dot-shaped recess corresponds to the dot-shaped dent; or the solder mask covered on the metal circuit layer with the dot-shaped dents does not have dot-shaped dents at the positions of the dot-shaped dents; or the solder mask layer on one metal circuit layer is provided with point-shaped depressions corresponding to the point-shaped dents of the metal circuit layer, and the solder mask layer on the other metal circuit layer is not provided with the point-shaped depressions.

Optionally, the solder mask layer is solder mask ink or a solder mask film.

Optionally, the metal circuit layer is a copper metal layer, or an aluminum metal layer, or a copper-aluminum composite metal layer.

Optionally, the two metal circuit layers are the same metal layer or different metal layers.

An embodiment of a second aspect of the present invention provides an electronic product, including the dual-layer flexible circuit board according to any one of the embodiments of the first aspect, on which electronic components are soldered.

Optionally, the electronic product is a lighting fixture.

The embodiments of the first aspect and the second aspect of the invention have at least one of the following advantages: the point-shaped dents are arranged on the surface of at least one metal circuit layer, the position, corresponding to the point-shaped dents, of the other surface of the metal circuit layer is point-shaped and protruded, the through hole is formed in the position, corresponding to the point-shaped protruded position, of the middle insulating layer, the metal circuit layers on the two sides are in contact conduction through the point-shaped protruded positions, the mode that two circuit layers are in conduction through copper electroplating, conductive glue or conductive ink, solder paste reflow soldering and the like in the prior art is abandoned, the mode is completely different from the mode that two metal circuit layers are in conduction through additionally arranging conductive media in the prior art, the conduction mode is simple, the manufacturing process is obviously simplified, the problem of environmental pollution caused by the existence of the conductive media in the prior art is solved, the two circuit layers can be tightly and firmly attached and conducted through due to the point-shaped protruded arrangement, the contact conduction is reliable, the double-layer flexible circuit board or the electronic product manufactured by the method can bear repeated bending in the use process, the folding resistance is good, and the service life of the product is long.

An embodiment of a third aspect of the present invention provides a method for turning on a double-layer flexible printed circuit board, including:

providing a double-layer flexible circuit board, wherein the double-layer flexible circuit board comprises a middle insulating layer and metal circuit layers positioned on two sides of the middle insulating layer;

the double-layer flexible circuit board is placed in a die, wherein at least one surface of the die is provided with an extrusion nail, at least one metal circuit layer is extruded to the middle insulating layer by the extrusion nail, the extrusion nail is extruded on the surface of the metal circuit layer to form a punctiform dent, a punctiform bulge is formed on the other surface of the metal circuit layer corresponding to the punctiform dent position, the middle insulating layer is simultaneously extruded by the extrusion nail to form a through hole, so that the punctiform bulge is in contact with the opposite metal circuit layer at the through hole position, and the contact conduction is realized.

Optionally, one side of the die is provided with an extrusion nail, the other side of the die is a plane, and the extrusion nail extrudes one metal circuit layer to obtain a punctiform dent and a punctiform bulge; or the two sides of the die are provided with extrusion nails which simultaneously extrude the two metal circuit layers in the die, so that point-shaped dents and point-shaped bulges are formed on the two metal circuit layers.

Optionally, the extrusion nails on two sides of the die are arranged oppositely; or the extrusion nails on the two sides of the die are arranged in a staggered manner; or the extrusion nail parts on the two sides of the die are arranged oppositely, and the parts are arranged in a staggered way.

Optionally, more than 2 extrusion nails are arranged on one surface of the die with the extrusion nails.

Optionally, the provided double-layer flexible circuit board is a fully bare circuit board, and after the extrusion step is completed, the solder mask layer is manufactured on the two metal circuit layers.

Optionally, the double-deck flexible line way board that provides all has the circuit board of solder mask for both sides, in the mould, utilizes extrusion nail extrusion solder mask, transmits the extrusion force of extrusion nail for metal circuit layer through the solder mask for form punctiform sunken on the solder mask, correspond punctiform sunken position on the metal circuit layer and form punctiform dent and punctiform arch.

Optionally, the provided double-layer flexible circuit board is a semi-bare circuit board, one surface of the circuit board is a bare circuit, the other surface of the circuit board is provided with a solder mask, and after the extrusion step is completed, the solder mask is manufactured on the metal circuit layer of the bare circuit.

Optionally, the double-layer flexible circuit is heated wholly or locally.

The embodiment of the third aspect of the invention has at least one of the following advantages: the double-layer flexible circuit board is arranged in the die, wherein at least one surface of the die is provided with the extrusion nail, at least one metal circuit layer is extruded to the middle insulating layer by the extrusion nail, the extrusion nail is extruded on the surface of the metal circuit layer to form a point-shaped dent, the other surface corresponding to the point-shaped dent forms a point-shaped bulge, the extrusion nail simultaneously crushes the middle insulating layer to form a through hole, the point-shaped bulge is contacted with the opposite metal circuit layer at the through hole position, and contact conduction is realized.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the methods and structures particularly pointed out in the written description and drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention.

FIG. 1-1 is a schematic plan view of a front circuit layer according to an embodiment of the present invention;

fig. 1-2 are schematic plan views of the backside circuit layer in the embodiment of the invention;

FIGS. 1-3 are schematic plan views of solder mask frontside (with pad windows) in an embodiment of the invention;

FIGS. 1-4 are schematic plan views of the backside solder mask (without pad windows) in an embodiment of the invention;

fig. 1-5 are schematic plan views of two-layer flexible printed circuit boards according to embodiments of the present invention (four conducting positions, each having 8 dot-shaped recesses of 2 × 4);

FIG. 2-1 is a schematic structural diagram of a front circuit layer with dot-shaped indents according to an embodiment of the present invention (fully bare circuit board);

FIG. 2-1-1 is an exploded schematic view of FIG. 2-1;

FIG. 2-2 is a schematic structural diagram of the front and back sides of FIG. 2-1 with solder resist ink;

FIG. 2-3 is a schematic structural diagram of solder resist cover films formed on the front and back sides of FIG. 2-1;

FIG. 3-1 is a schematic structural view of a back side circuit layer with dot-shaped dents according to an embodiment of the present invention (a bare board)

FIG. 3-2 is a schematic structural diagram of the front and back sides of FIG. 3-1 with solder resist ink;

FIG. 3-3 is a schematic structural diagram of solder resist cover films formed on the front and back sides of FIG. 3-1;

FIG. 4-1 is a schematic structural diagram of a dual-layer metal circuit layer with dot-shaped dimples (fully bare circuit board) according to an embodiment of the present invention;

FIG. 4-2 is a schematic structural diagram of the front and back sides of FIG. 4-1 with solder resist ink;

FIG. 4-3 is a schematic structural diagram of solder resist cover films formed on the front and back sides of FIG. 4-1;

FIG. 5-1 is a schematic structural diagram of a front circuit layer with dotted indents according to an embodiment of the present invention (a half-bare circuit board, a back cover film with solder resist);

FIG. 5-2 is a schematic diagram of the structure of FIG. 5-1 after solder mask ink is formed on the front side wiring layer;

FIG. 5-3 is a schematic structural diagram of FIG. 5-1 after a solder mask film is formed on the front circuit layer;

FIG. 6-1 is a schematic structural diagram of a back circuit layer with dotted indents according to an embodiment of the present invention (a half bare circuit board, a front surface with a solder-mask film);

FIG. 6-2 is a schematic diagram of the structure of FIG. 6-1 after solder mask ink is formed on the back side circuit layer;

FIG. 6-3 is a schematic structural diagram of FIG. 6-1 after a solder mask film is formed on the back circuit layer;

FIG. 7-1 is a schematic structural diagram of a double-layer metal circuit layer with dotted dents in the embodiment of the present invention (a half-bare circuit board, a back side with a solder-resistant cover film);

FIG. 7-2 is a schematic diagram of the structure of FIG. 7-1 after solder mask ink is formed on the front side wiring layer;

FIG. 7-3 is a schematic structural diagram of FIG. 7-1 after a solder mask film is formed on the front circuit layer;

FIG. 8-1 is a schematic structural diagram of a double-layer metal circuit layer with dotted dents in the embodiment of the present invention (a half-bare circuit board, a cover film with solder on the front side);

FIG. 8-2 is a schematic diagram of the structure of FIG. 8-1 after solder mask ink is formed on the back side circuit layer;

FIG. 8-3 is a schematic structural diagram of FIG. 8-1 after a solder resist cover film is formed on the back circuit layer;

FIG. 9-1 is a schematic structural diagram of a front circuit layer with dot-shaped dents according to an embodiment of the present invention (before pressing, a solder resist cover film is applied to both sides of a dual-layer circuit board, and after pressing, dot-shaped dents are formed on the solder resist cover film);

FIG. 9-2 is a schematic structural diagram of a portion of the middle insulating layer, a portion of the front circuit layer, and a portion of the two metal circuit layers according to an embodiment of the present invention;

FIG. 9-2-1 is a partial enlarged view of A in FIG. 9-2 (the middle insulating layer is not broken, and the two metal wiring layers are not in contact conduction);

FIG. 9-2-2 is a close-up view of B in FIG. 9-2 (the front side circuit layer is crushed to form a through-hole);

FIG. 9-2-3 is a partial enlarged view of C in FIG. 9-2 (the front circuit layer and the back circuit layer are simultaneously punctured to form a through hole);

FIG. 10-1 is a schematic diagram of a structure of a dual-layer metal circuit layer with dot-shaped dents in an embodiment of the present invention (before extrusion, both surfaces of the dual-layer circuit board are provided with solder resist cover films, and after extrusion, dot-shaped dents are formed on the solder resist cover films);

fig. 10-2 is a schematic structural view illustrating that a part of the back surface circuit layer, a part of the front surface circuit layer, and a part of the two metal circuit layers are broken in the embodiment of the present invention;

FIG. 10-2-1 is an enlarged view of a portion D of FIG. 10-2 (the backside circuit layer is crushed to form a through-hole);

FIG. 10-2-2 is an enlarged view of a portion E of FIG. 10-2 (the front side circuit layer is crushed to form a through-hole);

FIG. 10-2-3 is an enlarged view of a portion F of FIG. 10-2 (the front and back trace layers are simultaneously crushed to form perforations);

FIG. 11-1 is a schematic view of a structure of a double-layer metal wiring layer in an embodiment of the present invention when a solder resist layer is broken (before pressing, a solder resist cover film is provided on both sides of the double-layer wiring board, and after pressing, a dot-like depression is formed on the solder resist cover film);

FIG. 11-1-1 is an enlarged view of a portion G of FIG. 11 (the back solder resist cover film, the back wiring layer are crushed);

FIG. 11-1-2 is a partial enlarged view of H in FIG. 11 (solder resist cover film on the front side, front side wiring layer crushed);

11-1-3 are enlarged partial views of I in FIG. 11 (the front solder resist cover film, the front wiring layer, the back solder resist cover film, and the back wiring layer are all crushed);

FIG. 12-1 is a schematic view of the structure of a die (upper die belt pressing pins) in the embodiment of the present invention;

FIG. 12-2 is a schematic structural view of a mold according to an embodiment of the present invention (the upper mold and the lower mold are provided with extrusion nails and are arranged in a staggered manner);

FIG. 12-3 is a schematic structural diagram of a mold according to an embodiment of the present invention (the upper mold and the lower mold are both provided with extrusion nails, and the extrusion nails on the upper mold and the lower mold are aligned);

FIG. 12-4 is a schematic structural view of a mold according to an embodiment of the present invention (the upper mold and the lower mold are provided with extrusion nails, and the extrusion nails on the upper mold and the lower mold are partially dislocated and partially aligned);

12-5 are schematic structural views of the die in the embodiment of the invention (the upper die and the lower die are both provided with the extrusion nails, and the extrusion nails on the upper die and the lower die are arranged in a staggered manner);

description of reference numerals:

an intermediate insulating layer-1, a resin film-11, an adhesive layer-12 and a through hole-13;

front circuit layer-21, back circuit layer-22, dot-shaped dent-23, dot-shaped bump-24, perforation-25;

the solder mask comprises a point depression-31, solder mask ink-32, a solder mask covering film-33, a solder mask-331, a glue layer-332, a front solder mask-34, a pad window-341 and a back solder mask-35;

an upper die-41, a lower die-42 and a pipe position nail-421;

and extruding the nail-5.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the features of the embodiments and examples described below may be arbitrarily combined with each other without conflict.

The following provides many different embodiments, or examples, for implementing the methods, structures, and methods of the present invention.

With particular reference to fig. 1-1 to 11-1-3, an embodiment of the first aspect of the present invention provides a dual-layer flexible circuit board, which includes an intermediate insulating layer 1 and metal circuit layers disposed on two sides of the intermediate insulating layer 1, where the metal circuit layers include a front surface circuit layer 21 and a back surface circuit layer 22, the intermediate insulating layer 1 insulates and separates the front surface circuit layer 21 and the back surface circuit layer 22 from each other, so as to prevent the two metal circuit layers from contacting a short circuit, and at the same time, the intermediate insulating layer 1 serves as a carrier for the front surface circuit layer 21 and the back surface circuit layer 22, so that the circuit board has sufficient strength to prevent the circuit board from being scattered, the intermediate insulating layer 1 may include a resin film 11 and adhesive layers 12 disposed on two surfaces, namely, the front surface circuit layer 21 and the back surface circuit layer 22 are bonded and fixed on the resin film 11 through the adhesive layers 12, the resin film 11 may be a PI film or a PET film, and the intermediate insulating layer 1 may also be another structure or material known in the art; the middle insulating layer 1 is made of flexible materials, so that the circuit board is a flexible circuit board, and for a rigid circuit board, the middle insulating layer is thick and hard and cannot be broken by an extrusion nail to form an effective through hole; a dot-shaped dent 23 is arranged on the surface of at least one of the metal circuit layers, and a dot-shaped protrusion 24 is arranged on the other surface of the metal circuit layer corresponding to the dot-shaped dent 23, that is, the metal circuit layer includes an upper surface and a lower surface, taking the front circuit layer 21 as an example, the upper surface of the front circuit layer 21 has the dot-shaped dent 23, and the lower surface forms the dot-shaped protrusion 24 at the position of the dot-shaped dent 23, it can be understood that the dot-shaped dent 23 and the dot-shaped protrusion 24 can also be arranged on the back circuit layer 22, and can also be arranged on both the front circuit layer 21 and the back circuit layer 22; the middle insulating layer 1 is provided with through holes 13 corresponding to the positions of the point-shaped protrusions 24, the through holes 13 penetrate through the middle insulating layer 1, so that a channel for the contact conduction of two metal circuit layers at the through hole positions is formed, for example, in some embodiments, the through holes 13 penetrate through the adhesive layer 12 and the resin film 11, the metal circuit layers on both sides are in contact conduction through the point-shaped protrusions 24 at the through hole 13 positions, namely, at the through hole 13 positions, the point-shaped protrusions 24 on one metal circuit layer are in contact with the opposite metal circuit layer to realize circuit communication; when the front circuit layer 21 and the back circuit layer 22 are both provided with the dot-shaped protrusions 24 and are aligned, the aligned dot-shaped protrusions 24 are in contact with the through holes 13, so that the circuit communication of the two metal circuit layers is realized.

The circuit board is provided with at least one conducting position, the conducting position is a position for conducting two metal circuit layers up and down according to the design requirement of a circuit, the conducting position on the circuit board is at least one, the upper and lower metal circuit layers are conducted up and down at a plurality of positions under most conditions, the conducting position is as the position indicated by an arrow X shown in figures 1-5, the figure shows that the conducting position on the circuit board is 4, and each conducting position is provided with 8 point-shaped depressions of 2X 4; in some embodiments of the invention, at each conducting position, the number of the dot-shaped dents is more than 2, so as to ensure that the contact conduction at each conducting position is reliable; specifically, as shown in fig. 9-2-1, considering that two metal circuit layers are in contact conduction through a dot-shaped bump, in the process of actually making a dot-shaped dent and a dot-shaped bump, conduction may be abnormal due to poor contact, for example, in the process of forming a dot-shaped dent and a dot-shaped bump by pressing a pressing nail, an unexpected situation that the pressing nail does not crush the intermediate insulating layer 1 and does not form a through hole may occur, at this time, although a dot-shaped dent and a dot-shaped bump are formed, the dot-shaped bump cannot be in contact with the opposite metal circuit layer because of no through hole being formed, in order to reduce the risk of circuit breaking caused by poor contact due to the possible situation, more than 2 dot-shaped dents are provided at each conducting position, the occurrence of a poor situation that the conducting position is not conducted is avoided by providing a plurality of dot-shaped dents, and the probability that the plurality of dot-shaped bumps are not in contact with the opposite metal circuit layer is very low, thereby significantly improving the yield of the circuit board; specifically, in some embodiments, at each conducting position, 4 dot-shaped dents may be disposed, corresponding to 4 dot-shaped protrusions, and the 4 dot-shaped dents are densely arranged in a manner of 1 × 4; in other embodiments, 16 dot-shaped dents may be disposed at each conducting position, corresponding to 16 dot-shaped protrusions, and the 16 dot-shaped dents are densely arranged in a manner of 4 × 4, so as to ensure that each conducting position is conducted according to the requirements of the circuit design, as shown in fig. 1-5, and 8 dot-shaped dents of 2 × 4 are disposed at each conducting position.

The arrangement of the dot-shaped indent 23 can be various, in some embodiments, the dot-shaped indent 23 is arranged on one of the metal circuit layers, and the dot-shaped protrusion 24 is in contact conduction with the opposite metal circuit layer after passing through the through hole 13; specifically, as shown in fig. 2-1 to 2-3 and 5-1 to 5-3, the dot-shaped dimples 23 are disposed on the upper surface of the front circuit layer 21, the dot-shaped protrusions 24 are formed on the lower surface of the front circuit layer 21, and the dot-shaped protrusions 24 are in contact with and conducted with the back circuit layer 22 at the positions of the through holes 13; in another embodiment, as shown in fig. 3-1 to 3-3 and 6-1 to 6-3, the dot-shaped indent 23 is disposed on the lower surface of the back circuit layer 22, the upper surface of the back circuit layer 22 forms a dot-shaped protrusion 24, the dot-shaped protrusion 24 is in contact with and conducted with the front circuit layer 21 at the position of the through hole 13, wherein the front surface, the back surface, the upper surface and the lower surface are determined by the observation angle of the shown figures; in other embodiments, as shown in fig. 4-1 to 4-3 and fig. 7-1 to 8-3, both metal wiring layers are provided with dot-shaped indentations 23, and the dot-shaped protrusions 24 are in contact conduction with the opposite metal wiring layer at the positions of the through holes 13; specifically, as shown in fig. 7-1 to 8-3, the dot-shaped dimples 23 are respectively disposed on the upper surface of the front circuit layer 21 and the lower surface of the back circuit layer 22, and correspondingly, dot-shaped protrusions 24 are formed on the lower surface of the front circuit layer 21 and the upper surface of the back circuit layer 22, and the dot-shaped protrusions 24 on the front circuit layer 21 correspond to the dot-shaped protrusions 24 on the back circuit layer 22 in the up-down position, at this time, the dot-shaped protrusions 24 on the front circuit layer 21 or the back circuit layer 22 contact the aligned dot-shaped protrusions 24 at the through holes 13, so as to achieve contact conduction; specifically, the dot-shaped bumps 24 on the front surface circuit layer 21 and the dot-shaped bumps 24 on the back surface circuit layer 22 are staggered from each other in the vertical direction, that is, no dot-shaped bump is formed on the back surface circuit layer 22 directly below the dot-shaped bump 24 on the front surface circuit layer 21, the dot-shaped bump on the back surface circuit layer 22 is positioned at the lower left or lower right of the dot-shaped bump on the front surface circuit layer 21, and at this time, the dot-shaped bump 24 is in contact conduction with the opposite metal circuit layer at the position of the through hole 13; specifically, a part of the dot-shaped bumps 24 on the back surface wiring layer 22 is located right below the dot-shaped bumps 24 on the front surface wiring layer 21, and a part is located at the lower left or lower right.

In some embodiments of the present invention, through holes 25 are formed at the positions of some or all of the dot-shaped indentations 23, where the through holes 25 penetrate through one metal circuit layer where the dot-shaped indentations 23 are located, or the through holes 25 penetrate through two metal circuit layers, where the positions of the through holes 25 on the two metal circuit layers are aligned. When the metal circuit layer is extruded by the extrusion nail, the stress area of the metal circuit layer is small, the metal circuit layer can be extruded and broken by the extrusion nail to form the through hole 25, and the existence of the through hole 25 does not influence the existence of the point-shaped bulge 24 and the contact conduction of the point-shaped bulge 24 and the opposite metal circuit layer. As shown in fig. 9-2-2, 9-2-3, 10-2-1, and 10-2-2, the pressing nail breaks one metal wiring layer such that the through hole 25 penetrates one metal wiring layer where the dot-shaped dents 23 are located; as shown in fig. 10-2-3, the extrusion nail can also simultaneously extrude the opposite metal circuit layers, so that the through holes 25 penetrate through the two metal circuit layers, and the through holes 25 on the two metal circuit layers are arranged in an opposite position.

It can be understood that, when the extrusion nail is extruded, since the extrusion force is transmitted to the opposite metal line layer, when the dot-shaped dent 23 is formed by extrusion of the extrusion nail, the opposite metal line layer may be thinned due to the extrusion force, as shown in fig. 2-1 to 3, 9-2-1 to 9-2-3, 10-2-1 to 10-2-2, 11-1-1 and 11-1-2, and whether the metal line layer is extruded to form the through hole 25 or not, the metal line layer opposite to the extrusion nail may be thinned.

In some embodiments, the through hole 25 may be located at a central position of the dot-shaped indent 23, in this case, the dot-shaped protrusion 23 at the position of the through hole 25 forms a ring structure, and the metal of the ring structure is in contact conduction with the opposite metal circuit layer at the position of the through hole 13, that is, the metal is protruded at the hole edge of the through hole 25 after the pressing nail breaks the metal circuit layer due to the ductility of the metal. In other embodiments, the metal of the wall of the point-like indentation 23 is torn to form a through hole 25 during the pressing process of the metal circuit layer by the pressing nail.

Considering that the intermediate insulating layer is made of a resin film, or the resin film and glue, the resin film and the glue both have elasticity, after the intermediate insulating layer 1 is squeezed to form the through hole 13, the intermediate insulating layer at the position of the through hole 13 forms a contraction force due to the elasticity, so that the intermediate insulating layer 1 at the position of the through hole 13 is clamped on the point-shaped protrusion 24, the point-shaped protrusion 24 is controlled and fixed by the wrapping of the elastic intermediate insulating layer 1 at the position of the through hole 13, and the point-shaped protrusion 24 can always keep good contact with the opposite metal circuit layer to form stable contact conduction.

In some embodiments of the present invention, the opening width of the dot-shaped indent 23 is less than or equal to 1.5mm, preferably 0.5-1mm, so that good contact conduction can be formed without damaging the overall appearance of the circuit board.

According to the difference of the manufacturing process, in some embodiments of the invention, the solder mask layer covering the metal circuit layer with the dot-shaped dent 23 is provided with the dot-shaped recess 31, and the dot-shaped recess 31 corresponds to the dot-shaped dent 23; or the solder mask layer covered on the metal circuit layer with the dot-shaped dents 23 does not have dot-shaped dents at the positions of the dot-shaped dents 23; or the solder mask on one metal circuit layer is provided with point-shaped depressions 31, the point-shaped depressions 31 correspond to the point-shaped dents 23 of the metal circuit layer, and the solder mask on the other metal circuit layer does not have point-shaped depressions. Specifically, as shown in fig. 7-1 to 11-1-3, after the metal circuit layer is covered with the solder mask, the point-like dent 23 is made by using the extrusion nail, at this time, the extrusion force of the extrusion nail is transmitted to the metal circuit layer through the solder mask, the point-like dent 31 is formed on the solder mask, and the point-like dent 23 is formed on the metal circuit layer at the corresponding position; specifically, as shown in fig. 2-1 to 4-3, after a dot-shaped dent 23 is formed on a bare circuit board (without forming a solder mask), the solder mask is formed, and at this time, the solder mask is not pressed by a pressing nail, so that the solder mask has no dot-shaped dent 31; specifically, as shown in fig. 9-1 to 9-2-3, after the metal circuit layer is covered with the solder resist layer, one surface of the mold has the extrusion pins, and the other surface has no extrusion pins, so that one of the metal circuit layers has the dot-shaped recesses 31, and the other of the metal circuit layers has no dot-shaped recesses. The solder mask layer may be solder mask ink 32 or solder mask coating film 33, and in some embodiments, the solder mask coating film 33 includes a solder mask film 331 and a glue layer 332, and the glue layer 332 adheres and fixes the solder mask film 331 on the metal circuit layer, such as a PET film with glue, a PI film with glue, and the like.

In some embodiments of the present invention, the two metal circuit layers are the same metal layer, and both the two metal circuit layers are copper metal layers, or both the two metal circuit layers are aluminum metal layers, or both the two metal circuit layers are copper-aluminum composite metal layers; the two metal circuit layers may also be different metal layers, for example, the front circuit layer 21 is a copper metal layer, and the back circuit layer 22 is an aluminum metal layer. Copper and aluminum are convenient to obtain, the conductivity is good, particularly, the ductility is very good, the dot-shaped dents 23 and the dot-shaped protrusions 24 with preset sizes can be easily manufactured, and therefore good contact conduction can be formed.

An embodiment of a second aspect of the present invention provides an electronic product, including the double-layer flexible printed circuit board according to any one of the embodiments of the first aspect, where an electronic component is soldered on the double-layer flexible printed circuit board, a solder pad window is arranged on a solder resist layer of the double-layer flexible printed circuit board, and the electronic component is soldered at the solder pad window and is conducted with a metal circuit layer. In some embodiments, the electronic product is a lighting fixture, and it is understood that the electronic product is not limited to lighting fixtures.

The surface of at least one metal circuit layer is provided with the point-shaped dents 23, the positions of the other surface of the metal circuit layer corresponding to the point-shaped dents 23 are point-shaped protrusions 24, through holes 13 are formed in the positions of the middle insulating layer 1 corresponding to the point-shaped protrusions 24, the metal circuit 2 layers on two sides are in contact conduction through the point-shaped protrusions 24 in the positions of the through holes 13, the mode that two circuit layers are in conduction through electroplated copper, conductive glue or conductive ink, solder paste reflow soldering and the like in the prior art is abandoned, the mode is completely different from the mode that two metal circuit layers are in conduction through additionally arranged conductive media in the prior art, the conduction mode is simple, the manufacturing process is obviously simplified, the problem of environmental pollution caused by the existence of the conductive media in the prior art is solved, the two circuit layers can be always kept in close and firm fit conduction through due to the arrangement of the point-shaped protrusions 24, the contact conduction is reliable, the manufactured double-layer flexible circuit board or the electronic product can bear repeated bending in the use process, the folding resistance is good, and the service life of the product is long.

The embodiment of the third aspect of the invention provides a conducting method of a double-layer flexible circuit board.

Example 1:

providing a double-layer flexible circuit board, wherein the double-layer flexible circuit board comprises a middle insulation layer 1 and metal circuit layers positioned on two sides of the middle insulation layer, the double-layer flexible circuit board is a fully-bare circuit board, a solder mask layer is not manufactured on the surface of the metal circuit layer, the metal circuit layers are all copper circuit layers, and the middle insulation layer 1 is a PET film with glue;

an extrusion die is installed on an extruder, as shown in fig. 12-1, wherein an upper die 41 of the die is provided with extrusion nails 5, a lower die 42 is provided with tube position nails 421, a double-layer flexible circuit board is provided with tube position holes (not shown), the tube position holes are sleeved on the tube position nails of the lower die, at this time, the extrusion nails are just aligned to positions on the circuit board where point-shaped dents need to be made, the surface of the lower die contacting the circuit board is a plane, each conducting position is provided with 4 extrusion nails with a layout of 1 × 4, the maximum diameter of the extrusion nails is 0.5mm, the die is closed, the extrusion pressure is controlled to be 50kg, the extrusion time is controlled to be 0.5s, the extrusion nails extrude the front circuit layer 21 to the middle insulating layer 1, and the point-shaped dents 23 are formed at the positions on the upper surface of the front circuit layer 21 extruded by the extrusion nails, the lower surface of the front circuit layer 21 correspondingly forms a point-shaped bulge 24, the extrusion nail is heated and kept at 350 ℃, when the extrusion nail is in extrusion contact with the circuit board, heat can be rapidly transferred to PET and glue of the intermediate insulating layer, the PET and the glue can be rapidly melted or softened, meanwhile, a through hole 13 is formed under the strong pressure of the extrusion nail, the point-shaped bulge 24 is in contact with the opposite back circuit layer 22 at the position of the through hole 13 to realize contact conduction, the extrusion is completed, the mold is opened, then a PET covering film (solder-resisting covering film) with glue is in press bonding on the metal circuit layer through a press bonding machine on a bare circuit, the press bonding of the solder-resisting covering film is a known technology in the field, and the circuit board structure shown in the figures 2-3 can be obtained without repeated description; and carrying out a line power connection test.

Example 2:

providing a double-layer flexible circuit board, wherein the double-layer flexible circuit board comprises a middle insulation layer 1 and metal circuit layers positioned on two sides of the middle insulation layer 1, the double-layer flexible circuit board is a semi-bare circuit board, a solder mask covering film 33 (covering film known in the art) is already manufactured on a back circuit layer 22, a solder mask layer is not manufactured on the surface of a front circuit layer 21, the metal circuit layers are all aluminum circuit layers, and the middle insulation layer 1 is a PI film with glue;

an extrusion die is installed on an extruder, and specifically, as shown in fig. 12-3, an upper die 41 and a lower die 42 of the die are respectively provided with an extrusion nail 5, the extrusion nails 5 of the upper die 41 and the lower die 42 are arranged in an aligned mode, the lower die 42 is provided with a pipe position nail 421, a double-layer flexible circuit board is provided with a pipe position hole, the pipe position hole on the double-layer flexible circuit board is sleeved on the pipe position nail of the lower die, at the moment, the extrusion nail is just aligned to a position on the circuit board where a point-shaped dent needs to be manufactured, 16 extrusion nails are arranged at each conduction position and are in a 4-x-4 layout, the maximum diameter of the extrusion nail is 0.2mm, the die is closed, the extrusion pressure is controlled to be 25kg, the extrusion time is controlled to be 1s, the extrusion nails simultaneously extrude the front circuit layer 21 and the back circuit layer 22 to the middle insulating layer 1, and the point-shaped dent 23 is formed at the position where the upper surface of the front circuit layer 21 is extruded by the extrusion nails, the lower surface of the front circuit layer 21 correspondingly forms a dot-shaped protrusion 24, the lower surface of the back circuit layer 22 forms a dot-shaped dent 23 at a position extruded by an extrusion nail, the upper surface correspondingly forms a dot-shaped protrusion 24, the extrusion nail is heated and kept at 500 ℃, when the extrusion nail is in extrusion contact with the circuit board, heat can be rapidly transferred to an intermediate insulating layer PI and glue, the PI and the glue are rapidly softened, a through hole 13 is formed under the strong pressure of the extrusion nail, the dot-shaped protrusions 24 on the front circuit layer 21 and the back circuit layer 22 are in contact at the position of the through hole 13 to realize contact conduction, the extrusion is completed, the mold is opened, then solder resist ink 32 is manufactured on the surface of the front circuit layer 21, the manufacturing of the solder resist ink is a conventional technology in the field, the repeated description is omitted, and the structure shown in fig. 7-2 is obtained; and carrying out a line power connection test.

Example 3:

the difference from the embodiment 2 is that the extrusion nails on the upper die and the lower die are arranged in a staggered manner, specifically referring to fig. 12-2, the extrusion pressure is controlled to be 50kg, after the dies are closed, the extrusion nails extrude punctiform protrusions 24 on the front surface circuit layer 21, the punctiform protrusions 24 pierce the middle insulation layer 1 to form through holes 13, and the punctiform protrusions 24 are in contact conduction with the back surface circuit layer 22 at the positions of the through holes 13; similarly, the dot-shaped protrusion 24 on the back circuit layer 22 pierces the intermediate insulating layer 1 to form the through hole 13, and the dot-shaped protrusion 24 is in contact with and in communication with the front circuit layer 21 at the position of the through hole 13.

Example 4:

the difference from the embodiment 2 is that the extrusion nails of the upper die and the lower die are partially arranged in a right-hand way and partially arranged in a staggered way, and particularly, as shown in fig. 12-4 or fig. 12-5, the extrusion pressure is controlled to be 35kg, and the extrusion nails are not subjected to heating treatment.

Example 5:

providing a double-layer flexible circuit board, wherein the double-layer flexible circuit board comprises a middle insulation layer 1 and metal circuit layers positioned at two sides of the middle insulation layer, wherein solder mask covering films (covering films known in the field) are manufactured on two sides of the double-layer flexible circuit board, a front circuit layer 21 is a copper circuit layer, a back circuit layer 22 is an aluminum circuit layer, a middle insulation layer 1 is a PET film with glue, the double-layer flexible circuit board is heated to 160 ℃ in the whole board, and the PET resin film and the glue of the middle insulation layer are in a softened state;

installing an extrusion die on an extruder, wherein an upper die belt and a lower die of the die are both provided with extrusion nails, the extrusion nails on the upper die and the lower die are all arranged oppositely, the lower die is provided with pipe position nails, a double-layer flexible circuit board is provided with pipe position holes, the pipe position holes on the double-layer flexible circuit board are sleeved on the pipe position nails of the lower die, at the moment, the extrusion nails are just aligned to the positions on the circuit board where punctiform dents need to be made, 25 extrusion nails are arranged at each conducting position and are in 5-by-5 layout, the maximum diameter of the extrusion nails is 1.5mm, closing the die, controlling the extrusion pressure to be 73kg, the extrusion time to be 0.8s, the extrusion nails act on the solder mask and simultaneously extrude the front circuit layer 21 and the back circuit layer 22 to the middle insulating layer 1, the solder mask layer is subjected to the extrusion force of the extrusion nail and transmits the extrusion force to the metal circuit layer, wherein a point-shaped dent 23 is formed at the position, extruded by the extrusion nail, of the upper surface of the front circuit layer 21, a point-shaped bulge 24 is correspondingly formed at the lower surface of the front circuit layer 21, a point-shaped recess 31 is formed on the front solder mask layer corresponding to the point-shaped dent position, a point-shaped dent 23 is formed at the position, extruded by the extrusion nail, of the lower surface of the back circuit layer 22, a point-shaped bulge 24 is formed at the corresponding position of the upper surface, a point-shaped recess 31 is formed on the back solder mask layer corresponding to the point-shaped dent position, the extrusion nail pushes the point-shaped bulge 24 to extrude the middle insulating layer to form a through hole 13, the point-shaped bulges 24 on the front circuit layer 21 and the back circuit layer 22 are contacted at the through hole position, so that contact conduction is realized, the extrusion is completed, and the die is opened; and carrying out a line power connection test.

In the above embodiment, the double-layer flexible printed circuit board is heated wholly or locally to soften the intermediate insulating layer 1, and the intermediate insulating layer 1 can be more easily broken by the pressing nail to form the through hole 13, and it is understood that the heating process is not essential, and the intermediate insulating layer 1 can be broken at normal temperature to form the through hole 13.

The double-layer flexible circuit board is placed in a die, wherein at least one surface of the die is provided with an extrusion nail, at least one metal circuit layer is extruded to the middle insulating layer 1 by the extrusion nail, the extrusion nail is extruded on the surface of the metal circuit layer to form a point-shaped dent 23, the other surface corresponding to the point-shaped dent 23 is provided with a point-shaped bulge 24, the middle insulating layer 1 is simultaneously extruded by the extrusion nail to form a through hole 13, so that the point-shaped bulge is in contact with the opposite metal circuit layer at the position of the through hole 13, contact conduction is realized, the mode of realizing conduction of the two circuit layers by electroplating copper, conductive glue or conductive ink, solder paste reflow soldering and the like in the prior art is abandoned, the mode is completely different from the mode of realizing conduction of the two metal circuit layers by additionally arranging a conductive medium in the prior art, the conduction mode is not required to be prepared on the wire in advance as in the prior art, the middle insulating layer 1 is extruded by the extrusion nail to form the through hole 13 when the point-shaped dent 23 and the point-shaped bulge 24 are prepared, the conduction mode is obviously simplified, the problem of environmental pollution caused by the existence of conductive medium in the existence of the existing technology does not exist, the point-shaped bulge 24, the double-shaped flexible circuit board can be kept in close contact with good consistency, the double-layer flexible circuit board, and the product can be used for the double-layer flexible circuit board, and the product can be stably connected with long service life, and the product can be used in the product.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims

1. A double-layer flexible circuit board is characterized in that: the circuit board comprises a middle insulating layer and metal circuit layers positioned on two sides of the middle insulating layer, wherein the surface of at least one metal circuit layer is provided with a point-shaped dent, the position of the other surface of the metal circuit layer, corresponding to the point-shaped dent, is provided with a point-shaped bulge, the position of the middle insulating layer, corresponding to the point-shaped bulge, is provided with a through hole, and the metal circuit layers on two sides are in contact conduction through the point-shaped bulge at the through hole position.

2. The double-layer flexible wiring board of claim 1, wherein: the circuit board is provided with at least one conducting position, and the number of the point-shaped dents is more than 2 at each conducting position.

3. The double-layer flexible wiring board of claim 1, wherein: the point-shaped dents are arranged on one of the metal circuit layers, or the point-shaped dents are arranged on the two metal circuit layers, and the point-shaped protrusions are in contact conduction with the opposite metal circuit layer at the through hole positions.

4. The double-layer flexible wiring board of claim 3, wherein: the two layers of metal circuit layers are provided with point-shaped dents, and the point-shaped dents on the two layers of metal circuit layers are arranged in an alignment mode, or in a staggered mode, or in a partial alignment mode, and in a partial staggered mode.

5. The double-layer flexible wiring board of claim 1, wherein: at the point-shaped dent, a perforation is formed on part or all of the metal, and the perforation penetrates through the metal circuit layer where the point-shaped dent is located; or the through holes penetrate through the two metal circuit layers, and the through holes on the two metal circuit layers are aligned.

6. The double-layer flexible wiring board of claim 5, wherein: the point-shaped bulges at the perforating positions form an annular structure, and the metal of the annular structure is in contact conduction with the opposite metal circuit layer at the through hole positions.

7. The double-layer flexible wiring board of claim 1, wherein: the middle insulating layer at the position of the through hole is hooped on the point-shaped bulge, and the point-shaped bulge and the opposite metal circuit layer form stable contact conduction.

8. The double-layer flexible wiring board of claim 1, wherein: the opening width of the dot-shaped dents is less than or equal to 1.5mm.

9. The double-layer flexible wiring board according to any one of claims 1 to 8, wherein: a solder mask is arranged on the metal circuit layer, a point-shaped recess is formed in the solder mask which covers the metal circuit layer with the point-shaped dent, and the point-shaped recess corresponds to the point-shaped dent; or the solder mask covered on the metal circuit layer with the dot-shaped dents does not have dot-shaped dents at the positions of the dot-shaped dents; or the solder mask on one metal circuit layer is provided with point-shaped depressions corresponding to the point-shaped dents of the metal circuit layer, and the solder mask on the other metal circuit layer is not provided with the point-shaped depressions.

10. The double-layer flexible wiring board of claim 8, wherein: the solder mask layer is solder mask ink or a solder mask film.

11. The double-layer flexible wiring board of claim 1, wherein: the metal circuit layer is a copper metal layer, or an aluminum metal layer, or a copper-aluminum composite metal layer.

12. The double-layer flexible wiring board of claim 11, wherein: the two metal circuit layers are the same metal layer or different metal layers.

13. An electronic product, characterized in that: a double-layer flexible wiring board comprising the double-layer flexible wiring board according to any one of claims 1 to 12, on which electronic components are soldered.

14. An electronic product according to claim 13, wherein: the electronic product is a lighting lamp.

15. A conduction method of a double-layer flexible circuit board is characterized by comprising the following steps:

the double-layer flexible circuit board is placed in a die, wherein at least one side of the die is provided with an extrusion nail, at least one metal circuit layer is extruded to the middle insulating layer by the extrusion nail, the surface of the metal circuit layer is extruded by the extrusion nail to form a point-shaped dent, the other surface of the metal circuit layer forms a point-shaped bulge corresponding to the point-shaped dent, the middle insulating layer is simultaneously extruded by the extrusion nail to form a through hole, so that the point-shaped bulge is in contact with the opposite metal circuit layer at the through hole position, and the contact conduction is realized.

16. The conduction method of the double-layer flexible circuit board according to claim 15, characterized in that: one side of the die is provided with an extrusion nail, the other side of the die is a plane, and the extrusion nail extrudes one of the metal circuit layers to obtain a point-shaped dent and a point-shaped bulge; or the two sides of the die are provided with extrusion nails which simultaneously extrude the two metal circuit layers in the die, so that point-shaped dents and point-shaped bulges are formed on the two metal circuit layers.

17. The conduction method of the double-layer flexible circuit board according to claim 16, characterized in that: the extrusion nails on the two sides of the die are arranged oppositely; or the extrusion nails on the two sides of the die are arranged in a staggered manner; or the extrusion nail parts on the two sides of the die are arranged oppositely, and the parts are arranged in a staggered way.

18. The conduction method of the double-layer flexible circuit board according to claim 15, characterized in that: more than 2 extrusion nails are arranged on one surface of the die, which is provided with the extrusion nails.

19. A method for connecting a double-layer flexible wiring board according to any one of claims 15 to 18, wherein: the double-layer flexible circuit board is a fully bare circuit board, and after the extrusion step is completed, the solder mask layer is manufactured on the two metal circuit layers.

20. A method for connecting a double-layer flexible wiring board according to any one of claims 15 to 18, wherein: the double-deck flexible line way board that provides all has the circuit board of solder mask for both sides, in the mould, utilizes extrusion nail extrusion solder mask, transmits the extrusion force of extrusion nail for metal circuit layer through the solder mask for form punctiform sunken on the solder mask, correspond punctiform sunken position on the metal circuit layer and form punctiform dent and punctiform arch.

21. A method of connecting a two-layer flexible wiring board according to any one of claims 15 to 18, wherein: the provided double-layer flexible circuit board is a semi-bare circuit board, one surface of the circuit board is a bare circuit, the other surface of the circuit board is provided with a solder mask, and after the extrusion step is completed, the solder mask is manufactured on a metal circuit layer of the bare circuit.

22. The conduction method of the double-layer flexible circuit board according to claim 15, characterized in that: heating the whole board or the local part of the provided double-layer flexible circuit.