CN116390362A

CN116390362A - Double-layer flexible circuit board and manufacturing method thereof

Info

Publication number: CN116390362A
Application number: CN202111680248.3A
Authority: CN
Inventors: 王定锋; 代宏信; 徐磊; 宋健; 夏鹏; 郑英杰; 明瑞; 徐文红
Original assignee: Tongling Guozhan Electronic Co ltd
Current assignee: Tongling Guozhan Electronic Co ltd
Priority date: 2021-12-26
Filing date: 2021-12-26
Publication date: 2023-07-04

Abstract

The invention relates to a double-layer flexible circuit board and a manufacturing method thereof, in particular to a copper-clad plate with an adhesive coated on the back surface of a whole roll, which is punched with a plurality of holes by a die roll to roll, polished to remove burrs on the edges of the holes, and then attached to a single-layer circuit board or copper foil to be pressed into a whole; or cutting a whole roll of copper-clad plate with adhesive coated on the back into short copper-clad plates with adhesive less than or equal to 2 meters, overlapping a plurality of short copper-clad plates together, drilling, arranging and pasting the short copper-clad plates after drilling on a single-layer long circuit board or a long copper foil with the length more than 2 meters end to end, filling the gap between two adjacent short copper-clad plates with insulating resin, and pressing into a whole. And (3) processing the hole wall to attach a layer of conductive object, electroplating a layer of copper, connecting and conducting the two layers of metal by the electroplated copper on the hole wall, and etching the surface copper foil layer by an etching method to manufacture the metal circuit. And manufacturing the double-layer flexible circuit board.

Description

Double-layer flexible circuit board and manufacturing method thereof

Technical Field

The invention relates to the field of circuit boards, in particular to a double-layer flexible circuit board and a manufacturing method thereof.

Background

The modern manufacturing industry is developed towards full-automatic and intelligent production and management, the product and accessory manufacturing of the electronic industry is not exceptional, the electronic industry is developed towards full-automatic and intelligent, a circuit board is one of the most important basic accessories of the electronic product, along with the pursuit of light weight and flexibility of the electronic product, the electronic product manufactured by using the flexible circuit board is increasingly popular, and the flexible circuit board is popular in products such as mobile phones, pen computers, LED lamp bands and the like.

At present, the production of double-layer flexible circuit boards mainly adopts single-chip operation, and adopts a chip production mode for production, and the automation degree and the efficiency are low. The full-automatic production of the flexible circuit board is realized by adopting long coil materials, the whole production process is called coil-to-coil production in the industry, and the production mode can realize high-efficiency full-automatic production, and has the advantages of high production efficiency, short production period and low cost.

The flexible circuit board is also divided into: a flexible wiring board of a single-layer wiring, a flexible wiring board of a double-layer wiring, and a flexible wiring board of a multi-layer wiring. The largest amount of use is the flexible circuit board of single-layer circuit and double-layer circuit. The flexible circuit board of the single-layer circuit has simple relative production process, and has already realized full-automatic production in a full-flow roll-to-roll mode, however, the double-layer flexible circuit board has not realized production in a large-batch full-scale roll-to-roll mode all the time in the industry, and the main technical difficulty is in the production link of drilling.

Conventionally, double-layer flexible circuit boards have been difficult to produce roll-to-roll, and even if they can be produced roll-to-roll, they have been very inefficient and costly. The reasons are as follows:

After the double-layer flexible circuit board is drilled, metallized holes (mainly copper metallized holes) are formed on the resin surface of the hole wall, so that the upper layer circuit and the lower layer circuit are conducted through the hole wall metal.

Drilling can only be performed by mechanical drilling or laser drilling, and the prior art drilling machines in the mechanical drilling mode can only drill short plates below 2 meters, so that the drilling is efficient, because up to 15 short plates are stacked (shown in fig. 1) for drilling the short plates below 2 meters at the same time. For long plates exceeding 2 meters. If the prior art mechanical drilling machine or the laser drilling machine is used for roll-to-roll drilling, the two drilling modes are difficult to realize that a plurality of roll plates are stacked together, then continuous roll-to-roll drilling can only be carried out by single roll plates (shown in figure 2), the efficiency of drilling long plates with more than 2 meters is very low! The cost is high. The drilling output in unit time is actually compared on a drilling machine, and the total area of the drilling machine for drilling short plates lower than one meter is more than 15 times of the total area of long plates with more than one meter according to the sum of areas of drilling outputs. The drilling machine in the circuit board industry is very expensive equipment, one 6-axis machine is more than 150 ten thousand yuan, and if the long double-layer circuit board with the length of more than one meter is produced by the prior process technology, compared with the short double-layer circuit board with the length of less than one meter, the same yield is produced, the investment of the drilling machine is improved by 15 times, and the corresponding cost of the manual electric charge field and the like is also improved by 15 times. If a laser drilling machine is used for drilling holes, more than 300 ten thousand yuan is needed for one laser drilling machine with two ends, and a plurality of layers of copper-clad plates are stacked together for drilling, the following is more difficult! The reason is that after the multilayer copper-clad plate is overlapped, the total thickness of copper is too thick, and laser drilling is difficult. For this reason, long double-layer circuit boards of more than 2 meters cannot be produced widely worldwide so far, and only small amounts of spot samples or small batches are not counted.

Of course, it is first thought why do not use continuous automatic punches, do it replace the driller with die roll-to-roll continuous punching (shown in fig. 3)? The reason is that the copper-clad plate is punched by the die and burrs are generated, the copper-clad plate punched with double-layer copper always has burrs of one copper surface, the burrs rolled into the holes (4.1 of burrs shown in fig. 4) cannot be polished, the burrs rolled into the holes float on the hole walls, holes (shown in fig. 5) are formed after the hole walls of the circuit board are plated with copper, and when the circuit board is used, air expansion in the holes causes copper cracking on the hole walls during high-temperature soldering tin. Therefore, the copper-clad plate with double layers of copper cannot be punched by a die to replace a drilled hole, and then is used for manufacturing a circuit board with double layers of circuits.

Not only is the flexible circuit board produced in a roll-to-roll production manner required in the production and manufacturing process, so that high-efficiency automation can be realized, but also some products per se need long circuit boards with the length exceeding 1 meter, such as LED lamp strip products which are generally used for a period exceeding 5 meters. The lamp strip product is highly desirable to be fabricated with very long flexible circuit boards. The demand for the rapid development of LED lamp strips and LED flexible display screens has been very large in the years, and the demand for flexible circuit boards has reached tens of millions of square meters. And both products are more than 1 meter, however, the long lamp belts manufactured by the prior art with the length of more than 1 meter are manufactured by using the short circuit board with the length of not more than 1 meter, and then are connected into the long lamp belts with the length of more than 1 meter for use, and the connection positions of the long lamp belts manufactured by the method are unreliable.

How to realize the high-efficiency roll-to-roll production of the double-layer flexible circuit board is critical to how to realize the high-efficiency manufacture of the via hole of the double-layer flexible circuit board, and also to form the roll-to-roll continuous production.

The invention provides four methods, and the four methods are used for realizing the efficient continuous roll-to-roll production of the double-layer flexible circuit board. And simultaneously, the flexible circuit board with the length of more than 1 meter is produced.

1. A method for manufacturing a double-layer flexible circuit board includes such steps as preparing a single-layer flexible circuit board with length greater than 1 m, winding, coating adhesive layer on the back of single-layer copper-clad plate with length greater than 1 m, winding, punching copper surface by mould, generating copper burrs on the hole edge, grinding copper burrs by sand wheel grinder, laminating the copper-clad plate with adhesive layer on the back, and metal circuit on single-layer circuit board, exposing, preparing a conductive object, plating copper layer, connecting copper layer, etching, and preparing a solder mask layer.

2. A method for manufacturing a double-layer flexible circuit board includes such steps as coating adhesive on back of a single-layer copper-clad plate with length greater than 1 m to form an adhesive layer, punching holes on a continuous punch machine for making copper face downward, generating copper burrs on the hole edges, grinding copper burrs by sand wheel grinder (figure 9 and figure 10), laminating copper-clad plate with adhesive layer on back of hole edges, adhering copper foil, exposing metal on copper foil from hole position, making a layer of electric conductor on hole wall, electroplating copper to make hole wall plated with a layer of copper, connecting two layers of copper foil, etching to form two layers of circuit, and making a double-side solder mask.

3. A method for manufacturing a double-layer flexible circuit board includes such steps as preparing a long single-layer flexible circuit board with length greater than 2 m, printing multiple insulating resin inks on the bottom layer of the single-layer flexible circuit board, baking to solidify the inks, coating adhesive on back of the single-layer copper flexible copper-clad plate, cutting to obtain multiple short copper-clad plates with length b, stacking multiple short copper-clad plates, drilling, arranging multiple short copper-clad plates, sticking the short copper-clad plates on the long single-layer flexible circuit board, sticking insulating resin inks at the gaps between two adjacent short copper-clad plates, sticking the lower metal wires from holes, making a layer of conductive object, plating copper on the hole wall, forming a conducting connection layer by using metal of the bottom layer and copper on the copper-clad plate, etching the copper-clad plate, and making a large-size solder mask layer on the upper copper-clad plate.

4. A method for manufacturing a double-layer flexible circuit board includes the steps of coating adhesive on the back of a single-layer copper-clad plate by a roll-to-roll adhesive coating method, cutting into a plurality of short copper-clad plates smaller than b meters, stacking the short copper-clad plates together, drilling holes on a drilling machine, adhering a plurality of insulating resin strips containing adhesive on the surface of a long copper foil larger than 2 meters, enabling the center distance between two adjacent resin strips to be a meters, b is smaller than or equal to 2 meters, arranging the plurality of the drilled short copper-clad plates with adhesive to be adhered on a long copper foil with the length larger than 2 meters in an end-to-end mode, enabling gaps between the two adjacent short copper-clad plates to be provided with resin strips to cover the copper foil at the gaps, enabling the positions of the holes of the short copper-clad plates to face to be exposed out of copper, bonding the long copper foil and the short copper-clad plates with holes firmly through pressing, manufacturing a layer of conductive object on the hole wall, electroplating copper to enable the copper on the hole wall to form conducting connection between the long copper foil and all the short copper-clad plates with all short copper-clad plates, manufacturing a double-layer flexible circuit board with at least two layers of a double-layer flexible solder-resisting layer on a circuit board, manufacturing a double-layer flexible solder-resisting circuit board with at least two layers.

The four methods respectively solve the technical problems in the industry, not only realize the full-automatic full-process high-efficiency roll-to-roll production of the double-layer flexible circuit board, but also realize the low-cost manufacture of the circuit board with the long double-layer circuit exceeding 2 meters.

Disclosure of Invention

The invention relates to a manufacturing method of a double-layer flexible circuit board, in particular to a manufacturing method of a single-layer flexible circuit board with the length of more than 1 meter, which comprises the steps of firstly manufacturing a single-layer flexible circuit board with the length of more than 1 meter, coiling, then coating a layer of adhesive on the back surface of a single-layer copper-clad plate with the length of more than 1 meter to form an adhesive layer, coiling, installing a die on a roll-to-roll continuous punching machine, arranging a plurality of punching needles in the upper die, arranging a plurality of holes corresponding to the punching needles in the lower die, keeping the copper surface downwards, punching by using the die, generating copper burrs on the punched hole edge, grinding the copper burrs outwards by using a sand wheel grinding machine, laminating the copper-clad plate with the adhesive layer on the back surface of the ground hole edge, laminating the single-layer flexible circuit board together by using a roll-to-roll laminating compound machine, forming a lower layer circuit layer in the middle by clamping a metal circuit on the single-layer circuit board, exposing from the hole positions, manufacturing a conductive layer on the hole wall, manufacturing a copper-clad plate, etching a copper-clad plate, and manufacturing a copper-clad plate with a large-layer, and a copper-plated layer, and a manufacturing method.

The invention provides a manufacturing method of a double-layer flexible circuit board, which comprises the steps of coating adhesive on the back of a single-layer copper-clad plate with the length of more than 1 meter to form an adhesive layer, mounting a die on a roll-to-roll continuous punching machine, wherein the die is formed by combining the upper die and the lower die, a plurality of punching pins are arranged in the upper die, a plurality of holes corresponding to the upper punching pins are arranged in the lower die, the copper face is kept downwards, the punched holes are provided with copper burrs, the copper burrs are all in the copper face direction and are outwards convex, a sand wheel plate mill is used for grinding the copper burrs, the copper-clad plate with the adhesive layer on the back of the copper burrs with the hole side and the copper foil with the length of more than 1 meter are stacked together, the copper foil with the hole side burrs is firmly bonded through pressing, a layer of conductive material is manufactured on the hole wall, then the hole wall is plated with one layer of copper, the two layers are connected and conducted through the hole wall copper, two layers are manufactured through an etching method, two layers of solder masks are manufactured, and at least one layer of solder masks is provided with a double-layer copper-clad plate with a window, and the flexible circuit board is manufactured with the size of more than 1 meter.

There is also provided a double-layer flexible circuit board according to the present invention, including: a lower solder mask layer; a lower wiring layer; an intermediate insulating layer; an upper wiring layer; an upper solder mask layer; the double-layer flexible circuit board is characterized in that layers of the double-layer flexible circuit board are arranged and combined together according to the following sequence, namely, a lower circuit layer is combined on a lower circuit layer, an intermediate insulating layer is combined on the lower circuit layer, an upper circuit layer is combined on the intermediate insulating layer, the upper circuit layer is combined on an upper circuit layer, the double-layer flexible circuit board is a flexible circuit board with the length being more than 1 meter, a plurality of holes are formed in the double-layer flexible circuit board, conduction between the upper circuit layer and the lower circuit layer is formed by metal copper combined on a hole wall, the holes are characterized in that the upper circuit layer and the intermediate insulating layer penetrate through the lower circuit layer, a plurality of windows are formed in the upper circuit layer, and all or part of the holes are covered by the front circuit layer.

The invention also provides a manufacturing method of the double-layer flexible circuit board, and specifically, firstly, manufacturing a single-layer flexible circuit board, wherein the length of the single-layer flexible circuit board is larger than 2 meters, the circuit layer of the single-layer flexible circuit board is a bottom circuit layer of the double-layer circuit board, a plurality of insulating resin ink is printed on the bottom circuit layer, the ink is cured by baking to form insulating resin strips, the center distance between two adjacent insulating resin strips is a, then, a single-layer copper flexible copper-clad plate is coated with an adhesive on the back, a plurality of short copper-clad plates are cut into a plurality of short copper-clad plates, the lengths of the short copper-clad plates are b and less than or equal to a, a plurality of short copper-clad plates are stacked together, the short copper-clad plates are drilled by a drilling machine and then are arranged and attached to the long single-layer flexible circuit board in an end-to-end mode, the insulating resin ink is arranged at a gap between the two adjacent short copper-clad plates, a lower metal circuit is upwards exposed from the hole, the single-layer flexible circuit board and the single-layer copper-clad plate are firmly combined by a press, a conductive object is manufactured on the hole wall, then, copper is plated to form a copper layer, the copper-clad plate is coated on the hole wall, the copper-clad plate is manufactured, the copper layer is connected with the copper layer, and the copper-clad layer is manufactured by etching, and the copper layer is manufactured by the copper layer.

The invention also provides a manufacturing method of the double-layer flexible circuit board, and particularly, the single-layer copper flexible copper-clad plate is glued on the back by adopting a roll-to-roll gluing method, a plurality of short copper-clad plates smaller than b meters long are cut into a plurality of short copper-clad plates, the short copper-clad plates are stacked together, the double-layer flexible circuit board is used after drilling on a drilling machine, a plurality of insulating resin strips containing glue are attached to the surface of the copper foil with the length of more than 2 meters, the center distance between every two adjacent resin strips is a meter, b is less than or equal to 2 meters, the plurality of the drilled short copper-clad plates with glue are arranged end to end on the copper foil with the length of more than 2 meters, gaps are reserved between every two adjacent short copper-clad plates, the resin strips cover the copper foil at the gaps, the long copper foil with the length of more than 2 meters are exposed towards the front surface at the hole position of the short copper-clad plates, the copper foil and the short copper-clad plates with holes are firmly bonded by pressing, a layer of conductive material is manufactured on the hole wall, then the copper-clad plate is plated with one layer of copper, the copper foil and all the short copper-clad plates are connected by etching, at least two layers of the double-layer flexible circuit board is manufactured, and a solder-resisting layer is manufactured.

There is also provided a double-layer flexible circuit board according to the present invention, including: a lower solder mask layer; a lower wiring layer; an intermediate insulating layer; an upper wiring layer; an upper solder mask layer; the double-layer flexible circuit board is characterized in that layers of the double-layer flexible circuit board are combined together in a sequence that a lower layer circuit layer is combined on a lower layer solder mask layer, an intermediate insulating layer is combined on the lower layer circuit layer, an upper layer circuit layer is combined on the intermediate insulating layer, the upper layer solder mask layer is combined on an upper layer circuit layer, the lower layer circuit layer is a continuous long circuit layer, the length of the lower layer circuit layer is greater than 2 meters, the upper layer circuit layer is a multi-section short circuit layer, the length of each section of the upper layer circuit layer is less than or equal to 2 meters, a plurality of holes are formed in the double-layer circuit board, the holes pass through the upper layer circuit layer and the intermediate insulating layer, but do not pass through the lower layer circuit layer, all or part of the holes are covered by the solder mask layer, the upper layer circuit layer and the lower layer circuit layer are connected by copper on the upper layer and lower layer circuit layer through metal copper combined on a hole wall, the upper layer solder mask layer is provided with a plurality of windows, and a plurality of metal pads are formed on the upper layer circuit layer.

According to a preferred embodiment of the present invention, the double-layer flexible circuit board is characterized in that LEDs or LEDs and control elements can be soldered on the double-layer flexible circuit board to form a double-layer circuit board LED strip.

According to a preferred embodiment of the present invention, the double-layer flexible circuit board is characterized in that the lower circuit layer is a copper circuit layer, or a copper-clad aluminum circuit layer, or a copper-aluminum composite circuit layer.

According to a preferred embodiment of the present invention, the double-layer flexible circuit board is characterized in that the lower solder resist layer or the upper solder resist layer is a coverlay film solder resist layer or an ink solder resist layer.

According to a preferred embodiment of the present invention, the lower solder mask layer is a coverlay solder mask layer, and the upper solder mask layer is a coverlay solder mask layer or an ink solder mask layer.

According to a preferred embodiment of the present invention, the double-layer flexible circuit board can be used by cutting the long flexible circuit board into short circuit boards smaller than or equal to 1 meter.

According to a preferred embodiment of the present invention, the LED strip with a double-layer circuit board is characterized in that the LED is an LED flip chip, or an LED CSP device, or an LED bead with an LED chip packaged on a support.

According to a preferred embodiment of the present invention, the double-layer flexible circuit board is characterized in that the gap between the two adjacent upper circuit layers is filled with metal copper for connecting the two adjacent upper circuit layers, or no metal copper is filled in the gap between the two adjacent upper circuit layers, and the two adjacent upper circuit layers are completely disconnected.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below.

Drawings

The features, objects, and advantages of the present invention will become more apparent from the detailed description read in conjunction with the following drawings, a brief description of which follows.

Fig. 1 is a schematic view of a short copper clad laminate Zhang Zuankong.

Fig. 2 is a schematic diagram of a full roll copper clad laminate roll-to-roll section-to-section drilling.

Fig. 3 is a schematic diagram of a die for making holes by roll-to-roll punching of single or double layer copper clad laminates on a continuous punch press.

Fig. 4 is a schematic cross-sectional view of the punched double-layer copper-clad plate expressed in fig. 3, which rolls copper burrs 4.1 into and out of the hole.

Fig. 5 is a schematic cross-sectional view of the burr 4.1 expressed in "fig. 4" to form a floating copper (void) 5.1 in the hole wall when the hole wall copper is manufactured.

Fig. 6 is a schematic plan view of the lower circuit layer 6 of the flat cable manufactured on the flat cable machine, in which the lower circuit layer 6 is manufactured by etching the single-sided flexible copper-clad plate, and the etched circuit 6.1 and the lower solder mask layer 6.2, or a plurality of flat copper wire circuits 6.1 and a layer of film with glue are also the lower solder mask layer 6.2.

Fig. 7 is a schematic view of a flat copper wire used for the lower wiring layer 6 made of the flat wire expressed by "fig. 6".

Fig. 8 is a schematic plan view of the adhesive single-layer copper-clad plate with a plurality of holes made by the expression of "fig. 3".

Fig. 9 is a schematic cross-sectional view of a plurality of hole-coated copper clad laminate of fig. 8, punched with a die on a roll-to-roll continuous punch of fig. 3, with copper burrs facing downward.

Fig. 10 is a schematic cross-sectional view of the outward burr of "fig. 9" being ground away with a sand wheel plate grinding machine.

The glued copper-clad plate expressed by the figure 11 and the lower circuit layer expressed by the figure 6 form a schematic cross section of the composite board.

Fig. 12 is a partially enlarged schematic cross-sectional view of the composite plate 11a expressed in "fig. 11".

FIG. 13 is a schematic cross-sectional view of a portion of the expression "FIG. 12" after copper plating.

Fig. 14 is a schematic plan view of the upper layer circuit 14.1 of the combined circuit board shown in fig. 11, after copper plating shown in fig. 13, by etching.

Fig. 15 is a schematic plan view of the fabrication of an upper solder mask layer with a plurality of pad windows 15.1 on the upper layer of circuitry expressed in fig. 14.

Fig. 16 is a schematic plan view of a lamp strip manufactured by SMT soldering LED beads or die bonding with a die bonder and resistor 16.1 on a bonding pad window as expressed in "fig. 15".

Fig. 17 is a schematic cross-sectional view of a double-layer flexible wiring board on which the expression "fig. 15" is attached.

Fig. 18 is a schematic cross-sectional view of the light strip expressed in "fig. 16".

Fig. 19 is a schematic plan view of a single-layer copper-clad laminate with adhesive having a plurality of holes produced by the method of "fig. 3".

Fig. 20 is a schematic cross-sectional view of a multi-hole, glued single-layer copper-clad plate of fig. 19, punched with a die on a roll-to-roll continuous punch of fig. 3, with copper burrs facing downward.

Fig. 21 is a schematic cross-sectional view of the outward burr of "fig. 20" being ground away with a sand wheel plate grinding machine.

Fig. 22 is a schematic cross-sectional view of a combined double layer board in which the multi-hole glued single layer copper-clad plate and the lower copper foil are covered together as expressed in fig. 19.

Fig. 23 is a partially enlarged schematic cross-sectional view of the assembled double-layer board 21a expressed in "fig. 22".

FIG. 24 is a schematic sectional view of a part of the expression "FIG. 21" after copper plating.

Fig. 25 is a schematic plan view of the upper wiring layer formed by etching the copper-plated composite double-layer plate expressed by "fig. 24".

FIG. 26 is a schematic cross-sectional view of the copper-plated composite double layer plate of FIG. 24 after etching to form an underlying circuit.

Fig. 27 is a schematic plan view of the upper solder mask layer with a plurality of pad windows 15.1 formed on the upper wiring layer as shown in fig. 25.

Fig. 28 is a schematic plan view of a lamp strip formed by SMT soldering LED beads or die attach chip and resistor 16.1 on the pad window shown in fig. 27.

Fig. 29 is a schematic cross-sectional view of the double-layer flexible wiring board expressed as "fig. 27".

Fig. 30 is a schematic cross-sectional view of the light strip expressed in "fig. 28".

Fig. 31 is a schematic plan view of the lower circuit layer 6 of the flat cable manufactured on the flat cable machine by etching the single-sided flexible copper-clad plate to manufacture the lower circuit layer 6, etching the circuit 6.1 and the lower solder mask layer 6.2, or simultaneously forming a plurality of flat copper conductor circuits 6.1 and a layer of film with glue into the lower solder mask layer 6.2.

Fig. 32 is a schematic view of a flat copper wire 6.1 for the lower wiring layer 6 made of the flat wire expressed by "fig. 31".

Fig. 33 is a schematic view of a short single layer copper clad laminate Zhang Zuankong.

Fig. 34 is a schematic plan view of a single Zhang Duan copper-clad plate made by "fig. 33" expressing stacked drilling.

Fig. 35 is a schematic plan view of the lower wiring layer printed multi-stage insulating resin adhesive tape expressed by "fig. 31".

Fig. 36 is a schematic plan view of the short single-layer copper-clad plate expressed in fig. 34, aligned and attached to the lower layer circuit layer combined double-layer plate with the insulating resin adhesive tape expressed in fig. 35.

Fig. 37 is a schematic cross-sectional view of the combined double-layer panel expressed in "fig. 36".

Fig. 38 is a partially enlarged schematic cross-sectional view of the assembled double-layer panel 37a expressed in "fig. 37".

FIG. 39 is a schematic cross-sectional view of the copper foil after partial copper plating as shown in FIG. 38.

Fig. 40 is a schematic plan view of the combined bilayer board etched to form the upper wiring layer as expressed in "fig. 39".

Fig. 41 is a schematic cross-sectional view of the combined double-layer board 37b shown in fig. 37 after copper plating, in the gap between two adjacent upper line layers, there is metallic copper connecting the two adjacent upper line layers to form a connection via.

Fig. 42 is a schematic diagram of a connection between two adjacent upper circuit layers in the gap between two adjacent upper circuit layers shown in fig. 41.

Fig. 43 is a schematic cross-sectional view of a fully broken circuit between two adjacent upper circuit layers, with the combined double layer plate 37b of fig. 37 being etched to form a metal free copper connection via in the gap between the two adjacent upper circuit layers after copper plating.

Fig. 44 is a schematic diagram showing a completely broken line between two adjacent upper line layers of the section "fig. 43".

Fig. 45 is a schematic plan view of the upper layer solder mask layer with a plurality of pad windows 15.1 formed on the upper layer circuit expressed in fig. 40.

Fig. 46 is a schematic plan view of a lamp strip formed by SMT soldering LED beads or die attach chip and resistor 16.1 on the pad window shown in fig. 45.

Fig. 47 is a schematic cross-sectional view of the double-layer flexible wiring board expressed by "fig. 45".

Fig. 48 is a schematic cross-sectional view of the light strip of fig. 46.

Fig. 49 is a schematic plan view of an insulating tape 49.1 fabricated on a copper foil 49 at equal intervals.

Fig. 50 is a schematic view of a short copper clad laminate Zhang Zuankong.

Fig. 51 is a schematic plan view of a single Zhang Duan single-layer copper-clad plate made by "fig. 50" expression fold-open drilling.

Fig. 52 is a schematic plan view of the short single-layer copper-clad plate expressed in fig. 51, which is attached to the insulating resin adhesive tape 49.1 expressed in fig. 49 in a head-to-tail alignment manner.

Fig. 53 is a schematic cross-sectional view of a composite board of the short single-layer copper-clad laminate of fig. 52 attached to a copper foil with an insulating resin tape.

Fig. 54 is a partially enlarged schematic cross-sectional view at 53a of the expression "fig. 53".

FIG. 55 is a schematic cross-sectional view of the copper foil after partial copper plating as shown in FIG. 54.

Fig. 56 is a schematic plan view of the upper circuit layer formed by etching the composite board expressed by "fig. 55".

Fig. 57 is a schematic plan view of the pattern plate etched to form the underlying wiring layer as expressed in "fig. 55".

Fig. 58 is a schematic cross-sectional view of the combined double-layer board 53b of fig. 53 in the gap between two adjacent upper circuit layers in the etched circuit after copper plating, where the metal copper connecting the two adjacent upper circuit layers forms a connection via.

Fig. 59 is a schematic diagram of a connection between two adjacent upper line layers in the gap between the two adjacent upper line layers shown in fig. 58, where copper is used to connect the two adjacent upper line layers.

Fig. 60 is a schematic cross-sectional view of a circuit formed by etching a combined double-layer board 53b shown in fig. 53 after copper plating, in a gap between two adjacent upper circuit layers, which is etched to form a metal-free copper connection via, and a completely disconnected circuit between the two adjacent upper circuit layers.

Fig. 61 is a schematic diagram of a completely broken line between two adjacent upper line layers of the section "fig. 60".

Fig. 62 is a schematic plan view of the upper solder mask layer with a plurality of pad windows 15.1 formed on the upper wiring layer as shown in fig. 56.

Fig. 63 is a schematic plan view of a lamp strip formed by SMT soldering LED beads or die attach chip and resistor 16.1 on the pad window shown in fig. 62.

FIG. 64 is a schematic cross-sectional view of the dual-layer flexible circuit board shown in FIG. 62.

Fig. 65 is a schematic cross-sectional view of the light strip expressed by "fig. 63".

Fig. 66 is a schematic view of a two-layer flexible wiring board in which a denotes an upper solder resist layer, b denotes an upper wiring layer, c denotes an intermediate insulating layer, d denotes a lower wiring layer, and e denotes a lower solder resist layer.

Fig. 67 is a schematic view of a lamp strip manufactured by a double-layer flexible circuit board, wherein a represents an upper solder resist layer, b represents an upper circuit layer, c represents an intermediate insulating layer, d represents a lower circuit layer, and e represents a lower solder resist layer.

Detailed Description

The present invention will be described in detail below by taking preferred embodiments as examples.

It will be appreciated by those skilled in the art that the following description is merely illustrative of and describes some preferred embodiments and that the claims do not limit the invention in any way.

Preferred embodiment one:

1. manufacture of lower circuit layer

The lower circuit layer 6 (shown in figure 6) is manufactured by adopting the traditional circuit board manufacturing process and carrying out silk-screen circuit anti-corrosion ink, baking, solidifying, etching and film stripping on the single-sided flexible copper-clad plate, and the etched circuit 6.1 is formed by adopting the film of the copper-clad plate as the lower solder mask layer 6.2.

Or a plurality of copper wires 6.1 (shown in fig. 7) and a layer of film 6.2 with glue are used, a plurality of wires are juxtaposed on a wire arranging machine to be adhered on the film with glue to form a wire arranging 6 (shown in fig. 6), and the juxtaposed wires are the lower layer wires 6.1, and the film is the lower layer solder mask layer 6.2.

2. Manufacture of upper circuit layer

2.1 manufacturing of copper-clad plate with glue

And coating flexible epoxy glue on the surface of the insulating film on a gluing production line by using a whole roll of single-layer copper flexible copper-clad plate, and drying to remove the solvent to prepare the adhesive-carrying copper-clad plate with the adhesive on the back.

2.2 punching holes

The punching die is arranged on a roll-to-roll punching machine, the die is formed by an upper die and a lower die (shown in figure 3), a plurality of punching needles are arranged in the upper die, a plurality of holes corresponding to the punching needles of the upper die are arranged in the lower die, the copper surface 9.2 of the adhesive copper-clad plate faces downwards, the film surface 9.1 of the adhesive 8.2 faces upwards, the holes 8.1 are punched on a continuous roll-to-roll automatic punching machine (shown in figure 3), the adhesive copper-clad plate 8 with the holes is manufactured (shown in figure 8), and then the copper surface burrs 4.1 (shown in figure 9 and figure 10) formed by the edges of the holes are ground by a sand wheel grinder.

2.3, assembling and pressing

The whole roll of the perforated glued copper-clad plate 8 (shown in fig. 8) and the lower layer circuit layer 6 (shown in fig. 6) are simultaneously unreeled and put into a compounding machine with a CCD correction function for lamination, the lower layer circuit 6.1 is clamped in the middle after lamination, the whole roll of the perforated glued copper-clad plate 8 (shown in fig. 8) is adhered together to form a composite board 11 (shown in fig. 11), the composite board is pressed by a quick press at 180 ℃ under 1200kg of pressure, each time is pressed for 0.5 m-0.6 m long, the composite board is placed in an oven after one section, and the composite board is baked and cured for 60 minutes at 150 ℃.

2.4 hole copper fabrication

And putting the whole roll of assembled and pressed combined board 11 into a conductive adhesive production line, processing and attaching a thin layer of conductive adhesive on the hole wall resin in the hole 8.1 to form conduction between surface layer copper and the lower layer circuit 6.1, and then plating copper on the whole roll of electroplating production line to plate a layer of copper 13.1 (shown in fig. 13) on the hole wall of the hole 8.1, wherein the thickness is in the range of 5-15 um, and the conductive capability of the hole wall is improved. At this time, electroplated copper layers of 5-15 um are added to the surface copper surface and the copper surface at the bottom of the hole, respectively.

2.5 preparation of upper Circuit layer

The upper circuit layer was produced by etching, the copper surface of the copper-plated composite board 11 (shown in fig. 13) was coated with a photosensitive etching-resistant ink, baked and cured, exposed on a roll-to-roll aerator, developed, and then the copper surface 9.2 of the copper-plated copper 13.1 with holes was etched to form a copper circuit 14.1 by an etching line, and the etching-resistant ink on the copper circuit was removed with a 5% caustic soda solution to produce an upper circuit (shown in fig. 14).

3. Manufacture of solder mask layer

The cover film 15 with the bonding pad window 15.1 is adhered to the double-layer board 11 circuit 14.1 with the manufactured upper layer circuit 14.1, the cover film and the circuit board are firmly adhered together by a whole roll press, then the double-layer board is placed in an oven, and the double-layer board is baked and cured for 60 minutes at 150 ℃ to solidify the adhesive bonding the upper layer circuit layer and the cover film, so that an upper layer solder mask with a plurality of bonding pad windows 15.1 is manufactured (shown in fig. 15).

4. Pad surface treatment

And processing the metal copper bonding pad on an OSP production line to enable an oxidation resistant layer which is helpful for the soldering function to be adsorbed on the bonding pad.

The completed double-layer flexible circuit board (shown in fig. 17) is characterized in that 15 is an upper solder mask layer, 14.1 is an upper circuit layer, 9.3 is an intermediate insulating layer, 6.1 is a lower circuit layer and 6.2 is a lower solder mask layer.

5. Lamp strip manufacturing

The SMT lamp bead and the resistor are manufactured into a lamp strip, the resistor and the lamp bead 16.1 are pasted and welded on a bonding pad of a circuit board by using an SMT technology, and the lamp strip is manufactured by reflow soldering firmly (shown in figure 16 and figure 18).

Or the LED flip chip and the resistor are manufactured by a method of sticking the chip and the resistor by a die bonder, the LED flip chip and the resistor are stuck on a bonding pad of a circuit board by using solder paste, the device is firmly welded by reflow soldering, the chip and the resistor are sealed by applying light-transmitting glue, and the glue is solidified by heating, so that the LED lamp strip is manufactured (shown in figure 16 and figure 18).

Two preferred implementations are:

1. manufacturing of copper-clad plate with glue

2. Punching hole

The punching die is arranged on a roll-to-roll punching machine, the die is formed by an upper die and a lower die (shown in figure 3), a plurality of punching needles are arranged in the upper die, a plurality of holes corresponding to the punching needles of the upper die are arranged in the lower die, the copper surface 9.2 of the adhesive copper-clad plate faces downwards, the film surface 9.1 of the adhesive 8.2 faces upwards, the holes 8.1 are punched on a continuous roll-to-roll automatic punching machine (shown in figure 3), the adhesive copper-clad plate 8 (shown in figure 19) with the holes is manufactured, and then the sand wheel plate grinding machine is used for grinding burrs 4.1 (shown in figure 20 and figure 21) of the copper surface formed by the edges of the holes.

3. Assembling press fit

The punched glued copper-clad plate 8 (shown in figure 19) and the whole roll of copper foil 22.1 are simultaneously unfolded and enter a compounding machine with a CCD correction function to be compounded and stuck together, so that a double-layer copper-clad plate 22 (shown in figure 22) is manufactured, and then is pressed by a quick press at the temperature of 180 ℃ and the pressure of 1200kg, wherein each time is 0.5 m-0.6 m long for one section, and then is pressed by one section in sequence, and then is placed in an oven, baked and cured for 60 minutes at the temperature of 150 ℃.

4. Hole copper manufacture

And (3) putting the whole roll of the assembled and pressed double-layer copper-clad plate 22 into a conductive adhesive production line, processing and attaching a thin layer of conductive adhesive on the hole wall resin of the hole 8.1 to form conduction between surface copper and lower copper foil, and then plating copper on the whole roll of electroplating production line to plate a layer of copper 13.1 (shown in fig. 24) on the hole wall, wherein the thickness is in the range of 5-15 um, and the conductive capability of the hole wall is improved. At this time, electroplated copper layers of 5-15 um are added to the surface copper surface and the copper surface at the bottom of the hole, respectively.

5. Manufacture of two circuit layers

The lower and upper circuit layers are fabricated by etching. After the copper-plated double-layer copper-clad plate 22 is coated with photosensitive etching-resistant ink in a double-layer manner, dried and cured, exposed on a full-roll exposure machine and developed, the copper-clad plate enters an etching production line to be etched to form an upper-layer copper circuit 14.1 (shown in fig. 25) and a lower-layer copper circuit 6.1 (shown in fig. 26), and the etching-resistant ink on the copper circuit is removed by using a 5% caustic soda solution, so that the production of the circuit layers on both sides is completed.

6. Manufacturing of two-layer solder mask

The cover film with the bonding pad window 15.1 shown in fig. 27 is attached to the upper circuit layer 14.1, the other cover film without the bonding pad window is attached to the lower circuit layer 6.1, the two cover films and the circuit board are firmly bonded together by a whole roll press, then the two cover films and the circuit board are placed in an oven, and the baking and curing are carried out for 60 minutes at the temperature of 150 ℃ to solidify the adhesive of the bonding circuit layer and the cover film, so that an upper solder mask with a plurality of bonding pad windows and a lower solder mask of the cover film without the bonding pad windows are manufactured.

7. Pad surface treatment

The completed double-layer flexible circuit board (shown in fig. 29) is characterized in that 15 is an upper solder mask layer, 14.1 is an upper circuit layer, 9.3 is an intermediate insulating layer, 6.1 is a lower circuit layer and 6.2 is a lower solder mask layer.

8. Lamp strip manufacturing

The SMT lamp bead and the resistor are manufactured into a lamp strip, the resistor and the lamp bead 16.1 are pasted and welded on a bonding pad of a circuit board by using an SMT technology, and the lamp strip is manufactured by reflow soldering firmly (shown in figure 28 and figure 30).

Or the LED flip chip and the resistor are manufactured by a method of sticking the chip and the resistor by a die bonder, the LED flip chip and the resistor are stuck on a bonding pad of a circuit board by using solder paste, the device is firmly welded by reflow soldering, the chip and the resistor are sealed by applying light-transmitting glue, and the glue is solidified by heating, so that the LED lamp strip is manufactured (shown in a figure 28 and a figure 30).

Three preferred implementations:

1. manufacture of lower circuit layer

The lower circuit layer 6 (shown in fig. 31) is manufactured by adopting the traditional circuit board manufacturing process and carrying out silk-screen circuit anti-corrosion ink, baking, solidifying, etching and film stripping on the single-sided flexible copper-clad plate, and the etched circuit 6.1 is formed by adopting the film of the copper-clad plate as the lower solder mask layer 6.2.

Or a plurality of copper wires 6.1 (shown in fig. 32) and a layer of film 6.2 with glue are used, a plurality of wires are juxtaposed on a wire arranging machine to be stuck on the film with glue to form a wire arranging 6 (shown in fig. 31), and the juxtaposed wires are the lower layer wires 6.1, and the film is the lower layer solder mask layer 6.2.

2. And (3) manufacturing an upper circuit layer:

2.1 manufacturing of copper-clad plate with glue

And (3) coating flexible epoxy glue on the surface of the insulating film on a gluing production line by using a whole roll of single-layer copper-clad plate, drying to remove the solvent, and shearing into a plurality of adhesive-coated copper-clad plates with the back surfaces of 0.5 meter length.

2.2 drilling holes

The 25 glued copper clad laminates are stacked into a stack, clamped by two clamping plates, drilled on a drilling machine of a large family by a drilling nozzle with the diameter of 0.5mm (shown in figure 33), and split into single sheets for later use (shown in figure 34).

2.3, assembling and pressing

Printing a plurality of insulating resin ink sticks 6.3 (shown in fig. 35) on a circuit layer 6, drying to obtain a back circuit layer (shown in fig. 35) with a plurality of insulating resin sticks 6.3, pressing the back circuit layer with the center distance between every two adjacent insulating resin sticks being 0.501 m, sequentially pressing the drilled 25 copper-clad plates with adhesive on the back (shown in fig. 34) in a head-to-tail alignment mode (shown in fig. 36) on the back circuit layer with the insulating resin sticks 6.3 to prepare a combined plate 37 (shown in fig. 37), sealing the circuit layer 6 by the insulating resin sticks 6.3 at the gap between the head and the tail, pressing the combined plate with a pressure of 180 ℃ and a pressure of 1200kg on a quick press, pressing the copper-clad plates with adhesive on the back surface for 0.5m to 0.6m each time, placing the copper-clad plates in an oven in sequence one by one, and baking and curing the copper-clad plates with adhesive for 60 minutes with a temperature of 150 ℃.

2.4 hole copper fabrication

And putting the whole roll of assembled and pressed combined board 37 into a conductive adhesive production line, processing and attaching a thin layer of conductive adhesive on the hole wall resin in the hole 8.1 to form conduction between surface layer copper and lower layer copper foil, and then plating copper on the whole roll of electroplating production line to plate a layer of copper 13.1 (shown in fig. 38 and 39) on the hole wall, wherein the thickness is in the range of 5-15 um, and the conductive capability of the hole wall is improved. At this time, electroplated copper layers of 5-15 um are added to the surface copper surface and the copper surface at the bottom of the hole, respectively.

2.5 preparation of upper Circuit layer

The upper circuit layer is manufactured by an etching method, photosensitive etching-resistant ink is coated on the copper-plated combined board, baking and curing are carried out, the copper-plated combined board is exposed on a whole roll of exposure machine and developed, then the copper-plated combined board is etched to form a copper circuit 40.1 (shown in figure 40) by entering an etching production line, and the etching-resistant ink on the copper circuit is removed by using 5% caustic soda solution to manufacture the upper circuit. The upper circuit is made by connecting and conducting metal copper of two adjacent upper circuit layers in the gap between the two adjacent upper circuit layers (shown in fig. 41 and 42); or in the gap between two adjacent upper circuit layers, the metal-free copper connection conduction is etched, and the circuit between the two adjacent upper circuit layers is completely disconnected (shown in fig. 43 and 44).

3. Manufacture of solder mask layer

The cover film with the bonding pad windows 15.1 is adhered to the upper layer circuit 40.1 of the double-sided board, the cover film and the circuit board are firmly adhered together by a whole roll press, and then the double-sided board is placed in an oven, baked and cured for 60 minutes at 150 ℃ to cure the adhesive bonding the upper layer circuit layer and the cover film, and an upper layer solder mask with a plurality of bonding pad windows 15.1 is manufactured (shown in fig. 45).

4. Pad surface treatment

The completed double-layer flexible circuit board (shown in fig. 47) is 15 of an upper solder mask layer, 14.1 of an upper circuit layer, 9.3 of an intermediate insulating layer, 6.1 of a lower circuit layer and 6.2 of a lower solder mask layer.

5. Lamp strip manufacturing

The SMT lamp bead and the resistor are manufactured into a lamp strip, the resistor and the lamp bead 16.1 are pasted and welded on a bonding pad of a circuit board by using an SMT technology, and the lamp strip is manufactured by reflow soldering firmly (shown in fig. 46 and 48).

Or the LED flip chip and the resistor are manufactured by a method of sticking the chip and the resistor by a die bonder, the LED flip chip and the resistor are stuck on a bonding pad of a circuit board by using solder paste, the device is firmly welded by reflow soldering, the chip and the resistor are sealed by applying light-transmitting glue, and the glue is solidified by heating, so that the LED lamp strip (shown in a graph 48 of fig. 46) is manufactured.

Four preferred implementations are:

1. a plurality of p i cover films 49.1 (shown in fig. 49) each 10mm wide were attached to a long copper foil roll 49, and pi cover film strips were insulating resin strips, and the center-to-center distance between two adjacent insulating resin strips was 0.501 m, to prepare a copper foil with a plurality of pi films 49.1 (shown in fig. 49).

2. Manufacturing of copper-clad plate with glue

3. Drilling holes

The 25 glued copper clad laminates are stacked into a stack, clamped by two clamping plates, drilled on a drilling machine of a large family by a drilling nozzle with the diameter of 0.5mm, and split into single sheets for later use (shown in a graph 51 of fig. 50).

4. Assembling press fit

The drilled 25 copper-clad plates with adhesive on the back (shown in fig. 51) are aligned and attached to the copper foil with the insulating resin adhesive tape 49.1 in a head-to-tail arrangement (shown in fig. 52), the copper foil is sealed by the insulating resin tape 49.1 at the gap between the head and the tail to prepare the double-layer copper-clad plate shown in fig. 53, the double-layer copper-clad plate is pressed by a quick press at 180 ℃ and 1200kg, each time is pressed for 0.5 m-0.6 m long, the double-layer copper-clad plate is pressed one by one in sequence, and then the double-layer copper-clad plate is placed in an oven, baked and cured for 60 minutes at 150 ℃.

5. Hole copper manufacture

And (3) putting the whole roll of the assembled and pressed double-layer copper-clad plate into a conductive adhesive production line, processing and attaching a thin layer of conductive adhesive on the resin of the hole wall of 8.1 to form conduction between surface copper and lower copper foil, and then plating copper on the whole roll of electroplating production line to plate the hole wall with a layer of copper 13.1 (shown in fig. 54 and 55), wherein the thickness is in the range of 5-15 um, and the conductive capability of the hole wall is improved. At this time, electroplated copper layers of 5-15 um are added to the surface copper surface and the copper surface at the bottom of the hole, respectively.

6. The manufacture of two circuit layers,

the lower and upper circuit layers are fabricated by etching. After the copper-plated double-layer copper-clad plate is coated with photosensitive etching-resistant ink in a double-layer manner, dried and cured, exposed on a whole roll exposure machine and developed, the copper-clad plate enters an etching production line to be etched to form an upper-layer copper circuit 40.1 (shown in fig. 56) and a lower-layer copper circuit 6.1 (shown in fig. 57), and the etching-resistant ink on the copper circuit is removed by using a 5% caustic soda solution to finish the manufacture of two-side circuit layers; in the gap between two adjacent upper circuit layers, the metal copper connecting and conducting layers (shown in fig. 58 and 59) for connecting the two adjacent upper circuit layers are arranged in the manufactured upper circuit; or in the gap between two adjacent upper circuit layers, the metal-free copper connection conduction is etched, and the circuit between the two adjacent upper circuit layers is completely disconnected (shown in fig. 60 and 61).

7. Manufacture of solder mask layer

The cover film with the bonding pad window 15.1 is adhered to the upper circuit layer 40.1, the other cover film without the bonding pad window is adhered to the lower circuit layer 6.1, the two cover films and the circuit board are firmly adhered together by a whole roll press, and then the cover film and the circuit board are placed in an oven, baked and cured for 60 minutes at the temperature of 150 ℃ to solidify the adhesive of the bonding circuit layer and the cover film, so that an upper solder mask layer (shown in fig. 62) with a plurality of bonding pad windows and a lower solder mask layer of the cover film without the bonding pad windows are manufactured.

8. Pad surface treatment

The completed double-layer flexible circuit board (shown in fig. 64) is characterized in that 15 is an upper solder mask layer, 14.1 is an upper circuit layer, 9.3 is an intermediate insulating layer, 6.1 is a lower circuit layer and 6.2 is a lower solder mask layer.

9. Lamp strip manufacturing

The SMT lamp bead and the resistor are manufactured into a lamp strip, the SMT technology is used for bonding the resistor and the lamp bead 16.1 to a bonding pad of a circuit board, reflow soldering is carried out firmly, and a strip splitting machine is used for splitting to manufacture the LED lamp strip (shown in a graph 65 of FIG. 63).

Or the LED flip chip and the resistor are manufactured by a method of sticking the chip and the resistor by a die bonder, the LED flip chip and the resistor are stuck on a bonding pad of a circuit board by using solder paste, the device is firmly welded by reflow soldering, the chip and the resistor are sealed by applying light-transmitting glue, the glue is solidified by heating, and the LED lamp strip is manufactured by splitting (shown in a graph 65 of FIG. 63).

The invention solves the technical problems of drilling limitation and the industry of forming floating copper on the hole wall when punching and manufacturing hole wall copper, not only realizes the full-automatic full-flow high-efficiency roll-to-roll production of the double-layer flexible circuit board, but also realizes the low-cost manufacturing of the circuit board of the overlength double-layer circuit with the length of more than 1 meter.

The present invention is described in detail with reference to the drawings, in which a double-layer flexible circuit board and a method of manufacturing the same are described. However, it will be appreciated by persons skilled in the art that the foregoing description is merely illustrative of and describes some embodiments and that the scope of the invention, particularly the scope of the claims, is not to be in any way limited.

Claims

1. A method for manufacturing a double-layer flexible circuit board includes such steps as preparing a single-layer flexible circuit board with length greater than 1 m, winding, coating adhesive layer on the back of copper-clad plate, winding, laminating, pressing, sticking, holding copper layer, and etching copper layer to form a copper pad.

2. A method for manufacturing a double-layer flexible circuit board includes such steps as coating adhesive on back of a single-layer copper-clad plate with length greater than 1 m to form an adhesive layer, loading a die on a continuous punch press, loading the die on the die consisting of upper and lower dies, multiple punching pins in upper die, multiple holes in lower die, punching copper surface by die, generating copper burrs on hole edges, grinding copper burrs by sand wheel grinder, stacking copper-clad plates with adhesive layer on back of copper burrs, and copper foil with length greater than 1 m, pressing to adhere, exposing the metal on copper foil, making a layer of electric conductor, plating copper, connecting two layers by hole wall copper, etching to form two layers of circuit layers, making two layers of solder masks, and making a double-layer flexible circuit board with at least one solder mask layer with solder pad.

3. A dual-layer flexible circuit board, comprising:

a lower solder mask layer;

a lower wiring layer;

An intermediate insulating layer;

an upper wiring layer;

an upper solder mask layer;

the double-layer flexible circuit board is characterized in that all layers of the double-layer flexible circuit board are arranged and combined together according to the following sequence, namely, a lower circuit layer is combined on a lower circuit layer solder mask layer, an intermediate insulating layer is combined on the lower circuit layer, an upper circuit layer is combined on the intermediate insulating layer, the upper circuit layer solder mask layer is combined on an upper circuit layer, the double-layer flexible circuit board is a flexible circuit board with the length of more than 1 meter, a plurality of holes are formed in the double-layer flexible circuit board, conduction between the upper circuit layer and the lower circuit layer is formed by metal copper combined on a hole wall, and the holes are characterized in that at least one solder mask layer passes through the upper circuit layer and the intermediate insulating layer and does not pass through the lower circuit layer, a bonding pad window is formed in at least one solder mask layer, and all or part of the holes are covered by the upper circuit layer solder mask layer.

4. A manufacturing method of a double-layer flexible circuit board comprises the steps of firstly manufacturing a single-layer flexible circuit board, wherein the length of the single-layer flexible circuit board is larger than 2 meters, the circuit layer of the single-layer flexible circuit board is a lower circuit layer of the double-layer circuit board, a plurality of insulating resin printing inks are printed on the lower circuit layer, the inks are cured through baking to form insulating resin strips, the center distance between every two adjacent insulating resin strips is a, a is smaller than or equal to 2 meters, then coating adhesive on the back of a single-layer copper flexible copper-clad plate, cutting into a plurality of short copper-clad plates, the length of each short copper-clad plate is b, b is smaller than or equal to a, the short copper-clad plates are stacked together, the short copper-clad plates are used after being drilled by a drilling machine, the short copper-clad plates with the holes are arranged at the head and tail parts of the single-layer flexible circuit board, the insulating resin strips are arranged at gaps between the two adjacent short copper-clad plates, a lower metal circuit is upwards exposed from holes, the single-layer flexible circuit board and the single-layer copper-clad plate are firmly combined by a press, a layer conductive object is manufactured on the hole wall, then copper is plated with a copper layer, the copper-clad plate is manufactured on the hole wall, the copper-clad plate is connected with the copper-clad plate through the upper circuit layer by etching, and the copper-clad plate is manufactured, and the copper-clad layer is manufactured by etching a large-layer, and the copper-clad layer.

5. A method for manufacturing a double-layer flexible circuit board includes such steps as coating adhesive on back of a single-layer copper-clad plate, cutting to obtain multiple short copper-clad plates with length less than b meters, drilling holes on a drilling machine, sticking multiple insulating resin strips on the surface of copper foil with length greater than 2 meters, arranging the multiple short copper-clad plates with adhesive on the copper foil with length greater than 2 meters, covering the copper foil with gap between two adjacent short copper-clad plates, exposing copper to front, pressing to bond the copper foil with adhesive, making a layer of electric conductor on the hole wall, plating copper on the hole wall, making a layer of copper on the hole wall, making copper on the copper foil with copper layer, making a layer of electric conductor on the copper layer, making a layer of electric conductor, and a layer of copper layer on the copper layer.

6. A dual-layer flexible circuit board, comprising:

a lower solder mask layer;

a lower wiring layer;

an intermediate insulating layer;

an upper wiring layer;

an upper solder mask layer;

the double-layer flexible circuit board is characterized in that layers of the double-layer flexible circuit board are arranged and combined together according to the following sequence, a lower layer circuit layer is combined on a lower layer solder mask layer, an intermediate insulating layer is combined on the lower layer circuit layer, an upper layer circuit layer is combined on the intermediate insulating layer, the upper layer solder mask layer is combined on an upper layer circuit layer, the lower layer circuit layer is a continuous long circuit layer, the length of the lower layer circuit layer is greater than 2 meters, the upper layer circuit layer is a plurality of sections of short circuit layers, the length of each section of upper layer circuit layer is less than or equal to 2 meters, a gap is formed between every two adjacent sections of upper layer short circuit layers, and insulating resin strips cover the lower layer circuit layer at the gap. The double-layer circuit board is provided with a plurality of holes, the holes pass through the upper circuit layer and the middle insulating layer, but do not pass through the lower circuit layer, all or part of the holes are covered by a solder mask, the conduction between the upper circuit layer and the lower circuit layer is formed by connecting copper on the upper circuit and the lower circuit through metal copper combined on the hole wall, and the upper solder mask is provided with a plurality of windows, so that the upper circuit layer is formed with a plurality of metal bonding pads.

7. A double-layer flexible circuit board according to claim 1 or 2 or 3 or 4 or 5 or 6, wherein LEDs or LEDs and control elements can be soldered on the double-layer flexible circuit board to form a double-layer circuit board LED strip.

8. A double-layer flexible circuit board according to claim 1, 2, 3, 4, 5 or 6, wherein the lower circuit layer is a copper circuit layer, or a copper-clad aluminum circuit layer, or a copper-aluminum composite circuit layer.

9. A double-layer flexible circuit board according to claim 2, 3, 5 or 6, wherein the lower solder resist layer or the upper solder resist layer is a coverlay film solder resist layer or an ink solder resist layer.

10. The dual-layer flexible circuit board as claimed in claim 1, 3, 4 or 6, wherein the lower solder mask layer is a coverlay solder mask layer, and the upper solder mask layer is a coverlay solder mask layer or an ink solder mask layer.

11. A double-layer flexible circuit board according to claim 1, 2 or 3, which can be used by cutting the long flexible circuit board into short circuit boards of 1 meter or less.

12. The double-layer circuit board LED strip of claim 7, wherein said LEDs are LED flip chips, or LED CSP devices, or LED beads with LED chips encapsulated on a carrier.

13. The double-layer flexible circuit board according to claim 4, 5 or 6, wherein the gap between the two adjacent upper circuit layers is filled with metal copper for connecting the two adjacent upper circuit layers, and the two adjacent upper circuit layers are connected and conducted; or no metal copper exists in the gap between the two adjacent upper circuit layers, and the two adjacent upper circuit layers are completely disconnected.