CN114900998A - Multilayer circuit board and processing method thereof - Google Patents

Abstract

The invention discloses a multi-layer circuit board and a processing method thereof. The processing method of the multi-layer circuit board comprises the following steps: aligning and pasting an inner layer protective film on a double-sided board formed with an inner layer circuit to form an inner layer The double-sided board of the protective film, the copper glue board and the double-sided board with the inner layer protective film are laminated and baked, and the outer layer circuit is formed on the single board of the multi-layer board, and the processed The multi-layer board and the outer layer protective film are aligned, laminated, and baked until the outer layer protective film is completely cured, wherein the outer layer protective film is provided with a second opening in the opening area, and the second The shape of the opening is the same as that of the opening area, and the width of one side of the opening is smaller than the second preset length, and the difference between the second preset length and the preset distance is greater than 0.

Description

A kind of multilayer circuit board and its processing method

technical field

The invention belongs to the technical field of flexible circuit boards, and in particular relates to a multi-layer circuit board and a processing method thereof.

Background technique

Flexible Printed Circuit (FPC for short) is a highly reliable and excellent flexible printed circuit board made of polyimide or polyester film as the base material. It has the characteristics of high wiring density, light weight, thin thickness and good bendability. The flexible circuit board can move and expand in three-dimensional space, realize the three-dimensional wiring of the circuit, improve the integration degree of component assembly and connection, reduce the product volume and maintain high stability, so FPC can be widely used in Mobile phones, computers, mobile peripherals, automotive electronics and other industries.

With the upgrading of electronic products, multilayer FPCs with three or more layers are gradually increasing to meet the functional requirements of high density. Because the higher the number of layers and the thicker the thickness of the flexible circuit board, the worse its bending performance and reliability cannot meet the requirements. In order to maintain the balance between versatility and bendability, a local delamination design is usually developed at the position where the multi-layer FPC needs to be bent, and the outer layer circuit board in a specific area is cut and peeled off by processes such as laser or punching, so as to achieve local The single-layer or double-layer structure of the circuit board improves the bending performance of the circuit board, and the layer-reduced area is also called the de-cap area.

At present, the existing technology mainly adopts the back-opening process, that is, the outer layer copper foil is cut by picosecond laser. In order to prevent the inner layer glue (bonding glue) from being heated and melted during the laser process, the glue flow phenomenon is usually applied on the outer layer. Before closing, shrink the opening of the glue by 0.1mm; after the process of hot rolling glue, laminating machine and laser opening the cover, the edge of the inner layer glue is 60-140um from the edge of the opening area; The filling of the inner layer circuit is better, and the risk of the inner layer gap is small; however, if the lamination parameters of higher pressure are used, the protective film glue is usually backfilled with 80-110um, and there is still a possibility that the two types of glue are not in contact, resulting in the gap, thus It affects the insulation performance of the inner and outer layers of the FPC, and there is a risk of copper ions migrating and growing in the gap under a long-term voltage load, resulting in poor functions such as spark test (spark) and short circuit of the FPC.

SUMMARY OF THE INVENTION

Therefore, the present invention aims to solve the technical problems of the prior art that a gap occurs in the open area of the inner layer circuit of the flexible circuit board, which leads to a failure of the spark test or a short circuit and other poor functions.

In order to solve the above-mentioned technical problems, the present invention provides a processing method of a multilayer circuit board, and the processing method of the multilayer circuit board comprises the following steps:

Step S100, aligning and pasting the inner layer protective film on the double-sided board formed with the inner layer circuit to form a double-sided board with an inner layer protective film, wherein the shape of the inner layer protective film is the same as the shape of the opening area And the width of the unilateral relative opening area is greater than the first preset length;

Step S200, bonding the copper rubber sheet and the double-sided board with the inner layer protective film and laminating and baking, so that the inner layer glue in the copper rubber sheet melts and overflows and is protected with the inner layer in the molten state. The inner layer circuit is jointly filled with the film to obtain a multi-layer board, wherein the copper glue plate includes the inner layer glue and a single panel that are pressed together, the copper glue plate is provided with a first opening, and the first The size and shape of the opening are the same as the opening area;

Step S300, setting and forming an outer layer circuit on the single panel of the multi-layer board, wherein the outer layer circuit and the edge of the cover opening area are separated by a preset distance;

Step S400, the multi-layer board and the outer layer protective film processed in step S300 are aligned and laminated, and baked until the outer layer protective film is completely cured, wherein the outer layer protective film is opened when the cover is opened. The area is provided with a second opening, the shape of the second opening is the same as that of the opening area, and the width of one side of the opening area is smaller than a second preset length, and the second preset length is equal to the preset distance. The difference is greater than 0.

Preferably, in the processing method of the multilayer circuit board, the difference between the second preset length and the preset distance is ΔL, and ΔL is 0.2±0.1 mm.

Preferably, in the processing method of the multilayer circuit board, the preset distance is D, and D is 0.45±0.1 mm.

Preferably, in the processing method of the multilayer circuit board, before the step S100, the following steps are further included:

The protective film is attached to the carrier film and punched to obtain an inner layer protective film with the same shape as that of the opening area and a first preset length of one side opposite to the width of the opening area.

Preferably, in the processing method of the multilayer circuit board, the first preset length is L1, and L1 is 0.70±0.1 mm.

Preferably, in the processing method of the multilayer circuit board, before the step S200, the following steps are further included:

The inner layer glue and the single panel are sequentially attached and pressed together to form the copper glue plate, and a first opening is formed by cutting in the open area of the copper glue plate, and the size and shape of the first opening are the same as the open area.

Preferably, in the processing method of the multilayer circuit board, before the step S400, the following steps are further included:

A second opening is formed by cutting the outer layer protective film in the cover opening area, the shape of the second opening is the same as that of the cover opening area, and the width of one side of the opening area is smaller than the second preset length.

Preferably, in the processing method of the multilayer circuit board, the second preset length is L2, and L2 is 0.25±0.1 mm.

The present invention also provides a multi-layer circuit board, which comprises:

The double-sided panel layer includes an inner layer protective film that is sequentially attached and laminated from the first direction and a double-sided panel formed with an inner layer circuit. The shape of the inner layer protective film is the same as the shape of the opening area, and the cover is opened on one side opposite to each other. The width of the area is greater than the first preset length;

The copper glue board is pasted and laminated on the double-sided layer along the first direction, and the copper glue plate includes an inner layer glue and a single panel that are successively pasted and laminated along the first direction, and the single plate is provided with For the external circuit, the copper glue plate is provided with a first opening, the size and shape of the first opening are the same as that of the opening area, and the inner layer glue and the inner layer protective film together fill the inner circuit, wherein a preset distance between the outer layer circuit and the edge of the opening area;

The outer layer protective film is attached and laminated on the copper glue board along the first direction, the outer layer protective film is provided with a second opening in the opening area, and the shape of the second opening is the same as that in the opening area, And the width of the single side is smaller than the second preset length, and the second preset length is smaller than the preset distance.

Preferably, in the multilayer circuit board, the difference between the second preset length and the preset distance is ΔL, and ΔL is 0.2±0.1 mm; wherein,

The preset distance is D, and D is 0.45±0.1 mm; and/or,

The second preset length is L2, and L2 is 0.25±0.1 mm; and/or,

The first preset length is L1, and L1 is 0.70±0.1 mm.

The technical scheme provided by the present invention has the following advantages:

In the invention, the inner layer protective film is added in the opening area, meanwhile, the inner layer adhesive shrinking design is canceled, and it is processed after lamination with the outer layer single panel, so as to ensure the fusion of the inner layer adhesive and the inner layer protective film adhesive, and avoid the inner layer wiring. There is a gap in the opening area, resulting in a failure of the spark test or a short circuit and other malfunctions;

Further, the present invention forms a double-sided board with an inner-layer protective film by aligning and pasting the inner-layer protective film on the double-sided board formed with the inner-layer circuit, wherein the shape of the inner-layer protective film and the opening area are have the same shape and the width of one side relative to the open area is greater than the first preset length, the copper rubber sheet and the double-sided board with the inner layer protective film are laminated and baked, so that the inner layer of the copper rubber sheet is laminated and baked. The glue melts and overflows and fills the inner layer circuit together with the inner layer protective film in the molten state, so as to obtain a multi-layer board, wherein the copper glue plate includes the inner layer glue and the single panel that are pressed together, so The copper glue board is provided with a first opening, the size and shape of the first opening are the same as the opening area, and an outer layer circuit is formed on the single panel of the multi-layer board, wherein the outer layer circuit is formed. There is a preset distance from the edge of the opening area, and the processed multi-layer board and the outer layer protective film are aligned, laminated, and baked until the outer layer protective film is completely cured, wherein the The outer protective film is provided with a second opening in the cover opening area, the shape of the second opening is the same as that of the cover opening area, and the width of one side is smaller than the second preset length compared with the cover opening area, and the second preset length The difference from the preset distance is greater than 0, so that the inner layer glue in the copper glue board melts and overflows and fills the inner layer circuit together with the inner layer protective film in the molten state, and the outer layer protective film is more than the outer layer. The unilateral large △L of the line ensures that the line is completely covered in the protective film;

Further, by splitting the protective film into an inner layer and an outer layer design, and processing it on the surface of the circuit board before and after laminating the inner layer glue, the filling stability of the glue in the open area of the multi-layer flexible circuit board is improved, avoiding the The incomplete filling of the glue results in undesirable phenomena such as copper ion migration, which improves the yield and stability of the product;

Further, the present invention increases the cover opening design of the outer layer protective film, and reduces the overall thickness of the cover opening area of the multilayer board.

Description of drawings

In order to illustrate the specific embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings required in the description of the specific embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

1 is a cross-sectional view of a multi-layer circuit board in the prior art;

2 is a cross-sectional view of an embodiment of a double-sided panel provided by the present invention;

3 is a cross-sectional view of an embodiment of a double-sided panel with inner layer lines provided by the present invention;

4 is a cross-sectional view of the double-sided panel with inner layer circuit in FIG. 3 after laminating the inner layer protective film;

5 is a cross-sectional view of the copper rubber sheet after the first opening provided by the present invention;

6 is a cross-sectional view of an embodiment of a multilayer board provided by the present invention;

7 is a cross-sectional view of an embodiment in which the multilayer board in FIG. 6 is provided with an outer layer circuit;

FIG. 8 is a cross-sectional view of the multi-layer board and the outer protective film in FIG. 7 after bonding;

FIG. 9 is a schematic flowchart of an embodiment of a method for processing a multilayer circuit board provided by the present invention.

Description of the prior art reference numerals:

label name label name 100’ Multilayer circuit board 3’ Copper plywood 1' protective film 31’ inner layer glue 2' Double panel 32’ single panel twenty one' first copper layer 321’ third copper layer twenty two' first substrate 322’ second substrate twenty three' second copper layer 4’ gap

Description of the reference numerals of the present invention:

label name label name 100 Multilayer circuit board 32 single panel 1 inner protective film 321 third copper layer 2 Double panel 322 second substrate twenty one first copper layer 33 first opening twenty two first substrate 4 Outer protective film twenty three second copper layer 5 inner line 3 Copper plywood 6 Outer line 31 inner layer glue

The realization, functional characteristics and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and in conjunction with embodiments. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

It should be noted that the terms "first", "second" and the like in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence.

In the present invention, unless otherwise stated, the directional words used such as "upper, lower, top, bottom" are usually for the directions shown in the drawings, or for the components themselves in vertical, In terms of vertical or gravitational direction; similarly, for the convenience of understanding and description, "inner and outer" refers to the inner and outer relative to the contour of each component itself, but the above-mentioned orientation words are not used to limit the present invention.

FIG. 1 shows a cross-sectional view of a multi-layer circuit board in the prior art. Please refer to FIG. 1. The processing method of the multi-layer circuit board in the prior art includes:

Step S100': align and fit the inner layer adhesive 31' and the double-sided panel 2' according to the alignment holes;

Wherein, the double-sided panel 2' of the step S100' includes a first copper layer 21', a first base material 22', and a second copper layer 23' that are stacked together in sequence.

Step S200'; the inner layer glue 31' and the double-sided plate 2' after the single-sided board 32' is bonded in step S100', and the position is bonded, and the inner layer glue is cured by the high temperature and high pressure treatment of the laminator to form a multi-layer board;

Wherein, the single panel 32' includes a third copper layer 321' and a second substrate 322' that are sequentially stacked together.

Step S300 ′: laser processing through blind holes, plasma etching to remove glue residue, carbon film, and copper plating to form through holes on the multilayer board with a single-sheet process, and then dry film, exposure, development, etching, and film removal to form L3 layer circuit graphics;

Step S400 ′: Uncovering process: locate the area to be opened according to the optical mark (Fiducial mark) etched in the L3 layer, and use picosecond laser to cut the pattern, and then use the machine to tear off the L3 layer substrate and copper above the glue opening, Expose the L2 layer lines. Then manually inspect the open area for defects such as substrate residue, delamination or damage, and finally use plasma etching to remove the glue residue.

After step S400 ′, the multi-layer board after the opening of the cover is also included in order to pass the optical detection of the glue flow and the electrical detection of the open circuit short circuit and other malfunctions, the conventional lamination of the protective film 1 ′, the lamination of the protective film 1 ′, the solder mask treatment and the surface treatment. Wait.

The processing method of the multi-layer circuit board is the above-mentioned back-opening process, and a gap 4' appears in the open-cover area of the inner layer circuit of the flexible circuit board, resulting in a failure of the spark test or a short circuit and other malfunctions.

Example 1

2 to 9 are schematic diagrams showing the steps of the method for manufacturing a multilayer wiring board of the present invention. The present invention provides a method for processing a multi-layer circuit board, wherein the multi-layer circuit board 100 may be three-layer, four-layer, . The present invention is described below by taking a three-layer circuit board as an example. The three-layer circuit board includes a double-sided board 2, an inner layer of glue 31, a single-sided board 32, and the like.

Please refer to FIG. 9, the processing method of the multilayer circuit board includes the following steps:

In step S100, the inner layer protective film 1 is aligned and pasted on the double-sided board 2 formed with the inner layer circuit 5 to form a double-sided board 2 with the inner layer protective film 1, wherein the shape of the inner layer protective film 1 is the same as that of the double-sided board 2. The shape of the opening area is the same, and the width of one side relative to the opening area is greater than the first preset length;

Specifically, in the step S100, the inner layer protective film 1 is aligned and pasted on the double-sided board 2 formed with the inner layer circuit 5, which may be using a clamp, then cured by a fast press, and baked at a high temperature to remove moisture. Lamination can also be used for curing. These are all in the prior art and will not be described in detail. The first preset length is L1, and L1 is 0.70±0.1 mm, that is, L1 is 0.6 mm˜0.80 mm, for example, L1 may be 0.65 mm, 0.66 mm, 0.68 mm, 0.70 mm, 0.72 mm, 0.74 mm, or 0.76 mm mm.

In this embodiment, please refer to FIG. 2 , the double-sided panel 2 includes a first copper layer 21 , a first substrate 22 (eg, polyimide), and a second copper layer 23 that are formed by stacking along the first direction.

Wherein, before step S100 in the manufacturing process step S110 of the inner layer protective film 1, the protective film may be attached to the carrier film, and punched to obtain a shape that is the same as the shape of the opening area, and one side is opposite to the opening area. The inner layer protective film 1 with a width of the first preset length specifically includes:

Step S111, attaching the unprocessed protective film to the carrier film;

Wherein, the laminating process may be, but not limited to, laminating the unprocessed protective film on the carrier film in a roll process, and the carrier film may be, but not limited to, a transparent polyethylene terephthalate PET material.

In step S112, the protective film in step S111 is punched out in shape, the shape of which is the same as the shape of the opening area, but the first preset length is increased on one side to obtain the inner layer protective film 1 arranged on the surface of the carrier film;

Among them, please refer to FIG. 4, the punching process can be but not limited to punching the shape in a half-cut way, the shape of which is the same as the shape of the opening area, but the first preset length L1 is increased on one side (it needs to be understood that the single side Compared with the opening area, the first preset length is increased, that is, the distance between each side and the opening area is increased by the same first preset length), and the cutting depth is consistent with that of the protective film. In other embodiments, it can also be cutting The depth is greater than that of the protective film, so that the shape of the protective film is cut completely.

Step S112 also includes steps such as tearing off waste materials after punching, which will not be described in detail here.

3, the process of the double-sided panel 2 with the inner layer circuit 5 can be a conventional method, for example, a roll-to-roll process laser processing through blind holes, dry film pressing, exposure, development, etching, film removal, etc. process to form L2 layer lines.

Step S200, the copper glue plate 3 is attached to the double-sided board 2 with the inner layer protective film 1 and laminated and fixed, so that the inner layer glue 31 in the copper glue plate 3 is melted and overflowed and is in the molten state. The inner layer protective film 1 of the inner layer is filled with the inner layer circuit 5 to obtain a multi-layer board, wherein the copper glue plate 3 includes the inner layer glue 31 and the single panel 32 that are pressed together. The copper glue plate 3 A first opening 33 is opened, and the size and shape of the first opening 33 are the same as the opening area;

Specifically, referring to FIG. 6 , after aligning and laminating the copper rubber sheet 3 with the double-sided board 2 with the inner layer protective film 1 , lamination, baking, etc. to form a multi-layer board, wherein the inner layer of the copper rubber sheet 3 is The layer glue 31 melts and overflows under high temperature and high pressure, fuses with the inner layer protective film 1 in the molten state and fills the inner layer circuit 5 together, and finally solidifies together. The width of the inner layer glue 31 under high temperature and high pressure is usually 0-0.125mm. Referring to FIG. 5 , the single panel 32 includes a third copper layer 321 stacked along the first direction, and a second substrate 322 (polyimide).

Wherein, before the step S200, please refer to FIG. 5, which further includes the following steps:

In step S210, the inner layer glue 31 and the single panel 32 are sequentially attached and pressed together to form the copper glue plate 3, and a first opening 33 is formed in the open area of the copper glue plate 3. The size of the first opening 33 The shape is the same as the opening area.

Specifically, the unprocessed inner layer glue 31 and the single panel 32 are laminated and pressed to form the copper glue plate 3 in a roll process. Cut the copper rubber sheet 3 into a single sheet, and use the single sheet process to laser or die punching to process the partial alignment holes and exhaust holes of the layer, and the aperture is generally 2mm. At the same time, the shape is laser cut in the opening area, and the size and shape are the same as the opening area. Unlike the rear decapping process, the front decapping process does not require strict control of the cutting depth. After laser cutting to get the opening, clean to remove toner and glue residue.

Step S300, setting and forming an outer layer circuit 6 on the single panel 32 of the multi-layer board, wherein the outer layer circuit 6 is spaced a preset distance from the edge of the opening area;

Specifically, the process of disposing and forming the outer layer circuit 6 on the single panel 32 of the multi-layer board is similar to the conventional process, and will not be described in detail here. Please refer to FIG. 7 , the difference is the preset distance between the outer layer circuit 6 and the edge of the opening area. In this embodiment, the preset distance is D, and D is 0.45±0.1mm, that is, D is 0.35mm～ 0.55mm, in this way, it can effectively ensure that after the protective film is attached, the protective film and the protective film flow glue away from the cover area. The open cover area is generally used for bending functions. cover area, which can have an impact on the reliability of the bend. In other embodiments, D may be 0.37mm, 0.39mm, 0.41mm, 0.43mm, 0.45mm, 0.47mm, or 0.5mm.

Step S400, the multi-layer board and the outer layer protective film 4 processed in step S300 are aligned and laminated until the outer layer protective film 4 is completely cured, wherein the outer layer protective film 4 is opened. The lid area is provided with a second opening, the shape of the second opening is the same as that of the lid opening area, and the width of one side of the lid opening area is smaller than the second preset length, and the second preset length is smaller than the preset distance , so that it can be ensured that the outer protective film 4 is larger than the circuit, and the outer protective film 4 is used to protect the circuit layer. Specifically, referring to FIG. 8 , the multi-layer board processed in step S300 and the outer layer protective film 4 are aligned and laminated, which may be, but not limited to, alignment and lamination according to alignment holes, and then through the layer Press the glue to fully cure the outer layer protective film 4, because the unilateral distance between the outer layer protective film 4 and the outer layer circuit 6 is greater than the preset value (that is, the difference ΔL between the second preset length and the preset distance), so , it can be ensured that the outer layer circuit 6 is completely covered in the outer layer protective film 4 .

In this embodiment, ΔL is 0.2±0.1mm, that is, ΔL is 0.1mm～0.3mm, since the tolerance of the outer layer protective film 4 is 0.2mm, if ΔL is too small, consider the outer layer protective film 4 Lamination deviation will cause the outer protective film 4 to fail to cover the circuit layer. If it is too large, the outer protective film 4 will be too close to the open area, and the lamination deviation will cause the outer protective film 4 to shift to the open area. , causing defects; in addition, for multi-layer boards, it is also necessary to consider the influence of factors such as the expansion and contraction factors of flex boards, environmental factors in the production process, equipment stability and other factors on the lamination accuracy. Therefore, in this embodiment, △L is 0.1mm ~0.3mm, the effect is better. In other embodiments, ΔL may be 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.20mm, 0.21mm, or 0.22mm.

In this embodiment, the second preset length is L2, and L2 is 0.25±0.1 mm.

Preferably, in the method for processing the multilayer circuit board 100, preferably, in the method for processing the multilayer circuit board 100, the first preset length is L1, and L1 is 0.70±0.10mm, that is, L1 is 0.60mm～0.80mm, in this way, the copper rubber plate and the opening area can be overlapped by at least 0.2mm to make the effect better. For example, L1 can be 0.65mm, 0.72mm, 0.74mm, 0.76mm , or 0.78mm.

Preferably, in the processing method of the multilayer circuit board 100, before the step S400, the following steps are further included:

In step S410 , a second opening is formed in the cover opening area of the outer layer protective film 4 . The shape of the second opening is the same as that of the cover opening area, and the width of one side of the opening area is smaller than the second preset length.

Specifically, after cutting the outer layer protective film 4 into a single sheet, the alignment holes are processed by a laser or punching process, and at the same time, a second opening is cut in the opening area. The shape of the opening of the second opening is the same as the opening area, but the single opening is While reducing the second preset length, the laser process needs to use alcohol to clean the toner or glue residue.

In addition, after the step S400, solder mask treatment and surface treatment are also included. Since the subsequent process may be a conventional process in the prior art, it will not be described in detail here.

In the present invention, the inner layer protective film 1 is added in the opening area, while the inner layer adhesive 31 is cancelled inwardly, and the inner layer adhesive 31 is laminated with the outer layer single panel 32 after processing, so as to ensure the fusion of the inner layer adhesive 31 and the inner layer protective film 1 adhesive. It avoids the failure of the spark test or the occurrence of short circuit due to the gap in the open area of the inner layer circuit 5;

Further, the present invention forms the double-sided board 2 with the inner-layer protective film 1 by aligning the inner-layer protective film 1 on the double-sided board 2 formed with the inner-layer circuit 5, wherein the inner-layer protective film 1 The shape is the same as the shape of the opening area and the width of the single side relative to the opening area is greater than the first preset length. The copper glue plate 3 and the double-sided board 2 with the inner layer protective film 1 are pasted and laminated to bake to make the The inner layer glue 31 in the copper glue plate 3 melts and overflows and fills the inner layer circuit 5 together with the inner layer protective film 1 in the molten state to obtain a multi-layer board, wherein the copper glue plate 3 includes a pressure plate. The inner layer adhesive 31 and the single panel 32 are combined together. The copper adhesive plate 3 is provided with a first opening 33. The size and shape of the first opening 33 are the same as the opening area. The outer layer circuit 6 is formed on the single panel 32 of the board, wherein the outer layer circuit 6 and the edge of the opening area are separated by a preset distance, and the processed multi-layer board and the outer layer protective film 4 are separated. Positioning and lamination to fully cure the outer layer protective film 4, wherein the outer layer protective film 4 is provided with a second opening in the opening area, and the shape of the second opening is the same as that in the opening area, and The width of the open area on one side is smaller than the second preset length, and the second preset length is smaller than the preset distance, so that the inner layer glue 31 in the copper glue plate 3 melts and overflows and is in the molten state. The inner layer protective film 1 fills the inner layer circuit 5 together, and the outer layer protective film 4 is unilaterally larger than the outer layer circuit 6 by ΔL, ensuring that the circuit is completely covered in the protective film;

Further, by splitting the protective film into inner layer and outer layer design, and processing it on the surface of the circuit board before and after laminating the inner layer glue 31, the filling stability of the inner glue in the open area of the multi-layer flexible circuit board is improved, avoiding Unsatisfactory phenomena such as copper ion migration are caused by the incomplete filling of the glue, which improves the yield and stability of the product;

Further, the present invention increases the cover opening design of the outer layer protective film 4, thereby reducing the overall thickness of the cover opening area of the multi-layer board.

Further, the present invention is different from the back-opening process mentioned in the prior art. Before the single-panel lamination, the inner-layer adhesive is opened at the same time, and then it is laminated and pressed with the double-sided panel, avoiding the need of laser decapping. Cumbersome post-processing procedures such as tearing off, manual inspection, machine inspection, etc., and the introduction of the inner layer protective film design, eliminating the inner layer gap caused by the inner layer gap caused by the incomplete contact between the inner layer glue and the outer layer protective film glue after opening the cover, which leads to poor product function and other risks.

Example 2

The present invention also provides a multi-layer circuit board 100, please refer to FIG. 2 to FIG. 8, the multi-layer circuit board 100 includes a double-sided board 2 layers, a copper glue board 3, and an outer protective film 4, and the double-sided board 2 layers include self- In the first direction, the inner layer protective film 1 and the double-sided board 2 formed with the inner layer circuit 5 are sequentially attached and laminated. The width is greater than the first preset length, and the copper rubber sheet 3 is attached and laminated on the double-sided panel 2 along the first direction. The copper rubber sheet 3 includes inner layer glue 31 which is sequentially attached and laminated along the first direction. and the single panel 32, the single panel 32 is provided with an external circuit, the copper glue plate 3 is provided with a first opening 33, the size and shape of the first opening 33 are the same as the opening area, the inner layer The glue 31 and the inner layer protective film 1 together fill the inner circuit, wherein the outer layer circuit 6 and the edge of the opening area are separated by a preset distance, and the outer layer protective film 4 is attached and laminated along the first direction On the copper rubber sheet 3, the outer protective film 4 is provided with a second opening in the cover opening area. The shape of the second opening is the same as that of the cover opening area, and the width of one side of the opening area is smaller than that of the first opening area. Two preset lengths, the second preset length is smaller than the preset distance.

The double-sided panel 2 includes a first copper layer 21, a first substrate 22 (eg, polyimide), and a second copper layer 23 stacked along the first direction, and the single-sided panel 32 includes stacked layers along the first direction. The third copper layer 321 and the second base material 322 (polyimide).

The multi-layer circuit board 100 may be formed by the processing method including the multi-layer circuit board 100 provided in Embodiment 1, or may be formed by other processing methods, which are not specifically limited herein. Embodiments of the multilayer wiring board 100 may include all embodiments of the above-described processing methods of the multilayer wiring board 100 .

Preferably, the preset distance is D, and D is 0.45±0.1 mm, that is, D is 0.35 mm˜0.55 mm.

In this embodiment, the difference between the second preset length and the preset distance is ΔL of 0.2±0.1mm, that is, ΔL is 0.1mm˜0.3mm, for example, ΔL can be 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.20mm, 0.21mm, or 0.22mm. .

In this embodiment, the second preset length is L2, and L2 is 0.25±0.1 mm.

Obviously, the above-described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, those of ordinary skill in the art can make other changes or changes in different forms without creative work, which shall fall within the protection scope of the present invention.

Claims (10)

1. a processing method of a multilayer circuit board, is characterized in that, comprises the steps: Step S100, aligning and pasting the inner layer protective film on the double-sided board formed with the inner layer circuit to form a double-sided board with an inner layer protective film, wherein the shape of the inner layer protective film is the same as the shape of the opening area And the width of the unilateral relative opening area is greater than the first preset length; Step S200, bonding the copper rubber sheet with the double-sided board with the inner layer protective film and laminating and baking, so that the inner layer glue in the copper rubber sheet is melted and overflowed and shared with the inner layer protective film in the molten state. Filling the inner layer circuit to obtain a multi-layer board, wherein the copper glue plate includes the inner layer glue and a single panel that are pressed together, the copper glue plate is provided with a first opening, and the first opening is The size and shape are the same as the opening area; Step S300, setting and forming an outer layer circuit on the single panel of the multi-layer board, wherein the outer layer circuit and the edge of the cover opening area are separated by a preset distance; Step S400, the multi-layer board and the outer layer protective film processed in step S300 are aligned and laminated, and baked until the outer layer protective film is completely cured, wherein the outer layer protective film is opened when the cover is opened. The area is provided with a second opening, the shape of the second opening is the same as that of the opening area, and the width of one side of the opening area is smaller than a second preset length, and the second preset length is equal to the preset distance. The difference is greater than 0. 2 . The method for processing a multilayer circuit board according to claim 1 , wherein the difference between the second preset length and the preset distance is ΔL, and ΔL is 0.2±0.1 mm. 3 . 3. The method for processing a multilayer circuit board according to claim 1 or 2, wherein the preset distance is D, and D is 0.45±0.1 mm. 4. The method for processing a multilayer circuit board according to claim 1 or 2, wherein before the step S100, the method further comprises the following steps: The protective film is attached to the carrier film and punched to obtain an inner layer protective film with the same shape as that of the opening area and a first preset length of one side opposite to the width of the opening area. 5. The method for processing a multilayer circuit board according to claim 1 or 2, wherein the first preset length is L1, and L1 is 0.70±0.1 mm. 6. The method for processing a multilayer circuit board according to claim 1 or 2, wherein before the step S200, the method further comprises the following steps: The inner layer glue and the single panel are sequentially attached and pressed together to form the copper glue plate, and a first opening is formed by cutting in the open area of the copper glue plate, and the size and shape of the first opening are the same as the open area. 7. The method for processing a multilayer circuit board according to claim 1 or 2, wherein before the step S400, the method further comprises the following steps: A second opening is formed by cutting the outer layer protective film in the cover opening area, the shape of the second opening is the same as that of the cover opening area, and the width of one side of the opening area is smaller than the second preset length. 8. The method for processing a multilayer circuit board according to claim 1 or 2, wherein the second preset length is L2, and L2 is 0.25±0.1 mm. 9. A multilayer circuit board, characterized in that, comprising: The double-sided panel layer includes an inner layer protective film that is sequentially attached and laminated from the first direction and a double-sided panel formed with an inner layer circuit. The shape of the inner layer protective film is the same as the shape of the opening area, and the cover is opened on one side opposite to each other. The width of the area is greater than the first preset length; The copper glue board is pasted and laminated on the double-sided layer along the first direction, and the copper glue plate includes an inner layer glue and a single panel that are successively pasted and laminated along the first direction, and the single plate is provided with For the external circuit, the copper glue plate is provided with a first opening, the size and shape of the first opening are the same as that of the opening area, and the inner layer glue and the inner layer protective film together fill the inner circuit, wherein a preset distance between the outer layer circuit and the edge of the opening area; The outer layer protective film is attached and laminated on the copper glue board along the first direction, the outer layer protective film is provided with a second opening in the opening area, and the shape of the second opening is the same as that in the opening area, And the width of the single side is smaller than the second preset length, and the second preset length is smaller than the preset distance. 10 . The multilayer circuit board according to claim 9 , wherein the difference between the second preset length and the preset distance is ΔL, and ΔL is 0.2±0.1 mm; wherein, The preset distance is D, and D is 0.45±0.1 mm; and/or, The second preset length is L2, and L2 is 0.25±0.1 mm; and/or, The first preset length is L1, and L1 is 0.70±0.1 mm.

Images