A rigid-flexible board with multiple flying tail structures and a preparation method thereof

Abstract

The present invention discloses a rigid-flex board with multiple flying tail structures and a preparation method thereof, comprising the following steps: providing a plurality of core boards, and cutting the plurality of core boards according to a cutting drawing to obtain a plurality of first inner core boards required for production; making inner circuits on the plurality of first inner core boards to obtain a plurality of second inner core boards; grafting covering films on the plurality of second inner core boards and laminating them to obtain a plurality of third inner core boards; affixing blue tapes to the plurality of third inner core boards and performing surface treatment to obtain a plurality of fourth inner core boards; cutting the plurality of fourth inner core boards according to the forming areas to obtain a plurality of fourth inner core boards with flying tails, and affixing PI protective tapes on the flying tails to obtain a plurality of fifth inner core boards; laminating the plurality of fifth inner core boards to obtain a rigid-flex board with multiple flying tail structures. The present invention solves the technical problem that the rigid-flex board with multiple flying tail structures produced by the traditional process has severe indentations.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board preparation, and in particular to a rigid-flexible board with multiple flying tail structures and a preparation method thereof. Background Art

[0002] As electronic products develop towards high density, miniaturization and high reliability, rigid-flex printed circuit boards are particularly suitable for today's electronic products' requirements for lightness, thinness, shortness and smallness due to their bendability, foldability, reduced size, reduced weight and easy assembly. In the PCB industry, rigid-flex boards with flying tail structures are a type of printed circuit board that has grown very rapidly in recent years, with a fast growth rate and broad market prospects. However, as time goes by, the market is no longer satisfied with a single flying tail structure, but is developing towards a structure with multiple flying tails.

[0003] Rigid-flex boards with multiple flying tails produced by traditional production processes generally have serious indentations, and may even be scrapped due to indentations. As the number of rigid-flex boards with multiple flying tails increases, customer requirements have also changed from concessions to strict requirements.

[0004] Therefore, traditional production processes can no longer meet existing market requirements. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a rigid-flexible composite board with multiple flying tail structures and a preparation method thereof, which is used to solve the technical problem that the rigid-flexible composite board with multiple flying tail structures produced by traditional processes has severe indentations, thereby achieving the purpose of improving the quality of the rigid-flexible composite board with multiple flying tail structures.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a rigid-flexible board with multiple flying tail structures comprises the following steps:

[0008] Providing a plurality of core boards, and cutting the plurality of core boards according to the cutting drawing to obtain a plurality of first inner core boards required for production;

[0009] Making inner layer circuits on the plurality of first inner layer core boards to obtain a plurality of second inner layer core boards;

[0010] Grafting covering films onto the plurality of second inner core panels to obtain a plurality of third inner core panels;

[0011] affixing blue tape to the plurality of third inner core boards and performing surface treatment to obtain a plurality of fourth inner core boards;

[0012] Cutting the plurality of fourth inner core panels according to the forming area to obtain a plurality of fourth inner core panels with flying tails, and attaching PI protective tapes to the flying tails to obtain a plurality of fifth inner core panels;

[0013] After the plurality of fifth inner core boards are pressed together, the rigid-flex board with multiple flying tail structures is obtained.

[0014] As a preferred embodiment of the present invention, when inner layer circuits are manufactured on the plurality of first inner layer core boards, the process includes:

[0015] Pre-processing the plurality of first inner core panels;

[0016] A dry film is attached to the plurality of first inner core boards that have been pre-treated, and corresponding circuit patterns are obtained after alignment, exposure and development;

[0017] Etching the plurality of first inner core boards according to the circuit pattern;

[0018] Punching rivet holes and performing blackening to obtain the plurality of second inner core panels.

[0019] As a preferred embodiment of the present invention, when inner layer circuits are manufactured on the plurality of first inner layer core boards, the method further comprises:

[0020] Determining the thickness of the dry film according to the line width and line spacing in the required circuit pattern;

[0021] Exposing the dry film using an LDI exposure machine;

[0022] The plurality of first inner core boards are etched using an acid solution.

[0023] As a preferred embodiment of the present invention, when the covering films are grafted onto the plurality of second inner core panels, the method includes:

[0024] Aligning the covering film on the plurality of second inner core plates according to the etching identification lines;

[0025] Laminating the aligned covering film to the plurality of second inner core plates;

[0026] Using a fixing device to fix the covering film on the plurality of second inner core panels;

[0027] The plurality of second inner core panels with the covering films fixed thereon are sent into an oven to cure the glue on the covering films to obtain the plurality of third inner core panels.

[0028] As a preferred embodiment of the present invention, when the covering film is grafted onto the plurality of second inner core panels, it further comprises:

[0029] Before alignment, the plurality of second inner core plates are placed in a clean room, and surfaces of the plurality of second inner core plates are cleaned with a cleaning liquid;

[0030] Before being sent into the oven, a press is used to exhaust the air between the covering film and the plurality of second inner core plates, so that the glue of the covering film is bonded to the plurality of second inner core plates.

[0031] As a preferred embodiment of the present invention, when affixing blue tape to the plurality of third inner core panels, the method includes:

[0032] Paste blue tape on the entire boards of the plurality of third inner core boards, and open windows on the blue tape at finger positions of the plurality of third inner core boards;

[0033] Chemically clean the third inner core boards with blue tapes attached thereto, and after nickel-gold deposition thereon, remove the blue tapes and inspect the effect of nickel-gold deposition;

[0034] Characters are printed on a plurality of third inner core boards deposited with nickel and gold, and the characters are cured to obtain the plurality of fourth inner core boards.

[0035] As a preferred embodiment of the present invention, the weight of the blue tape is 30-70 grams.

[0036] As a preferred embodiment of the present invention, when the plurality of fourth inner core panels are cut according to the forming areas, the method includes:

[0037] The plurality of fourth inner core panels with flying tails are formed by cutting along the outer contour lines on the flexible regions of the plurality of fourth inner core panels by die punching or laser forming.

[0038] As a preferred embodiment of the present invention, when affixing the PI protective tape on the tail, it includes:

[0039] Selecting the thickness of the PI protective tape;

[0040] Determine the size of the PI protective tape according to the size of the finger to be protected;

[0041] Attaching the preformed PI protective tape to the covering film at the tail;

[0042] The thickness of the PI protective tape can be selected in the range of 50um, 80um and 100um.

[0043] A rigid-flexible board with multiple flying tail structures is prepared by the above-mentioned preparation method.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The preparation method provided by the present invention can effectively remove the indentation of the rigid-flexible board with a flying tail structure, thereby improving the quality of the rigid-flexible board;

[0046] (2) The rigid-flex board with a flying tail structure obtained by the present invention can not only meet the high requirements of customers, but also has strong competitiveness in the market.

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 - is a step diagram of a method for preparing a rigid-flexible board with multiple flying tail structures according to an embodiment of the present invention;

[0049] Figure 2 - is a schematic diagram of a second inner core board in a method for preparing a rigid-flex board with multiple flying tail structures according to an embodiment of the present invention;

[0050] Figure 3 - is a schematic diagram of a third inner core board in a method for preparing a rigid-flex board with multiple flying tail structures according to an embodiment of the present invention;

[0051] Figure 4 - is a schematic diagram of a fourth inner core board in a method for preparing a rigid-flex board with multiple flying tail structures according to an embodiment of the present invention;

[0052] Figure 5 - is a schematic diagram of a fourth inner core board with flying tails in a method for preparing a rigid-flex board with multiple flying tail structures according to an embodiment of the present invention;

[0053] Figure 6 - is a schematic diagram of a fifth inner core board in a method for preparing a rigid-flex board with multiple flying tail structures according to an embodiment of the present invention;

[0054] Figure 7 - is a physical picture of the flying tail structure of an embodiment of the present invention.

[0055] Explanation of the figure numbers: 1. Inner layer circuit; 2. Rivet hole; 3. Cover film; 4. Blue tape; 5. Finger; 6. Molding area; 7. Flying tail; 8. PI protective tape. DETAILED DESCRIPTION

[0056] The present invention provides a method for preparing a rigid-flexible board with multiple flying tail structures, such as Figure 1 As shown, the following steps are included:

[0057] Step S1: providing a plurality of core boards, and cutting the plurality of core boards according to a cutting drawing to obtain a plurality of first inner core boards required for production;

[0058] Step S2: making inner layer circuits on a plurality of first inner layer core boards to obtain a plurality of second inner layer core boards;

[0059] Step S3: Grafting the covering film 3 onto a plurality of second inner core panels to obtain a plurality of third inner core panels;

[0060] Step S4: affixing blue tape 4 to a plurality of third inner core boards and performing surface treatment to obtain a plurality of fourth inner core boards;

[0061] Step S5: cutting a plurality of fourth inner core panels according to the forming area 6 to obtain a plurality of fourth inner core panels with a tail portion 7, and attaching a PI protective tape to the tail portion 7 to obtain a plurality of fifth inner core panels;

[0062] Step S6: After pressing together a plurality of fifth inner core boards, a rigid-flex board with a plurality of flying tail structures is obtained.

[0063] The present invention solves the problem of severe indentation at the tail 7 by adding a PI protective tape 8 of corresponding thickness at the tail position of the inner layer in coordination with the remaining process steps, further meets customer requirements and enhances the market competitiveness of the product.

[0064] In the above step S2, when the inner layer circuit 1 is manufactured on a plurality of first inner layer core boards, it includes:

[0065] Pre-treating a plurality of first inner core panels;

[0066] A dry film is attached to a plurality of first inner core boards that have been pre-treated, and corresponding circuit patterns are obtained after alignment, exposure and development;

[0067] Etching a plurality of first inner core boards according to circuit patterns;

[0068] Punch rivet holes 2 and perform blackening to obtain a plurality of second inner core plates, such as Figure 2 shown.

[0069] The black oxidation process is a key technology for the production of multi-layer printed circuit boards. Among them, black oxidation is the key step of the entire blackening process; the purpose of black oxidation is to form a uniform, dense, and appropriately long needle-shaped oxide crystal layer on the copper surface, increase the specific surface area of ​​the copper surface, and enhance the adhesion between the copper surface and the prepreg resin, thereby improving the interlayer bonding strength of the board. The chemical reaction mechanism is as follows:

[0070]

[0071] Cu2O+H2O=Cu(OH)2+Cu (2);

[0072]

[0073] Overall reaction equation: 3Cu+NaClO2=CuO+Cu2O+NaCl

[0074] The blackening process formula adopted by the present invention is:

[0075] NaClO2 40~48g / L; NaOH 7~14g / L; Na3PO4 7~15g / L; temperature 90~100℃; time 5~7min.

[0076] The temperature used in the formulation of the present invention is relatively high, which can easily cause deformation of the inner core board lining, so the processing time should not be too long, and should not exceed 7 minutes.

[0077] Furthermore, when the inner layer circuit 1 is manufactured on a plurality of first inner layer core boards, it also includes:

[0078] Determine the thickness of the dry film according to the line width and line spacing in the required circuit pattern;

[0079] The dry film is exposed using an LDI exposure machine;

[0080] Acid solution is used to etch a plurality of first inner core boards.

[0081] The LDI exposure machine uses laser to directly scan the image of the printed circuit board (PCB) onto a photosensitive dry film. Since no photographic film is required, the size deviation caused by the expansion and contraction of the film and the deviation caused by the non-parallel light during exposure are avoided, while providing high flexibility and high precision.

[0082] In the above step S3, when the covering film is grafted onto a plurality of second inner core panels, the process includes:

[0083] Align the cover film 3 on the plurality of second inner core plates according to the etching identification lines;

[0084] Laminating the aligned covering film 3 to a plurality of second inner core plates;

[0085] Using a fixing device to fix the covering film 3 on a plurality of second inner core panels;

[0086] The plurality of second inner core plates with the cover film 3 fixed thereon are sent into an oven to cure the glue on the cover film 3 to obtain a plurality of third inner core plates, such as Figure 3 shown.

[0087] Further, the fixing device comprises a trouser press or an iron.

[0088] Furthermore, when the covering film 3 is grafted onto a plurality of second inner core panels, the method further comprises:

[0089] Before alignment, a plurality of second inner core plates are placed in a clean room, and surfaces of the plurality of second inner core plates are cleaned with a cleaning liquid;

[0090] Before being sent into the oven, a press is used to exhaust the air between the covering film and the plurality of second inner core boards, so that the glue of the covering film 3 is bonded to the plurality of second inner core boards.

[0091] Preferably, the cleaning fluid is alcohol.

[0092] In the above step S4, when affixing the blue tape 4 to a plurality of third inner core panels, it includes:

[0093] A blue tape 4 is pasted on the entire board of the third inner core board, and a window is opened on the blue tape 4 at the finger 5 position of the third inner core board;

[0094] Chemically clean the third inner core boards with the blue tape 4, and after nickel-gold deposition, remove the blue tape 4 and check the effect of nickel-gold deposition;

[0095] Characters are printed on a plurality of third inner core boards deposited with nickel and gold, and the characters are cured to obtain a plurality of fourth inner core boards, such as Figure 4 shown.

[0096] Furthermore, the weight of the blue tape 4 is 30-70 grams of low-viscosity blue tape 4, and the thickness of the nickel-gold immersion is made according to customer requirements.

[0097] Blue tape 4 is actually the common name for peelable solder mask ink. It is a single-component thermosetting ink without diluent. It is a relatively new special material for printed circuit boards. It is mainly used as a protective layer for gold fingers, partial gold plating and plugging holes during hot air leveling.

[0098] Adopting blue tape 4 in the present invention has the following advantages:

[0099] (1) Save manpower and improve production efficiency: The blue glue process adopts the screen printing production method commonly used in the circuit board PCB industry, which can replace the high-temperature tape production method;

[0100] (2) Simple curing method: Blue tape 4 is a heat-curing ink, which is cured in a vertical oven / tunnel oven at 100-150°C / 30 minutes.

[0101] (3) Good high temperature resistance: the cured blue tape 4 can withstand temperatures from 50°C to below 280°C;

[0102] (4) Easy to peel: Normal parameters plus baked blue tape 4, easy to peel and good toughness, can be removed manually without secondary cleaning.

[0103] Blue tape 4 production process and subsequent process requirements:

[0104] (1) Thickness of blue tape 4: The thickness of the plug hole position is usually >1300um, and the local gold plating and gold finger position usually need to be ≥200um. In particular, the thickness of the blue tape 4 that needs to go through the hot air leveling process usually needs to be guaranteed to be above 300um to avoid poor tinning in the protection area under the blue tape 4 when subjected to thermal shock.

[0105] (2) Alignment of blue tape 4: The position of the blue tape 4 is not allowed to leak the protection zone pads, and SMT pads are not allowed. Pads that are not designed to be covered with blue tape 4 are not allowed to be covered with blue tape;

[0106] (3) The PTH hole position of the blue tape 4 is not designed, and blue tape is not allowed to enter the hole. The area of ​​the blue tape 4 must be peeled off cleanly at one time without any residue.

[0107] Immersion nickel gold is a process of chemically plating nickel and chemically immersing gold on the bare copper surface of the printed circuit board pad. The coating has good contact conductivity and assembly welding performance, and can also be used in conjunction with other surface treatment processes. The principles of the immersion nickel gold process include:

[0108] Principle of chemical nickel plating: Under the catalytic action of Pd, Ni 2+ It is reduced by hypophosphite (NaH2PO2) to metallic Ni and deposited on the copper surface. 2+ When the Pd crystals covering the catalyst are deposited, the newly formed Ni acts as a catalyst to continue to promote the reaction, thereby obtaining a nickel coating of any thickness. The specific reaction mechanism is as follows:

[0109] Anode reaction: H2PO2+H2O→HPO3 2- +3H - +2e (1);

[0110] Cathode reaction: Ni 2+ +2e→Ni (2);

[0111] H2PO2+2H + +e→P+2H2O (3);

[0112] Principle of chemical immersion gold: On the active nickel surface, Au(CN) 2- The complex ions undergo a chemical replacement reaction with Ni, depositing a thin layer of gold on the nickel layer. The reaction mechanism is as follows:

[0113] 2Au(CN) 2- +Ni→2Au+Ni 2+ +4CN - (4);

[0114] Because △E 0=0.289V>0V, which is a spontaneous reaction. When one nickel atom is dissolved, two gold atoms will be deposited on the nickel layer.

[0115] In the above step S5, when the plurality of fourth inner core panels are cut according to the forming area 6, the method includes: using a die punching or laser forming to cut along the outer shape line on the flexible area of ​​the plurality of fourth inner core panels to form a plurality of fourth inner core panels with a flying tail 7, such as Figure 5 and Figure 7 shown.

[0116] Laser forming is the most widely used laser processing technology. Its principle is to irradiate the material with laser polymerization, so that the temperature of the material rises sharply to melt or vaporize. With the relative movement of the laser and the material to be cut, a slit is formed on the cut material to achieve the purpose of cutting. It uses the principle of laser ablation, and laser ablation is essentially the thermal effect or chemical effect of light. Laser forming has the following advantages:

[0117] (1) No cutting stress

[0118] Since laser forming uses a non-contact material processing method, there is no cutting stress. For thin plates and soft plates, shape deviation and precision deviation caused by plate deformation can be avoided.

[0119] (2) Higher processing accuracy

[0120] Since there is no cutting stress, higher processing accuracy can be obtained, and the theoretical processing accuracy can reach ±1mil.

[0121] (3) Narrower incision

[0122] The laser spot diameter is much smaller than the milling cutter diameter, so the cut is narrower, which is suitable for processing micro panels.

[0123] (4) Depth control

[0124] Since the laser uses a non-contact material processing method, the cutting depth can be controlled by parameters such as cutting speed, pulse frequency, and number of cuts. Therefore, adjusting these parameters can achieve precise control of the depth.

[0125] In the above step S5, when the PI protective tape 8 is attached to the tail portion 7, the steps include: selecting the thickness of the PI protective tape; determining the size of the PI protective tape 8 according to the size of the finger to be protected; attaching the pre-formed PI protective tape 8 to the covering film of the tail portion 7, such as Figure 6 As shown;

[0126] The thickness of the polyimide film (PI) protective tape can be selected in the range of 50um, 80um and 100um.

[0127] PI protective tape has the advantages of good adhesion, good conformability, high and low temperature resistance, solvent resistance, abrasion resistance, no residual adhesive left on the masked surface after tearing off, and excellent electrical properties. Short-term temperature resistance can reach 300℃, long-term temperature resistance can reach 250℃, high tensile strength, good chemical resistance, and RoHS compliance.

[0128] The rigid-flex board with multiple flying tail structures provided by the present invention is prepared by the above-mentioned preparation method.

[0129] Compared with the prior art, the present invention has the following beneficial effects:

[0130] (1) The preparation method provided by the present invention can effectively remove the indentation of the rigid-flexible board with a flying tail structure, thereby improving the quality of the rigid-flexible board;

[0131] (2) The rigid-flex board with a flying tail structure obtained by the present invention can not only meet the high requirements of customers, but also has strong competitiveness in the market.

[0132] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for preparing a rigid-flex board with multiple flying tail structures, characterized in that: The following steps are involved: Providing a plurality of core boards, and cutting the plurality of core boards according to the cutting drawing to obtain a plurality of first inner core boards required for production; Making inner layer circuits on the plurality of first inner layer core boards to obtain a plurality of second inner layer core boards; Grafting covering films onto the plurality of second inner core panels to obtain a plurality of third inner core panels; affixing blue tape to the plurality of third inner core boards and performing surface treatment to obtain a plurality of fourth inner core boards; Cutting the plurality of fourth inner core panels according to the forming area to obtain a plurality of fourth inner core panels with flying tails, and attaching PI protective tapes to the flying tails to obtain a plurality of fifth inner core panels; After pressing the plurality of fifth inner core boards together, the rigid-flex board with multiple flying tail structures is obtained; Wherein, when the PI protective tape is attached to the tail, it includes: Selecting the thickness of the PI protective tape; Determine the size of the PI protective tape according to the size of the finger to be protected; Attaching the preformed PI protective tape to the covering film at the tail; The thickness of the PI protective tape can be selected in the range of 50um, 80um and 100um.

2. The method for preparing a rigid-flex board with multiple flying tail structures according to claim 1, characterized in that: When inner layer circuits are fabricated on the plurality of first inner layer core boards, the method includes: Pre-processing the plurality of first inner core panels; A dry film is attached to the plurality of first inner core boards that have been pre-treated, and corresponding circuit patterns are obtained after alignment, exposure and development; Etching the plurality of first inner core boards according to the circuit pattern; Punching rivet holes and performing blackening to obtain the plurality of second inner core panels.

3. The method for preparing a rigid-flex board with multiple flying tail structures according to claim 2, characterized in that: When inner layer circuits are fabricated on the plurality of first inner layer core boards, the method further comprises: Determining the thickness of the dry film according to the line width and line spacing in the required circuit pattern; Exposing the dry film using an LDI exposure machine; The plurality of first inner core boards are etched using an acid solution.

4. The method for preparing a rigid-flex board with multiple flying tail structures according to any one of claims 1 to 3, characterized in that: When the covering films are grafted onto the plurality of second inner core panels, the method comprises: Aligning the covering film on the plurality of second inner core plates according to the etching identification lines; Laminating the aligned covering film to the plurality of second inner core plates; Using a fixing device to fix the covering film on the plurality of second inner core panels; The plurality of second inner core panels with the covering films fixed thereon are sent into an oven to cure the glue on the covering films to obtain the plurality of third inner core panels.

5. The method for preparing a rigid-flex board with multiple flying tail structures according to claim 4, characterized in that: When the covering films are grafted onto the plurality of second inner core panels, the method further comprises: Before alignment, the plurality of second inner core plates are placed in a clean room, and surfaces of the plurality of second inner core plates are cleaned with a cleaning liquid; Before being sent into the oven, a press is used to exhaust the air between the covering film and the plurality of second inner core plates, so that the glue of the covering film is bonded to the plurality of second inner core plates.

6. The method for preparing a rigid-flex board with multiple flying tail structures according to claim 4, characterized in that: When affixing blue tape to the plurality of third inner core panels, the method includes: Paste blue tape on the entire boards of the plurality of third inner core boards, and open windows on the blue tape at finger positions of the plurality of third inner core boards; Chemically clean the third inner core boards with blue tapes attached thereto, and after nickel-gold deposition thereon, remove the blue tapes and inspect the effect of nickel-gold deposition; Characters are printed on a plurality of third inner core boards deposited with nickel and gold, and the characters are cured to obtain the plurality of fourth inner core boards.

7. The method for preparing a rigid-flex board with multiple flying tail structures according to claim 6, characterized in that: The blue tape weighs 30-70 grams.

8. The method for preparing a rigid-flex board with multiple flying tail structures according to claim 1, characterized in that: When the plurality of fourth inner core panels are cut according to the forming areas, the method includes: The plurality of fourth inner core panels with flying tails are formed by cutting along the outer contour lines on the flexible regions of the plurality of fourth inner core panels by die punching or laser forming.

9. A rigid-flex board with multiple flying tail structures, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

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