CN113179597A - Rigid-flexible circuit board and manufacturing method thereof - Google Patents
Rigid-flexible circuit board and manufacturing method thereof Download PDFInfo
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- CN113179597A CN113179597A CN202110434301.5A CN202110434301A CN113179597A CN 113179597 A CN113179597 A CN 113179597A CN 202110434301 A CN202110434301 A CN 202110434301A CN 113179597 A CN113179597 A CN 113179597A
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- flexible printed
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- 239000002184 metal Substances 0.000 claims abstract description 95
- 229910052751 metal Inorganic materials 0.000 claims abstract description 95
- 238000000034 method Methods 0.000 claims abstract description 48
- 229910000679 solder Inorganic materials 0.000 claims abstract description 38
- 238000005476 soldering Methods 0.000 claims abstract description 19
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000002844 melting Methods 0.000 claims abstract description 7
- 230000008018 melting Effects 0.000 claims abstract description 7
- 239000000178 monomer Substances 0.000 claims description 46
- 239000002390 adhesive tape Substances 0.000 claims description 14
- 238000003466 welding Methods 0.000 claims description 11
- 229910000831 Steel Inorganic materials 0.000 claims description 9
- 239000010959 steel Substances 0.000 claims description 9
- 230000000149 penetrating effect Effects 0.000 claims description 6
- 238000001465 metallisation Methods 0.000 claims description 4
- 230000032683 aging Effects 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 abstract description 7
- 239000010410 layer Substances 0.000 description 45
- 239000000047 product Substances 0.000 description 13
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 11
- 239000011889 copper foil Substances 0.000 description 10
- 238000007689 inspection Methods 0.000 description 7
- 239000000758 substrate Substances 0.000 description 6
- 238000001816 cooling Methods 0.000 description 4
- 229910000597 tin-copper alloy Inorganic materials 0.000 description 4
- 229920002799 BoPET Polymers 0.000 description 2
- 239000005041 Mylar™ Substances 0.000 description 2
- 238000003848 UV Light-Curing Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000002355 dual-layer Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/46—Manufacturing multilayer circuits
- H05K3/4611—Manufacturing multilayer circuits by laminating two or more circuit boards
- H05K3/4614—Manufacturing multilayer circuits by laminating two or more circuit boards the electrical connections between the circuit boards being made during lamination
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/11—Printed elements for providing electric connections to or between printed circuits
- H05K1/115—Via connections; Lands around holes or via connections
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
- H05K3/42—Plated through-holes or plated via connections
- H05K3/429—Plated through-holes specially for multilayer circuits, e.g. having connections to inner circuit layers
Abstract
The invention belongs to the technical field of circuit boards and processing thereof, and particularly relates to a manufacturing method of a rigid-flexible circuit board, which comprises the following steps: (1) preparing and pretreating a rigid printed circuit board, and pre-implanting solder balls on each single metal pad; (2) preparing and pretreating a flexible printed circuit board; (3) respectively stacking the rigid printed circuit board and the flexible printed circuit board which are obtained through the pretreatment in the step (1) and the step (2) together and pre-fixing the rigid printed circuit board and the flexible printed circuit board into a whole; (4) and (4) placing the rigid printed circuit board and the flexible printed circuit board which are pre-fixed together in the step (3) into a constant-temperature laser soldering machine for tin melting connection processing to obtain the soft-hard combined circuit board. Compared with the prior art of the same type, the invention has simple process and less working procedures, and is beneficial to saving the processing cost; the rigid-flexible circuit board obtained by the manufacturing method has a simple structure and small overall thickness, and is beneficial to realizing the light and thin design of a terminal product applying the rigid-flexible circuit board.
Description
Technical Field
The invention relates to the technical field of circuit boards and processing thereof, in particular to a rigid-flexible circuit board and a manufacturing method thereof.
Background
With the rapid development of electronic products, electronic terminal products tend to be designed to be more and more light and thin, resulting in compact internal space layout of the terminal, and more circuit boards using soft and hard combination are required to meet the connection requirements of functional components. The soft-hard combined circuit board is used as a high-end product in the printed circuit board, and the manufacturing cost of the whole terminal product is high due to the high manufacturing cost. In addition, the rigid-flexible circuit board belongs to an integrally formed customized hardware product, and when the internal structure of the terminal product is changed, the rigid-flexible circuit board needs to be structurally designed again, so that a large amount of resources are wasted. And two kinds of printed circuit board's of ordinary rigid-flexible connected mode, generally connect with Connector, Connector connects and need weld Plug and Socket on rigid-flexible printed circuit board both respectively, and the material cost and the welding cost of Plug and Socket can promote terminal material cost greatly, and Connector connects and compare in the soft or hard combination board, and Plug and Socket need occupy extra space, are difficult to realize terminal product's frivolousization, can't replace the soft or hard combination circuit board.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a manufacturing method of a rigid-flexible circuit board, which aims to solve the problem that the existing rigid-flexible circuit board is high in manufacturing cost.
The other purpose is to provide a soft and hard combined circuit board manufactured by the method.
In order to achieve one of the purposes, the invention adopts the technical scheme that: a manufacturing method of a rigid-flexible circuit board comprises the following steps:
(1) preparing a rigid printed circuit board, processing two rows of metal pads positioned at the tail end of a circuit on the rigid printed circuit board, wherein each row of metal pads comprises a plurality of single metal pads, and pre-planting solder balls on each single metal pad;
(2) preparing a flexible printed circuit board, processing two rows of double-layer connecting pads which are positioned at the tail end of a circuit and respectively correspond to two rows of metal pads on the flexible printed circuit board, wherein the number of the single connecting pads contained by each row of double-layer connecting pads is consistent with the number and positions of the single metal pads contained by each row of metal pads, and processing metallized through holes penetrating through the flexible printed circuit board in each single connecting pad, wherein the through holes communicate the two single connecting pads at the corresponding positions on each row of double-layer connecting pads;
(3) respectively stacking the rigid printed circuit board and the flexible printed circuit board which are obtained through the pretreatment in the step (1) and the step (2) together, respectively aligning the single metal pad in each row of metal pads with the single connection pad in one layer of connection pads of each row of double-layer connection pads at the corresponding position, and pre-fixing the rigid printed circuit board and the flexible printed circuit board into a whole;
(4) and (3) placing the rigid printed circuit board and the flexible printed circuit board which are pre-fixed together in the step (3) into a constant-temperature laser soldering machine for tin melting connection processing, wherein the pre-planted solder balls are melted and then flow through the through holes, and fixedly connecting each row of metal pads with the double-layer connection pads at the corresponding positions together to obtain the circuit board with soft and hard combination.
Preferably, after the step (1) and before the step (2), the method further comprises the step (1 a): two gold-plated positioning marks are processed on the rigid printed circuit board.
Preferably, after the step (2) and before the step (3), the method further comprises the step (2 a): processing two positioning holes respectively corresponding to the two gold-plated positioning marks on the flexible printed circuit board; when the rigid printed circuit board and the flexible printed circuit board are stacked together, the two gold-plated positioning marks are respectively aligned with the two positioning holes.
Preferably, the method further comprises the step (2 b): arranging a piece of double-sided adhesive tape on the surface of the flexible printed circuit board, which is attached to the rigid printed circuit board; tearing off release paper on the double-sided adhesive tape, and after the rigid printed circuit board and the flexible printed circuit board are aligned through the gold-plated positioning marks and the positioning holes, adhering the rigid printed circuit board and the flexible printed circuit board together, namely, realizing the pre-fixation of the rigid printed circuit board and the flexible printed circuit board through the double-sided adhesive tape.
Preferably, the two connection pads of each row of the two connection pads are respectively processed on two surfaces of the flexible printed circuit board.
Preferably, the distance between each row of metal pads and the edge of the end part of the rigid printed circuit board is more than or equal to 0.3 mm; the single metal pads are circular, the diameter of each single metal pad is 0.35mm, and the distance between every two adjacent single metal pads is larger than or equal to 0.25 mm.
Preferably, the pre-planting of the solder balls comprises a printing process and a reflow soldering process; the printing process adopts a solder paste printing machine for processing, a steel mesh with the thickness of 80 microns is adopted for printing, the height of the steel mesh is 0-100 microns away from a product, the angle of a scraper adopted by the solder paste printing machine is 60 +/-5 degrees, and the advancing speed of the scraper is set to be 75 +/-25 mm/s; the reflow soldering process adopts a reflow oven to process, the oven temperature is less than or equal to 245 ℃, and the advancing speed of the reflow oven is 900 mm/min-950 mm/min.
Preferably, the positioning holes corresponding to the gold-plating positioning marks are circular, and the diameters of the positioning holes are 0.8mm and 0.9mm respectively.
Preferably, the distance between each row of connecting pads and the edge of the end part of the flexible printed circuit board is more than or equal to 0.2 mm; the monomer connecting pad is circular, and the diameter of the monomer connecting pad is 0.3 mm; the through-hole is the circular port, and it is coaxial setting with monomer connection pad, and the diameter is 0.13mm after the metallization.
Preferably, the thickness of the double-sided adhesive tape is less than or equal to 50 mu m, and the initial viscosity of the double-sided adhesive tape is more than or equal to 5.2N/10 mm; the aging viscosity is more than or equal to 6.9N/10mm after 14 days; the process can be repeated twice.
Preferably, the laser wavelength of the constant-temperature laser soldering machine is 915 nm; the laser power is more than or equal to 30W; the welding mode is single-point continuous welding; the temperature control mode needs to meet the requirement of constant temperature control; the single spot welding time is less than or equal to 200 ms.
In order to achieve the second purpose, the invention adopts the technical scheme that: a soft and hard combined circuit board is manufactured by the manufacturing method and comprises a rigid printed circuit board and a flexible printed circuit board which are stacked together; two rows of metal pads are arranged in one surface of the rigid printed circuit board, each row of metal pads comprises a plurality of single metal pads, and a solder ball is arranged on each single metal pad; the flexible printed circuit board is provided with two rows of double-layer connecting pads corresponding to two rows of metal pads respectively, the number of the monomer connecting pads contained by each layer of double-layer connecting pad is consistent with the number and the positions of the monomer metal pads contained by each row of metal pad, a through hole penetrating through the flexible printed circuit board is arranged in each monomer connecting pad, the through hole is used for communicating the two monomer connecting pads at the corresponding positions on each row of double-layer connecting pads, and the monomer metal pads in each row of metal pads are aligned with the monomer connecting pads in one layer of connecting pads of each row of double-layer connecting pads at the corresponding positions respectively; the melted solder balls connect the corresponding monomer metal pads and the monomer connecting pads together.
Preferably, two gold-plated positioning marks are arranged on the rigid printed circuit board, and two positioning holes respectively corresponding to the two gold-plated positioning marks are arranged on the flexible printed circuit board; the two gold-plated positioning marks are respectively aligned with the two positioning holes.
Preferably, a piece of double-sided tape for pre-fixing with the rigid printed circuit board is provided on one surface of the flexible printed circuit board.
The beneficial technical effects are as follows: the rigid printed circuit board and the flexible printed circuit board required by the invention both adopt the existing conventional products without customization, the proper rigid printed circuit board and the proper flexible printed circuit board are selected, a plurality of corresponding monomer metal pads and connecting pads are respectively processed on the rigid printed circuit board and the flexible printed circuit board according to the design requirements, the solder balls are pre-planted on the surface of each monomer metal pad, the metalized through holes are processed in each monomer connecting pad, when the rigid printed circuit board and the flexible printed circuit board are assembled, the monomer metal pads are aligned with the monomer connecting pads, the pre-planted solder balls on the metal pads are positioned between the metal pads and the connecting pads, the assembled and pre-fixed rigid printed circuit board and the flexible printed circuit board are placed in a laser constant temperature soldering machine for tin melting connection processing, the pre-planted solder balls flow through the metalized through holes after being melted, and each row of metal pads are fixedly connected with the double-layer connecting pads at the corresponding positions, obtaining a soft and hard combined circuit board; compared with the prior art of the same type, the invention has simple process and less working procedures, and is beneficial to saving the processing cost; the rigid-flexible circuit board obtained by the manufacturing method has a simple structure and small overall thickness, and is beneficial to realizing the light and thin design of a terminal product applying the rigid-flexible circuit board.
Drawings
FIG. 1 is a front view of a rigid printed circuit board according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;
FIG. 3 is a front view of a flexible printed circuit board of an embodiment of the present invention;
FIG. 4 is a cross-sectional view taken along line B-B of FIG. 3;
FIG. 5 is a front view of an assembled state of an embodiment of the present invention;
fig. 6 is a cross-sectional view taken along line C-C of fig. 5.
Detailed Description
In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings and embodiments.
As shown in fig. 5 to 6, the embodiment of the present invention provides a rigid-flex circuit board, which includes a rigid printed circuit board 1 and a flexible printed circuit board 3 stacked together.
As shown in fig. 1-2, two rows of metal pads 2 are disposed in one surface of the rigid printed circuit board 1, each row of metal pads includes a plurality of single metal pads 201, and a solder ball is disposed on each single metal pad 201; two rows of metal pads 2 are respectively positioned at the bottom and the top of one surface of the rigid printed circuit board 1; the rigid printed circuit board 1 of the embodiment is a conventional printed circuit board which comprises a substrate layer, a copper foil layer and a solder mask layer, wherein a single metal pad 201 is formed by arranging two rows of metal pads 2 at the tail end of a circuit according to design requirements and wiring requirements; and processing the solder mask layer, and exposing a copper foil at a set position, wherein the exposed copper foil is the single metal pad 201.
As shown in fig. 3-4, two rows of double-layer connection pads 4 corresponding to two rows of metal pads 2 are disposed on the flexible printed circuit board 3, the number and the positions of the single-body connection pads 401a included in each layer connection pad401 of each row of double-layer connection pads are the same as those of the single-body metal pads 201 included in each row of metal pads 2, a metalized through hole 5 penetrating through the flexible printed circuit board 3 is disposed in each single-body connection pad401a, and the through hole 5 communicates the two single-body connection pads 401a at the corresponding positions on each row of double-layer connection pads 4, for example, referring to fig. 4, the two single-body connection pads 401a at the second position from the left are the two single-body connection pads at the corresponding positions on each row of double-layer connection pads 4, and the two single-body connection pads are communicated with each other through the through hole 5; the flexible printed circuit board 3 of the embodiment also adopts a conventional flexible printed circuit board, which comprises a substrate layer, a copper foil layer and a solder mask layer, wherein the single connection pad401a is formed by arranging two rows of double-layer connection pads 4 at the tail end of a circuit according to design requirements and wiring requirements; and processing the solder mask layer and the substrate layer, exposing copper foils at set positions, wherein the exposed copper foils are single connection pads 401a, and two connection pads included in each row of double-layer connection pads 4 are respectively positioned in two surfaces of the flexible printed circuit board 3. The single connection pad401a is circular, and the through hole 5 is processed therein by using a conventional flexible printed circuit board metallization through hole processing process, so that the single connection pad401a is substantially a metal ring.
As shown in fig. 5-6, during assembly, the rigid printed circuit board 1 and the flexible printed circuit board 3 are stacked together, and the single metal pad 201 in each row of metal pads 2 is aligned with the single connection pad401a in one of the connection pads 401 of each row of double-layer connection pads at the corresponding position; the melted solder balls connect and conduct the corresponding single metal pad 201 and the single connecting pad401a together to form the same network, and the soft-hard combined circuit board is obtained.
In order to realize the rapid positioning of the rigid printed circuit board 1 and the flexible printed circuit board 3, two gold-plated positioning marks 6 are arranged on the rigid printed circuit board, and two positioning holes 7 respectively corresponding to the two gold-plated positioning marks 6 are arranged on the flexible printed circuit board 3; the two gold-plated positioning marks 6 are respectively aligned with the two positioning holes 7. The gold-plated positioning marks 6 are arranged according to actual requirements, for example, the gold-plated positioning marks 6 are arranged on diagonal lines of the rigid printed circuit board 1, or a connecting line of two gold-plated positioning marks 6 is neither parallel to nor perpendicular to edges of two ends of the rigid printed circuit board 1, and the arrangement of the positioning holes 7 is consistent with that of the gold-plated positioning marks 6.
As shown in fig. 3, in order to pre-fix the rigid pcb 1 and the flexible pcb 3 after alignment, a double-sided tape 8 for pre-fixing the rigid pcb 1 is disposed on one surface of the flexible pcb 3, and specifically, the double-sided tape is attached to the surface of the flexible pcb 3 attached to the rigid pcb 1.
As shown in fig. 1 to 6, an embodiment of the present invention further provides a method for manufacturing a rigid-flex circuit board, including the following steps:
1. preparing a rigid printed circuit board 1, processing two rows of metal pads 2 positioned at the tail end of a circuit on the rigid printed circuit board, wherein each row of metal pads comprises a plurality of single metal pads, and pre-planting solder balls on each single metal pad;
2. preparing a flexible printed circuit board 3, processing two rows of double-layer connecting pads 4 which are positioned at the tail end of a circuit and respectively correspond to two rows of metal pads on the flexible printed circuit board, wherein the number of the monomer connecting pads contained in each layer connecting pad401 of each row of double-layer connecting pads is consistent with the number and positions of the monomer metal pads contained in each row of metal pads, processing a through hole 5 penetrating through the flexible printed circuit board in each monomer connecting pad, and communicating the two monomer connecting pads at the corresponding positions on each row of double-layer connecting pads through the through hole; the inner wall of the through hole 5 needs to be subjected to hole wall metallization treatment, namely copper plating, so that the connection reliability is improved;
3. respectively stacking the rigid printed circuit board and the flexible printed circuit board which are obtained through the pretreatment in the step 1 and the step 2 together, respectively aligning the single metal pad in each row of metal pads with the single connection pad in one layer of connection pads of each row of double-layer connection pads at the corresponding position, and pre-fixing the rigid printed circuit board and the flexible printed circuit board into a whole;
4. and (3) placing the rigid printed circuit board and the flexible printed circuit board which are pre-fixed together in the step (3) into a constant-temperature laser soldering machine for tin melting connection processing, enabling the pre-planted solder balls to flow through the through holes (5) after being melted, and fixedly connecting each single metal pad (201) with the single connection pad (401 a) at the corresponding position together to obtain the circuit board with soft and hard combination.
The single metal pad 201 here is two rows of metal pads 2 arranged at the end of the line according to the design requirement and the wiring requirement; processing the solder mask layer, namely exposing a copper foil at a set position, wherein the exposed copper foil is the monomer metal pad 201; the single connection pad401a is formed by arranging two rows of double-layer connection pads 4 at the tail end of a circuit according to design requirements and wiring requirements; processing is carried out on the solder mask layer and the substrate layer, copper foil is exposed at a set position, the exposed copper foil is a single connection pad401a, and two layers of connection pads contained in each row of double-layer connection pads 4 are respectively positioned in two surfaces of the flexible printed circuit board 3; the single connection pad401a has a circular shape in which the through hole 5 is processed, and thus, the single connection pad401a is substantially a metal ring.
After tin melting processing is carried out in a constant-temperature laser soldering machine, the pre-planted solder balls melt and flow through the through holes to form tin-copper alloy, and the tin-copper alloy stays in the through holes 5 and the connection pad401a of each monomer.
After step 1 and before step 2, further comprising step 1 a: two gold-plated positioning marks 6 are machined on the rigid printed circuit board.
After step 2 and before step 3, further comprising step 2 a: processing two positioning holes 7 corresponding to the two gold-plated positioning marks on the flexible printed circuit board respectively; when the rigid printed circuit board and the flexible printed circuit board are stacked together, the two gold-plated positioning marks 6 are respectively aligned with the two positioning holes 7.
Further comprising step 2 b: arranging a piece of double-sided adhesive tape 8 on the surface of the flexible printed circuit board, which is attached to the rigid printed circuit board; tearing off release paper on the double-sided adhesive tape, and after the rigid printed circuit board and the flexible printed circuit board are aligned through the gold-plated positioning marks and the positioning holes, adhering the rigid printed circuit board and the flexible printed circuit board together, namely, realizing the pre-fixation of the rigid printed circuit board and the flexible printed circuit board through the double-sided adhesive tape 8.
Specifically, the distance between each row of metal pads 2 and the edge of the end part of the rigid printed circuit board 1 is more than or equal to 0.3 mm; the single metal pads are circular, the diameter of each single metal pad is 0.35mm, and the distance between every two adjacent single metal pads is larger than or equal to 0.25 mm.
The solder ball pre-planting process comprises a printing process, a reflow soldering process, an SPI (serial peripheral interface) inspection process between the printing process and the reflow soldering process and an AOI (automated optical inspection) process after the reflow soldering process; the printing process adopts a solder paste printing machine for processing, a steel mesh with the thickness of 80 microns is adopted for printing, the height of the steel mesh is 0-100 microns away from a product, the angle of a scraper adopted by the solder paste printing machine is 60 +/-5 degrees, and the advancing speed of the scraper is set to be 75 +/-25 mThe steel net tension of m/s, the steel net length and width dimension of 420mmx520mm or 580mmx580mm, 420mmx520mm meets 30N/cm2～35N/cm2580mmx580mm steel net tension satisfying 35N/cm2～40N/cm2(ii) a Working environment and storage environment requirements: the temperature is 22 +/-5 ℃, and the relative humidity is 50% +/-20% RH; the reflow soldering process adopts a multi-temperature-zone reflow furnace for processing, the furnace temperature is less than or equal to 245 ℃, the advancing speed of the reflow furnace is 900 mm/min-950 mm/min, the number of temperature zones is not less than ten temperature zones, the preheating slope is 1-2 ℃/s in a 30-150 ℃ interval, the preheating time is 80-100 s in a 0-150 ℃ interval, the constant temperature time is 70-90 s in a 150-200 ℃ interval, the reflow soldering time is 50-65 s in a 220 ℃ interval, the peak temperature is 240-245 ℃, and the cooling slope is-5-1 ℃/s; the requirements of the working environment are as follows: the temperature is 22 +/-5 ℃; SPI inspection process adopts the online three-dimensional soldering paste detection machine of SPI, needs to satisfy following technical index: a. using a point laser scanning or stripe laser light trial scanning principle; b. the scanning level meets the micron level; c. besides basic thickness scanning, the indexes or bad performances such as area, volume, deviation, deformation, bridging, tin deficiency, tip pulling and the like are also required to be identified; d. equipment GR&R satisfies 10% -20% of the measured length, width and thickness tolerance; e. the inspection thickness of the substrate needs to meet 0.1 mm-5.0 mm; f. the size of the workbench is not less than 450mmx350 mm; g. the requirements of the working environment are as follows: the temperature is 22 +/-5 ℃, and the relative humidity is 50% +/-20% RH; the AOI inspection process adopts automatic optical inspection equipment AOI, and the following technical indexes are required to be met: a. detecting by using a color digital CCD visual camera and color operation, color extraction, gray scale operation and image comparison modes; b. the equipment positioning precision is less than or equal to 8 mu m; c. the moving speed is required to be more than or equal to 650 mm/s; d. the resolution of the equipment is more than or equal to 15 mu m; e. the inspection thickness of the substrate needs to meet 0.1 mm-5.0 mm; f. the size of the workbench is not less than 450mmx350 mm; g. the requirements of the working environment are as follows: the temperature is 22 ℃ plus or minus 5 ℃ and the relative humidity is 50% + orminus 20% RH.
The solder paste adopted by the pre-planted solder ball needs to meet the following technical indexes: a. lead-free solder paste; b. the average diameter of the tin powder particles is 32 mu m, and the diameter range is 25-36 mu m.
The positioning holes 7 corresponding to the gold-plated positioning marks 6 are all circular, and the diameters of the positioning holes 7 are 0.8mm and 0.9mm respectively.
The distance between each row of connecting pads and the edge of the end part of the flexible printed circuit board 3 is more than or equal to 0.2 mm; the monomer connecting pad is circular, and the diameter of the monomer connecting pad is 0.3 mm; the metallized through hole is a circular hole, which is coaxially arranged with the monomer connection pad, and the diameter of the metallized through hole is 0.13mm, so that the monomer connection pad401a is a metal circular ring with the specification of phi 0.3 x0.13mm.
The thickness of the double-sided adhesive tape is less than or equal to 50 mu m, and the initial viscosity of the double-sided adhesive tape is more than or equal to 5.2N/10 mm; the aging viscosity is more than or equal to 6.9N/10mm after 14 days; the process can be repeated twice.
The laser wavelength of the constant-temperature laser soldering machine is 915 nm; the laser power is more than or equal to 30W; the welding mode is single-point continuous welding; the temperature control mode needs to meet the requirement of constant temperature control; the single spot welding time is less than or equal to 200ms, the repeated operation precision is less than or equal to 10 mu m, and the welding residue standard is as follows: referring to IPC-610H, cooling mode: air cooling or water cooling, and the requirements of the working environment are as follows: the temperature is 22 ℃ plus or minus 5 ℃ and the relative humidity is 50% + orminus 20% RH.
After the rigid printed circuit board 1 and the flexible printed circuit board 3 are assembled together, a layer of insulating mylar is attached to the surface of the tin-copper alloy on the monomer connection pad401a in the surface, which is not attached to the rigid printed circuit board 1, of the flexible printed circuit board or UV light curing glue is applied for fixation, and the step is only used for protection and does not affect the functions of the product. It should be noted that the flexible printed circuit board 3 includes two surfaces, if the surface of the flexible printed circuit board 3 that is attached to the rigid printed circuit board 1 is defined as a surface a, the surface that is not attached to the rigid printed circuit board 1 is defined as a surface B, two layers of connection pads included in each row of the dual-layer connection pads are respectively located in the surface a and the surface B of the flexible printed circuit board 3, here, the surfaces of the single connection pads 401a in the surface a and the surface B both have tin-copper alloy, but only the surface of the single connection pad401a in the surface B needs to be attached with a layer of insulating mylar or fixed by a point UV light curing adhesive.
In summary, the rigid printed circuit board 1 and the flexible printed circuit board 3 required by the present invention both adopt the existing conventional products, no customization is needed, the appropriate rigid printed circuit board and flexible printed circuit board are selected, the conventional process is respectively adopted to process a plurality of corresponding monomer metal pads and monomer connection pads on the rigid printed circuit board and the flexible printed circuit board according to the design requirement, the solder ball is pre-planted on the surface of each monomer metal pad, the through hole is processed in each monomer connection pad, when the rigid printed circuit board and the flexible printed circuit board are assembled, the monomer metal pads are aligned with the monomer connection pads, the pre-planted solder ball on the metal pads is positioned between the metal pads and the connection pads, the assembled and pre-fixed rigid printed circuit board and flexible printed circuit board are placed in the constant temperature laser soldering machine for tin melting connection processing, the pre-planted solder ball is melted and then each monomer metal pad is fixedly connected with the monomer connection pads at the corresponding position, obtaining a soft and hard combined circuit board; compared with the prior art of the same type, the invention has simple process and less working procedures, and is beneficial to saving the processing cost; the rigid-flexible circuit board obtained by the manufacturing method has a simple structure and small overall thickness, and is beneficial to realizing the light and thin design of a terminal product applying the rigid-flexible circuit board.
In the above description, it should be noted that the terms "mounted," "connected," and the like are used in a broad sense, and for example, they may be fixedly connected, detachably connected, or integrally connected; the connection may be direct or indirect via an intermediate medium, and the connection may be internal to the two components.
It is to be understood that the above-described embodiments are merely illustrative of some, but not restrictive, of the broad invention, and that the appended drawings illustrate preferred embodiments of the invention without limiting its scope. This invention may be embodied in many different forms and, on the contrary, these embodiments are provided so that this disclosure will be thorough and complete. All equivalent structures made by using the contents of the specification and the attached drawings of the invention can be directly or indirectly applied to other related technical fields, and are also within the protection scope of the patent of the invention.
Claims (14)
1. A manufacturing method of a rigid-flexible circuit board is characterized by comprising the following steps:
(1) preparing a rigid printed circuit board, processing two rows of metal pads positioned at the tail end of a circuit on the rigid printed circuit board, wherein each row of metal pads comprises a plurality of single metal pads, and pre-planting solder balls on each single metal pad;
(2) preparing a flexible printed circuit board, processing two rows of double-layer connecting pads which are positioned at the tail end of a circuit and respectively correspond to two rows of metal pads on the flexible printed circuit board, wherein the number of the single connecting pads contained by each row of double-layer connecting pads is consistent with the number and positions of the single metal pads contained by each row of metal pads, and processing metallized through holes penetrating through the flexible printed circuit board in each single connecting pad, wherein the through holes communicate the two single connecting pads at the corresponding positions on each row of double-layer connecting pads;
(3) respectively stacking the rigid printed circuit board and the flexible printed circuit board which are obtained through the pretreatment in the step (1) and the step (2) together, respectively aligning the single metal pad in each row of metal pads with the single connection pad in one layer of connection pads of each row of double-layer connection pads at the corresponding position, and pre-fixing the rigid printed circuit board and the flexible printed circuit board into a whole;
(4) and (3) placing the rigid printed circuit board and the flexible printed circuit board which are pre-fixed together in the step (3) into a constant-temperature laser soldering machine for tin melting connection processing, wherein the pre-planted solder balls are melted and then flow through the through holes, and fixedly connecting each row of metal pads with the double-layer connection pads at the corresponding positions together to obtain the circuit board with soft and hard combination.
2. The method for manufacturing a rigid-flex circuit board according to claim 1, further comprising the step (1a) after the step (1) and before the step (2): two gold-plated positioning marks are processed on the rigid printed circuit board.
3. The method for manufacturing a rigid-flex circuit board according to claim 2, further comprising the step (2a) after the step (2) and before the step (3): processing two positioning holes respectively corresponding to the two gold-plated positioning marks on the flexible printed circuit board; when the rigid printed circuit board and the flexible printed circuit board are stacked together, the two gold-plated positioning marks are respectively aligned with the two positioning holes.
4. The method for manufacturing a rigid-flex circuit board according to claim 3, further comprising the step (2 b): arranging a piece of double-sided adhesive tape on the surface of the flexible printed circuit board, which is attached to the rigid printed circuit board; tearing off release paper on the double-sided adhesive tape, and after the rigid printed circuit board and the flexible printed circuit board are aligned through the gold-plated positioning marks and the positioning holes, adhering the rigid printed circuit board and the flexible printed circuit board together, namely, realizing the pre-fixation of the rigid printed circuit board and the flexible printed circuit board through the double-sided adhesive tape.
5. The method for manufacturing a rigid-flexible printed circuit board according to claim 4, wherein the two connection pads of each row of the two connection pads are respectively processed on two surfaces of the flexible printed circuit board.
6. The method for manufacturing a rigid-flex circuit board according to claim 4, wherein the distance between each row of metal pads and the edge of the end of the rigid printed circuit board is not less than 0.3 mm; the single metal pads are circular, the diameter of each single metal pad is 0.35mm, and the distance between every two adjacent single metal pads is larger than or equal to 0.25 mm.
7. The method of claim 4, wherein the pre-implanting of solder balls comprises a printing process and a reflow process; the printing process adopts a solder paste printing machine for processing, a steel mesh with the thickness of 80 microns is adopted for printing, the height of the steel mesh is 0-100 microns away from a product, the angle of a scraper adopted by the solder paste printing machine is 60 +/-5 degrees, and the advancing speed of the scraper is set to be 75 +/-25 mm/s; the reflow soldering process adopts a multi-temperature zone reflow furnace for processing, the furnace temperature is less than or equal to 245 ℃, and the traveling speed of the reflow furnace is 900 mm/min-950 mm/min.
8. The method of claim 4, wherein the positioning holes corresponding to the gold-plated positioning marks are circular, and the diameters of the positioning holes are 0.8mm and 0.9mm, respectively.
9. The method for manufacturing a rigid-flexible printed circuit board according to claim 6, wherein the distance between each row of connection pads and the edge of the end of the flexible printed circuit board is not less than 0.2 mm; the monomer connecting pad is circular, and the diameter of the monomer connecting pad is 0.3 mm; the through-hole is the circular port, and it is coaxial setting with monomer connection pad, and the diameter is 0.13mm after the metallization.
10. The method for manufacturing a rigid-flex circuit board according to claim 4, wherein the thickness of the double-sided adhesive tape is less than or equal to 50 μm, and the initial adhesion is greater than or equal to 5.2N/10 mm; the aging viscosity is more than or equal to 6.9N/10mm after 14 days; the process can be repeated twice.
11. The method for manufacturing a rigid-flex circuit board according to claim 4, wherein the laser wavelength of the constant temperature laser soldering machine is 915 nm; the laser power is more than or equal to 30W; the welding mode is single-point continuous welding; the temperature control mode needs to meet the requirement of constant temperature control; the single spot welding time is less than or equal to 200 ms.
12. A rigid-flex circuit board manufactured by the manufacturing method of any one of claims 1 to 10, comprising a rigid printed circuit board, a flexible printed circuit board stacked together; two rows of metal pads are arranged in one surface of the rigid printed circuit board, each row of metal pads comprises a plurality of single metal pads, and a solder ball is arranged on each single metal pad; the flexible printed circuit board is provided with two rows of double-layer connecting pads corresponding to two rows of metal pads respectively, the number of the monomer connecting pads contained by each layer of double-layer connecting pad is consistent with the number and positions of the monomer metal pads contained by each row of metal pad, a metalized through hole penetrating through the flexible printed circuit board is arranged in each monomer connecting pad, the through hole is used for communicating the two monomer connecting pads at the corresponding positions on each row of double-layer connecting pad, and the monomer metal pads in each row of metal pads are aligned with the monomer connecting pads in one layer of connecting pads of each row of double-layer connecting pad at the corresponding positions respectively; the melted solder balls connect the corresponding monomer metal pads and the monomer connecting pads together.
13. The rigid-flex circuit board of claim 12, wherein two gold-plated positioning marks are provided on the rigid printed circuit board, and two positioning holes corresponding to the two gold-plated positioning marks, respectively, are provided on the flexible printed circuit board; the two gold-plated positioning marks are respectively aligned with the two positioning holes.
14. A rigid-flex circuit board according to claim 12, wherein a double-sided tape for pre-fixing with the rigid printed circuit board is provided on one surface of the flexible printed circuit board.
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| CN202110434301.5A CN113179597A (en) | 2021-04-22 | 2021-04-22 | Rigid-flexible circuit board and manufacturing method thereof |
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| CN202110434301.5A CN113179597A (en) | 2021-04-22 | 2021-04-22 | Rigid-flexible circuit board and manufacturing method thereof |
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Application publication date: 20210727 |