CN114143976B - Wearable flexible circuit based on laser induction and preparation method thereof - Google Patents
Wearable flexible circuit based on laser induction and preparation method thereof Download PDFInfo
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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
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/105—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by conversion of non-conductive material on or in the support into conductive material, e.g. by using an energy beam
-
- 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
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/10—Using electric, magnetic and electromagnetic fields; Using laser light
- H05K2203/107—Using laser light
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing Of Printed Circuit Boards (AREA)
- Manufacturing Of Printed Wiring (AREA)
Abstract
The invention discloses a wearable flexible circuit based on laser induction and a preparation method thereof, wherein the method comprises the steps of etching a conductive layer or a protective layer by adopting laser induction: firstly, the difference of the absorption coefficients of the conducting layer and the long-chain polymer protective layer on laser is utilized, the long-chain polymer protective layer with high laser absorption coefficient covered on the surface of the conducting layer is firstly subjected to induced etching, the conducting layer of the exposed part of the conducting layer is directly generated into a circuit with the long-chain polymer protective layer after being etched by etching liquid, and the same principle can be utilized to subtract the etching liquid etching step and then quickly prepare a welding hole of the flexible circuit; secondly, the preparation process and steps of the flexible circuit are adjusted by adjusting the laser induction parameters, the thickness of the conductive layer and the materials of the long-chain polymer protective layer by utilizing the action difference of the laser on the conductive layers with different thicknesses, so that the dry preparation of the flexible circuit is realized. Compared with the traditional circuit preparation process, the invention simplifies the process flow, reduces the production cost and has the potential of large-scale application.
Description
Technical Field
The invention relates to a wearable circuit based on laser induction and a preparation method thereof, which can be used for agricultural intelligent detection, industry, medical treatment, consumer goods and the like, and belongs to the field of flexible wearable equipment.
Background
The wearable electronic products and the flexible wearable sensors are widely applied to medical monitoring products and services based on physiological signal monitoring, but most of the wearable electronic products at present only realize the flexibility of the tail end detection sensor, and the data processing platform is also based on a planar hard printed circuit board, so that the defects of large measurement result error and the like caused by the fact that the existing rigid electronic devices such as the hard printed circuit board (Printed Circuit Board, PCB) are not suitable for being worn for a long time and cannot be tightly combined with skin folds are overcome. The electronic equipment prepared by using the wearable flexible material substrate can be better attached to the skin surface of a human body to obtain higher measurement precision, meanwhile, the discomfort of wearing for a long time is reduced, the life quality of a wearer is improved, and the electronic equipment is gradually valued by scientific researchers. In order to combine the wearable electronic product and the sensor with irregular curved surfaces such as skin, scientific researchers print the circuit on the PI film, but PI only has bending characteristics and no stretching characteristics, so that the application effect is not ideal, and the application conditions of large-amplitude bending and stretching cannot be met. With advances in materials science and micro-nano fabrication technology, it has become possible to fabricate wearable flexible circuits. However, the thermal expansion coefficients of the metal and the stretchable material are very different, and the flexible circuit is directly manufactured on the surface of the wearable flexible material (such as PDMS), so that the problems of cracking or breaking of the metal wire and the like can occur, and the reliability and the practicability of the circuit are seriously affected.
A key challenge in the manufacture of wearable flexible circuit boards to date has been the preparation of solderable, low resistance, and high stretchability wires on flexible substrates for connection to electronic components. It has been proposed in the prior art to make wires from thin metal films (e.g., silver, gold, copper), dispersed solutions of conductive materials (e.g., silver, copper, carbon nanotubes, graphene, or carbon fibers), or liquid conductors (liquid metals). However, the resistivity of the dispersed conductive material and liquid conductor is high. In addition, stretchable wires made from conductive materials and liquid conductors are not compatible with existing soldering processes for PCBs. In addition to the above methods, to provide stretchability to the wires in the circuit, a metal film is used to fabricate stretchable wires with "deterministic geometry" (e.g., wavy structures, and serpentine grids) on a stretched substrate (e.g., PDMS). There are researchers depositing metal films onto substrates by vapor deposition, but this is too costly, and there are also people manufacturing seed layers and electroformed metal wires on seed layers with spray guns. Although this method is less expensive than vacuum film deposition techniques, a time consuming electroforming process is required.
Disclosure of Invention
The invention aims to: another object of the invention is to provide a high-stretchability, low-cost, laser-induced-based wearable flexible circuit; another object of the invention is to provide a method of manufacturing a wearable flexible circuit based on laser induction.
The technical scheme is as follows: the wearable flexible circuit based on laser induction comprises a flexible substrate, a conductive layer and a long-chain polymer protective layer which are sequentially covered on the flexible substrate, a wire area and a bonding pad area which are prepared based on laser induction and other processes, and an electronic component and a packaging layer which are welded in the bonding pad area.
Further, the wires of the wire area are serpentine, zigzag or S-shaped.
In another aspect, the method for manufacturing a wearable flexible circuit based on laser induction of the present invention comprises the steps of:
(1) Fixing a flexible substrate on a substrate, and sequentially modifying a conductive layer and a long-chain polymer protective layer on the surface of the flexible substrate;
(2) Etching the long-chain polymer protective layer by using laser according to a preset circuit diagram, and exposing the conducting layer of the non-conducting wire and the non-bonding pad area after cleaning etching residues;
laser induced etching: leading a pre-designed circuit diagram into a laser direct writing instrument, and etching and removing the protective materials on the surfaces of non-conducting wires and non-bonding pad parts in the circuit on the material surface of the long-chain polymer protective layer by laser etching to expose the conductive layer in the region; wherein the thickness range of the conductive layer in the step (1) is 80-120 μm, the conductive layer under the thickness range cannot be etched by set laser, and the set laser can only etch the long-chain polymer protective layer.
Cleaning etching residues: and cleaning the laser etching area, and removing carbonized residues generated by laser etching to thoroughly expose the conductive layer.
(3) Etching: and etching the exposed conductive layer through etching liquid to obtain the wire with the circuit supporting layer.
(4) Preparing welding holes: and (3) introducing a pre-designed welding hole pattern into a laser direct writing instrument, performing laser etching to remove the long-chain polymer protective layer in the preset bonding pad area on the surface of the flexible device, exposing the conductive layer, and cleaning etching residues to form the welding hole with the welding resistance film.
(5) Welding electronic components and external power lines on the bonding pad area;
(6) Packaging, solidifying and stripping to obtain the final product;
and (3) packaging: and packaging the welded flexible circuit, and curing the packaging layer.
Stripping: and stripping the prepared circuit board from the substrate to finally finish the preparation of the wearable flexible circuit board.
Further, in the step (1), the flexible substrate is polydimethylsiloxane, ecoflex or polyurethane; preferably, the flexible substrate is PDMS; the thickness of the flexible substrate ranges from 2 mu m to 200 mu m; the substrate is a glass sheet, a ceramic sheet or a silicon sheet; preferably, the hard substrate is a glass sheet;
further, in the step (1), the modification of the conductive layer may be performed in any of the following manners: (1) modifying the conductive layer on the surface of the flexible substrate by sticking a metal foil; (2) modifying the conductive layer by evaporating a metal film on the flexible substrate; (3) the conductive layer is decorated on the flexible substrate by means of doctor blade coating, spin coating, screen printing or ink jet printing of conductive ink.
Further, the metal foil in the mode (1) can be copper, gold or silver foil, the thickness range is 80 μm-120 μm, and the substrate and the metal foil are fixed by bisphenol A type epoxy resin glue or metal foil glue; the vapor plating metal in the mode (2) is copper, gold or silver, and the thickness range of the plating layer is 80-120 mu m; the conductive ink in the mode (3) is metal-based ink such as silver nanowires.
Further, in the step (1), the long-chain polymer protective layer is polyimide, polymethyl methacrylate or polyethylene; preferably, the long-chain polymer protective layer is polyimide.
Further, in the step (1), the method for modifying the long-chain polymer protective layer is any one of the following modes: (1) sticking a long-chain high-molecular polymer protective film with high laser absorptivity on the surface of the flexible substrate; (2) the prepolymer of the long-chain high-molecular polymer with high laser absorptivity is decorated on the flexible substrate by means of knife coating, spin coating, screen printing or ink-jet printing.
Further, in the step (2), the laser direct writing power range of laser etching is 4W-20W, and the direct writing speed is 0.5 cm/s-3 cm/s; the laser type of the laser direct writing instrument is carbon dioxide laser, excimer laser or YAG laser; the thickness of the protective layer ranges from 80 mu m to 120 mu m; the line width of the circuit and the bonding pad is 500-4000 μm; the conductor pattern is serpentine, zigzag or S-shaped.
Further, in the step (2), cleaning the etched residual substances by using a cleaning solution, wherein the cleaning solution is diethylene glycol monoethyl ether acetate, absolute ethyl alcohol or acetone; in the step (5), the ratio of the etchant for preparing the etching liquid to water is 4:1, etching for 5-10 min at 40-50 ℃.
Further, in the step (5), the chip is welded to the bonding pad through a PCB (printed circuit board) surface mounting process, or the chip is fixed on the bonding pad by using conductive adhesive; the external power line can be welded by using a common electronic component welding process.
Further, in the step (6), packaging is performed by using PDMS or silica gel; the thickness of the encapsulation layer is 50-500 mu m.
On the other hand, the process and sequence of the steps (1) to (6) can be adjusted by adjusting the laser induction parameters, the thickness of the conductive layer and the material of the long-chain polymer protective layer, and the adjusted preparation method of the wearable flexible circuit comprises the following steps:
(1) Fixing a flexible base on a substrate, and only modifying a conductive layer on the surface of the flexible base;
(2) According to a preset circuit diagram, etching the conductive layer by laser to obtain a flexible substrate with a wire area and a bonding pad area;
(3) Coating long-chain polymer prepolymer on the surfaces of the lead and the bonding pad area by using a mask plate mode, and forming a circuit supporting layer and a solder resist after curing;
(4) Welding electronic components and external power lines on the bonding pad area;
(5) Packaging, solidifying and stripping to obtain the final product.
Compared with the conductive layer with the thickness of 80-120 mu m in the first method for preparing the wearable flexible circuit, in the step (2), the thickness of the conductive layer is adjusted to be 80-120 nm, the thickness of the conductive layer is extremely thin, and the set laser can etch the conductive layer; in order to obtain the flexible substrate with the wire area and the bonding pad area, the thickness of the conductive layer can be maintained to be 80-120 μm without adjusting the thickness of the conductive layer, and laser parameters are adjusted to enable the conductive layer to be etched successfully.
The invention adopts a laser induction technology to obtain two methods for preparing the wearable flexible circuit: firstly, the difference of the absorption coefficients of the conducting layer and the long-chain polymer protective layer on laser is utilized, the long-chain polymer protective layer with high laser absorption coefficient on the surface of the conducting layer is firstly subjected to induced etching, the conducting layer of the exposed part of the conducting layer is etched by etching liquid, then a circuit with the long-chain polymer protective layer is directly generated, and the same principle can be utilized, and the welding holes of the flexible circuit are rapidly prepared after the etching step of the etching liquid is subtracted; secondly, the preparation process and steps of the flexible circuit are adjusted by adjusting the laser induction parameters, the thickness of the conductive layer and the materials of the long-chain polymer protective layer by utilizing the difference of the action effect of the laser on the conductive layers with different thicknesses, so that the dry preparation of the flexible circuit is realized.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages: (1) The preparation process is simplified, and compared with the preparation modes such as electroplating, seed layer spraying and the like, the method improves the preparation precision of the circuit and the preparation efficiency of the flexible circuit;
(2) The circuit reliability is high, the long-chain high-molecular polymer protective film with high laser absorptivity is etched on the surface of the conductive layer by adopting laser induction, the conductive layer is exposed, the welding holes are quickly prepared, the complicated process of manufacturing the traditional flexible circuit bonding pad is avoided, the reliability is improved while the manufacturing cost is reduced, and the potential of large-scale preparation is possessed.
(3) The metal circuit has certain stretchability, is designed into a serpentine shape, a zigzag shape or an S shape, and is coated with a liquid PI prepolymer on the surface of the metal circuit to be solidified so as to support and protect the metal circuit;
(4) The wearable flexible substrate is high in wearability, and the wearable flexible substrate is made of biocompatible materials such as Polydimethylsiloxane (PDMS), so that the integrated wearable device is comfortable to wear, and anaphylactic reaction caused by wearing is not easy to occur.
Drawings
FIG. 1 is a flow chart of the preparation process of the invention;
FIG. 2 is a schematic diagram of a laser-induced etching generation circuit of the present invention;
FIG. 3 is a view of a laser-induced fabrication of solder apertures in accordance with the present invention;
fig. 4 is a flow chart of the preparation process of example 5.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
1. A substrate; 2. a flexible substrate; 3. a conductive layer; 4. a long-chain polymer protective layer; 5. a pad region; 6. a wire region; 7. externally connecting a power line; 8. an electronic component; 9. tin; 10. an encapsulation layer; 11. a laser beam; 12. and (5) a laser instrument.
Example 1
As shown in fig. 1, the wearable flexible circuit based on laser induction comprises a flexible substrate 2, a conductive layer 3, a long-chain polymer protective layer 4, a bonding pad area 5, a wire area 6, an external power line 7, an electronic component 8 and a packaging layer 10, wherein the conductive layer 3 and the long-chain polymer protective layer 4 are sequentially covered on the flexible substrate 2, the wire area formed after the long-chain polymer protective layer 4 and the exposed conductive layer 3 are respectively etched by laser induction and etching liquid and the bonding pad area 5 based on laser induction are formed, the electronic component 8 and the external power line 7 are welded in the bonding pad area 5, and the packaging layer 10 is covered on the outermost layer of the wearable flexible circuit; the long-chain polymer protective layer covers the welding pad area 5, namely the welding resistance film of the welding hole, and the long-chain polymer protective layer covers the wire area, namely the wire support layer of the wire.
Specifically, the full-view boundary of the wearable flex circuit: 50mm x 65mm; the flexible substrate 2 is Polydimethylsiloxane (PDMS) with the thickness of 500 mu m, the conductive layer 3 is copper with the thickness of 100 mu m; the wire area 6 is a serpentine wire, and has the width: 0.8mm, inner ring radius: 0.16mm, outer ring radius: 0.96mm and amplitude 2mm; pad area 5:1.5mm x 2mm; external pin in external power cord 7: 2mm x 2mm; the long-chain polymer protective layer 4 is Polyimide (PI) with the thickness of 100 mu m; the encapsulation layer 9 is made of PDMS and has a thickness of 100 μm.
Optionally, the flexible substrate may be Ecoflex or polyurethane; the conductive layer 3 is a metal foil, which can be copper, gold or silver foil, and has a thickness ranging from 80 mu m to 120 mu m; the long-chain polymer protective layer can be made of Polyimide (PI), polymethyl methacrylate (PMMA) or Polyethylene (PE) long-chain polymer materials; the thickness range of the wire area and the bonding pad area is 80-120 mu m; the line width of the circuit and the bonding pad is 500-4000 μm; the wire pattern is serpentine, zigzag or S-shaped; the material of the packaging layer is PDMS or other flexible materials such as silica gel, and the thickness of the packaging layer is 50-500 mu m.
Example 2
As shown in fig. 1, the preparation method of the wearable flexible circuit based on laser induction comprises the following main steps:
1. modified conductive layer and long-chain polymer protective layer on flexible substrate
(1) Preparing a substrate 1 and a flexible substrate 2 with a required size, coating a layer of glue on the substrate 1, peeling off a protective film of the flexible substrate 2, attaching the protective film on a glass plate, and compacting; the protective film on the other side of the flexible substrate 2 is uncovered, bisphenol A epoxy resin glue formed by mixing bisphenol A epoxy resin and a curing agent 5:1 is uniformly coated on the flexible substrate 2, a prepared conductive layer 3 is attached to the flexible substrate 2PDMS on a glass plate, and after the conductive layer 3 is flattened, a flat article is used for pressing until the glue is cured; wherein the substrate 1 is a glass substrate, the flexible substrate 2 is a PDMS flexible substrate, and the conductive layer 3 is copper foil.
Optionally, modifying the conductive layer by evaporating a metal film on the flexible substrate; or modifying the conductive layer on the flexible substrate by means of doctor-blading, spin-coating, screen printing or ink-jet printing conductive ink and the like, wherein the conductive ink is metal-based ink such as silver nanowires and the like.
(2) And (3) sticking the long-chain polymer protective layer 4 on the surface of the copper foil and flattening, wherein the long-chain polymer protective layer 4 is a glued PI film.
Optionally, the protective film is modified by sticking a long-chain high-molecular polymer protective film with high laser absorptivity on the surface of the conductive layer; or the prepolymer of the long-chain high-molecular polymer with high laser absorptivity is modified on the conductive layer by means of knife coating, spin coating, screen printing or ink-jet printing, etc. to form the protective film.
2. Laser induced etching and cleaning residues
(1) Laser induced etching: leading a pre-designed circuit diagram into a laser direct writing instrument, and etching and removing the protective materials on the surfaces of non-conducting wires and non-bonding pad parts in the circuit through laser on the material surface of the long-chain polymer protective layer to expose the conductive layer in the area;
the laser wavelength used was 450nm, the laser power was 5.5W, and the write-through speed was 2cm/s. Under the laser parameters, the laser carbonizes the PI protecting film of the non-circuit and bonding pad part to separate from the copper foil, and the remaining part PI is used as a long-chain polymer protecting layer. In the laser-induced etching process, if the PI long-chain polymer protective layer is not completely carbonized and falls off after one-time etching, the etching steps can be repeated by using the same etching parameters until the PI protective film and the adhesive layer of the non-circuit and bonding pad parts are completely carbonized.
(2) Cleaning residues: after immersing the copper foil in the laser etched area for 40 seconds by using diethylene glycol monoethyl ether acetate, wiping the PI and glue carbide on the surface of the copper foil with a cotton swab, and thoroughly exposing the copper foil in the area.
3. Etching the exposed conductive layer by etching liquid
Placing the device into etching liquid, and etching and removing the exposed non-conducting wire and the conducting layer of the non-bonding pad part in the circuit; the etchant is mixed with water in a ratio of 4:1 to prepare etching liquid, and the device is placed into the etching liquid to be etched for about 6 minutes at 50 ℃.
4. Preparation of solder holes and pads
(1) Preparing welding holes: leading a pre-designed welding hole graph into a laser direct writing instrument, and removing the PI-removed protective film of the preset welding pad area on the surface of the flexible device through laser etching to expose the conductive layer; and repeating the step 3 for cleaning, and then manufacturing a welding hole with a welding resistance film in the welding pad area 5.
(2) Welding electronic components and manufacturing an external power line welding disk: soldering the desired electronic components 8 to the pad areas 5 of the wearable flexible circuit board using a PCB patch process; when the conductive adhesive is used for connecting the electronic components and the circuit, a proper amount of the conductive adhesive is taken after the conductive adhesive is thawed and coated on a metal part which needs to be connected with the electronic components, the electronic components are fixed at the position coated with the conductive adhesive, and the electronic components are put into a drying box and dried for 60 minutes at 80 ℃.
When the bonding pad of the external power line is manufactured, the tin soldering paste is coated on the metal of the external bonding pad part, the tin soldering paste is heated to melt, and the external power line bonding pad with tin 9 is formed after the tin is cooled and solidified.
5. PDMS flexible packaging layer packaging
(1) And (3) packaging: after the electronic component is welded, the PDMS prepolymer is prepared by mixing SYLGARDTM184 Silicone Elastomer Base and SYLGARDTM184 Silicone Elastomer Cring Agent in a ratio of 10:1, and is spin-coated on the surface of the electronic component, wherein the spin-coating thickness is 100 mu m, and the rotating speed is 1500r/min for 180 seconds. The spin-coated samples were placed in a vacuum oven, evacuated to no bubbles in the liquid PDMS, and then cured at 60 ℃ for 2 hours to make the encapsulation layer 10.
(2) Stripping: and stripping the prepared wearable flexible circuit from the substrate 1 to finish the preparation of the wearable flexible circuit.
Example 3
The steps of the laser induced etching generating circuit are as follows:
as shown in fig. 2, in fig. 2 (1), PI with a higher laser absorption coefficient is carbonized and falls off after laser induced etching, and then is cleaned by diethylene glycol monoethyl ether acetate, so that copper foil of a non-wire and a bonding pad part is completely exposed, as shown in fig. 2 (2), finally, the flexible device obtained after cleaning is put into etching liquid, and is etched for 10 minutes at 50 ℃ to obtain the flexible circuit with the circuit supporting layer shown in fig. 2 (3).
Optionally, the cleaning solution is diethylene glycol monoethyl ether acetate, absolute ethyl alcohol or acetone, and the etching solution is etched for 5-10 min at 40-50 ℃.
Example 4
The laser-induced preparation of the welded hole comprises the following steps:
as shown in fig. 3, the flexible circuit obtained after etching by the etching solution is cleaned by clean water and then placed into a laser direct writing instrument, a preset welding hole pattern is led into the laser direct writing instrument, the laser power is set to be 5.5W, and the direct writing speed is set to be 2cm/s. Under the laser parameters, the laser carbonizes the PI protective film of the preset part to separate from the copper foil, and then the copper foil is exposed out of the welding hole area after the PI protective film is cleaned by diethylene glycol monoethyl ether acetate, so that the preparation of the welding hole with the solder mask is completed.
Optionally, the laser direct writing power range of laser etching is 4W-20W, and the direct writing speed is 0.5 cm/s-3 cm/s; the laser type of the laser direct writing instrument is carbon dioxide laser, excimer laser or YAG laser.
Example 5
As shown in fig. 4, the wearable flexible circuit based on laser induction of the invention comprises a flexible substrate 2, a conductive layer 3, a long-chain polymer protective layer 4, a bonding pad region 5, a wire region 6, an external power wire 7, an electronic component 8 and a packaging layer 10, wherein the conductive layer 3 is covered on the flexible substrate 2, the bonding pad region 5 and the wire region 6 which are not etched and are formed after the long-chain polymer conductive layer 3 is etched by laser induction are covered on the bonding pad region 5 and the wire region 6, the long-chain polymer protective layer 4 is covered on the bonding pad region 5, namely a solder mask of a solder hole, and the long-chain polymer protective layer is covered on the wire region, namely a wire supporting layer of a wire; the electronic components 8 and the external power line 7 are welded in the bonding pad area 5, and the packaging layer 10 covers the outermost layer of the wearable flexible circuit;
the related parameters of the wearable flexible circuit are as follows: the flexible substrate 2 is PDMS, the thickness of the flexible substrate is 500 mu m, the material of the conductive layer 3 is copper, and the thickness of the conductive layer is 80nm; the wire of the wire area is a serpentine wire, and the width is as follows: 0.5mm, inner ring radius: 0.26mm, outer ring radius: 0.76mm and amplitude 2mm; pad area 5:1.5mm x 2mm; external pin of external power line 7: 2mm x 2mm; finishing boundary: 60mm; the long-chain polymer protective layer 4 is PI with the thickness of 100 mu m; the encapsulation layer 9 is made of PDMS and has a thickness of 100 μm.
The steps for preparing the flexible wearable circuit by dry method after adjusting parameters are as follows:
1. modifying a conductive layer on a surface of a flexible substrate
Fixing a flexible substrate PDMS on a glass substrate, uniformly coating bisphenol A type epoxy resin glue on the PDMS, uncovering paper on the prepared copper foil, exposing the conductive layer 3 and flattening, pressing the substrate 1 with the PDMS on the conductive layer 3, and pressing with a flattening object until the glue is solidified.
2. Preparing a wire region and a pad region
In the experiment, the laser wavelength used was 450nm, the laser power was 5.5W, and the write-through speed was 2cm/s. Under the laser parameters, the laser vaporizes the conductive layer 3 off of the non-circuit and pad portions off of the flexible substrate 2, with the remainder of the copper acting as the circuit and pad.
3. Preparation of long-chain Polymer protective layer
Mixing PI stock solution and NMP according to a ratio of 1:1, stirring uniformly to prepare a liquid PI prepolymer, uniformly coating the liquid PI prepolymer on the solder resist area of a bonding pad and the surface of a metal wire through a mask plate, coating the liquid PI prepolymer with a thickness of 100 mu m, and then placing the circuit board into a drying box and drying for 60 minutes at a temperature of 60 ℃.
Washing and oxidation: the sample subjected to the above steps was immersed in a 10% citric acid solution for 3 minutes.
4. Welding electronic components and external power lines in the bonding pad area: the same as in step 4 of example 2.
5. Packaging and stripping: the same as in step 5 of example 2.
In the step 2, the laser is used for gasifying the copper foil with the thickness of 80nm-120nm to separate from the flexible substrate under the parameters that the direct write power range of the laser is 4W-20W and the direct write speed is 0.5 cm/s-3 cm/s.
Claims (8)
1. The wearable flexible circuit based on laser induction is characterized by comprising a flexible substrate, a conductive layer and a long-chain polymer protective layer which are sequentially covered on the flexible substrate, a wire area and a bonding pad area which are prepared based on laser induction, and an electronic component and a packaging layer which are welded in the bonding pad area;
the preparation method of the wearable flexible circuit based on laser induction comprises the following steps:
(1) Fixing a flexible substrate on a substrate, and sequentially modifying a conductive layer and a long-chain polymer protective layer on the surface of the flexible substrate, wherein the long-chain polymer protective layer is polyimide, polymethyl methacrylate or polyethylene;
(2) According to a preset circuit diagram, etching a long-chain polymer protective layer by using laser, cleaning etching residues, exposing a non-conducting wire area and a conducting layer of a non-bonding pad area, wherein the laser direct writing power range of laser etching is 4W-20W, and the direct writing speed is 0.5 cm/s-3 cm/s;
(3) Etching the exposed conductive layer through etching liquid, wherein the long-chain polymer protective layer covers the wire area to obtain a wire supporting layer of the wire, and the wire supporting layer is obtained;
(4) Etching a preset part of long-chain polymer protective layer in the bonding pad area by using laser according to a preset bonding hole diagram to expose a conductive layer in the bonding pad area, wherein the long-chain polymer protective layer covers the bonding pad area to obtain a bonding pad film of the bonding pad, and cleaning to obtain the bonding pad with the bonding pad film;
(5) Welding electronic components and external power lines on the bonding pad area;
(6) Packaging, solidifying and stripping to obtain the final product.
2. The wearable flexible circuit of claim 1, wherein the conductors of the conductor area are serpentine, zigzag, or S-shaped.
3. The preparation method of the wearable flexible circuit is characterized by comprising the following steps of:
(1) Fixing a flexible substrate on a substrate, and sequentially modifying a conductive layer and a long-chain polymer protective layer on the surface of the flexible substrate, wherein the long-chain polymer protective layer is polyimide, polymethyl methacrylate or polyethylene;
(2) According to a preset circuit diagram, etching a long-chain polymer protective layer by using laser, cleaning etching residues, exposing a non-conducting wire area and a conducting layer of a non-bonding pad area, wherein the laser direct writing power range of laser etching is 4W-20W, and the direct writing speed is 0.5 cm/s-3 cm/s;
(3) Etching the exposed conductive layer through etching liquid, wherein the long-chain polymer protective layer covers the wire area to obtain a wire supporting layer of the wire, and the wire supporting layer is obtained;
(4) Etching a preset part of long-chain polymer protective layer in the bonding pad area by using laser according to a preset bonding hole diagram to expose a conductive layer in the bonding pad area, wherein the long-chain polymer protective layer covers the bonding pad area to obtain a bonding pad film of the bonding pad, and cleaning to obtain the bonding pad with the bonding pad film;
(5) Welding electronic components and external power lines on the bonding pad area;
(6) Packaging, solidifying and stripping to obtain the final product.
4. The method of claim 3, wherein in step (1), the flexible substrate is polydimethylsiloxane, ecoflex, or polyurethane; the substrate is a glass sheet, a ceramic sheet or a silicon sheet.
5. A method of manufacturing a wearable flexible circuit according to claim 3, wherein in step (1), the method of modifying the conductive layer is any one of pasting a metal foil, metal vapor deposition, doctor blading, spin coating, screen printing or ink jet printing conductive ink.
6. The method for manufacturing a wearable flexible circuit according to claim 3, wherein in the step (1), the method for modifying the long-chain polymer protective layer is any one of a method for pasting a long-chain polymer film with glue, a method for doctor blade coating, spin coating, screen printing or ink jet printing of a long-chain polymer prepolymer.
7. The method of claim 3, wherein in the step (2), the etched residual material is cleaned by a cleaning solution, and the cleaning solution is diethylene glycol monoethyl ether acetate, absolute ethyl alcohol or acetone.
8. A method of manufacturing a wearable flexible circuit according to claim 3, wherein in step (5), the chip is soldered to the pad by a PCB die bonding process or the chip is fixed to the pad using a conductive adhesive.
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