Stretchable rigid-flex interconnection member and manufacturing method therefor

Abstract

Disclosed in the present invention are a stretchable rigid-flex interconnection member and a manufacturing method therefor. The method comprises: providing a stretchable substrate, and printing silver paste and a liquid metal composite material respectively on a first side of the stretchable substrate to form a non-stretchable circuit layer and a stretchable circuit layer, respectively, to obtain a first rigid-flex composite structure, wherein an overlapping area exists at a junction of the non-stretchable circuit layer and the stretchable circuit layer; providing a sealant, and using the sealant to encapsulate the first rigid-flex composite structure to form a sealing layer, such that the stretchable circuit layer is covered by the sealing layer to obtain a second rigid-flex composite structure; and providing a support layer, and attaching the support layer to a second side of the second rigid-flex composite structure to obtain a target rigid-flex interconnection member. In the present invention, the rigid-flex interconnection member for electronic interconnection between a rigid circuit system and a flexible circuit system can be truly formed, and the entire rigid-flex interconnection member has excellent stretchable performances, and can meet the requirements of rigid-flex interconnection electronic products such as wearable electronic devices at the current stage.

Description

Stretchable rigid-flexible interconnect and manufacturing method thereof Technical Field

[0001] The present invention relates to the technical field of rigid-flexible interconnection, and in particular to a stretchable rigid-flexible interconnection component and a manufacturing method thereof. Background Art

[0002] Rigid-flex interconnects refer to electronic systems that incorporate both rigid and flexible circuit systems, with electrical interconnection required between them. Rigid circuit systems typically refer to rigid, non-stretchable circuit modules, while flexible circuit systems typically refer to soft, stretchable circuit modules. With the advancement of technology, rigid-flex interconnects have found widespread application in fields such as medicine, military, and robotics. In particular, in the field of wearable electronics, interconnection between soft and stretchable circuit modules (i.e., flexible circuit systems) and rigid and non-stretchable circuit modules (i.e., rigid circuit systems) is almost inevitable.

[0003] Currently, most rigid-flex interconnects employ a method of designing serpentine circuits within the flexible circuit system to reduce tensile stress, thereby achieving stretchable rigid-flex interconnects. However, in these rigid-flex interconnects, only the serpentine circuits within the flexible circuit system are stretchable, and their stretchability is limited. The flexible circuit system substrate itself can only bend, not stretch. As a result, the entire rigid-flex interconnect has poor stretchability and cannot meet the requirements of current rigid-flex electronic products such as wearable electronic devices. Technical issues

[0004] The present invention provides a stretchable rigid-flexible interconnect and a manufacturing method thereof, so as to solve the problem that only the internal circuits of the existing rigid-flexible interconnect are stretchable while the substrate itself is not stretchable, thereby resulting in poor stretchability. Technical Solutions

[0005] The present invention provides a method for manufacturing a stretchable rigid-flexible interconnect, comprising:

[0006] Providing a stretchable substrate, and printing silver paste and a liquid metal composite material on a first side of the stretchable substrate to form a non-stretchable circuit layer and a stretchable circuit layer, respectively, to obtain a first rigid-flexible composite structure; wherein the non-stretchable circuit layer and the stretchable circuit layer have an overlapping area at their junction;

[0007] Providing a sealant, and encapsulating the first rigid-flexible composite structure with the sealant to form a sealing layer, so that the stretchable circuit layer is covered by the sealing layer, thereby obtaining a second rigid-flexible composite structure;

[0008] A support layer is provided, and the support layer is attached to the second side of the second rigid-flexible composite structure to obtain a target rigid-flexible interconnect.

[0009] Optionally, the liquid metal composite material is made of silver powder, liquid metal and styrene-ethylene-butylene-styrene block copolymer.

[0010] Optionally, the weight percentages of the silver powder, the liquid metal and the styrene-ethylene-butylene-styrene block copolymer in the liquid metal composite material are 28.2%, 68.3% and 3.4% respectively.

[0011] Optionally, the liquid metal is a gallium-indium alloy, and the weight ratio of gallium to indium in the gallium-indium alloy is 3:1.

[0012] Optionally, a length of the overlapping area between the non-stretchable circuit layer and the stretchable circuit layer along the stretching direction of the stretchable circuit layer is greater than or equal to 0.1 mm.

[0013] Optionally, the stretchable substrate is composed of a polymer film layer and a hot-melt adhesive layer;

[0014] Wherein, the thickness of the polymer film layer is 75 μm, and / or the thickness of the hot-melt adhesive layer is 25 μm.

[0015] Optionally, the polymer film layer includes any one of an organic silicon film layer, an acrylic polymer film layer and a polyurethane film layer.

[0016] Optionally, silver paste and liquid metal composite material are printed on the first side of the stretchable substrate to form a non-stretchable circuit layer and a stretchable circuit layer, respectively, to obtain a first rigid-flexible composite structure, comprising:

[0017] Providing the silver paste, and printing the silver paste on the side of the stretchable substrate having the polymer film layer;

[0018] curing the stretchable substrate printed with the silver paste according to a first preset curing parameter to form the non-stretchable circuit layer;

[0019] Providing the liquid metal composite material, and printing the liquid metal composite material on the side of the stretchable substrate having the polymer film layer;

[0020] The stretchable substrate printed with the liquid metal composite material is dried according to preset drying parameters to form the stretchable circuit layer that is in electrical conduction with the non-stretchable circuit layer, thereby obtaining the first rigid-flexible composite structure.

[0021] Optionally, the first preset curing parameters include a first curing time and a first curing temperature; and / or the preset drying parameters include a drying time and a drying temperature.

[0022] Optionally, the first curing time is 30 minutes; and / or the first curing temperature is 80°C; the drying time is 60 minutes; and / or the drying temperature is 60°C.

[0023] Optionally, laminating the support layer to the second side of the second rigid-flexible composite structure includes:

[0024] Bonding the support layer to the side of the second rigid-flexible composite structure having the hot-melt adhesive layer;

[0025] The second rigid-flexible composite structure bonded with the support layer is thermally laminated according to preset lamination parameters.

[0026] Optionally, the preset lamination parameters include lamination temperature, lamination time and lamination pressure;

[0027] Wherein, the lamination temperature ranges from 100 to 120° C.; and / or the lamination time ranges from 10 to 30 seconds; and / or the lamination pressure ranges from 4 to 7 Bar.

[0028] Optionally, the first rigid-flexible composite structure is encapsulated with the sealant to form a sealing layer, so that the stretchable circuit layer is covered by the sealing layer, to obtain a second rigid-flexible composite structure, comprising:

[0029] Printing the sealant onto the side of the first rigid-flexible composite structure having the stretchable circuit layer;

[0030] The first rigid-flexible composite structure printed with the sealant is cured according to second preset curing parameters to form the sealing layer on the first rigid-flexible composite structure, so that the stretchable circuit layer is completely covered by the sealing layer to obtain the second rigid-flexible composite structure.

[0031] Optionally, the second preset curing parameters include a second curing time and a second curing temperature;

[0032] Wherein, the second curing time is 2 hours; and / or the second curing temperature is 80°C.

[0033] Optionally, the thickness of the non-stretchable circuit layer ranges from 1 to 100 μm; and / or the thickness of the stretchable circuit layer ranges from 1 to 300 μm.

[0034] Optionally, the thickness of the sealing layer ranges from 0.1 to 2 mm.

[0035] Optionally, the sealing layer includes any one of an organic silicon film layer, an acrylic polymer film layer and a polyurethane film layer, or a film layer formed by any combination of several of them.

[0036] Optionally, a projection of the supporting layer on the stretchable substrate covers a projection of the non-stretchable circuit layer on the stretchable substrate.

[0037] Optionally, after laminating the support layer to the second side of the second rigid-flexible composite structure, the method further includes:

[0038] Mounting electronic components on the non-stretchable circuit layer in the second rigid-flexible composite structure on which the support layer is attached, so that electrical conduction is established between the electronic components and the non-stretchable circuit layer;

[0039] The second rigid-flexible composite structure after the electronic component is mounted is cured according to a third preset curing parameter.

[0040] Optionally, the third preset curing parameter includes a third curing time and a third curing temperature;

[0041] Wherein, the third curing time is 30 minutes; and / or the third curing temperature is 120°C.

[0042] In addition, the present invention also provides a stretchable rigid-flexible interconnect, which is manufactured using the aforementioned method for manufacturing a stretchable rigid-flexible interconnect. Beneficial effects

[0043] The beneficial effects of the present invention are as follows: silver paste is conductive and can be made flexible but not stretchable. Therefore, by printing silver paste on the first side of the stretchable substrate, a non-stretchable circuit layer can be formed, which facilitates the subsequent combination of the stretchable substrate and the support layer to form a non-stretchable rigid circuit system; the liquid metal composite material not only has the characteristics of liquid metal material, that is, it is soft and stretchable, but also overcomes the disadvantages of liquid metal material, that is, it can avoid the rapid formation of an oxide layer and hinder the wetting of the substrate. Therefore, by printing the liquid metal composite material on the first side of the stretchable substrate, a high-quality stretchable circuit layer can be easily made. Combined with the stretchability of the stretchable substrate, a flexible circuit system can be formed, and it is ensured that the entire flexible circuit system formed has excellent stretchability, not just the internal circuit is stretchable; wherein, the sealing layer formed by the encapsulation of the sealant can cover the stretchable circuit layer, which can prevent leakage or outflow of the liquid metal composite material, and play a sealing and protective role for the stretchable circuit layer; the support layer is attached to the second side of the second rigid-flexible composite structure, and can play a supporting role for the non-stretchable circuit layer;

[0044] The stretchable rigid-flexible interconnect and its manufacturing method of the present invention are based on the presence of a stretchable circuit layer and a non-stretchable circuit layer in an overlapping area at the junction, and can truly form a rigid-flexible interconnect for electronic interconnection between a rigid circuit system and a flexible circuit system. The entire rigid-flexible interconnect not only ensures functionality but also has excellent stretchability, which can meet the requirements of rigid-flexible interconnect electronic products such as wearable electronic devices at this stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0046] FIG1 shows a flow chart of a method for manufacturing a stretchable rigid-flexible interconnect in a first embodiment of the present invention;

[0047] FIG2 shows a top view of a structure in which a non-stretchable circuit layer is formed on a stretchable substrate in accordance with a first embodiment of the present invention;

[0048] FIG3 shows a top view of the first rigid-flexible composite structure obtained in Example 1 of the present invention;

[0049] FIG4 shows a cross-sectional structural diagram of the right half of the first rigid-flexible composite structure in Example 1 of the present invention;

[0050] FIG5 shows a cross-sectional structural diagram of the right half of the second rigid-flexible composite structure in Example 1 of the present invention;

[0051] FIG6 shows a top view of the second rigid-flexible composite structure in the first embodiment of the present invention;

[0052] FIG7 shows a model diagram of the changes of liquid metal before and after hot lamination in Example 1 of the present invention;

[0053] FIG8 shows a top view of the second rigid-flexible composite structure after the support layer is attached in Example 1 of the present invention;

[0054] FIG9 shows a cross-sectional structural diagram of the right half of the second rigid-flexible composite structure after the support layer is attached in Example 1 of the present invention;

[0055] FIG10 shows a cross-sectional structural diagram of a first specific implementation manner of a support layer in Example 1 of the present invention;

[0056] FIG11 shows a cross-sectional structural diagram of a second specific implementation manner of the support layer in Example 1 of the present invention;

[0057] FIG12 shows a top view of the target rigid-flexible interconnect obtained in Example 1 of the present invention;

[0058] FIG13 shows a tensile test curve of the sample produced in Example 1 of the present invention. Modes for Carrying Out the Invention

[0059] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0060] In the description of the present invention, it should be noted that the terms "upper" and "lower" etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0061] It should be noted that, in the present invention, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. Example 1

[0062] This embodiment provides a method for manufacturing a stretchable rigid-flexible interconnect, as shown in FIG1 , comprising:

[0063] S1: Providing a stretchable substrate, and printing a silver paste and a liquid metal composite material on a first side of the stretchable substrate to form a non-stretchable circuit layer and a stretchable circuit layer, respectively, to obtain a first rigid-flexible composite structure; wherein the non-stretchable circuit layer and the stretchable circuit layer have an overlapping area at their junction;

[0064] S2: providing a sealant, and encapsulating the first rigid-flexible composite structure with the sealant to form a sealing layer, so that the stretchable circuit layer is covered by the sealing layer, thereby obtaining a second rigid-flexible composite structure;

[0065] S3: providing a support layer, and laminating the support layer on the second side of the second rigid-flexible composite structure to obtain a target rigid-flexible interconnect.

[0066] In this embodiment, the silver paste is conductive and can be made flexible but not stretchable. Therefore, by printing the silver paste on the first side of the stretchable substrate, a non-stretchable circuit layer can be formed, which is convenient for the subsequent combination of the stretchable substrate and the support layer to form a non-stretchable rigid circuit system; the liquid metal composite material not only has the characteristics of the liquid metal material, that is, it is soft and stretchable, but also overcomes the shortcomings of the liquid metal material, that is, it can avoid the rapid formation of an oxide layer and hinder the wetting of the substrate. Therefore, by printing the liquid metal composite material on the first side of the stretchable substrate, a high-quality stretchable circuit layer can be easily made. Combined with the stretchability of the stretchable substrate, a flexible circuit system can be formed, and it is ensured that the entire flexible circuit system formed has excellent stretchability, and not only the internal circuit is stretchable; wherein, the sealing layer formed by the encapsulation of the sealant can cover the stretchable circuit layer, which can avoid leakage or outflow of the liquid metal composite material, and play a sealing and protective role for the stretchable circuit layer; the support layer is attached to the second side of the second rigid-flexible composite structure, and can play a supporting role for the non-stretchable circuit layer.

[0067] The method for manufacturing a stretchable rigid-flexible interconnect in this embodiment is based on a stretchable circuit layer and a non-stretchable circuit layer with an overlapping area at the junction, which can truly form a rigid-flexible interconnect that electronically interconnects the rigid circuit system and the flexible circuit system. The entire rigid-flexible interconnect not only ensures functionality but also has excellent stretchability and can meet the requirements of current wearable electronic devices.

[0068] It should be understood that the silver paste, liquid metal composite material and sealant are all made on the first side of the stretchable substrate, and the support layer is made on the second side of the stretchable substrate. Therefore, the order of the steps S1~S2 of making the non-stretchable circuit layer, the stretchable circuit layer and the sealing layer in this embodiment and the step S3 of bonding the support layer in this embodiment is not unique. That is, the non-stretchable circuit layer, the stretchable circuit layer and the sealing layer can be made respectively according to steps S1~S2, and then the support layer can be bonded according to step S3. Alternatively, the support layer can be bonded according to step S3 first, and then the non-stretchable circuit layer, the stretchable circuit layer and the sealing layer can be made respectively according to steps S1~S2. Both can form the rigid-flexible interconnect with excellent stretchable performance in this embodiment. For ease of explanation, the following embodiments are described by taking the example of first following steps S1 to S2 to respectively produce a non-stretchable circuit layer, a stretchable circuit layer and a sealing layer, and then following step S3 to bond the support layer. The case of first following step S3 to bond the support layer, and then following steps S1 to S2 to respectively produce a non-stretchable circuit layer, a stretchable circuit layer and a sealing layer will not be repeated here.

[0069] Each step of the method for manufacturing the stretchable rigid-flexible interconnect of this embodiment is described in detail below.

[0070] In S1, the stretchable substrate provided is composed of a polymer film layer and a hot melt adhesive layer.

[0071] The polymer film layer has better elongation. Using this polymer film layer can make the entire stretchable substrate have good stretchability, which is convenient for providing excellent stretchability for the flexible circuit system together with the subsequently printed liquid metal composite material; using the hot-melt adhesive layer, it is convenient to easily bond the support layer subsequently, provide good support for the stretchable circuit layer, and form a high-quality rigid circuit system.

[0072] Preferably, the polymer film layer includes any one of an organic silicon film layer, an acrylic polymer film layer and a polyurethane film layer.

[0073] Silicone film layers (such as Dragon Skin silicone produced by Smooth-On in the United States) are mainly made of polydimethylsiloxane (PDMS) polymer cross-linked and solidified. They have a low Young's modulus and good flexibility and stretchability. They are highly corrosion-resistant, have high dielectric strength, and have good transparency and stability over a wide range of operating temperatures. They can be used as substrate materials for large-area transparent flexible electronic devices or thermally stable devices. In addition, they are easy to combine with electronic materials, fixing the electronic materials to their surface, making it convenient to print silver paste separately to form a non-stretchable circuit layer.

[0074] The acrylic polymer film layer (such as 3M VHB glue produced by 3M) is a film material layer made of acrylic polymer, which has excellent film-forming properties, outstanding chemical stability, good mechanical properties and good processing performance; the polyurethane film layer (such as thermoplastic polyurethanes, TPU) is a film made of polyurethane (Polyurethane, referred to as PU), a polymer material, with a unique block molecular structure, excellent wear resistance, flexibility, tear resistance and good elasticity, and can adapt to various complex deformations and stretching.

[0075] The above-mentioned polymer film layers can all ensure that the stretchable substrate has good stretchability.

[0076] In an optional embodiment, the stretchable substrate is made of TPU5855 film, that is, the polymer film layer is a TPU film with a thickness of 75 μm, which has better elongation, a typical elongation at break exceeding 500%, and a good recovery ability of less than 5% after 100% strain; the hot melt adhesive layer is a hot melt adhesive of model FDS5855X1 with a thickness of 25 μm.

[0077] In this embodiment S1, the silver paste has high conductivity and good chemical stability, and is not easily oxidized. Even if its surface is partially oxidized, the resulting oxide can still be conductive, which enables the silver paste to ensure smooth transmission of current in the application of the circuit layer; combined with the printing process, the circuit wire formed has higher resolution, better conductivity, a denser structure and a brighter surface, and is more resistant to moisture and corrosion of silk-screen copper wire; it has good adhesion to the substrate and is not easy to fall off on the stretchable substrate, making it possible to print electronic products with more complex structures and larger areas on the stretchable substrate.

[0078] In an optional embodiment, the silver paste may be ASH LS-411 or ASH LS-453 silver paste.

[0079] Liquid metal is an excellent conductor for soft and stretchable media. However, it is difficult to use directly as a conductive ink because it quickly forms an oxide layer that hinders substrate wetting. This embodiment uses a liquid metal polymer composite (LMPC), which maintains the material properties of liquid metal—its softness and stretchability—while overcoming its drawbacks by preventing the rapid formation of an oxide layer that hinders substrate wetting.

[0080] In this embodiment S1, the liquid metal composite material is made of silver powder, liquid metal and styrene-ethylene-butylene-styrene block copolymer.

[0081] In the aforementioned liquid metal composites, the addition of flake silver powder together with a compatible stretchable polymer (i.e., styrene-ethylene-butylene-styrene block copolymer) binder, as well as liquid metal as a dual phase in the Ag / binder matrix, can improve the processability of the liquid metal.

[0082] Preferably, the weight percentages of the silver powder, the liquid metal and the styrene-ethylene-butylene-styrene block copolymer in the liquid metal composite material are 28.2%, 68.3% and 3.4% respectively.

[0083] The stretchable circuit layer formed by the liquid metal composite material (LMPC) with the above weight percentage has excellent stretchability and can be used in areas of rigid-flexible interconnects that require high tensile strain; it can be used as a conductive line in a flexible circuit system and as a strain buffer for rigid-flexible interconnects; in addition, the liquid metal in the LMPC acts as a "healing" medium to bridge the separated flaky Ag powder when it is stretched apart, thereby maintaining electrical continuity.

[0084] Specifically, the liquid metal is a gallium-indium alloy, and the weight ratio of gallium to indium in the gallium-indium alloy is 3:1.

[0085] When the weight ratio of gallium and indium in the gallium-indium alloy is 3:1, it has the advantages of low melting point, good thermal stability, high electrical conductivity, good plasticity and ductility, etc., which can facilitate the production of liquid metal composite materials while ensuring the functionality of the formed stretchable circuit layer.

[0086] Preferably, in this embodiment S1, silver paste and liquid metal composite material are printed on the first side of the stretchable substrate respectively to form a non-stretchable circuit layer and a stretchable circuit layer respectively, to obtain a first rigid-flexible composite structure, comprising:

[0087] S11: providing the silver paste, and printing the silver paste on the side of the stretchable substrate having the polymer film layer;

[0088] S12: curing the stretchable substrate printed with the silver paste according to a first preset curing parameter to form the non-stretchable circuit layer;

[0089] S13: providing the liquid metal composite material, and printing the liquid metal composite material on a side of the stretchable substrate having the polymer film layer by using a dispensing printing or a stencil printing method;

[0090] S14: Drying the stretchable substrate printed with the liquid metal composite material according to preset drying parameters to form the stretchable circuit layer that is electrically connected to the non-stretchable circuit layer, thereby obtaining the first rigid-flexible composite structure.

[0091] In S11, silver paste can be printed using dispensing printing or screen printing. Dispensing printing (i.e., dispense printing) refers to the process of using a dispensing machine to continuously apply material to specified locations to achieve continuous printing of electronic circuits; screen printing (i.e., screen printing) refers to the process of using a silk screen as a base and using a photosensitive platemaking method to make a silk screen printing plate with graphics, and then using the silk screen printing plate to print electronic circuits.

[0092] In S13, liquid metal composite materials can be printed using dispensing printing or stencil printing. Stencil printing (i.e., stencil printing) refers to the process of engraving images and texts on sheets of wood, cardboard, metal, or plastic, hollowing them out to make a stencil, and then using brushing or spraying to allow ink to pass through the through holes and adhere to the substrate to achieve the process of printing electronic circuits.

[0093] When printing silver paste to produce a non-stretchable circuit layer in S11, the method of dispensing printing or screen printing is adopted, which can efficiently and accurately control the position and layout of the non-stretchable circuit layer. After printing, the stretchable substrate printed with silver paste is cured according to the first preset curing parameters in S12, which can ensure that the produced non-stretchable circuit layer meets the design requirements and improve the production accuracy and efficiency of the non-stretchable circuit layer. When printing liquid metal composite materials in S13, the method of dispensing printing or hollow plate printing is adopted, which can adapt to the characteristics of liquid metal composite materials and efficiently and accurately control the position and layout of the stretchable circuit layer. After printing, the stretchable substrate printed with liquid metal composite materials is dried according to the preset drying parameters in S14, which can also ensure that the produced non-stretchable circuit layer meets the design requirements and effectively improve the production accuracy and efficiency of the stretchable circuit layer.

[0094] Specifically, the first preset curing parameters include a first curing time and a first curing temperature.

[0095] Specifically, the preset drying parameters include drying time and drying temperature.

[0096] Through the above-mentioned first preset curing parameters, the material properties of the silver paste can be better adapted, thereby controlling the forming effect of the non-stretchable circuit layer; similarly, through the above-mentioned preset drying parameters, the material properties of the liquid metal composite material can be better adapted, thereby controlling the forming effect of the stretchable circuit layer.

[0097] In an optional embodiment, for silver paste, the first curing time is 30 minutes; and / or the first curing temperature is 80°C.

[0098] In an optional embodiment, for the liquid metal composite material, the drying time is 60 minutes; and / or the drying temperature is 60°C.

[0099] In an optional embodiment, the thickness of the non-stretchable circuit layer ranges from 1 to 100 μm; and / or the thickness of the stretchable circuit layer ranges from 1 to 300 μm.

[0100] It should be understood that the order of the steps S11~S12 for making the non-stretchable circuit layer and the steps S13~S14 for making the stretchable circuit layer in this embodiment is not unique. The non-stretchable circuit layer can be made first, or the stretchable circuit layer can be made first. In an optional embodiment, the order of making the non-stretchable circuit layer first and then the stretchable circuit layer is adopted. The top view structure of the non-stretchable circuit layer formed on the stretchable substrate is shown in Figure 2. Based on Figure 2, a stretchable circuit layer is formed on the stretchable substrate, and the top view structure of the obtained first rigid-flexible composite structure is shown in Figure 3. In Figures 2 and 3, 1 is the stretchable substrate, 2 is the non-stretchable circuit layer, and 3 is the stretchable circuit layer. The cross-sectional structure of the right half of the first rigid-flexible composite structure in Figure 3 is shown in Figure 4. In Figure 4, 11 is the polymer film layer in the stretchable substrate 1, and 12 is the hot-melt adhesive layer in the stretchable substrate 1. The cross-sectional structure of the left half is symmetrical with the cross-sectional structure shown in Figure 4 and is not shown here.

[0101] In Figure 3, a non-stretchable circuit layer 2 is formed at both ends of the stretchable substrate 1, and a stretchable circuit layer 3 is formed between the non-stretchable circuit layers 2 at both ends, and electrical conduction is formed between the stretchable circuit layer 3 and the non-stretchable circuit layers 2 at both ends. In actual processes, a non-stretchable circuit layer 2 can also be formed at one end of the stretchable substrate 1, and electrical conduction is formed between the stretchable circuit layer 3 and the non-stretchable circuit layer. The position, number, and layout of the non-stretchable circuit layer 2 and the stretchable circuit layer 3 depend on the specific product design, and electrical conduction must be ensured between the non-stretchable circuit layer 2 and the stretchable circuit layer 3.

[0102] Preferably, in S1, a length of the overlapping region between the non-stretchable circuit layer and the stretchable circuit layer along the stretching direction of the stretchable circuit layer is greater than or equal to 0.1 mm.

[0103] In Figure 4 , the first side of the stretchable substrate 1 refers to the region of the upper surface of the stretchable substrate 1, while the second side refers to the region of the lower surface of the stretchable substrate 1. The stretching direction of the stretchable circuit layer 3 is the x-direction in Figure 4 . Therefore, there is an overlapping region at the junction between the non-stretchable circuit layer 2 and the stretchable circuit layer 3, as indicated by 100 in Figure 4 . The length L of this overlapping region 100 along the x-direction is ≥ 0.1 mm.

[0104] By limiting the length of the overlapping area mentioned above, the electronic interconnection at the interconnection interface between the flexible circuit system and the rigid circuit system can be better guaranteed, thereby effectively ensuring the functionality of the rigid-flexible interconnection component; at the same time, it also facilitates the subsequent sealant to better fill the edge of the stretchable circuit layer, better encapsulate or seal the stretchable circuit layer, and ensure that the formed sealing layer plays a better sealing role.

[0105] In this embodiment S2, due to the fluidity of the liquid metal composite material, the liquid metal composite material may leak or flow out from the matrix during the stretching of the stretchable circuit layer. By providing a sealant and utilizing the encapsulation of the sealant, this situation can be controlled and the printed conductive LMPC traces (i.e., the stretchable circuit layer) can be encapsulated or sealed.

[0106] The provided sealant includes any one or any combination of silicone, acrylic polymer and polyurethane.

[0107] The above-mentioned sealant can not only encapsulate or seal the stretchable circuit layer, but also ensure that the sealant also has a certain degree of stretchability, so that it can be stretched together with the stretchable circuit layer, thereby realizing a rigid-flexible interconnect with excellent stretchable performance.

[0108] Based on the above sealant, the formed sealing layer includes any one of an organic silicon film layer, an acrylic polymer film layer and a polyurethane film layer, or a film layer formed by any combination of several of them.

[0109] In an optional embodiment, the sealant is ecoflex-010 silicone, which is more compatible with the hollow plate printing process.

[0110] Preferably, in this embodiment S2, the first rigid-flexible composite structure is encapsulated with the sealant to form a sealing layer, so that the stretchable circuit layer is covered by the sealing layer, thereby obtaining a second rigid-flexible composite structure, including:

[0111] S21: Printing the sealant onto a side of the first rigid-flexible composite structure having the stretchable circuit layer;

[0112] S22: Curing the first rigid-flexible composite structure printed with the sealant according to second preset curing parameters to form the sealing layer on the first rigid-flexible composite structure, so that the stretchable circuit layer is completely covered by the sealing layer to obtain the second rigid-flexible composite structure.

[0113] In S21, a hollow plate printing method is specifically used to print the sealant onto the side of the first rigid-flexible composite structure having the stretchable circuit layer. This can easily realize the printing of sealants of different shapes and sizes, and can adapt to stretchable circuit layers of different shapes and sizes, so that the subsequently formed sealing layer can completely cover the stretchable circuit layer, thereby playing an excellent sealing role. After the sealant is printed, it is cured according to the second preset curing parameters in S22, which can efficiently form a sealing layer, thereby further ensuring that the sealing layer plays an excellent sealing role.

[0114] Because the stretchable and non-stretchable circuit layers overlap at their interface, the edges of the sealing layer can extend onto the non-stretchable circuit layer to ensure the stretchable circuit layer is completely covered by the sealing layer. As shown in Figure 5, a cross-sectional view of the right half of the second rigid-flexible composite structure shows that the sealing layer 4 covers the stretchable circuit layer 3, and the edges of the sealing layer 4 extend onto the non-stretchable circuit layer 2.

[0115] The top view structure of the second rigid-flexible composite structure of this embodiment is shown in FIG6 .

[0116] Specifically, the second preset curing parameters include a second curing time and a second curing temperature.

[0117] Similar to the first preset curing parameter, the second preset curing parameter can better adapt to the material properties of the sealant, thereby controlling the molding effect of the sealing layer.

[0118] In an optional embodiment, the second curing time is 2 hours; and / or the second curing temperature is 80°C.

[0119] In an optional embodiment, the thickness of the sealing layer ranges from 0.1 to 2 mm.

[0120] In an optional embodiment, the thickness of the sealing layer is specifically 0.25 mm.

[0121] Preferably, in this embodiment S3, by laminating the support layer to the second side of the stretchable substrate, it can provide support for the non-stretchable circuit layer on the first side of the stretchable substrate, ensuring that when the stretchable circuit layer is stretched, the non-stretchable circuit layer is better fixed on the stretchable substrate, thereby effectively ensuring the functionality of the non-stretchable circuit layer and truly realizing the electronic interconnection between the rigid circuit system and the flexible circuit system.

[0122] In this embodiment S3, laminating the support layer on the second side of the second rigid-flexible composite structure includes:

[0123] S31: bonding the support layer to the side of the second rigid-flexible composite structure having the hot-melt adhesive layer;

[0124] S32: thermally laminating the second rigid-flexible composite structure bonded with the support layer according to preset lamination parameters.

[0125] Based on the hot-melt adhesive layer in the stretchable substrate, the support layer can be easily bonded to the second side of the stretchable substrate using the hot lamination method, ensuring that the support layer supports the stretchable circuit layer; at the same time, under the hot lamination pressure, the liquid metal in the stretchable circuit layer will be "squeezed" and fill the gaps between the silver powder in the liquid metal composite material, as shown in Figure 7, which will bring better conductivity and further compact the liquid metal composite material to form a better quality stretchable circuit layer, thereby improving the quality of the target rigid-flexible interconnection component finally formed.

[0126] In FIG7 , 5 is silver powder in the liquid metal composite material, and 6 is liquid metal in the liquid metal composite material.

[0127] Specifically, the preset lamination parameters include lamination temperature, lamination time and lamination pressure.

[0128] By using the above-mentioned preset lamination parameters, it is possible to ensure that a support layer that meets the requirements is formed and the functionality of the support layer is ensured.

[0129] In an optional embodiment, the lamination temperature ranges from 100 to 120° C.; and / or the lamination time ranges from 10 to 30 seconds; and / or the lamination pressure ranges from 4 to 7 Bar.

[0130] The above parameters can ensure efficient bonding to the support layer, while also activating the liquid metal filler in the stretchable circuit layer to improve the conductivity of the stretchable circuit layer.

[0131] Preferably, the projection of the supporting layer on the stretchable substrate covers the projection of the non-stretchable circuit layer on the stretchable substrate.

[0132] The projection of the support layer on the stretchable substrate covers the projection of the non-stretchable circuit layer on the stretchable substrate, which enables the support layer to better provide support for the non-stretchable circuit layer, avoiding the rigid circuit system being stretched along with the flexible circuit system when being stretched, causing the electronic components in the rigid circuit system to be damaged, and ensuring the functionality of the ultimate target rigid-flexible interconnect.

[0133] The top view structure of the second rigid-flexible composite structure after the support layer is bonded in this embodiment is shown in FIG8 , and the corresponding cross-sectional structure of the right half is shown in FIG9 . In FIG8 and FIG9 , 7 is the support layer.

[0134] In Figure 9, when the projection of the supporting layer 7 on the stretchable substrate 1 covers the projection of the non-stretchable circuit layer 2 on the stretchable substrate 1, it means that the edge line of the supporting layer 7 close to the stretchable circuit layer 3 (such as line B in Figure 9) is flush with the boundary line between the non-stretchable circuit layer 2 and the stretchable circuit layer 3 (such as line A in Figure 9), or the edge line of the supporting layer 7 close to the stretchable circuit layer 3 (such as line B in Figure 9) exceeds the boundary line between the non-stretchable circuit layer 2 and the stretchable circuit layer 3 (such as line A in Figure 9), that is, the edge line of the supporting layer 7 close to the stretchable circuit layer 3 (line B) is closer to the stretchable circuit layer 3 than the boundary line (line A) between the non-stretchable circuit layer 2 and the stretchable circuit layer 3.

[0135] The support layer in this embodiment can be a rigid material layer (as shown in Figure 9), that is, a material layer with a large elastic modulus, including any one of a steel layer (made of steel), a reinforcement layer (made of organic glass fiber reinforcement material, which is composed of glass fiber and epoxy resin), an FR-4 substrate layer (made of glass fiber reinforced epoxy resin), a polycarbonate layer (made of PC, PC is Polycarbonate, a thermoplastic plastic), a polyethylene terephthalate layer (made of PET, PET is Polyethylene Terephthalate, a thermoplastic polyester) and a polyimide layer (made of PI, PI is Polyimide).

[0136] The support layer in this embodiment can also be a support layer with gradient stiffness composed of at least one flexible material layer and one rigid material layer. The flexible material layers are stacked on the second side of the stretchable substrate in a specified order, and the rigid material layer can be stacked on the outside of all the flexible material layers (as shown in FIG. 10 , FIG. 10 has two flexible material layers), or can be embedded inside one of the flexible material layers (as shown in FIG. 11 , FIG. 11 has one flexible material layer). In FIG. 10 and FIG. 11 , 71 is a rigid material layer and 72 is a flexible material layer. In this case, the projection of the support layer on the stretchable substrate overlaps the projection of the non-stretchable circuit layer on the stretchable substrate, specifically, the projection of the rigid material layer on the stretchable substrate overlaps the projection of the non-stretchable circuit layer on the stretchable substrate.

[0137] The flexible material layer refers to a material layer with a relatively small elastic modulus, including any one of an organic silicon layer, an acrylic polymer layer and a polyurethane layer.

[0138] In an optional embodiment, the support layer is specifically a 0.125 mm hard PET film.

[0139] Preferably, in this embodiment S3, after laminating the support layer to the second side of the second rigid-flexible composite structure, the method further includes:

[0140] S33: mounting an electronic component on the non-stretchable circuit layer in the second rigid-flexible composite structure bonded with the support layer, so that electrical conduction is established between the electronic component and the non-stretchable circuit layer;

[0141] S34: Curing the second rigid-flexible composite structure after the electronic component is mounted thereon according to a third preset curing parameter.

[0142] Through the above steps, electronic components can be mounted on the non-stretchable circuit layer, and the final rigid circuit system can be formed as required by the design requirements, thereby ensuring the production of the target rigid-flexible interconnect that meets the design requirements.

[0143] In an optional embodiment, electronic components (such as resistors and capacitors) can be mounted using conductive adhesive. To improve strength, SMT adhesive (surface mount adhesive) can also be used, using SMT (surface mount technology) for mounting. SMT is a conventional mounting technology, and its specific details are not detailed here.

[0144] Specifically, the third preset curing parameters include a third curing time and a third curing temperature.

[0145] Similar to the first preset curing parameter and the second preset curing parameter, the third preset curing parameter can better control the placement effect of the electronic components to ensure that it meets the design requirements.

[0146] In an optional embodiment, the third curing time is 30 minutes; and / or the third curing temperature is 120°C.

[0147] In the actual production process, if there is a circuit system in the non-stretchable circuit that needs to be protected or isolated in the product design, after printing the silver paste on the first side of the stretchable substrate, a layer of dielectric ink needs to be applied on top of the silver paste to play the role of insulation and isolation protection.

[0148] The top view structure of the target rigid-flexible interconnect obtained in this embodiment is shown in FIG12 . In FIG12 , 8 represents an electronic component.

[0149] The sample was made by the manufacturing method of this embodiment, and a hard PET film was used as a support layer and laminated on the bottom side of the stretchable substrate. The manufactured samples were subjected to tensile tests at different strain rates. In order to facilitate testing, the sample was not assembled with electronic components, and only a stretchable circuit layer with only a single stretchable conductive trace was interconnected to the pad in the non-stretchable circuit layer. The stretchability test curve obtained by the stretchability test is shown in Figure 13, wherein the stretchability test was carried out at 100% strain and a stretching rate of 3mm / sec. In Figure 13, the resistance ratio (i.e., R / R0, which refers to the ratio between the resistance of the stretchable conductive trace after repeated stretching and the initial resistance before stretching) of the sample manufactured by the manufacturing method of this embodiment after about 10,000 repeated stretchings is stable, and is about 2.20 at the 9823rd repeated stretching (wherein R0 is in the range of 1-2Ω, which is suitable for most electronic applications), reflecting relatively good tensile properties and stability.

[0150] Example 2

[0151] This embodiment provides a stretchable rigid-flexible interconnect, which is manufactured using the method for manufacturing a stretchable rigid-flexible interconnect described in the first embodiment.

[0152] The stretchable rigid-flexible interconnect manufactured in this embodiment not only ensures functionality but also has excellent stretchability and can meet the requirements of current wearable electronic devices.

[0153] The manufacturing method of the stretchable rigid-flexible interconnect in this embodiment is the same as the method steps described in Example 1. Therefore, for any unfinished details of this embodiment, please refer to the specific description of Example 1 and Figures 1 to 13, and will not be repeated in this embodiment.

[0154] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for manufacturing a stretchable rigid-flexible interconnect, characterized in that: include: Providing a stretchable substrate, and printing silver paste and a liquid metal composite material on a first side of the stretchable substrate to form a non-stretchable circuit layer and a stretchable circuit layer, respectively, to obtain a first rigid-flexible composite structure; wherein the non-stretchable circuit layer and the stretchable circuit layer have an overlapping area at their junction; Providing a sealant, and encapsulating the first rigid-flexible composite structure with the sealant to form a sealing layer, so that the stretchable circuit layer is covered by the sealing layer, thereby obtaining a second rigid-flexible composite structure; A support layer is provided, and the support layer is attached to the second side of the second rigid-flexible composite structure to obtain a target rigid-flexible interconnect.

2. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 1, wherein: The liquid metal composite material is made of silver powder, liquid metal and styrene-ethylene-butylene-styrene block copolymer.

3. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 2, wherein: The weight percentages of the silver powder, the liquid metal, and the styrene-ethylene-butylene-styrene block copolymer in the liquid metal composite material are 28.2%, 68.3%, and 3.4%, respectively.

4. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 2, wherein: The liquid metal is specifically a gallium-indium alloy, and the weight ratio of gallium to indium in the gallium-indium alloy is 3:

1.

5. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 1, wherein: A length of the overlapping region between the non-stretchable circuit layer and the stretchable circuit layer along the stretching direction of the stretchable circuit layer is greater than or equal to 0.1 mm.

6. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 1, wherein: The stretchable substrate is composed of a polymer film layer and a hot melt adhesive layer; Wherein, the thickness of the polymer film layer is 75 μm, and / or the thickness of the hot-melt adhesive layer is 25 μm.

7. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 6, wherein: The polymer film layer includes any one of an organic silicon film layer, an acrylic polymer film layer and a polyurethane film layer.

8. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 6, wherein: Silver paste and liquid metal composite material are printed on the first side of the stretchable substrate to form a non-stretchable circuit layer and a stretchable circuit layer, respectively, to obtain a first rigid-flexible composite structure, comprising: Providing the silver paste, and printing the silver paste on the side of the stretchable substrate having the polymer film layer; curing the stretchable substrate printed with the silver paste according to a first preset curing parameter to form the non-stretchable circuit layer; Providing the liquid metal composite material, and printing the liquid metal composite material on the side of the stretchable substrate having the polymer film layer; The stretchable substrate printed with the liquid metal composite material is dried according to preset drying parameters to form the stretchable circuit layer that is in electrical conduction with the non-stretchable circuit layer, thereby obtaining the first rigid-flexible composite structure.

9. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 8, wherein: The first preset curing parameters include a first curing time and a first curing temperature; and / or the preset drying parameters include a drying time and a drying temperature.

10. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 9, wherein: The first curing time is 30 minutes; and / or the first curing temperature is 80°C; the drying time is 60 minutes; and / or the drying temperature is 60°C.

11. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 6, wherein: Laminating the support layer on the second side of the second rigid-flexible composite structure includes: Bonding the support layer to the side of the second rigid-flexible composite structure having the hot-melt adhesive layer; The second rigid-flexible composite structure bonded with the support layer is thermally laminated according to preset lamination parameters.

12. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 11, wherein: The preset lamination parameters include lamination temperature, lamination time and lamination pressure; Wherein, the lamination temperature ranges from 100 to 120° C.; and / or, the lamination time ranges from 10 to 30 seconds; and / or, the lamination pressure ranges from 4 to 7 Bar.

13. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 1, wherein: The first rigid-flexible composite structure is encapsulated with the sealant to form a sealing layer, so that the stretchable circuit layer is covered by the sealing layer, thereby obtaining a second rigid-flexible composite structure, comprising: Printing the sealant onto the side of the first rigid-flexible composite structure having the stretchable circuit layer; The first rigid-flexible composite structure printed with the sealant is cured according to second preset curing parameters to form the sealing layer on the first rigid-flexible composite structure, so that the stretchable circuit layer is completely covered by the sealing layer to obtain the second rigid-flexible composite structure.

14. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 13, wherein: The second preset curing parameters include a second curing time and a second curing temperature; Wherein, the second curing time is 2 hours; and / or the second curing temperature is 80°C.

15. The method for manufacturing a stretchable rigid-flexible interconnect according to any one of claims 1 to 14, wherein: The thickness of the non-stretchable circuit layer ranges from 1 to 100 μm; and / or the thickness of the stretchable circuit layer ranges from 1 to 300 μm.

16. The method for manufacturing a stretchable rigid-flexible interconnect according to any one of claims 1 to 14, wherein: The thickness of the sealing layer ranges from 0.1 to 2 mm.

17. The method for manufacturing a stretchable rigid-flexible interconnect according to any one of claims 1 to 14, wherein: The sealing layer includes any one of an organic silicon film layer, an acrylic polymer film layer and a polyurethane film layer, or a film layer formed by any combination of several of them.

18. The method for manufacturing a stretchable rigid-flexible interconnect according to any one of claims 1 to 14, wherein: The projection of the supporting layer on the stretchable substrate covers the projection of the non-stretchable circuit layer on the stretchable substrate.

19. The method for manufacturing a stretchable rigid-flexible interconnect according to any one of claims 1 to 14, wherein: After the support layer is attached to the second side of the second rigid-flexible composite structure, the method further includes: Mounting an electronic component on the non-stretchable circuit layer in the second rigid-flexible composite structure on which the support layer is attached, so that electrical conduction is established between the electronic component and the non-stretchable circuit layer; The second rigid-flexible composite structure after the electronic component is mounted is cured according to a third preset curing parameter.

20. The method for manufacturing a stretchable rigid-flexible interconnect according to claim 19, wherein: The third preset curing parameters include a third curing time and a third curing temperature; Wherein, the third curing time is 30 minutes; and / or the third curing temperature is 120°C.

21. A stretchable rigid-flexible interconnect, characterized in that: The stretchable rigid-flexible interconnect is manufactured using the manufacturing method of any one of claims 1 to 20.

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