Stretchable flexible circuit board

Abstract

The utility model discloses a stretchable flexible circuit board. The stretchable flexible circuit board comprises a flexible circuit substrate provided with a winding circuit; the first elastic body has a first tensile modulus, is arranged on the periphery of the flexible circuit base material and seals the winding circuit inside; the second elastic body has a second tensile modulus and is arranged on the periphery of the first elastic body, and the first elastic body and the winding line in the first elastic body are sealed in the second elastic body; wherein the first tensile modulus is smaller than the second tensile modulus. According to the utility model, the winding circuit on the flexible circuit substrate is packaged through the two layers of elastomers with different tensile moduli, and the tensile modulus of the tensile module of the inner layer is smaller than that of the tensile module of the outer layer, so that the whole flexible circuit board is ensured to have excellent tensile performance; and the comprehensive performance of the whole flexible circuit board in the aspects of hardness, tensile strength, tearing strength and the like can be improved, and the flexible circuit board has the advantages of high tensile property and high hardness.

Description

Technical Field

[0001] The utility model relates to the technical field of flexible printed circuit boards, and particularly relates to a stretchable flexible printed circuit board. Background Art

[0002] At present, stretchable flexible printed circuit boards have received increasing attention and research. A stretchable flexible printed circuit board can ensure that the conductivity of the circuit hardly changes while being stretched and its size changes. This characteristic enables electronic products (such as wearable electronic products) using the stretchable flexible printed circuit board to have better comfort, can meet more usage scenarios, and can help engineers develop more functional products.

[0003] At present, a common method for manufacturing a stretchable flexible printed circuit board is to cut the circuit layer inside the flexible printed circuit board into a serpentine structure, and then encapsulate the printed circuit board with an elastomer material having a higher elongation rate. The stretchable flexible printed circuit board prepared by this method has high tensile performance, is easy to rebound and maintain the previous length after stretching, and thus has high practicality. Among them, the performance of the elastomer has a great influence on the tensile elongation rate and tensile fatigue life of the stretchable flexible printed circuit board. Generally speaking, a stretchable flexible printed circuit board prepared with an elastomer having a lower tensile modulus and a higher elongation rate has a higher tensile elongation rate and a better tensile fatigue life. However, an elastomer with a lower tensile modulus usually has lower performance in terms of hardness (including hardness, tensile strength, tear strength, etc.), which makes it difficult for such materials with better tensile performance (i.e., materials with a lower tensile modulus) to meet application scenarios with high requirements for hardness performance. That is to say, there is a contradiction between the tensile performance and the hardness performance requirements of the current stretchable flexible printed circuit boards, and it is impossible to have both high tensile performance and high hardness performance at the same time. Summary of the Utility Model

[0004] In view of this, an embodiment of the utility model provides a stretchable flexible printed circuit board to solve the problem that there is a contradiction between the tensile performance and the hardness performance requirements of the existing stretchable flexible printed circuit boards, and it is impossible to have both high tensile performance and high hardness performance at the same time.

[0005] The utility model provides a stretchable flexible printed circuit board, comprising:

[0006] A flexible printed circuit substrate provided with a serpentine circuit;

[0007] A first elastomer having a first tensile modulus, disposed on the outer periphery of the flexible printed circuit substrate and sealing the serpentine circuit therein; and

[0008] A second elastomer having a second tensile modulus, disposed on the outer periphery of the first elastomer and sealing both the first elastomer and the serpentine circuit inside the first elastomer;

[0009] Among them, the first tensile modulus is less than the second tensile modulus.

[0010] Optionally, the first elastomer is specifically any one of silicone rubber elastomers, polyurethane elastomers, and polystyrene block elastomers; and / or, the second elastomer is specifically any one of silicone rubber elastomers, polyurethane elastomers, and polystyrene block elastomers.

[0011] Optionally, the range of the first tensile modulus is 0.05 - 50 MPa; and / or, the range of the second tensile modulus is 1 - 1000 MPa.

[0012] Optionally, the range of the first tensile modulus is 0.1 - 10 MPa; and / or, the range of the second tensile modulus is 1 - 100 MPa.

[0013] Optionally, the thickness range of the first elastomer is 0.03 - 2 mm; and / or, the thickness range of the second elastomer is 0.1 - 10 mm.

[0014] Optionally, the thickness range of the first elastomer is 0.2 - 1 mm; and / or, the thickness range of the second elastomer is 1 - 3 mm.

[0015] Optionally, the first elastomer has a first elongation at break, and the range of the first elongation at break is 100 - 2000%.

[0016] Optionally, the range of the first elongation at break is 300 - 1000%.

[0017] Optionally, the second elastomer has a second elongation at break, and the range of the second elongation at break is 50 - 1000%.

[0018] Optionally, the range of the second elongation at break is 100 - 500%.

[0019] Advantages of the present utility model: The meandering lines on the flexible circuit substrate are encapsulated by two layers of elastomers with different tensile moduli (i.e., the first elastomer and the second elastomer). Among them, the inner elastomer (i.e., the first elastomer) has a lower tensile modulus, and the outer elastomer (i.e., the second elastomer) has a higher tensile modulus, which can not only ensure that the entire flexible circuit board has excellent tensile properties, but also improve the comprehensive properties of the entire flexible circuit board in terms of hardness, tensile strength, tear strength, etc. The stretchable flexible circuit board provided by the present utility model has the advantages of both high tensile performance and high hardness performance. Description of the Drawings

[0020] The features and advantages of the present utility model will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as imposing any limitations on the present utility model. In the drawings:

[0021] Figure 1 shows the front view of the stretchable flexible printed circuit board in an embodiment of the present utility model;

[0022] Figure 2 shows the top view of the stretchable flexible printed circuit board in an embodiment of the present utility model;

[0023] Figure 3 shows the cross-sectional view of the stretchable flexible printed circuit board in an embodiment of the present utility model.

[0024] The descriptions of the reference numerals in each drawing are as follows:

[0025] 101, flexible printed circuit substrate; 102, first elastomer; 103, second elastomer; 1011, meandering circuit; 1012, transition region; 1013, non-stretchable region; 10111, circuit unit. Detailed implementation manners

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0027] Embodiment

[0028] This embodiment provides a stretchable flexible printed circuit board, as Figures 1 to 3 shown, including:

[0029] A flexible printed circuit substrate 101 provided with a meandering circuit 1011;

[0030] A first elastomer 102 having a first tensile modulus, disposed on the outer periphery of the flexible printed circuit substrate 101, and sealing the meandering circuit 1011 therein; and

[0031] A second elastomer 103 having a second tensile modulus, disposed on the outer periphery of the first elastomer 102, and sealing both the first elastomer 102 and the meandering circuit 1011 inside the first elastomer 102;

[0032] wherein, the first tensile modulus is less than the second tensile modulus.

[0033] In this embodiment, the meandering circuit on the flexible circuit substrate is encapsulated by two elastomers with different tensile moduli (i.e., the first elastomer and the second elastomer). The inner elastomer (i.e., the first elastomer) has a lower tensile modulus, and the outer elastomer (i.e., the second elastomer) has a higher tensile modulus. This can not only ensure that the entire flexible circuit board has excellent tensile properties, but also improve the comprehensive performance of the entire flexible circuit board in terms of hardness, tensile strength, tear strength, etc. The stretchable flexible circuit board provided in this embodiment has the advantages of both high tensile performance and high hardness performance.

[0034] Among them, Figure 1 is the front view of the stretchable flexible circuit board, Figure 2 is the top view of the stretchable flexible circuit board, Figure 3 is the cross-sectional view of the stretchable flexible circuit board.

[0035] Next, each component part of the stretchable flexible circuit board in this embodiment will be described in detail.

[0036] The flexible circuit substrate in this embodiment can be either a single-sided copper-clad substrate, which is composed of a copper layer and an insulating layer laminated together, or a double-sided copper-clad substrate, which is composed of two copper layers and an insulating layer laminated together, with the two copper layers located on both sides of the insulating layer respectively.

[0037] As Figure 2 shown, the flexible circuit substrate 101 in this embodiment includes:

[0038] a meandering circuit 1011;

[0039] two transition regions 1012, which are connected to the two ends of the meandering circuit 1011 in one-to-one correspondence; and

[0040] two non-stretchable regions 1013, which are connected to the two transition regions 1012 in one-to-one correspondence.

[0041] In the above flexible circuit substrate, the meandering circuit 1011 is etched from the copper layer on the flexible circuit substrate. The meandering circuit 1011 is a circuit in a meandering shape, corresponding to a straight circuit, and is composed of a plurality of circuit units with the same pattern connected end to end in sequence (i.e., Figure 2 10111 in

[0042] The wire harness in the meandering line 1011 can be composed of one or more wire cores. The wire cores have a wire core width, and there is also a wire core spacing between adjacent wire cores. In this embodiment, the range of the wire core width is 25 - 500 μm, preferably 35 - 50 μm; the range of the wire core spacing is 25 - 500 μm, preferably 35 - 50 μm.

[0043] In the above flexible circuit substrate, the transition region 1012 can also be etched from the copper layer in the flexible circuit substrate 101, getting thicker from thin along the direction towards the non-stretchable region. This structure can make the stress of the meandering line change gradually when being stretched, and it is not easy to be broken.

[0044] In the above flexible circuit substrate, the non-stretchable region 1013 can also be etched from the copper layer in the flexible circuit substrate 101. Its size is fixed, usually rectangular, and does not change during stretching. The resistive element can be mounted on the non-stretchable region 1013.

[0045] Preferably, the first tensile modulus is 0.1% - 70% of the second tensile modulus.

[0046] Preferably, the first elastomer 102 is specifically any one of silicone rubber elastomer, polyurethane elastomer, and polystyrene block elastomer.

[0047] Preferably, the second elastomer 103 is specifically any one of silicone rubber elastomer, polyurethane elastomer, and polystyrene block elastomer.

[0048] The above several elastomer materials all have the characteristics of high tear strength, high elongation rate, good shock absorption effect, excellent wear resistance, and good low-temperature elasticity. Therefore, as the sealing layer of the meandering line, it can not only ensure that the meandering line exerts its own stretchability to the greatest extent, but also effectively improve the comprehensive performance of the entire stretchable flexible circuit board in terms of hardness, tensile strength, and tear strength.

[0049] Among them, silicone rubber elastomer is a kind of high molecular elastomer with a main chain composed of silicon and oxygen atoms and organic groups (such as methyl, vinyl, etc.) on the side chain; polyurethane elastomer is a kind of high molecular material made by reacting raw materials such as isocyanate and polyol; polystyrene block elastomer, also known as styrene block copolymer (SBCs), is usually composed of hard segment polystyrene (PS) and soft segment polyolefin (such as polybutadiene, polyisoprene) or poly(styrene-ethylene / butylene-styrene) (SEBS) and other blocks.

[0050] In this embodiment, the first elastomer can be sealed on the outer periphery of the flexible circuit substrate by means of lamination, injection molding, bonding, etc., and the second elastomer can also be sealed on the outer periphery of the first elastomer by means of lamination, injection molding, bonding, etc.

[0051] Preferably, the range of the first tensile modulus is 0.05 to 50 MPa.

[0052] Preferably, the range of the second tensile modulus is 1 to 1000 MPa.

[0053] Further, the range of the first tensile modulus is 0.1 to 10 MPa.

[0054] Further, the range of the second tensile modulus is 1 to 100 MPa.

[0055] With the tensile moduli within the above two ranges, it can be ensured that the tensile modulus of the inner elastomer is less than that of the outer elastomer, enabling the inner elastomer to have better tensile properties relative to the outer elastomer, while enabling the outer elastomer to have better hardness properties relative to the inner elastomer. Furthermore, it can ensure that the entire flexible printed circuit board not only has excellent tensile properties but also takes into account the comprehensive properties in terms of hardness, tensile strength, tear strength, etc., and at the same time combines the advantages of high tensile properties and high hardness properties.

[0056] Preferably, the thickness range of the first elastomer 102 is 0.03 to 2 mm.

[0057] Preferably, the thickness range of the second elastomer 103 is 0.1 to 10 mm.

[0058] Further, the thickness range of the first elastomer 102 is 0.2 to 1 mm.

[0059] Further, the thickness range of the second elastomer 103 is 1 to 3 mm.

[0060] The first elastomer and the second elastomer within the above thickness ranges can not only seal the inner meandering circuit but also ensure that the properties of the elastomer and the meandering circuit are fully exerted.

[0061] Preferably, the first elastomer 102 has a first elongation at break, and the range of the first elongation at break is 100 to 2000%.

[0062] Further, the range of the first elongation at break is 300 to 1000%.

[0063] Preferably, the second elastomer 103 has a second elongation at break, and the range of the second elongation at break is 50 to 1000%.

[0064] Further, the range of the second elongation at break is 100 to 500%

[0065] The ranges of the above first elongation at break and second elongation at break can further help resolve the contradiction between the tensile performance and hardness performance of the entire stretchable flexible printed circuit board, and further ensure that the entire stretchable flexible printed circuit board has the advantages of both high tensile performance and high hardness performance.

[0066] Next, six samples of the stretchable flexible printed circuit boards of this embodiment are compared with two samples of traditional stretchable flexible printed circuit boards. Among them, the six samples of the stretchable flexible printed circuit boards of this embodiment are different in the material selection and parameters of the first elastomer and the second elastomer, specifically as follows:

[0067] Example 1

[0068] The first elastomer specifically uses a polyurethane elastomer with a thickness of 0.1 mm and a tensile modulus of 5 MPa. The second elastomer specifically uses a silicone rubber elastomer with a thickness of 1 mm and a tensile modulus of 15 MPa.

[0069] Example 2

[0070] The first elastomer specifically uses a polyurethane elastomer with a thickness of 0.8 mm and a tensile modulus of 5 MPa. The second elastomer specifically uses a silicone rubber elastomer with a thickness of 1 mm and a tensile modulus of 15 MPa.

[0071] Example 3

[0072] The first elastomer specifically uses a polyurethane elastomer with a thickness of 0.1 mm and a tensile modulus of 0.5 MPa. The second elastomer specifically uses a silicone rubber elastomer with a thickness of 1 mm and a tensile modulus of 15 MPa.

[0073] Example 4

[0074] The first elastomer specifically uses a SEBS elastomer with a thickness of 0.1 mm and a tensile modulus of 5 MPa. The second elastomer specifically uses a polyurethane elastomer with a thickness of 1 mm and a tensile modulus of 15 MPa.

[0075] Example 5

[0076] The first elastomer specifically uses a polyurethane elastomer with a thickness of 0.1 mm and a tensile modulus of 5 MPa. The second elastomer specifically uses a silicone rubber elastomer with a thickness of 2 mm and a tensile modulus of 15 MPa.

[0077] Example 6

[0078] The first elastomer specifically uses a polyurethane elastomer with a thickness of 0.1 mm and a tensile modulus of 5 MPa. The second elastomer specifically uses a silicone rubber elastomer with a thickness of 1 mm and a tensile modulus of 150 MPa.

[0079] Comparative Example 1

[0080] There is no first elastomer. The second elastomer is specifically a silicone rubber elastomer with a thickness of 1 mm and a tensile modulus of 15 MPa.

[0081] Comparative Example 2

[0082] There is no first elastomer. The second elastomer is specifically a silicone rubber elastomer with a thickness of 1 mm and a tensile modulus of 150 MPa.

[0083] First, the tensile cycle number tests are respectively carried out on the above-mentioned 8 kinds of samples in total. The test method is as follows:

[0084] 1. Measure the length of the stretchable area (i.e., the meandering line) of each sample, denoted as L 0 , and then fix both ends of the sample on the fixture of the tensile fatigue testing machine to keep the natural form of the sample;

[0085] 2. Connect the resistance test electrodes to both ends of the meandering line to test whether the metal wire in the meandering line is open-circuited;

[0086] 3. Stretch the sample cyclically. Each time of stretching makes the stretchable area of the sample elongate by 100% of the length, and stretch 45 times per minute until the test is damaged or the wire is open-circuited.

[0087] Then, the maximum elongation rate and tensile strength of each sample are respectively tested by using conventional measurement methods, and the surface hardness of each sample is tested by using a Shore A hardness tester. Finally, the comparison results of the maximum tensile rate, tensile strength and surface hardness of the 8 kinds of samples are shown in Table 1.

[0088] Table 1 Comparison results of the maximum tensile rate, tensile strength and surface hardness of 8 kinds of samples

[0089]

[0090] As can be seen from Table 1 above, the 6 kinds of samples in this embodiment all have excellent tensile properties and hardness properties, and at the same time have the advantages of high tensile properties and high hardness properties.

[0091] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A stretchable flexible circuit board, characterized in that: include: A flexible circuit substrate having a meandering circuit; A first elastic body having a first tensile modulus is disposed on the periphery of the flexible circuit substrate and seals the meandering circuit therein; as well as A second elastic body having a second tensile modulus is disposed on the periphery of the first elastic body and seals the first elastic body and the meandering line inside the first elastic body; Wherein, the first tensile modulus is smaller than the second tensile modulus.

2. The stretchable flexible circuit board according to claim 1, characterized in that: The first elastomer is specifically any one of a silicone rubber elastomer, a polyurethane elastomer and a polystyrene block elastomer; and / or the second elastomer is specifically any one of a silicone rubber elastomer, a polyurethane elastomer and a polystyrene block elastomer.

3. The stretchable flexible circuit board according to claim 1, characterized in that: The first tensile modulus ranges from 0.05 to 50 MPa; and / or the second tensile modulus ranges from 1 to 1000 MPa.

4. The stretchable flexible circuit board according to claim 1, characterized in that: The first tensile modulus is in the range of 0.1 to 10 MPa; and / or the second tensile modulus is in the range of 1 to 100 MPa.

5. The stretchable flexible circuit board according to claim 1, characterized in that: The thickness of the first elastic body ranges from 0.03 to 2 mm; and / or the thickness of the second elastic body ranges from 0.1 to 10 mm.

6. The stretchable flexible circuit board according to claim 1, characterized in that: The thickness of the first elastic body is in the range of 0.2 to 1 mm; and / or the thickness of the second elastic body is in the range of 1 to 3 mm.

7. The stretchable flexible circuit board according to claim 1, characterized in that: The first elastic body has a first elongation at break, and the first elongation at break ranges from 100 to 2000%.

8. The stretchable flexible circuit board according to claim 7, characterized in that: The first elongation at break ranges from 300 to 1000%.

9. The stretchable flexible circuit board according to claim 1, characterized in that: The second elastic body has a second elongation at break, and the second elongation at break ranges from 50 to 1000%.

10. The stretchable flexible circuit board according to claim 9, characterized in that: The second elongation at break ranges from 100 to 500%.

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