A design and protection method for rigid-flex printed cables

Abstract

This invention relates to a design and protection method for rigid-flex printed cables, comprising an electrical connector 10, a rigid-flex printed circuit board, and a sealing adhesive. The method includes the following steps: Step 1: Selecting the electrical connector for the rigid-flex printed cable, determining the type of electrical connector. The selection includes series selection, core count selection, mating type selection, locking accessory selection, pin length selection, and quality grade selection. This invention is particularly suitable for applications in products with limited space, weight, and stringent environmental requirements.

Description

Technical Field

[0001] This invention belongs to the field of rigid-flex printed cable technology, specifically a design and protection method for rigid-flex printed cables. Background Technology

[0002] Cables serve as channels for electrical signal transmission. Traditional cable designs use electrical connectors to connect wires via crimping or soldering, but this method is heavy and difficult to assemble manually. Current solutions utilize rigid-flex printed circuit boards (PCBs) instead of traditional cables for signal transmission. This reduces cable network weight; however, the electrical, structural, mechanical, and thermal protection methods for rigid-flex PCBs differ from those of traditional cables and the design methods used for rigid-flex PCBs in equipment. Therefore, this invention provides a design and protection method for rigid-flex PCBs to achieve reliable electrical signal transmission. Summary of the Invention

[0003] The present invention aims to provide a design and protection method for rigid-flex printed cables, which is applicable to electrical interconnection with clear weight reduction requirements, and realizes the electrical, structural design and mechanical and thermal protection of rigid-flex printed cables.

[0004] A design and protection method for a rigid-flex printed cable, the rigid-flex printed cable comprising an electrical connector 10, a rigid-flex printed circuit board, and a sealing adhesive, characterized by comprising the following steps:

[0005] Step 1: Select the electrical connectors for the rigid-flex printed circuit cable and determine the type of electrical connector for the rigid-flex printed circuit cable. The selection of electrical connectors includes series selection, core count selection, mating type selection, locking accessory selection, pin length selection, and quality grade selection.

[0006] Step 2: Perform structural design of rigid-flex printed circuit boards:

[0007] a. Design and determine the appearance and shape of the rigid-flex printed circuit board; there are bending and intersecting branches on the rigid-flex printed circuit board 7;

[0008] b. Rigid-flex printed circuit boards include rigid plates and flexible plates; a rigid-flex printed circuit board has a rigid plate A111 connected to one end of a flexible plate A4 and a rigid plate C112 connected to the other end of the flexible plate A4, wherein the flexible plate A4 is a three-dimensional shape that is either in a plane or not in a plane.

[0009] c. The flexible sheet A4 has a bending and intersecting branch 7, including a rigid sheet B113 and a flexible sheet B41 at the branch. One end of the flexible sheet B41 at the branch is connected to the flexible sheet A4 as needed, and the other end of the flexible sheet B41 at the branch is connected to the rigid sheet B113 at the branch. The flexible sheet B41 at the branch has a three-dimensional shape that is either in a plane or not in a plane. Multiple branches can be connected on the flexible sheet A4.

[0010] d. Design determines the dimensions and appearance of the rigid-flex printed circuit board;

[0011] Step 3: Perform electrical design for rigid-flex printed circuit boards, including electrical connection design and PCB routing design, where PCB routing design includes on-resistance design and current carrying capacity design.

[0012] Step 4: Perform rigid-flex printed circuit board mechanical reinforcement design: including,

[0013] a. Design fixed lugs 5 on the main flexible sheet or branch flexible sheet;

[0014] b. Add tear-resistant line 6. Tear-resistant line 6 is provided at the edge connection between the fixed support lug 5 and the main flexible plate or branch flexible plate. Tear-resistant line 6 is provided at the edge connection of the main flexible plate that can connect to multiple branch flexible plates.

[0015] Step 5: Perform thermal protection design for rigid-flex printed circuit boards: Wrap the part of the rigid-flex printed circuit board except for the fixed lug 5 with heat-resistant cloth 8, with 1 / 2 overlap and two layers wrapped, and fix it with tape 9 at the branch of the rigid-flex printed cable.

[0016] Step 6: Perform insulation design for rigid-flex printed cables: Use sealing adhesive to seal the solder joints between the main rigid plate and branch rigid plate of the rigid-flex printed circuit board and the electrical connector to ensure the insulation performance of the product.

[0017] The steps in Step 1, connector selection, include series selection, number of cores selection, mating type selection, locking accessory selection, pin length selection, and quality grade selection. The specific selection principles are as follows:

[0018] a. Series selection: Select based on the characteristics of the transmitted electrical signal, the rated current of the electrical connector, and the product size. Generally, micro rectangular connectors are selected.

[0019] b. Number of cores selection: Select according to the number of electrical signals to be transmitted, generally 5 cores to 100 cores;

[0020] c. Selection of plug type: There are two types of plug type: straight plug and right-angle plug. The choice is mainly based on the surrounding structural environment and wiring of the electrical connector. If there are no restrictions, the plug type should be selected according to the principle of the smoothest wiring direction. For electrical connectors with 10 pins and 101 arranged in 3 rows, the right-angle plug type should be selected as much as possible to facilitate the subsequent electrical PCB wiring design.

[0021] d. Locking accessory selection: The selection of locking accessories should consider two aspects: first, the locking of the connector at the device end, and second, the thickness of the rigid plate;

[0022] e. Pin length selection: The pin length selection depends on the thickness of the rigid plate, and is generally 0.7mm to 1.5mm thicker than the rigid plate;

[0023] f. Quality grade selection: The selection is based on the usage environment of the rigid-flex printed cable. Generally, industrial grade, military grade, and aerospace grade are selected.

[0024] The PCB routing design in step two includes on-resistance design and current carrying capacity design, and the specific design methods are as follows:

[0025] a. On-resistance design: The on-resistance of the circuit is calculated according to the conductor resistance calculation formula, as follows.

[0026] R=ρL / S(1)

[0027] S=Wt(2)

[0028] In the formula: R—resistance of the wire, Ω;

[0029] L—Wire length, mm;

[0030] W – Width of conductor, mm;

[0031] ρ = 1.8 × 10 -5 Ω·mm;

[0032] t — conductor thickness, mm.

[0033] b. Current carrying capacity design: The current carrying capacity is determined by the cross-sectional area of ​​the conductor. The current carrying capacity design is carried out according to the current carrying capacity formula, as follows.

[0034] I = K × T 0.44 ×A 0.75 (3)

[0035] In the formula:

[0036] I is the correction factor, which is 0.024 for the inner layer and 0.048 for the outer layer;

[0037] T represents the temperature rise;

[0038] A is the cross-sectional area of ​​the conductor, in mils. 2 ;

[0039] Finally, the trace width of the PCB routing is taken as the maximum value calculated from both methods;

[0040] The tear-resistant line 6 mentioned in step four is an arc-shaped copper wire.

[0041] The heat-resistant cloth 8 mentioned in step five has a thickness of ≥0.3mm, and 3M tape is used, with heat-resistant adhesive applied for protection and fixation.

[0042] Step six involves using a sealing adhesive to seal the solder joints between the main rigid plate and branch rigid plate of the rigid-flex printed circuit board and the electrical connector, wherein the sealing adhesive is polyurethane adhesive.

[0043] Compared with the prior art, the present invention has the following beneficial technical effects:

[0044] (1) The rigid-flex printed cable of the present invention is composed of a rigid-flex printed circuit board and an electrical connector by means of pin soldering. Due to its great advantage of being thin and light, rigid-flex printed cables are gradually being used in the aerospace field.

[0045] (2) The technical solution of this invention has a reliable structure and can withstand a high impact of 6000g. The technical solution can withstand a high temperature of 350℃ (50s). The technical solution can greatly reduce the weight of electrical systems. Compared with traditional cables, rigid-flex printed cables reduce weight and volume by more than 50%. This invention is particularly suitable for applications in products with limited space and strict weight and environmental requirements. Attached Figure Description

[0046] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0047] Figure 1 This is a flowchart of the rigid-flex printed cable design and protection method of the present invention;

[0048] Figure 2 This is a schematic diagram of the mechanical reinforcement design of the rigid-flex printed cable design and protection method of the present invention;

[0049] Figure 3 This is a schematic diagram of the partial electrical connector type in the rigid-flex printed cable design and protection method of the present invention;

[0050] Figure 4 This is a schematic diagram of the partial sealing design of the rigid-flex printed cable design and protection method of the present invention;

[0051] Figure 5This is a schematic diagram of the local thermal protection design of the rigid-flex printed cable design and protection method of the present invention;

[0052] Figure 6 This is an embodiment of the present invention.

[0053] Figure label:

[0054] Among them, 2-rigid-flexible joint plate, 3-signal line, 4-flexible plate A, 5-fixed support lug, 6-tear-resistant line, 7-branch, 8-heatproof cloth, 9-tape, 10-electrical connector, 11-colloid, 101-pin, 111-rigid plate A, 112-rigid plate C, 113-rigid part B. Detailed Implementation

[0055] Rigid-flex printed circuit boards (PCBs) consist of electrical connectors, a rigid-flex PCB, and a sealant. The rigid-flex PCB comprises a rigid section and a flexible section. The working principle involves soldering the electrical connector to the rigid section of the PCB, with the sealant acting on the solder joints. The electrical connector connects various devices, interlocking and locking with the connectors of each device for reliable signal transmission. The rigid-flex PCB enables long-distance flexible signal transmission; the rigid section is used for reliable soldering with the electrical connector, while the flexible section facilitates long-distance flexible signal transmission and bending. The sealant protects the solder joints, improves the product's insulation performance, and enhances the rigid-flex PCB's mechanical resistance.

[0056] The present invention is achieved through the following technical solutions.

[0057] Step 1: Perform structural design of rigid-flex printed cables and determine the appearance shape of rigid-flex printed cables, including rigid-flex printed circuit boards and sealing adhesives. The rigid-flex printed circuit boards include rigid and flexible parts.

[0058] Step 2: Select the electrical connectors for the rigid-flex printed cable and determine the type of electrical connector for the rigid-flex printed cable.

[0059] Furthermore, the selection of electrical connectors includes series selection, number of cores selection, mating type selection, locking accessory selection, pin length selection, and quality grade selection. The specific selection principles are as follows:

[0060] (1) Series selection: Select according to the characteristics of the transmitted electrical signal, the rated current of the electrical connector and the product size. Generally, micro rectangular connectors are selected.

[0061] (2) Number of cores: Select according to the number of electrical signals to be transmitted. Generally, the number of cores is 5 to 100.

[0062] (3) Selection of plug type: There are two types of plug type: straight plug and bent plug. The choice is mainly determined by the surrounding structural environment and wiring of the electrical connector. If there are no restrictions, the plug type should be selected based on the principle of the smoothest wiring direction. For connectors with 3 rows of pins, the bent plug type should be selected as much as possible to facilitate the subsequent electrical PCB wiring design.

[0063] (3) Selection of locking accessories: The selection of locking accessories should consider two aspects: first, the locking of the connector at the device end, and second, the thickness of the rigid plate.

[0064] (4) Selection of pin length: The selection of pin length depends on the thickness of the rigid plate, and is generally 0.7mm to 1.5mm thicker than the rigid plate.

[0065] (5) Quality grade selection: The selection is based on the usage environment of the rigid-flex printed cable. Generally, industrial grade, military grade, and aerospace grade are selected.

[0066] Step 3: Perform electrical design for rigid-flex printed cables, including adding tear-resistant lines 6 at branch 7 and fixed lugs (5) for mechanical reinforcement.

[0067] Further, the electrical design of the rigid-flex printed cable is carried out, which mainly includes: electrical connection design and PCB routing design. The PCB routing design includes on-resistance design, current carrying capacity design and matching impedance design. The specific design methods are as follows.

[0068] (1) On-resistance design: The on-resistance of the line is calculated according to the formula for calculating conductor resistance, as follows.

[0069] R=ρL / S(1)

[0070] S=Wt(2)

[0071] In the formula: R—resistance of the wire, Ω;

[0072] L—Wire length, mm;

[0073] W – Width of conductor, mm;

[0074] ρ = 1.8 × 10 -5 Ω·mm;

[0075] t — conductor thickness, mm.

[0076] (2) Current carrying capacity design: The current carrying capacity is determined by the cross-sectional area of ​​the conductor. The current carrying capacity design is carried out according to the current carrying capacity formula, as follows.

[0077] I = K × T 0.44 ×A 0.75 (3)

[0078] In the formula:

[0079] I is the correction factor, which is 0.024 for the inner layer and 0.048 for the outer layer;

[0080] T represents the temperature rise;

[0081] A is the cross-sectional area of ​​the conductor, in mils. 2 .

[0082] Finally, the PCB trace width is taken as the maximum value calculated from both methods.

[0083] Step 4: Perform thermal protection design, wrap the rigid-flex printed cable with heat-resistant cloth (8), wrap two layers with a 1 / 2 overlap, and fix the rigid-flex printed cable branch with tape (9);

[0084] Step 5: Perform insulation design: Use sealing adhesive to seal the solder joints of the rigid-flex printed cable connector to ensure the insulation performance of the product.

[0085] The aforementioned rigid-flex printed cable design and protection method is characterized in that: the type of tear-resistant wire added at the branch and fixed support is arc-shaped copper wire.

[0086] The design and protection method for rigid-flex printed circuit cables is characterized in that: the thickness of the heat-resistant cloth is ≥0.3mm, 3M tape is selected, and heat-resistant adhesive is applied for protection and fixation.

[0087] The aforementioned rigid-flex printed cable design and protection method is characterized by using polyurethane adhesive to seal the solder joints of the rigid-flex printed cable connectors to ensure the insulation performance of the product.

[0088] To make the present invention, its technical solutions, and advantages clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0089] refer to Figures 1 to 5 The present invention discloses a design and protection method for rigid-flex printed cables, comprising: step S101, performing structural design of the rigid-flex printed cable; step S102, selecting electrical connectors for the rigid-flex printed cable and determining the type of electrical connectors for the rigid-flex printed cable; step S103, performing electrical design of the rigid-flex printed cable, including adding tear-resistant threads for mechanical reinforcement at branch points and fixed lugs; and step S104, performing thermal protection design by wrapping the rigid-flex printed cable with heat-resistant cloth, with two layers overlapping by 1 / 2, and fixing it with tape at the branch points of the rigid-flex printed cable.

[0090] In one embodiment, the rigid-flex printed cable has the following shape: Figure 2As shown, it includes rigid parts (111, 112, 113), and the electrical connector 10 is welded to the rigid part 111 via pins 101; the flexible part 4 includes a fixed support lug 5 and a branch 7.

[0091] In one embodiment, the electrical connector (10) of the rigid-flex printed cable is of type MDM1-37SNL7.

[0092] In one embodiment, the PCB wiring design of the rigid-flex printed cable includes signal lines 3 and tear-resistant lines 6 added at branch points 7 and fixed lug points 5, that is, adding arc-shaped copper foil lines 6 at mechanically weak points to enhance local stress resistance. The width of the arc-shaped copper foil lines is 0.25mm.

[0093] Specifically, if the resistance R of signal line 3 is <1Ω, the current carrying capacity I is >2A, the temperature rise is no more than 20℃, the wire length L = 500mm, the wire thickness t = 0.035mm, and the PCB wiring is on the outer layer K of 0.048, according to formulas (1) and (2), the wire width W should be >0.257mm. According to formula (3), the wire width W should be >0.508mm. The maximum value of the two should be taken. Therefore, the signal line wiring width is 0.6mm.

[0094] In one embodiment, the thermal protection method for the rigid-flex printed cable involves wrapping the rigid-flex printed cable with 0.3mm thick silicone-based heat-resistant cloth 8, with two layers overlapping by 1 / 2, and fixing it with 3M tape 9 at the branch points of the rigid-flex printed cable, and then applying heat-resistant adhesive for protection and fixation.

[0095] In one embodiment, the thermal protection method for the rigid-flex printed cable uses RB283-01 polyurethane adhesive 11 to seal the weld between the connector pin 101 and the rigid part A111 of the rigid-flex printed cable to ensure the insulation performance of the product.

Claims

1. A design and protection method for rigid-flex printed cables, comprising an electrical connector (10), a rigid-flex printed circuit board, and a sealing adhesive, characterized in that, Includes the following steps: Step 1: Select the electrical connectors for the rigid-flex printed circuit cable and determine the type of electrical connector for the rigid-flex printed circuit cable. The selection of electrical connectors includes series selection, core count selection, mating type selection, locking accessory selection, pin length selection, and quality grade selection. Step 2: Perform structural design of rigid-flex printed circuit boards: a. Design and determine the appearance shape of the rigid-flex printed circuit board; there are bending and intersecting branches on the rigid-flex printed circuit board (7); b. Rigid-flex printed circuit boards include rigid plates and flexible plates; a rigid-flex printed circuit board is a flexible plate A (4) with a rigid plate A (111) connected to one end and a rigid plate C (112) connected to the other end, wherein the flexible plate A (4) is a three-dimensional shape that is either in a plane or not in a plane. c. A branch (7) with bending and crossing is provided on the flexible plate A (4), including a rigid plate B (113) and a flexible plate B (41) at the branch. One end of the flexible plate B (41) at the branch is connected to the flexible plate A (4) as needed, and the other end of the flexible plate B (41) at the branch is connected to the rigid plate B (113). The flexible plate B (41) at the branch is a three-dimensional shape that is either in a plane or not in a plane. Multiple branches can be connected on the flexible plate A (4). d. Design determines the dimensions and appearance of the rigid-flex printed circuit board; Step 3: Perform electrical design for rigid-flex printed circuit boards, including electrical connection design and PCB routing design, where PCB routing design includes on-resistance design and current carrying capacity design. Step 4: Perform rigid-flex printed circuit board mechanical reinforcement design: including, a. Design fixed lugs on the main flexible sheet or branch flexible sheet (5) b. Add tear-resistant line (6), tear-resistant line (6) is provided at the edge connection between the fixed support lug (5) and the main flexible plate or branch flexible plate, and tear-resistant line (6) is provided at the edge connection of the main flexible plate that can connect multiple branch flexible plates. Step 5: Perform thermal protection design for rigid-flex printed circuit boards: Wrap the part of the rigid-flex printed circuit board except for the fixed lugs (5) with heat-resistant cloth (8), with a 1 / 2 overlap of two layers, and wrap and fix it with tape (9) at the branch of the rigid-flex printed cable. Step 6: Perform insulation design for rigid-flex printed cables: Use sealing adhesive to seal the solder joints between the main rigid plate and branch rigid plate of the rigid-flex printed circuit board and the electrical connector to ensure the insulation performance of the product.

2. The design and protection method for rigid-flex printed circuit cables according to claim 1, characterized in that, The steps in Step 1, connector selection, include series selection, number of cores selection, mating type selection, locking accessory selection, pin length selection, and quality grade selection. The specific selection principles are as follows: a. Series selection: Select based on the characteristics of the transmitted electrical signal, the rated current of the electrical connector, and the product size. Generally, micro rectangular connectors are selected. b. Number of cores selection: Select according to the number of electrical signals to be transmitted, generally 5 cores to 100 cores; c. Selection of plug type: There are two types of plug type: straight plug and bent plug. The main selection is based on the surrounding structural environment and wiring of the electrical connector. If there are no restrictions, the plug type should be selected according to the principle of the smoothest wiring direction. For connectors (10) with 3 rows of pins (101), bent plug should be selected as much as possible to facilitate subsequent electrical PCB wiring design. d. Locking accessory selection: The selection of locking accessories should consider two aspects: first, the locking of the connector at the device end, and second, the thickness of the rigid plate; e. Pin length selection: The pin length selection depends on the thickness of the rigid plate, and is generally 0.7mm to 1.5mm thicker than the rigid plate; f. Quality grade selection: The selection is based on the usage environment of the rigid-flex printed cable. Generally, industrial grade, military grade, and aerospace grade are selected.

3. The method for designing and protecting rigid-flex printed cables according to claim 1, characterized in that, The PCB routing design in step two includes on-resistance design and current carrying capacity design, and the specific design methods are as follows: a. On-resistance design: The on-resistance of the circuit is calculated according to the conductor resistance calculation formula, as follows: R=ρL / S(1) S=Wt(2) In the formula: R—resistance of the wire, Ω; L—Wire length, mm; W – Width of conductor, mm; p=1.8×10 -5 Ohm mm; t — conductor thickness, mm; b. Current-carrying capacity design: The current-carrying capacity is determined by the cross-sectional area of ​​the conductor. The current-carrying capacity design is based on the following formula: I=K×T 0.44 ×A 0.75 (3) In the formula: I is the correction factor, which is 0.024 for the inner layer and 0.048 for the outer layer; T represents the temperature rise; A is the cross-sectional area of ​​the conductor, in mils. 2 ; Finally, the PCB trace width is taken as the maximum value calculated from both methods.

4. The design and protection method for rigid-flex printed cables according to claim 1, characterized in that, The tear-resistant line (6) added in step four is an arc-shaped copper wire.

5. The design and protection method for rigid-flex printed cables according to claim 1, characterized in that, The heat-resistant cloth (8) mentioned in step five has a thickness of ≥0.3mm. 3M tape is used, and heat-resistant adhesive is applied for protection and fixation.

6. The method for designing and protecting rigid-flex printed cables according to claim 1, characterized in that, Step six involves using a sealing adhesive to seal the solder joints between the main rigid plate and branch rigid plate of the rigid-flex printed circuit board and the electrical connector, wherein the sealing adhesive is polyurethane adhesive.

Images