Pressing method of vehicle-mounted thick copper FPC (Flexible Printed Circuit)

Abstract

According to the lamination method of the vehicle-mounted thick copper FPC provided by the invention, the TPX glue blocking film is matched with the vacuum false pressure, so that the FCCL layer with large thickness can be matched with the adhesive with small thickness for use, the limitation of the total board thickness is met, bubbles are discharged, and the layering of a base material is avoided; the ratio of the thickness of the bonding glue to the thickness of the FCCL layer of the bonding glue contact binding surface reaches 1: 1.6; and the matching capability of the thicker FCCL layer and the thinner adhesive glue is effectively provided.

Description

Technical Field

[0001] This invention relates to the field of FPC technology, and in particular to a method for laminating automotive-grade thick copper FPCs. Background Technology

[0002] Thick copper FPC refers to flexible printed circuit boards with copper foil thickness of 35μm-40μm. Compared with ordinary FPC (copper thickness is usually 12-35μm), its core features include: high current carrying capacity, excellent heat dissipation, improved mechanical strength, and high temperature resistance.

[0003] In thick copper FPCs, the ratio of FCCL layer thickness to adhesive thickness is generally 1:1. Due to the limitation of the total board thickness, a thicker FCCL layer needs to be used with a thinner adhesive. For example, an FCCL layer with a thickness of 35μm-40μm can only be used with 25μm adhesive. This will result in an adhesive-to-copper ratio that is significantly lower than 1:1 (the adhesive-to-copper ratio refers to the ratio of adhesive thickness to copper layer thickness). During the lamination process, insufficient adhesive filling will cause air bubbles to form between the FCCL layer and the adhesive, which will lead to substrate delamination.

[0004] For example, a patent document with Chinese application number 202411908338.7 and publication date of 2025.11.18 discloses a method for manufacturing a wireless charging FPC. This method discloses a method of vacuum sham pressing on the protective film to overcome the occurrence of bubble defects.

[0005] However, this method first applies vacuum pressure to the protective film, and then presses the vacuum-pressed protective film onto the FPC. Since the protective film and FPC are not vacuum-pressed during the stacking process, it is difficult to remove air bubbles between the stacked substrates and between the circuits. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a lamination method for automotive thick copper FPC, which solves the problems of air bubbles and delamination by using TPX resist film and vacuum sham pressure, so that the thick FCCL layer can be matched with the thin adhesive, effectively improving the adhesive-copper ratio of the adhesive.

[0007] To solve the above-mentioned technical problems, the technical solution used in this invention is: a method for laminating automotive-grade thick copper FPCs, comprising the following steps:

[0008] S1. Apply an adhesive layer to one surface of the double-sided substrate.

[0009] S2. Apply a TPX resist film to the surface of the adhesive layer and the other surface of the double-sided substrate, and perform vacuum dummy pressure.

[0010] S3. Remove the TPX resist film.

[0011] S4. After vacuum squeezing, a single-sided substrate is bonded to the surface of the adhesive layer and pressed together to form an FPC.

[0012] Preferably, in S4, a press is used to press the single-sided substrate, the adhesive layer, and the double-sided substrate together.

[0013] Preferably, the pressure transmission machine adopts segmented control. The pressure of the pressure transmission machine first increases and then remains for a period of time before gradually decreasing. The temperature of the pressure transmission machine first gradually increases and then remains for a period of time before gradually decreasing.

[0014] Preferably, the segmented control includes a first pressing stage, a second pressing stage, a third pressing stage, and a fourth pressing stage.

[0015] In the first pressing stage, the temperature is gradually increased to the temperature set value required for the second pressing stage, and then kept constant. In the second pressing stage, the temperature is gradually decreased to the temperature set value required for the third pressing stage, and then kept constant. In the third pressing stage, the temperature is gradually decreased to the temperature set value required for the fourth pressing stage, and then kept constant. This process continues until pressing is complete.

[0016] Preferably, in the first pressing stage, the pressure is gradually increased to the pressure setting value required for the second pressing stage; then, from the second pressing stage to the fourth pressing stage, the current pressure value is maintained; in the fourth pressing stage, the pressure is gradually decreased to the pressure setting value required for the fifth pressing stage; until the pressing is completed.

[0017] Preferably, the thickness of the TPX resist film is ≥120μm.

[0018] Preferably, in step S2, a vacuum press is used for vacuum pre-pressing, with a temperature range of 110±5℃; the pre-pressing time is 10-15 seconds, the forming time is 10-15 seconds, and the pressure is 15±2 kgf / cm². 2 .

[0019] Compared with the prior art, the beneficial effects of the bonding method for automotive thick copper FPC described in this invention are mainly reflected in the following aspects: the TPX resist film softens under the high temperature of vacuum sham pressure, and the softened TPX resist film uniformly covers the surface of the adhesive layer, fully expelling large air bubbles between the lines; by bonding the double-sided substrate, adhesive layer, and single-sided substrate after lamination into an FPC, small air bubbles between the lines are further expelled, thereby achieving complete elimination of air bubbles.

[0020] By combining TPX adhesive barrier film with vacuum dummy pressure, a thicker FCCL layer can be matched with a thinner adhesive, thereby meeting the total board thickness limit while expelling air bubbles and preventing substrate delamination. This achieves a 1:1.6 ratio between the adhesive thickness and the FCCL layer thickness on the adhesive contact surface, effectively providing the ability to match a thicker FCCL layer with a thinner adhesive.

[0021] The double-sided substrate, adhesive, and single-sided substrate are pressed together by a press to ensure uniform heating of the substrate surface, reduce the internal stress of the temperature guide pillars, and the uniform pressure allows the adhesive between the double-sided and single-sided substrates to flow fully and fill the gaps between the circuits, thereby improving the interlayer bonding force.

[0022] By employing multi-stage heating / cooling curves and pressure regulation, the system adapts to differences in the thermal expansion coefficients of materials, thereby improving dimensional stability. Simultaneously, temperature control involves gradually increasing the temperature at different pressing stages, followed by multiple gradual coolings to the set temperature. This prevents rapid cooling from causing substrate shrinkage and wrinkles.

[0023] The temperature range of the vacuum press is set to 110±5℃; it can meet the TG point temperature requirements of different adhesives and has a wide range of applications; the pre-pressing time and molding time of the vacuum press are set to a range of 10-15S, which can shorten the pre-pressing and molding time while meeting the requirements of false pressure degassing, thus avoiding wasted production capacity.

[0024] The present invention discloses a method for laminating thick copper FPC for automotive applications. By using TPX resist film and vacuum sham pressing, the problems of air bubbles and delamination are solved, enabling the use of thick FCCL layers with thin adhesives. Attached Figure Description

[0025] The above and other objects, features, and advantages of the invention will become clearer through a more detailed description of the preferred embodiments illustrated in the accompanying drawings. The same reference numerals denote the same parts throughout the drawings, and the drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the gist of the invention.

[0026] Figure 1 This is a schematic diagram of the structure of the FPC of the present invention.

[0027] Figure 2 This is a composite diagram of the double-sided substrate and adhesive layer subjected to vacuum sham pressing according to the present invention.

[0028] Figure 3 This is a schematic diagram of the FPC being laminated and stacked according to the present invention.

[0029] Explanation of reference numerals: FPC1, single-sided substrate 11, adhesive layer 12, double-sided substrate 13, TPX adhesive barrier film 14, double-sided substrate 13, FCCL layer 15, PI layer 16, adhesive release paper layer 17, three-in-one pressing structure 2, press airbag 3, press steel plate 4. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention. In this embodiment, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0031] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to and integrated with the other element, or there may be an intervening element present. The terms "mounted," "one end," "the other end," and similar expressions used in this invention are for illustrative purposes only.

[0032] like Figure 1-2 As shown, a vehicle-mounted thick copper FPC includes a single-sided substrate 11, an adhesive layer 12, and a double-sided substrate 13 stacked sequentially.

[0033] The single-sided substrate 11 includes an FCCL layer 15 (flexible copper clad laminate) and a PI layer 16 located below the FCCL layer 15; the double-sided substrate 13 includes two FCCL layers 15 and a PI layer 16 located between the two FCCL layers 15.

[0034] The initial bonding of the adhesive layer 12 and the double-sided substrate 13 is achieved through a combination of TPX adhesive barrier film and vacuum dummy pressure. An adhesive release paper layer 17 is provided on the surface of the adhesive layer 12 away from the double-sided substrate 13, and the TPX adhesive barrier film is disposed on the surface of the adhesive release paper layer 17. After the initial bonding of the adhesive layer 12 and the double-sided substrate 13, the TPX adhesive barrier film and the adhesive release paper layer 17 are removed. Then, a single-sided substrate 11 is placed on the surface of the adhesive layer 12 away from the double-sided substrate 13, and the single-sided substrate 11, the adhesive layer 12, and the double-sided substrate 13 are bonded together by a press.

[0035] In a preferred embodiment, the thickness of the TPX resist film 14 is ≥120μm.

[0036] A method for laminating thick copper FPCs for automotive applications includes the following steps:

[0037] S1. Adhesive layer 12 is bonded to one surface of double-sided substrate 13.

[0038] S2. A TPX resist film 14 is placed on the surface of the adhesive layer 12 and the other surface of the double-sided substrate 13 and vacuum pressure is applied.

[0039] In this embodiment, a vacuum press is used for vacuum pre-pressing. The temperature range of the vacuum press is 110±5℃; the pre-pressing time is 10-15 seconds; the forming time is 10-15 seconds; and the pressure is 15±2 kgf / cm². 2 The temperature range of the vacuum press is set to 110±5℃; it can meet the TG point temperature requirements of different adhesives and has a wide range of applications; the pre-pressing time and molding time of the vacuum press are set to a range of 10-15S, which shortens the pre-pressing and molding time while meeting the requirements of false pressure degassing, thus avoiding wasted production capacity.

[0040] Reference Figure 2 As shown, an adhesive release paper layer 17 is provided on the surface of the adhesive layer 12 away from the double-sided substrate 13. A TPX adhesive barrier film 14 is disposed above the adhesive release paper layer 17, and another TPX adhesive barrier film 14 is disposed below the double-sided substrate 13. The stacked TPX adhesive barrier film 14, adhesive release paper layer 17, adhesive layer 12, double-sided substrate 13 and TPX adhesive barrier film 14 are placed between the press air bladder 3 and the press steel plate 4 of the vacuum press.

[0041] S3. Remove the TPX adhesive barrier film and adhesive release paper layer 17.

[0042] S4. A single-sided substrate is bonded to the surface of the adhesive layer after vacuum sham pressing. The single-sided substrate, adhesive layer 12 and double-sided substrate are pressed together to form an FPC.

[0043] In this embodiment, a press is used to press the single-sided substrate 11, the adhesive layer 12, and the double-sided substrate 13 together. The press adopts segmented control; the pressure of the press first increases, then is maintained for a period of time, and finally gradually decreases; the temperature of the press first gradually increases, then is maintained for a period of time, and finally gradually decreases.

[0044] The double-sided substrate 13, adhesive layer 12, and single-sided substrate 11 are pressed together by a press to ensure that the substrate board is heated evenly, reduce the internal stress of the temperature guide post, and the uniform pressure allows the adhesive between the double-sided substrate 13 and the single-sided substrate 11 to flow fully and fill the gaps between the circuits, thereby improving the interlayer bonding force.

[0045] By employing multi-stage heating / cooling curves and pressure regulation, the system adapts to differences in the thermal expansion coefficients of materials, thereby improving dimensional stability. Simultaneously, temperature control involves gradually increasing the temperature at different pressing stages, followed by multiple gradual coolings to the set temperature. This prevents rapid cooling from causing substrate shrinkage and wrinkles.

[0046] In a preferred embodiment, a two-three-in-one pressing structure 1 is provided on the press machine, and the FPC is placed in the two-three-in-one pressing structure 1 for pressing. The three-in-one pressing structure 1 is a composite material including a release film, a buffer pad, and a heating plate.

[0047] In the above method, the TPX resist film 14 is softened under high temperature of vacuum pressure. The softened TPX resist film 14 is uniformly covered on the surface of the adhesive layer 12, and large air bubbles between the lines are fully discharged. The spaces between the lines are the spaces between conductive lines (copper foil).

[0048] By pressing the double-sided substrate 13, adhesive layer 12, and single-sided substrate 11 together to form an FPC, small air bubbles between the circuits are further removed, thus achieving complete elimination of air bubbles.

[0049] By combining the TPX resist film 14 with vacuum dummy pressure, a thicker FCCL layer can be matched with a thinner adhesive, thereby meeting the total board thickness limit while expelling air bubbles and preventing substrate delamination. This achieves a 1:1.6 ratio between the adhesive thickness and the copper thickness of the FCCL layer on the adhesive contact surface, effectively improving the compatibility between a thicker FCCL layer and a thinner adhesive.

[0050] The aforementioned segmented control includes a first pressing stage, a second pressing stage, a third pressing stage, and a fourth pressing stage.

[0051] Table 1 shows the pressing parameters of the press.

[0052]

[0053] Table 1

[0054] In the first pressing stage, the temperature is gradually increased to the temperature set value required for the second pressing stage, and then kept constant. In the second pressing stage, the temperature is gradually decreased to the temperature set value required for the third pressing stage, and then kept constant. In the third pressing stage, the temperature is gradually decreased to the temperature set value required for the fourth pressing stage, and then kept constant. This process continues until pressing is complete.

[0055] In the first pressing stage, gradually increase the pressure to the pressure set value required for the second pressing stage. Then, maintain the current pressure value from the second to the fourth pressing stage. In the fourth pressing stage, gradually decrease the pressure to the pressure set value required for the fifth pressing stage; until pressing is complete. The maximum pressure is 900 psi, the maximum temperature is 190°C, and the high-temperature and high-pressure holding time is 120 minutes. Pressing under high pressure and high temperature conditions effectively vents air between the lines, ensuring the adhesive adheres effectively to the lines and further removing air bubbles.

[0056] Specifically, referring to Table 1, the slope represents the time it takes for a pressure setpoint to change to the next pressure setpoint, and for a temperature setpoint to change to the next pressure setpoint. The pressure setpoint for the first pressing stage is the initial pressure setpoint, and the temperature setpoint for the first pressing stage is the initial temperature setpoint.

[0057] The pressure setting for the first pressing stage is 100 psi, and the temperature setting is 45°C. Maintain these settings for 1 minute.

[0058] After the first pressing stage, gradually increase the current pressure setting from 100 psi to 900 psi and the current temperature setting from 45°C to 190°C within 30 minutes. Proceed to the second pressing stage and maintain the current parameters for 120 minutes.

[0059] After the second pressing stage, maintain the pressure setpoint at 900 psi and gradually reduce the current temperature setpoint from 190°C to 130°C over 15 minutes. Proceed to the third pressing stage and maintain the current parameters for 10 minutes.

[0060] After the third pressing stage, maintain the pressure setpoint at 900 psi and gradually reduce the current temperature setpoint from 130°C to 45°C over 15 minutes. Proceed to the fourth pressing stage and maintain the current parameters for 10 minutes.

[0061] After the fourth pressing stage, gradually reduce the current pressure setting from 900 psi to 100 psi within 1 minute, and gradually reduce the current temperature setting from 45°C to 40°C. Proceed to the fifth pressing stage and maintain the current parameters for 1 minute; pressing is complete.

[0062] In this specification, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0063] In the description of this specification, the references to terms such as "preferred embodiment," "another embodiment," "other embodiment," or "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for laminating a thick copper FPC for automotive applications, characterized in that: Includes the following steps: S1. Apply an adhesive layer to one surface of a double-sided substrate; S2. Apply a TPX adhesive barrier film to the surface of the adhesive layer and the other surface of the double-sided substrate and perform vacuum sham pressure. S3. Remove the TPX resist film; S4. A single-sided substrate is bonded to the surface of the adhesive layer after vacuum sham pressing. The single-sided substrate, adhesive layer and double-sided substrate are pressed together to form an FPC.

2. The lamination method for automotive-grade thick copper FPC according to claim 1, characterized in that: The S4 uses a press to press together a single-sided substrate, an adhesive layer, and a double-sided substrate.

3. The lamination method for automotive-grade thick copper FPC according to claim 2, characterized in that: The pressure transmission machine adopts segmented control. The pressure of the pressure transmission machine first increases, then remains for a period of time, and finally gradually decreases. The temperature of the pressure transmission machine first gradually increases, then remains for a period of time, and finally gradually decreases.

4. The lamination method for automotive-grade thick copper FPC according to claim 3, characterized in that: The segmented control includes a first pressing stage, a second pressing stage, a third pressing stage, and a fourth pressing stage; In the first pressing stage, the temperature is gradually increased to the temperature set value required for the second pressing stage, and then kept constant. In the second pressing stage, the temperature is gradually decreased to the temperature set value required for the third pressing stage, and then kept constant. In the third pressing stage, the temperature is gradually decreased to the temperature set value required for the fourth pressing stage, and then kept constant. This process continues until pressing is complete.

5. The lamination method for automotive-grade thick copper FPC according to claim 4, characterized in that: In the first pressing stage, gradually increase the pressure to the pressure setting value required for the second pressing stage; then, from the second pressing stage to the fourth pressing stage, maintain the current pressure value; in the fourth pressing stage, gradually decrease the pressure to the pressure setting value required for the fifth pressing stage; until pressing is completed.

6. The lamination method for automotive-grade thick copper FPC according to claim 1, characterized in that: The thickness of the TPX resist film is ≥120μm.

7. The lamination method for automotive-grade thick copper FPC according to claim 1, characterized in that: In step S2, a vacuum press is used for vacuum pre-pressing. The temperature range of the vacuum press is 110±5℃; the pre-pressing time is 10-15 seconds, the forming time is 10-15 seconds, and the pressure is 15±2 kgf / cm². 2 .

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