Flexible pet copper plated film with gradient interface structure and manufacturing method thereof

Abstract

The present application relates to the technical field of functional composite film, and discloses a flexible PET copper-plated film with gradient interface structure and a manufacturing method thereof. The flexible PET copper-plated film comprises a PET substrate, a microstructure layer formed on at least one side surface of the PET substrate, a metal adhesion transition layer formed on the microstructure layer, and a copper functional layer formed on the metal adhesion transition layer. The cross-sectional profile of the microstructure layer is a continuous curve transition, and there is no sharp corner mutation between the top and the side wall. The metal adhesion transition layer comprises an adhesion sublayer arranged close to the PET substrate and a transition sublayer arranged close to the copper functional layer. The copper functional layer has a grain size difference structure along the thickness direction, and the grain size of the region close to the interface is smaller than that of the region close to the surface. The application also discloses a manufacturing method of the flexible PET copper-plated film, which comprises PET substrate treatment, microstructure layer formation, surface activation, metal adhesion transition layer deposition, copper functional layer stage-by-stage deposition, and optional low-temperature annealing treatment. Through the synergistic effect of interface topography design, interlayer transition design and copper layer organization regulation, the interface bonding state and the structural stability under thermal cycling and bending conditions can be improved.

Description

Technical Field

[0001] This invention relates to the field of functional composite film technology, and in particular to a flexible PET copper-plated film with a gradient interface structure for use in flexible circuits, flexible shielding structures and high-speed signal transmission structures, and its manufacturing method. Background Technology

[0002] PET film possesses good mechanical properties, electrical insulation, and dimensional stability, making it a common substrate in flexible electronic devices. Existing copper-plated PET films typically employ planar interfaces or simply roughened interfaces, with the copper layer relying primarily on physical adsorption and limited interfacial interactions with the PET substrate. Under repeated bending, thermal cycling, or long-term service conditions, existing structures are prone to problems such as peeling, crack propagation, interfacial delamination, and decreased conductivity. The applicant has found that these problems are related to the lack of controllable spatial morphology at the interface, insufficient interlayer transition, and a uniform microstructure of the copper layer. Summary of the Invention

[0003] Design objective: The purpose of this invention is to provide a flexible PET copper-plated film with a gradient interface structure and its manufacturing method, so as to improve the interfacial bonding state between PET and copper layer, structural stability under bending conditions and interfacial stability under thermal cycling conditions.

[0004] Design scheme: To achieve the above objectives, the present invention provides a flexible PET copper-plated film with a gradient interface structure, comprising a PET substrate, a microstructure layer formed on at least one surface of the PET substrate, a metal adhesion transition layer formed on the microstructure layer, and a copper functional layer formed on the metal adhesion transition layer.

[0005] The cross-sectional profile of the microstructure layer has a continuous curved transition, with no sharp abrupt changes between the top and the sidewalls; preferably, the microstructure height of the microstructure layer is 0.5 to 3 μm, and the microstructure spacing is 1 to 10 μm; more preferably, the microstructure unit is composed of multiple microstructure units with alternating protrusions or concave-convexities, and the cross-sectional profile of the microstructure unit is arc-shaped or approximately arc-shaped.

[0006] The metal adhesion transition layer includes an adhesion sublayer disposed near the PET substrate and a transition sublayer disposed near the copper functional layer; preferably, the adhesion sublayer contains Ti and / or Cr, and the transition sublayer contains Ni and / or Ni alloy; more preferably, the thickness of the adhesion sublayer is 5-20 nm, and the thickness of the transition sublayer is 20-80 nm.

[0007] The copper functional layer has a grain size difference structure along the thickness direction, and the grain size in the region near the interface is smaller than the grain size in the region near the surface; preferably, the total thickness of the copper functional layer is 1 to 10 μm; more preferably, the grain size in the region near the interface is 60 to 100 nm, and the grain size in the region near the surface is 250 to 400 nm; in some embodiments, the copper functional layer includes a fine-grained region near the interface and a relatively coarse-grained region near the surface along the thickness direction.

[0008] The present invention also provides a method for manufacturing the flexible PET copper-plated film, comprising the following steps: S1, cleaning and drying the PET substrate; S2, forming a microstructure layer on the surface of the PET substrate; S3, performing plasma activation treatment on the surface of the PET substrate with the microstructure layer; S4, depositing a metal adhesion transition layer on the surface of the activated microstructure layer; S5, performing staged pulse electroplating to deposit a copper functional layer on the surface of the metal adhesion transition layer, so as to obtain a copper functional layer in which the grain size in the region near the interface is smaller than the grain size in the region near the surface; S6, optionally, performing a low-temperature annealing treatment on the obtained structure.

[0009] Preferably, the microstructure layer is formed in step S2 by roller embossing or laser processing. Preferably, the plasma activation treatment in step S3 has a power of 50–300 W and a treatment time of 10–120 s. Preferably, the adhesion sublayer is formed first in step S4, followed by the transition sublayer.

[0010] Preferably, the pulse electroplating in step S5 includes a first stage of high current density deposition and a second stage of low current density deposition; more preferably, the current density in the first stage is 12 to 18 A / dm², and the current density in the second stage is 1.5 to 3 A / dm²; preferably, the total thickness of the copper functional layer formed in step S5 is 1 to 10 μm.

[0011] Preferably, the low-temperature annealing treatment in step S6 is performed at a temperature of 80–180°C for 5–60 min.

[0012] The beneficial effects of this invention are as follows: (1) By constructing a microstructure layer with a continuous curved transition profile on the PET surface, the interface spatial morphology can be improved, thereby improving the interface bonding state. (2) By setting a metal adhesion transition layer between PET and the copper layer, the transition relationship between the polymer-metal interface can be improved, and a continuous metal interface can be provided for the subsequent formation of the copper layer. (3) By forming a grain size difference structure along the thickness direction inside the copper functional layer, the structural stability under bending conditions and thermal cycling conditions can be improved. (4) The above effects are based on the comparison results of the embodiments and comparative examples in this specification under the same test conditions. Attached Figure Description

[0013] Figure 1 This is a schematic flowchart of one embodiment of the flexible PET copper-plated film manufacturing method of the present invention.

[0014] Figure 2 This is a schematic diagram of the microstructure layer on the PET surface in this invention.

[0015] Figure 3 This is a partial cross-sectional schematic diagram of the flexible PET copper-plated film layer structure in this invention.

[0016] Figure 4 This is a schematic diagram of one embodiment of the copper functional layer with different grain sizes along the thickness direction in this invention.

[0017] Figure 5 This is a schematic diagram comparing the peeling paths of the structure of the present invention and the planar interface structure.

[0018] In the attached figures: 1 is the copper functional layer; 11 is the relatively coarse-grained region; 12 is the transition grain region; 13 is the fine-grained region; 2 is the metal adhesion transition layer; 21 is the transition sublayer; 22 is the adhesion sublayer; 3 is the PET substrate; 4 is the microstructure layer; h is the microstructure height; p is the microstructure spacing. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments. Unless otherwise stated, the thickness, dimensions, current density, temperature and time parameters in this specification are all directly measured using conventional testing or process equipment in the art.

[0020] In this specification, "microstructure layer" refers to an interface morphology layer composed of multiple microstructure units formed on the surface of PET; the cross-sectional profile of the microstructure unit has a continuous curve transition, with no sharp abrupt changes between the top and the sidewall.

[0021] In this specification, "interface region" refers to the area of ​​the copper functional layer near the metal adhesion transition layer; "surface region" refers to the area of ​​the copper functional layer near the outer surface.

[0022] In this specification, "grain size difference structure" refers to the presence of at least two different statistical scales of grain regions along the thickness direction of the copper functional layer, with the grain size of the region near the interface being smaller than that of the region near the surface.

[0023] In the embodiment shown in the accompanying drawings Figure 3The invention illustrates a layered structure of a flexible PET copper-plated film, which, from top to bottom, includes a copper functional layer 1, a transition sublayer 21, an adhesion sublayer 22, a microstructure layer 4, and a PET substrate 3, wherein the transition sublayer 21 and the adhesion sublayer 22 together constitute a metal adhesion transition layer 2. Figure 4 An embodiment of a grain size difference structure of copper functional layer 1 along the thickness direction is shown, which may include a relatively coarse grain region 11, a transition grain region 12 and a fine grain region 13 from near the outer surface to near the interface. Figure 5 The difference in the peeling path between the structure of the present invention and the planar interface comparative structure is shown. In the present invention, due to the presence of the microstructure layer 4, the peeling path extends along the undulating interface.

[0024] S1: PET substrate treatment. Select PET substrates with a thickness of 12–125 μm, and perform alkaline cleaning, deionized water rinsing, and drying under hot air conditions of 80–120℃.

[0025] S2: Forming a microstructure layer. The microstructure layer can be formed by die-printing or laser processing; preferably, the height of the microstructure is 0.8–2.5 μm and the spacing is 3–8 μm.

[0026] S3: Surface activation treatment. Plasma activation treatment is used, preferably with a power of 100-200 W and a treatment time of 30-60 s.

[0027] S4: Deposit a metal adhesion transition layer. Preferably, an adhesion sublayer is first formed on the activated microstructure layer by magnetron sputtering, followed by the formation of a transition sublayer; wherein the adhesion sublayer is a 5-15 nm Ti layer and / or Cr layer, and the transition sublayer is a 50-120 nm Ni layer or NiCr layer.

[0028] S5: Forming a copper functional layer. A pulse electroplating method is preferably used to deposit the copper functional layer; in the initial deposition stage, a current density of 12–18 A / dm² is used to form a fine-grained region near the interface, and in the later deposition stage, a current density of 1.5–3 A / dm² is used to form a relatively coarse-grained region near the surface, so that the grain size of the copper functional layer near the interface is 60–100 nm, and the grain size near the surface is 250–400 nm.

[0029] S6: Optional post-processing. After the copper functional layer is formed, a low-temperature annealing treatment of 80–180°C for 5–60 min can be performed; in some embodiments, the annealing temperature is 140–160°C and the time is 20–40 min.

[0030] (1) Peel strength: The 90° peel method was used, the strip width was 10 mm, the peel speed was 50 mm / min, the stable peel plateau value was recorded and converted into N / cm.

[0031] (2) Bending life: Bending radius 3 mm, repeated bending, failure is judged by the appearance of through crack.

[0032] (3) Thermal cycling stability: The interface is observed to have visible delamination after 100 cycles at temperatures ranging from -40℃ to 120℃.

[0033] (4) Surface resistance: Measured at 25℃ using the four-probe method, the unit is mΩ / sq.

[0034] (5) Residual stress: The residual stress in the copper layer was measured by XRD sin²ψ method, and the unit is MPa.

[0035] 1) The PET thickness is 25 μm.

[0036] 2) A microstructure layer is formed by die roller imprinting at a temperature of 130℃ and a pressure of 1.2 MPa. The microstructure height is 1.5 μm and the spacing is 5 μm.

[0037] 3) Plasma activation treatment was used, with a power of 150 W and a time of 60 s.

[0038] 4) A metal adhesion transition layer is formed by magnetron sputtering, wherein the Ti layer is 10 nm thick and the Ni layer is 80 nm thick.

[0039] 5) A copper functional layer was formed by pulse electroplating. The current density in the initial deposition stage was 15 A / dm², and the current density in the later deposition stage was 2 A / dm². The total thickness of the copper layer was 2 μm. The grain size in the region near the interface was about 80 nm, and the grain size in the region near the surface was about 300 nm.

[0040] 6) Anneal at 150℃ for 30 min.

[0041] 7) When tested according to the test method described in this instruction manual, the peel strength is 3.1 N / cm; no through cracks appeared after 5000 cycles under a bending radius of 3 mm; no delamination was observed after 300 thermal cycles from -40℃ to 120℃.

[0042] 1) The microstructure layer is formed by laser processing with a laser power of 12 W, a scanning speed of 400 mm / s, and a microstructure height of 2.5 μm and a spacing of 3 μm.

[0043] 2) A Cr layer with a thickness of 15 nm was used as the adhesion sublayer; a NiCr layer with a thickness of 120 nm was used as the transition sublayer.

[0044] 3) A copper functional layer is formed by pulse electroplating. The current density in the initial deposition stage is 18 A / dm², and the current density in the later deposition stage is 1.5 A / dm². The grain size in the region near the interface is about 60 nm, and the grain size in the region near the surface is about 400 nm.

[0045] 4) When tested according to the test method described in this instruction manual, the peel strength is 3.6 N / cm; no through cracks appeared after 8000 cycles under a bending radius of 3 mm; no delamination was observed after 500 thermal cycles.

[0046] 1) The height of the microstructure layer is 0.8 μm and the spacing is 8 μm.

[0047] 2) The adhesion sublayer is a Ti layer with a thickness of 5 nm; the transition sublayer is a Ni layer with a thickness of 50 nm.

[0048] 3) The grain size in the region near the interface is about 100 nm, and the grain size in the region near the surface is about 250 nm.

[0049] 4) When tested according to the test method described in this instruction manual, the peel strength is 2.7 N / cm; no through cracks appeared after 5000 cycles under a bending radius of 3 mm.

[0050] 1) The PET surface remains flat and the microstructure layer is not formed. All other conditions are the same as in Example 1.

[0051] 2) Peel strength is 1.6 N / cm; cracks appear after 2000 cycles under a bending radius of 3 mm; delamination occurs after 150 thermal cycles.

[0052] 1) A microstructure layer is formed, and the metal adhesion transition layer is the same as in Example 1; the copper layer is deposited using a single current density of 3 A / dm², so that the grain size is basically uniform.

[0053] 2) Peel strength is 2.1 N / cm; cracks appear after 3000 cycles under a bending radius of 3 mm; local delamination occurs after 200 thermal cycles.

[0054] sample Peel strength (N / cm) Bending performance Thermal cycling performance Example 1 3.1 No through-cracks appeared after 5000 cycles. No stratification observed after 300 trials Example 2 3.6 No through-cracks appeared after 8000 cycles. No stratification observed after 500 trials Example 3 2.7 No through-cracks appeared after 5000 cycles. — Comparative Example 1 1.6 Cracks appeared 2000 times 150 instances of stratification Comparative Example 2 2.1 Cracks appeared 3000 times 200 local layerings As can be seen from Table 1, under the test conditions described in the embodiments of this specification, the embodiments of the present invention are superior to the comparative examples in terms of peel strength, flexural life and thermal cycling stability.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the scope of protection of the present invention. Equivalent substitutions or modifications made by those skilled in the art without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

Claims

1. A flexible PET copper-plated film with a gradient interface structure, characterized in that, include: PET substrate; A microstructure layer formed on at least one surface of the PET substrate; A metal adhesion transition layer formed on the microstructure layer; The microstructure layer has a continuous curved profile with no sharp abrupt changes between the top and sidewalls. The metal adhesion transition layer includes an adhesion sublayer disposed near the PET substrate and a transition sublayer disposed near the copper functional layer. The copper functional layer has a grain size difference structure along the thickness direction, and the grain size in the region near the interface is smaller than the grain size in the region near the surface.

2. The flexible PET copper-plated film with a gradient interface structure according to claim 1, characterized in that, The microstructure height of the microstructure layer is 0.5–3 μm, and the microstructure spacing is 1–10 μm.

3. The flexible PET copper-plated film with a gradient interface structure according to claim 1 or 2, characterized in that, The microstructure layer is composed of multiple microstructure units with alternating protrusions or concave-convex shapes, and the cross-sectional profile of the microstructure unit is arc-shaped or approximately arc-shaped.

4. The flexible PET copper-plated film with a gradient interface structure according to any one of claims 1 to 3, characterized in that, The adhesion sublayer comprises Ti and / or Cr, and the transition sublayer comprises Ni and / or a Ni alloy.

5. The flexible PET copper-plated film with a gradient interface structure according to claim 4, characterized in that, The thickness of the adhesion sublayer is 5–20 nm, and the thickness of the transition sublayer is 20–80 nm.

6. The flexible PET copper-plated film with a gradient interface structure according to any one of claims 1 to 5, characterized in that, The total thickness of the copper functional layer is 1–10 μm.

7. The flexible PET copper-plated film with a gradient interface structure according to any one of claims 1 to 6, characterized in that, The grain size in the copper functional layer near the interface is 60–100 nm, and the grain size in the region near the surface is 250–400 nm.

8. The flexible PET copper-plated film with a gradient interface structure according to any one of claims 1 to 7, characterized in that, The copper functional layer includes a fine-grained region near the interface and a relatively coarse-grained region near the surface along the thickness direction.

9. The flexible PET copper-plated film with a gradient interface structure according to any one of claims 1 to 8, characterized in that, The PET substrate is a flexible PET film with a thickness of 12–75 μm.

10. The flexible PET copper-plated film with a gradient interface structure according to any one of claims 1 to 9, characterized in that, The flexible PET copper-plated film is used in flexible circuits, flexible shielding structures, or high-speed signal transmission structures.

11. A method for manufacturing a flexible PET copper-plated film with a gradient interface structure as described in claim 1, characterized in that, The process includes the following steps: S1, cleaning and drying the PET substrate; S2, forming a microstructure layer on the surface of the PET substrate; S3, performing plasma activation treatment on the surface of the PET substrate with the microstructure layer formed. S4. Deposit a metal adhesion transition layer on the surface of the activated microstructure layer; S5. Deposit a copper functional layer on the surface of the metal adhesion transition layer in stages using pulse electroplating to obtain a copper functional layer in which the grain size in the region near the interface is smaller than the grain size in the region near the surface; S6. Optionally, perform low-temperature annealing treatment on the obtained structure.

12. The method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to claim 11, characterized in that, In step S2, the microstructure layer is formed by roller embossing.

13. The method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to claim 11, characterized in that, In step S2, the microstructure layer is formed using laser processing.

14. A method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to any one of claims 11 to 13, characterized in that, The power of the plasma activation treatment in step S3 is 50-300 W, and the treatment time is 10-120 s.

15. The method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to any one of claims 11 to 14, characterized in that, In step S4, the adhesion sublayer is formed first, and then the transition sublayer is formed.

16. The method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to claim 15, characterized in that, The thickness of the adhesion sublayer is 5–20 nm, and the thickness of the transition sublayer is 20–80 nm.

17. The method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to any one of claims 11 to 16, characterized in that, The pulse electroplating in step S5 includes a first stage of high current density deposition and a second stage of low current density deposition.

18. The method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to claim 17, characterized in that, The current density in the first stage is 12–18 A / dm², and the current density in the second stage is 1.5–3 A / dm².

19. A method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to any one of claims 11 to 18, characterized in that, The total thickness of the copper functional layer formed in step S5 is 1 to 10 μm.

20. A method for manufacturing a flexible PET copper-plated film with a gradient interface structure according to any one of claims 11 to 19, characterized in that, The low-temperature annealing treatment in step S6 is performed at a temperature of 80–180°C for 5–60 min.

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