Low-warping flexible copper-clad plate
By introducing a slow-curing adhesive layer and an epoxy resin adhesive layer with spherical silica filler into the flexible copper clad laminate, the warping problem was solved, the yield of the production process was improved, and the scrap rate was reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-20
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional flexible copper clad laminates warp due to the difference in thermal expansion coefficient of the PI original film and the shrinkage rate of the adhesive layer, affecting production processes such as etching, punching, and SMT, and increasing defect and scrap rates.
A slow-curing adhesive layer is added between the PI original film layer and the adhesive layer. The epoxy resin adhesive layer with spherical silica filler provides surface support and thermal stability, and slowly crosslinks the adhesive layer to release internal stress.
It effectively reduces the warpage of flexible copper clad laminates, improves warpage problems after etching, increases production yield, and reduces scrap rate.
Smart Images
Figure CN224075206U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of flexible copper clad laminates, and in particular to a low-warpage flexible copper clad laminate. Background Technology
[0002] Flexible copper clad laminate (FCCL) is the main raw material for producing flexible printed circuit boards (FPC). As the substrate of FPC, FCCL carries various electronic components and serves to conduct circuits. Traditional FCCL consists of a PI (polyimide) base film, an adhesive layer, and a copper foil layer. However, because the thermal expansion coefficient curves and expansion / contraction rates of the PI (polyimide) base film produced by different manufacturers vary, and the adhesive layer has a certain shrinkage rate after curing, the FCCL exhibits uneven stress in the finished product due to the differences in the expansion / contraction rates of each layer. This leads to varying degrees of warping after etching to remove the copper foil layer. Severe warping can affect downstream etching, punching, and surface mount technology (SMT) processes, increasing defect rates and scrap rates. Utility Model Content
[0003] Therefore, it is necessary to provide a low-warpage flexible copper clad laminate to address the issue of high warpage in flexible copper clad laminates.
[0004] This utility model provides a low-warpage flexible copper-clad laminate, comprising a PI original film layer, a slow-curing adhesive layer, an adhesive layer, and a copper foil layer. The slow-curing adhesive layer is coated on the surface of the PI original film layer, the adhesive layer is coated on the surface of the slow-curing layer, and the copper foil layer is rolled and bonded to the adhesive layer. The slow-curing adhesive layer is an epoxy resin adhesive layer with spherical silica as filler.
[0005] In some embodiments, the thickness of the slow-curing layer is 5µm to 50µm, and the thickness of the adhesive layer is 5-50µm.
[0006] In some embodiments, the sum of the thickness of the slow-curing layer and the thickness of the adhesive layer is 20µm to 25µm.
[0007] In some embodiments, the thickness of the slow-curing layer is greater than the thickness of the adhesive layer.
[0008] In some embodiments, the epoxy resin adhesive layer is a composite layer of block nitrile-modified bisphenol A epoxy resin and o-cresol epoxy resin.
[0009] In some embodiments, the adhesive layer is a composite adhesive layer made of carboxyl-terminated nitrile rubber and bisphenol A type epoxy resin.
[0010] Compared with the prior art, the present invention has at least the following beneficial effects:
[0011] This invention adds a slow-curing adhesive layer between the PI original film layer and the adhesive layer. This structure utilizes the low shrinkage rate of the slow-curing adhesive layer to provide surface support for the PI original film layer and the adhesive layer. At the same time, the thermal stability of the slow-curing layer allows the adhesive layer to slowly cross-link under the action of the slow-curing adhesive layer, delaying the curing rate of the adhesive layer. This allows the uneven stress inside the FCCL to be released during the curing process of the adhesive layer, thus preventing warping problems after the copper foil layer is etched and removed from the FCCL, reducing the warping of the flexible copper clad laminate. Attached Figure Description
[0012] Figure 1 This is a schematic cross-sectional view of a low-warpage flexible copper-clad laminate as shown in an embodiment of the present invention. Detailed Implementation
[0013] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.
[0014] It should be noted that when an element is said to be "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly on" another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.
[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0016] See Figure 1The present invention illustrates a cross-sectional structure of a low-warpage flexible copper-clad laminate, comprising a PI original film layer 1, a slow-curing adhesive layer 2, an adhesive layer 3, and a copper foil layer 4. The slow-curing adhesive layer 2 is coated on the surface of the PI original film layer 1, the adhesive layer 3 is coated on the surface of the slow-curing layer 2, and the copper foil layer 4 is rolled and bonded to the adhesive layer 3. The slow-curing adhesive layer 2 is an epoxy resin adhesive layer with spherical silica as filler.
[0017] In this embodiment, the epoxy resin adhesive layer can be a commercially available epoxy resin adhesive with added spherical silica. The spherical silica is a low-shrinkage filler that can provide good surface support for the adhesive layer 3. It also has very good thermal stability, which can improve the high-temperature resistance of the epoxy resin adhesive, thereby hindering the surface shrinkage of the adhesive layer 3 during high-temperature curing.
[0018] The prepared slow-curing adhesive is evenly coated onto the PI base film, and the slow-curing adhesive is baked for a short time to set its surface, forming slow-curing adhesive layer 2; then the prepared adhesive is evenly coated onto the surface of slow-curing adhesive layer 2, and the adhesive is baked for a short time to set its surface, forming adhesive layer 3; copper foil is rolled and bonded to the surface of adhesive layer 3 to form copper foil layer; finally, it is cured at 170℃ for 8 hours to obtain the finished FCCL.
[0019] In this embodiment, a slow-curing adhesive layer 2 is added between the PI original film layer 1 and the adhesive layer 3. This structure can provide support for the PI original film layer 1 and the adhesive layer 3, and at the same time, the adhesive layer 3 is slowly cross-linked under the action of the slow-curing adhesive layer 2, so that the uneven stress inside the FCCL can be released, and thus no warping problem will occur after the copper foil layer 4 is etched away by the FCCL, reducing the warping of the flexible copper clad laminate.
[0020] In some embodiments, the thickness of the slow-curing layer 2 is 5µm to 50µm, and the thickness of the adhesive layer 3 is 5µm to 50µm. The thicknesses of both the slow-curing layer 2 and the adhesive layer 3 are 5µm to 50µm to meet the specifications of different flexible copper-clad laminates.
[0021] Optionally, the sum of the thickness of the slow-curing layer 2 and the thickness of the adhesive layer 3 is 20µm to 25µm, so that the slow-curing layer 2 and the adhesive layer 3 can meet the good mechanical requirements of the flexible copper-clad laminate while avoiding the adhesive layer being too thick or too thin. Preferably, the thickness of the slow-curing layer 2 is greater than the thickness of the adhesive layer 3, which can provide a more stable surface support for the adhesive layer 3, thereby more effectively reducing the warpage of the flexible copper-clad laminate.
[0022] In some embodiments, the epoxy resin adhesive layer is a composite layer of block nitrile-modified bisphenol A epoxy resin and o-cresol epoxy resin. Specifically, the epoxy resin adhesive layer comprises the following components: 20-40 parts of block nitrile-modified bisphenol A epoxy resin, 14-20 parts of o-cresol epoxy resin, 25-30 parts of spherical silica (D50 of 30nm-100nm), 10-15 parts of aluminum hydroxide, and 5-10 parts of aromatic amine. After the above components are mixed evenly, they are ground for 4 hours, then coated onto the surface of the PI original film layer 1, and baked at 160°C for 10 minutes to form a slow-curing layer 2.
[0023] In some embodiments, the adhesive layer 3 is a composite adhesive layer made of carboxyl-terminated nitrile rubber and bisphenol A type epoxy resin. Specifically, the composite adhesive layer contains the following components: 10-20 parts of carboxyl-terminated nitrile rubber, 20-33 parts of bisphenol A type epoxy resin, 33-40 parts of aluminum hydroxide, and 5-10 parts of methyltetrahydrophthalic anhydride. After the above components are mixed evenly and ground for 4 hours, they are then coated onto the surface of the slow-curing layer 2 and baked at 160°C for 2 minutes to form the adhesive layer 3.
[0024] Further, the copper foil is rolled and bonded to the adhesive layer 3 to form a copper foil layer 4, which is then cured at 170℃ for 8 hours to obtain the finished flexible copper-clad laminate. The finished flexible copper-clad laminate is cut into pieces with dimensions of 25cm × 28cm. After etching to remove the copper foil layer, the laminate is placed on a horizontal surface to dry. The edge warping height is then tested using a ruler perpendicular to the horizontal surface. The warping is ≤0.3cm, indicating a significant improvement in warping.
[0025] In this embodiment, a slow-curing adhesive layer 2 is added between the PI original film layer 1 and the adhesive layer 3 to provide surface support for the PI original film layer 1 and the adhesive layer 3, reduce the surface shrinkage of the adhesive layer 3, and delay the curing rate of the adhesive layer 3. This allows the uneven stress inside the FCCL to be released, and thus prevents warping problems after the copper foil layer 4 is etched away by the FCCL, reducing the warping of the flexible copper clad laminate.
[0026] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0027] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.
Claims
1. A low warpage flexible copper clad plate characterized by, The PI original film layer, the slow curing adhesive layer, the adhesive layer and the copper foil layer are included, the slow curing adhesive layer is coated on the surface of the PI original film layer, the adhesive layer is coated on the surface of the slow curing adhesive layer, and the copper foil layer is roll-pressed and attached with the adhesive layer; the slow curing adhesive layer is a commercially available epoxy resin adhesive with spherical silica as a filler.
2. The low warpage flexible copper clad plate according to claim 1, wherein, The thickness of the slow curing adhesive layer is 5-50um, and the thickness of the adhesive layer is 5-50um.
3. The low warpage flexible copper clad plate according to claim 2, characterized by, The sum of the thickness of the slow curing adhesive layer and the thickness of the adhesive layer is 20-25um.
4. The low warpage flexible copper clad plate according to claim 2 or 3, characterized by, The thickness of the slow curing adhesive layer is greater than the thickness of the adhesive layer.