Light-sensitive dry film for metal processing and preparation method thereof

Abstract

The invention relates to a photosensitive dry film for metal processing and a preparation method thereof, and relates to the technical field of photosensitive dry films, the photosensitive dry film for metal processing sequentially comprises a light-transmitting protective layer with a thickness of 5-15 [mu] m and a light transmittance greater than or equal to 90%; the anti-reflection layer comprises nano carbon black or metal oxide particles, and the thickness of the anti-reflection layer is 0.1-1 [mu] m; the thickness of the photosensitive resin layer is 5-8 microns, and the photosensitive resin layer comprises a silicon-based polymer and a two-photon absorption type photoinitiator; the thickness of the pressure-sensitive adhesive layer is 1-3 [mu] m, and the surface adhesive force of the pressure-sensitive adhesive layer is 5-15 N / 25 mm; and a release film, wherein the release force of the release film is 0.01 to 0.1 N / cm. According to the photosensitive dry film, through the innovative five-layer structural design, comprehensive breakthrough in resolution, process stability and application range is achieved.

Description

Technical Field

[0001] This application relates to the field of photosensitive dry film technology, and in particular to a photosensitive dry film for metal processing and its preparation method. Background Technology

[0002] Currently, photosensitive dry film is a photolithography material used in electronic manufacturing (such as PCB and semiconductor processing). It consists of a photosensitive layer and upper and lower protective films, and achieves pattern transfer through ultraviolet exposure and development. Its working principle is divided into negative (exposed areas cure) and positive (exposed areas dissolve), offering advantages such as high resolution (up to 10-25μm), ease of operation (no coating required), and uniform thickness. It is widely used in high-precision pattern creation for PCB outer layer circuits, inner layer circuits, and semiconductor packaging. A typical process includes bonding, exposure, development, and etching steps. Compared to liquid photoresist, it is more efficient and environmentally friendly, making it one of the core materials for modern microfabrication.

[0003] Traditional photosensitive dry films are limited by the fundamental laws of optical diffraction. When using a 365 nm ultraviolet light source, their theoretical resolution is constrained by the wavelength of the light source and the characteristics of the optical system. Due to the thickness of the photosensitive layer, light undergoes significant scattering within the material, resulting in blurred edges of the exposed pattern. Simultaneously, reflected light from the substrate surface interferes with the incident light, creating periodic uneven exposure, which severely affects pattern accuracy.

[0004] Traditional photosensitive materials are prone to expansion and deformation during development, which can lead to deviations in pattern size. Furthermore, insufficient photoinitiator efficiency can easily trigger unexpected side reactions, causing diffusion of the exposed area. Excessive developer penetration makes it difficult to precisely control the etching direction, resulting in irregular lateral etching at the pattern edges.

[0005] Insufficient adhesion between the dry film and the substrate can lead to poor bonding, especially on rough substrate surfaces. When creating dense patterns, optical interference between adjacent lines can result in uneven linewidth. These factors collectively limit the application of traditional photosensitive dry films in fine pattern fabrication, necessitating performance improvements through material optimization and process modifications.

[0006] Regarding the aforementioned technologies, the inventors believe that light diffraction and scattering occur during exposure, resulting in blurred edges of the pattern and making it difficult to create fine lines. Secondly, the material expands and deforms during development, causing deviations between the actual pattern size and the design. Finally, if the dry film is not firmly bonded to the substrate, it is prone to peeling, leading to defects when fabricating high-density circuits. These factors collectively make it difficult for traditional photosensitive dry films to stably produce fine patterns below 10 micrometers, thus limiting the resolution of photosensitive dry films. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a photosensitive dry film for metal processing and a method for preparing the same, which solves the technical problem of resolution limitation of photosensitive dry films.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A photosensitive dry film for metal processing, comprising, in sequence: A light-transmitting protective layer, wherein the thickness of the light-transmitting protective layer is 5-15μm and the light transmittance is ≥90%; An anti-reflective layer comprising nano-carbon black or metal oxide particles with a thickness of 0.1-1 μm; A photosensitive resin layer, the photosensitive resin layer having a thickness of 5-8 μm, comprising a silicon-based polymer and a two-photon absorption photoinitiator; Pressure-sensitive adhesive layer, wherein the thickness of the pressure-sensitive adhesive layer is 1-3μm and the surface adhesion is 5-15N / 25mm; Release film, wherein the peeling force of the release film is 0.01-0.1 N / cm.

[0009] Furthermore, the nanoparticles of the antireflective layer are silicon dioxide or zinc oxide with a particle size of 10-50 nm, dispersed in an acrylate carrier.

[0010] Furthermore, the photosensitive resin layer contains 15-30 wt% of an epoxy acrylate siloxane copolymer with a molecular weight of 2000-5000 Da.

[0011] Furthermore, the pressure-sensitive adhesive layer is a UV-curable acrylic adhesive with an elastic modulus of 0.1-1 MPa after curing.

[0012] Furthermore, the surface of the release film (50) is plasma treated, and the water contact angle is ≤30°.

[0013] A method for preparing a photosensitive dry film for metal processing as described in any of the preceding claims includes the following steps: Step 1: Anti-reflective layer coating: Apply anti-reflective slurry to the surface of the light-transmitting protective layer using a micro-gravure coating method. The slurry contains nano-silica particles (10-50nm) and an acrylate carrier. The coating thickness is 0.1-1μm. After drying and curing at a gradient temperature of 80-100℃, an anti-reflective layer is formed. Step 2: Precision molding of photosensitive layer: A photosensitive resin layer is formed on the anti-reflective layer by slit extrusion coating method with a coating thickness of 5-8μm. The coating speed is controlled at 1-3m / min, and the ambient temperature and humidity are 23±2℃ and RH45±5%. After coating, it is UV pre-cured under nitrogen protection (energy 5-10mJ / cm²). Step 3: Composite Structure Integration: The pre-made pressure-sensitive adhesive layer and release film are thermally bonded in a vacuum press with a vacuum degree ≤10Pa and a pressure of 0.2-0.5MPa. Segmented temperature control is used (preheating zone 40-50℃ / composite zone 60-70℃). After cooling, the roll is wound up with the tension controlled at 10-15N / m.

[0014] Furthermore, the antireflective paste described in step 1 has a solid content of 20-30% and a viscosity controlled at 500-1500 cps (25℃). After coating, it is first dried at 80℃ for 30 seconds, and then dried at 100℃ for 60 seconds.

[0015] Furthermore, in step 2, the die gap for slit extrusion coating is 50-80 μm, and the distance between the extruder and the substrate is set to 1.2-1.5 times the coating thickness.

[0016] Furthermore, step 3, after thermal bonding, also includes a curing treatment: standing at 40-45℃ for 24-48 hours to fully release the internal stress of the adhesive layer.

[0017] An application of a photosensitive dry film as described in any of the preceding claims in a printed circuit board.

[0018] In summary, this application includes at least one of the following beneficial technical effects of photosensitive dry films for metal processing and their preparation methods: By leveraging the synergistic effect of an ultrathin photosensitive layer (5-8μm) and an anti-reflective layer, combined with 248nm DUV exposure technology, the dry film resolution is improved to 3-5μm, more than twice that of traditional dry films, with linewidth deviation controlled within ±0.3μm, meeting the requirements of advanced packaging RDL layers and HDI boards for fine lines. By combining a pressure-sensitive adhesive layer (1-3μm) with a plasma-treated release film, the bonding yield of dry film on rough substrates (Ra≤2μm) reaches over 98.5% (Example 3). Furthermore, the vacuum thermal lamination process ensures that the warpage of the roll material is <0.5mm / m, thus solving the problem of development line breakage caused by poor bonding of traditional dry film. Silicon-based modified photosensitive resin, combined with alkaline developer (0.5-1.5wt% TMAH), reduces the swelling rate to <1.5% (compared to ≥5% for traditional products), while being compatible with flexible PI substrates and ceramic substrates, thus expanding its application scenarios in flexible electronics and power module packaging. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of a photosensitive dry film for metal processing, which is the main feature of this application.

[0020] Reference numerals: 1. Light-transmitting protective layer; 2. Anti-reflective layer; 3. Photosensitive resin layer; 4. Pressure-sensitive adhesive layer; 5. Release film. Detailed Implementation

[0021] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this invention, the invention will be further described below in conjunction with specific embodiments.

[0022] The following is combined with Figure 1 This application will be described in further detail.

[0023] This application discloses a photosensitive dry film for metal processing and its preparation method.

[0024] Reference Figure 1 A photosensitive dry film for metal processing comprises, in sequence, a light-transmitting protective layer 1, an anti-reflective layer 2, a photosensitive resin layer 3, a pressure-sensitive adhesive layer 4, and a release film 5. The light-transmitting protective layer 1 reduces energy loss during exposure. By adding the anti-reflective layer 2 and the pressure-sensitive adhesive layer 4, linewidth errors can be controlled within the acceptable range, and the adhesive layer reduces bubbles and edge peeling.

[0025] The thickness of the light-transmitting protective layer 1 is 5-15 μm, preferably 8 μm, and the light transmittance of the light-transmitting protective layer 1 is ≥90%. In use, the light-transmitting protective layer 1 can reduce scratches on the photosensitive resin layer 3 by foreign objects and improve the overall tensile strength of the photosensitive dry film.

[0026] The anti-reflective layer 2 comprises nano-carbon black or metal oxide particles, wherein the nanoparticles of the anti-reflective layer 2 are silicon dioxide or zinc oxide, dispersed in an acrylate carrier. The thickness of the anti-reflective layer 2 is 0.1-1 μm, preferably 0.5 μm. Further, the particle size of the nanoparticles is 10-50 nm, preferably 20 nm. The anti-reflective layer 2 can reduce the standing wave effect caused by substrate reflection, thereby increasing the exposure energy threshold difference by more than 20%.

[0027] The photosensitive resin layer 3 comprises a matrix resin and a photoinitiator. The matrix resin is 15-30 wt% of an epoxy acrylate-siloxane copolymer with a molecular weight of 2000-5000 Da, and the photoinitiator is a two-photon absorption type. The thickness of the photosensitive resin layer 3 is 5-8 μm, preferably 6 μm. During use, after exposure and development, the photosensitive resin layer 3 can achieve a linewidth of ≤3 μm. Furthermore, it exhibits a etching resistance time of ≥5 min in an acidic copper chloride etching solution.

[0028] The pressure-sensitive adhesive layer 4 is a UV-curable acrylic adhesive with an elastic modulus of 0.1-1 MPa after curing. The thickness of the pressure-sensitive adhesive layer 4 is 1-3 μm, preferably 2 μm. Furthermore, the adhesion strength of the pressure-sensitive adhesive layer 4 to the copper / PI / ceramic substrate is 5-15 N / 25 mm. During use, the elastic deformation of the pressure-sensitive adhesive layer 4 absorbs the difference in thermal expansion of the substrate.

[0029] The release film 5 has a peel force of 0.01-0.1 N / cm, preferably 0.01-0.1 N / cm. Furthermore, the surface of the release film 5 is plasma-treated, resulting in a water contact angle ≤30°. During use, the release film 5 reduces contamination before lamination.

[0030] A method for preparing a photosensitive dry film for metal processing includes the following steps: Anti-reflective layer 2 coating: An anti-reflective slurry is coated onto the surface of the light-transmitting protective layer 1 using a micro-gravure coating method. The solid content of the anti-reflective slurry is 20-30%, preferably 20%, and the viscosity is controlled at 500-1500 cps (25℃). The slurry contains nano-silica particles (10-50nm) and an acrylate carrier. The coating thickness is 0.1-1μm. It is cured by gradient temperature increase drying at 80-100℃. Preferably, after coating, it is first dried at 80℃ for 30s, and then dried at 100℃ for 60s to form the anti-reflective layer 2.

[0031] Precision molding of the photosensitive layer: A photosensitive resin layer 3 is formed on the anti-reflective layer 2 using a slot extrusion coating method. The die gap for slot extrusion coating is 50-80 μm, preferably 60 μm. The distance between the extruder and the substrate is set to 1.2-1.5 times the coating thickness, preferably 1 times. The coating thickness is 5-8 μm, preferably 6 μm, and the coating speed is controlled at 1-3 m / min, preferably 2 m / min. The ambient temperature and humidity are 23±2℃ and RH 45±5%. After coating, UV pre-curing is performed under nitrogen protection (energy 5-10 mJ / cm²). Step 3: Composite Structure Integration: The pre-fabricated pressure-sensitive adhesive layer 4 and release film 5 are thermally laminated in a vacuum press. The vacuum degree is ≤10Pa, and the pressure is 0.2-0.5MPa, preferably 0.3MPa. After thermal lamination, a curing treatment is performed: the material is left to stand at 40-45℃ for 24-48 hours to fully release the internal stress of the adhesive layer. Segmented temperature control is adopted (preheating zone 40-50℃ / lamination zone 60-70℃). After cooling, the material is wound up, and the tension of the roll is controlled at 10-15N / m.

[0032] Application of a photosensitive dry film in printed circuit boards.

[0033] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A photosensitive dry film for metal processing, characterized in that, In order, they include: A light-transmitting protective layer (1) has a thickness of 5-15 μm and a light transmittance of ≥90%. An anti-reflective layer (2) comprising nano-carbon black or metal oxide particles with a thickness of 0.1-1 μm; Photosensitive resin layer (3), the photosensitive resin layer (3) having a thickness of 5-8 μm, comprising a silicon-based polymer and a two-photon absorption photoinitiator; Pressure-sensitive adhesive layer (4), the thickness of the pressure-sensitive adhesive layer (4) is 1-3μm, and the surface adhesion is 5-15N / 25mm; Release film (5), wherein the peeling force of the release film (5) is 0.01-0.1 N / cm.

2. The photosensitive dry film for metal processing according to claim 1, characterized in that, The antireflective layer (2) consists of nanoparticles of silicon dioxide or zinc oxide with a particle size of 10-50 nm, dispersed in an acrylate carrier.

3. The photosensitive dry film for metal processing according to claim 1, characterized in that, The photosensitive resin layer (3) contains 15-30 wt% epoxy acrylate siloxane copolymer with a molecular weight of 2000-5000 Da.

4. The photosensitive dry film for metal processing according to claim 1, characterized in that, The pressure-sensitive adhesive layer (4) is a UV-curable acrylic adhesive with an elastic modulus of 0.1-1 MPa after curing.

5. The photosensitive dry film for metal processing according to claim 1, characterized in that, The release membrane (5) (50) has a plasma-treated surface with a water contact angle ≤30°.

6. A method for preparing a photosensitive dry film for metal processing as described in any one of claims 1-5, comprising the following steps: Step 1: Coating of anti-reflective layer (2): Apply anti-reflective slurry to the surface of the light-transmitting protective layer (1) using a micro-gravure coating method. The slurry contains nano-silica particles (10-50nm) and acrylate carrier. The coating thickness is 0.1-1μm. After drying and curing at a gradient temperature of 80-100℃, an anti-reflective layer (2) is formed. Step 2: Precision molding of photosensitive layer: A photosensitive resin layer (3) is formed on the anti-reflective layer (2) by slit extrusion coating method with a coating thickness of 5-8μm, and the coating speed is controlled at 1-3m / min. The ambient temperature and humidity are 23±2℃ and RH45±5%. After coating, it is UV pre-cured under nitrogen protection (energy 5-10mJ / cm²). Step 3: Composite structure integration: The pre-made pressure-sensitive adhesive layer (4) and release film (5) are thermally bonded in a vacuum press. The vacuum degree is ≤10Pa and the pressure is 0.2-0.5MPa. Segmented temperature control is adopted (preheating zone 40-50℃ / composite zone 60-70℃). After cooling, the roll is wound up and the tension of the roll is controlled at 10-15N / m.

7. The method as described in claim 6, characterized in that, The antireflective paste described in step 1 has a solid content of 20-30% and a viscosity controlled at 500-1500 cps (25℃). After coating, it is first dried at 80℃ for 30s, and then dried at 100℃ for 60s.

8. The method as described in claim 6, characterized in that, In step 2, the die gap for slit extrusion coating is 50-80 μm, and the distance between the extruder head and the substrate is set to 1.2-1.5 times the coating thickness.

9. The method as described in claim 6, characterized in that, Step 3, after thermal bonding, also includes a curing treatment: standing at 40-45℃ for 24-48 hours to fully release the internal stress of the adhesive layer.

10. The application of the photosensitive dry film as described in any one of claims 1-5 in a printed circuit board.

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