| HS Code | 535277 |
| Product Type | Negative-working photosensitive dry film photoresist for electronic and EL grade applications |
| Primary Composition | Acrylic-based photopolymer sandwiched between a polyester support film and a polyethylene release film |
| Thickness Options | Typically available in 15, 20, 25, 30, 38, and 50 micrometers |
| Film Color | Deep blue or blue-green for high visibility during alignment and inspection |
| Resolution | Capable of resolving line/space widths down to 25-50 micrometers depending on thickness |
| Photo Sensitivity | Exposure energy range commonly 40-120 mJ/cm² at 365 nm wavelength |
| Lamination Temperature | Optimal roll lamination temperature 100-120°C |
| Developer Chemistry | Aqueous alkaline developer solution, typically 1% sodium carbonate monohydrate at 30°C |
| Stripping Solution | Aqueous sodium hydroxide (3-5% KOH or NaOH) at 50-60°C |
| Adhesion Property | Excellent adhesion to copper, copper alloys, and transparent conductive oxide surfaces used in EL panels |
| Contrast And Edge Quality | High photopolymer contrast producing sharp vertical sidewalls and minimal undercut |
| Shelf Life | Six months from date of manufacture under recommended conditions |
| Storage Conditions | Store at 5-25°C in a cool, dark, dry environment, away from direct sunlight and UV sources |
| Peel Strength | Good dry film release from support and release liners without residue or stretch |
As an accredited Photosensitive Dry Film Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sealed light-tight rolls with protective liner, moisture-barrier packaging. Quantity: 100 square feet per box. Store below 25°C, keep dry. |
| Container Loading (20′ FCL) | 20′ FCL: palletized, light-proof packaging of Photosensitive Dry Film (Electronic/EL Grade), safely secured and protected from moisture. |
| Shipping | Ship Photosensitive Dry Film (Electronic/EL Grade) in opaque, moisture-barrier packaging with desiccant, inside rigid cartons to prevent creases. Protect from UV light, humidity, and excessive heat or cold. Label fragile and “Keep Dry.” Avoid stacking heavy loads. If classified non-dangerous per SDS, no UN transport restrictions apply. |
| Storage | Store Photosensitive Dry Film Electronic/EL Grade in its original sealed container in a cool, dry, dark environment, ideally 5–25°C with low humidity (<70% RH). Protect from ultraviolet light, sunlight, moisture, and excessive heat. Keep rolls flat, away from chemicals and dust. Under proper conditions, shelf life typically remains within manufacturer’s specification. |
| Shelf Life | Store in original dark, dry, cool conditions below 25°C; protect from light. Typical shelf life is six months from manufacture. |
Aqueous-processable negative-tone acrylic dry film photoresists are laminated onto mechanically scrubbed and microetched copper surfaces with a hot roll laminator at 100–120 °C roll surface temperature, 0.4–0.6 MPa nip pressure, and 1.0–1.8 m/min lamination speed; vacuum lamination is substituted when pad cratering or copper thickness variation exceeds ±5 µm across a 610 mm × 610 mm panel. For HDI outer layer traces with 25/25 µm line/space, a dry film thickness of 15–20 µm is selected at a film-to-copper thickness ratio of 0.75:1 to 1.2:1; thicker 25–30 µm film is required on 35 µm copper to prevent breakage during pattern plating. The alkaline developing solution is maintained at 0.9–1.1 wt% Na2CO3·H2O, pH 10.0–10.8, 28–32 °C, with a breakpoint controlled at 35–55% of the clean point to avoid scum formation. Panel compliance is held to IPC-6012E Class 3 and IPC-A-600K. Direct imaging with a 405 nm laser direct imager uses an exposure dose of 60–120 mJ/cm²; conventional collimated UV exposure with a 5 kW metal halide source and a Stouffer 21-step wedge at 6–9 clear step holds 20–40 µm line geometry. Where pattern plating is used, the developed openings are electroplated with copper to 20–25 µm at 1–3 A/dm², using a dry-film-to-plated-copper thickness ratio of 1.2:1 minimum to prevent mushrooming. Adhesion is tested by cross-hatch tape pull per ASTM D3359-23 and IPC-TM-650 2.4.28.1, with Class 3 acceptance requiring no resist lifting on ≥95% of edges. This segment supplies HDI smartphone main boards, chip-on-flex substrates, and board-to-board connector interposers.
| Dry film thickness | Minimum line/space | Exposure dose at 405 nm LDI | Copper foil thickness | Adhesion test method |
|---|---|---|---|---|
| 15 µm | 25/25 µm | 50–80 mJ/cm² | 12/18 µm | IPC-TM-650 2.4.28.1 |
| 20 µm | 30/30 µm | 60–100 mJ/cm² | 18/25 µm | IPC-TM-650 2.4.28.1 |
| 25 µm | 40/40 µm | 80–120 mJ/cm² | 35 µm | IPC-TM-650 2.4.28.1 |
In the fabrication of multilayer PCB innerlayer cores from 18–35 µm rolled or electrodeposited copper foil, the dry film is applied as an etch resist over a controlled surface roughness Ra 0.25–0.45 µm after pumice scrubbing or chemical microetch with 30–50 g/L Na2S2O8 at 30–35 °C. The process chemistry for alkaline cupric chloride etching is maintained at 2.0–2.5 mol/L CuCl2, 2.0–2.5 mol/L HCl, specific gravity 1.28–1.32, oxidation-reduction potential 520–560 mV vs Ag/AgCl, temperature 48–52 °C, and spray pressure 1.2–1.8 bar; excessive free acid in this bath produces undercut, while low HCl destabilizes the monovalent copper complex and precipitates CuCl. Dry film thickness 20–25 µm is standard for 18 µm foil, giving a film-to-copper thickness ratio of 0.7:1 to 1.2:1, with lamination parameters at 100–115 °C, 0.4–0.6 MPa, and 1.2–2.0 m/min. Development uses 0.8–1.0 wt% Na2CO3 at 28–31 °C, and stripping uses 3–5 wt% NaOH at 45–55 °C. Finished innerlayer cores are validated to IPC-6012E Class 2 and Class 3, with acceptance limits per IPC-A-600K for conductor width reduction and edge roughness; line width loss from etching is typically 2–6 µm per side at an etch factor of 1.5–2.0. Terminal outputs include multilayer cores for automotive engine control units, server backplanes, and industrial PLC modules.
Chemical milling of stainless steel, copper alloy, and thin nickel alloy foil uses dry film as a selective mask when metal thickness reaches 25–500 µm and mechanical punching cannot hold ±25 µm feature position. For a 100–200 µm stainless steel sheet, dry film thickness is set at 30–40 µm, giving a film-to-metal thickness ratio of 0.15:1 to 0.4:1; lamination is run at 105–120 °C roll temperature, 0.5–0.7 MPa pressure, and 0.8–1.5 m/min to fully conform over grain boundaries. Exposure with a 365 nm collimated source at 100–150 mJ/cm² holds sidewall definition; development in 0.9–1.1 wt% Na2CO3 at 29–32 °C is stopped at 40–60% breakpoint to avoid lifting at feature edges. Stainless steel etching uses FeCl3 at 42–48 °Bé, 45–50 °C, spray pressure 1.0–2.0 bar, and free HCl 0.5–1.0 mol/L to hold etch factor at 1.5–2.0; undercut is controlled at 10–25 µm per side for 100 µm etch depth, and the sidewall angle remains 30–45° from the vertical. Copper alloy milling uses either FeCl3 or cupric chloride with similar redox control, while dry film stripping is performed in 3–5 wt% NaOH at 55–65 °C. Compliance references include ASTM E340-23 for macroetching inspection, ISO 13485 for medical component batch traceability, and ISO 9227 for salt spray corrosion verification of post-etched parts. Terminal parts include rotary encoder disks, lead frames for QFN packages, shadow masks, metal stencils, and surgical blades.
Advanced wafer-level packaging uses high-viscosity dry film photoresists on 200 mm and 300 mm wafers for redistribution layer via plating and copper pillar bump formation. The film is applied by vacuum laminator at chamber temperature 60–90 °C, pressure 0.3–0.5 MPa, and vacuum level ≤1 kPa, with film thickness 20–40 µm for copper pillar height 30–80 µm and aspect ratio 1:1 to 2:1; thickness uniformity across the wafer is held within ±2.5 µm to avoid non-uniform plating. Exposure on an i-line stepper or high-pressure mercury aligner at 365 nm uses 150–400 mJ/cm², with sidewall angle 85–90° at ≤5 µm resolution after post-exposure bake at 65–85 °C for 30–60 s on a hot plate. Development uses 2.38 wt% tetramethylammonium hydroxide at 23–25 °C for high-resolution RDL features or 1.0 wt% Na2CO3 for thicker pillar resists; breakpoint is held at 40–60% to preserve the film surface. Copper electroplating follows with CuSO4·5H2O 40–80 g/L, H2SO4 180–220 g/L, chloride ion 50–70 ppm, and current density 1–3 A/dm², with a phosphorus-copper anode area ratio 1:1 to 2:1. Strip chemistry is 2–5 wt% NaOH or a formulated solvent-based stripper at 50–60 °C, followed by oxygen plasma ash at 100–200 W for 60–120 s. Compliance screens include ASTM E595-15 outgassing, ASTM D3359-23 adhesion, JEDEC JESD22-A113F preconditioning at 85 °C/85% RH for 168 h, ISO 14644-1 Class 5 cleanroom handling, and SEMI S2-0818 equipment safety. Terminal outputs include copper pillar bumps for flip-chip assembly, redistribution layers for fan-out wafer-level packaging, and microbumps for 3D stacked integrated circuits.
| Standard or method | Test condition | Acceptance criterion |
|---|---|---|
| ASTM D3359-23 | Cross-hatch tape pull with 3M #600 | Classification 5B |
| ASTM E595-15 | 125 °C, vacuum | TML ≤1.0%, CVCM ≤0.1% |
| JEDEC JESD22-A113F | 85 °C/85% RH, 168 h | No delamination or resist lifting |
| ISO 14644-1 | Particle count at point of use | Class 5 |
| SEMI S2-0818 | Equipment safety evaluation | Interlock and exhaust verification |
Roll-to-roll flex circuit lamination onto 12.5 µm and 25 µm polyimide film requires tension-controlled dry film application with unwind tension 2–5 N/cm, wrap angle 15–30°, and lamination roll temperature 90–110 °C to prevent resist cracking or delamination during subsequent bending. The dry film thickness is 15–20 µm on 12/18/35 µm rolled copper foil, with film-to-copper thickness ratio near 0.5:1 to 1.2:1; exposure is performed by roll-to-roll LDI at 405 nm and 50–100 mJ/cm² or by collimated UV exposure with 6–9 Stouffer step. Development uses 0.8–1.0 wt% Na2CO3 at 28–30 °C, and cupric chloride etching is operated at 48–52 °C with specific gravity 1.26–1.30 to minimize undercut on 50/50 µm flex traces. Stripping is performed with 2–3 wt% NaOH at 45–50 °C, followed by a deionized water rinse at ≥18 MΩ·cm resistivity to meet ROSE ionic contamination limits below 1.56 µg/cm² NaCl equivalence per IPC-TM-650 2.3.25. Compliance is maintained to IPC-6013D for flexible printed boards, IPC-4204A for polyimide laminates, and IPC-TM-650 2.4.13 flexural endurance. Terminal products include electroluminescent lamp driver flex circuits, inkjet printer head cables, ultrasound transducer flex assemblies, and wearable sensor interconnects.
Capacitive touch sensor and display cover glass patterning applies thin dry film photoresist to indium tin oxide layers with sheet resistance 30–150 Ω/sq or to 5–10 µm copper metal mesh films. Lamination is carried out at 90–110 °C roll temperature, 0.3–0.5 MPa pressure, and 1.5–2.0 m/min speed; film thickness 10–15 µm is used to preserve 20/20 µm line/space resolution after wet etching. Exposure with 365–405 nm UV at 50–100 mJ/cm² is followed by development in 0.8–1.0 wt% Na2CO3 at 28–30 °C. ITO wet etching uses HCl 2–3 mol/L and FeCl3 0.5–1.0 mol/L at 20–25 °C for 20–40 s, while copper metal mesh etching uses cupric chloride with HCl 2.0–2.5 mol/L at 45–50 °C. Post-etch stripping uses 2–3 wt% NaOH at 45–50 °C, followed by ultrasonic DI water rinse at 40 kHz and 18 MΩ·cm resistivity. Outgassing is qualified to ASTM E595-15 with total mass loss ≤1.0% and collected volatile condensable material ≤0.1%; cleanroom operation is maintained at ISO 14644-1 Class 6 for display film handling. Terminal products include smartphone touch sensors, automotive center stack touch panels, flexible metal mesh touch sensors, and display cover glass edge bezel patterns.
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Photosensitive dry film classified as Electronic/EL grade is a negative-acting photopolymer resist supplied as a three-layer web in which the photosensitive layer is sandwiched between a polyester carrier sheet and a polyethylene cover sheet. The carrier maintains dimensional stability during roll handling; the cover sheet is removed immediately before lamination. The product is converted in roll widths from 300 mm to 610 mm, in roll lengths from 50 m to 200 m, and in nominal dry film thicknesses of 20 µm, 25 µm, 30 µm, 38 µm, and 50 µm. Model designations are not uniform across coating sources; a supplier code for this material normally concatenates the grade prefix, dry thickness, roll length, and width, such as a 25 µm product on a 100 m roll with 610 mm width. The Electronic/EL grade designation refers to a controlled-contamination film intended for printed wiring board imaging and for other applications requiring low mobile-ion residues after stripping.
Electronic/EL grade differs from general-purpose dry film principally in the restriction of mobile ionic contaminants and coating defect populations. Supplier lot certificates for electronic-grade material commonly record sodium and potassium ion concentrations below 5 ppm each, with total chloride below 5 ppm. These limits are not universal; they are used because residual halide or alkali metal ions can promote electrochemical migration after the resist is stripped from copper circuitry. The photosensitive layer is based on free-radical acrylate photopolymerization. Exposure to 365 nm I-line radiation initiates crosslinking in the image area, reducing its solubility in aqueous sodium carbonate. Unexposed material remains soluble and is removed in a spray developer. After development, the crosslinked film functions as an etch resist, an electroplating resist, or a chemical milling mask, and is subsequently stripped in dilute aqueous sodium hydroxide.
Compared with liquid photoresists, which are commonly applied by screen coating, spray coating, or electrodeposition to wet films below 15 µm, the dry film supplies a pre-metered thickness that is independent of panel surface tension, solvent evaporation, and coating-head gap variation. This property supports through-hole tenting and consistent circuit edge coverage. It also imposes a separate thermal lamination step. Production-scale hot-roll lamination of this grade is typically performed at 100 °C to 120 °C roll surface temperature, 1 m/min to 3 m/min transport speed, and 2 kg/cm² to 4 kg/cm² nip pressure. The temperature control window across the roll face should be maintained within ±5 °C; larger deviations produce tack non-uniformity and entrap air along the copper/hot-roll boundary. For high-density innerlayers, vacuum lamination at 40 °C to 60 °C with a vacuum level of −0.08 MPa to −0.095 MPa is preferred when air entrapment at trace edges is a known yield risk.
In innerlayer print-and-etch applications, the 20 µm and 25 µm grades are used with acid cupric chloride or sulfuric acid-hydrogen peroxide etchants at 48 °C to 52 °C. The resist adhesion at the trace sidewall determines etch factor; adhesion loss during etching appears as undercut that widens the design rule beyond the phototool. Batch-to-batch variation in dry film thickness should be checked at roll start, middle, and end with a micrometer or thickness gauge. A thickness deviation of more than ±3 µm from nominal shifts the required exposure dose and may push the development breakpoint outside the 50 % to 70 % production window.
Outerlayer pattern plating exposes the developed film to acid copper sulfate electrolyte under direct current. The imaged film must remain bonded to the copper surface at current densities from 1.5 A/dm² to 3.5 A/dm² for 45 min to 90 min. For this use, 38 µm and 50 µm dry film thicknesses are specified for through-hole tenting, while 20 µm and 25 µm films are restricted to innerlayer print-and-etch and outerlayer etch-resist work. Tenting failures on horizontal conveyorized plating lines are observed as resist bridge rupture at hole rims and as undercutting at the resist/copper interface when the film is undercured or when lamination temperature is below 105 °C. Production records show that roll temperature non-uniformity above 5 °C across width correlates with tenting bridge rupture at via diameters below 1.0 mm.
Adhesion is rated after lamination and development by a cross-cut tape pull per ASTM D3359-17 method B; a classification of 5B on properly micro-etched copper is the accepted baseline. The film should be developed to a breakpoint of 50 % to 70 %, determined with a Stouffer 21-step wedge, and then rinsed with deionized water at 20 °C to 25 °C. A development breakpoint above 75 % indicates underexposure and produces undercutting during plating; a breakpoint below 50 % indicates overexposure and can leave thin resist scum in narrow gaps.
Exposure is conducted on collimated UV printers with 365 nm I-line output, typically 5 kW to 7 kW metal halide lamps. The exposure dose required varies by thickness and equipment: 25 µm film commonly requires 30 mJ/cm² to 60 mJ/cm²; 38 µm film requires 45 mJ/cm² to 70 mJ/cm²; 50 µm film requires 60 mJ/cm² to 90 mJ/cm². Minimum line/space resolution for 25 µm film is 25 µm/25 µm under well-collimated exposure. Thinner 20 µm film can resolve 25 µm features with a wider exposure latitude, but it has lower tenting strength. Below 15 µm geometry, published data for this specific grade is limited and qualification usually requires laser direct imaging rather than conventional phototool exposure.
| Property | 20 µm | 25 µm | 38 µm | 50 µm |
|---|---|---|---|---|
| Typical resolution, line/space | 25 µm | 25 µm | 35 µm | 50 µm |
| Exposure energy at 365 nm | 25–40 mJ/cm² | 30–60 mJ/cm² | 45–70 mJ/cm² | 60–90 mJ/cm² |
| Development breakpoint | 50–60 % | 50–65 % | 50–70 % | 55–75 % |
| Minimum lamination temperature | 100 °C | 105 °C | 110 °C | 110 °C |
| Preferred lamination speed | 1.5–3 m/min | 1–2.5 m/min | 0.8–2 m/min | 0.6–1.5 m/min |
The principal difference is contamination control rather than photochemistry. Electronic/EL grade dry film is produced with low-alkali, low-halide raw materials and is handled in a cleanroom coating environment to reduce particulate inclusions. General-purpose dry film may use the same negative-acting acrylate chemistry but is not certified for mobile-ion ceilings or for post-strip residue performance on high-density circuit features. Liquid photoresists differ in process architecture: their wet thickness depends on coating method and solvent retention, while dry film thickness is fixed by the coating head. Liquid photoresists can conform to extremely rough substrates, but they are not as effective for tenting through-holes at the 38 µm to 50 µm thicknesses available in dry film. Electrodeposited resists can conformally cover copper surfaces, yet their deposition bath control is more complex and thickness is limited by the applied ampere-minute loading.
| Criterion | Electronic/EL dry film | General-purpose dry film | Liquid photoresist |
|---|---|---|---|
| Dry/wet thickness availability | 20–50 µm | 25–75 µm | 5–15 µm |
| Mobile-ion control | Lot-certified low | Not electronics-certified | Solvent and equipment dependent |
| Coating thickness tolerance | ±3 µm | ±5 µm or wider | Coating-weight dependent |
| Through-hole tenting strength | High at 38–50 µm | Moderate | Low unless electrodeposited |
| Fine-line resolution | 25 µm with 25 µm film | 25–50 µm depending on grade | 10–25 µm possible with thin coatings |
Storage and handling constraints are critical. The dry film is sensitive to white light and should be stored in a dark-room or yellow-light environment at 5 °C to 20 °C. Before roll lamination, the roll is conditioned at 20 °C to 25 °C for 24 h to prevent condensation and to stabilize roll-tension-dependent flatness. The material is incompatible with high relative humidity above 60 % RH during storage and lamination because moisture uptake alters film tack and can create bubbles at the resist/copper interface. It should not be placed in contact with solvent-based strippers containing methylene chloride or N-methylpyrrolidone in a closed process line; standard aqueous processing does not require these solvents and their use can attack equipment seals and enclosures.
Developer control is equally bounded. The recommended aqueous developer is 0.85 % to 1.0 % sodium carbonate monohydrate held at 28 °C to 32 °C, with spray pressure between 1.8 kg/cm² and 2.5 kg/cm². pH drift caused by dissolved carbon dioxide or dragged-in acid copper electrolyte shifts the development breakpoint; the carbonate concentration must be replenished by conductivity or titration rather than by time alone. Stripping after plating or etching is performed in 1 % to 3 % sodium hydroxide at 40 °C to 55 °C, followed by high-pressure deionized water rinse. Aggressive stripping above 3 % NaOH or above 55 °C can swell the crosslinked polymer and generate resist fragments that redeposit on narrow traces.
Compliance documentation for this grade is provided under RoHS Directive 2011/65/EU for the six restricted substances and under REACH Regulation (EC) No 1907/2006 as a supplier declaration of registration or non-registration status for the web. Because the resist is removed from the finished circuit, final conformal-coating or soldermask selection is outside the scope of this dry film. Ionic cleanliness of processed panels may be checked by resistivity of solvent extract using IPC-TM-650 2.3.25; however, that method reports whole-board contamination and cannot isolate dry film residue from plating bath carryover. Published data for direct electroluminescent lamp patterning with this exact grade is limited; qualification on indium tin oxide or silver-paste electrodes should include adhesion, residue, and optical density tests.
