| HS Code | 607697 |
| Product Type | Negative-working photosensitive wet film for electronic/electroless-grade applications |
| Chemical Base | Acrylate photopolymer system |
| Appearance | Smooth, uniform, light-colored photosensitive film layer |
| Film Thickness | 25 micrometers (with variants from 20 to 50 micrometers) |
| Exposure Wavelength | UV region around 365 nm |
| Sensitivity | Photopolymerizes upon low-to-medium UV exposure energy |
| Resolution | Capable of producing fine line-and-space patterns in high-definition etching |
| Developer | Developed using dilute sodium carbonate aqueous solution |
| Stripper | Removable with dilute sodium hydroxide aqueous solution after use |
| Etch Resistance | Provides good resistance to acidic etchants and plating solutions |
| Adhesion | Good adhesion to copper and common electronic metal substrates |
| Storage Life | 6 months when stored under cool, dry, dark conditions |
| Handling Safety | Requires UV-filtered or yellow-room illumination |
| Functional Grade | Electronic/EL grade for high-reliability printed circuit and metal patterning processes |
As an accredited Photosensitive Wet Film (Eternal Chemical ETEC-W) Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged in vacuum-sealed, light-impermeable bags with desiccants, placed in cartons to prevent moisture and light damage. Quantity: 1 roll. |
| Container Loading (20′ FCL) | One 20′ FCL containing ETEC-W Photosensitive Wet Film, Electronic/EL grade, securely packed in sealed containers and palletized for safe transit. |
| Shipping | Ship as a photosensitive, electronic-grade chemical in opaque, sealed containers to prevent UV exposure. Maintain controlled temperature, avoid freezing and excessive heat. Ensure proper labeling for safe handling. Use grounded, ventilated transport to comply with hazardous material regulations. Avoid prolonged storage and protect from impact during transit. |
| Storage | Store Photosensitive Wet Film (ETEC-W) in a tightly sealed, light-resistant container, away from direct sunlight and UV exposure. Keep in a cool, dry, well-ventilated area at controlled temperature (recommended 5–25°C). Avoid extreme heat, moisture, and ignition sources. Use promptly after opening, and check expiration date. Keep out of reach of unauthorized personnel. |
| Shelf Life | Shelf life is 6 months from manufacture date when stored sealed, cool (5–25°C), and away from direct light. |
For copper-clad laminate inner-layer patterning at line/space geometries below 75 µm/75 µm, ETEC-W Electronic/EL Grade is run as a negative-acting aqueous-alkaline-developable liquid photoresist. The formulation is curtain-coated onto brushed and micro-etched 1/2 oz or 1 oz rolled copper foil at a wet film thickness of 18–25 µm, yielding a dry film thickness of 8–12 µm after pre-bake in a tunnel oven at 75–85 °C for 10–15 min. Viscosity at 25 °C is held between 60–120 mPa·s, with propylene glycol monomethyl ether acetate added at 2–5 wt% only when line-speed drift exceeds ±0.5 m/min; solvent addition outside this range causes curtain break-up and dry-film edge thinning on 61 cm × 76 cm panels. Formulation solids are maintained at 42–48 wt%, with photoinitiator at 3.0–5.0 wt% of total solids, acrylate oligomer at 55–65 wt% of total solids, and adhesion promoter at 0.5–1.2 wt% of total solids, derived from publicly available liquid photoresist formulation data; product-specific addition ratios shall be confirmed against the supplier technical data sheet. Exposure is performed on a 5–7 kW mercury arc or matched LED UV unit at 365 nm, with energy density of 60–140 mJ/cm² for a 10 µm dry film and an exposure gap below 100 µm. Development uses 1.0–1.2 wt% sodium carbonate at 28–32 °C and 1.0–1.5 bar spray pressure, with breakpoint held at 45–60 s; breakpoint drift above 60 s indicates photoresist scumming in 50 µm spaces and must be corrected by increasing exposure dose or developer pH. Etching proceeds in cupric chloride or ammoniacal etchant at 45–52 °C, with etch factor loss kept below 5 µm and undercut below 8 µm where resist sidewalls remain above 5 µm. Resist stripping uses 3.0–5.0 wt% NaOH at 50–55 °C followed by deionized water rinse at ≥15 MΩ·cm. Compliance references IPC-4101 for laminate base materials, IPC-TM-650 test methods for undercut and adhesion, RoHS Directive 2011/65/EU as amended by (EU) 2015/863, and REACH Regulation (EC) No 1907/2006 at the 0.1% w/w SVHC reporting threshold. The terminal finished product is the etched copper inner-layer artwork for multilayer PCB cores, accepted at 50 µm/50 µm line/space and suitable for lamination into 4–28-layer boards.
In pattern-plating configurations, the wet film serves as a plating mask over high-density interconnect substrates, where the controlling variables are resist swelling in acid copper sulfate, sidewall adhesion at dry film thickness above 20 µm, and resist lifting at conveyor transfer points. For this segment, formulation solids are set at 50–55 wt%, with epoxy acrylate oligomer at 20–30 wt% of total formulation, multifunctional monomer at 10–15 wt%, photoinitiator at 3–6 wt%, leveling agent at 0.3–1.0 wt%, and fumed silica at 1.0–2.5 wt% when vertical conveyor speed exceeds 2.0 m/min; this addition ratio raises low-shear viscosity by 300–700 mPa·s without altering photospeed. Solvent reduction below 40 mPa·s is not recommended without supplier validation because the liquid film breaks at curtain-coater gaps above 0.8 mm and produces sidewall thinning. Pre-drying at 110 °C for 20 min is required on copper substrates exposed to relative humidity above 60%, otherwise underplating and adhesion loss occur at 2.0 A/dm² acid copper plating. Exposure uses 100–180 mJ/cm² at 365 nm, with laser direct imaging exposure at 405 nm requiring dose compensation of +20–40% and a step size below 2 µm for 40 µm/40 µm line/space. Development in 1.0 wt% Na2CO3 at 28–30 °C and 1.0–1.2 bar produces breakpoint at 50–70 s; under-development leaves residual resist between 35 µm traces, while over-development above 90 s removes 2–4 µm of sidewall. Acid copper sulfate plating is then run at 2.0–3.0 A/dm² and 22–28 °C to deposit 15–25 µm of copper, followed by tin flash as etch resist and aqueous stripping in 3.0–5.0 wt% NaOH at 50–55 °C. Compliance is verified against IPC-6012 Class 3 for HDI board qualification, IPC-TM-650 for thermal stress and adhesion, ASTM D3359-17 Method B tape adhesion, and RoHS Directive 2011/65/EU as amended. The terminal finished product is the pattern-plated HDI PCB with 40 µm/40 µm copper traces, subsequently laminated into any-layer or semi-additive multilayer boards.
| Downstream segment | Compliance standard | Test method / reference | Acceptance threshold |
|---|---|---|---|
| Inner-layer etch resist | IPC-4101 | IPC-TM-650 series | Undercut ≤8 µm |
| Pattern-plating resist | IPC-6012 Class 3 | ASTM D3359-17 Method B | No peel beyond 5% of crosshatch area |
| IC package solder mask | IPC-SM-840E Class H | ASTM D257-14 | SIR ≥1×10^9 Ω after 85 °C/85% RH |
| Wafer RDL resist | SEMI S2 | RoHS Directive 2011/65/EU | Metal ion impurities <100 ppb |
Where organic package substrates for flip-chip BGA require solder mask with surface insulation resistance above 1×10^9 Ω after 85 °C/85% RH testing, ETEC-W is processed as a liquid photoimageable solder mask instead of an etch resist. The wet film is screen-printed or vacuum-printed onto BT or ABF substrate surfaces at a dry film thickness of 15–25 µm after pre-bake at 75–85 °C for 15–20 min. Formulation solids are kept at 70–78 wt%, with inorganic filler at 25–35 wt% of total solids to reduce coefficient of thermal expansion below 60 ppm/°C below glass transition, epoxy acrylate resin at 35–45 wt% of total solids, latent curing agent at 2–5 wt% of total solids, and photoinitiator at 2–4 wt% of total solids; this addition ratio balances chemical resistance against embrittlement when the solder mask bridges 30 µm dam features. Exposure on a 3–5 kW UV unit at 365 nm requires 200–400 mJ/cm² due to filler scattering, and development uses 1.0 wt% sodium carbonate at 30–32 °C with breakpoint at 60–90 s. Final thermal cure is performed in a forced-air oven at 150 °C for 60 min, followed by cooling at ≤3 °C/min to prevent microcracking. Compliance references IPC-SM-840E Class H for package-grade solder mask, UL 94 V-0 flammability, ASTM D3359-17 Method B crosshatch adhesion, ASTM D257-14 volume resistivity, and RoHS Directive 2011/65/EU with (EU) 2015/863. The terminal finished product is the bare-board package substrate solder mask layer for flip-chip CSP and BGA carriers with solder dam widths down to 40 µm and pad openings of 80–150 µm.
The bend-stable flex segment uses a low-filler variant of ETEC-W to prevent stress whitening and cracking at dynamic bend radii below 3 mm. For this application, the formulation addition ratio differs from rigid solder mask: aliphatic urethane acrylate is added at 20–35 wt% of total formulation to achieve elongation of 30–60%, while inorganic filler is reduced below 5 wt% to maintain bend durability and avoid reflectance shifts that disturb automated optical inspection. The wet film is screen-printed onto plasma-cleaned polyimide at 12–18 µm dry thickness, pre-baked at 60–70 °C for 8–12 min, exposed at 80–120 mJ/cm² using a 365 nm UV unit, and developed in 0.8–1.0 wt% Na2CO3 at 28–30 °C; development must not exceed 60 s because the flexibilized network swells faster than rigid epoxide systems. Post-cure is run at 120–150 °C for 30–45 min. Operational boundary: amine-based adhesion promoters are incompatible with this formulation; their presence accelerates ester crosslinking in storage and reduces photospeed after 72 h at 25 °C. Additionally, relative humidity above 65% during lamination requires pre-drying of the polyimide web at 80 °C for 15 min. Compliance anchors to IPC-4202 and IPC-4203 for flexible base dielectrics, IPC-TM-650 for adhesion and flexibility, UL 94 VTM-0 for thin film flammability, and ASTM D3359-17 crosshatch adhesion. The terminal finished product is the photoimageable solder mask or coverlay layer on dynamic polyimide flex circuits used in wearables, foldable-adjacent connectors, and optical module flex assemblies with bend radii down to 2–3 mm and pad pitch below 0.3 mm.
Reel-to-reel leadframe strip lines impose different solvent loss dynamics than PCB panel lines because the copper alloy strip moves at 8–15 m/min through infrared air-impingement ovens. For selective plating resist on QFN and SOIC leadframes, ETEC-W is applied by spray coating at a dry thickness of 15–22 µm with formulation solids at 38–45 wt%, photoinitiator at 2–4 wt% of solids, leveling agent at 0.2–0.6 wt% of solids, and no filler to prevent nozzle clogging. Exposure uses 120–200 mJ/cm² at 365 nm, development in 1.0 wt% Na2CO3 at 28–32 °C, and the resist then masks Ni/Pd/Au spot plating or silver plating; stripping uses 3.0–5.0 wt% NaOH at 50–55 °C. Compliance references J-STD-002 for component lead solderability and RoHS Directive 2011/65/EU. The terminal finished product is the selectively plated QFN or SOIC leadframe strip. Published data for this specific configuration is limited; line qualification should confirm nozzle pressure and IR oven profile against the supplier technical data sheet.
| Process parameter | Inner-layer etch resist | Pattern-plating resist | IC package solder mask | Wafer RDL resist |
|---|---|---|---|---|
| Dry film thickness | 8–12 µm | 15–25 µm | 15–25 µm | 5–12 µm |
| Exposure dose at 365 nm | 60–140 mJ/cm² | 100–180 mJ/cm² | 200–400 mJ/cm² | 100–200 mJ/cm² |
| Developer condition | 1.0–1.2 wt% Na2CO3, 28–32 °C | 1.0 wt% Na2CO3, 28–30 °C | 1.0 wt% Na2CO3, 30–32 °C | 2.38% TMAH, 23 ± 1 °C |
| Development breakpoint | 45–60 s | 50–70 s | 60–90 s | 60–90 s |
Wafer-level redistribution layer plating replaces dry film when bump pitch falls below 130 µm and seed layer topography varies by ±1.5 µm across a 300 mm wafer. For this segment, ETEC-W is spin-coated at 1,000–3,000 rpm to produce a 5–12 µm dry film, with soft-bake at 90–110 °C for 90–120 s; viscosity is set at 20–60 cSt by a solvent blend of propylene glycol monomethyl ether acetate and cyclohexanone, with total solids at 35–45 wt% and metal ion impurities below 100 ppb to protect semiconductor-grade seed layers. The photosensitive formulation addition ratio includes photoinitiator at 2–5 wt% of solids, epoxy acrylate oligomer at 30–45 wt% of solids, and a low-sodium adhesion promoter at 0.5–1.0 wt% of solids; higher sodium content causes wafer edge corrosion during copper RDL electroplating. Exposure is performed on an i-line or broadband stepper at 365 nm with 100–200 mJ/cm², followed by development in 2.38% tetramethylammonium hydroxide at 23 ± 1 °C for 60–90 s; development endpoint is detected by clearing the unexposed pad window at 30–45 s without attacking the seed layer. Copper RDL electroplating then deposits 4–8 µm of copper at 1.0–2.0 A/dm², after which the resist is stripped with alkaline solvent and the wafer is oxygen-plasma ashed to remove residual organic film below 1 nm surface carbon. Compliance references SEMI S2 for equipment safety, SEMI S8 for ergonomics, RoHS Directive 2011/65/EU as amended, and REACH Regulation (EC) No 1907/2006. The terminal finished product is the electroplated copper RDL pattern on 200 mm or 300 mm wafers for fan-in WLCSP and wafer-level bumping.
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The model designation ETEC-W identifies a photosensitive wet film supplied by Eternal Chemical for electronic and EL-grade applications. The material is employed as a photopolymer imaging layer on copper-clad laminates and related conductive substrates prior to pattern plating or chemical etching. In the negative-acting process typical of this product class, ultraviolet exposure through a phototool initiates crosslinking in the image regions, while unexposed film is removed in an aqueous alkaline developer. The Electronic/EL Grade designation is a supplier classification that typically corresponds to controlled ionic contamination and reduced residue after development, but published data sheets for this specific ETEC-W configuration are limited. Lot-specific certificates of analysis should be used to establish viscosity, solids content, and exposure latitude. Relevant incoming inspection methods include IPC-TM-650 2.3.25 for ionic cleanliness of residues and ISO 3219 for rheological characterization. Because the product is supplied as a wet film rather than a dry-film resist, pre-lamination handling and solvent removal become critical process variables.
Comparative selection among ETEC-W-class wet film, dry film photoresist, and liquid photoimageable solder mask depends on topography, resolution, and thermal budget. Wet film conforms to rough copper surfaces without the vacuum lamination step required for dry film; this reduces air entrapment along circuit edges but introduces drying and thickness-control variables not present with pre-formed dry film. Dry film provides tight thickness uniformity and clean handling but can bridge over irregular topography unless vacuum lamination and optimized roll pressure are used. Liquid photoimageable solder mask exhibits higher post-cure chemical resistance and is designed for permanent dielectric or solder mask functions, whereas ETEC-W is an imaging resist that is removed after etching or plating.
| Property | ETEC-W-class wet film | Dry film photoresist | Liquid photoimageable solder mask |
|---|---|---|---|
| Application method | Screen printing, spray, or curtain coating | Hot-roll lamination | Screen printing or spray coating |
| Viscosity at 25°C | 8,000–20,000 mPa·s typical class range; ETEC-W lot data required | Not applicable | 15,000–40,000 mPa·s typical class range |
| Applied wet thickness | 5–25 µm depending on mesh or spray passes | 20–50 µm supplied | 10–30 µm after leveling |
| Resolving capability | 25–50 µm line/space under optimized exposure | 20–40 µm line/space | 50–75 µm line/space |
| Conformal coverage on rough copper | High | Moderate; vacuum lamination often required | High with spray or curtain coating |
Values in the table are representative industrial windows for electronic-grade materials of each class and are not a substitute for ETEC-W lot-specific verification. The primary difference relevant to ETEC-W is that it remains liquid before drying, allowing conformal contact with irregular circuit features but requiring an evaporation step before exposure. Over-drying hardens the resist surface and may reduce adhesion in unexposed areas, while under-drying leaves residual solvent that can cause mask sticking and exposure scatter.
On production lines using 43T–77T polyester mesh screens, the wet film is deposited at controlled mesh tension and squeegee pressure; screen-stencil thickness and open area determine wet deposit, and edge bead formation is controlled by screen emulsions and snap-off distance. Alternative coating methods include spray coating with low-pressure atomization and curtain coating for larger panel formats. After deposition, a tack-dry stage is required. For this product class, convection ovens with horizontal airflow and panel temperatures in the range of 70–80°C are common; the drying window must maintain panel surface temperature within ±5°C to avoid skin-over or solvent entrapment. A skin-over layer can trap residual solvent in the lower film and produce scumming during development or incomplete removal in fine spaces. The dry-film thickness should be measured by non-contact profilometry or beta-backscatter gauge after panel cool-down because hot measurements overstate thickness. Viscosity drift on the screen is controlled by solvent replenishment; evaporative loss increases local solids, raising exposure threshold and complicating line-width control. The cleanroom environment should be maintained below 60% relative humidity to prevent moisture absorption and surface tack variation. Published data for this specific ETEC-W configuration is limited; process ranges should be established by designed experiments on the actual coating line.
The pre-bake step converts the wet film into a non-blocking, photoactive dry layer. In conveyorized horizontal ovens with 3–5 m heated length and multiple temperature zones, the initial zone is often set 10–15°C lower than the final zone to prevent surface skinning. Panel temperature, rather than air-set temperature, controls the evaporation rate. A panel temperature ramp of 2–4°C/min is typically used for films in this class; faster ramps can create a dense surface layer that inhibits solvent release. The resulting entrained solvent may express itself later as bubbles at the resist-copper interface during exposure or as developer scumming in isolated spaces. Slow evaporation, by contrast, can leave the resist tacky and susceptible to phototool sticking in the vacuum frame. Production-scale defect logs on automated optical inspection equipment often show a characteristic cluster of open circuits or shorts near panel edges when solvent removal is non-uniform; edge areas dry faster than interior zones in poorly balanced ovens.
The required pre-bake endpoint is not a fixed time but a retained solvent level and surface tack condition. Because ETEC-W-specific retained solvent data are not openly published, the manufacturing line should establish limits using gas chromatography or thermogravimetric analysis of dried panels. A typical working target for the product class is retained solvent below 2–4% by weight before exposure, but the exact value must be established for the ETEC-W lot and oven configuration. Operators should also monitor oven exhaust rate; insufficient exhaust raises solvent vapor concentration and can slow evaporation in the later zones. Conveyor belt speed, zone temperatures, and exhaust damper settings should be captured in batch records as process variables that directly influence final resolution.
Replacement of dry film with ETEC-W on a high-density substrate line changes the front-end equipment configuration and the defect signature. A dry-film laminator is removed or bypassed, and a screen printer or spray coater is inserted before the pre-bake oven. The process is more sensitive to panel flatness and copper surface energy than dry-film lamination. Copper pretreatment must produce a uniform microetched surface; a sodium persulfate microetch followed by deionized water rinse at resistivity above 1 MΩ·cm is typically used. Surface roughness measured by contact profilometry should be held within a range established for adhesion, often 0.3–0.5 µm Ra on innerlayer copper. Lower roughness reduces mechanical interlocking and can produce undercut adhesion loss during etching; higher roughness can cause fine-line resolution loss due to light scattering at the resist-copper interface.
When the product is used for pattern plating, the resist must withstand acidic copper sulfate electrolytes with sulfuric acid at 200–250 g/L and copper at 70–90 g/L under air agitation. The imaged film should remain intact at electrolyte temperatures up to 24°C; above that, resist softening and pattern lift may occur unless the specific ETEC-W grade is validated. For etching, compatibility with acidic cupric chloride at 2.5–3.5 M free hydrochloric acid and ferric chloride systems is relevant, but manufacturer-specific chemical compatibility data should be reviewed. Via tenting is not automatically suitable for wet films because the applied thickness on the via periphery is lower than on the flat surface; if via tenting is required, a separate validation using cross-sections per IPC-A-600 is necessary. Failure modes observed during such replacement typically include resist chipping at conveyor transfer points, coating non-uniformity on warped panels, and developer loading shifts due to higher dissolved solids. These should be tracked with panel-level traceability and microsection sampling.
Photospeed is evaluated with a 21-step Stouffer optical wedge exposed under production phototool conditions. Exposure units using 5 kW or 7 kW metal-halide lamps with peak output in the 365–420 nm range are typical; vacuum frame pressure should be held below 0.08 MPa differential to avoid phototool movement and resist damage. The step tablet provides a relative measure of exposure latitude rather than an absolute line-width guarantee. In the wet film class, a retained step range of 7–9 after development is common, but ETEC-W-specific step retention should be determined from the supplier’s technical data sheet or internal process capability studies. Underexposure produces soft sidewalls and poor adhesion; overexposure increases resist foot width and may close fine spaces. Line width deviation from phototool dimension should be measured by automated optical inspection after development and after final etch. For fine-line work below 50 µm, collimated UV sources are preferred because light scattering through the phototool and wet film increases with thickness.
The development endpoint is detected by a breakpoint method: panels are passed through a spray-developing chamber with sodium carbonate solution, and the time to clear unexposed film is recorded. Breakpoint is expressed as a percentage of the total developer chamber residence time; values of 40–60% are commonly targeted for consistent fine-line development, with final clear time at 1.5–2.0× the breakpoint. Developer concentration is typically 0.85–1.10% sodium carbonate monohydrate, maintained by conductivity or pH control. Excessive developer attack in exposed areas appears as reduced sidewall integrity and can be detected by cross-sectioning per IPC-TM-650 2.1.1 or equivalent internal methods. Published data for this specific ETEC-W configuration is limited; validation on the actual spray chamber is required.
Regulatory status for ETEC-W Electronic/EL Grade should be verified against the supplier’s current safety data sheet and certificate of compliance. The table below identifies typical standards and test methods used for incoming and in-process verification of electronic-grade photoresists. The absence of a published ETEC-W-specific value in this table does not imply non-compliance; it indicates that the supplier’s lot documentation must be the controlling reference.
| Control parameter | Reference method or standard | Typical acceptance basis |
|---|---|---|
| Viscosity | ISO 3219 | Lot-specific certificate of analysis |
| Solids content | ISO 3251 | Lot-specific certificate of analysis |
| Adhesion after development | IPC-TM-650 2.4.28.1 or ASTM D3359 | No lifting at specified line width; 4B–5B class rating where applicable |
| Ionic contamination | IPC-TM-650 2.3.25 | Below purchaser-defined residue limit |
| Flammability | ASTM D93 or supplier SDS | Not classified as flammable liquid by flash point |
| RoHS restricted substances | IEC 62321 test suite | Below 0.1% by weight for lead, mercury, hexavalent chromium, PBB, PBDE; below 0.01% for cadmium |
| REACH SVHC content | EC 1907/2006 Article 33 | Supplier confirmation of absence above 0.1% w/w |
In production, the material should be returned to 18–24°C storage when not in use and protected from actinic light. Opened containers should be sealed to limit solvent loss and viscosity drift. Waste developer containing dissolved photopolymer should be treated as process wastewater; local discharge limits may require chelation or pH adjustment before release. Process qualification remains dependent on lot-specific data and production-scale trials.
