| HS Code | 742538 |
| Product Name | DuPont EtchMaster |
| Product Type | Negative-working dry film photoresist |
| Manufacturer | DuPont |
| Application | Patterned copper etching for PCB inner and outer layers |
| Physical Form | Rolled dry film with polyester support and polyethylene separator |
| Color | Blue |
| Film Thickness | 25 to 40 micrometers depending on product grade |
| Resolution | Supports fine line patterning down to 25-50 micrometers lines/spaces |
| Exposure Wavelength | UV sensitive in the 350-420 nm range |
| Exposure Energy | Typically 80-150 mJ/cm2 |
| Lamination Condition | Hot-roll lamination at 105-125 degrees Celsius |
| Development Process | Aqueous spray development using 0.8-1.2% sodium carbonate solution |
| Etch Resistance | Compatible with acid and alkaline cupric chloride etchants |
| Stripping Method | Aqueous stripping with 3-5% sodium hydroxide solution at 50-55 degrees Celsius |
| Storage Condition | Store dark and dry at 5-20 degrees Celsius in original packaging |
| Shelf Life | 6 months from date of manufacture when properly stored |
As an accredited PCB Dry Film Photoresist DuPont EtchMaster factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | DuPont EtchMaster dry film photoresist is supplied in light-proof, vacuum-sealed packaging, with rolls typically containing 400 square feet per package. |
| Container Loading (20′ FCL) | 20′ FCL: PCB Dry Film Photoresist (DuPont EtchMaster) loaded on pallets, secured, moisture-proof wrapped, in sealed container. |
| Shipping | Ship in opaque, moisture-resistant packaging to protect light-sensitive dry film. Avoid UV exposure, high heat, and humidity. Store flat between 5–25°C. Not classified as dangerous goods for transport, but keep away from ignition sources and label fragile. Use sturdy cartons with minimal movement to prevent creasing or edge damage. |
| Storage | Store in the original sealed container in a cool, dark, dry area at 15–25°C. Protect from sunlight, ultraviolet light, humidity, and physical damage. Keep away from oxidizers, open flames, and heat sources. Ensure ventilation and maintain clean conditions. Follow manufacturer’s shelf-life guidance, and keep only authorized personnel access. |
| Shelf Life | Store cool, dry, and dark in original packaging; typical shelf life is six months from manufacture, avoiding light and humidity. |
On horizontal conveyorised inner-layer lines processing 0.5 mm to 3.2 mm FR-4 cores, DuPont EtchMaster dry film photoresist is laminated after pumice or aluminium oxide brushing and an oxide replacement adhesion promotion step. The film is a negative-tone, solvent-processed photopolymer supplied as 100% solids; the applicable formulation addition ratio is therefore the developer working-solution concentration rather than a liquid resist loading. For 35 µm copper foil, the selected film thickness is 38 µm; for 70 µm copper foil, 50 µm film is specified to reduce etch lifting and to survive spray impingement. Lamination is performed at roll temperature 105 °C to 120 °C, speed 0.8 m/min to 1.6 m/min, nip pressure 3.0 bar to 5.0 bar. Exposure on a metal halide or 365 nm UV-LED printer is set to 50 mJ/cm² to 80 mJ/cm², with a Stouffer 41-step wedge held at 7 to 9 clear steps after development. Development uses 0.85 wt% to 1.0 wt% sodium carbonate monohydrate at 28 °C to 32 °C, pH 10.6 to 11.0, with spray pressure 1.2 bar to 1.8 bar and a breakpoint of 40% to 60%. The etchant is ammoniacal cupric chloride maintained at pH 8.3 to 8.8, free chloride 5.8 M to 6.2 M, specific gravity 1.18 g/mL to 1.22 g/mL, redox potential 520 mV to 560 mV, and temperature 48 °C to 52 °C. Stripping follows in 3 wt% to 5 wt% sodium hydroxide at 45 °C to 55 °C. Production-scale horizontal etchers equipped with oscillating spray manifolds show undercut variation of ±2 µm to ±5 µm when pH and redox drift outside these limits. Compliance is assessed under IPC-6012E Section 3.6 for conductor width and spacing, IPC-A-600K acceptance criteria, IPC-4101E for laminate base material, UL 94V-0 for final flammability, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006 Article 33. Terminal articles include engine control unit multilayer PCBs, battery management system boards, industrial servo drive cards, and 5G backplane cores.
The dominant yield-loss mechanism in outer-layer pattern plating is not plating thickness uniformity but resist foot undercut at the copper-coverplate interface, which widens after electrolytic copper deposition. For HDI outer layers with dry film thickness selected at 25 µm or 30 µm on 9 µm to 18 µm electroless copper over FR-4 or BT laminate, DuPont EtchMaster dry film photoresist is laminated at 100 °C to 115 °C with a conformable top roller to displace air from fine topography. Direct imaging at 405 nm or UV-LDI is set to 40 mJ/cm² to 60 mJ/cm², with panel scale registration held to ±10 µm. The developer working-solution concentration is 0.8 wt% to 0.9 wt% Na₂CO₃·H₂O, maintained at 28 °C to 30 °C and pH 10.3 to 10.7; the addition-ratio equivalent in the plating bath is copper sulphate pentahydrate 190 g/L to 230 g/L, sulphuric acid 50 g/L to 80 g/L, chloride ion 40 ppm to 70 ppm, and brightener carrier 0.5 mL/L to 2.5 mL/L based on ampere-hour uptake. Electrolytic copper is plated at 2.0 A/dm² to 3.5 A/dm² to a thickness of 20 µm to 25 µm, followed by tin etch resist 3 µm to 8 µm. Dry film is stripped in an alkaline organic stripper at 45 °C to 55 °C with ultrasonic assist, the exposed electroless copper is flash-etched in 2% to 3% H₂SO₄/Na₂S₂O₈, and tin is removed in 10% to 15% nitric acid. Process audits on production lines show that developer breakpoint drift beyond 55% creates residual photopolymer islands between 30 µm line pairs, generating plating skip. Compliance references are IPC-6012E Class 3, IPC-A-600K, IPC-TM-650 Method 2.6.3.3 for surface insulation resistance after stripping, UL 94V-0, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006. Terminal articles include HDI smartphone main boards, wearable device rigid-flex assemblies, optical transceiver interposers, and automotive camera module PCBs.
Roll-to-roll conversion of polyimide-clad laminates requires lower lamination temperature and lower web tension than rigid-board cut-sheet processing, because excessive thermal input causes transverse shrinkage of the polyimide base film and resist adhesion failure at the copper grain boundaries. EtchMaster dry film photoresist is laminated at roll temperature 90 °C to 110 °C, speed 0.5 m/min to 1.2 m/min, web tension 15 N to 35 N, using 25 µm film for 18 µm rolled-annealed copper foil and 30 µm film for 35 µm electrodeposited copper. The relevant formulation addition ratio is the developer working solution at 0.7 wt% to 0.9 wt% Na₂CO₃·H₂O, pH 10.3 to 10.7, 28 °C to 30 °C, with a breakpoint set between 45% and 55%. Exposure is performed with collimated UV at 45 mJ/cm² to 75 mJ/cm² through a polyester phototool; the exposure dimension is compensated for polyimide dimensional stability of 0.03% to 0.15% depending on supplier and pre-bake. Etching uses acidic cupric chloride at 2.5 mol/L to 3.5 mol/L HCl, specific gravity 1.28 g/mL to 1.34 g/mL, redox 500 mV to 560 mV, 45 °C to 50 °C, with spray pressure reduced to 1.0 bar to 1.5 bar to avoid resist peel on thin cores. Stripping uses 2 wt% to 3 wt% NaOH at 40 °C to 50 °C, followed by a deionised water rinse at 1.5 bar. Adhesion of the dry film to copper is verified by ASTM D3359-17 Method B with a minimum classification of 4B on production coupons. Conformance for flexible boards is assessed under IPC-6013D Class 3, IPC-FC-234 for adhesiveless and adhesive-based flex constructions, UL 94V-0, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006. Terminal articles include automotive flex harnesses, foldable phone hinge interconnects, medical ablation catheter circuits, and battery management sense-line flex assemblies.
| Configuration | Film thickness | Exposure dose | Developer concentration | Etch or plating medium |
|---|---|---|---|---|
| Rigid inner-layer | 38–50 µm | 50–80 mJ/cm² | 0.85–1.0 wt% Na₂CO₃·H₂O | Ammoniacal cupric chloride, pH 8.3–8.8 |
| Fine-line pattern plating | 25–30 µm | 40–60 mJ/cm² | 0.8–0.9 wt% Na₂CO₃·H₂O | Acid copper sulphate, 190–230 g/L CuSO₄·5H₂O |
| Roll-to-roll flex | 25–30 µm | 45–75 mJ/cm² | 0.7–0.9 wt% Na₂CO₃·H₂O | Acidic cupric chloride, 2.5–3.5 mol/L HCl |
| Chemical milling | 38–50 µm | 80–140 mJ/cm² | 1.0–1.2 wt% Na₂CO₃·H₂O | Ferric chloride, 40–45 °Baumé |
| QFN leadframe | 38–50 µm | 60–100 mJ/cm² | 0.9–1.0 wt% Na₂CO₃·H₂O | Cupric chloride, 140–180 g/L CuCl₂·2H₂O |
| Shadow mask | 15–20 µm | 90–150 mJ/cm² | 0.6–0.8 wt% Na₂CO₃·H₂O | Ferric chloride, 35–42 °Baumé |
| Thick-copper power board | 50–75 µm | 120–180 mJ/cm² | 1.0–1.1 wt% Na₂CO₃·H₂O | Ammoniacal cupric chloride, pH 8.4–8.8 |
In chemical milling, the dry film functions as a selective mask over metal foils that are through-etched or half-etched by high-aggression ferric chloride or cupric chloride solutions. EtchMaster dry film photoresist is applied to degreased, microetched surfaces of 304/316 stainless steel, nickel 200, and Inconel 625 at metal thicknesses from 0.025 mm to 0.5 mm. The selected film thickness is 38 µm for foils up to 0.1 mm and 50 µm for 0.1 mm to 0.5 mm, because thicker metal stock demands longer dwell time in the etch chamber. Lamination uses roll temperature 105 °C to 125 °C, speed 0.6 m/min to 1.4 m/min, and pressure 4 bar to 6 bar. UV exposure at 80 mJ/cm² to 140 mJ/cm² provides sufficient crosslink density to resist etchant attack at feature edges. The developer addition-ratio equivalent is 1.0 wt% to 1.2 wt% Na₂CO₃·H₂O at 30 °C to 35 °C, with a breakpoint of 50% to 60% and continuous conductivity control at 50 mS/cm to 60 mS/cm. Etching is conducted in ferric chloride at 40 °Baumé to 45 °Baumé and 45 °C to 55 °C, with pulse-spray pressure 1.5 bar to 2.5 bar; for nickel alloys, cupric chloride with concentrated hydrochloric acid at 2.5 mol/L to 3.5 mol/L is used where tight dimensional tolerance is required. Etch factor on stainless steel typically falls to 1.5:1 to 2.5:1, requiring phototool compensation of 10 µm to 25 µm per side. Stripping uses 3 wt% to 5 wt% NaOH at 50 °C to 60 °C in reciprocating spray stripping modules. Compliance references include ASTM E407 for microetching, ISO 9001:2015 Clause 8.5.1 for production control, ISO 13485:2016 for medical device components, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006. Terminal articles include precision encoder discs, surgical blades, battery current collector foils, metal shims, and fine filtration screens.
On copper alloy strip such as C19400, the etch sequence for QFN leadframes requires the dry film resist to survive long enough to define half-etched die pads and exposed leads while remaining removable without leaving carbonised residues on the plated finish. EtchMaster dry film photoresist is laminated on both sides of 0.127 mm to 0.254 mm copper strip at roll temperature 110 °C to 125 °C, line speed 1.0 m/min to 2.5 m/min, and pressure 4 bar to 6 bar. Film thickness is 38 µm for 0.127 mm strip and 50 µm for thicker strip. The addition-ratio equivalent for the developer is 0.9 wt% to 1.0 wt% Na₂CO₃·H₂O at 29 °C to 32 °C, pH 10.5 to 10.9, with breakpoint 50% to 60%. Exposure uses double-sided UV aligners at 60 mJ/cm² to 100 mJ/cm² with a top-bottom registration tolerance of ±12 µm. Etching uses cupric chloride at 140 g/L to 180 g/L CuCl₂·2H₂O, HCl 2.0 mol/L to 3.0 mol/L, redox 520 mV to 560 mV, temperature 48 °C to 52 °C, with spray oscillation at 80 rpm to 120 rpm. Stripping in 3 wt% to 5 wt% NaOH at 50 °C to 55 °C is specified before measurement of the half-etch depth; production-scale experience shows that incomplete stripping is more common on 42 Alloy than on C19400 because the lower thermal conductivity of 42 Alloy reduces local stripper temperature at the resist-metal interface. Published data for EtchMaster dry film on 42 Alloy leadframes is limited, and transfer from C19400 strip must be validated against the difference in thermal expansion and surface oxide character. Compliance is assessed under JEDEC JESD47I for package-level stress testing, ASTM B152/B152M for copper sheet and strip, IATF 16949:2016 Section 8.5.1 for automotive electronics production, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006. Terminal articles include QFN, DFN, SOP, and exposed-pad leadframe packages for power management ICs and microcontroller units.
For aperture grids with slot widths below 20 µm, the resist is exposed through a collimated UV source to maintain sidewall verticality and to prevent aperture broadening after ferric chloride spray etching. Invar 36 foil, SUS 304 stainless foil, and cold-rolled low-carbon steel are typical substrates for sacrificial metal masks and microsieves. EtchMaster dry film photoresist is laminated at roll temperature 100 °C to 120 °C, speed 0.4 m/min to 1.0 m/min, and pressure 4 bar to 6 bar; film thickness of 15 µm to 20 µm is selected for sub-20 µm slot geometry to reduce the resist aspect ratio and improve the etch factor. The developer addition-ratio equivalent is 0.6 wt% to 0.8 wt% Na₂CO₃·H₂O at 27 °C to 30 °C, with a slower breakpoint of 50% to 65% because thin resist requires longer rinse time at 1.0 bar to 1.4 bar. UV exposure is set to 90 mJ/cm² to 150 mJ/cm² using high-pressure mercury lamps; the dose-to-clear is measured with a Stouffer 41-step wedge and is held at 1.4 to 1.8 times the clear step. Etching is performed in ferric chloride at 35 °Baumé to 42 °Baumé, 40 °C to 50 °C, with reciprocating spray pressure 1.2 bar to 2.0 bar. Dimensional control for 15 µm to 20 µm features requires phototool compensation of 5 µm to 15 µm per side because undercut is asymmetric in vertically oscillated spray modules. Stripping uses 3 wt% to 4 wt% NaOH at 45 °C to 55 °C, followed by neutralisation in 5% citric acid for stainless steel substrates. Compliance references include ASTM E407, ISO 9001:2015 Clause 8.5.1, ISO 13485:2016 for medical-grade microsieves, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006. Terminal articles include OLED fine metal masks, solder paste stencils, microsieves for analytical instruments, and precision filter meshes.
Direct etch of thick copper power boards places a higher demand on resist adhesion than pattern plating because there is no electrolytic copper shell to reinforce the photoresist sidewall during impingement from high-pressure etch spray. For copper weights from 105 µm to 400 µm, EtchMaster dry film photoresist is specified at 50 µm or 75 µm thickness, with 75 µm film required on 210 µm and heavier copper to bridge the deep topography between conductors. Lamination uses a vacuum laminator with a 24 µm conformable top film at 110 °C to 125 °C, speed 0.3 m/min to 0.8 m/min, and two-pass lamination on 300 µm to 400 µm copper. Exposure on a 365 nm UV-LED printer is set to 120 mJ/cm² to 180 mJ/cm² for 75 µm film, with a post-exposure hold of 10 min to 15 min before development to stabilise crosslink density. The addition-ratio equivalent in the developer is 1.0 wt% to 1.1 wt% Na₂CO₃·H₂O at 30 °C to 33 °C, pH 10.7 to 11.1, with spray pressure 1.5 bar to 2.0 bar and breakpoint 45% to 55%. Etching uses alkaline cupric chloride at pH 8.4 to 8.8, free chloride 5.8 M to 6.2 M, redox 540 mV to 580 mV, temperature 50 °C to 54 °C, and a two-chamber etch module to limit dwell time. Etch factor on 210 µm copper is typically 1.5:1 to 2.0:1, requiring artwork compensation of 30 µm to 60 µm per side. Stripping uses 4 wt% to 6 wt% NaOH at 50 °C to 60 °C, with a residence time of 10 min to 20 min in a flood-strip chamber. Compliance is assessed under IPC-6012E Class 3 for thick-copper boards, IPC-2221 conductor sizing, IPC-A-600K, UL 94V-0, RoHS Directive 2011/65/EU Annex II, and REACH Regulation (EC) No 1907/2006. Terminal articles include IGBT drive boards, power inverter modules, battery protection boards, and bus bar interconnects for electric vehicle traction systems.
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DuPont EtchMaster dry film photoresist is an aqueous-processable, negative-acting acrylate-based photopolymer supplied as a dry laminate on a polyethylene terephthalate carrier film with a polyolefin cover sheet. The material is specified for print-and-etch inner layer patterning, through-hole tenting, and selective etch-resist formation on rigid and flexible copper-clad laminates. Because the film is applied by hot-roll lamination rather than slot-die or curtain coating, the dry film format avoids solvent evaporation, edge bead, and viscosity drift associated with liquid photoresists. Thickness selection is made according to etch chemistry and copper weight; production thicknesses for dry film etch resists in this category are typically 20 µm to 50 µm, but exact EtchMaster catalog codes, roll widths, and carrier film specifications should be verified against the supplier datasheet. The product is positioned for cupric chloride and ammoniacal alkaline etching; published data for this specific configuration is limited and line qualification remains necessary.
Film construction is standard tri-layer: a polyethylene terephthalate carrier film of 19 µm to 25 µm, the photopolymer layer, and a polyolefin cover sheet of 25 µm to 35 µm. The cover sheet is removed immediately before lamination, while the carrier film remains over the resist during exposure and is peeled before development. Humidity during storage above 60% is controlled; moisture uptake in the acrylic matrix lowers glass transition temperature and can alter exposure speed.
Table 1 lists the principal directives and test methods used for incoming and in-process control of aqueous dry film photoresists. Conformity of the specific EtchMaster formulation must be confirmed against the supplier’s current certificate for each batch.
| Standard or directive | Scope | Verification notes |
|---|---|---|
| RoHS Directive 2011/65/EU Annex II | Restriction of hazardous substances in electrical and electronic equipment | Supplier declaration for cadmium, lead, mercury, hexavalent chromium, PBB, PBDE, and phthalates |
| REACH Regulation (EC) No 1907/2006 Annex XVII | Restrictions on chemical substances | Verify SVHC content above 0.1% by mass |
| ISO 9001:2015 Clause 8.5 | Control of production and service provision | Release of lamination, exposure, and development process parameters |
| ASTM D3359-17 | Cross-hatch tape adhesion test | Used after development for resist adhesion on copper; acceptance commonly 4B or 5B |
| ISO 2409:2020 | Cross-cut adhesion test | Equivalent method for coated surfaces |
| DIN EN ISO 2808:2019 | Coating thickness measurement | Cross-section or gravimetric verification of dry film thickness |
On conveyorized exposure systems fitted with 5 kW or 7 kW metal halide lamps, the unfiltered 365 nm dose required for 25 µm to 30 µm dry films is typically held between 35 mJ/cm² and 80 mJ/cm², depending on artwork density and film thickness. A Stouffer 41-step wedge response of 6 clear steps to 9 clear steps is commonly used as a production control; fewer clear steps indicate underexposure and low copper adhesion, while higher clear-step counts may close 40 µm to 50 µm channels. Resolution for a 25 µm film is commonly 40 µm line/space under vacuum contact, though the specific EtchMaster resolution should be confirmed with the manufacturer’s optical line test.
Development is carried out in a 0.85% to 1.1% by mass anhydrous sodium carbonate solution at 28°C to 32°C, with sump pH 10.4 to 10.9 and conveyor breakpoint 45% to 60%. The developer sump temperature must be controlled within ±5°C of the established setpoint; larger excursions accelerate acrylate matrix dissolution and produce resist foot undercut or sidewall notching. Adhesion to copper is evaluated after development by ASTM D3359-17 cross-hatch tape test, with 4B or 5B classification accepted for production. Surface roughness of the copper is measured according to ISO 4287:1997; Rz values between 1.5 µm and 3.0 µm are typical after chemical microetch or pumice treatment. Smooth rolled copper below Rz 1.0 µm may show adhesion failure at the resist-copper interface after cupric chloride etching.
Exposure energy per panel is verified with a radiometer calibrated to a 365 nm probe. Lamp aging that reduces output by more than 15% from baseline requires either conveyor speed adjustment or lamp replacement. Vacuum frame contact is preferred over non-vacuum contact because air gaps of 5 µm to 15 µm between artwork and resist can degrade line edge reproduction in 50 µm features. Increasing film thickness from 25 µm to 40 µm commonly increases the required dose by 15% to 30%. A collimated LED source at 405 nm with a 50 mJ/cm² dose and a 10° half-angle may produce straighter sidewalls than a non-collimated metal halide source; however, dry film formulations optimized for 365 nm exposure may show lower sensitivity at 405 nm.
A mixed inner-layer and outer-layer production line with a 1,600 mm working-width conveyorized etcher and a 1,250 mm hot-roll laminator typically exhibits resist lifting at the laminate surface at copper areas where the persulfate or hydrogen peroxide–sulfuric microetch was exhausted below 0.5 µm to 1.0 µm removal. Lamination is performed at roll temperatures of 105°C to 120°C, conveyor speed 1.0 m/min to 2.5 m/min, and nip pressure 2.5 kg/cm² to 5.0 kg/cm². Insufficient nip pressure leaves entrapped air at the copper surface, creating channels for etchant penetration and line widening. Excessive roll temperature above 125°C promotes premature thermal crosslinking in the acrylate matrix and can reduce the solubility of the film in the later stripping step. Panel preheat at 60°C to 80°C is used on some lines to reduce thermal shock and improve conformability over heavy copper. Air entrapment and resist footprint defects are observed as scalloped line edges under 100× microscope inspection.
Acrylate-based dry films exhibit different adhesion behavior in acidic cupric chloride–HCl and ammoniacal alkaline etchants. In cupric chloride at 48°C to 52°C and 2.0 bar to 3.0 bar spray pressure, the EtchMaster film is specified to resist undercut on 18 µm and 35 µm copper foils; however, line qualification is required because the specific etching factor depends on conveyor speed, copper thickness, and etch chemistry. When an ammoniacal alkaline etchant at pH 8.5 to 9.5 and 50°C to 54°C is substituted for cupric chloride, adhesion loss at the resist-copper interface is a known failure mode if the panel enters the etcher with residual carbonate developer salts or if the copper surface was not fully microetched. Alkaline etchants also increase the rate of top-surface resist softening; spray pressure is therefore reduced to the lower end of the equipment range and the etch time is limited to the minimum required for complete copper removal. Published data for the EtchMaster formulation under this specific contrast between cupric chloride and alkaline etching is limited; a controlled etch-rate panel test with 0.3 mm and 0.5 mm line/space test coupons is recommended before full production release.
The etch factor, defined as copper penetration depth divided by lateral undercut, is typically maintained above 2.5 for 35 µm copper when cupric chloride pH is controlled between 0.5 and 1.0 and free hydrochloric acid is held at 2.0 N to 3.5 N. Specific gravity of the etchant is maintained at 1.280 to 1.330, and oxidation-reduction potential is held at 520 mV to 580 mV versus Ag/AgCl. Exceeding 600 mV accelerates sideways undercut and can attack the resist edge. In alkaline etching, pH and copper concentration control are critical because copper precipitation at pH above 9.8 can plug spray nozzles and create uneven etching. Lower etch factors below 2.0 increase line-width loss and reduce process capability for 75 µm line/space inner layers.
Resist removal after etching uses a 3% to 5% by mass sodium hydroxide solution at 45°C to 55°C with 1.0 bar to 2.0 bar spray pressure. Stripping time is typically 30 s to 90 s for 30 µm film. Stripper pH below 12 or temperature below 40°C can leave residual acrylate particles on the copper surface, which are detected as red or brown staining in post-strip inspection. The stripped film fragments are removed by 0.5 mm slot filters; if the stripping bath is not filtered, re-deposited resist particles can block the etch rinse nozzles in subsequent panels. Spent stripper containing dissolved acrylate solids is treated by acid precipitation at pH 2.5 to 3.5 before filtration. Direct discharge without pH neutralization is not permitted.
The product is not recommended for direct laser ablation imaging because the acrylate matrix absorbs at 355 nm and can form carbonaceous residues; published data for the EtchMaster film under UV laser direct imaging at 355 nm is limited. EtchMaster is not specified for use in nickel/gold plating resists with highly alkaline cyanide baths because the acrylate network swells at pH above 13 and may lose adhesion. The resist is also incompatible with prolonged immersion in methylene chloride-based solvent cleaners, which dissolve the photopolymer. For horizontal conveyorized lines, the film should not be processed with developer impingement pressures above 2.5 bar, which can cause resist lifting at narrow line ends.
Compared with solvent-processable dry films, EtchMaster eliminates hydrocarbon developer and stripper handling and is suitable for aqueous-only printed circuit board fabrication lines. Relative to liquid photoresists, dry film provides a fixed thickness across surface topography and can tent through-holes larger than 0.5 mm without capillary thinning. Dry film lamination yields thickness uniformity of ±1 µm to ±3 µm across a 500 mm panel, while liquid coating can vary by ±5 µm near panel edges. However, dry film lamination requires a clean, flat panel surface; pits, scratches, and woven glass protrusion reduce conformability and can create local etch channels. The main operational difference from older solvent-based dry films is the aqueous sodium carbonate development step, which requires pH and total alkalinity control rather than solvent replenishment. Compared with high-resolution liquid resists used in semiadditive processing, a 25 µm dry film typically exhibits lower resolution and is specified for subtractive etch and tent-and-etch routes rather than sub-30 µm line/space pattern plating. Tenting reliability for through-holes up to 2.0 mm diameter with 30 µm film should be validated by thermal stress testing per IPC-TM-650 2.6.8.
Flexible polyimide circuits require lamination temperatures lowered to 95°C to 105°C to minimize polyimide distortion, and the cover sheet removal tension is adjusted to prevent resist stretching. The film should be stored at 5°C to 25°C and allowed to reach room temperature before lamination; condensation at relative humidity above 60% can form blisters at the resist-copper interface. Shelf life for dry film photoresists is commonly 6 months to 12 months in unopened, light-tight packaging. Exact EtchMaster shelf life, batch certificates, and defined storage tolerances should be obtained from the supplier for the specific roll code and thickness selected.
