| HS Code | 569037 |
| Product Name | PCB Hole Metallization Solution (MacDermid Hole Metallization Special Solution) Electronic/EL Grade |
| Product Type | Aqueous chemical solution for electroless copper deposition in PCB through-hole metallization |
| Manufacturer | MacDermid, Inc. / Element Solutions |
| Grade | Electronic/EL Grade |
| Physical State | Liquid |
| Appearance | Clear to slightly hazy liquid |
| Color | Blue to dark blue |
| Odor | Mild characteristic formaldehyde/amine-like odor |
| Ph | Strongly alkaline, typically greater than 12 |
| Specific Gravity | 1.05 to 1.10 at 25°C |
| Boiling Point | Approximately 100°C |
| Melting Freezing Point | Approximately 0°C |
| Solubility In Water | Completely miscible |
| Stability | Stable under recommended storage conditions; avoid contact with acids and strong oxidizers |
| Storage Temperature | 10°C to 30°C in tightly closed containers |
| Chemical Composition | Proprietary mixture containing copper salts, complexing agents, alkali hydroxide, formaldehyde/formaldehyde donor, and stabilizers |
As an accredited PCB Hole Metallization Solution (MacDermid Hole Metallization Special Solution) Electronic/EL Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaging: 1 L HDPE bottle of MacDermid Hole Metallization Special Solution, Electronic/EL grade, for PCB through-hole plating. |
| Container Loading (20′ FCL) | 20′ FCL: PCB Hole Metallization Solution in sealed, palletized drums, secured with bracing, protected from sunlight, moisture, and damage during transit. |
| Shipping | This electronic-grade chemical solution requires careful shipping. Transport in sealed, corrosion-resistant containers with proper hazardous material labeling and documentation. Comply with all applicable transport regulations. Avoid extreme temperatures and physical damage. Include safety data sheet and spill containment provisions to ensure safe, compliant delivery. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and incompatible materials such as strong acids or oxidizers. Keep the original container tightly sealed when not in use to prevent contamination and evaporation. Avoid freezing, and maintain temperatures between 15–30°C (59–86°F). Ensure secondary containment and clear labeling. |
| Shelf Life | Shelf life is typically six months when stored unopened in original containers at controlled room temperature, protected from heat, light, and contamination. |
Deployment of the electronic/EL grade MacDermid Hole Metallization Special Solution begins after post-drill inspection and desmear acceptance. The solution is not a desmear substitute and is not applied as a final conductor. Its function is to form a conductive seed layer on exposed resin, glass, and plasma-treated films before electrolytic copper deposition. The bath is an alkaline aqueous process solution with controls for temperature, pH, agitation, filtration, and replenishment based on panel throughput and bath analysis. In each downstream segment, the operating window shifts because laminate type, hole aspect ratio, dielectric wetting, and final acceptance class change the required seed thickness and the risk of gas entrapment. The following application splits describe the process logic for HDI, automotive, backplane, package substrate, flex, and RF/high-speed digital substrates.
In HDI multilayer boards, laser-drilled blind microvias of 75–100 µm diameter and 40–75 µm depth are the primary interconnect feature. The solution is used after UV laser ablation, which leaves carbonized resin and glass debris. Alkaline permanganate desmear at 70–80 °C for 4–8 min removes 0.3–0.8 µm of dielectric, followed by a neutralizer and rinse. The hole metallization bath is maintained at 32–36 °C, pH 12.4–12.8, cupric ion at 2.8–3.2 g/L, formaldehyde at 4.5–5.5 g/L, and complexing agent at 30–40 g/L. Panels are processed for 12–16 min to deposit a seed layer of 0.3–0.5 µm. Panel loading is limited to 1.5 dm²/L to prevent local cupric ion depletion. In horizontal conveyorized equipment, panel transport is set at 0.5–1.0 m/s and the bath is filtered continuously through 10 µm polypropylene depth cartridges. The primary failure mode in this segment is void formation at the via bottom caused by insufficient solution exchange and hydrogen bubble retention. Bath temperature above 38 °C accelerates deposition but destabilizes the complex and increases gas evolution; operation below 30 °C reduces seed coverage on glass fibers. After seed deposition, electrolytic copper fills the blind via and a leveling copper cap is plated for via-in-pad structures. Terminal HDI products include smartphone mainboards and 0.4 mm pitch BGA substrates. Acceptance is per IPC-6012 Class 3, with solder float at 288 °C. RoHS 2011/65/EU and REACH 1907/2006 obligations apply to the bath chemistry and the finished laminate.
Automotive engine control unit and industrial I/O substrates place a different demand on hole wall preparation because the laminate is mechanically drilled FR-4 with a thickness of 2.4–3.2 mm. Through-holes of 0.25–0.35 mm diameter carry more drill smear than laser vias, so alkaline permanganate desmear is extended to 80–85 °C for 8–12 min and removes 0.8–1.5 µm of resin. The hole metallization bath is run at 30–32 °C for 15–18 min to slow the deposition rate and improve conformality on rough hole walls. The pH is maintained at 12.2–12.6 because a higher pH releases more hydrogen and reduces bath stability. Replenishment on production lines is tied to processed area and measured bath parameters: a proportioning pump adds 0.2–0.4 L make-up per 1 m² of processed panel, and automatic titration records cupric ion, formaldehyde, and sodium hydroxide every 30 min. Air sparging is kept at 0.5–1.0 L/min per bath liter. The electronic/EL grade formulation controls sodium, chloride, and trace copper particulate to keep final ionic contamination below 1.56 µg/cm² NaCl equivalent. Finished ECU, ABS control, and PLC boards are qualified by IPC-TM-650 2.6.8 thermal stress and IPC-6012 Class 3. A boundary condition applies: thermal cycling from -40 °C to +125 °C requires the seed layer to remain continuous through thermal expansion of the Z-axis. If the bath is aged beyond the supplier-defined metal turnover, seed coverage at the resin-glass interface becomes discontinuous and post-solder interconnect microcracking appears. This segment is therefore controlled by bath age and turnover limits, not only by temperature.
Mass transport, not bath age, limits backplane through-hole processing. For 0.25 mm holes in 3.0–4.5 mm thick backplane laminates, the aspect ratio reaches 10:1–15:1. The hole metallization solution must exchange inside the hole against hydrogen gas generated by the electroless reaction. Conventional air sparging is insufficient; vertical process tanks are fitted with mechanical reciprocating agitation at 20–40 cycles/min and a stroke of 30–50 mm. The bath is operated at 33–36 °C and pH 12.5–12.9 with a contact time of 18–22 min. The resulting seed thickness is 0.4–0.8 µm, which is lower than expected from flat-surface deposition because diffusion limitation inside the hole reduces the local copper ion supply. The control window is narrow: ±0.2 pH and ±2 °C. Operation above this window creates nodular deposits at the hole mouth and reduces coverage at the center; operation below it leaves exposed glass fiber. Replenishment is continuous, split into two streams: copper salt complex and aldehyde/alkali replenisher. The two are never premixed at high concentration because high local pH and copper concentration trigger homogeneous nucleation. Filtration uses 5 µm depth filters at 1–2 tank volumes/h. A post-seed dip in 2–5 % sulfuric acid removes alkaline solution before acid copper. The terminal products are test and measurement backplanes and 4G/5G baseband switch cards. Qualification requires IPC-6012 Class 3 and IPC-TM-650 2.6.8 thermal shock. For aspect ratios above 12:1, published data for this specific configuration is limited; cross-section coverage of at least five holes per panel edge and center is required before lot release.
| Downstream class | Substrate/feature | Pre-treatment | Solution temperature | Immersion time | Seed film thickness | Primary process conflict |
|---|---|---|---|---|---|---|
| HDI multilayer | RCC / 106 glass; 75–100 µm blind vias | Alkaline permanganate 70–80 °C, 4–8 min | 32–36 °C | 12–16 min | 0.3–0.5 µm | Blind via bottom voiding |
| Automotive / industrial | FR-4 2.4–3.2 mm; 0.25–0.35 mm through-holes | Alkaline permanganate 80–85 °C, 8–12 min | 30–32 °C | 15–18 min | 0.3–0.5 µm | Z-axis thermal expansion and seed cracking |
| High-aspect-ratio backplane | 0.25 mm holes / 3.0–4.5 mm board | Desmear plus mechanical agitation | 33–36 °C | 18–22 min | 0.4–0.8 µm | Hydrogen gas retention and mass transport |
| IC package substrate | Build-up film; 40–60 µm vias | Plasma or short wet etch | 28–30 °C | 8–12 min | 0.2–0.4 µm | Dielectric surface roughening |
| Flex / rigid-flex | Polyimide 25–50 µm core | O₂/CF₄ plasma 80–100 °C | 25–28 °C | 6–10 min | 0.2–0.3 µm | Swell / wicking / blistering |
| RF / high-speed | PTFE / PPO; 0.3 mm vias | Plasma or sodium surface activation | 34–38 °C | 14–18 min | 0.3–0.5 µm | Low surface energy and skip plating |
For package substrate formats below 50 µm line/space, blind microvias of 40–60 µm diameter are ablated into build-up film or epoxy-based dielectrics. The hole metallization solution is kept at 28–30 °C and pH 12.0–12.4 for 8–12 min, producing only 0.2–0.4 µm seed. The reduced pH and temperature window protects the dielectric surface from excessive alkaline attack, which would raise roughness and compromise fine-line adhesion. The deposition rate is controlled at 0.02–0.04 µm/min. Horizontal equipment with circulation of 1.5–2.0 m/s is preferred because direct impingement prevents cupric ion depletion at the via bottom. Ultrafiltration below 0.2 µm removes colloidal copper nuclei that could deposit as nodules on fine traces. Panel loading is limited to 0.8 dm²/L. After seed formation, semi-additive processing electroplates 12–18 µm copper traces and fills microvias. Final package substrates include flip chip CSP and BGA interposers. Qualification follows IPC-6012 Class 2 or Class 3 as specified by the assembly OSAT, and RoHS 2011/65/EU plus REACH 1907/2006 batch declarations accompany the solution. The process window is among the narrowest in the downstream matrix: a temperature rise of +2 °C can increase deposition rate enough to bridge dielectric sidewalls, causing final trace adhesion failures.
Polyimide flex and rigid-flex substrates absorb electrolyte and swell in highly alkaline media. The hole metallization solution is run at 25–28 °C with a reduced hydroxide concentration of 6–8 g/L and a contact time of 6–10 min. These conditions produce a seed thickness of 0.2–0.3 µm, which is sufficient because the subsequent electrolytic copper layer carries the circuit current. Exposed acrylic adhesive and coverlay cut edges can wick solution and create blistering after solder reflow; therefore the process uses plasma desmear at 80–100 °C in O₂/CF₄ for adhesive-containing flex stacks instead of wet alkaline permanganate. The plasma-cleaned polyimide surface is wetted directly by the solution without high caustic. Horizontal equipment is set to 0.5–1.0 m/s panel transport to minimize tensile stress on thin 25–50 µm polyimide cores. Filtration at 10 µm removes particulate that could deposit between the hole wall and subsequent electrolytic copper. Finished rigid-flex boards are qualified by IPC-TM-650 2.6.8 thermal stress and IPC-6013 Class 3 flexural endurance. The main incompatibility is wet alkaline permanganate on exposed acrylic: the resulting porous surface retains solution and yields post-lamination blisters during reflow at 260 °C. Process records must confirm which desmear route was used before the hole metallization bath is started.
| Mandate / standard | Designation | Relevant parameter | Acceptance condition |
|---|---|---|---|
| IPC | IPC-6012 Class 3 | Thermal stress and hole wall coverage | No interconnect defect after 288 °C float |
| IPC-TM-650 | 2.6.8 | Solder float | No delamination, void, or copper separation |
| IPC | IPC-6013 Class 3 | Flexural endurance | No conductor failure after flex cycles |
| RoHS | 2011/65/EU | Homogeneous material restrictions | Pb, Hg, Cd, Cr VI below Annex II limits |
| REACH | 1907/2006 | SVHC declaration | Batch certificate required |
| UL | 94 V-0 | Flammability | Finished laminate rating |
After plasma or sodium-based surface activation raises the critical surface tension above 40 mN/m, the hole metallization solution is introduced to RF and high-speed digital laminates. PTFE, hydrocarbon ceramic, and polyphenylene oxide substrates present low surface energy and require the hole wall to be wetted before seed formation. In a typical RF board process, the panel passes through plasma treatment, then a conditioner at 40–55 °C for 5 min, then the hole metallization bath at 34–38 °C for 14–18 min. The higher operating temperature is applied because the exposed walls have no bulk glass fiber at the surface, but it increases the risk of foam from entrained wetting agents. Slow board entry and 10 µm depth filtration limit air pocket formation at the via mouth. Deposition is inspected at 100× cross-section for continuous coverage. A typical 0.3 mm via in a 77 GHz radar board requires uninterrupted seed coverage along the PTFE wall to maintain the ground return path. After electrolytic copper, the finished product is a 77 GHz automotive radar antenna, 112 Gbps backplane board, or RF switch card. Compliance is evaluated under IPC-6012 Class 2 or Class 3; high-frequency boards are additionally tested for insertion loss and VSWR because DC continuity alone does not confirm signal integrity. RoHS 2011/65/EU and UL 94 V-0 material ignitability ratings apply to the finished plank. The solution must not be used without prior surface activation on PTFE; otherwise the low surface energy yields skip plating in the hole wall and intermittent ground plane contact.
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MacDermid Hole Metallization Special Solution Electronic/EL Grade is an aqueous carbon dispersion used as a direct-metallization seed layer for printed circuit board through-holes, laser-formed microvias, and blind-via structures. The fluid contains a stabilized conductive carbon pigment suspended in an alkaline carrier; the Electronic/EL Grade designation defines a low-trace-metal chemical package for electronics manufacturing, not an electroless copper or palladium bath. The product is applied after desmear and conditioning operations, coats the exposed dielectric wall, and after drying produces a continuous conductive carbon film suitable for subsequent acid copper electroplating. Because the formulation does not contain formaldehyde, tartrate, or copper complexing agents, it differs from classical electroless copper seed chemistries in both waste profile and process control. Model identification is typically limited to the Electronic/EL Grade suffix; no separate numeric model code appears in current commercial trade documentation. The working bath is operated in either horizontal conveyorized modules or vertical basket lines, with solution contact time and drying adjusted to panel thickness and via aspect ratio.
Electroless copper deposition relies on a formalin-based reducing agent, a strongly alkaline environment near pH 12.0–12.8, and complexants such as EDTA or quadrol to hold copper in solution. The carbon dispersion operates in the pH range of 10.0–11.5 and requires no copper complexants, no palladium activator, and no formaldehyde. Seed-layer formation is therefore a physical coating and drying sequence rather than an autocatalytic metal reduction. The copper thickness produced by electroless copper typically ranges from 0.3 µm to 1.0 µm, whereas the carbon film is not a metal deposit and is controlled by film coverage and sheet resistance rather than thickness. Production lines using the carbon dispersion eliminate the separate palladium activator tank and reduce alkaline copper waste, but introduce a drying step between coating and microetching. The conductive carbon film must be removed from exposed copper lands by a microetch before electroplating, because it is not selective to dielectric and no catalyzed copper-to-copper continuity is formed by the bath itself.
| Parameter | Carbon direct metallization | Electroless copper | Palladium-based direct metallization |
|---|---|---|---|
| Reducing agent | None | Formaldehyde, typically 1.5–3.0 g/L | None or proprietary |
| Operating pH | 10.0–11.5 | 12.0–12.8 | Varies, acidic to neutral |
| Deposition or coating nature | Carbon film | Metallic copper | Palladium/carbon film |
| Waste load | No copper-EDTA waste | Copper-EDTA and formaldehyde | Palladium-containing waste |
| Typical throughput | Horizontal dry-to-dry, 30–90 s immersion | Vertical or horizontal, 10–30 min bath residence | Horizontal, 30–120 s immersion |
For mixed FR-4, high-Tg FR-4, and polyimide panel loading, the working dispersion is maintained with deionized water having a resistivity of ≥ 1 MΩ·cm at 25 °C; makeup water with hardness above 100 mg/L as CaCO₃ can destabilize the carbon particles and increase filtration pressure. The bath is run at 20–28 °C, with control often set at 24 °C, and pH is held between 10.0 and 11.5 by a pH controller using an alkali feed. Brookfield rotational viscosity measured per ASTM D2196-20 remains below 30 mPa·s at 25 °C; values above 50 mPa·s indicate particle agglomeration or excessive drag-in of conditioner. Immersion time in horizontal equipment is typically 30–90 s, while vertical basket processing uses 2–5 min depending on hole diameter and panel stack. Drying temperature at the final air knife stage is held between 80 °C and 95 °C; incomplete drying leaves residual water that can reduce electroplating adhesion, while excessive local heating above 100 °C can over-cure the carbon film and decrease microetch removal. Tank materials include polypropylene, polyethylene, or 316L stainless steel; titanium is avoided in working tanks to prevent galvanic issues with copper racks, and pumps use sealless polypropylene or polyvinylidene fluoride construction.
High-aspect-ratio boards present two opposing demands: the dispersion must penetrate narrow vias without leaving voids, yet the dried film must remain conductive enough to initiate copper plating from the via center. The carbon dispersion is engineered with a shear-thinning rheology; under low-shear conditions, viscosity increases to hold the fluid in the via during draining, while under flood-bar or pump shear, viscosity drops for uniform wetting. For this product class, particle size distribution is controlled with a D90 below 1.0 µm as verified by laser diffraction per ISO 13320-1; oversized agglomerates are removed by in-line bag filters rated at 5–10 µm followed by polypropylene depth cartridges. Through-hole coverage is evaluated after drying using a four-point probe or production current ramp test, not by film thickness. On high-aspect-ratio test coupons, post-dried through-hole resistance is measured after 10 min stabilization at room temperature; published data for this specific product formulation is limited, so each line establishes a go/no-go resistance value against board thickness and hole diameter. Process failures on vertical lines include carbon pooling at the lower via edge when drain time is too short, and dry film bridging across the hole opening when air knife velocity exceeds the fluid drainage rate.
On horizontal conveyorized lines, the solution is delivered through flood bars and squeegee rollers in a dry-to-dry sequence: conditioning, rinsing, carbon dispersion immersion, air-knife removal, and convection drying. Drag-out from the dispersion tank reports immediately downstream in the first rinse; suspended carbon in that rinse must be filtered continuously at a rate equal to at least 1–2 tank turnovers per hour to prevent redeposition on copper lands. Rinse water conductivity is monitored, and cascade flow is adjusted so that the final rinse does not exceed 50 µS/cm above incoming DI water. A production-scale failure mode observed on some horizontal modules is foam accumulation in the recirculation weir when the line speed exceeds the degassing capacity of the carbon bath; anti-foam additions are not made without supplier approval because hydrophobic defoamer can deposit on hole walls and lower plating adhesion. The microetch station following drying uses sodium persulfate or cupric chloride chemistry, but the exact etch depth is set to remove carbon from copper without attacking the carbon film inside vias; typical etch depth on copper is 0.5–1.0 µm per pass. After microetching, panels proceed directly to acid copper electroplating, where the carbon film must withstand the high-current strike step.
Electronic/EL Grade formulations are controlled for extractable ionic residues because the carbon film remains in contact with the dielectric during subsequent electroplating and can contribute to surface insulation resistance losses if the film is not adequately dried and microetched. Under IPC-6012 testing for rigid PCBs, surface insulation resistance and electrochemical migration resistance are evaluated with IPC-TM-650 test methods; the exact resistivity limits depend on the board class and operating voltage. The product is designed to be formaldehyde-free and to contain no intentionally added lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers; compliance with Directive 2011/65/EU and Regulation (EC) No 1907/2006 should be verified against the current safety data sheet and supplier statement. Residual carbon in the base material must be removed from copper surfaces before soldermask application; otherwise, the carbon film can reduce soldermask adhesion and contribute to ionic contamination after hot air solder leveling.
| Requirement | Designation | Relevance to product use |
|---|---|---|
| Restriction of hazardous substances | Directive 2011/65/EU | No intentionally added restricted substances |
| Registration, evaluation, authorization of chemicals | Regulation (EC) No 1907/2006 | SVHC Candidate List review required |
| Rigid PCB performance | IPC-6012 | Thermal stress, continuity, and solderability after plating |
| Ionic cleanliness test methods | IPC-TM-650 | Surface insulation resistance and extract conductivity |
| Viscosity determination | ASTM D2196-20 | Brookfield rotational viscosity at 25 °C |
| Particle size analysis | ISO 13320-1 | Laser diffraction D90 control |
In mixed-material stacks containing polytetrafluoroethylene, ceramic-filled hydrocarbon, or low-loss dielectrics, plasma desmear or wet chemical desmear must produce a wettable via wall before the carbon dispersion is applied. The carbon solution does not compensate for poor smear removal; voids caused by incomplete desmear remain visible after electroplating as microvoids in the copper layer. High-frequency materials may require reduced drying temperature to avoid thermal damage to the dielectric; the dryer profile is then compensated with longer dwell time and lower air impingement. The dispersion is generally compatible with alkaline permanganate desmear residues if the conditioner and rinse sequence maintain pH separation; acid carryover from copper surface preparation can lower local pH and destabilize the carbon suspension. When processing flex or rigid-flex panels, the drying stage must not exceed the glass transition region of the coverlay adhesive; otherwise, adhesive softening can entrap carbon particles and create subsequent blistering during solder shock. Proper cleaning of the carbon bath is required before shutdown; dried carbon is difficult to redisperse and may require a heated alkaline cleaner plus mechanical scrubbing of tank surfaces.
Bath life is governed less by chemical depletion than by particle agglomeration and contamination drag-in. In-line filtration with 5–10 µm bag filters followed by depth cartridges removes rogue agglomerates, but excessive shear from high-pressure pumps can degrade particle size and reduce film coverage. Air agitation is used at low flow to keep carbon suspended without causing foam; eductor-driven recirculation is preferred in vertical tanks to minimize settling. Bath replenishment is based on pH, viscosity, and process solids, which are measured by gravimetric solids content per ASTM D2369 or by a calibrated densitometer. If solids content falls more than 10–15% from the new bath value, film resistivity increases and high-current strike plating can show skipping at the via mouth. If viscosity rises above the upper control limit, the bath is not diluted with water alone; dilution can reduce carbon solids below the deposition threshold. The supplier’s published data for this specific configuration is limited, so batch-to-batch solids and D90 values should be trended against line speed and hole coverage data to define the local control window. Replenishment is typically performed by adding the same Electronic/EL Grade concentrate to the working tank while filtering.
A representative process sequence places the carbon dispersion after alkaline permanganate desmear and conditioning, but before microetching and acid copper electroplating. Panels enter the dispersion bath at 20–28 °C, are drained and air-knifed to remove excess fluid, and then dried at 80–95 °C to fix the carbon film. The dried carbon remains on both copper lands and dielectric walls; the subsequent microetch removes carbon from copper surfaces while leaving the carbon film inside holes. After microetch and rinse, the panels are directly electroplated; no palladium activation is used. This flow eliminates the traditional electroless copper line and its formaldehyde air monitoring, but requires careful control of the drying and microetch stations. In production, hole wall coverage is verified by cross-sectioning after a test panel; IPC-A-600 acceptance criteria for plated through-holes apply to the final copper deposit. If the bath solids drift below the local control limit or the microetch depth is insufficient, voiding at the via corner and carbon residues under electrolytic copper are the typical failure points; these conditions are assessed by cross-section per IPC-A-600 before release of the plating line.
