| HS Code | 211551 |
| Breakdown Voltage | 530 V/µm |
| Volume Resistivity | 1e19 Ω·cm |
| Tensile Strength | 89 MPa |
| Elongation At Break | 6% |
| Young S Modulus | 2.9 GPa |
| Glass Transition Temperature | >350 °C |
| Coefficient Of Thermal Expansion | 52 ppm/°C |
| Cure Temperature | 250 °C |
| Photosensitivity | Negative-tone |
| Resolution | 2 µm |
| Viscosity | Variable by formulation |
| Moisture Absorption | <0.2% |
As an accredited Photosensitive BCB Resin for Wafer-Level Packaging Applications factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Packaged as 500 mL amber glass bottle, sealed under inert nitrogen, with tamper-evident cap and light-protective outer wrap. |
| Container Loading (20′ FCL) | One 20-foot container of photosensitive BCB resin, packed in drums, for wafer-level packaging applications. |
| Shipping | Ship photosensitive BCB resin in light-blocking, sealed containers under controlled temperature (2-8°C). Ensure proper hazardous material labeling, ventilation, and grounding during transport. Avoid exposure to UV light, moisture, and static. Use double containment with absorbent material. Comply with local regulations for chemical shipping. Handle with PPE to prevent skin contact. |
| Storage | Store at 2–8 °C in the original tightly sealed, opaque container. Protect from direct light, UV exposure, moisture, and heat. Do not freeze. Before use, allow the resin to warm slowly to room temperature to prevent condensation. Keep the container closed when not in use, avoid contamination, and store away from ignition sources and incompatible materials. Always observe the manufacturer’s expiration date. |
| Shelf Life | Shelf life is typically six months when stored refrigerated in original, unopened opaque containers, protected from light and moisture. |
In 300 mm fan-out wafer-level packaging of application processors and baseband devices, photosensitive benzocyclobutene is deposited onto reconstituted mold compound panels after through-mold via exposure of aluminum or copper pads. The first dielectric layer must planarize mold compound roughness, adhere simultaneously to epoxy mold compound and metal pads, and open 5–30 µm vias without cracking after cure. A 46 wt% solids mesitylene resin is diluted to 40 wt% solids by adding 15 parts by weight 1,3,5-trimethylbenzene per 100 parts by weight as-supplied solution; this gives a target post-cure single-coat thickness of 7–9 µm when spun at 1,800–2,800 rpm on a 300 mm open-bowl coater with a hotplate uniformity of ±1 °C. The production sequence comprises dispense, spin coating, edge-bead removal with mesitylene, soft bake at 95 °C for 120 s to reduce residual solvent below 5 wt%, i-line exposure at 365 nm with a dose of 250–450 mJ/cm², puddle development in Stoddard solvent for 45–90 s, and final cure at 250 °C for 60 min under nitrogen with O₂ below 20 ppm. The oven ramp rate is restrained to 4 °C/min until 180 °C to prevent solvent blistering inside vias and over mold-compound porosity. Field data from production lots show a 3σ thickness uniformity of ±0.4 µm across a 300 mm panel after edge-bead removal, but edge delamination recurs when mold compound absorbs more than 0.3 wt% moisture; a dehydration bake at 150 °C for 30 min is therefore mandatory when fab relative humidity exceeds 60%. After formation of the first via layer, Ti/Cu seed is sputtered, Cu redistribution lines are electroplated to 5–10 µm, the seed layer is etched, and a second photosensitive BCB layer is coated, exposed, developed, and cured as passivation. The terminal products are Cu RDL dielectric stacks in fan-out wafer-level packages for application processors, PMICs, RF transceivers, and multi-chip modules that require redistribution beyond the native pad pitch. Finished-package qualification references JEDEC J-STD-020E moisture sensitivity level 3, JESD22-A104E thermal cycling Condition N from −55 °C to 125 °C for 1,000 cycles, JESD22-B112 drop shock, and RoHS Recast 2011/65/EU Annex II for restricted substances. Cured dielectric films are also evaluated to UL 94 V-0 on FR4 coupons at final thickness.
| Property | Test method | Typical value or limiting criterion |
|---|---|---|
| Dielectric constant at 1 MHz | ASTM D150-22 | 2.65 ± 0.05 |
| Dissipation factor at 1 MHz | ASTM D150-22 | 0.002 maximum |
| Volume resistivity | ASTM D257-14 | >1 × 10¹⁹ Ω·cm |
| Breakdown strength | ASTM D149-20 | >300 V/µm |
| Tensile strength | ASTM D638-14 | 87 ± 7 MPa |
| Elongation at break | ASTM D638-14 | 8 ± 4% |
| Moisture absorption, 24 h | ASTM D570-22 | <0.2% |
| Cure shrinkage | Profilometry | <5% |
On 300 mm copper pillar bump lines serving flip-chip attachment without wire bonding, photosensitive BCB is applied over aluminum bond pads and cured before under-bump metallization. The film absorbs thermomechanical shear between the Cu pillar and low-k on-chip dielectrics while acting as a repassivation layer that defines the bump window. The coating solution is adjusted from 46 wt% solids to 40 wt% solids by adding 15 parts by weight mesitylene per 100 parts by weight stock; two sequential coats achieve a total cured thickness of 12–16 µm for pillar heights above 60 µm, while a single coat of 7–9 µm is used for pillar heights below 45 µm. Windows of 20–70 µm are opened over the Al pads, and sidewall angles after development are maintained at 55°–65° by balancing exposure dose and puddle time. Production hardware includes a 300 mm track coater/developer, an i-line stepper at 365 nm with an exposure dose of 200–500 mJ/cm², and a nitrogen box furnace. Soft bake at 100 °C for 120 s is followed directly by develop; no post-exposure bake is inserted because excess thermal crosslinking narrows the develop window and changes opening critical dimension. Final cure is 250 °C for 60 min in nitrogen with O₂ below 20 ppm and a ramp rate below 4 °C/min. A recurring batch-to-batch failure mode is dewetting at the Al pad edge when the aluminum surface is not pre-cleaned; a 200 W O₂ plasma desum after develop also shifts opening critical dimension by −1 to −2 µm and must be compensated in exposure. The terminal goods are Cu pillar bump wafers for application processors, power management ICs, Wi-Fi/Bluetooth combo chips, and RF front-end modules. Reliability qualification follows JEDEC JESD22-A104E thermal cycling Condition B from −55 °C to 125 °C for 1,000 cycles, JESD22-B110 mechanical shock, JESD22-B112 drop shock, and JEDEC J-STD-020E moisture sensitivity level 3. Package-level failure is defined as any delamination exceeding 0.05 mm from the bump edge in C-mode scanning acoustic microscopy. The primary processing boundary is that single coats above 18 µm generate entrained-solvent voids because the top surface crosslinks before the bulk solvent escapes; such thicknesses require two coats with intermediate soft bake, while films above 25 µm are outside the qualified window for standard i-line exposure because through-cure dose gradients produce scum at the resin/metal interface.
Photosensitive BCB serves as a low-k organic liner in through-silicon via structures for 2.5D interposers and stacked memory where the sidewall dielectric must insulate copper fill from the silicon substrate. The stock solution is diluted from 46 wt% to 30 wt% solids with 1,3,5-trimethylbenzene; the addition ratio is 53 parts by weight solvent per 100 parts by weight as-supplied resin. This viscosity reduction permits spray coating and vacuum-assisted spin coating into via diameters of 10–60 µm and depths of 50–120 µm. After Bosch etching and dilute HF sidewall cleaning, the diluted BCB is dispensed under vacuum to remove trapped air, followed by low-speed spin to remove field material and leave a sidewall film of 1–3 µm. Soft bake at 95 °C for 120 s on a nitrogen-purged hotplate reduces solvent content; front-side i-line exposure at 365 nm with 300–600 mJ/cm² crosslinks field and via-rim material, and spray development with Stoddard solvent clears unexposed material from via interiors. Final cure at 250 °C for 60 min in nitrogen with O₂ below 20 ppm produces a liner with a dielectric constant of 2.65 at 1 MHz and a dissipation factor of 0.002 at 1 MHz. Conformality is the limiting constraint: published data for photosensitive BCB liners in aspect ratios above 3:1 is limited, and production lots restrict the material to 2:1 or lower aspect ratios unless vacuum-assisted spray coating is qualified for the specific via critical dimension. Sidewall coverage below 1 µm has caused isolation loss between Cu fill and silicon sidewall after copper electroplating and chemical mechanical planarization. Terminal products include 2.5D silicon interposers, high-bandwidth memory stacks, and silicon bridge die for chiplet integration. Reliability evaluation references JEDEC JESD22-A104E thermal cycling Condition N from −55 °C to 125 °C for 1,000 cycles, JEDEC JESD22-A102C autoclave at 121 °C and 100% relative humidity for 96 h, and JEDEC J-STD-020E moisture sensitivity level 3. An explicit incompatibility is that amine-containing CMP slurries and resist strippers can swell or plasticize uncured BCB; after via reveal, solvent residues above 3 wt% measured by thermogravimetric desorption are also unacceptable because they generate outgassing voids during subsequent solder reflow.
In MEMS and sensor wafer-level packaging, photosensitive BCB is patterned as a thin bond ring because cured films provide low moisture absorption and adhesion to silicon, glass, and ceramic cap wafers under thermal compression. The material is used at 45–50 wt% solids in mesitylene without dilution for bond rings of 5–15 µm final thickness; for sub-5 µm bond lines, a 50 wt% stock is diluted to 40 wt% solids by adding 25 parts by weight solvent per 100 parts by weight stock. The flow includes a 150 °C dehydration bake for 30 min, spin coating at 2,000–4,000 rpm, soft bake at 95 °C for 120 s, i-line exposure through a bond-ring mask at 300–700 mJ/cm², puddle development with Stoddard solvent, and a partial cure at 200 °C for 20 min in nitrogen. Partial cure retains reactive sites for wafer-to-wafer bonding while allowing enough reflow to planarize cap wafer topography. Alignment and bonding are performed in an EVG or SUSS wafer bonder at 0.5–2.0 MPa, followed by ramping to 250 °C for 60 min under nitrogen at 4 °C/min. Production failure signatures include non-uniform bond line thickness when ring height varies by more than ±0.5 µm across a 200 mm wafer, and voids when the partially cured film absorbs atmospheric moisture before bonding; a dry nitrogen storage queue and bonding within 8 h of partial cure are specified. The terminal devices are CMOS image sensors, MEMS accelerometers, gyroscopes, pressure sensors, and silicon microphones in wafer-level chip-scale packages. Qualification is performed against MIL-STD-883K Method 5011.7 for polymeric material acceptance, JEDEC JESD22-A102C autoclave at 121 °C and 100% relative humidity for 96 h, and JEDEC J-STD-020E moisture sensitivity level 3. Stoddard solvent and mesitylene residues in the bond ring are controlled below 0.5 wt% by thermal desorption; higher residues reduce cap wafer adhesion and appear as bond line delamination after autoclave.
Photosensitive BCB is introduced as an interlayer dielectric for antenna-in-package and mmWave front-end modules where spin-on glass has excessive loss or moisture-induced drift. The stock resin at 46 wt% solids is diluted to 38 wt% solids by adding 21 parts by weight mesitylene per 100 parts by weight stock; target cured thickness is 10 ± 0.5 µm. The film is spin coated on high-resistivity silicon or glass carriers, soft baked at 95 °C for 120 s, exposed with i-line at 365 nm at 300–700 mJ/cm², puddle developed in Stoddard solvent, and cured at 250 °C for 60 min under nitrogen with O₂ below 20 ppm. After cure, adhesion layers and gold or copper metallization are deposited by sputtering and electroplating; feature impedance is measured by vector network analyzer with ground-signal-ground probes and correlated to the film thickness and dielectric constant. The low-frequency dielectric constant is measured by ASTM D150-22 as 2.65 at 1 MHz; mmWave loss tangent must be confirmed for each stack by split-post dielectric resonator or microstrip ring resonator methods because published values for specific multilayer configurations at 28 GHz and 39 GHz are limited. BCB replaces spin-on glass primarily where the process cannot tolerate alkaline cure shrinkage or where the module requires a planarizing dielectric under thick copper pillars. The production boundary is that BCB has higher solvent retention than spin-on glass; edge bead removal and a 2 mm edge exclusion are mandatory to prevent edge spikes that alter inserted impedance. Terminal products include antenna-in-package modules, 5G mmWave front-end modules, automotive radar modules, and integrated passive couplers/filters. Compliance for finished modules references JEDEC J-STD-020E moisture sensitivity level 3, JESD22-A104E thermal cycling Condition B from −55 °C to 125 °C for 1,000 cycles, RoHS Recast 2011/65/EU Annex II, and REACH Regulation EC 1907/2006 Annex XVII restrictions. Cured film degradation above 350 °C in air makes this material unsuitable for final assembly steps requiring continuous operation above that temperature.
Wafer-level packaging of backside-illuminated CMOS image sensors uses photosensitive BCB as a planarizing spacer and passivation layer between the silicon device wafer and glass carrier. The 46 wt% solids stock is diluted to 42 wt% solids by adding 9.5 parts by weight mesitylene per 100 parts by weight stock; the target cured thickness for a single coat is 10–15 µm, and a two-coat process with one final cure is used for 20–25 µm spacers required for microlens clearance. The sequence includes dehydration bake at 150 °C for 30 min, spin coating at 1,500–3,000 rpm, soft bake at 100 °C for 120 s, i-line exposure at 365 nm with 400–700 mJ/cm², puddle development in Stoddard solvent, and final cure at 250 °C for 60 min under nitrogen at a ramp rate of 4 °C/min. Outgassing is controlled by ASTM E595-15; after 24 h at 125 °C under vacuum, total mass loss must be below 0.1%, and collected volatile condensable material must be below 0.01%, otherwise condensate deposits on microlenses and reduces module image quality. Field data from production lots show that wafers exposed to relative humidity above 60% before cure can trap water and form bubbles at 250 °C; a dehydration bake is mandatory. The terminal products are 8–50 MP smartphone camera modules, automotive surround-view cameras, and industrial machine vision sensors in wafer-level chip-scale packages. Reliability testing references JEDEC J-STD-020E moisture sensitivity level 3, JESD22-A104E thermal cycling Condition N from −55 °C to 125 °C for 1,000 cycles, and JESD22-A102C autoclave at 121 °C and 100% relative humidity for 96 h. The operational boundary is that residual Stoddard solvent above 0.5 wt% in thick films causes cavity pressure changes and glass carrier warpage after reflow; solvent retention is therefore monitored by thermal desorption on a per-lot basis.
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Photosensitive benzocyclobutene resin is supplied as a negative-acting, solvent-borne dielectric coating for redistribution layers, stress-buffer films, and die-to-wafer adhesive interfaces in wafer-level packaging. The Cyclotene 4000-series grades—including 3022-35, 4024-40, and 4026-46—contain a BCB polymer system with a photosensitive additive package; the suffix denotes nominal percent solids in the coating solution. On a 300 mm cassette-to-cassette wafer track with dynamic dispense, the material is coated, pre-baked, exposed with broadband i-line radiation, developed in a hydrocarbon solvent, and cured in a nitrogen furnace. The uncured film after pre-bake withstands automated wafer transfer without edge chipping, which is a basic requirement for high-volume redistribution-layer manufacturing.
In fan-out wafer-level packaging, the resin is used as the dielectric between copper redistribution lines and as a stress buffer over the active die. In silicon interposer flows, it acts as a low-loss passivation layer for high-speed signal paths. In die-to-wafer bonding, a partially cured BCB layer can be pressed at 250 °C and 1–3 bar to form a void-free bonding interface. The same material set also functions as a planarizing dielectric over topography created by copper pillars and embedded die.
The film thickness is controlled primarily by percent solids, final spin speed, and exhaust backpressure. Formulations at 35%, 40%, and 46% solids produce single-coat cured thicknesses from 1.5 µm to 25 µm; spin-speed curves follow a non-linear inverse relationship, with a 3000 rpm final spin on 300 mm wafers typically yielding a 2–3 µm film for the 35% grade and 7–10 µm for the 46% grade. These ranges should be re-established on the specific coater because wafer bow and exhaust can shift thickness by up to 10%.
Pre-bake uses a proximity hotplate at 100–115 °C for 3–5 min. Surface temperatures above 120 °C can reduce photospeed and produce surface haze, while incomplete solvent removal below 95 °C yields tacky films that lift at the wafer edge during automated handling. A hotplate uniformity of ±2 °C across 300 mm is required to maintain within-wafer contrast after development.
Pattern exposure uses broadband i-line radiation centered at 365 nm; typical dose ranges from 100 mJ/cm² to 300 mJ/cm² depending on film thickness and target via geometry. Dose below 100 mJ/cm² results in incomplete crosslinking and scum at the via base, whereas dose above 300 mJ/cm² can create sidewall flare because scattered light initiates crosslinking at the film bottom. Development is performed by immersion or spray-puddle in a hydrocarbon solvent such as DS2100 for 60–120 s, followed by an isopropanol rinse. Under-development leaves a residual film that raises via bottom leakage current by more than 2× when measured per ASTM D257; over-development swells the sidewall and enlarges vias by 1–2 µm.
Final cure in a nitrogen-purged furnace at 250 °C for 60 min with oxygen below 100 ppm is required to achieve full crosslinking and stable dielectric loss. The furnace is ramped at 3 °C/min to avoid solvent shock and thickness uniformity loss. Cure temperature is a critical boundary; excursions above 270 °C induce film cracking through CTE mismatch, while temperatures below 240 °C leave residual monomers that increase moisture uptake.
After full cure, the film exhibits a dielectric constant of 2.65 at 1 MHz to 10 GHz when tested per ASTM D150-18. Dissipation factor is 0.0008 at 1 MHz, and volume resistivity after 24 h at 25 °C and 50% RH is approximately 1 × 10¹⁹ Ω·cm per ASTM D257. These properties are used as acceptance criteria for interlayer dielectric qualification.
| Property | Typical cured value | Standard/test method |
|---|---|---|
| Dielectric constant | 2.65 at 1 MHz to 10 GHz | ASTM D150-18 |
| Dissipation factor | 0.0008 at 1 MHz | ASTM D150-18 |
| Volume resistivity | 1 × 10¹⁹ Ω·cm | ASTM D257 |
| Dielectric strength | 300 V/µm | ASTM D149-20 |
| Coefficient of thermal expansion | 42 × 10⁻⁶ /K below Tg | ASTM E831 |
| Glass transition temperature | >350 °C | ASTM E831 via TMA |
| Moisture absorption | <0.2% after 24 h immersion | ASTM D570-22 |
| Tensile modulus | 2.9 GPa | ASTM D882 |
| Elongation at break | 8% | ASTM D882 |
| Cure temperature | 250 °C for 60 min | Nitrogen oven, O₂ 100 ppm |
Values are typical for fully cured films and vary with thickness, substrate, and cure schedule.
Maintaining oxygen below 100 ppm during the 250 °C cure is a kinetic boundary condition, not a cleanliness preference. Oxygen retards BCB ring-opening crosslinking and produces surface oxidation that raises dissipation factor from 0.0008 to above 0.0015 at 1 MHz and darkens the film from pale amber to brown. The production failure mode is usually not complete insulation loss but adhesion loss at the BCB-copper interface and higher leakage current after unbiased HAST at 130 °C/85% RH for 96 h per JESD22-A118.
Horizontal quartz tube furnaces with independent zone control at ±5 °C have been used; oxygen analyzers are positioned in the exhaust and set to alarm at 50 ppm. Nitrogen mass flow controllers are set to exchange the chamber volume 5–10 times per minute. Cold-wall rapid thermal processing is not recommended because temperature overshoot above 270 °C induces film shrinkage and via cracking.
Adhesion improvement on silicon nitride and silicon oxide passivation is achieved with an organosilane adhesion promoter applied before coating. The promoter is dispensed dynamically, spin-dried, and baked at 100 °C for 2 min. Omission of the adhesion promoter reduces crosshatch adhesion classification from 5B to 0B on plasma-cleaned silicon nitride when tested per ASTM D3359-17. Field data from 300 mm lines show that argon/nitrogen plasma cleaning of the substrate before promoter application reduces interfacial voiding after thermal cycling from -55 °C to 125 °C for 1000 cycles per JESD22-A104.
The cured BCB film has a glass transition temperature exceeding 350 °C by TMA per ASTM E831, which places it outside routine solder reflow excursions at 260 °C. Elastic modulus of 2.9 GPa and elongation at break of 8% per ASTM D882 provide resistance to thin-wafer handling without cracking, but the film is not a high-elongation stress buffer for extreme CTE mismatch. Cured films are resistant to common acids and alkaline developers, but prolonged exposure to strong bases above 60 °C can attack silicon oxide interfaces and lift the film. The solvent resistance after cure permits sequential Cu/BCB multilayer builds without dissolution of underlying BCB layers.
Immersion in N-methyl-2-pyrrolidone at 80 °C for 1 h produces a thickness change of <1% for fully cured films, whereas partially cured films show swelling above 5%; this is a useful incoming inspection discriminator.
Relative to non-photosensitive BCB, the 4000-series eliminates the separate photoresist masking and reactive-ion etch sequence. In a redistribution-layer flow, the non-photosensitive material requires photoresist coat, exposure, develop, etch, and resist strip; the photosensitive flow consolidates this into coat, exposure, and develop. This removes fluorocarbon plasma damage at the via sidewall and reduces particle excursions associated with etch chamber cleaning. Via bottom critical dimension is controlled by lithography exposure and development rather than isotropic etch overcut.
| Attribute | Photosensitive BCB 4000-series | Positive-tone PBO | Polyimide |
|---|---|---|---|
| Dielectric constant | 2.65 | 2.9–3.2 | 3.3–3.5 |
| Moisture absorption | <0.2% | 0.8–1.2% | 2.0–3.0% |
| Cure temperature | 250 °C | 350 °C | 350 °C |
| Elongation at break | 8% | 30–40% | 20–50% |
| Development chemistry | Hydrocarbon solvent, negative-tone | Aqueous base, positive-tone | Aqueous or solvent, positive-tone |
Values are representative literature ranges; specific grades vary.
Unlike positive-tone PBO, the BCB grade develops in hydrocarbon solvents rather than 2.38% TMAH. This imposes different equipment requirements: developer exhaust must be rated for hydrocarbon vapors, and the line must segregate solvent waste from aqueous alkaline waste streams. The lower cure temperature and lower moisture uptake are the primary reasons for selecting BCB; the trade-off is lower elongation at break than some PBO stress-buffer grades. In high-frequency redistribution layers, the BCB loss factor of 0.0008 at 1 MHz is a driving requirement.
