At Nanosystems JP Inc., we fabricate wafer-level gold bumps via two complementary routes, thermal or e-beam evaporation with lift-off patterning for fine-pitch 1-5µm bumps, and Au electroplating through a resist mold for taller 2-20µm bumps. 99.99% gold, no native oxide ever, bondable by thermocompression, thermosonic, or ACF at any time after delivery. 4-12 inch wafers, from a single wafer.
Need a solder joint instead of a solid-state bond?
Gold bumps bond without melting. When the assembly needs a reflowed solder joint, hermetic AuSn and cryogenic indium are the companion services, on the same UBM, from the same flow.
We fabricate gold bumps on your wafer and deliver it ready for bonding at your facility or chosen assembly site. Three properties keep gold the default choice wherever solder is the wrong answer.
Gold is the only common bump metal with no native oxide. There is no flux, no pre-bond surface activation chemistry, and no shelf-life clock running between our shipment and your bonder. A gold-bumped wafer stored for months bonds the same as one bonded the day it arrives, which simplifies logistics for multi-site assembly and low-volume programs alike.
A gold bump is one element at 99.99% purity. There is no alloy composition to control, no intermetallic phase ratio to verify, and no melting-point shift to chase between lots. Run-to-run behavior is set by geometry alone, which is why gold is the reference process for research programs and for production lines that value boring, repeatable bonding. Gold is also inert and biocompatible, opening implantable and sensor applications closed to solders.
Gold bumps join by thermocompression or thermosonic bonding, deformation and diffusion rather than melting, so nothing flows, nothing wicks, and the joint geometry you designed is the joint geometry you get. The finished Au-Au bond is stable far above any solder's service limit and behaves cleanly at cryogenic temperature. For ACF and ACP assembly, the bump serves as the pressure contact with no metallurgy at all.
Both routes deposit the same 99.99% gold; the difference is geometry and economics. Our engineers recommend the route from your pitch, height, and bonding method.
Gold is evaporated over a lift-off resist profile with a Ti or Cr adhesion layer beneath it, and dissolving the resist leaves bumps only in the defined openings. The footprint is set by the resist at ±0.5µm registration with no undercut, which makes this the route for fine-pitch arrays, thermocompression pads on photonic and MEMS devices, and cryogenic hybridization surfaces. Typical heights run 1-5µm; economics favor evaporation exactly where gold does, in thin layers and low wafer counts.
Gold is electroplated through a resist mold onto a sputtered seed, then the resist is stripped and the seed etched, the classic route behind display-driver COG and COF bumps and every application that needs real stand-off height. Plating builds gold far taller and far faster than evaporation, and bath selection gives hardness control: soft, low-hardness gold for thermocompression deformation, or standard gold for contact and probe surfaces.
| Parameter | Evaporation + Lift-Off | Electroplating |
|---|---|---|
| Bump height | 1-5µm typical | 2-20µm typical |
| Minimum pitch | 10µm typical | ~20µm typical |
| Height uniformity | ±5% within wafer | ±8% within wafer |
| Hardness control | As deposited | Soft Au for TC on request |
| Best for | Fine pitch, TC pads, cryo | COG/COF, tall stand-off, volume |
We fabricate the bumps; bonding runs at your facility or chosen assembly site. Bump geometry, hardness, and surface finish are prepared for the mode you will use.
| Parameter | Evaporation + Lift-Off | Electroplating |
|---|---|---|
| Wafer Sizes | 4 inch (100mm), 6 inch (150mm), 8 inch (200mm), 12 inch (300mm) | |
| Substrates | Si, InP, GaAs, glass, sapphire; others on request | |
| Material | Gold (Au), 99.99% purity | |
| Underlayer | Ti or Cr adhesion | Sputtered TiW/Au seed, field etched |
| Bump Height | 1-5µm typical | 2-20µm typical |
| Minimum Pitch | 10µm typical, finer on request | ~20µm typical |
| Height Uniformity | ±5% within-wafer | ±8% within-wafer |
| Hardness | As deposited | Soft Au for TC on request |
| Patterning | Lift-off | Through-resist plating + seed etch |
| Alignment Accuracy | ±0.5µm (stepper) | ±1µm |
| Bonding Compatibility | Au-Au thermocompression, thermosonic, ACF/ACP, wire bond, solder base | |
| Shelf Life | No oxidation; bond any time after delivery | |
| Inspection | Profilometry + SEM standard; shear and coplanarity on request | |
| Minimum Lot | From 1 wafer, prototype to production on the same recipe | |
Electroplated gold bumps are the industry-standard interconnect for chip-on-glass and chip-on-flex display driver ICs, bonded through ACF at fine pitch and high I/O counts. The classic volume application for plated Au bumps, and the geometry our plated route is built around.
Au-Au thermocompression joins photonic die, MEMS caps, and wafer-level assemblies without any molten phase, so waveguide facets stay clean and released structures stay put. Evaporated fine-pitch bumps and soft plated gold both serve, matched to your bonder.
Gold surfaces bond by thermocompression and stay stable and conductive to millikelvin temperatures, serving as TC hybridization pads and as the base metallization under indium bumps in cryogenic detector and quantum processor stacks.
Gold's low, stable contact resistance without oxide films makes it the metal for RF MEMS switches, relay contacts, and interposer contact arrays, where a joint that never forms an insulating skin is the entire requirement.
Inert, biocompatible gold bumps and pads for implantable electronics, neural and biosensor electrodes, and lab-on-chip assemblies, where solder metallurgies are excluded by chemistry or regulation.
Gold bumps and pads for wafer probing, test vehicles, and university or corporate R&D lots, from a single wafer, with the reproducibility that comes from a single-element metallurgy.
Evaporated lift-off and plated gold on the same line, so the route is chosen by your pitch, height, and bonding method, not by the only tool available.
Soft gold for thermocompression deformation, standard gold for contacts and probing. We ask how you bond before we plate.
±0.5µm stepper registration and resist-defined footprints with no undercut, the same discipline behind our AuSn and indium fine-pitch arrays.
Gold, AuSn, indium, and UBM run on shared lithography and deposition, so mixed programs, gold pads here, solder bumps there, stay in one flow, managed end to end by a dedicated project manager.
Profilometry height maps and SEM verification ship with the wafers; shear and coplanarity data on request. Your bonding engineers start from measurements.
Prototype on a single wafer, verify bonding at your line, then scale on the same recipe. No re-qualification required.
Share your process requirements, substrate, and production volume. A Nanosystems JP Inc. engineer will respond within 24 hours. Full quote typically within 7-10 business days, subject to project complexity and NDA requirements.