Gold Bump Services
Evaporated & Electroplated Au Bumps
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 to 5 µm bumps, and Au electroplating through a resist mold for taller 2 to 20 µm bumps. 99.99% gold, no native oxide, keeping it bondable by thermocompression, thermosonic, or ACF long after delivery with appropriate packaging and storage. 4 to 12 inch wafers, from a single wafer.
long after delivery with proper storage
both fabrication routes
Si and compound semis
on stepper lithography
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.
The bump that never oxidizes
and bonds without melting
We fabricate gold bumps on your wafer and deliver it ready for bonding at your facility or chosen assembly site, or in the same program through the flip-chip assembly service, or flip-chip assembly can be included in the same program. Three properties keep gold the default choice wherever solder is the wrong answer.
No Native Oxide, Ever
Gold is the only common bump metal with no native oxide. Flux is generally unnecessary, and Au-Au bonding can often run without aggressive oxide-removal chemistry. Unlike oxide-forming bump metals, gold does not grow a native oxide in storage, which keeps the practical bonding window long when wafers are packaged and stored appropriately.
Single Metal, Total Reproducibility
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, material condition, and bonding parameters, 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.
Solid-State Bonding
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 suited to elevated-temperature service where conventional solder joints may not survive. For ACF and ACP assembly, the bump serves as the pressure contact with no metallurgy at all.
Evaporated fine pitch and
electroplated height
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.
Evaporation + Lift-Off
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 ±0.5 µm 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 to 5 µm; economics favor evaporation exactly where gold does, in thin layers and low wafer counts.
Au Electroplating
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 to 5 µm typical | 2 to 20 µm typical |
| Minimum pitch | 10 µm typical | ~20 µm 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 |
One bump, four ways
to use it
We fabricate the bumps; bonding runs at your facility or chosen assembly site, or in the same program through the flip-chip assembly service. Bump geometry, hardness, and surface finish are prepared for the mode you will use.
Complete gold bump
fabrication parameters
| Parameter | Evaporation + Lift-Off | Electroplating |
|---|---|---|
| Wafer Sizes | 4 to 12 inch (100 to 300 mm) | |
| 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 to 5 µm typical | 2 to 20 µm typical |
| Minimum Pitch | 10 µm typical, finer on request | ~20 µm 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 | ±0.5 µm (stepper) | ±1 µm |
| Bonding Compatibility | Au-Au thermocompression, thermosonic, ACF/ACP, wire bond, solder base | |
| Shelf Life | No stable native oxide; surface cleanliness and storage still require control; long practical bonding window | |
| Inspection | Profilometry + SEM standard; shear and coplanarity on request | |
| Minimum Lot | From 1 wafer; R&D runs to repeat lots on one baseline recipe | |
Gold bumps across display,
photonics, and cryo
Display Driver COG / COF
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.
Photonic & MEMS Thermocompression
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.
Cryogenic & Quantum Assembly
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.
RF & MEMS Contacts
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.
Biocompatible Devices
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.
Probe Pads & R&D Runs
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.
What makes our gold bump capability
different
Both routes, one recommendation
Evaporated lift-off and plated gold are both offered, so the route is chosen by your pitch, height, and bonding method, not by the only tool available.
Hardness matched to your bonder
Soft gold for thermocompression deformation, standard gold for contacts and probing. We ask how you bond before we plate.
Fine pitch by lift-off
±0.5 µm stepper registration and resist-defined footprints with no undercut, the same discipline behind our AuSn and indium fine-pitch arrays.
Part of the bump family
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.
Data with each lot
Profilometry height maps and SEM verification ship with the wafers; shear and coplanarity data on request. Your bonding engineers start from measurements.
From 1 wafer, no minimum lot
Prototype on a single wafer, verify bonding at your line, then scale on the same recipe. That prototype data becomes the baseline for repeat production.
Start your project.
Initial response typically within one business day.
Share your process requirements, substrate, and production volume. A Nanosystems JP Inc. engineer will give an initial response typically within one business day. Full quote typically within 7-10 business days, subject to project complexity and NDA requirements.