Bumping Services

Advanced Wafer Bumping

Redistribution Solutions

Unisem provides comprehensive wafer bumping and wafer-level processing services for 100mm, 150mm, and 200mm wafers, supported by controlled Class 100, Class 1,000, and Class 10,000 cleanroom environments. Our advanced capabilities support a wide range of semiconductor packaging and interconnect requirements, including Gold Bumping, Electroplated Solder Bumping, Copper Pillar Bumping, Large Solder Bumping, Passivation, and Redistribution.

With in-house photomask and stencil design capabilities, we provide greater process control, shorter lead times, and flexible solutions to meet demanding customer requirements.

Our Exclusive Services

Gold Bumping

Reliable interconnects

for wire bonding

and flip-chip applications.

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Electroplated Solder Bumping

Lead-free and
eutectic solder solutions tailored
to diverse requirements.

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Electroplated Copper Pillar Bumping
High-density,
high-performance interconnects for
next-generation devices

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Large Solder Bumping
(Ball Drop)
Optimized for advanced
package-on-package (PoP)
and BGA applications

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Advanced Bumping Solutions

For Next-Generation Semiconductor

Precision. Reliability. Performance.

Gold Bumping

Reliable interconnects for wire bonding and flip-chip applications.

Gold Bumping

Miniature gold interconnects for semiconductors

Gold bumps are conductive interconnects used in flip chip and wafer level packaging, enabling high density electrical connections in semiconductors. Made via electroplating, gold bumps offer superior conductivity, corrosion resistance and mechanical stability compared to solder based alternatives. Due to fine pitch capability and thermal management benefits, gold bumps are essential in advanced miniaturized electronics.

UAT offers advanced gold bumping solutions for both 200mm & 300mm wafers. Our 200mm process utilizes a reliable TiW/Au stack while the 300mm platform features a robust Cu/Ni/Au stack.

Gold bumping using a TiW/Au (Titanium-Tungsten/Gold) stack is a proven and robust wafer-level interconnect technology widely used in flip-chip and chip-on-film (COF) applications. This metallization scheme provides excellent adhesion, conductivity, and corrosion resistance, making it ideal for precision devices requiring consistent electrical performance and long-term reliability.

For larger wafer sizes and more demanding applications, UAT also offers a Cu/Ni/Au (Copper/Nickel/Gold) bump stack. This structure leverages a copper core for superior electrical performance, a nickel barrier layer to prevent diffusion, and a gold top layer to ensure excellent solderability and oxidation resistance. The Cu/Ni/Au stack is optimized for high-density, fine-pitch designs and is particularly well-suited for 300mm wafer processing, delivering enhanced mechanical strength and long-term reliability for advanced packaging needs.

Electroplated Solder Bumping

Lead-free and eutectic solder solutions tailored to diverse requirements

Electroplated solder bumping is a precision wafer-level interconnect technology where solder is deposited via electroplating onto under-bump metallization (UBM) pads. This method offers excellent control over bump height, uniformity, and alloy composition—making it ideal for high-density, fine-pitch applications and advanced flip-chip packaging.

UAT offers plated solder bumping on 150mm, 200mm and 300mm wafers, using pure tin (Sn) and tin-silver (SnAg) solder alloys to meet a variety of customer and reliability requirements. Our electroplating process delivers consistent solder volume, strong adhesion, and robust bump integrity after reflow. With tight process control and in-line inspection, UAT ensures high-yield, high-reliability solder interconnects for cutting-edge semiconductor devices.

Electroplated Copper Pillar Bumping

High-density, high-performance interconnects for next-generation devices

Copper pillar bumping is a cutting-edge wafer-level interconnect solution engineered for advanced semiconductor applications requiring fine pitch, high current capability, and excellent thermal performance. Unlike traditional solder bumps, copper pillars offer a robust columnar structure that enhances electrical conductivity, mechanical strength, and form factor scalability.
UAT provides copper pillar bumping services on 150mm, 200mm and 300mm wafers, utilizing a Cu/Ni/SnAg bump stack. This structure features a copper core for optimal electrical performance, a nickel barrier for diffusion control and a SnAg solder cap for reliable assembly and reflow. The Cu/Ni/SnAg stack is ideal for flip-chip and high-density packaging, delivering superior coplanarity, interconnect integrity, and long-term reliability.

Large Solder Bumping

(a.k.a. Ball Drop)

Optimized for advanced package-on-package (PoP) and BGA applications
Ball drop is a key wafer-level packaging process that deposits solder balls onto designated pads to form second-level interconnects, enabling seamless integration into PCB assemblies. Widely used in flip-chip and wafer-level chip scale packaging (WLCSP), the process demands precise ball placement and height uniformity to ensure reliable assembly and electrical performance.
UAT offers ball drop services for 150mm, 200mm, and 300mm wafers, supporting a wide range of lead-free SAC alloy solder balls to meet global environmental and industry standards. Our advanced process control ensures tight ball pitch, excellent coplanarity, and robust mechanical integrity—making it ideal for high-reliability applications in consumer, automotive, and industrial markets.