Packaging Engineer- Bump Interconnect

Volantis Semiconductor · San Francisco

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We’re seeking an experienced engineer to lead bump interconnect development for advanced semiconductor devices  (2.5D/3D/chiplet/fan-out). 

This role spans ubump and C4 bump metallurgy, RDL design and

plating, chip-side and interposer capture pad design rules, OSAT engagement, reliability,

failure analysis, and cross-functional support through package and system productization.

Core Responsibilities

• Own end-to-end bump interconnect development for both ubump (micro-bump) and C4

processes, including bump formation, and reflow for use with mass reflow, TCB, and LAB chip

attach for high-performance semiconductor packages.

• Define and own bump metallurgy stacks for ubump (e.g., Cu pillar/SnAg) and C4 (e.g., SAC alloys)

interconnects, including UBM selection and pad finish specifications for both chip-side and

interposer capture pads.

• Develop and own design rules for bump interconnects including pitch, bump diameter, standoff

height, keep-outs, and land pad geometry for both the chip side and interposer or substrate

capture pads.

• Lead RDL (redistribution layer) process development including electroplating of Cu RDL traces,

via fills, and pad finishes; define RDL design rules for line/space, via diameter, and layer stack-up

to meet electrical and reliability requirements.

• Collaborate with OSATs and bumping foundries to qualify ubump and C4 bumping processes,

drive design rule alignment, and manage process transfers into production.

• Evaluate and mitigate bump interconnect assembly risks including non-wet opens, voiding, head-

in-pillow, intermetallic growth, and joint fatigue failures across both ubump and C4 interconnect types.

• Perform root cause analysis of assembly and reliability failures using cross-sectioning, SEM,

CSAM, and other failure analysis techniques.

• Support reliability qualification including thermal cycling, drop, mechanical shock, and power cycling.

• Work cross-functionally with design, reliability, thermal, and manufacturing teams to ensure

robust package performance from concept through high-volume production.

Required Technical Skills

• Strong experience in bump interconnect processes including ubump (Cu pillar, micro-bump) and

C4 bumping for semiconductor devices.

• Deep understanding of bumping metallurgy including UBM stacks, solder alloy systems (SnAg),

intermetallic compound (IMC) formation and growth kinetics, and their impact on joint reliability.

• Experience with RDL plating processes including Cu electroplating, photoresist patterning, seed

layer deposition, and associated design rules for line/space, via geometry, and pad stack.

• Understanding of thermo-mechanical behavior in bump interconnect assemblies including CTE

mismatch, warpage, solder joint fatigue, and IMC-driven reliability risks for both ubump and C4

configurations.

• Hands-on experience with failure analysis and reliability testing (cross-sections, SEM, CSAM,

thermal cycling).

• Ability to work with OSATs and suppliers to develop and transfer assembly processes into

production.

• Strong problem-solving skills with ability to debug yield and reliability issues in manufacturing

environments.

Preferred / Differentiating Skills

• Experience with III-V packaging, photonics packaging, and precision chip attach.
• Experience with advanced packaging technologies including 2.5D interposers, 3D stacking,

chiplets, and CoWoS-like architectures.

• Familiarity with fine-pitch micro-bump and hybrid bonding approaches.
• Experience integrating high-power or high-TDP devices with tight warpage and thermal

constraints.

• Exposure to thermo-mechanical modeling or collaboration with simulation teams for warpage

and reliability prediction.

• Understanding of system-level interactions (warpage, second-level interconnect reliability).
• Deep expertise in bump metallurgy fundamentals including UBM stack design (Ti/Cu, etc.), solder

alloy selection, wetting behavior, and the influence of plating chemistry and process conditions

on bump morphology and composition.

• Fundamental knowledge of intermetallic compound (IMC) formation, growth kinetics, and phase

behavior in Cu/Sn, Ni/Sn, and Au/Sn systems; understanding of how IMC thickness, morphology,

and composition affect joint strength, electromigration resistance, and long-term reliability.

Education & Experience:

Industry experience in semiconductor packaging with strong emphasis on bump interconnect

processes, RDL development, and productization.

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