Electroless UBM Formation Service

As semiconductor packaging technology achieves greater miniaturization and integration, flip chip bonding is increasingly taking over from wire bonding as the bonding method used for LSI, IC, and other chips. In flip chip bonding, under bump metallurgy (UBM) formation to bond the metal pad to the solder is viewed as essential. Our company's UBM processing employs electroless plating to offer lower costs, shorter delivery times, and greater miniaturization, and offers the added advantage of being an environmentally friendly technology. We also offer solder bumping for the UBM-formed wafer, affording customers an all-in-one processing service from UBM formation to bumping.


Design Rules

Description Specification (Trial production)
Wafer Si, GaAs Si, GaAs + SiC
Wafer size 50-300mm φ (2"-12") As on the left
Wafer thickness ≧150μm Min 80μm (6"φ)
Bond pad metal Al, AlSi, AlCu, AlSiCu, Cu, Au As on the left
Passivation opening ≧60μm Min 4μm
Applications Logic, Memory, Image sensor, Power device, and any others  
UBM E-less Ni/Au, E-less Ni/Pd/Au (Pb-free, CN-free bath)  
Ni (material) Ni (P 5–10%)
Ni thickness 1-10μm
Pd thickness 0.05-0.2μm
Au thickness 0.03-0.2μm
Thickness uniformity ±10% (200mm φ wafer)

Fully Automatic Electroless UBM Production Line

Plating Line #1 (up to 6"wafer)

Plating Line #2(up to 12"wafer)

Plating Line #3(up to 12"wafer)

Plating Line in Taiwan(up to 12”wafer)

  • *Clean Room:Class 1000
  • *Plating Lines are located in Japan and Taiwan.

Features of our electroless plating process

  • Uses self-developed plating process and equipment
  • Provides a reliable quality control system using the Company's own analysis equipment
    Plating chemicals and films are analyzed in-house to meet customers' requirements and to improve the plating quality
  • Achieves high processing capacity of over 20,000 wafers/month
  • Capable of protecting the backside of wafers from damage

Inspection Tools

Automatic wafer pattern inspection system (2D, 3D)

Fluorescent X-ray (XRF) analyzer

Non-contact 3-dimensional measuring equipment with laser

Analytical Tools for Electroless Plating

Surface morphology FIB-SEM, FE-SEM, SPM
Elemental analysis FE-EPMA, FE-AES, XPS
Functional group analysis Raman, FT-IR, UV
Crystal structure analysis XRD

High Film Quality (1) … Highly uniform plating on pads with differences in electrical potential

Our plating process delivers uniform quality of UBM, even for pads with differences in electrical potential or size.

High film quality (2) … Fine and uniform Au deposition without pitting corrosion

The grain structure of our new cyanide-free Au is fine and uniform. It inhibits pinholes and pitting corrosion.

SEM images of the Au and Ni surfaces after gold stripping