Aluminum Processes
for Under Bump Metallization

Pretreatment

Cleaner – Epithas® MCL-16 alkaline soak cleaner for silicon wafers is designed for the pretreatment of aluminum prior to electroless nickel plating. (Also available: MCL-067 CMOS-compatible cleaner.)

Micro etch – Epithas LEC-18 micro etch for aluminum removes oxide surface film from aluminum and aluminum alloys. An exceptional pretreatment for plating electroless nickel on aluminum for silicon wafers. (Also available: Epithas LEC-19 CMOS-compatible micro etch.)

HNO3 acid rinse forms a thin oxide layer on the aluminum IC pad.

HNO3 zinc strip

Plating

Electroless nickel – Epithas NPR-18 mildly acidic electroless nickel plating bath for fine line circuitry in silicon wafer plating. Stable, easy-to-use bath allows bridge-free deposit of electroless nickel. Nickel layer forms an adherent coating to the IC and functions as a diffusion barrier. Optimized for automatic solution control using Uyemura Starline NI controller. (Also available: Epithas NPR-18CM CMOS-compatible electroless nickel.)

Epithas NPR-24, is a mildly acidic electroless nickel that has been specially formulated for fine line circuitry encountered in silicon wafer plating. This bath allows the deposition of EN without bridging; easy to use and optimized for automatic solution control using the Uyemura STARLiNE DASH controller.

Immersion gold – Epithas TDS-20 neutral immersion gold bath for silicon wafers is designed for surface mount applications and wafer plating. TDS neutral immersion gold won’t corrode the underlying nickel surface, so it provides excellent solder joint reliability, including small solder balls. Cyanide-free.

Epithas TDS-43, is an alternative to TDS-20, a neutral, cyanide-free bath for plating the immersion gold layer of ENEPIG on aluminum or copper pads. Epithas TDS-43 is a high reliability soldering and wire bonding surface. The bath is highly stable and easy to control.

Auto-catalytic gold – Epithas TMX-16 electroless gold for silicon wafers is cyanide-free, with a neutral pH. Ideal for surface mount and wafer plating. Will not corrode the underlying nickel surface, thus it provides excellent solder joint reliability.

We recommend TDS-20 immersion gold as the under-layer, and Epithas NPR-18 electroless nickel with Epithas TMX-15 electroless gold.

CMOS-Compatible Process for Aluminum Metallization

Cleaner – Epithas CACL-067 acid soak cleaner for pretreatment of silicon wafers, including SOI wafers, prior to the Epithas Ni/Au process.

Micro-etch – Epithas LEC-19 removes naturally-occurring oxidation from aluminum and aluminum alloy surfaces. Pretreatment for electroless nickel on aluminum for silicon wafers, including SOI wafers.

Zincate – Epithas MCS-30 acid immersion zinc for silicon wafer plating; minimizes the dissolution of aluminum, assures thin, uniform zinc deposit for subsequent electroless nickel plating.

Electroless Nickel – Epithas NPR-18CM was developed for wafer plating applications with fine line circuitry. Highly stable bath; allows bridge-free deposition of electroless nickel. Low temperature operation for improved resist tolerance. 6-8% phosphorus as plated. 100-hour salt spray performance (ASTM B117). Adhesion is superior to electroplated nickel.

Read about our UBM process for copper

Read Under Bump Metallization: Some Economical Alternatives published in US Tech.

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For more details, or to arrange test processing, contact your Uyemura representative.

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