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Electroless Nickel Sodium Hypophosphite (NaH2PO2)

CAS Number: 7681-53-0

Sodium hypophosphite monohydrate (NaH2PO2·H2O) is the reducing agent in electroless nickel (EN) plating baths, enabling autocatalytic deposition of nickel-phosphorus alloy without external current. In semiconductor packaging, ENIG (Electroless Nickel Immersion Gold) and ENEPIG surface finishes rely on sodium hypophosphite-based EN baths to provide solderable, wire-bondable, and corrosion-resistant surfaces on PCBs and substrates.

Technical Specifications

iron (Fe)≤10 ppm
appearanceWhite crystalline powder
purity (%)≥99.0 (NaH2PO2 assay)
chloride (Cl-)≤50 ppm
heavy metals (Pb, As)≤5 ppm each

Applications

  • ENIG (Electroless Nickel Immersion Gold) surface finish
  • ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold)
  • Under-bump metallization (UBM) barrier layer
  • Semiconductor substrate solderable surface preparation
  • MEMS selective metal deposition

Key Features

  • High reducing power for stable autocatalytic EN plating bath
  • Controlled P content in deposit (5–12%) via concentration management
  • Low chloride content minimizes corrosion risk in EN bath
  • Consistent solubility for easy bath makeup and replenishment

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Electroless Nickel Sodium Hypophosphite (NaH2PO2) chemical structure

CAS Number

7681-53-0

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