Browse Prior Art Database

Fine Pitch Halide-Free Water Soluble Solder Paste

IP.com Disclosure Number: IPCOM000103467D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Gutierrez, BL: AUTHOR

Abstract

Disclosed is a halide-free water soluble flux solder paste formula capable of 0.020" pitch, or smaller, printing. The combination of chemical constituents used addresses current inherent problems of water soluble solder pastes: low tack, poor print quality, reflow profile sensitivity, solder balling, and short shelf life/freezer storage required. The chemicals will not interact with epoxy-glass PCBs, are of low toxicity, and are compatible with a wide range of including low-melting point alloy. Most are soluble in room temperature water, so high temperature aqueous cleaning is not required.

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Fine Pitch Halide-Free Water Soluble Solder Paste

      Disclosed is a halide-free water soluble flux solder paste
formula capable of 0.020" pitch, or smaller, printing.  The
combination of chemical constituents used addresses current inherent
problems of water soluble solder pastes: low tack, poor print
quality, reflow profile sensitivity, solder balling, and short shelf
life/freezer storage required.  The chemicals will not interact with
epoxy-glass PCBs, are of low toxicity, and are compatible with a wide
range of including low-melting point alloy.  Most are soluble in room
temperature water, so high temperature aqueous cleaning is not
required.

      Description of Invention: Water soluble flux solder paste of
simple chemical composition comprising:
85-95% by weight -270 mesh solder powder
5-15% by weight water soluble flux

      Solder Powder composition:
      63 Sn/37 Pb and other tin/lead, tin/lead/bismuth, tin/bismuth,
tin/silver, or tin/antimony alloys

      Water soluble flux composition:
      30-80% by weight solvent (may also serve as tackifier)
      2-20% by weight thixotrope and thickener (may also serve as
tackifier and activator)
      0-10% by weight activator

      Possible solvents are alcohols, polyols, or glycol ethers, but
exclude polyethylene oxides.  Preferred solvents are tripropylene
glycol and its ethers, and polypropylene oxide-based solvents.

      Thixotropes and thickeners include hydroxy...