Soldering flux composition

Claim 2

A flux composition, comprising, as essential constituents: (1) at least one ester derived from a polyhydric alcohol and at least one saturated or unsaturated fatty acid or .Iadd.monocarboxylic .Iaddend.mononuclear aromatic acid.Iadd., said ester having a molecular weight of at least 300.Iaddend.; and (2) at least one additional constituent selected from: (a) organic acids which are substantially soluble in said ester of a polyhydric alcohol when in a molten condition; (b) flux activating agents; and (c) flux residue hardening agents, said ester being present in an amount of at least 25% by weight based on the total weight of constituents (1) and (2).

Claim 3

A composition as claimed in claim 1 in the form of a solid, the composition containing at least 80% by weight, based on the total composition, of said ester.

Claim 4

A composition as claimed in claim 1 in the form of a liquid, comprising constituents (1) and (2) dissolved in an organic solvent, the liquid composition containing at least 40% by weight of said ester (1), based on the total weight of constituents (1) and (2).

Claim 5

A composition as claimed in claim 1, wherein said constituent (1) is an ester having a molecular weight in the range from 300 to 3000 and which is solid at room temperature.

Claim 6

A composition as claimed in claim 1, wherein said constituent (1) is an ester derived from a polyhydric alcohol containing from 2 to 8 hydroxyl groups.

Claim 7

A composition as claimed in claim 5, wherein said ester is pentaerythritol tetrabenzoate.

Claim 8

A composition as claimed in claim 1, wherein said organic acid (a) is present in an amount not exceeding 20% by weight of the total composition.

Claim 9

A composition as claimed in claim 1, wherein said flux activating agent (b) is present in an amount not exceeding 20% by weight of the total composition.

Claim 10

A composition as claimed in claim 1, wherein said flux residue hardening agent is present in an amount not exceeding 20% by weight of the total composition.

Claim 11

A fluxed solder composition for use in soft soldering, the composition comprising in association a soft solder alloy and a flux composition as claimed in claim 1.

Claim 12

A method of producing a printed circuit board, which comprises the steps of: (a) applying to a copper coated plastics laminate board a flux composition as claimed in claim 3 so as to form thereon a pattern in which copper circuit conductors are required to be formed; (b) subjecting the resulting board to the action of an etch solution so as to remove all the copper coating in those areas outside the patterned areas; and (c) washing and thereafter drying the resulting etched board bearing the required copper circuit conductors still having a coating of said flux composition.

Claim 13

A method of producing a printed circuit assembly, which comprises the steps of: (a) applying to a copper coated plastics laminate board a flux composition as claimed in claim 3 so as to form thereon a pattern in which copper circuit conductors are required to be formed; (b) subjecting the resulting board to the action of an etch solution so as to remove all the copper coating in those areas outside the patterned areas; (c) washing and thereafter drying the resulting etched board bearing the required copper circuit conductors still having a coating of said flux composition; (d) mounting on the printed circuit board so formed a plurality of electronic components by passing the component lead wires through holes formed in the board; and (e) thereafter joining the lead wires to the appropriate copper circuit conductors by soldering with a soft solder alloy without a separate application of flux.

Claim 14

A flux composition in accordance with claim 1, wherein said aromatic acid is benzoic acid.