Lead-free solder flux and solder paste

Abstract

A flux for a lead-free solder that is able to reduce "void(s) appear within solder joint", "void(s) appear within solder joint", and "solder-balling" without impairing general solderabilities. The flux for a lead-free solder comprising 6-55 wt% of a polyvalent alcohol ester of a resin acid (a1) as a base resin (A). Further, a solder paste comprising the said flux for a lead-free solder and a lead-free solder powder provides a very small number of void(s) or a very small amount thereof.

Description

technical field

[0001] The present invention relates to a flux for lead-free solder (hereinafter, sometimes simply referred to as flux) and a solder paste containing the flux. Background technique

[0002] In order to surface-mount electronic components such as capacitors on the wiring pattern on the circuit board, soldering is generally performed. Various characteristics are required for welding. For example, it is important to suppress the formation of "solder balls". Here, the term "solder ball" refers to a phenomenon in which solder paste printed on a conductor pattern excessively slumps and spreads during reflow heating and melting, and spherical fine solder appears near the edge of the slump. If the amount of solder balls is large, bridging and short circuits are likely to occur, and the reliability of the mounting substrate is significantly impaired.

[0003] However, due to the reason that lead pollutes the environment and is harmful to the human body, in recent y...