| abstract |
An object of the present invention is to suppress a flux residue remaining after soldering or flux cleaning, and to suppress a defect in an electronic device due to the flux residue. As a flux used for joining a solder, a flux containing more than 75% by weight of an ethylene glycol polymer represented by HO (CH2CH2O) nH (n is an integer of 4 or more) is used. As the ethylene glycol polymer in the flux 40, one that evaporates when heated ends at a temperature equal to or higher than the joining temperature of the solder 30 to be joined, that is, one that can exist on the surface of the solder 30 or the terminal 21 at the joining temperature is used. . For example, a molecular weight ethylene glycol polymer exhibiting such properties is used. Such a flux 40 suppresses a flux residue remaining after solder joining. The remaining flux residue is removed by washing with water. [Selection] Figure 2 |