Abstract: In a method of reflow soldering, a non-aqueous electrolyte secondary battery is discharged to a first discharge voltage different from a second discharge voltage at an inflection point in a discharge curve of the non-aqueous electrolyte secondary battery having an axis of abscissa representing discharge capacity and an axis of ordinate representing discharge voltage. The discharged non-aqueous electrolyte secondary battery is placed on a substrate which is then exposed to a reflow soldering temperature to reflow solder the non-aqueous secondary battery to the substrate. The first discharge voltage is higher than the second discharge voltage to prevent degradation of characteristics of the non-aqueous electrolyte secondary battery resulting from decomposition of the non-aqueous electrolyte due to reaction of the non-aqueous electrolyte with excessive lithium ions in the cathode active material when the non-aqueous electrolyte secondary battery is exposed to the reflow soldering temperature.

Abstract: In a nonaqueous-electrolyte secondary-battery that is soldered to a circuit board by a reflow soldering process, there has been a problem that when a secondary battery that requires discharging a after assembling the battery that requires discharging after assembling the battery is subjected to reflow, battery characteristics degrade due to heat treatment. Discharge voltage at the end of the discharging is made to be higher than a discharge voltage value that is an inflectional value at the end of a voltage plateau region indicating a cell reaction in a discharge curve (discharge capacity in abscissa and discharge voltage in ordinate) of initial discharge, thereby degradation of the battery characteristics due to the reflow hear treatment can be suppressed.