Soldering method of nonaqueous-electrolyte secondary-battery
View Patent ↗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.
1. A method of reflow soldering a non-aqueous electrolyte secondary battery comprised of a non-aqueous electrolyte and a cathode having an active material containing lithium ions, comprising the steps of:
discharging the non-aqueous electrolyte secondary battery 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;
placing the discharged non-aqueous electrolyte secondary battery on a substrate; and
exposing the substrate to a reflow soldering temperature to reflow solder the non-aqueous secondary battery to the substrate;
wherein 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.
2. A method according to claim 1 ; wherein the degradation of characteristics of the non-aqueous electrolyte secondary battery comprises at least one of a decrease in capacity and an increase in internal resistance of the non-aqueous electrolyte secondary battery.
3. A method according to claim 1 ; wherein the inflection point in the discharge curve of the non-aqueous electrolyte secondary battery is an inflection point at the end of a voltage plateau region in the discharge curve.
4. A method according to claim 3 ; wherein the first discharge voltage has a voltage value at which the substrate is damaged.
5. A method according to claim 3 ; wherein the first discharge voltage has a voltage value lower than a voltage value at which the substrate is damaged.
6. A method according to claim 1 ; wherein the first discharge voltage has a voltage value at which the substrate is damaged.
7. A method according to claim 6 ; wherein the first discharge voltage has a voltage value lower than a voltage value at which the substrate is damaged.
8. A method of reflow soldering a non-aqueous electrolyte secondary battery comprised of a cathode having an active material containing lithium ions and a non-aqueous electrolyte, comprising the steps of:
discharging an electric capacity of the non-aqueous electrolyte secondary battery;
placing the discharged non-aqueous electrolyte secondary battery on a substrate; and
exposing the substrate to a reflow soldering temperature to reflow solder the non-aqueous secondary battery to the substrate;
wherein the discharged electric capacity of the non-aqueous electrolyte secondary battery is 80% or less of a total discharge capacity of the non-aqueous electrolyte secondary battery 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.
9. A method according to claim 8 ; wherein the discharged electric capacity of the non-aqueous electrolyte secondary battery is 20% or less of the total discharge capacity of the non-aqueous electrolyte secondary battery.
10. A method according to claim 8 ; wherein the discharged electric capacity of the non-aqueous electrolyte secondary battery is 10% or less of the total discharge capacity of the non-aqueous electrolyte secondary battery.
11. A method according to claim 8 ; wherein the degradation of characteristics of the non-aqueous electrolyte secondary battery comprises at least one of a decrease in capacity and an increase in internal resistance of the non-aqueous electrolyte secondary battery.