Abstract: Described herein are methods for forming welded and soldered connections to flexible interconnect circuits and assemblies comprising such connections. An assembly can include a weldable transition unit having a transition pad and a solderable pad. The transition pad may comprise aluminum and can be welded to the aluminum conductive trace of a flexible interconnect circuit. The solderable pad can be soldered to the electrical contact of a device (e.g., a resistor, capacitor). In some examples, the weldable transition unit may comprise a stiffener mechanically connected to the transition pad to provide mechanical support of the transition pad and devices soldered to the transition pad. In some examples, the device soldered to the weldable transition unit may include one or more individual electronic components. In some examples, the device soldered to the weldable transition unit may be a printed circuit board (PCB) having solderable traces.

Abstract: Provided are flexible interconnect circuits comprising signal circuit elements. For example, a signal circuit element can be formed from the same metal sheet as a signal trace, thereby being monolithic with the signal circuit element. This integration of signal circuit elements into a flexible interconnect circuit reduces the number of additional operations and components (e.g., attaching external circuit elements). In some examples, a flexible interconnect circuit is used in a battery pack for interconnecting batteries while providing external terminals on the same side of the pack. Specifically, a flexible interconnect circuit comprises an interconnecting conductive layer (for connecting to batteries) and a return conductive layer, both extending between the first and second circuit edges. Each of these conductive layers comprises a corresponding external terminal at the first edge, while these layers are interconnected at the second edge.

Abstract: Provided are flexible interconnect circuits comprising signal circuit elements. For example, a signal circuit element can be formed from the same metal sheet as a signal trace, thereby being monolithic with the signal circuit element. This integration of signal circuit elements into a flexible interconnect circuit reduces the number of additional operations and components (e.g., attaching external circuit elements). In some examples, a flexible interconnect circuit is used in a battery pack for interconnecting batteries while providing external terminals on the same side of the pack. Specifically, a flexible interconnect circuit comprises an interconnecting conductive layer (for connecting to batteries) and a return conductive layer, both extending between the first and second circuit edges. Each of these conductive layers comprises a corresponding external terminal at the first edge, while these layers are interconnected at the second edge.