Surface mount multi-layer electrical circuit protection device with active element between PPTC layers

An electrical circuit for connection between an electrical energy source and an electrical load, the circuit being formed on a circuit substrate and having at least one surface-mounted electrical circuit protection device comprising:

• a first polymeric positive temperature coefficient resistive (“PPTC”) element having first and second major surfaces, a first electrode formed at the first major surface and in intimate electrical contact therewith, and a second electrode formed at the second major surface and in intimate electrical contact therewith;
• a second PPTC element having third and fourth major surfaces, a third electrode formed at the third major surface and in intimate electrical contact therewith, and a fourth electrode formed at the fourth major surface and in intimate electrical contact therewith;
• at least one heat-generating electrical component positioned between the first and second PPTC elements and in effective thermal contact with the second and third electrodes such that an electrical current above a threshold level passing through the component causes the component to heat, the heat being transferred to the PPTC elements and increasing the resistance of the first or second PPTC elements, and
• a plurality of terminal electrodes formed along at least one major edge of the device and connecting the first and second PPTC elements and the electrical component to the electrical substrate.

An electrical circuit for connection between an electrical energy source and an electrical load, the circuit being formed on a circuit substrate and having at least one surface-mounted electrical circuit protection device comprising:

• a generally box-shaped heat-generating element carrier comprising a central planar layer forming a polymeric positive temperature coefficient (“PPTC”) resistor having first and second major surfaces, a first electrode layer formed at the first major surface and in intimate electrical contact therewith, and a second electrode layer formed at the second major surface and in intimate electrical contact therewith, the element carrier defining a space for receiving at least one heat-generating electrical element;
• at least first, second and third terminal electrode regions formed along at least one major edge wall of the device and connected to the circuit substrate thereby surface mounting the device to the circuit substrate;
• the at least one heat-generating electrical element having a first metallized contact face bonded to a metal layer path within the element carrier space comprising a part of the first electrode layer, the heat-generating electrical element having a second metallized contact face bonded to one end region of an electrical interconnect structure, an opposite end region of the electrical interconnect structure being bonded to part of the third terminal electrode region, such that a current above a threshold level flowing through the heat-generating electrical element in an electrical circuit including the device generates heat that is transferred directly to the first PPTC resistor to aid tripping to a high resistance state.

A method for making a surface-mountable electrical circuit protection device comprising steps of:

• (a) forming a substantially planar polymeric positive temperature coefficient resistive (“PPTC”) layer having predetermined electrical characteristics and physical dimensions including first and second major surfaces, forming a first electrode layer at the first major surface in intimate electrical contact therewith, and forming a second electrode layer at the second major surface in intimate electrical contact therewith;
• (b) forming first, second and third terminal electrodes along at least one major edge wall of the device, the first terminal electrode being in electrical connection with the first electrode layer, the second terminal electrode being in electrical connection with the second electrode layer, and the third terminal electrode being electrically isolated from the first and second terminal electrodes;
• (c) bonding a first metallized face of at least one heat-generating electrical element to a part of the first electrode layer arranged to receive the heat-generating electrical element;
• and,
• (d) connecting a second metallized face of the at least one heat-generating electrical element to the third terminal electrode with an interconnect structure.

A method for making a surface-mountable electrical circuit protection device comprising steps of:

• (a) forming a substantially planar first polymeric positive temperature coefficient resistive (“PPTC”) element having predetermined electrical characteristics and physical dimensions including first and second major surfaces, forming a first electrode at the first major surface in intimate electrical contact therewith, and forming a second electrode at the second major surface in intimate electrical contact therewith;
• (b) forming a substantially planar second PPTC element having predetermined electrical characteristics and physical dimensions including third and fourth major surfaces, forming a third electrode at the third major surface in intimate electrical contact therewith, and forming a fourth electrode at the fourth major surface in intimate electrical contact therewith;
• (c) securing at least one heat-generating electrical component between the first and second PPTC elements to be in effective thermal contact with the second and third electrodes such that an electrical current above a threshold level passing through the component causes the component to heat, the heat thereupon being transferred to the first and second PPTC elements and tripping one of the PPTC elements to a high resistance state, and
• (d) forming a plurality of terminal electrodes along at least one major edge of the device in electrical connection with the first and second PPTC elements and the heat-generating electrical component, for enabling a surface-mounting connection of the first and second PPTC elements and the electrical component to an electrical substrate.