Littelfuse, Inc.

Littlefuse, Inc.

Littlelfuse, Inc.

Tom J Hall

Michael J Weber

Philip C Shaw, Jr

Michael J Hoss

Donna L Randle

Feng Cai

The present invention provides a method for heat treating a polymer PTC composition to increase the peak resistivity of the composition making it especially well suited for high voltage applications. A polymer PTC composition having a melting point temperature T is provided. The temperature of the polymer PTC composition is increased at a rate, r , to a temperature greater than T . The temperature of polymer PTC composition is held at the temperature greater than T for a predetermined period of time. Then the temperature of the polymer PTC composition is decreased to a temperature less than T at a rate, r , wherein r is greater than r .

Method for heat treating PTC devices

Positive temperature coefficient (&ldquo;PTC&rdquo;) materials for use in electronic components for the protection of electrical circuits. Through the use of an organo-metallic coupling agent, the room temperature resistivity of polymeric PTC materials may be reduced. The PTC materials of the present invention include a polyolefin, a conductive filler and an organo-metallic coupling agent, and have an electrical resistivity at 25&deg; C. of less than 1 ohm cm.

Low resistivity polymeric PTC compositions

Circuit protection devices comprising PTC elements and circuits containing such devices. The PTC element includes a crystalline conductive polymer composition comprising a conductive particulate filler grafted to a modified polyolefin. The modified polyolefin comprises a polyolefin having a carboxylic acid or a carboxylic acid derivative grafted thereto. The conductive particulate filler is grafted via an esterification reaction to the modified polyolefin.

Polymeric PTC compositions

Electrical devices having a PTC element of a polymer having conductive particles dispersed therein. The PTC element is coated with a conductive layer and has electrodes with a plurality of voids affixed to opposing surfaces. The devices are made by dispersing conductive particles into a polymer to form a polymer PTC composition. The polymer PTC composition is melt-shaped to form a laminar shaped PTC element. First and second opposing surfaces of the PTC element are coated with a conductive layer. The electrodes, characterized by a plurality of voids and made of foam, are brought into contact with the coated surfaces of the PTC element, and heated while applying pressure to form a laminate. The laminate is then further shaped into a plurality of PTC electrical circuit protection devices.

PTC circuit protection device and manufacturing process for same

Electrical devices comprising a PTC element comprised of a polymer having conductive particles dispersed therein. The PTC element is coated with a conductive layer and has electrodes with a plurality of voids affixed to opposing surfaces. The devices are made by dispersing conductive particles into a polymer to form a polymer PTC composition. The polymer PTC composition is melt-shaped to form a laminar shaped PTC element. First and second opposing surfaces of the PTC element are coated with a conductive layer. The electrodes, characterized by a plurality of voids, are brought into contact with the coated surfaces of the PTC element, and heated while applying pressure to form a laminate. The laminate is then further shaped into a plurality of PTC electrical circuit protection devices.

Method of manufacturing a PTC circuit protection device

Electrical devices having improved PTC polymeric compositions

Electrical circuits with improved overcurrent protection

A method for producing a conductive polymeric composition exhibiting PTC behavior. The method includes the steps of: providing a quantity of polymer component having a melting point temperature T.sub.mp, and a quantity of conductive filler component; mixing the quantity of polymer component and the quantity of conductive filler component in a receiving unit at a temperature greater than T.sub.mp to form a molten mixture; forcing the molten mixture from the receiving unit to form an element having an electrical resistivity; measuring the electrical resistivity of the element; comparing the measured electrical resistivity of the element to a predetermined electrical resistivity value; and, adjusting the quantity of conductive filler component relative to the quantity of polymer component based on the comparison between the measured electrical resistivity of the element and the predetermined electrical resistivity value to achieve a desired element having an electrical resistivity approximately equal to the predetermined electrical resistivity value.

Growing community of inventors

Arlington Heights, IL, United States of America

Tom J Hall