One-part adhesive forms flexible, conductive bond

Polytec PU 1000 is an electrically conductive polyurethane which addresses applications in die attach, bonding of components in hybrid circuit applications and SMT - areas where silver filled electrically conductive adhesives have been used for many decades. Usually such adhesives are epoxy-based, two-component or premixed and frozen single-component systems, but the Polytec PU 1000 polyurethane option provides a flexible bond, offering cost saving and performance advantages in the production process when compared to a standard two-part conductive epoxy adhesive. PU 1000 provides simplicity with its one-part application without mixing, indefinite pot life and rapid cure at room temperature, for example, 10 minutes at +23°C, compared to 15 minutes at +120°C for a typical two- part epoxy.

Compared to soldering, traditional epoxy-based Isotropic Conductive Adhesives (ICAs) offer lower processing temperatures, low volume resistivity, good temperature stability (withstanding reflow processes), excellent mechanical properties and chemical resistance. These advantages have made silver filled epoxies a reliable standard material for electrical interconnections in the electronics industry.

However, one significant disadvantage of epoxies is the high demand and overhead they place on the production process. The automated application of two-part adhesives requires suitable metering and mixing equipment; single-component, premixed and frozen adhesives require a sophisticated supply chain and storage to ensure an enduring temperature of at least -40°C. Another disadvantage of both these systems is the limited processing time (pot life) after mixing or thawing of the adhesive. After application, to obtain optimum electrical and mechanical properties, traditional epoxies should be cured at elevated temperatures (typically at +120 to +150°C).

Seeking to provide a superior solution with both performance and process efficiency advantages, Intertronics and manufacturers Polytec PT have introduced the PU 1000 formulation, an electrically conductive, polyurethane-based adhesive which can be considered as a very interesting alternative to epoxy-based adhesives in various applications.

Polytec PU 1000 is a single-component, silver filled, paste adhesive, which can be both stored and cured quickly at room temperature. It is flexible and elastic, which makes it suitable for bonding of flex-circuits, temperature-sensitive substrates or substrates with highly dissimilar coefficients of thermal expansion. It has found applications in smart cards and RFID circuitry, where cure can be effected in seconds, and may find interesting applications in wearables.

Intertronics says that the performance of PU 1000 is considered excellent for the electrical contact of both active and passive components, especially when coupled with its ease of processing and high flexibility. The adhesive can be dispensed automatically or applied manually and has rheological properties which are particularly suitable for the requirements of the jet type dispensers. It is suitable for electrically conductive bonding and coating applications on absorbing substrates like fabric, paper, leather, cork and non-absorbing substrates like glass, ceramics, PMMA, metals and most plastics.