Electrically conductive flexible polyurethane adhesive

Polytec PU 1000 is an electrically conductive polyurethane which addresses applications in die attach, bonding of components in hybrid circuit applications and surface mount technology (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 now the Polytec PU 1000 polyurethane option provides a flexible bond and cost-saving and performance advantages in the production process when compared with a standard two-part conductive epoxy adhesive. There is the simplicity of one-part application without mixing and an indefinite pot life with rapid cure at room temperature, e.g. 10 minutes at 23degC compared with 15 minutes at 120degC for a typical two-part epoxy.

Compared with 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 -40degC. Another disadvantage of both these systems is the limited processing time (pot life) after mixing or thawing of the adhesive. After application, to obtain their optimum electrical and mechanical properties, traditional epoxies should be cured at elevated temperatures (typically at 120-150degC).

Seeking to provide a superior approach 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 at room temperature 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. It may find interesting applications in wearable technology - clothing and accessories incorporating computer and advanced electronic technologies.

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.

For further information about Polytec PU 1000 single-part adhesive please see www.intertronics.co.uk/electrically_conductive_adhesives.