Super labels show material advantage

18 December 2007

Advanced materials technologies have dramatically transformed the humble label, says Tom Shelley

Materials for labels are now available that boast more than a charmed life - surviving soldering temperatures of up to 320ºC, liquid nitrogen at -196ºC, as well as aggressive chemicals. They can also be made to hold fast to rough surfaces, such as on automotive castings, as well as indicate whether products to which they are attached have been tampered with or have become wet. They are thus not only much cheaper both to create and apply than traditional engraved aluminium name plates, but are also mechanically superior, as well as providing additional intelligence and information.

The latest product from Brady is a RoHS compliant label, the B-476 ‘Green’, specifically designed for PCB assembly and re-work, which carries a barcode and RoHS certification information. It is made of polyimide, uses pressure-sensitive acrylic adhesives and can survive temperatures of up to 320ºC for one and a half minutes. Normally, lead-free soldering takes place at 260ºC for 90 seconds. They also have a high opacity gloss topcoat specifically designed for thermal transfer printing, verified and certified to be lead free.

Brady’s specialist account manager William Nelson describes the thermal transfer printing ink as a layer of resin that bonds itself to the top layer of polymer. “The labels resist jet fuel, as well as a host of other solvents,” he says. And they can be printed and applied by automated equipment that moves faster than human hands.

The labels compatible with liquid nitrogen are basically vinyl cloth with acrylic adhesive, although clear polyester labels, designated B-461, can also go down to -196ºC and would survive at least three cycles of four hours, adds Brady. Products include ‘Freezerbondz’, a laboratory label designed to adhere to already frozen samples. Labels for rough surfaces use rubber-based adhesives, are quite thick, so that the label can press them into the rough surface.

Brady product expert Liz Gallagher states that the company has customers in the offshore, automotive, mobile phone and defence markets, including the Atomic Weapons Establishment. She makes particular mention of labels for mobile phones and electronic equipment. These cannot be removed in one piece and replaced, thus showing evidence of any tampering, and can also be made to turn red, if they have been exposed to water. For static sensitive items, she adds, the company also makes static dissipative labels that use charcoal-loaded adhesives to ensure any charge falls to 1% of its initial values in, typically 0.02s, more than fulfilling the requirements of US Electronics Industries Association, EIA-541 Packaging Materials Standards for ESD Sensitive Items, in which a charged material must decay to 1% of its initial voltage in less than two seconds. Label type B-129 has surface resistance values in the static dissipative range between 106 - 1012 ohms/sq.

Pointers

Text: Labels for electronics boards can survive excursions of up to 320ºC

Text: Other labels are designed to survive usage at –196ºC, including types that will bond to already frozen vials

Text: Label adhesives are available that bond to rough surfaces - and that survive prolonged exposure to jet fuel and other aggressive liquids