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RoHS compliance and lead-free are not necessarily the same
Rob Spiegel -- Design News, November 8, 2006
According to a white paper written by Kevin Curran of the Electronics Group of Henkel Technologies, RoHS compliant products do not ensure lead-free process capability. Curran says, “Nothing could be further from the truth.” In response to the dual needs of RoHS compliance and lead-free process capability, Henkel has developed a RoHS-compliant adhesive that meets the traditional low-temp processing need while also being able to withstand the higher-temp lead-free processing capability.
Curran’s paper points out that RoHS compliance simply means that a product or a material does not contain any of the hazardous substances banned under the legislation. But just because the material is free of the RoHS-banned substances doesn’t mean it can withstand processing at the elevated temperatures of lead-free.
Curran points to numerous examples of compliance versus capability, but he focuses particularly on surface mount adhesives. He is concerned that lead-free manufacturing has pushed surface mount adhesives to their performance limits. “Lower temperature cure adhesives became the industry standard in surface mount assembly for a wide range of devices,” says Curran. But with the advent of lead-free processes, “it became clear that yet another adhesive innovation would be required to meet the demands of lead-free process conditions.”
In response to the dual needs of low-temperature cure adhesives and the elevated process temperatures of lead-free, Henkel developed an adhesive that meets both needs. Loctite 3629 was designed to deliver the capabilities of low-temperature cure adhesives while also retaining its strength during high-temperature lead-free soldering processes. “It possesses lower yield points to enable faster dispensing and printing ability and higher adhesive strength to handle the extreme temperatures of lead-free and the pull imposed on components resulting from the greater surface tension of lead-free alloys,” says Curran.
According to Curran, Loctite 3629 requires less energy for processing, has a long shelf-life and was designed to have an extended floor life which is beneficial in hot climates since the material maintains its stability even after removal from refrigeration. The adhesive is also RoHS compliant.
