12/02/2009, Irvine, California

 

How “Free” is Your Halogen-Free Solder Paste?

With all the talk of halogen-free in the electronics industry these days, it’s hard to believe that there is actually no official halogen-free legislation – yet. While environmental activist groups such as Greenpeace initially pushed the effort to eliminate brominated flame retardants (BFRs), many electronics manufacturers have also jumped feet first into the halogen-free initiative. The fact is that while some BFRs -- namely polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) -- are harmful, not all BFRs represent health or safety risks.

Deca-BDE and/or deca-brominated diphenyl ether/tetra- bromobisphenol-A (TBBPA) are the BFRs most commonly used in electronics production and have been found to impose no risk. Scientific fact aside, halogen-free electronics production is arguably here to stay and, therefore, manufacturers must be informed about the best way forward when making critical material selections.

The term “halogen-free” is actually a bit misleading according to current recommendations of various industry consortia. By these definitions, materials which contain up to 900 ppm bromine, 900 ppm chlorine or maximum combined total halogens of 1500 ppm are still considered “halogen-free”. Perhaps a more fitting moniker would be “halogen-light”! It is understandable that some materials manufacturers are still deliberately adding halogen to their formulations. Considering that covalently bonded halogen offers significant benefit – particularly with soldering materials, as it extends open time on the printer, enhances thermal stability, extends the reflow process window and the shelf-life – one could relate to the continued, though much reduced, use of halogen in soldering products. The danger of this approach, however, is that there is always the risk of excessive halogenated material being added during manufacturing and, thus, pushing past the currently set limits.

Ultimately, the challenge for materials scientists is to find suitable halogen substitutes that deliver all of the benefits associated with halogenated materials in a halogen-free (not halogen-light!) product. Doing so is difficult, to say the least but, in Henkel’s view, this is the absolute correct philosophy. With a strong foundation as a company that places tremendous emphasis on sustainability in all aspects of its business, Henkel has consciously decided to push past the current standards, developing a solder paste material that contains absolutely no deliberately added halogens.    After an extensive and lengthy development program, Henkel made a formulating breakthrough which ultimately delivered Multicore HF108, a lead-free, halogen-free solder paste which has zero deliberately added halogen yet confers all of the benefits of modern, robust lead-free materials.

The lack of intentionally added halogen to Multicore HF108 has resulted in it being under the limit of detection in the rigorous oxygen bomb/ion chromatography test. Whileremoving the halogen from a material is not difficult, replacing it with activators that deliver the bevy of solder paste advantages to which manufacturers have become accustomed is a formidable challenge. Henkel’s materials experts, however, have been able to do just that.

Aside from its status as the market’s first truly zero-halogen solder paste, Multicore HF108 has numerous other advantages. With performance that is comparable to that of other well-known Henkel lead-free solder pastes, Multicore HF108 enables excellent high-speed print capability, provides a wide process window for exceptional manufacturing flexibility and has a long and stable shelf-life of up to six months when refrigerated or four weeks at room temperature.

Formulated for low voiding in fine-pitch CSPs and BGAs and outstanding solderability over a wide range of reflow profiles in air and nitrogen, Multicore HF108 has proven capability on a variety of surface finishes including Immersion silver and OSP copper. In addition, the material’s process flexibility also extends to provide outstanding performance regardless of environmental variations: the humidity resistance of Multicore HF108 is superb and has exhibited excellent coalescence even after eight hours of exposure to 80% relative humidity (RH). Other attributes include its colorless residues, which serve to improve the speed and ease of post-print inspection, as well as the material’s hot slump resistance, which limits the risk of bridging.

The fact is that designing a halogen-free material is challenging in and of itself. But, formulating a product such as Multicore HF108 that offers such a deep and broad range of performance and processabiltiy benefits with the added advantage of zero deliberately added halogen is a true breakthrough. It is imperative to understand that all halogen- free materials are not created equal and do not conform to consistent standards. Make sure that your halogen-free solder paste has no intentionally added halogens for true zero-halogen – as opposed to halogen-light – manufacturing and eliminate the risk from your operation.

For more information on Henkel’s Multicore HF108 or any of our advanced soldering products, call the company headquarters at 949-789-2500 or log onto www.henkel.com/electronics.