May/June, 2012
Are Your Materials Really Halogen-Free?
Continued from page 59
with the oxide to clean and encour- age wetting. Likewise, the test requirements for halide-free and halogen-free materials are complete- ly different. While international standards have been set for halide- free, high-reliability solder intercon- nects and the test procedures have been well-established, the same can- not be said for halogen-free. As indicated in the chart, these
standards — particularly the three main standards that relate to halo- gen-free — do not mean 0 ppm halo-
“halide-free” might be so at room temperature but, once changed dur- ing the manufacturing process, can contain halogens far outside of the current recommended ppm limits. Removing the halogen from a
material isn’t difficult; the challenge lies in how it is replaced. Covalently bonded halogen delivers tremendous benefits for the soldering process including printer open time, thermal stability, the reflow process window and the shelf-life. Because of these advantages, many in the industry use small amounts of halogen that fall just below the current- ly defined ppm limits. Though valid from a formu- lation point of view, the danger is that excess halo- genated materials can be added during the manufac- turing process. The only way to
Halogen-free solder pastes, like this one
from Henkel, are becoming more prevalent in electronics assembly operations.
gen. So, the majority of today’s so- called “halogen-free” materials are, if they are just below the limit as set by these standards, really “halogen- light”. The other huge hurdle in rela- tion to halogen-free materials is the testing regimen. Halogens have a neutral charge and cannot be detect- ed by standard ion chromatography;
ensure a truly halogen-free product is to have zero deliberately added halo- gens in the formulation and products constructed of the purest raw materials available. Even the lack of delib-
erate additions of halogen
can result in halogen-containing products, as many of the raw materi- als can contain impurities. It is criti- cal, therefore, to partner with a sup- plier that has access to raw materi- als containing the least amount of impurities and with materials scien- tists who have the expertise to design a solder system that maintains all of the per- formance characteristics consistent with today’s sol- der materials but without the halogen. This is a diffi- cult task, indeed, and it’s safe to say that only a very few suppliers have these resources and are also not deliberately adding halo- gens to their materials.
Risk Always Present It is imperative to go to
Henkel’s MULTICORE HF200 Halogen- Free Solder Paste has zero deliberately added halogens, putting it significantly below the current PPM standard and ensuring integrity during the reflow process.
they must be converted into ionic halides through a combustion process. What this means is that many so-called halide-free materials may, in fact, contain hidden halides. The current analytical methods mean that testing occurs during a
Covalently bonded halogen delivers
tremendous benefits for the soldering process including printer open time and thermal stability.
state in which chemical bonds are not broken, but are kept under isola- tion in a neutral charge format. When these chemicals are heated up — as during the solder reflow process — the bonds are broken and the halides can then be detected. So, many products that claim to be
these lengths, however, because of the risk of halo- genated materials being added during the manufac- turing process. The situa- tion is complicated even fur- ther because of the testing
challenges halogen-free in troduces, with manufacturers largely relying on their suppliers to confirm the purity of the materials they are receiving. Now it is more than ever crucial to partner with a supplier that has the resources, expertise and formulation know-how to develop truly halogen-free products. Though there are still many unan- swered questions about halogen-free manufacturing, understanding these important halide-free and halogen- free distinctions, as well as the current halogen-free requirements, will help ensure a truly halogen-free production process. Armed with these facts, should government mandates become a reality, those in the know will be far better prepared to comply. Contact: Henkel Corp., 14000
Jamboree Rd., Irvine, CA 92606 % 714-368-8000 949-789-2500 fax: 714-368-2265 E-mail:
doug.dixon@us.henkel.com Web:
www.henkel.com/electronics r
www.us-tech.com
Page 61
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