Stay in touch…

Blog

Read the latest Bitstream

RSS Feed

LinkedIn

Look for us at LinkedIn

Twitter

Follow us on Twitter

Mix Magazine

This installment of The Bitstream column appeared in the May 2005 issue of Mix Magazine.

The Bitstream

This column combines Part Nine of Pedants In A Big Box with a discussion of legislation aimed at reducing hazardous substances, RoHS…

Getting The Lead Out

This month, I’m finally closing the book on my Pedant in a Box series and, all I can say is, man, did this project balloon! What started out as a seemingly modest glossary of non–audio techie terms, has grown into a list of over 10k words embodying a crazy amount of research time.

Before we dive into the Ws, I’m going to bring to your attention a development in EU policy making that will have subtle but important implications for our industry. It begins with the dichotomy between one facet of Euro and US public opinion, ends with those magick boxes that free many of us from being formal “engineers,” and all comes down to heavy metal.

No, I’m not talking about the heavy metal genre of big hair and tight pants, I’m referring to the plumbic alloys used as solder in most electronic assemblies. You see, the EU, unlike us Yanks, is concerned about long term public health and has phased in a “restriction of the use of certain hazardous substances in electrical and electronic equipment,” as the “RoHS” (Restriction of Hazardous Substances) document is subtitled. The Directive 2002/95/EC of the European Parliament and of the Council explicitly states that, “Member States shall ensure that, from 1 July 2006, new electrical and electronic equipment put on the market does not contain lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) or polybrominated diphenyl ethers (PBDE).” Though this and another directive, WEEE or Waste Electronics and Electrical Equipment, come out of the EU, the Japanese are also pushing ahead with “green” manufacturing initiatives and any US company conducting global business in the electronics, fastener (hexavalent chromium or Cr IV provides great corrosion resistance), jewelry or a host of other industries had better pay attention to stay competitive or be shut out from lucrative European and Far Eastern markets.

Fine and dandy but, why should we care? After all, if our government isn’t concerned with such trifling, why should we be? Well, two things really, size and reliability and let’s start with the latter. We have come to expect quite good reliability from professional grade electronics and I expect some interesting exceptions to that rule to surface in the next few years. The reason is that lead I mentioned earlier, or the lack thereof. You see, electronic parts are attached to their circuit boards with an alloy of about 40 to 60% lead and other metals, often silver or tin. If you change the composition and remove the offending lead from electrical solder, you raise the melting point to within a dozen degrees of the temperature at which those precious components you’re attaching are literally cooked to death. According to Canfield Technologies, a solder manufacturer, “typical reflow soldering temperatures for tin-lead alloys have a peak temperature of approximately 220° C. For lead free alloys, the peak temperatures for reflow soldering can be as high as 260° C.” This means that automated assembly processes must be fundamentally modified in order to achieve reliable solder flow and “wetting” (see sidebar) without exceeding temperature limits.

To make matters worse, many integrated circuits or ICs will require either repackaging or retirement. As product manager for Sonic Studio, we have had some serious hand wringing as a result of this directive and, I see prices going up and reliability going down for several years as sweeping obsolescence removes the majority of electronic components from the supply chain, to be replaced with higher temperature tolerant, heavy metal–reduced versions. At the same time, some parts will simply go away, never to be manufactured again.

This isn’t the first time that a big change has happened in the electronics industry due to enviro concerns. In the mid ’80s, the elimination of ozone–depleting CFCs (chlorofluorocarbon solvents) caused a major upheaval in an attempt to find a solution. That crisis lead to the rise of “no–clean” fluxes, which do not require removal after assembly, and water soluble fluxes that replaced the noxious chemical solvents of days past. In like fashion, the electronics industry has introduced new tin/silver/copper (95.5% tin/3.9% silver/0.6% copper) and new, compatible fluxes to ensure proper wetting and flow characteristics. The medical and food service industries have been using lead–free solders for over a decade, so there is a small but significant body of historical data available out there on the use of lead–free products.

Way back at the start of this rant, I mentioned size…By that, I meant a temporary increase in size for some products as mechanical designs change to accommodate the increased temperature profiles of lead–free soldering or, the size increases because one of more highly integrated parts are no longer available. However, savvy engineers should be able to minimize this effect.

Oh, yeah, there‘s another fun fact relating to this hardware headache, and it’s known as “tin whiskers.” I’ll leave it to the reader to Google the phrase and consider the implications of whiskers combined with the other reliability issues of the RoHS and WEEE directives, especially for the high density packaging so common with surface mounted ICs. Being Pb–free won’t be easy but, thanks to the European Union and the Japanese, our domestic disregard for environmental concerns that interfere with the smooth flow of money up the social ladder is being short circuited, in more ways than one.

Sidebar

Where’d I Put That Flux Capacitor…

What’s all this about wetting and flux? Flux is a blanket term used to describe various chemicals which remove contaminants during the soldering process. When plumbers fix a copper pipe, they use a highly reactive acid to chemically clean the pipe’s surface, like detergent cleans greasy dishes, so the solder will “wet” and flow across the joint. As you may know, that acid flux would be the death of an electronic device since the flux would “clean” it’s way right thought the circuitry. In the world of electronics, clean metal makes for mechanically solid and highly conductive connections while dirty pieces make for “cold solder joints” that are electrically and mechanically unreliable.

Pedants In A Big Box — Part Eight

Go to the glossary

Bio

OMas is Director of Brands & Products for Sonic Studio, LLC. Recent revelations, besides the RoHS, include the low maintenance Britpop of Dogs Die In Hot Cars on the V2 label.