1934 - 2000

66 YEARS OF EXELLENCE

Greetings For The Millennium

From All Of Us At

MEI-Charlton, Inc.

As we transit into the Third Millennium, taking some time for contemplation and reflection seems a worthy effort. Although the transition milestone of the Millennium itself is arbitrary and relates to just one segment of the human family, it nevertheless is a milestone. Of course, we've all heard the argument by some, that we've jumped the gun by a year and the Millennium doesn't really change until next New Year's Eve! Regardless of the factual merits of the argument, most folks have chosen to go along with the year 2000 celebration, so why rock the boat? The event provides an excellent opportunity to celebrate across time zones and national boundaries! In these times of an accelerating move toward globalization of commerce and information, crumbling trade barriers, and rapid interchange of ideas and peoples, survival strategies for any institution can be summarized by three words: Flexibility, Adaptation, and Contribution.

If you think about it, these strategies were probably just as valid in previous millennia. For instance, ancient beliefs about the age of the universe ranged from an extremely long time frame of 26E12 years (Rig Veda) to as low as 1E4 years (Biblical). The Big Bang theory, supported by the presence of a constant cosmic background radiation, postulates an expanding universe created about 13.6E9 years ago from a singular event. The formation of our own solar system is presently believed to have occurred around 4.6E9 years ago. And these may not be the final answers, as there are philosophical/metaphysical discussions about the existence of multiple universes in the cosmos.Remember, the introduction of the Hubble telescope has increased the number of galaxies known to mankind by several orders of magnitude; 120 billion and counting! Old beliefs are replaced by new ones, which in turn are shattered as new investigative tools and theories arrive. Yes to Flexibility.

Measurement of time has been an ongoing passion for mankind from antiquity to the present. Numerous calendars, some dating back more than five millennia (Egyptian, Vedic Indian), span the continents and several cultures, and they reflect changing concepts about the relative motions of the sun, moon, and earth. The origin of our present day calendar dates back to 1582 AD, when Pope Gregory reformed earlier versions to a Gregorian year consisting of 365 days, 5 hours, 49 minutes, and 12 seconds. World-wide adoption of the Gregorian calendar took more than 350 years, with the most recent convert being China in 1949. Earth time based on planetary motions was replaced by atomic time based on the vibrations of the cesium atom (9.192E9 cycles/sec) as the world's official Scientific Time Standard in 1972. We continue to Adapt.

While the emergence of humans as the dominant species is thought to have started 40 millennia ago, human settlement, agriculture, civic order, languages, literature, and arts initiated as recently as 8 to 10 millennia ago. In the First Millennium, while the West languished in the dark ages, the East flourished in a flurry of arts, literature, religions, theories of governance, and technologies. The beginnings of the Second Millennium saw a resurgence of the West with the Renaissance, Reformation, empire building, and settlement of new continents. Contributions to various aspects of life by humanity in the past two centuries has been phenomenal. From an agricultural economy, to the industrial revolution, to the more recent information/telecommunication advances, to (as we transit into the next Millennium) the internet revolution. What a trip of Contributions.

So what is waiting for us in the Third Millennium? A hundred years ago, a commissioner in the United States Patent Office reportedly advised there was no use in maintaining a patent office because everything that could possibly be invented had already been invented. Hmmm! I would rather go with the folksy expression, "You ain't seen nothin' yet!" Predicting far into the next Millennium would be futile; even predicting into the new century is problematic at best, if the now wildly inaccurate predictions from the ‘50's and ‘60's about life in the year 2000 are any indication. So perhaps, rather than predict what will be, we should simply observe what the trends suggest may be:

• Globalization of information, markets, manpower, and resources.
• Abundance of environmentally friendly energy sources (e.g., solar, wind, fusion).
• Eradication of hunger through efficient production of genetically modified crops/livestock.
• Increased lifespan made possible by revolutions in healthcare and genetic engineering.
• Improved, "intelligent" materials engineered for specific applications.
• High-speed (levitated) trains, intelligent cars/roads, and supersonic air travel.
• Robots ranging in size from nano-scale to macro-scale to handle tasks ranging from mundane to sophisticated.
• Embedded computers for personal technology for information, entertainment, identification, medical monitoring, etc.

Sounds like Utopia? Probably! We may be proud of our achievements to date, but we'll probably look like primitives to our great great grandchildren. The progress may be slowed and/or challenged by ethicists, environmentalists, fundamentalists, and anarchists. But the market forces will be the deciding factors. One thing is certain, progress will never be stopped or reversed.

Enough for reflections. MEI-C has been fortunate to be in the company of businesses who have the bragging rights to have spanned a decade, a century, and a millennium. Yes! We will continue to be Flexible, Adapt, and Contribute to meet the constantly changing needs of our clients in the new Millennium. Greetings!

D. G. Chakrapani, President MEI-Charlton, Inc.

High-Tech Happenings

Lately, the high-tech community has been asking us about solder joint problems. Several recent failures we have investigated involved a combination of corrosion,with associated dendrite formation, and poor wetting, with associated oxide formation. These problems depend on rather obscure surface phenomena that, unfortunately, can't be seen with the naked eye or even with a microscope, at least, not until it's too late!

Of course, wetting is important in many areas besides high tech. Pulp and paper companies, for example, routinely use wetting agents to keep paper ingredients together, and conversely, they sometimes purposely add ingredients to prevent wetting. You've probably noticed how yucky a milk carton opening gets if you tear the carton when opening it? Well, the carton stock is treated to repel water (or, milk as the case may be), but only on the surface; if you expose the underlying material by tearing it, you get a soggy carton. Another familiar product with tailored wetting properties is Gortex, which keeps liquid water out while still "breathing" (letting water vapor pass though).

Getting back to high-tech industry, proper flux is the key to wetting in soldering. The flux acts both as a wetting agent and as a chemical cleaning agent, dissolving and reacting with dirt and oxides, leaving bright clean wettable solder and metal surfaces. Only now, in the interest of minimizing environmental problems and speeding up operations, the industry is switching to no-clean flux, with the intent that post soldering cleaning of the flux residue is no longer necessary. At the same time, as junctions become smaller and smaller, and as industry switches to solder paste (microspheres of solder suspended in flux), the surface-to-volume ratio keeps increasing, giving the flux more surface to clean. But we are finding what's intended and what actually works are sometimes two different matters.

So what types of problems are we seeing? Primarily, circuit board corrosion and dendrite formation. After soldering, the flux residue contains salts and tends to absorb water, making it sticky, causing it to pick up contaminants from the air. The salts and contaminants can be corrosive, and they are also often conductive to some degree. Since with no-clean flux the residues cover the entire board, the potential for corrosion and short circuiting is high.

The photograph above, taken at a magnification of 750 in a Scanning Electron Microscope, shows a solder dendrite just starting to form on a solder joint. It formed because the flux residue was slightly conductive, allowing a corrosion electrolysis cell to develop between two adjacent leads. Over time, the dendrites grew in size until they reached the neighboring lead, which then shorted out the circuit, as shown in the photograph below.

Energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy can be used to pinpoint specific causes of dendrite formation.

Other problems we have encountered are gray or white colors or a dull appearance on solder, which are indications of thick surface oxide layers; these result in wetting problems where the solder fails to join properly. If the layers of oxide are thin enough, however, they show no visual or microscopic indications of their presence, making them very difficult to detect in advance; when the time comes to add solder, the surfaces refuse to wet properly, resulting in failed devices.

Because of the deliterious effect of oxide layers on soldering, the electronics industry is very interested in analytical methods capable of detecting them. Using EDS, oxide layers around 5,000 Angstroms (0.5 microns) thick can be detected by observing the X-ray oxygen peak. However, for layers this thick, optical microscopy and visual cues are nearly as effective.

Auger spectroscopy can be used for thinner, invisible layers. It detects layers 10 Angstroms thick and can be used in combination with sputter etching to determine actual oxide layer thickness. Auger spectroscopy, though, uses very expensive equipment and many hours of expert time are needed for a single thickness determination.

Sometimes the wetting problems depend more on the type than on the amount of oxide. For example, tin dioxide, which is more difficult to remove than the normal tin oxide, is sometimes found. X-ray photoelectron spectroscopy gives very accurate information on the types of oxides present, but it's just as expensive as auger spectroscopy.

Sometimes no oxide at all is found on poorly wetting surfaces. In one case, a "skin" effect was found by Auger spectroscopy, whereby a thin layer of lead was present on the surface. The lead stayed solid during soldering, producing poor wetting conditions.

We have also encountered cases where zinc impurities in the solder caused poor wetting. More complications!

For many years, the electronics industry has been looking for new analytical methods of assessing oxide layer thickness. The good news is some new methods are now available. The bad news, though, is the methods are complicated.

The new methods are based on electrochemical oxidation and reduction and are being used to analyze thin oxide layers. With these new methods, oxide types and thicknesses on solder or other metal surfaces can be measured. The inventors call the methods SERA and PESO.

These methods are so new we couldn't even find any commercial information about them on internet search engines. If you want to learn more about them, try the full text of US Patent Nos. 5,466,349 and 5,425,859, available on the internet at www.uspto.gov. In fact, if you want to know about anything ever invented (and patented) try the free searchable full-text patent database at www.uspto.gov.

MEI-C People

Chris Gerdes, Engineering Technician, and Dana King are happy to announce their recent engagement. They plan to wed in May of 2001.