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areas are sites of small localized arcs, or perhaps these regions are small asperities at which contact between the components first occurs. Because of the relatively small cross section of these asperities, the current density passing through them is extremely high. The high current density may stimulate intermetallic compound for mation through local small-scale heat ing or material transport by electromigration. These observations of intermetallic compounds formation at the currentcarrying fractions make the choice of substitute materials difficult. Clearly, the aluminum wire should not be in contact with metals with which it can form intermetallic compounds. Unfor tunately, examination of the phase di agrams of aluminum reveals that many binary and ternary systems con tain extensive sequences of interme tallic compounds. More work is need ed on the details of the interactions of components at current-carrying inter faces. Acknowledgment
DYNATECH
PRECISION SAMPLING
CORPORATION
P.O. Box 15886, Baton Rouge, Louisiana 70895 CIRCLE 62 ON READER SERVICE CARD
I would like to express special thanks to Charles Brady, whose metallographic sections made this work possible, Sidney Greenwald for the de sign of the simple laboratory alumi num wire connection, and Joy Shoe maker for preparation of the manu script. References
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1064 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 9, AUGUST 1982
(1) Meese, W. J.; Beausoliel, R. W. "Ex ploratory Study of Glowing Electrical Connections"; Nat. Bur. Stand. (U.S.) Build. Sci. Ser. 103, October 1977. (2) Rabinow, J. "Some Thoughts on Elec trical Connections"; Nat. Bur. Stand. U.S. NBSIR 78-1507, August 1978. (3) Rabinow, J. "Special Report on Alumi num Wire"; Report for U.S. Consumer Product Safety Commission, September 1974. (4) Newbury, D.; Greenwald, S. "Observa tions on the Mechanisms of High Resis tance Junction Formation in Aluminum Wire Connections," J. Res. Nat. Bur. Stand. U.S. 1980,85,429-40. (5) Goldstein, J. I.; Yakowitz, H.; Newbu ry, D. E.; Lifshin, E.; Colby, J. W.; Cole man, J. R. "Practical Scanning Electron Microscopy"; Plenum: New York, 1975. (6) Myklebust, R. L.; Fiori, C. E.; Heinrich, K. F. J. "FRAME C: A Compact Procedure for Quantitative Energy-Dis persive Electron Probe X-ray Analysis"; Nat. Bur. Stand. U.S. Tech. Note 1106, September 1979. (7) Small, J. Α.; Newbury, D. E.; Mykle bust, R. L. "Analysis of Particles and Rough Samples by FRAME P, a ZAF Method Incorporating Peak-to-Background Measurements." In "Microbeam Analysis—1979"; Newbury, D. E., Ed.; San Francisco Press, 1979; pp 243-46. (8) Myklebust, R. L.; Newbury, D. E. "The Use and Abuse of a Quantitative Analy sis Procedure for Energy-Dispersive X-ray Microanalysis." In "Microbeam Analysis—1979"; Newbury, D. E., Ed.; San Francisco Press, 1979; pp 231-37. (9) Hansen, M. "Constitution of Binary Alloys"; McGraw-Hill: New York, 1958; pp 84-95.
