~) Pergamon PII: S 1350-6307(97)00017-4 Engineerin9 Failure Ana(vsis, Vol. 5, No. 1, pp. 6%75, 1998 (t'), 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 1350~6307/98 $19.00 + 0.00 THE ATTACHMENT OF THIN ALUMINA CERAMIC PLATES TO KOVAR ® USING GOLD GERMANIUM SOLDER D. MATSUOKA, M. SMITH and O. S. ES-SAID* Mechanical Engineering Department, Loyola Marymount University, 7900 Loyola Blvd., Los Angeles, CA 90045-8145, U.S.A. (Received 23 June 1997) Abstract--An electronics firm experienced difficulty attaching gold metalized alumina ceramic plates to gold plated KovaF~ alloy assemblies using gold germanium eutectic solder. The soldering process often left large voids in the soldered joint. Using an automated oven and various gasses to reduce the formation of oxides, a reliable and repeatable process was found. Real time X-ray and cross section analysis of the joined parts determined that a high quality solder joint can be obtained by using spring probes to fixture the assemblies. © 1998 Elsevier Science Ltd. All rights reserved. Keywords: Defects, electronic-device failures, joint failures, non-destructive inspection, production failures. 1. BACKGROUND In various microwave communication applications, microwave signals follow paths created by depositing thin layers of metal, typically 250 A to 200/a in. thick, on alumina substrates. Gold is preferred on the outermost layers of such paths because of its high conductivity and oxidation resistance. Since gold will not adhere directly to alumina, the alumina is plated first with ti-tungsten, followed by either chrome, platinum or nickel, and finally with gold. This layer of gold creates a solder adhesion layer which can be consumed by the molten solder at and above the eutectic temperature. If this layer is consumed, the solder will also readily adhere to the next layer of unoxidized metal. A typical substrate is illustrated in Fig. 1 (a). (a) I 0.1250 --0.2500 TOP I I ! I BOTTOM i I (b) ] 0.3500 0.2500 O O Fig. 1. (a) Typical alumina substrate. (b) Typical gold plated Kovar carrier. I 6.- 0.0250 i t 1 0.0350 * Author to whom correspondence should be addressed. 69