University of California

Hewlett-packard Company

Michael J Strum

Richard L Landingham

Oleg D Sherby

Lawrence M Wagner

Alfred Goldberg

A printed circuit board for minimizing thermally-induced mechanical damage of solder joints electrically connecting electronic components to the printed circuit board. The printed circuit board includes a first substrate, solder pads, and an expansion layer. The first substrate has two substantially parallel major surfaces, and a first coefficient of thermal expansion (CTE). The solder pads are located on one of the major surfaces of the substrate. The expansion layer has a second CTE, different than the first CTE, and is affixed to a portion of one of the major surfaces. The expansion layer is also arranged to provide a predetermined degree of bending for a given temperature change to a portion of the first substrate proximate to the expansion layer and to two of the solder pads, thus forming a concavity in the portion of the substrate.

Printed circuit board for mitigating thermally-induced mechanical damage

A free standing self contained device for bonding ultra thin metallic films, such as 0.001 inch beryllium foils. The device will regulate to a predetermined load for solid state bonding when heated to a bonding temperature. The device includes a load regulating feature, whereby the expansion stresses generated for bonding are regulated and self adjusting. The load regulator comprises a pair of friction isolators with a plurality of annealed copper members located therebetween. The device, with the load regulator, will adjust to and maintain a stress level needed to successfully and economically complete a leak tight bond without damaging thin foils or other delicate components.

Load regulating expansion fixture

Ultrahigh carbon steels with superplastic properties are produced by heating a steel containing ferrite and carbide phases to a soaking temperature approximately 50.degree. C. above the A.sub.1 transformation temperature, soaking the steel above the A.sub.1 temperature for a sufficient time that the major portion of the carbides dissolve into the austenite matrix, and then cooling the steel in a controlled manner within predetermined limits of cooling rate or transformation temperature, to obtain a steel having substantially spheroidal carbides. New alloy compositions contain aluminum and solute additions which promote the formation of a fine grain size and improve the resistance of the carbides to coarsening at the forming temperature.

Growing community of inventors

San Jose, CA, United States of America

Michael J Strum